XRCC1 Arg399Gln Genetic Variant Increases Colorectal Cancer Susceptibility: A Comprehensive Meta-Analysis

Abstract

Introduction:

Colorectal cancer (CRC) continues to be a common health condition and one of the most prevalent and lethal cancers worldwide. CRC is the third most leading cancer by incidence and second most common cause of cancer mortality. Emerging evidence showing that inherited genetic variants in genes coding for DNA repair enzymes have potential role in increasing the risk of CRC. Among these, polymorphisms in the XRCC1 has been widely investigated, although the results have been varied in different populations.

Methods:

The current meta-analysis is aimed to explain the relation between three XRCC1 polymorphisms and the CRC risk. Meta-analysis included a combined analysis of 52 case-controls studies including 23 Arg194Trp studies, 8 Arg280His studies, and 42 Arg399Gln studies.

Results:

The results of the present study revealed a statistically significant correlation between the Arg399Gln polymorphism and the increased risk of CRC (OR = 1.10, 95% CI = 1.01–1.20, p = 0.038, random effects model). However, subgroup analysis based on ethnicity revealed no statistical significance between CRC risk and XRCC1 polymorphisms in Asian and Caucasian populations. In addition, no publication bias was found in the current meta-analysis.

Conclusion:

Overall, the data suggest that XRCC1 Arg399Gln might be associated with increased CRC susceptibility, while Arg194Trp and Arg280His are not significantly associated.

Introduction

Colorectal cancer (CRC) is known to be a global health burden, both in the terms of incidence and mortality [1, 2]. It is one of the three most frequently diagnosed cancers in the world and the second in cancer-related deaths. According to global estimates in 2020, approximately 1.9 million new cases and 930,000 deaths were reported due to CRC [3, 4]. Incidence rates differ geographically, with higher rates in developed nations and increasing rates in developing countries that are adopting Western lifestyles [5]. Risk factors include obesity, sedentary lifestyle, red meat consumption, alcohol, and tobacco use. Recent data indicate that approximately one in ten CRC cases occurs in individuals aged 50 years or younger, which is a concerning trend [6]. Early detection through screening programs has contributed to reduced mortality in developed countries [7]. Several biomarkers, such as Carcinoembryonic antigen, CA 19-9, microsatellite instability, K-RAS mutations, and BRAF mutations, are used to monitor treatment response, recurrence, and prognosis of colorectal cancer [8]. Treatment options include surgery, chemotherapy, radiation therapy, and targeted therapies.

Improvements in the treatment of metastatic CRC have come a long way over the last few decades. Initially 5-flurouracil was used as a chemotherapeutic agent for nearly half a century. Treatment regimens now include additional cytotoxic drugs such as irinotecan, oxaliplatin, and capecitabine, which in turn have opened more targeted treatment options [9, 10]. Combination chemotherapy regimens such as FOLFOX and FOLFIRI have shown improved clinical effectiveness [11]. Moreover, targeted drugs using monoclonal antibodies like bevacizumab, cetuximab, and panitumumab have shown better treatment outcomes [12, 13]. These targeted agents, when combined with chemotherapy, have shown improved survival rates and quality of life for metastatic CRC patients [14]. Platinum-based agents such as oxaliplatin via DNA damage mechanisms, mainly by the formation of intra- and interstrand DNA crosslinks that inhibit replication and transcription [15]. Drug resistance to platinum-based drugs is a significant clinical challenge, frequently associated with enhanced DNA repair activity, mainly via the nucleotide excision repair and base excision repair pathways [16].

Among the DNA repair genes, XRCC1 (X-ray repair cross-complementing group 1), present on chromosome 19q13.2, encodes for a 633 amino acid protein that works as a scaffold in base excision repair, single-strand breaks repair, and to lesser extend double-strand break repair [17, 18]. Its role is to coordinate and stabilize multi-protein complexes required for efficient assembly of DNA repair complexes. Several single nucleotide polymorphisms (SNPs) in the XRCC1 gene such as rs1799782 (Arg194Trp), rs25489 (Arg280His) and rs25487 (Arg399Gln), have received a major focus of research due to their potential to influence DNA repair efficiency and their association with increased disease susceptibility. These mutations may change protein structure or function, potentially destabilizing the genome and increasing susceptibility to various cancers, including bladder cancer [19], glioma [20], and lung cancer [21].

In addition, XRCC1 polymorphisms have also been associated with the risk of schizophrenia [22]. The gene’s critical role in DNA repair was initially demonstrated through complementation studies in Chinese hamster ovary cells, where expression of XRCC1 restored DNA strand break repair and reduced chromosomal abnormalities [23]. Previous studies have explained the correlation between XRCC1 gene polymorphisms and CRC susceptibility across diverse ethnic groups, yielding mixed results. Further, no relevant correlation of XRCC1 polymorphisms with CRC has been reported in some studies from Malaysian and Austrian populations [24, 25]. However, other research data reported an increased susceptibility to CRC associated with Arg194Trp and Arg399Gln polymorphisms in Kashmiri and Chinese cohorts [26, 27]. Findings from subsequent studies in other populations are largely inconclusive. These variations could be attributed to difference in sample size, ethnic origin, environmental exposure and study design. Therefore, to investigate the heterogeneity in existing literature regarding XRCC1 gene polymorphism and CRC risk, we conducted a meta-analysis to determine their possible potential role as genetic risk factors.

Materials and Methods

A comprehensive literature search on research papers pertaining to XRCC1 gene polymorphisms and CRC susceptibility was conducted using Web of Science, PubMed, and Embase databases. The MeSh terms and keywords used included “colorectal cancer” or “colorectal carcinoma” or “colorectal tumor” or “colorectal neoplasm”, “XRCC1” or “rs1799782” or “Arg194Trp” or “rs25489” or “Arg280His” or “rs25487” or “Arg399Gln”, and terms related to genetic variations such as “polymorphism” or “SNP” or “variant” or “variation” or “mutation” or “genotype”. Studies were considered eligible if they met the following inclusion criteria: (1) case-control designs; (2) studies explaining the XRCC1 polymorphism correlation with CRC risk; and (3) availability of genotype frequency data for both case and control groups. Exclusion criteria included (1) conference abstracts, letters to the editors, or reviews; (2) studies lacking genotype count data and (3) studies in other languages for data uniformity. The entire search strategy and inclusion of papers is followed with the guidelines set forth by the Meta-analysis of Observational Studies in Epidemiology (MOOSE) [28]. The checklist for MOOSE is available in Supplementary File 1. The last search was performed on March 30, 2025.

Two independent reviewers extracted data from all eligible studies, including the principal author, year of publication, country of study, ethnic origin of the population and genotype distribution in both cases and controls. The methodological quality of included studies was assessed using the Newcastle-Ottawa Scale (NOS) [29]. Hardy-Weinberg equilibrium (HWE) was checked for control group in each study to confirm genetic consistency.

The association between CRC risk and the three XRCC1 polymorphisms, rs1799782 (Arg194Trp), rs25489 (Arg280His) and rs25487 (Arg399Gln) was measured in terms of pooled odds ratio (ORs) with respective 95% confidence intervals (CIs), computed under the dominant genetic model. Between study heterogeneity across studies was assessed by Cochrane’s Q test and the I² statistics (Higgins and Thompson). Based on the degree of heterogeneity, either a fixed-effect model or random-effects model was used for conducting the pooled analysis. For assessing the robustness of the meta-analysis results, prime end point sensitivity analyses were conducted by excluding each study sequentially (“Leave-one-out” approach). Publication bias was estimated by visual inspection of Begg’s funnel plots and tested further using Egger’s regression test. All statistical analyses were performed with the help of MetaGenyo web tool [30].

Results

The study selection process for this meta-analysis is illustrated in Figure 1. A total of 52 eligible case controls studies were included based on predefined criteria (Figure 1). For this meta-analysis, 23 papers with 6821 CRC cases and 10394 controls investigated the XRCC1 Arg194Trp polymorphism [24-27, 31-49], 8 papers with 3750 CRC cases and 4582 controls examined the XRCC1 Arg280His polymorphism [24, 32-34, 39, 40, 42, 47], and 42 papers with 11327 CRC cases and 16343 controls analysed the XRCC1 Arg399Gln polymorphism [24, 25, 31-70], met the inclusion criteria (Table 1). The association of CRC with all three XRCC1 polymorphic variants was evaluated under a dominant model (Table 1).

Figure 1.

The MOOSE Flow Diagram Showing Study Selection Process

Table 1.

Overall Meta-Analysis and Subgroup Analysis by Ethnicity for XRCC1 Arg194Trp, Arg280His and Arg399Gln Polymorphisms

Ethnicity	Number of studies	Test of association		Model	Test of heterogeneity		Egger's test p-value
		OR (95% CI)	p-value		I2%	p-value
2A: XRCC1 rs1799782 Arg194Trp; Dominant model (TT+TC vs. CC)
Overall	23	1.12 (0.97-1.28)	0.125	REM	61	<0.001	0.623
African	2	5.88 (1.19-29.05)	0.029	REM	77	0.04	NA
Asian	9	1.14 (0.97-1.34)	0.109	REM	61	0.008	0.388
Caucasian	9	0.97 (0.80-1.18)	0.772	FEM	0	0.44	0.34
Mixed	3	1.10 (0.92-1.30)	0.291	FEM	10	0.329	0.084
XRCC1 rs25489 Arg280His; Dominant model (AA+AG vs. GG)
Overall	8	1.03 (0.90-1.17)	0.681	FEM	0	0.499	0.163
Asian	4	1.06 (0.88-1.27)	0.518	FEM	12	0.331	0.519
Caucasian	2	1.23 (0.83-1.83)	0.304	FEM	14	0.28	NA
Mixed	2	0.93 (0.75-1.16)	0.516	FEM	0	0.83	NA
XRCC1 rs25487 Arg399Gln; Dominant model (AA+AG vs. GG)
Overall	42	1.10 (1.01-1.20)	0.038	REM	61	<0.001	0.311
African	3	1.73 (0.70-4.31)	0.235	REM	66	0.055	0.91
Asian	17	1.10 (0.97-1.25)	0.14	REM	56	<0.001	0.606
Caucasian	15	1.02 (0.88-1.19)	0.803	REM	38	0.068	0.945
Mixed	7	1.17 (0.93-1.46)	0.176	REM	79	<0.001	0.094

CI, confidence interval; OR, odds ratio; NA, not applicable.; FEM, fixed effects model; REM, random effects model

Pooled analysis of data identified a statistically significant relationship between XRCC1 Arg399Gln polymorphism and increased risk of CRC (OR = 1.10, 95% CI = 1.01–1.20, p = 0.038, random-effects model) (Figure 2C). However, no significant association was seen between Arg194Trp (OR = 1.12, p = 0.125) and Arg280His (OR = 1.03, p = 0.681) variants and CRC risk (Figure 2B). Subgroup analyses based on ethnic background showed no significant association between any of these three XRCC1 variants and the risk of CRC among ethnic groups (Table 1).

Figure 2.

Forest Plot Depicting the Association between CRC and XRCC1 Gene Polymorphisms. CRC, colorectal cancer; Experimental, colorectal cancer cases; Events, mutant genotypes; OR, odds ratio; CI, confidence interval. 

Heterogeneity testing revealed no variability among studies that assessed XRCC1 Arg280His polymorphism (I² = 0%, P = 0.499). Significant moderate heterogeneity was found for the other two polymorphisms, Arg194Trp and Arg399Gln (Arg194Trp: I² = 61%, P < 0.001; Arg399Gln: I² = 61%, P < 0.001). Sensitivity analysis conducted on pooled data using “leave-one-out” approach, established negligible impact on the pooled ORs for all three XRCC1 polymorphisms. This indicates that the results of the current meta-analysis are reliable and consistent (Figure 3). Assessment of possible publication bias by Begg’s funnel plots and Egger regression tests demonstrated symmetrical funnel plots for all three XRCC1 polymorphisms. The p-values of Egger’s test were 0.623 for Arg194Trp, 0.163 for Arg280His, and 0.211 for Arg399Gln, indicating the lack of significant publication bias (Figure 4).

Figure 3.

Sensitivity Analysis Evaluating the Robustness of the Association between CRC and XRCC1 Gene Polymorphisms

Figure 4.

Funnel Plot Analysis for Detecting Publication Bias in the Meta-Analysis of XRCC1 Gene Polymorphisms Associated with CRC

Discussion

The XRCC1 gene polymorphisms selected in this meta-analysis are non-synonymous (Arg194Trp, Arg280His, and Arg399Gln) which are established to affect DNA repair processes such as base-excision repair (BER) pathway in different ways. All of these polymorphism change protein structure in functionality critical domains of XRCC1 and may influence it’s activity in DNA damage responses. The Arg194Trp and Arg280His mutations are respectively located in N-terminal and BRCT (BRCA1 C Terminus) domains, leading to slight to moderate stability loss. While the Arg399Gln variant is located in the BRCT I domain which is an area essential for protein-protein interaction, and has been linked to a greater loss of XRCC1 function and severely disturbs DNA repair capacity [71]. Therefore, the Arg194Trp and Arg280His variants are seen to have slight decrease in DNA repair function and slightly increase cancer risk, while the Arg399Gln variant significantly impairs DNA repair function and significantly increases risk of cancer.

Colorectal cancer is a complex disease with polygenic etiology and is influenced by gene-gene and gene-environment interactions [72]. Besides host genetic factors determinants, the development and prognosis of colorectal cancer is influenced by other factors such as chronic inflammation, environmental factors, diet, lifestyle, and gut microbiota. Environmental factors such as smoking, poor diet, chronic inflammation and pollution tend to results in oxidative stress and inflammation, inducing DNA damage and tumorigenesis and colorectal cancer progression [73]. The genes and environmental factor interactions are turning out to be evident for CRC risk. For instance, a case-control study from Thailand demonstrated that individuals having certain XRCC1 polymorphisms had increased risk of CRC when combined with familial cancer history and high frequency of pork consumption [56]. Further, individuals carrying 399Gln allele who were habitual heavy smokers or drinkers are also found to have higher CRC risk [47]. Gene-gene interactions have also been known to influence the progression of HCC. Aflatoxin B1 (AFB1) exposure to rats under a vitamin A deficient diet has been shown to increase colon cancer incidence by 29% due to increased AFB1-DNA adduct levels [74]. This study demonstrates dietary influence on formation of DNA adducts and repairs proficiency. Furthermore, individuals with the 399Gln allele were more susceptible to developing detectable AFB1-DNA adducts [75].

The current study evaluated the combined data from 52 qualified case-control studies and evaluated the correlation between CRC and XRCC1 gene polymorphisms. Based on the meta-analysis, a significant correlation were seen between Arg399Gln variant and increased the risk of CRC. From the data it is seen that the other two polymorphisms (Arg194Trp and Arg280His) did not demonstrate a statistically significant correlation with the CRC risk. Subgroup analyses using ethnicity data, did not demonstrate a statistically significant correlation between the three variants (Arg194Trp, Arg280His, and Arg399Gln) and CRC risk. Although the overall results for Arg280His did not demonstrate heterogeneity, the Arg194Trp and Arg399Gin variants had significant heterogeneity. Sensitivity analyses revealed that the meta-analysis is robust, and absence of publication bias was observed for all three SNPs.

Several meta-analyses have examined the association between XRCC1 gene polymorphsism and CRC risk, but the results have been inconclusive. Two independent meta-analyses reported a protective effect of the 399Q allele in both recessive and homozygous models [76, 77]. However, Bin Wang et al. analyzed 14 studies on three XRCC1 variants (Arg399Gln, Arg280His, Arg194Trp) and found no significant association with CRC risk in the overall population and Asian and Caucasian subgroups [78]. A statistically significant increase in CRC risk for the Arg399Gln and Arg194Trp variants in Asian and Chinese populations, respectively, was documented in two separate meta-analyses [79, 80]. In contrast to this, XRCC1 R399Q showed no significant association with CRC in any genetic model in the Chinese Han population [81]. Larger meta-analyses have revealed ethnicity specific associations in Asian and Caucasian populations [82, 83]. On the other hand, a global meta-analysis of 61 variants in 26 DNA repair genes (BER, NER, and DRR pathways), including XRCC1, found several low-impact genetic variations on CRC risk, indicating the XRCC1’s role in CRC susceptibility. The results of the present meta-analysis are consistent with earlier studies, which reported association between XRCC1 polymorphisms in CRC risk [82, 83]. The inconsistencies in previous meta-analyses is mainly due to variations in the distribution of allele frequencies between ethnic groups, variability in sample size, and possible gene-environment interactions that were not equally controlled across studies. A study assessing CRC risk using a meta-analysis of 910 variants in 150 candidate genes found no significant association with XRCC1 gene polymorphisms. Despite its biological importance, XRCC1 was not included in the list of strong or moderate evidence groups due to a lack of consistent evidence [84].

This study has some limitations that need to be pointed out. First, the control groups of the independent studies might have included some undiagnosed CRC cases, leading to a potential selection bias. Second, we were unable to further assess the effects of other confounders such as age, gender, smoking, and alcohol consumption on CRC etiology. To conclude, the present meta-analysis revealed that XRCC1 Arg399Gln polymorphism is strongly associated with the susceptibility of CRC. As previous meta-analyses produced inconsistent results for the other two polymorphisms, along with disagreements in the literature, highlight the complexity of genetic factors in cancer risk. Large-scale studies involving environmental, lifestyle, and genetic data along with ethnically diverse cohorts and uniform control selection methods are needed in future studies to understand the role of XRCC1 variants in CRC etiology and to investigate their potential use as biomarkers for cancer risk stratification.

Author Contribution Statement

Conceptualization: Alam A, Sujatha P. LVKS B., Resources: Alam A, Sujatha P. LVKS B., Supervision: Alam A, Sujatha P. LVKS B., Data Collection: Praveen K. Writing-original draft: Praveen K., Writing-manuscript & editing: Praveen K, Mavillapalli RC and Ghanta MK. Approval of final manuscript: all authors.