Skip to main content
Journal of Gastrointestinal Oncology logoLink to Journal of Gastrointestinal Oncology
. 2016 Dec;7(6):882–902. doi: 10.21037/jgo.2016.11.02

Molecular spectrum of KRAS, NRAS, BRAF, PIK3CA, TP53, and APC somatic gene mutations in Arab patients with colorectal cancer: determination of frequency and distribution pattern

Humaid O Al-Shamsi 1,2,3, Jeremy Jones 4, Yazan Fahmawi 1, Ibrahim Dahbour 1, Aziz Tabash 1, Reham Abdel-Wahab 1,5, Ahmed O S Abousamra 1, Kenna R Shaw 3, Lianchun Xiao 1, Manal M Hassan 1, Benjamin R Kipp 6, Scott Kopetz 1, Amr S Soliman 7, Robert R McWilliams 4, Robert A Wolff 1
PMCID: PMC5177568  PMID: 28078112

Abstract

Background

The frequency rates of mutations such as KRAS, NRAS, BRAF, and PIK3CA in colorectal cancer (CRC) differ among populations. The aim of this study was to assess mutation frequencies in the Arab population and determine their correlations with certain clinicopathological features.

Methods

Arab patients from the Arab Gulf region and a population of age- and sex-matched Western patients with CRC whose tumors were evaluated with next-generation sequencing (NGS) were identified and retrospectively reviewed. The mutation rates of KRAS, NRAS, BRAF, PIK3CA, TP53, and APC were recorded, along with clinicopathological features. Other somatic mutation and their rates were also identified. Fisher’s exact test was used to determine the association between mutation status and clinical features.

Results

A total of 198 cases were identified; 99 Arab patients and 99 Western patients. Fifty-two point seven percent of Arab patients had stage IV disease at initial presentation, 74.2% had left-sided tumors. Eighty-nine point two percent had tubular adenocarcinoma and 10.8% had mucinous adenocarcinoma. The prevalence rates of KRAS, NRAS, BRAF, PIK3CA, TP53, APC, SMAD, FBXW7 mutations in Arab population were 44.4%, 4%, 4%, 13.1%, 52.5%, 27.3%, 2% and 3% respectively. Compared to 48.4%, 4%, 4%, 12.1%, 47.5%, 24.2%, 11.1% and 0% respectively in matched Western population. Associations between these mutations and patient clinicopathological features were not statistically significant.

Conclusions

This is the first study to report comprehensive hotspot mutations using NGS in Arab patients with CRC. The frequency of KRAS, NRAS, BRAF, TP53, APC and PIK3CA mutations were similar to reported frequencies in Western population except SMAD4 that had a lower frequency and higher frequency of FBXW7 mutation.

Keywords: Somatic mutations, colorectal cancer (CRC), next-generation sequencing (NGS), Arab population

Introduction

Colorectal cancer (CRC) is the third most commonly diagnosed cancer in males and the second most common in females, worldwide (1). CRC incidence has been increasing in Arab countries such as Kuwait and Saudi Arabia (2,3). In Saudi Arabia, the incidence of CRC accounted for 10.4% of all cancers in 2010; it was the most common cancer in males and the third most common in females, after breast and thyroid cancers (4). In the Kuwaiti population, CRC was the most common cancer in males (11.3%) and the second most common in females (9.1%) in 2000–2009 (5). Gene mutation and defective cell regulation are important processes in the development of CRC (6). Accumulation of these mutations, including mutations in KRAS, NRAS, BRAF and PIK3CA, activate multiple signaling pathways, such as RAS-RAF-MAPK and PI3K-PTEN-AKT, that play a major role in regulating cell proliferation, angiogenesis, cell motility and apoptosis (7-9).

Assessment of genetic mutations is an essential element in the modern era of personalized cancer treatment. In the past years, our understanding of some of these mutations and their predictive and prognostic potential has revolutionized the treatment for various malignancies, with improved outcome and patient care [e.g., targeting wild-type RAS in metastatic colon cancer (10), targeting HER2 in gastric adenocarcinoma] (11).

Anti-EGFR medications such as cetuximab and panitumumab are used for treatment of wild-type RAS metastatic CRC, but patients with mutations in the extended RAS family are resistant to these medications. Similarly, the patients with BRAF and the PIK3CA mutation have shown negative response to treatment with EGFR inhibitors (12-18).

The frequency rates of these mutations in CRC differ between populations. Zhang et al. have reported differences in the genetic profiles of KRAS, NRAS, PIK3CA, and BRAF at mutation hotspots between CRC patients from China and those from Western countries. The rate of these mutations in Arab patients with CRC is not well defined (9). The evaluations of the rates of these mutations in Arab population with CRC have been limited to few mutations including KRAS and BRAF (19,20).

The standard definition of the Arab world comprises the 22 countries and territories of the Arab League. The Arab Gulf countries which are also part of the Arab League are: Saudi Arabia, United Arab Emirates, Kuwait, Qatar, Bahrain and Oman.

The rate of some mutations of CRC in the Arab population from the Arabian Peninsula has been reported previously. A study by Siraj et al. reported a BRAF mutation rate of 2.5% in a Saudi Arabian population (19).

The rate of KRAS in Arab population from outside the Arab Gulf population has been reported, Elbjeirami et al. reported a KRAS mutation rate of 44% in a Jordanian population (20). The ratio of patients with mutated versus wild-type KRAS in the Jordanian study was similar to that reported in Western countries. Studies from Egypt showed high proportion (35%) of young onset CRC in patients under age 40. The studies also showed distinct KRAS and microsatellite instability (MSI) profiles between young and old CRC patients in Egypt (21,22). DNA methylation was also different in tumors of CRC patients from Egypt, Jordan, and Turkey (23).

The largest study, which included 500 patients from Saudi Arabia, assessed KRAS and BRAF using polymerase chain reaction (PCR) and DNA sequencing; the reported frequency rates were 30.1% and 2.4%, respectively (24). However, no studies have utilized next-generation sequencing (NGS) to assess in-depth mutations in Arab patients with CRC.

In the present study, we aimed to evaluate hotspot mutations by NGS in an Arab population from the Gulf countries with CRC and explored correlations of the mutations with clinicopathological features in this under-studied population.

Methods

Objectives

The primary objective of the study was to determine the frequencies of KRAS, NRAS, BRAF, PIK3CA, TP53, and APC mutations, as well as other somatic mutations, in CRC tumors from 99 Arab patients from the Gulf countries and to compare the results with 99 Western matched patients from our database at MD Anderson Cancer Center and with the frequencies among other populations. The secondary objective was to determine the relationships between these mutations and clinicopathological features of these patients.

Study design

We conducted a retrospective case-case study of Arab-patients from the Gulf countries who were treated in the U.S. at MD Anderson Cancer Center and the Mayo Clinic in Rochester, Minnesota. The electronic databases at both institutions were searched for all patients with a diagnosis of CRC from 2010 to 2014 who had standardized hotspot mutation testing using a 46- or 50-gene multiplex platform by NGS. The electronic records then were searched manually with various criteria to identify patients from the Arabian Peninsula using country of origin, primary language (Arabic), and sponsoring country that covering the medical expenses for the patient and matched Western patients that were treated at MD Anderson Cancer Center. We identified 99 Arab patients with CRC and there were matched (age, sex and type of testing 46- or 50-gene, see below for testing details) with 99 Western patients who had the same testing during the same period. The study was approved by institutional ethics board of MD Anderson Cancer Center (NCT01772771) and Mayo Clinic (15-000563).

Clinicopathological information was abstracted from the medical records for the following variables: age (≤50 or >50 years), sex (male or female), tumor site (right colon, left colon, or rectum), histological type, differentiation, MSI, and TNM stage.

We also conducted a comprehensive literature search for all studies that reported mutation rates in CRC tumors in populations around the world (Middle Eastern, Western, and Asian population). The method of detecting these mutations and the result for each population were recorded. The results were then pooled by region and compared with those from other regions and from our current study population.

Mutations assessments

All the samples (60% primary tumor and 40% other metastatic lesions) were originally evaluated using hematoxylin and eosin staining for tumor cellularity. DNA was extracted, purified, and quantified after hematoxylin and eosin staining. Genomic analysis samples were evaluated using NGS using the Ion AmpliSeq Cancer Panel (Life Technologies, Grand Island, NY, USA) test to assess hotspot mutations in 46 genes (38 patients). Testing later expanded to 50 genes by adding EZH2, IDH2, GNA11, and GNAQ (61 patients). Table S1 lists all tested genes.

Statistical analysis

Fisher’s exact test was used to determine the association between mutation status and clinical factors, as well as the association between markers.

The analysis determined the association between mutation status of each marker (i.e., KRAS, NRAS, BRAF, PIK3CA, TP53, APC) with clinicopathological features, especially histopathological type, tumor differentiation, tumor site, patients’ age, and sex and the association between markers. For all statistical analysis, we used IBM SPSS version 21.0 (IBM Corp., Armonk, NY, USA), and the P value was considered to be significant if it was less than 0.05.

Results

Study population

A total of 198 cases were identified; 99 Arab patients and 99 age- and sex-matched Western patients. Of the 99 Arab patients, 74 (74.7%) patients were from MD Anderson and 25 (25.3%) were from the Mayo Clinic. All of Western patients were treated at MD Anderson Cancer Center. The majority of Arab patients were from Saudi Arabia (38.3%) and the United Arab Emirates (34.3%). The major ethnicity of Western patients were White (79%) followed by Black Afro-American (11%) and Hispanic (10%).

Clinicopathological features

The demographic characteristics and clinicopathological variables for the Arab and Western population are given in Table 1. The mean age of Arab and Western patients was 50.8 and 48.03 years respectively. Of the 99 Arab patients identified, 52.7% had stage IV disease at their initial presentation. Seventy-four point two percent had left-sided tumors including rectum, sigmoid colon and splenic flexure compared to 25.8% had right sided tumors including cecum, hepatic flexure, and transverse colon. Furthermore, the histology of tubular adenocarcinoma (89.2%) was higher than mucinous adenocarcinoma (10.8%). In addition, the percentage of patients with moderately differentiated histology and poorly differentiated histology were 71% and 23.7%, respectively. The clinicopathological variables of the Western population are given in Table 1.

Table 1. Demographic characteristics and clinicopathological variables of 99 Arab patients with colorectal cancer a matched 99 Western patients.

Characteristic Arab patients (N=99) (%) Western patients (N=99) (%)
Sex (%)
   Male 60 (60.6) 61 (61.6)
   Female 39 (39.4) 38 (38.4)
Testing type (%)
   46 genes 38 (38.4) 38 (38.4)
   50 genes 61 (61.6) 61 (61.6)
Age at diagnosis (mean ± SD) [range]
   All 50.80±13.62 [20–77] 48.03±12.50 [20–79]
   Male 52.70±14.60 50.10±13.30
   Female 47.80±11.50 44.60±10.30
Age* (years) (%)
   ≤50 47 (47.5) 47 (47.5)
   >50 52 (52.5) 52 (52.5)
The distribution of patients from the six Arab Gulf countries (%)
   Saudi Arabia 39
   United Arab Emirates 34
   Kuwait 11
   Qatar 7
   Bahrain 2
   Oman 2
   Not available 5
Race among Western patients (%)
   White 79 (79.8)
   Black African American 11 (11.1)
   Hispanic 9 (9.1)
Primary tumor site (side of body)** (%)
   Left sided 69 (69.7) 64 (64.6)
   Right sided 24 (24.2) 35 (35.4)
   Unknown (missing data) 6 (6.1)
Primary tumor site (specific location)** (%)
   Ascending colon 9 (9.1) 7 (7.1)
   Cecum 7 (7.1) 18 (18.2)
   Hepatic flexure 1 (1.0) 4 (4.0)
   Splenic flexure 1 (1.0) 2 (2.0)
   Transverse colon 5 (5.0) 4 (4.0)
   Descending colon 6 (6.0) 15 (15.2)
   Sigmoid colon 27 (27.3) 18 (18.2)
   Rectum 37 (37.4) 31 (31.3)
   Unknown (missing data) 6 (6.1)
Histological type** (%)
   Tubular adenocarcinoma 83 (83.8) 93 (94.0)
   Mucinous adenocarcinoma 10 (10.1) 6 (6.0)
   Unknown (missing data) 6 (6.1)
Tumor differentiation** (%)
   Well 5 (5.1) 2 (2.1)
   Moderate 66 (66.6) 79 (84.1)
   Poor 22 (22.2) 13 (13.8)
   Unknown (missing data) 6 (6.1)
TNM stage** (%)
   I 0 3 (3.1)
   II 3 (3.0) 6 (6.1)
   III 41 (41.4) 15 (15.3)
   IV 49 (49.5) 74 (75.5)
   Unknown (missing data) 6 (6.1)
KRAS mutation (%)
   Positive 44 (44.4) 48 (48.4)
   Negative 55 (55.6) 51 (51.6)
NRAS mutation (%)
   Positive 4 (4.0) 4 (4.0)
   Negative 95 (96.0) 95 (96.0)
BRAF mutation (%)
   Positive 4 (4.0) 4 (4.0)
   Negative 95 (96.0) 95 (96.0)
TP53 mutation (%)
   Positive 52 (52.5) 47 (47.5)
   Negative 47 (47.5) 52 (52.5)
APC mutation (%)
   Positive 27 (27.3) 24 (24.2)
   Negative 72 (72.7) 75 (75.8)

*, for 1 patient (1%), age of diagnosis was not available; **, for 6 patients (6.1%), data were not available for the primary tumor site, histological type, tumor differentiation, and TNM stage.

Distribution of KRAS, NRAS, TP53, BRAF, PIK3CA, and APC in the 99 Arab patients with CRC

The rate of mutations in the 99 Arab patients and 99 Western matched patients with CRC using 46-gene (38 patients) and 50-gene (61 patients) panels in each cohort are given in Table 2.

Table 2. The rate of mutations in 99 Arab patients and matched 99 Western cohort with CRC using 46 genes (38 patients) and 50 genes (61 patients) in each cohort.

CRC somatic mutation No. of Arab patients with the mutation (%) No. of Western matched patients with the mutation (%)
KRAS 44 (44.4) 48 (48.4)
NRAS 4 (4.0) 4 (4.0)
BRAF 4 (4.0) 4 (4.0)
PIK3CA 13 (13.1) 12 (12.1)
TP53 52 (52.5) 47 (47.5)
APC 27 (27.3) 24 (24.2)
FBXW7 3 (3.0) 0
SMAD4 2 (2.0) 11 (11.1)
GNAS 2 (2.0) 1 (1.0)
AKT1 2 (2.0) 2 (2.0)
PDGFRA 2 (2.0) 1 (1.0)
ATM 3 (3.0) 1 (1.0)
KIT1 2 (2.0) 3 (3.3)

CRC, colorectal cancer.

Of the 4% of Arab patients with NRAS mutation, none had KRAS mutation, in keeping with previous reports that these mutations are mutually exclusive (25). BRAF mutation was found in four Arab patients and was mutually exclusive of KRAS or NRAS mutations. Eight tumors of Arab patients had both KRAS and PIK3CA mutations. PIK3CA mutations were present in 8 (8.1%) Arab patients with KRAS mutations, compared with only 5 Arab patients (5%) with wild-type KRAS. This finding suggests that PIK3CA and KRAS gene mutations represent overlapping subgroups in CRC.

Correlation of gene mutations with clinicopathological findings

A summary of the relationships among the gene mutations and clinicopathological features in Arab CRC patients is provided in Tables 3,4.

Table 3. Correlation between KRAS, NRAS, and BRAF mutation status and clinicopathological features in Arab CRC patients.

Clinicopathological features KRAS status NRAS status BRAF status
Wild type (%) Mutant type (%) P Wild type (%) Mutant type (%) P Wild type (%) Mutant type (%) P
Age (years) 0.8 0.3 1
   >50 28 (53.8) 24 (46.2) 51 (98.1) 1 (1.9) 50 (96.2) 2 (3.8)
   ≤50 26 (56.5) 20 (43.5) 43 (93.5) 3 (6.5) 44 (95.7) 2 (4.3)
Sex 0.5 1 0.6
   Female 20 (51.3) 19 (48.7) 38 (97.4) 1 (2.6) 37 (94.9) 2 (5.1)
   Male 35 (58.3) 25 (41.7) 57 (95.0) 3 (5.0) 58 (96.7) 2 (3.3)
Family history 0.7038 0.3 1
   No 46 (53.5) 40 (46.5) 83 (96.5) 3 (3.5) 83 (96.5) 3 (3.5)
   Yes 3 (42.9) 4 (57.1) 6 (85.7) 1 (14.3) 7 (100.0)
Personal history of FAP 1 1 1
   No 48 (52.2) 44 (47.8) 88 (95.7) 4 (4.3) 89 (96.7) 3 (3.3)
   Yes 1 (100.0) 1 (100.0) 1 (100.0)
Primary tumor site 1 0.5693 1
   Left sided 36 (52.2) 33 (47.8) 65 (94.2) 4 (5.8) 67 (97.1) 2 (2.9)
   Right sided 13 (54.2) 11 (45.8) 24 (100.0) 23 (95.8) 1 (4.2)
Tumor differentiation 0.5 0.2 0.2
   Well 4 (80.0) 1 (20.0) 4 (80.0) 1 (20.0) 4 (80.0) 1 (20.0)
   Moderate 33 (50.0) 33 (50.0) 64 (97.0) 2 (3.0) 64 (97.0) 2 (3.0)
   Poor 12 (54.5) 10 (45.5) 21 (95.5) 1 (4.5) 22 (100.0)
MSI 0.09 1 0.6
   High 1 (100.0) 1 (100.0) 1 (100.0)
   Intact 4 (100.0) 4 (100.0) 4 (100.0)
   Stable 10 (43.5) 13 (56.5) 22 (95.7) 1 (4.3) 23 (100.0)
   Unknown 20 (40.0) 30 (60.0) 47 (94.0) 3 (6.0) 47 (94.0)
Histological type 0.3 1 1
   Tubular adenocarcinoma 42 (50.6) 41 (49.4) 79 (95.2) 4 (4.8) 80 (96.4) 3 (3.6)
   Mucinous adenocarcinoma 7 (70.0) 3 (30.0) 10 (100.0) 10 (100.0)
TNM stage at diagnosis 0.1 0.2 0.6
   I 1 (100.0) 1 (100.0) 1 (100.0)
   II 1 (50.0) 1 (50.0) 2 (100.0) 2 (100.0)
   III 26 (63.4) 15 (36.6) 41 (100.0) 39 (95.1)
   IV 21 (42.9) 28 (57.1) 45 (91.8) 4 (8.2) 48 (98.0)
Clinical status 0.2 0.07 0.2
   Alive 20 (55.6) 16 (44.4) 36 (100.0) 36 (100.0)
   Dead 16 (42.1) 22 (57.9) 34 (89.5) 4 (10.5) 35 (92.1) 3 (7.9)
   Unknown 13 (68.4) 6 (31.6) 19 (100.0) 19 (100.0)

FAP, familial adenomatous polyposis; MSI, microsatellite instability; CRC, colorectal cancer.

Table 4. Correlation between PIK3CA, TP53, and APC mutation status and clinicopathological features in Arab CRC patients.

Clinicopathological features PIK3CA status TP53 status APC status
Wild type (%) Mutant type (%) P Wild type (%) Mutant type (%) P Wild type (%) Mutant type (%) P
Age (years) 0.08 0.009 0.5
   >50 42 (80.8) 10 (19.2) 31 (59.6) 21 (40.4) 36 (69.2) 16 (30.8)
   <50 43 (93.5) 3 (6.5) 15 (32.6) 31 (67.4) 35 (76.1) 11 (23.9)
Sex 1 0.07 1
   Female 34 (87.2) 5 (12.8) 14 (35.9) 25 (64.1) 28 (71.8) 11 (28.2)
   Male 52 (86.7) 8 (13.3) 33 (55.0) 27 (45.0) 44 (73.3) 16 (26.7)
Family history 1 0.3 1
   No 74 (86.0) 12 (14.0) 40 (46.5) 46 (53.5) 65 (75.6) 21 (24.4)
   Yes 6 (85.7) 1 (14.3) 5 (71.4) 2 (28.6) 5 (71.4) 2 (28.6)
Personal history of FAP 1 1 0.2
   No 79 (85.9) 13 (14.1) 45 (48.9) 47 (51.1) 70 (76.1) 22 (23.9)
   Yes 1 (100.0) 1 (100.0) 1 (100.0)
Tumor site 1 0.3 0.2
   Left 80 (86.0) 13 (14.0) 31 (44.9) 38 (55.1) 49 (71.0) 20 (29.0)
   Right 21 (87.5) 3 (12.5) 14 (58.3) 10 (41.7) 21 (87.5) 3 (12.5)
Differentiation 1 0.5 0.6
   Well 5 (100.0) 1 (20.0) 4 (80.0) 5 (100.0)
   Moderate 56 (84.8) 10 (15.2) 33 (50.0) 33 (50.0) 49 (74.2) 17 (25.8)
   Poor 19 (86.4) 3 (13.6) 11 (50.0) 11 (50.0) 16 (72.7) 6 (27.3)
MSI 0.2 0.6 0.9
   High 1 (100.0) 1 (100.0) 1 (100.0)
   Intact 2 (50.0) 2 (50.0) 1 (25.0) 3 (75.0) 3 (75.0) 1 (25.0)
   Stable 21 (91.3) 2 (8.7) 11 (47.8) 12 (52.2) 19 (82.6) 4 (17.4)
   Unknown 41 (82.0) 9 (18.0) 27 (54.0) 23 (46.0) 38 (76.0) 12 (24.0)
Tumor histology 1 1 0.4416
   Tubular adenocarcinoma 71 (85.5) 12 (14.5) 40 (48.2) 43 (51.8) 61 (73.5) 22 (26.5)
   Mucinous adenocarcinoma 9 (90.0) 1 (10.0) 5 (50.0) 5 (50.0) 9 (90.0) 1 (10.0)
TNM stage at diagnosis 0.23 0.2 0.04
   I 1 (100.0) 1 (100.0) 1 (100.0)
   II 1 (50.0) 1 (50.0) 1 (50.0) 1 (50.0) 1 (50.0) 1 (50.0)
   III 34 (82.9) 7 (17.1) 24 (58.5) 17 (41.5) 35 (85.4) 6 (14.6)
   IV 44 (89.8) 5 (10.2) 20 (40.8) 29 (59.2) 34 (69.4) 15 (30.6)
Clinical status 0.2 0.1 0.6
   Alive 28 (77.8) 8 (22.2) 13 (36.1) 23 (63.9) 26 (72.2) 10 (27.8)
   Dead 34 (89.5) 4 (10.5) 23 (60.5) 15 (39.5) 28 (73.7) 10 (26.3)
   Unknown 18 (94.7) 1 (5.3) 9 (47.4) 10 (52.6) 16 (84.2) 3 (15.8)

FAP, familial adenomatous polyposis; MSI, microsatellite instability; CRC, colorectal cancer.

The associations between KRAS, NRAS, BRAF, PIK3CA, TP53 and APC mutations and Arab population clinicopathological features such as age, gender, family history, personal history of familial adenomatous polyposis (FAP), tumor site, tumor histology, differentiation, and stage were not statistically significant. An exception was a statistically significant association of TP53 mutation with age >50 years (P=0.009). PIK3CA and TP53 were statistically significantly associated with absence of an APC gene mutation (P=0.039 and P=0.04), respectively.

Discussion

Here we present a large retrospective, two-center study that evaluated the frequencies of KRAS, NRAS, BRAF, TP53, APC, and PIK3CA somatic mutations in a cohort of 99 Arab CRC patients. This is the first study that comprehensively evaluated hotspot somatic mutations in Arab patients with CRC.

The majority of the population from the current study was from Saudi Arabia and the United Arab Emirates, however, all the gulf countries share common tribal genetic origin of the population from the Arabian peninsula (26).

Our study utilized comprehensive NGS platform to analyze the mutational profile of Arab CRC patients and assess the frequency. The frequencies of KRAS, NRAS, BRAF, TP53, and APC mutations. We were able to demonstrate similar mutational frequencies to those in most target genes compared with the Western population with the exception; however, PIK3CA which occurred at a lower frequency in the Arab population patients than in Western patients.

We performed a comprehensive literature review for somatic mutations testing in patients with CRC. The total number of cases were 2,981 in Middle Eastern countries (16 studies), 22,441 cases in Western countries (43 studies), and 8,053 in Asian countries (27 studies). Rate of mutations in each study, method of testing, pooled mutation rates based on geographical distribution and total pooled mutation rates from all reported studies to date are summarized in Table 5.

Table 5. Worldwide distribution pattern of KRAS, NRAS, BRAF, PIK3CA, APC, and TP53 mutations.

Region Year Method and codons studied Number of patients tested Number of patients with mutations in the indicated gene (%) References
KRAS NRAS BRAF PIK3CA APC TP53
Middle Eastern countries 2,981 691/2,052 (33.70) 4/99 (4.0) 76/1,647 (4.60) 51/418 (12.00) 59/177 (33.0) 208/541 (38.40)
   Arabian Peninsula 2015 Next-generation sequencing 99 44 (44.00) 4 (4.0) 4 (4.00) 13 (13.00) 27 (27.3) 52 (52.00) Current study
   Egypt 2001 PCR and SequiTherm EXCEL IITM DNA sequencing; codons: 12, 13, immunohistochemistry for TP53, exons: 5–9 59 5/47 (11.00) Not done Not done Not done Not done 26/56 (46.00) (22)
   Saudi Arabia 2008 PCR amplification and direct sequencing, exons: 9, 20, exons: 5–8 448 Not done Not done Not done 51/418 (12.00) Not done 130/386 (33.70) (27)
   Tunisia 2008 PCR, codons: 1240–1513 48 Not done Not done 4/48 (8.00) Not done 25/48 (52.0) Not done (28)
   Iran 2011 PCR-RFLP, codon: 600 110 24/86 (28.00) Not done 0 Not done Not done Not done (29)
   Jordan 2012 Hybridization-based strip assay, RT-PCR-based assay, Sanger sequencing, codons: 12, 13 100 44 (44.00) Not done Not done Not done Not done Not done (20)
   Iraq 2012 PCR and reverse hybridization 50 24 (48.00) Not done Not done Not done Not done Not done (30)
   Turkey 2013 AutoGenomics INFINITI® assay, codons: 12, 13, 61 53 26 (49.05) Not done 0 Not done Not done Not done (31)
   Saudi Arabia 2014 LCD-array kit 83 35/83 (42.20) Not done Not done Not done Not done Not done (32)
   Saudi Arabia 2014 Direct DNA sequencing, codons: 12, 13, codon: 600 770 216/755 (28.60) Not done 19/757 (2.50) Not done Not done Not done (19)
   Saudi Arabia 2014 PCR, codons: 12, 13 150 84/150 (56.00) Not done Not done Not done Not done Not done (33)
   Iran 2014 PCR-RFLP, codon: 600 80 Not done Not done 37/80 (46.25) Not done Not done Not done (34)
   Iran 2014 Direct DNA sequencing, codons: 653–885, 853–1242, 1213–1482, and 1404–1613 of exon 15 30 Not done Not done Not done Not done 7 (23.3) Not done (35)
   Saudi Arabia 2015 PCR, codons: 12, 13, codon: 600 770 150/498 (30.10) Not done 12/500 (2.40) Not done Not done Not done (24)
   Turkey 2015 Pyrosequencing with PCR, codons: 12, 13, 61 31 7/31 (22.00) Not done Not done Not done Not done Not done (36)
   Iran 2015 PCR and direct sequencing by Sanger method 100 32 (32.00) Not done Not done Not done Not done Not done (37)
Western countries 22,441 7,497/21,212 (35.30) 183/4,781 (3.8) 1,011/11,100 (9.10) 1,336/9,696 (13.80) 626/1,540 (40.6) 169/308 (54.90)
   Norway 2002 PCR, codons: 653–2843 218 Not done Not done Not done Not done 144 (66.0) Not done (38)
   United Kingdom 2002 Direct sequencing, codons: 12, 13, 61, denaturing HPLC “WAVE” analysis, codons: 1028–1712 106 29/106 (27.40) Not done Not done Not done 60/106 (56.0) 65/106 (61.30) (39)
   Portugal 2005 PCR-SSCP automated sequencing, exon: 9; PCR automated sequencing, exon: 20 150 31 (20.70) Not done 18 (12.00) 14 (9.30) Not done Not done (40)
   Netherlands 2005 Nested PCR, followed by direct sequencing, exon: 1, codons: 1286–1520 656 235/656 (35.80) Not done Not done Not done 245 (37.3) Not done (41)
   USA 2007 PCR, codons: 1286–1585 90 29 (32.20) Not done 18 (20.00) Not done 31 (34.4) 41 (45.60) (42)
   Germany 2007 PCR, codons: 1260–1547, exons: 5–8 (TP53) 99 Not done Not done Not done Not done 49 (49.0) 52 (52.00) (43)
   France 2008 PCR then direct sequencing, exon: 2, exons: 1, 2, 9, 20 (PIK3CA) 586 198 (33.80) Not done 78 (13.30) 98 (16.70) Not done Not done (44)
   Hungary 2008 PCR and SSCP/heteroduplex analysis, codons: 1285–1465 70 Not done Not done Not done Not done 15 (21.4) Not done (45)
   USA 2008 PCR, exon: 2, exons: 11, 15, DNA sequencing using a BigDye® 3.1 Terminator kit 62 24 (38.70) Not done 4 (5.60) 2 (3.20) Not done Not done (46)
   Italy 2008 HRM analysis, exon: 2, exon: 15, exons: 9, 20 116 50 (43.00) Not done 11 (9.50) 20 (17.20) Not done Not done (47)
   Italy 2009 PCR, codons: 12, 13, exons: 11, 15, exons: 9, 20 32 7/29 (24.10) Not done 3/31 (9.67) 4/31 (12.90) Not done Not done (48)
   USA 2009 PCR and pyrosequencing, codons: 12, 13, codon: 600, exons: 9, 20 450 160/448 (35.70) Not done 69/438 (15.80) 82 (18.20) Not done Not done (49)
   United Kingdom 2009 PCR, then Sequenom mass-spectrometric genotyping, (first sample), PCR, then Sanger sequencing (second sample), exon: 2, exon: 15, exons: 9, 20 168 62 (36.90) Not done 13 (7.70) 26 (15.47) Not done Not done (50)
   Belgium 2010 Mass spectrometry genotyping 1,022 299/747 (40.00) 17/644 (2.6) 36/761 (4.70) 108/743 (14.50) Not done Not done (13)
   Germany 2010 Two multiplex PCRs: the first for BRAF exon 15 and KRAS exons 2 and 3 and the second for PIK3CA exons 9 and 20 and NRAS exons 2 and 3 294 119/245 (48.60) 6/294 (2.0) 13/245 (5.30) 32/245 (13.10) Not done Not done (51)
   France 2010 KRAS: allelic discrimination assay; checked by direct sequencing of exon 2, BRAF(V600E): allelic discrimination assay; checked by direct sequencing; PIK3CA: direct sequencing, then DNA analyzer automated sequencer 42 19 (45.20) Not done 1 (2.38) 6 (14.28) Not done Not done (52)
   USA 2011 Pyrosequencing, codons: 12, 13, 61, codons: 595–600; PCR, then Sanger sequencing (PIK3CA), codons: 532–554 of exon 9, 1011–1062 of exon 20 504 69/367 (18.80) 2/31 (6.0) 31/361 (8.60) 54 (11.00) Not done Not done (53)
   Italy 2012 HRM analysis and direct sequencing, exon: 2, exon: 15, exon: 20 209 90 (43.00) Not done 13/117 (11.10) 7 (3.30) Not done Not done (54)
   Sardinia 2012 Automated DNA sequencing, exons: 2, 3, exon: 15, exons: 9, 20 478 145/478 (30.30) Not done 1/384 (0.26) 67/384 (17.44) Not done Not done (55)
   USA 2013 Pyrosequencing, codons: 12, 13, codon: 600, exons: 9, 20 964 336/959 (35.00) Not done 131/959 (13.70) 161/964 (16.70) Not done Not done (56)
   Portugal 2013 HRM, then DNA sequencing, exons: 3, 4 (KRAS), exons: 11, 15, exons: 9, 20 (PIK3CA) 201 26 (12.90) Not done 11 (5.50) 22 (10.90) Not done Not done (57)
   Russia 2013 HRM and sequencing COLD-PCR/sequencing, allele-specific PCR 195 70 (35.90) 8 (4.1) 8 (4.10) 24 (12.30) Not done Not done (58)
   Australia 2013 Direct sequencing, exons: 9, 20 757 215 (28.40) Not done 120 (15.90) 105 (14.00) Not done Not done (59)
   France 2013 PCR amplification followed by direct sequencing, exons: 2, 3, exon: 15, exons: 9, 20 98 23 (23.50) Not done 2 (2.00) 4 (4.00) Not done Not done (60)
   Germany 2013 Pyrosequencing, exon: 2, exon: 15, exons: 9, 20 171 70 (40.90) Not done 19 (11.10) 20 (18.70) Not done Not done (61)
   Albania 2014 Direct sequencing, codons: 12, 13, 61, 146, codon: 600 159 28 (17.60) Not done 10 (6.30) Not done Not done Not done (62)
   United Kingdom 2013 Pyrosequencing (KRAS), codons: 12, 13, Sequenom, Sanger sequencing, codons: 12, 13, codon: 600 1,976 836 (42.30) 71 (3.6) 178 (9.00) 251 (12.70) Not done Not done (18)
   Greece 2014 PCR, mutation analysis methodology of increased sensitivity and conventional genomic dideoxy sequencing (PIK3CA) 171 92 (53.80) Not done 4/171 (2.30) 6/171 (3.50) Not done Not done (63)
   Brazil 2014 Direct sequencing, codons: 12, 13 8,234 2,627 (31.90) Not done Not done Not done Not done Not done (64)
   Chile 2014 PCR, codons: 12, 13 262 98 (37.00) Not done Not done Not done Not done Not done (65)
   Italy 2015 Pyrosequencing, codons: 12, 13, 61, 146, codon: 600, exons: 9, 20 194 92 (47.40) 7/194 (3.6) 10 (19.40) 32 (16.50) Not done Not done (66)
   USA 2014 Not reported 484 240 (49.60) 32 (7.4) 10 (4.10) Not done Not done Not done (67)
   Greece 2015 PCR, codons: 12, 14, 61, 146, codon: 600, bidirectional sequence analysis 322 118 (36.60) Not done 17/188 (9.00) Not done Not done Not done (68)
   Italy 2015 Mass spectrometry-based single-base extension technique, codons (KRAS): 12, 13, 59, 61, 117, 146, codons (NRAS): 12, 13, 18, 59, 61, 117, 146, codons (BRAF): 594, 600, 601 175 25 (14.00) 4 (3.0) 13 (7.00) Not done Not done Not done (69)
   Brazil 2015 Pyrosequencing method improved by nested PCR, codons: 12, 13 422 139/421 (33.00) Not done Not done Not done Not done Not done (70)
   Belgium 2015 RT-PCR and Sequenom, exons: 2–4 193 53/165 (32.10) 4 (2.4) 26/165 (15.80) 22/165 (13.30) Not done Not done (71)
   USA 2015 PCR, codons: 12, 13 331 91 (27.50) Not done Not done Not done Not done Not done (72)
   Italy 2015 Pyrosequencing, exon: 2, codon: 600 309 143/307 (46.60) 17/307 (5.5) 12 (4.00) Not done Not done Not done (73)
   France 2015 Next-generation sequencing 13 7 (53.80) Not done Not done Not done 13/13 (100.0) 11/13 (84.60) (74)
   Germany 2015 PCR, codons: 12, 13, codon: 600 99 33 (33.30) Not done 9 (9.00) Not done Not done Not done (75)
   France 2015 PCR, codons: 12, 13, codon: 600 180 93 (51.70) Not done 19 (10.60) Not done Not done Not done (76)
   France 2015 Direct Sanger sequencing and PCR, codons: 12, 13, codon: 600, exons: 9, 20 826 301/817 (37.00) Not done 85/780 (11.00) 113 (14.00) Not done Not done (77)
   USA 2015 Next-generation sequencing 353 175/288 (49.60) 15/288 (4.3) 18/288 (5.10) 56/288 (13.90) 69/288 (24.0) Not done (78)
Asian countries 8,053 2,797/7,973 (35.10) 108/3,041 (3.6) 292/5,922 (4.90) 362/4,238 (8.50) 85/262 (32.4) 244/608 (40.10)
   Japan 2002 PCR-SSCP method, codons: 12, 14, codons: 582–1580, codons: 33–367 61 22/61 (36.00) Not done Not done Not done 29/61 (47.5) 35/61 (57.40) (79)
   South Korea 2008 WAVE DHPLC system, codon: 12, codons: 1202–1674, exons: 4–9 78 23 (29.50) Not done Not done Not done 26 (33.3) 27 (34.60) (80)
   China 2010 Multiplex PCR for TP53 and PTEN amplification; singleplex PCR using HotStarTaq (QIAGEN) to amplify PIK3CA, KRAS, and BRAF amplicons, codons: 12, 13, 61 (KRAS), codon: 600 (BRAF) 181 58 (32.00) Not done 29 (16.00) 7 (3.00) Not done 92 (52.00) (81)
   China 2010 Pyrosequencing using a PyroMark ID system (Biotage AB, Sweden), codons: 12, 13, codon: 600 61 12 (19.70) Not done 3 (4.90) 3 (4.90) Not done Not done (82)
   Korea 2011 Direct sequencing and peptide nucleic acid-mediated PCR 92 19 (20.70) Not done 3 (3.30) 1 (1.10) Not done Not done (83)
   Japan 2011 Direct sequencing 134 41 (30.60) Not done 1 (0.75) 18 (13.40) Not done Not done (84)
   Taiwan (China) 2012 Direct sequencing; HRM analysis, codon: 600, exons: 9, 20 (PIK3CA) 182 61 (33.50) Not done 2 (1.10) 13 (7.10) Not done Not done (85)
   China 2012 PCR-based direct DNA sequencing, codons: 12, 13 331 137/311 (44.10) Not done 9/156 (5.80) 4/156 (2.60) Not done Not done (86)
   China 2012 Automated sequencing analysis, codons: 12–14, codon: 600, codons: 542, 545, 1047 69 25/57 (53.90) Not done 15/59 (25.40) 5/56 (8.90) Not done Not done (87)
   Japan 2013 Multiplex kit (Luminex xMAP tests) and direct sequencing methods, codons: 61, 146, codon: 600, codons: 542, 545, 546, 1047 82 21 (25.60) 2 (2.4) 4 (4.90) 4 (4.90) Not done Not done (88)
   Malaysia 2013 Direct DNA sequencing, quantitative real-time PCR, codons: 12, 13, 61, codon: 600 44 11 (25.00) Not done 1 (2.30) 33/43 (76.70) Not done Not done (89)
   Japan 2013 Direct sequencing 254 85 (33.50) Not done 17 (6.70) Not done Not done Not done (90)
   Japan 2013 Automated CEQ 2000XL DNA analysis system 43 12 (27.90) Not done 2 (4.70) 2 (4.70) Not done Not done (91)
   Taiwan (China) 2013 Primer extension analysis, codons: 12, 13, HRM analysis, codon: 600, direct sequencing (for TP53), exons: 5–8 165 61/165 (36.97) Not done 7/165 (4.24) Not done Not done 62/165 (37.58) (92)
   India 2013 PCR, exon: 2 (KRAS) 1,323 271 (20.50) Not done Not done Not done Not done Not done (93)
   India 2013 PCR-RFLP and direct sequencing 62 41 (66.10) Not done Not done Not done Not done Not done (94)
   India 2013 PCR-restriction digestion to detect KRAS mutations, PCR-SSCP followed by DNA sequencing to detect mutations in APC and TP53 genes 30 8 (26.70) Not done Not done Not done 14 (46.7) 6 (20.00) (95)
   India 2014 Nested PCR, codons: 12, 13; PCR and direct sequencing, codon: 600; hemi-nested and nested PCR, exons: 9, 20 204 48 (23.50) Not done 20 (9.80) 12 (5.90) Not done Not done (96)
   Pakistan 2014 PCR, codons: full coding region of KRAS 150 20/150 (13.00) Not done Not done Not done Not done Not done (97)
   China 2014 Torrent AmpliSeq Cancer Panel 93 47 (50.50) 3 (3.2) 1 (1.10) 10 (10.80) 16 (17.2) 22 (23.70) (98)
   Japan 2015 Denaturing gradient gel electrophoresis; PCR (for BRAF) 813 312/812 (38.00) Not done 40/811 (5.00) Not done Not done Not done (99)
   China 2015 Sanger sequencing; mutation system PCR (nine patients), codons: 12, 13, codon: 600 535 185/488 (37.90) Not done 20/450 (4.40) Not done Not done Not done (100)
   Japan 2015 Luminex xMAP technology, codons: 61, 146, codon: 600, codons: 542, 545, 546, 1047; Scorpion assay, codons: 12, 13 264 100/264 (37.90) 11/264 (4.2) 14/264 (5.40) 17/264 (6.40) Not done Not done (101)
   Singapore 2015 Direct sequencing 45 15 (33.30) Not done 0 1 (2.20) Not done Not done (102)
   China 2015 RT-PCR and Sanger sequencing, codons: 12, 13, 61, 117, 146, codon: 600, codon: 1047 1,110 504/1,110 (45.40) 43/1,110 (3.9) 34/1,110 (3.10) 39/1,110 (3.50) Not done Not done (9)
   South Korea 2015 Not reported 100 26 (26.00) Not done Not done Not done Not done Not done (103)
   Japan 2015 PCR and direct sequencing, exon: 2 55 30 (54.40) Not done Not done Not done Not done Not done (104)
   Taiwan (China) 2015 PCR and Sequenom 1,492 602 (40.30) 49 (3.3) 70 (4.70) 193 (12.90) Not done Not done (105)
Pooled results for all studies from all regions 33,475 10,985/31,237 (35.20) 33,475 1,379/18,669 (7.40) 1,749/14,352 (12.20) 770/1,980 (38.9) 621/1,457 (42.60)

PCR, polymerase chain reaction; RT-PCR, reverse transcription polymerase chain reaction; RFLP, restriction fragment length polymorphism; HPLC, high-performance liquid chromatography; SSCP, single-strand conformation polymorphism; HRM, high-resolution melting; COLD, co-amplification at lower denaturation temperature; DHPLC, denaturing high-performance liquid chromatography.

Wild-type KRAS and NRAS oncogenes encode a family of small proteins with homology to G-proteins that regulate cellular signal transduction (106). The KRAS mutation frequency rate differs throughout the world. Soliman et al. reported that mutation of the KRAS gene was uncommon in Egyptian CRCs in general (11% of patients), in contrast to Western cases (28% in sporadic CRCs), and was only identified in patients older than 40 years (21). The study by Elbjeirami et al. reported KRAS mutation (44%) in a Jordanian population (20). The ratio of patients with mutated versus wild-type KRAS in our current study was similar to that reported in Western countries but differed from Egypt (107), which is a neighboring Middle Eastern country but similar to the Jordanian study (20). Other studies from Saudi Arabia reported rates of KRAS mutation to be 42.2% (108), 28.6% (19), 56% (33), and 30.1% (109). The results of our study are in line with all of the other Arab studies. The data from our study did not show statistical significance between KRAS gene mutation in the Arab population and any covariate such as age or gender, which is consistent with the results of a similar study in a Western population (110). Unlike KRAS mutation frequency rates, NRAS mutation was not previously reported in an Arab population. In Western populations the mutation frequency rates were low; in one study that used NGS, the rate was 5.1% (78). In the present study, NRAS mutation was detected in 4% of Arab patients, which is similar to the Western cohort and consistent with the pooled frequency rates in Asian countries and Western countries (3.6% and 3.8%, respectively).

The BRAF gene encodes a protein that is part of the Ras-Raf-MEK-ERK, or MAPK signaling pathway (111). Activation of this pathway results in cellular growth and proliferation. Siraj et al. reported the frequency of BRAF mutation as 2.5% in 770 Saudi patients. In our study, the BRAF frequency rate was 4% in Arab patients, which is lower than the Western cohort and the estimated frequency in Western countries (9.2%) but similar to the frequency reported in Asian (4.9%) and Middle Eastern countries (4.6%). This difference in BRAF mutational frequency may be attributable to the use of different methods/assays to assess for the mutations. Interestingly, the Western population-based studies reported that BRAF-mutant CRC was significantly more likely to occur in females (108); however, in our study there was no statistically significant association between the BRAF mutation and gender. In contrast to Zhang et al.’s study, which showed a significant association between BRAF mutation and right-sided colon cancer, we did not find any significant association between BRAF mutation and tumor site (9) yet the findings of our study is limited by the small number of patients with BRAF mutation (only four patients).

The PIK3CA gene encodes the catalytic subunit of PI3K, which is an intracellular central mediator of cell survival signals (112). Very few studies describe the frequency of PIK3CA mutations in an Arab population. Abubaker et al. reported a PIK3CA frequency rate of 12.2% in a Saudi population (27), which is consistent with the frequency found in our Arab patients population (13%) and the Western patients cohort (12.1%). However, the frequency rate of PIK3CA mutations in Asian countries (8.5%) appear to be lower compared with Middle Eastern and Western countries. This difference could be attributable to either environmental or genetic factors. Our study found no significant differences between Western and Arab populations with regard to PIK3CA gene mutations and other clinical characteristics (109).

The tumor suppressor gene APC plays an important role in CRC development. Absence of the APC protein leads to accumulation of beta-catenin in the cytoplasm, resulting in constitutive transcriptional activation of TCF-responsive genes, which may contribute to tumor progression (113). The frequency from the pooled results in Middle Eastern countries is (33%), which is consistent with the frequency rate in Asian countries (32.4%), but it is lower than the frequency rate in Western countries (44.8%). In the current study the frequency was (27.3%) in Arab patients and (24.2%) in Western patients. These differences between the frequencies in our population study and pooled frequencies in Middle Eastern countries, Asian countries and Western countries may be attributable to environmental factors.

Loss of TP53 function is one of the major events in the development of CRC. TP53 mutations are thought to occur late in pathogenesis of CRC (39). The TP53 mutation rate in our study was 52% in Arab patients and 47.5% in our Western cohort, which they are significantly higher than the pooled frequency rates encountered in Middle Eastern (38.4%) and Asian countries (40.1%). This difference between our study and the Middle Eastern countries frequency rate may be attributable to different sample selection. Abubaker et al. reported a trend of TP53 mutations towards old age (>50 years old) (27). In the present study, there was a significant association between TP53 mutations and age (>50 years old). This finding is in contrast to previous studies in Western countries (110,114).

Mutations in the FBXW7 gene are thought to impair cyclin E degradation resulting in unchecked cellular growth, and subsequently in progression of CRC (115-117). The frequency of FBXW7 mutation in the present study was 3% in Arab patients, none were found in the matched Western cohort. This is the first report of FBXW7 gene mutation in an Arab population and potential association.

Fleming et al. reported the frequency of SMAD4 mutation in 744 patients with sporadic CRC at 8.6% (118). Mutations in SMAD4 are thought to promote tumorigenesis by allowing CRC cells evade the inhibitory effect of TGF-beta, thus contributing to progression of CRC (119,120). In the present study, the rate of SMAD4 mutation in the Arab patients was 2% where 11.1% in the matched Western cohort. This difference in the frequency rates may be attributable to differences in sample size, ethnicities, and geographical distribution. This is the first report of SMAD4 gene mutation in the Arab population.

EGFR signaling plays a significant role in CRC development and progression. Gene mutations in the EGFR signaling proteins, such as KRAS, NRAS, BRAF, and TP53, are vital factors in evaluating EGFR targeted treatment resistance in patients with CRC (7,107). KRAS-mutant CRC do not respond to anti-EGFR agents such as cetuximab (14). However, only 40–60% of type patients with wild-type KRAS respond to EGFR targeted therapies (121). Therefore, it is very important to identify other molecular alterations that may affect anti-EGFR treatment. De Roock et al. demonstrated that BRAF, NRAS, and PIK3CA mutations affect the anti-EGFR treatment outcome in chemotherapy-resistant metastatic CRC patients (13).

Many environmental factors such as lifestyle and diet are implicated as risk factors for CRC. Subjects consuming a diet rich in meat and fat and poor in fiber have a higher risk for CRC (122-124). Decreased physical activity and obesity also put the subjects in a greater risk for CRC (125,126). Westernization of the developing countries along with changes in diet and lifestyle have been associated with the increasing incidence of CRC in developing countries (127,128). The increased incidence of CRC in Arabian Peninsula is parallel to similar increase incidence of CRC in Westernized countries. The results of the present study report the frequency of KRAS, NRAS, BRAF, TP53, and APC mutations similar to the frequencies in Western population. Many studies have previously indicated that the differences in the incidence of CRC are probably due to environmental and not genetic factors (129). In our study, we found that there was no association between incidence of CRC and clinicopathological factors except the association of TP53 mutation and advanced age. Two studies from Qatar and Jordan have shown associations between CRC and diet with low fiber, sedentary life and obesity in Qatari and Jordanian populations (130,131). A study by Bener et al. evaluated the association of family history, lifestyle and dietary factors with developing CRC in Arab patients. Multivariate stepwise logistic regression analysis showed that family history, BMI, smoking, consuming bakery and soft drinks were significant predictors of development of CRC. Age, gender, a sedentary lifestyle, and being overweight were positively linked with CRC risk (130). Also, there is a recent trend for left-sided CRC in Arabs, probably related to their changing lifestyles (132). All these results may influence CRC screening and diagnostic methodologies with cancer preventive lifestyle recommendations in Arab population.

A possible limitation of current study is the relatively small sample size which, which could potentially limit the generalizability of our findings. We have attempted to decrease this risk by including patients from at least six Arab Gulf countries, which were recruited from two large U.S. institutions.

Conclusions

This is the first study to report comprehensive hotspot somatic mutations using NGS in Arab patients with CRC. The frequency of KRAS, NRAS, BRAF, TP53, APC and PIK3CA mutations were similar to reported frequencies in Western population except SMAD4 that had a lower frequency but higher rate of FBXW7 mutation. Identification of molecular markers can provide insights into the pathogenic process and help optimize personalized cancer therapy in this poorly studied population.

Acknowledgements

The authors thank Sunita Patterson for providing medical editorial assistance with this article. The study was supported by the Sheikh Khalifa Bin Zayed Al Nahyan Institute for Personalized Cancer Therapy, Houston, Texas, USA and Khalifa Bin Zayed Al Nahyan Foundation, Abu Dhabi, United Arab Emirates. Names of the institutions at which the work was performed: MD Anderson Cancer Center; Mayo Clinic, Rochester.

Table S1. Codons tested on AmpliSeq 46-gene (CMS46) and 50-gene (CMS50) assays.

Gene Codons tested in CMS46 Codons tested in CMS50
ABL1 237–260, 275–283, 303–319, 350–362, 387–412 232–260, 275–279, 314–360, 380–412
AKT1 16–59 16–52, 154–183
ALK 1172–1177, 1259–1277 1172–1204, 1270–1279
APC 865–886, 1105–1122, 1289–1322, 1349–1382, 1430–1467, 1487–1509 860–891, 1089–1125, 1284–1326, 1342–1384, 1426–1471, 1483–1524, 1543–1582
ATM 343–355, 395–412, 601–614, 837–862, 1307–1324, 1674–1693, 1733–1758, 1785–1802, 1935–1957, 2436–2445, 2650–2667, 2693–2715, 2721–2739, 2888–2891, 2937–2950, 2996–3016, 3037–3052 326–355, 407–412, 601–626, 834–865, 1292–1325, 1674–1707, 1726–1757, 1790–1815, 1926–1946, 2436–2454, 2650–2667, 2682–2711, 2718–2736, 2865–2891, 2933–2950, 2996–3026, 3041–3057
BRAF 439–471, 581–605 439–473, 581–611
CDH1 69–92, 351–373, 395–415 65–96, 337–374, 380–408
CDKN2A 51–76 51–90, 98–140
CSF1R 299–318, 952–973 297–319, 953–973
CTNNB1 12–45 9–48
EGFR 89–125, 280–297, 575–601, 698–722, 729–761, 766–790, 803–823, 830–866 96–123, 279–297, 575–601, 695–726, 729–796, 807–823, 855–875
ERBB2 753–769, 772–797, 832–852, 875–883 752–797, 839–882
ERBB4 136–141, 177–186, 234–247, 272–289, 303–322, 343–363, 588–619, 923–943 136–141, 167–186, 225–247, 254–290, 295–323, 333–367, 580–623, 919–948
EZH2 625–649
FBXW7 264–279, 381–400, 450–472, 478–506, 566–583 264–287, 378–403, 434–473, 478–509, 567–594
FGFR1 121–139, 247–268 120–148, 247–273
FGFR2 250–268, 297–313, 367–395, 546–558 250–275, 296–313, 362–399, 546–558
FGFR3 247–268, 377–409, 634–653, 681–712, 790–807 247–277, 367–402, 631–653, 690–719, 771–807
FLT3 441–458, 569–575, 589–613, 662–682, 828–846 437–466, 570–610, 663–685, 828–847
GNA11 202–219
GNAQ 206–245
GNAS 196–218 196–240
HNF1A 198–217, 253–282 192–221, 253–282
HRAS 5–23, 48–79 5–35, 42–82
IDH1 118–134 101–135
IDH2 133–177
JAK2 604–622 603–622
JAK3 568–578, 709–729 128–140, 568–580, 709–733
KDR 240–258, 267–280, 472–490, 872–892, 959–985, 1138–1161, 1192–1216, 1301–1321, 1336–1356 244–291, 471–480, 872–894, 961–988, 1135–1156, 1192–1221, 1283–1310, 1324–1357
KIT 47–69, 501–514, 536–549, 550–585, 641–684, 714–728, 807–828, 836–854 23–58, 494–514, 525–587, 627–661, 664–684, 714–724, 802–828, 832–858
KRAS 5–28, 40–67, 136–150 5–66, 114–150
MET 160–187, 362–379, 992–1017, 1105–1126, 1247–1268 159–188, 339–378, 816–856, 981–1012, 1105–1132, 1246–1274
MLH1 373–393 373–415
MPL 499–522 501–522
NOTCH1 1566–1605, 1673–1697 1566–1602, 1673–1680, 2536–2476
NPM1 283–295 283–295
NRAS 6–22, 53–69 3–31, 43–69, 124–150
PDGFRA 552–570, 647–688, 819–847 552–583, 644–668, 671–709, 819–854
PIK3CA 77–98, 328–351, 418–422, 533–551, 688–716, 1019–1049, 1065–1069 54–90, 106–118, 316–351, 390–422, 449–468, 522–549, 677–720, 898–924, 1017–1051, 1065–1069
PTEN 5–24, 55–70, 167–184, 212–222, 240–266, 282–300, 316–342 1–25, 55–70, 99–135, 165–184, 212–215, 231–267, 282–300, 312–342
PTPN11 53–82, 486–506 46–82, 485–527
RB1 132–154, 195–203, 350–371, 549–565, 566–585, 655–680, 703–724, 743–765 130–159, 196–203, 314–345, 350–366, 452–463, 547–582, 655–691, 703–724, 743–770
RET 609–627, 630–654, 762–774, 880–901, 914–931 608–654, 762–786, 875–924
SMAD4 109–128, 167–184, 228–247, 304–319, 330–363, 385–404, 444–472, 497–526 98–136, 142–146, 165–202, 242–263, 307–319, 326–365, 384–424, 443–474, 494–532
SMARCB1 39–55, 154–167, 182–203, 376–386 35–72, 144–206, 373–386
SMO 186–218, 310–340, 399–418, 516–542, 626–646 186–228, 307–331, 391–419, 511–542, 608–646
SRC 514–534 499–533
STK11 30–62, 174–199, 253–281, 325–360 22–64, 155–181, 191–207, 253–285, 317–361
TP53 1–18, 81–114, 126–135, 149–181, 187–223, 230–253, 269–306, 332–344 1–20, 68–113, 126–138, 149–223, 225–258, 263–307, 332–367
VHL 88–110, 120–149, 147–175 78–108, 114–150, 155–174

Reproduced with permission from Meric-Bernstam F, Brusco L, Shaw K, et al. Feasibility of Large-Scale Genomic Testing to Facilitate Enrollment Onto Genomically Matched Clinical Trials. J Clin Oncol 2015;33:2753-62.

Ethical Statement: The study was approved by institutional ethics board of MD Anderson Cancer Center (NCT01772771) and Mayo Clinic (15-000563).

Footnotes

Conflicts of Interest: The authors have no conflicts of interest to declare.

References

  • 1.Torre LA, Bray F, Siegel RL, et al. Global cancer statistics, 2012. CA Cancer J Clin 2015;65:87-108. 10.3322/caac.21262 [DOI] [PubMed] [Google Scholar]
  • 2.Elbasmi A, Al-Asfour A, Al-Nesf Y, et al. Cancer in Kuwait: magnitude of the problem. Gulf J Oncolog 2010;(8):7-14. [PubMed] [Google Scholar]
  • 3.Ibrahim EM, Zeeneldin AA, El-Khodary TR, et al. Past, present and future of colorectal cancer in the Kingdom of Saudi Arabia. Saudi J Gastroenterol 2008;14:178-82. 10.4103/1319-3767.43275 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 4.Alsanea N, Abduljabbar A, Alhomoud S, et al. Colorectal cancer in Saudi Arabia: incidence, survival, demographics and implications for national policies. Ann Saudi Med 2015;35:196-202. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 5.El-Basmy A, Al-Mohannadi S, Al-Awadi A. Some epidemiological measures of cancer in Kuwait: national cancer registry data from 2000-2009. Asian Pac J Cancer Prev 2012;13:3113-8. 10.7314/APJCP.2012.13.7.3113 [DOI] [PubMed] [Google Scholar]
  • 6.McCubrey JA, Steelman LS, Chappell WH, et al. Roles of the Raf/MEK/ERK pathway in cell growth, malignant transformation and drug resistance. Biochim Biophys Acta 2007;1773:1263-84. [DOI] [PMC free article] [PubMed]
  • 7.Peyssonnaux C, Eychene A. The Raf/MEK/ERK pathway: new concepts of activation. Biol Cell 2001;93:53-62. 10.1016/S0248-4900(01)01125-X [DOI] [PubMed] [Google Scholar]
  • 8.Calistri D, Rengucci C, Seymour I, et al. Mutation analysis of TP53, K-ras, and BRAF genes in colorectal cancer progression. J Cell Physiol 2005;204:484-8. 10.1002/jcp.20310 [DOI] [PubMed] [Google Scholar]
  • 9.Zhang J, Zheng J, Yang Y, et al. Molecular spectrum of KRAS, NRAS, BRAF and PIK3CA mutations in Chinese colorectal cancer patients: analysis of 1,110 cases. Sci Rep 2015;5:18678. 10.1038/srep18678 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 10.Bokemeyer C, Van Cutsem E, Rougier P, et al. Addition of cetuximab to chemotherapy as first-line treatment for KRAS wild-type metastatic colorectal cancer: pooled analysis of the CRYSTAL and OPUS randomised clinical trials. Eur J Cancer 2012;48:1466-75. 10.1016/j.ejca.2012.02.057 [DOI] [PubMed] [Google Scholar]
  • 11.Wei Q, Shui Y, Zheng S, et al. EGFR, HER2 and HER3 expression in primary colorectal carcinomas and corresponding metastases: Implications for targeted radionuclide therapy. Oncol Rep 2011;25:3-11. [PubMed] [Google Scholar]
  • 12.Wilson PM, Labonte MJ, Lenz HJ. Molecular markers in the treatment of metastatic colorectal cancer. Cancer J 2010;16:262-72. 10.1097/PPO.0b013e3181e07738 [DOI] [PubMed] [Google Scholar]
  • 13.De Roock W, Claes B, Bernasconi D, et al. Effects of KRAS, BRAF, NRAS, and PIK3CA mutations on the efficacy of cetuximab plus chemotherapy in chemotherapy-refractory metastatic colorectal cancer: a retrospective consortium analysis. Lancet Oncol 2010;11:753-62. 10.1016/S1470-2045(10)70130-3 [DOI] [PubMed] [Google Scholar]
  • 14.De Roock W, Lambrechts D, Tejpar S. K-ras mutations and cetuximab in colorectal cancer. N Engl J Med 2009;360:834; author reply 835-6. [PubMed] [Google Scholar]
  • 15.Laurent-Puig P, Cayre A, Manceau G, et al. Analysis of PTEN, BRAF, and EGFR status in determining benefit from cetuximab therapy in wild-type KRAS metastatic colon cancer. J Clin Oncol 2009;27:5924-30. 10.1200/JCO.2008.21.6796 [DOI] [PubMed] [Google Scholar]
  • 16.Sartore-Bianchi A, Di Nicolantonio F, Nichelatti M, et al. Multi-determinants analysis of molecular alterations for predicting clinical benefit to EGFR-targeted monoclonal antibodies in colorectal cancer. PLoS One 2009;4:e7287. 10.1371/journal.pone.0007287 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 17.Shen Y, Wang J, Han X, et al. Effectors of epidermal growth factor receptor pathway: the genetic profiling of KRAS, BRAF, PIK3CA, NRAS mutations in colorectal cancer characteristics and personalized medicine. PLoS One 2013;8:e81628. 10.1371/journal.pone.0081628 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 18.Smith CG, Fisher D, Claes B, et al. Somatic profiling of the epidermal growth factor receptor pathway in tumors from patients with advanced colorectal cancer treated with chemotherapy +/- cetuximab. Clin Cancer Res 2013;19:4104-13. 10.1158/1078-0432.CCR-12-2581 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 19.Siraj AK, Bu R, Prabhakaran S, et al. A very low incidence of BRAF mutations in Middle Eastern colorectal carcinoma. Mol Cancer 2014;13:168. 10.1186/1476-4598-13-168 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 20.Elbjeirami WM, Sughayer MA. KRAS mutations and subtyping in colorectal cancer in Jordanian patients. Oncol Lett 2012;4:705-10. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 21.Soliman AS, Bondy ML, Levin B, et al. Colorectal cancer in Egyptian patients under 40 years of age. Int J Cancer 1997;71:26-30. [DOI] [PubMed] [Google Scholar]
  • 22.Soliman AS, Bondy ML, El-Badawy SA, et al. Contrasting molecular pathology of colorectal carcinoma in Egyptian and Western patients. Br J Cancer 2001;85:1037-46. 10.1054/bjoc.2001.1838 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 23.Chan AO, Soliman AS, Zhang Q, et al. Differing DNA methylation patterns and gene mutation frequencies in colorectal carcinomas from Middle Eastern countries. Clin Cancer Res 2005;11:8281-7. 10.1158/1078-0432.CCR-05-1000 [DOI] [PubMed] [Google Scholar]
  • 24.Beg S, Siraj AK, Prabhakaran S, et al. Molecular markers and pathway analysis of colorectal carcinoma in the Middle East. Cancer 2015;121:3799-808. 10.1002/cncr.29580 [DOI] [PubMed] [Google Scholar]
  • 25.Atreya CE, Corcoran RB, Kopetz S. Expanded RAS: refining the patient population. J Clin Oncol 2015;33:682-5. 10.1200/JCO.2014.58.9325 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 26.Nebel A, Landau-Tasseron E, Filon D, et al. Genetic evidence for the expansion of Arabian tribes into the Southern Levant and North Africa. Am J Hum Genet 2002;70:1594-6. 10.1086/340669 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 27.Abubaker J, Bavi P, Al-Harbi S, et al. Clinicopathological analysis of colorectal cancers with PIK3CA mutations in Middle Eastern population. Oncogene 2008;27:3539-45. 10.1038/sj.onc.1211013 [DOI] [PubMed] [Google Scholar]
  • 28.Bougatef K, Ouerhani S, Moussa A, et al. Prevalence of mutations in APC, CTNNB1, and BRAF in Tunisian patients with sporadic colorectal cancer. Cancer Genet Cytogenet 2008;187:12-8. 10.1016/j.cancergencyto.2008.06.016 [DOI] [PubMed] [Google Scholar]
  • 29.Naghibalhossaini F, Hosseini HM, Mokarram P, et al. High frequency of genes' promoter methylation, but lack of BRAF V600E mutation among Iranian colorectal cancer patients. Pathol Oncol Res 2011;17:819-25. 10.1007/s12253-011-9388-5 [DOI] [PubMed] [Google Scholar]
  • 30.Al-Allawi NA, Ismaeel AT, Ahmed NY, et al. The frequency and spectrum of K-ras mutations among Iraqi patients with sporadic colorectal carcinoma. Indian J Cancer 2012;49:163-8. 10.4103/0019-509X.98943 [DOI] [PubMed] [Google Scholar]
  • 31.Ozen F, Ozdemir S, Zemheri E, et al. The proto-oncogene KRAS and BRAF profiles and some clinical characteristics in colorectal cancer in the Turkish population. Genet Test Mol Biomarkers 2013;17:135-9. 10.1089/gtmb.2012.0290 [DOI] [PubMed] [Google Scholar]
  • 32.Bader T, Ismail A. Higher prevalence of KRAS mutations in colorectal cancer in Saudi Arabia: Propensity for lung metastasis. Alexandria Journal of Medicine 2014;50:203-9. 10.1016/j.ajme.2014.01.003 [DOI] [Google Scholar]
  • 33.Zahrani A, Kandil M, Badar T, et al. Clinico-pathological study of K-ras mutations in colorectal tumors in Saudi Arabia. Tumori 2014;100:75-9. [DOI] [PubMed] [Google Scholar]
  • 34.Asl JM, Almasi S, Tabatabaiefar MA. High frequency of BRAF proto-oncogene hot spot mutation V600E in cohort of colorectal cancer patients from Ahvaz City, southwest Iran. Pak J Biol Sci 2014;17:565-9. 10.3923/pjbs.2014.565.569 [DOI] [PubMed] [Google Scholar]
  • 35.Hasanpour M, Galehdari H, Masjedizadeh A, et al. A unique profile of adenomatous polyposis coli gene mutations in Iranian patients suffering sporadic colorectal cancer. Cell J 2014;16:17-24. [PMC free article] [PubMed] [Google Scholar]
  • 36.Siyar Ekinci A, Demirci U, Cakmak Oksuzoglu B, et al. KRAS discordance between primary and metastatic tumor in patients with metastatic colorectal carcinoma. J BUON 2015;20:128-35. [PubMed] [Google Scholar]
  • 37.Omidifar NM, Geramizadeh BM, Mirzai MM. K-ras mutation in colorectal cancer, a report from southern Iran. Iran J Med Sci 2015;40:454-60. [PMC free article] [PubMed] [Google Scholar]
  • 38.Løvig T, Meling GI, Diep CB, et al. APC and CTNNB1 mutations in a large series of sporadic colorectal carcinomas stratified by the microsatellite instability status. Scand J Gastroenterol 2002;37:1184-93. 10.1080/003655202760373407 [DOI] [PubMed] [Google Scholar]
  • 39.Smith G, Carey FA, Beattie J, et al. Mutations in APC, Kirsten-ras, and TP53--alternative genetic pathways to colorectal cancer. Proc Natl Acad Sci U S A 2002;99:9433-8. 10.1073/pnas.122612899 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 40.Velho S, Oliveira C, Ferreira A, et al. The prevalence of PIK3CA mutations in gastric and colon cancer. Eur J Cancer 2005;41:1649-54. 10.1016/j.ejca.2005.04.022 [DOI] [PubMed] [Google Scholar]
  • 41.Lüchtenborg M, Weijenberg MP, Wark PA, et al. Mutations in APC, CTNNB1 and K-ras genes and expression of hMLH1 in sporadic colorectal carcinomas from the Netherlands Cohort Study. BMC Cancer 2005;5:160. 10.1186/1471-2407-5-160 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 42.Samowitz WS, Slattery ML, Sweeney C, et al. APC mutations and other genetic and epigenetic changes in colon cancer. Mol Cancer Res 2007;5:165-70. 10.1158/1541-7786.MCR-06-0398 [DOI] [PubMed] [Google Scholar]
  • 43.Prall F, Weirich V, Ostwald C. Phenotypes of invasion in sporadic colorectal carcinomas related to aberrations of the adenomatous polyposis coli (APC) gene. Histopathology 2007;50:318-30. 10.1111/j.1365-2559.2007.02609.x [DOI] [PubMed] [Google Scholar]
  • 44.Barault L, Veyrie N, Jooste V, et al. Mutations in the RAS-MAPK, PI(3)K (phosphatidylinositol-3-OH kinase) signaling network correlate with poor survival in a population-based series of colon cancers. Int J Cancer 2008;122:2255-9. 10.1002/ijc.23388 [DOI] [PubMed] [Google Scholar]
  • 45.Kámory E, Olasz J, Csuka O. Somatic APC inactivation mechanisms in sporadic colorectal cancer cases in Hungary. Pathol Oncol Res 2008;14:51-6. 10.1007/s12253-008-9019-y [DOI] [PubMed] [Google Scholar]
  • 46.Freeman DJ, Juan T, Reiner M, et al. Association of K-ras mutational status and clinical outcomes in patients with metastatic colorectal cancer receiving panitumumab alone. Clin Colorectal Cancer 2008;7:184-90. 10.3816/CCC.2008.n.024 [DOI] [PubMed] [Google Scholar]
  • 47.Simi L, Pratesi N, Vignoli M, et al. High-resolution melting analysis for rapid detection of KRAS, BRAF, and PIK3CA gene mutations in colorectal cancer. Am J Clin Pathol 2008;130:247-53. 10.1309/LWDY1AXHXUULNVHQ [DOI] [PubMed] [Google Scholar]
  • 48.Perrone F, Lampis A, Orsenigo M, et al. PI3KCA/PTEN deregulation contributes to impaired responses to cetuximab in metastatic colorectal cancer patients. Ann Oncol 2009;20:84-90. 10.1093/annonc/mdn541 [DOI] [PubMed] [Google Scholar]
  • 49.Ogino S, Nosho K, Kirkner GJ, et al. PIK3CA mutation is associated with poor prognosis among patients with curatively resected colon cancer. J Clin Oncol 2009;27:1477-84. 10.1200/JCO.2008.18.6544 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 50.Souglakos J, Philips J, Wang R, et al. Prognostic and predictive value of common mutations for treatment response and survival in patients with metastatic colorectal cancer. Br J Cancer 2009;101:465-72. 10.1038/sj.bjc.6605164 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 51.Lurkin I, Stoehr R, Hurst CD, et al. Two multiplex assays that simultaneously identify 22 possible mutation sites in the KRAS, BRAF, NRAS and PIK3CA genes. PLoS One 2010;5:e8802. 10.1371/journal.pone.0008802 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 52.Perkins G, Lievre A, Ramacci C, et al. Additional value of EGFR downstream signaling phosphoprotein expression to KRAS status for response to anti-EGFR antibodies in colorectal cancer. Int J Cancer 2010;127:1321-31. 10.1002/ijc.25152 [DOI] [PubMed] [Google Scholar]
  • 53.Janku F, Lee JJ, Tsimberidou AM, et al. PIK3CA mutations frequently coexist with RAS and BRAF mutations in patients with advanced cancers. PLoS One 2011;6:e22769. 10.1371/journal.pone.0022769 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 54.Bozzao C, Varvara D, Piglionica M, et al. Survey of KRAS, BRAF and PIK3CA mutational status in 209 consecutive Italian colorectal cancer patients. Int J Biol Markers 2012;27:e366-74. 10.5301/JBM.2012.9765 [DOI] [PubMed] [Google Scholar]
  • 55.Palomba G, Colombino M, Contu A, et al. Prevalence of KRAS, BRAF, and PIK3CA somatic mutations in patients with colorectal carcinoma may vary in the same population: clues from Sardinia. J Transl Med 2012;10:178. 10.1186/1479-5876-10-178 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 56.Nishihara R, Lochhead P, Kuchiba A, et al. Aspirin use and risk of colorectal cancer according to BRAF mutation status. JAMA 2013;309:2563-71. 10.1001/jama.2013.6599 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 57.Guedes JG, Veiga I, Rocha P, et al. High resolution melting analysis of KRAS, BRAF and PIK3CA in KRAS exon 2 wild-type metastatic colorectal cancer. BMC Cancer 2013;13:169. 10.1186/1471-2407-13-169 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 58.Yanus GA, Belyaeva AV, Ivantsov AO, et al. Pattern of clinically relevant mutations in consecutive series of Russian colorectal cancer patients. Med Oncol 2013;30:686. 10.1007/s12032-013-0686-5 [DOI] [PubMed] [Google Scholar]
  • 59.Rosty C, Young JP, Walsh MD, et al. PIK3CA activating mutation in colorectal carcinoma: associations with molecular features and survival. PLoS One 2013;8:e65479. 10.1371/journal.pone.0065479 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 60.Derbel O, Wang Q, Desseigne F, et al. Impact of KRAS, BRAF and PI3KCA mutations in rectal carcinomas treated with neoadjuvant radiochemotherapy and surgery. BMC cancer 2013;13:200. 10.1186/1471-2407-13-200 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 61.Neumann J, Wehweck L, Maatz S, et al. Alterations in the EGFR pathway coincide in colorectal cancer and impact on prognosis. Virchows Arch 2013;463:509-23. 10.1007/s00428-013-1450-0 [DOI] [PubMed] [Google Scholar]
  • 62.Martinetti D, Costanzo R, Kadare S, et al. KRAS and BRAF mutational status in colon cancer from Albanian patients. Diagn Pathol 2014;9:187. 10.1186/s13000-014-0187-7 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 63.Kosmidou V, Oikonomou E, Vlassi M, et al. Tumor heterogeneity revealed by KRAS, BRAF, and PIK3CA pyrosequencing: KRAS and PIK3CA intratumor mutation profile differences and their therapeutic implications. Hum Mutat 2014;35:329-40. 10.1002/humu.22496 [DOI] [PubMed] [Google Scholar]
  • 64.Gil Ferreira C, Aran V, Zalcberg-Renault I, et al. KRAS mutations: variable incidences in a Brazilian cohort of 8,234 metastatic colorectal cancer patients. BMC Gastroenterol 2014;14:73. 10.1186/1471-230X-14-73 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 65.Hurtado C, Encina G, Wielandt AM, et al. KRAS gene somatic mutations in Chilean patients with colorectal cancer. Rev Med Chil 2014;142:1407-14. 10.4067/S0034-98872014001100007 [DOI] [PubMed] [Google Scholar]
  • 66.Foltran L, De Maglio G, Pella N, et al. Prognostic role of KRAS, NRAS, BRAF and PIK3CA mutations in advanced colorectal cancer. Future Oncol 2015;11:629-40. 10.2217/fon.14.279 [DOI] [PubMed] [Google Scholar]
  • 67.Morris VK, Lucas FA, Overman MJ, et al. Clinicopathologic characteristics and gene expression analyses of non-KRAS 12/13, RAS-mutated metastatic colorectal cancer. Ann Oncol 2014;25:2008-14. 10.1093/annonc/mdu252 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 68.Samara M, Kapatou K, Ioannou M, et al. Mutation profile of KRAS and BRAF genes in patients with colorectal cancer: association with morphological and prognostic criteria. Genet Mol Res 2015;14:16793-802. 10.4238/2015.December.14.6 [DOI] [PubMed] [Google Scholar]
  • 69.Barresi V, Bonetti LR, Bettelli S. KRAS, NRAS, BRAF mutations and high counts of poorly differentiated clusters of neoplastic cells in colorectal cancer: observational analysis of 175 cases. Pathology 2015;47:551-6. 10.1097/PAT.0000000000000300 [DOI] [PubMed] [Google Scholar]
  • 70.de Macêdo MP, de Melo FM, Lisboa BC, et al. KRAS gene mutation in a series of unselected colorectal carcinoma patients with prognostic morphological correlations: a pyrosequencing method improved by nested PCR. Exp Mol Pathol 2015;98:563-7. 10.1016/j.yexmp.2015.03.038 [DOI] [PubMed] [Google Scholar]
  • 71.Saridaki Z, Saegart X, De Vriendt V, et al. KRAS, NRAS, BRAF mutation comparison of endoscopic and surgically removed primary CRC paired samples: is endoscopy biopsy material adequate for molecular evaluation? Br J Cancer 2015;113:914-20. 10.1038/bjc.2015.307 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 72.Margonis GA, Kim Y, Spolverato G, et al. Association between specific mutations in KRAS codon 12 and colorectal liver metastasis. JAMA Surg 2015;150:722-9. 10.1001/jamasurg.2015.0313 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 73.Schirripa M, Bergamo F, Cremolini C, et al. BRAF and RAS mutations as prognostic factors in metastatic colorectal cancer patients undergoing liver resection. Br J Cancer 2015;112:1921-8. 10.1038/bjc.2015.142 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 74.Vignot S, Lefebvre C, Frampton GM, et al. Comparative analysis of primary tumour and matched metastases in colorectal cancer patients: evaluation of concordance between genomic and transcriptional profiles. Eur J Cancer 2015;51:791-9. 10.1016/j.ejca.2015.02.012 [DOI] [PubMed] [Google Scholar]
  • 75.Ilm K, Kemmner W, Osterland M, et al. High MACC1 expression in combination with mutated KRAS G13 indicates poor survival of colorectal cancer patients. Mol Cancer 2015;14:38. 10.1186/s12943-015-0316-2 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 76.Renaud S, Romain B, Falcoz PE, et al. KRAS and BRAF mutations are prognostic biomarkers in patients undergoing lung metastasectomy of colorectal cancer. Br J Cancer 2015;112:720-8. 10.1038/bjc.2014.499 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 77.Manceau G, Marisa L, Boige V, et al. PIK3CA mutations predict recurrence in localized microsatellite stable colon cancer. Cancer Med 2015;4:371-82. 10.1002/cam4.370 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 78.Meric-Bernstam F, Brusco L, Shaw K, et al. Feasibility of large-scale genomic testing to facilitate enrollment onto genomically matched clinical trials. J Clin Oncol 2015;33:2753-62. 10.1200/JCO.2014.60.4165 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 79.Miyaki M, Iijima T, Ishii R, et al. Increased frequency of TP53 mutation in sporadic colorectal cancer from cigarette smokers. Jpn J Clin Oncol 2002;32:196-201. 10.1093/jjco/hyf047 [DOI] [PubMed] [Google Scholar]
  • 80.Jeon CH, Lee HI, Shin IH, et al. Genetic alterations of APC, K-ras, TP53, MSI, and MAGE in Korean colorectal cancer patients. Int J Colorectal Dis 2008;23:29-35. 10.1007/s00384-007-0373-0 [DOI] [PubMed] [Google Scholar]
  • 81.Berg M, Danielsen SA, Ahlquist T, et al. DNA sequence profiles of the colorectal cancer critical gene set KRAS-BRAF-PIK3CA-PTEN-TP53 related to age at disease onset. PLoS One 2010;5:e13978. 10.1371/journal.pone.0013978 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 82.Liao W, Liao Y, Zhou JX, et al. Gene mutations in epidermal growth factor receptor signaling network and their association with survival in Chinese patients with metastatic colorectal cancers. Anat Rec (Hoboken) 2010;293:1506-11. 10.1002/ar.21202 [DOI] [PubMed] [Google Scholar]
  • 83.Kwon MJ, Lee SE, Kang SY, et al. Frequency of KRAS, BRAF, and PIK3CA mutations in advanced colorectal cancers: Comparison of peptide nucleic acid-mediated PCR clamping and direct sequencing in formalin-fixed, paraffin-embedded tissue. Pathol Res Pract 2011;207:762-8. 10.1016/j.prp.2011.10.002 [DOI] [PubMed] [Google Scholar]
  • 84.Aoyagi H, Iida S, Uetake H, et al. Effect of classification based on combination of mutation and methylation in colorectal cancer prognosis. Oncol Rep 2011;25:789-94. [DOI] [PubMed] [Google Scholar]
  • 85.Hsieh LL, Er TK, Chen CC, et al. Characteristics and prevalence of KRAS, BRAF, and PIK3CA mutations in colorectal cancer by high-resolution melting analysis in Taiwanese population. Clin Chim Acta 2012;413:1605-11. 10.1016/j.cca.2012.04.029 [DOI] [PubMed] [Google Scholar]
  • 86.Ling Y, Ying JM, Qiu T, et al. Detection of KRAS, BRAF, PIK3CA and EGFR gene mutations in colorectal carcinoma. Zhonghua Bing Li Xue Za Zhi 2012;41:590-4. [DOI] [PubMed] [Google Scholar]
  • 87.Mao C, Zhou J, Yang Z, et al. KRAS, BRAF and PIK3CA mutations and the loss of PTEN expression in Chinese patients with colorectal cancer. PLoS ONE 2012;7:e36653. 10.1371/journal.pone.0036653 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 88.Bando H, Yoshino T, Shinozaki E, et al. Simultaneous identification of 36 mutations in KRAS codons 61 and 146, BRAF, NRAS, and PIK3CA in a single reaction by multiplex assay kit. BMC Cancer 2013;13:405. 10.1186/1471-2407-13-405 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 89.Yip WK, Choo CW, Leong VC, et al. Molecular alterations of Ras-Raf-mitogen-activated protein kinase and phosphatidylinositol 3-kinase-Akt signaling pathways in colorectal cancers from a tertiary hospital at Kuala Lumpur, Malaysia. APMIS 2013;121:954-66. 10.1111/apm.12152 [DOI] [PubMed] [Google Scholar]
  • 90.Nakanishi R, Harada J, Tuul M, et al. Prognostic relevance of KRAS and BRAF mutations in Japanese patients with colorectal cancer. Int J Clin Oncol 2013;18:1042-8. 10.1007/s10147-012-0501-x [DOI] [PubMed] [Google Scholar]
  • 91.Soeda H, Shimodaira H, Watanabe M, et al. Clinical usefulness of KRAS, BRAF, and PIK3CA mutations as predictive markers of cetuximab efficacy in irinotecan- and oxaliplatin-refractory Japanese patients with metastatic colorectal cancer. Int J Clin Oncol 2013;18:670-7. 10.1007/s10147-012-0422-8 [DOI] [PubMed] [Google Scholar]
  • 92.Chang YS, Chang SJ, Yeh KT, et al. RAS, BRAF, and TP53 gene mutations in Taiwanese colorectal cancer patients. Onkologie 2013;36:719-24. [DOI] [PubMed] [Google Scholar]
  • 93.Patil H, Korde R, Kapat A. KRAS gene mutations in correlation with clinicopathological features of colorectal carcinomas in Indian patient cohort. Med Oncol 2013;30:617. 10.1007/s12032-013-0617-5 [DOI] [PubMed] [Google Scholar]
  • 94.Sinha R, Hussain S, Mehrotra R, et al. Kras gene mutation and RASSF1A, FHIT and MGMT gene promoter hypermethylation: indicators of tumor staging and metastasis in adenocarcinomatous sporadic colorectal cancer in Indian population. PLoS One 2013;8:e60142. 10.1371/journal.pone.0060142 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 95.Malhotra P, Anwar M, Nanda N, et al. Alterations in K-ras, APC and TP53-multiple genetic pathway in colorectal cancer among Indians. Tumour Biol 2013;34:1901-11. 10.1007/s13277-013-0734-y [DOI] [PubMed] [Google Scholar]
  • 96.Bisht S, Ahmad F, Sawaimoon S, et al. Molecular spectrum of KRAS, BRAF, and PIK3CA gene mutation: determination of frequency, distribution pattern in Indian colorectal carcinoma. Med Oncol 2014;31:124. 10.1007/s12032-014-0124-3 [DOI] [PubMed] [Google Scholar]
  • 97.Murtaza BN, Bibi A, Rashid MU, et al. Spectrum of K ras mutations in Pakistani colorectal cancer patients. Braz J Med Biol Res 2014;47:35-41. 10.1590/1414-431X20133046 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 98.Cai ZX, Tang XX, Gao HL, et al. APC, FBXW7, KRAS, PIK3CA, and TP53 Gene Mutations in Human Colorectal Cancer Tumors Frequently Detected by Next-Generation DNA Sequencing. J Mol Genet Med 2014;8:145. [Google Scholar]
  • 99.Kadowaki S, Kakuta M, Takahashi S, et al. Prognostic value of KRAS and BRAF mutations in curatively resected colorectal cancer. World J Gastroenterol 2015;21:1275-83. 10.3748/wjg.v21.i4.1275 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 100.Ye JX, Liu Y, Qin Y, et al. KRAS and BRAF gene mutations and DNA mismatch repair status in Chinese colorectal carcinoma patients. World J Gastroenterol 2015;21:1595-605. 10.3748/wjg.v21.i5.1595 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 101.Kawazoe A, Shitara K, Fukuoka S, et al. A retrospective observational study of clinicopathological features of KRAS, NRAS, BRAF and PIK3CA mutations in Japanese patients with metastatic colorectal cancer. BMC Cancer 2015;15:258. 10.1186/s12885-015-1276-z [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 102.Phua LC, Ng HW, Yeo AH, et al. Prevalence of KRAS, BRAF, PI3K and EGFR mutations among Asian patients with metastatic colorectal cancer. Oncol Lett 2015;10:2519-26. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 103.Lee JW, Lee JH, Shim BY, et al. KRAS mutation status is not a predictor for tumor response and survival in rectal cancer patients who received preoperative radiotherapy with 5-fluoropyrimidine followed by curative surgery. Medicine (Baltimore) 2015;94:e1284. 10.1097/MD.0000000000001284 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 104.Kawada K, Toda K, Nakamoto Y, et al. Relationship between 18F-FDG PET/CT scans and KRAS mutations in metastatic colorectal cancer. J Nucl Med 2015;56:1322-7. 10.2967/jnumed.115.160614 [DOI] [PubMed] [Google Scholar]
  • 105.Lan YT, Jen-Kou L, Lin CH, et al. Mutations in the RAS and PI3K pathways are associated with metastatic location in colorectal cancers. J Surg Oncol 2015;111:905-10. 10.1002/jso.23895 [DOI] [PubMed] [Google Scholar]
  • 106.Bourne HR, Sanders DA, McCormick F. The GTPase superfamily: conserved structure and molecular mechanism. Nature 1991;349:117-27. 10.1038/349117a0 [DOI] [PubMed] [Google Scholar]
  • 107.Harari PM, Allen GW, Bonner JA. Biology of interactions: antiepidermal growth factor receptor agents. J Clin Oncol 2007;25:4057-65. 10.1200/JCO.2007.11.8984 [DOI] [PubMed] [Google Scholar]
  • 108.Tran B, Kopetz S, Tie J, et al. Impact of BRAF mutation and microsatellite instability on the pattern of metastatic spread and prognosis in metastatic colorectal cancer. Cancer 2011;117:4623-32. 10.1002/cncr.26086 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 109.Mao C, Yang Z, Hu X, et al. PIK3CA exon 20 mutations as a potential biomarker for resistance to anti-EGFR monoclonal antibodies in KRAS wild-type metastatic colorectal cancer: a systematic review and meta-analysis. Annals of oncology 2012;23:1518-25. 10.1093/annonc/mdr464 [DOI] [PubMed] [Google Scholar]
  • 110.Russo A, Bazan V, Iacopetta B, et al. The TP53 colorectal cancer international collaborative study on the prognostic and predictive significance of TP53 mutation: influence of tumor site, type of mutation, and adjuvant treatment. J Clin Oncol 2005;23:7518-28. 10.1200/JCO.2005.00.471 [DOI] [PubMed] [Google Scholar]
  • 111.Dhomen N, Marais R. New insight into BRAF mutations in cancer. Curr Opin Genet Dev 2007;17:31-9. 10.1016/j.gde.2006.12.005 [DOI] [PubMed] [Google Scholar]
  • 112.Engelman JA. Targeting PI3K signalling in cancer: opportunities, challenges and limitations. Nat Rev Cancer 2009;9:550-62. 10.1038/nrc2664 [DOI] [PubMed] [Google Scholar]
  • 113.Béroud C, Soussi T. APC gene: database of germline and somatic mutations in human tumors and cell lines. Nucleic Acids Res 1996;24:121-4. 10.1093/nar/24.1.121 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 114.Samowitz WS, Curtin K, Ma KN, et al. Prognostic significance of TP53 mutations in colon cancer at the population level. Int J Cancer 2002;99:597-602. 10.1002/ijc.10405 [DOI] [PubMed] [Google Scholar]
  • 115.Akhoondi S, Sun D, von der Lehr N, et al. FBXW7/hCDC4 is a general tumor suppressor in human cancer. Cancer Res 2007;67:9006-12. 10.1158/0008-5472.CAN-07-1320 [DOI] [PubMed] [Google Scholar]
  • 116.Chang CC, Lin HH, Lin JK, et al. FBXW7 mutation analysis and its correlation with clinicopathological features and prognosis in colorectal cancer patients. Int J Biol Markers 2015;30:e88-95. 10.5301/jbm.5000125 [DOI] [PubMed] [Google Scholar]
  • 117.Grim JE. Fbxw7 hotspot mutations and human colon cancer: mechanistic insights from new mouse models. Gut 2014;63:707-9. 10.1136/gutjnl-2013-305144 [DOI] [PubMed] [Google Scholar]
  • 118.Fleming NI, Jorissen RN, Mouradov D, et al. SMAD2, SMAD3 and SMAD4 Mutations in Colorectal Cancer. Cancer Research 2013;73:725-35. 10.1158/0008-5472.CAN-12-2706 [DOI] [PubMed] [Google Scholar]
  • 119.Markowitz S, Wang J, Myeroff L, et al. Inactivation of the type II TGF-beta receptor in colon cancer cells with microsatellite instability. Science 1995;268:1336-8. 10.1126/science.7761852 [DOI] [PubMed] [Google Scholar]
  • 120.Woodford-Richens KL, Rowan AJ, Gorman P, et al. SMAD4 mutations in colorectal cancer probably occur before chromosomal instability, but after divergence of the microsatellite instability pathway. Proc Natl Acad Sci U S A 2001;98:9719-23. 10.1073/pnas.171321498 [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 121.Linardou H, Dahabreh IJ, Kanaloupiti D, et al. Assessment of somatic k-RAS mutations as a mechanism associated with resistance to EGFR-targeted agents: a systematic review and meta-analysis of studies in advanced non-small-cell lung cancer and metastatic colorectal cancer. Lancet Oncol 2008;9:962-72. 10.1016/S1470-2045(08)70206-7 [DOI] [PubMed] [Google Scholar]
  • 122.Armstrong B, Doll R. Environmental factors and cancer incidence and mortality in different countries, with special reference to dietary practices. Int J Cancer 1975;15:617-31. 10.1002/ijc.2910150411 [DOI] [PubMed] [Google Scholar]
  • 123.McKeown-Eyssen G. Epidemiology of colorectal cancer revisited: are serum triglycerides and/or plasma glucose associated with risk? Cancer Epidemiol Biomarkers Prev 1994;3:687-95. [PubMed] [Google Scholar]
  • 124.Prentice RL, Sheppard L. Dietary fat and cancer: consistency of the epidemiologic data, and disease prevention that may follow from a practical reduction in fat consumption. Cancer Causes Control 1990;1:81-97. 10.1007/BF00053187 [DOI] [PubMed] [Google Scholar]
  • 125.Friedenreich CM, Orenstein MR. Physical activity and cancer prevention: etiologic evidence and biological mechanisms. J Nutr 2002;132:3456S-3464S. [DOI] [PubMed] [Google Scholar]
  • 126.Calle EE, Rodriguez C, Walker-Thurmond K, et al. Overweight, obesity, and mortality from cancer in a prospectively studied cohort of US adults. N Engl J Med 2003;348:1625-38. 10.1056/NEJMoa021423 [DOI] [PubMed] [Google Scholar]
  • 127.Popkin BM. The nutrition transition in low-income countries: an emerging crisis. Nutr Rev 1994;52:285-98. 10.1111/j.1753-4887.1994.tb01460.x [DOI] [PubMed] [Google Scholar]
  • 128.Siegel R, Ward E, Brawley O, et al. Cancer statistics, 2011: the impact of eliminating socioeconomic and racial disparities on premature cancer deaths. CA Cancer J Clin 2011;61:212-36. 10.3322/caac.20121 [DOI] [PubMed] [Google Scholar]
  • 129.Fireman Z, Sandler E, Kopelman Y, et al. Ethnic differences in colorectal cancer among Arab and Jewish neighbors in Israel. Am J Gastroenterol 2001;96:204-7. 10.1111/j.1572-0241.2001.03476.x [DOI] [PubMed] [Google Scholar]
  • 130.Bener A, Moore MA, Ali R, et al. Impacts of family history and lifestyle habits on colorectal cancer risk: a case-control study in Qatar. Asian Pac J Cancer Prev 2010;11:963-8. [PubMed] [Google Scholar]
  • 131.Arafa MA, Waly MI, Jriesat S, et al. Dietary and lifestyle characteristics of colorectal cancer in Jordan: a case-control study. Asian Pac J Cancer Prev 2011;12:1931-6. [PubMed] [Google Scholar]
  • 132.Rozen P, Rosner G, Liphshitz I, et al. The changing incidence and sites of colorectal cancer in the Israeli Arab population and their clinical implications. Int J Cancer 2007;120:147-51. 10.1002/ijc.22141 [DOI] [PubMed] [Google Scholar]

Articles from Journal of Gastrointestinal Oncology are provided here courtesy of AME Publications

RESOURCES