Abstract
Background: China is a multinational country. The relationship between gene polymorphisms of xenobiotic metabolizing enzymes and national ethnicity has not previously investigated among Chinese people. The aim of this study was to investigate distributions of CYP1A1 and CYP2E1 gene polymorphisms in five ethnic groups of China. Methods: 829 blood samples were collected from five ethnic groups (Han, Shui, Miao, Zhuang, Bouyei). Taqman-MGB probe was used in Real-time PCR to test the gene polymorphisms of CYP1A1 (rs1048943 and rs4646903) and CYP2E1 (rs2031920 and rs6413420). We further validate the SNP genotyping results through DNA sequencing. Results: The genotype distribution of all four SNPs was in accordance with Hardy-Weinberg equilibrium except the genotype distribution of rs4646903 in Han and Bouyei ethnic groups (p=0.013 and 0.0005, respectively). CYP2E1 gene rs6413420 polymorphism was first found in the Bouyei ethnic group in China. The results of DNA sequencing were entirely in line with the SNP genotyping assay. Conclusions: The CYP1A1 and CYP2E1 genetic polymorphisms were different in different ethnic groups in China. CYP2E1 gene rs6413420 polymorphism was first found in the Bouyei ethnic group of China.
Keywords: CYP1A1, CYP2E1, Taqman-MGB probe, Real-time PCR, SNPs
Introduction
Cytochrome P450 enzymes (CYP450s) are important phase I xenobiotic metabolizing enzymes (XMEs). Most CYP450s are polymorphic, because of gene deletions, single nucleotide polymorphisms (SNPs), gene duplications and mutated alleles. CYP1A1 and CYP2E1 are two of the main cytochrome P450 isoforms involved in the metabolism of endogenous compounds and xenobiotics considered to be responsible for the development of several human diseases. The human enzyme CYP1A1 is the most active among the CYPs in metabolizing procarcinogens, particularly, the polycyclic aromatic hydrocarbons (PAHs), into highly reactive intermediates [1]. A functional role has been previously assigned to two nonsynonymous polymorphisms in the CYP1A1 gene. The first one is an adenine (A) to guanine (G) substitution at codon 462 in exon 7 (Ile462Val, rs1048943).The second one is a thymine (T) to cytosine (C) transition (rs4646903) [2]. Rs4646903 is a commonly studied SNP in the CYP1A1 which has been implied to associate with cancer risk [3]. The SNP located at nucleotide 3801 in the 3’ non-coding region containing a single T to C substitution that results in a polymorphic restriction site for the MspI enzyme (MspI or CYP1A1 *2A polymorphism, rs4646903). The MspI restriction site polymorphism results in three genotypes: a predominant homozygous m1 allele without the MspI site (type A, TT), the heterozygote (type B, TC) and a homozygous rare m2 allele with the MspI site (type C, CC) [4]. The CYP2E1 enzyme is responsible for the metabolism of alcohol and some tobacco carcinogens such as low-molecular weight nitrosamines [5-7]. The most extensively studied SNPs of CYP2E1 are RsaI/PstI site in the 5’ flanking region and the DraI site in intron 6 [8]. Two linked polymorphisms (CYP2E1 *5B) have been described in the CYP2E1 gene at nucleotides -1259 and -1019. They are located in the 5’ regulatory region and are detectable by RsaI or PstI restriction enzyme digestion [RsaI is 21053C > T (rs2031920), and PstI is 21293G > C (rs3813867), resp] [9,10].
TaqMan-MGB probe has the advantages of low fluorescence background, high resolution, strong hybridization specificity, good reproducibility, shorten probe length and low cost. It can be monitored in real-time and has no nonspecific diffusion phenomenon. It has become the internationally recognized method for detecting nucleic acids qualitatively and quantitatively.
Genetic susceptibility tends to be race-related, and this is due to the different races have different gene frequency. There have been some reports of CYP1A1 rs1048943, rs4646903 and CYP2E1 rs2031920, rs6413420 about gene frequency, but not for Chinese ethnic group. Therefore, we conducted SNPs classification experiment for CYP1A1 gene rs1048943, rs4646903 and CYP2E1 gene rs2031920, rs6413420 using TaqMan-MGB probe for the first time in different ethnic group in China.
Subjects and methods
Blood sample
829 blood samples were collected from health individuals of different ethnic groups from different provinces, including 193 from the Zhuang in Guangxi Province, 108 from the Han in Guangdong Province, 169 from the Shui, 179 from the Miao and 180 from the Bouyei ethnic group in Guizhou Province. There were no genetic relationships, no smoking and drinking histories and no hereditary diseases among these participants. This study protocol was reviewed and approved by the Department of Science and Technology of Shenzhen City and the local Ethics Committees.
DNA extraction and agarose gel electrophoresis (AGE)
We extracted DNA from the blood through three types of methods (standard phenol and chloroform, blood stain and QIGEN Mini Kit) according to the blood volume. Then we perform 1.6% AGE to observe the results. On the basis of DNA template extracted by these three methods, we conducted a PCR reaction to observe the difference, which was showed in 2% AGE.
TaqMan-MGB primers and probes
Each SNP was genotyped by using conventional TaqMan minor groove binding (MGB) probes, which were commercially supplied by Shanghai GeneCore Biotechnologies. TaqMan SNP genotyping was performed by Taq amplification. Each SNP genotype required two unlabeled PCR primers and two allele-specific probes. Each probe was doubly labeled with reporter dyes at the 5’ end. In the present study, the 5’ end of the two probes was labeled with FAM and VIC respectively. We designed the primers and probes of rs1048943 and rs4646903 in CYP1A1 and rs2031920 and rs6413420 in CYP2E1 through Primer Premier 5, and confirmed the specificity by BLAST. The base sequence showed on Table 1.
Table 1.
The TaqMan-MGB primer sequences and probe
| SNP site | Primer/probe | base sequence (5’-3’) | Product length |
|---|---|---|---|
| rs1048943 | primer | F: 5’-GGCAAGCGGAAGTGTATCG-3’ | 66 bp |
| R: 5’-CAGGATAGCCAGGAAGAGAAAGAC-3’ | |||
| probe | W: 5’-VIC- TGAGACCATTGCCC-MGB-3’ | ||
| M: 5’-FAM-TGAGACCGTTGCCC-MGB-3’ | |||
| rs4646903 | primer | F: 5’-GCACTGGTACCATTTTGTTTCACT-3’ | 67 bp |
| R: 5’-GCTGAGGTGGGAGAATCGT-3’ | |||
| probe | W: 5’-VIC- CACCTCCTGGGCTCA-MGB-3’ | ||
| M: 5’-FAM- ACCTCCCGGGCTCA-MGB-3’ | |||
| rs2031920 | primer | F: 5’-TGACTTTTATTTTCTTCATTTCTCATCATATTTTCTATTATACAT-3’ | 135 bp |
| R: 5’-GTTTTTCATTCTGTCTTCTAACTGGCAATAT-3’ | |||
| probe | W: 5’-VIC- AGGTTGCAATTTTGTACTTT-MGB-3’ | ||
| M: 5’-FAM- AGGTTGCAATTTTATACTTT-MGB-3’ | |||
| rs6413420 | primer | F: 5’-ATTTGGGATAGACGAGTAGCA-3’ | 97 bp |
| R: 5’-GAGACAATCCTGTGGAAACG-3’ | |||
| probe | W: 5’-VIC-TCACCCTCCTTCTCAGAACACATTATAAAA-MGB-3’ | ||
| M: 5’-FAM-TCACCCTCCTTCTCATAACACATTATAAAA-MGB-3’ |
Real-time PCR for SNPs
The reactions were perormed in 5 μL, using 2.5 μL of TaqMan Master Mix, and 6.25 nmol/L of primer, 18 nmol/L of probe and 20-300 ng of DNA template. The reactions were performed under 40 Cycling Standard Conditions, showed in Table 2. FAM and VIC were selected as florescence labeling perssad, which had similar wavelength. FAM was for wild type probe, while VIC was for mutant type probe.
Table 2.
The reactive condition of Real-time PCR
| SNP site | reactive condition |
|---|---|
| rs1048943 | 95°C pretreatment for 20 s, 95°C degeneration for 15 s, 56°C anneal for 20 s, 60°C extend and collect florescence for 34 s |
| rs4646903 | 95°C pretreatment for 20 s, 95°C degeneration for 15 s, 60°C anneal, extend and collect florescence for 34 s |
| rs2031920 | 95°C pretreatment for 20 s, 95°C degeneration for 20 s, 60°C anneal, extend and collect florescence for 34 s |
| rs6413420 | 95°C pretreatment for 20 s, 95°C degeneration for 15 s, 60°C anneal, extend and collect fluorescence for 34 s |
Sequence validation
To verify the reliability of the results from Real-time PCR SNPs experiment, we conduct a PCR amplified reaction to the sequence primer. For rs1048943 polymorphism, the primers were: forward: 5’- CTGCTTGCCTGTCCTCTA-3’, reverse: 5’-CAGCCC-AGATAGCAAAACT-3’. The length of target fragment was 522 bp. For rs2031920 polymorphism, the primers were: forward: 5’-CAAGT-GATTTGGCTGGATTG-3’, reverse: 5’-ACAGACCC-TCTTCCACCTTCT-3’. The length of target fragment was 243 bp. For rs6413420 polymorphism, the primers were: forward: 5’-CCGTT-GTCTAACCAGTGCC-3’, reverse: 5’-TGATGGGAA-GCGGGAAA-3’. The length of target fragment was 486 bp. Rs4646903 sequencing was using general primers of TaKaRa PMD-20T Vector.
The reaction product was detected by 2% AGE. The target stripe was cut off and purified by QIAquick PCR Purification Kit. The purified product was bi-directional sequenced using up and down primer. The results of sequence were compared with the corresponding DNA sequence of SNP site. If a doublet was appeared, it was heterozygote; if a simple spike appeared, it was wild type or mutation in the homozygous type.
Statistical analysis
Differences in the allele and genotype frequencies of rs1048943, rs4646903, rs2031920 and rs6413420 among different ethnic groups were calculated using a χ2 test. The χ2 test was used to test for deviation of genotype distribution from the Hardy-Weinberg law of genetic equilibrium. Descriptive statistical analysis was performed using SPSS Statistics version 13.0. Differences were considered to be statically significant when p < 0.05.
Results
The results of DNA extracted by standard phenol and chloroform, blood stain and QIGEN Mini Kit
In this study, we adopted three methods (standard phenol and chloroform, blood stain and QIGEN Mini Kit) to extract DNA from blood. The stripe which was extracted by QIGEN Mini Kit was better than the standard phenol and chloroform, blood stain, showed in Figure 1.
Figure 1.
Agarose gel (1.6%) Electrophoresis of DNA extracted by standard phenol and chloroform, blood stain and QIGEN Mini Kit. Lane 1, 8: DNA markers; Lane 2, 3: Blood stain method; Lane 4, 5: Standard phenol and chloroform method; Lane 6, 7: QIGEN Mini Kit method.
We took DNA extracted by standard phenol and chloroform, blood stain and QIGEN Mini Kit as template, and conducted a Real-time PCR SNPs experiment to compare the difference among these three methods, showed in Figure 2. We can see the AGE results of PCR product of 4 SNPs site extracted by three methods was the same. The PCR product of rs1048943 was at 66 bp, and rs4646903 at 67 bp, rs2031920 at 135 bp, rs1048943 at 97 bp.
Figure 2.
PCR products of rs1048943, rs4646903, rs2031920 and rs6413420 by agarose gel (2%) Electrophoresis. Lane 1, 8: DNA markers; Lane 2, 5, 9, 10, 13: Results of blood stain; Lane 3, 6, 11, 14: Results of standard phenol and chloroform; Lane 4, 7, 12, 15: Results of QIGEN Mini Kit. Lane 2, 3, 4: Stands for rs1048943; Lane 5, 6 7: Stands for rs4646903; Lane 9, 10, 11, 12: Stands for rs2031920; Lane 13, 14, 15: Stands for rs6413420.
CYP1A1 (rs1048943 and rs4646903) genotyping
We detected genotype and allele gene frequency of CYP1A1 gene 1048943 and 4646903 in 829 samples of five ethnic groups. In CYP1A1 gene 1048943, the genotype distribution of five ethnic groups was conformed to Hardy-Weinberg genetic equilibrium law, as shown in Table 3. There was statistical significance between the Zhuang ethnic group and other four ethnic groups. In CYP1A1 gene 4646903, only the genotype distribution of the Shui, Miao, and Zhuang ethnic groups was accord with the Hardy-Weinberg genetic equilibrium law, as shown in Table 4. There was statistical significance between the Zhuang and Han ethnic group (χ2=9.40, p=0.009), the Zhuang and Bouyei ethnic group (χ2=7.77, p=0.021), the Zhuang and Miao ethnic group (χ2=15.66, p < 0.001).
Table 3.
The genotype and allele frequency of rs1048943 in five ethnic groups
| ethnic group | sample size | genotype | Actualnumber (theoretical number) | Frequency (%) | Allele | Frequency (%) | χ2 (p) |
|---|---|---|---|---|---|---|---|
| Han | 108 | A/A | 61 (62.3) | 56.5 | A | 75.9 | 0.44 (0.51) |
| A/G | 42 (39.5) | 38.9 | G | 24.1 | |||
| G/G | 5 (6.3) | 4.6 | |||||
| Zhuang | 193 | A/A | 85 (81) | 44.0 | A | 64.8 | 1.63 (0.20) |
| A/G | 80 (88.1) | 41.5 | G | 35.2 | |||
| G/G | 28 (24.0) | 14.5 | |||||
| Shui | 169 | A/A | 102 (100.0) | 60.4 | A | 76.9 | 0.75 (0.39) |
| A/G | 56 (60.0) | 33.1 | G | 23.1 | |||
| G/G | 11 (9.0) | 6.5 | |||||
| Miao | 179 | A/A | 110 (107.9) | 61.5 | A | 77.7 | 0.79 (0.37) |
| A/G | 58 (62.1) | 32.4 | G | 22.3 | |||
| G/G | 11 (8.9) | 6.1 | |||||
| Bouyei | 180 | A/A | 113 (109.7) | 68.9 | A | 78.1 | 2.10 (0.15) |
| A/G | 55 (61.7) | 25.4 | G | 21.9 | |||
| G/G | 12 (8.7) | 5.7 |
Table 4.
The genotype and allele frequency of rs4646903 in five ethnic groups
| ethnic group | sample size | genotype | Actual number (theoretical number) | Frequency (%) | Allele | Frequency (%) | χ2 (p) |
|---|---|---|---|---|---|---|---|
| Han | 108 | T/T | 47 (40.9) | 43.5 | T | 61.6 | 6.60 (0.013*) |
| T/C | 39 (51.1) | 36.1 | C | 38.4 | |||
| C/C | 22 (15.9) | 20.4 | |||||
| Zhuang | 193 | T/T | 51 (45.8) | 26.4 | T | 48.7 | 2.25 (0.13) |
| T/C | 86 (96.4) | 44.6 | C | 51.2 | |||
| C/C | 56 (50.8) | 29.0 | |||||
| Shui | 169 | T/T | 58 (56.3) | 34.3 | T | 57.7 | 0.30 (0.58) |
| T/C | 79 (82.5) | 46.7 | C | 42.3 | |||
| C/C | 32 (30.3) | 19.0 | |||||
| Miao | 179 | T/T | 77 (73.2) | 43.0 | T | 64.0 | 1.49 (0.22) |
| T/C | 75 (82.5) | 41.9 | C | 36.0 | |||
| C/C | 27 (23.2) | 15.1 | |||||
| Bouyei | 180 | T/T | 72 (60.7) | 40.0 | T | 58.1 | 12.03 (0.0005*) |
| T/C | 65 (87.7) | 36.1 | C | 41.9 | |||
| C/C | 43 (31.7) | 23.9 |
CYP2E1 (rs2031920 and rs6413420) genotyping
In CYP2E1 gene 2031920, the genotype distribution of five ethnic groups was conformed to Hardy-Weinberg genetic equilibrium law, as shown in Table 5. There was statistical significance between the Miao and Bouyei ethnic group (χ2=6.53, p=0.038), the Miao and Shui ethnic group (χ2=6.13, p=0.047). Interestingly, we found only the Buoyei ethnic group had the SNP site of CYP2E1 gene 6413420. The frequency of the gene was 1.4%, as shown in Table 6.
Table 5.
The genotype and allele frequency of rs2031920 in five ethnic groups
| ethnic group | sample size | genotype | Actual number (theoretical number) | Frequency (%) | Allele | Frequency (%) | χ2 (p) |
|---|---|---|---|---|---|---|---|
| Han | 108 | C/C | 69 (66.1) | 63.9 | C | 78.2 | 2.66 (0.10) |
| C/T | 31 (36.8) | 28.7 | T | 22.8 | |||
| T/T | 8 (5.1) | 8.4 | |||||
| Zhuang | 193 | C/C | 123 (124.5) | 63.7 | C | 80.3 | 0.46 (0.50) |
| C/T | 64 (61.0) | 33.2 | T | 19.7 | |||
| T/T | 6 (7.5) | 3.1 | |||||
| Shui | 169 | C/C | 106 (107.4) | 62.7 | C | 80.2 | 0.41 (0.52) |
| C/T | 59 (56.3) | 34.9 | T | 19.8 | |||
| T/T | 4 (7.4) | 2.4 | |||||
| Miao | 179 | C/C | 107 (102.6) | 59.8 | C | 75.7 | 3.24 (0.07) |
| C/T | 57 (65.9) | 31.8 | T | 24.3 | |||
| T/T | 15 (10.6) | 8.4 | |||||
| Bouyei | 180 | C/C | 127 (125.8) | 70.6 | C | 83.6 | 0.40 (0.53) |
| C/T | 47 (49.3) | 26.1 | T | 16.4 | |||
| T/T | 6 (4.8) | 3.3 |
Table 6.
The genotype and allele frequency of rs6413420 in five ethnic groups
| ethnic group | sample size | genotype | Actual number (theoretical number) | Frequency (%) | Allele | Frequency (%) |
|---|---|---|---|---|---|---|
| Han | 108 | G/G | 108 | 100 | G | 100 |
| G/T | 0 | 0 | T | 0 | ||
| T/T | 0 | 0 | ||||
| Zhuang | 193 | G/G | 193 | 100 | G | 100 |
| G/T | 0 | 0 | T | 0 | ||
| T/T | 0 | 0 | ||||
| Shui | 169 | G/G | 169 | 100 | G | 100 |
| G/T | 0 | 0 | T | 0 | ||
| T/T | 0 | 0 | ||||
| Miao | 179 | G/G | 178 | 99.4 | G | 99.7 |
| G/T | 1 | 0.6 | T | 0.3 | ||
| T/T | 0 | 0 | ||||
| Bouyei | 180 | G/G | 175 | 97.2 | G | 98.6 |
| G/T | 5 | 2.8 | T | 1.4 | ||
| T/T | 0 | 0 |
Sequence validation
To verify the reliability of the results of Real-time PCR SNPs experiment, we conduct a PCR amplified reaction to the sequence primer. Taken rs4646903 for example, we randomly selected a DNA sample of CYP1A1 gene 4646903 which had wild type (W/M), heterozygosis genotype (W/M) and homozygosis mutant genotype (M/M), and conduct a PCR amplified reaction to the sequence primer. The reaction product was detected by 2% AGE. The stripe located at between 50 bp and 100 bp, which was conformed to 67 bp target stripe, showed in Figure 3. The results of sequence validation of rs1048943, rs2031920 and rs6413420 were displayed in Supplementary materials.
Figure 3.
PCR products of CYP1A1 gene 4646903 by agarose gel (2%) Electrophoresis. Lane M Represents 100 bp DNA Molecular Weight Markers.
The sequence results of W/W genotype of rs4646903 showed that No.69 bp on the forward direction was T, and the peak was singlet. We also validated on reverse direction. No.115 bp was A, and the map also was unimodal. So it was with W/M and M/M, showed in Figure 4. The sequence analysis results were consistent with Real-time PCR, which indicated that studying genetic polymorphism using Tapman-MGB technology was reliable.
Figure 4.
Sequencing analysis of CYP1A1 gene 4646903. Red arrow was rs4646903 site. A, B: Sequencing results of W/W; C, D: Sequencing results of W/M; E, F: Sequencing results of M/M. A, C, E: Positive-sense strand; B, D, F: Antisense strand.
Discussion
China is a multinational state, including the Han ethnic group and other 55 minorities. Different ethnic groups have different origin and genetic background. And this feature is quite different with other countries. So it is necessary to investigate the distribution of gene frequency and genotype among 56 ethnic groups in our country.
Now repercussion study of gene and environment is most focused on phase I, II exogenous metabolic enzymes [11]. The enzyme activity and balance relationship among them determines the susceptibility of different crowd to disease. CYP1A1 is an important phase I metabolic enzymes. Polycyclic aromatic hydrocarbons (PAHs) in tobacco and occupational environment can induce the expression of CYP1A1 gene. Nowadays, there are mainly four SNPs in research of CYP1A1 gene, which are rs1048943, rs4646903, rs4986883 and rs1799814. Rs1048943 locates at Exon 7. A-G exchange takes place on No.4889 bp, so the Ile is instead by Val on No.462 amino acid at ferroheme combination zone of the protein. There were some reports indicated that the polymorphism of rs1048943 could cause inducibility of enzymes and enhancement of biological activated ability and is associated with a variety of disease [12]. Another rs4646903 located at 246th bases at the downstream of the 3’ end. T changed to C, formed MspI site, which enhanced catalytic activity [13] and was associated with hydrophobic DNA adduct [14,15].
In this study, we detected SNPs of CYP1A1 gene 1048943 and 4646903 in 829 samples of five ethnic groups, which were the Han ethnic groups, the Bouyei, the Shui, the Miao and the Zhuang ethnic groups. In CYP1A1 gene 1048943, the genotype distribution of five ethnic groups was conformed to Hardy-Weinberg genetic equilibrium law. The gene frequency of five ethnic groups (W: 0.648-0.781; M: 0.219-0.352) was close to Japanese [16] and Indian [17], lower than American [18] and European [19,20], but had larger difference with Saudi Arabian [21]. The gene frequency of rs4646903 in five ethnic groups (W: 0.640-0.687; M: 0.360-0.512) was close to Indian [22], but lower than American [18], European [19,20], and Saudi Arabian [21].
Like most other metabolic enzymes, the gene frequency of CYP2E1 was different among different ethnic and racial. There were mainly five SNPs in research of CYP2E1 gene, that were rs2031920, rs6413432, rs6413419, rs6413420 and rs3813867. Rs2031920 and rs6413420 were both located in the 5’ end. The mutations of the former site created disappear of RsaI site. The polymorphism of RsaI site can significantly affect the transcription level of CYP2E1 gene [23,24]. The latter could increase gene transcription activity [25].
In our research, we found that the genotype distribution of rs2031920 in five ethnic groups was conformed to Hardy-Weinberg genetic equilibrium law. The frequency of M gene in the Miao ethnic group, the Han, the Shui, the Zhuang and the Bouyei ethnic group was 24.3%, 22.8%, 19.8%, 19.7% and 16.4%, respectively. The gene frequency of rs2031920 in five ethnic groups (W: 0.757-0.836; M: 0.164-0.243) was close to Japanese [16], but lower than American [26] and European [20,27]. Interestingly, we found only the Bouyei ethnic group existed the SNPs site of rs6413420. This was the first time found the site in Chinese. The gene frequency was lower than German [20], Norwegians [28] and Turks [29].
In our study, we validate the SNPs classification results using Taqman-MGB probe by designing and compounding sequencing primers of CYP1A1 gene rs1048943, CYP2E1 gene rs2031920 and rs6413420. CYP1A1 gene rs4646903 was validated by molecular cloning methods because of multiple repeat fragments near this site. The sequencing results of the present study were in complete accord with the SNPs classification results, which verify the reliability of the experimental system.
In summary, the CYP1A1 and CYP2E1 genetic polymorphism were different in different places as well as different ethnic groups in China. CYP2E1 gene rs6413420 polymorphism was first found in the Bouyei ethnic group of China. These results can not only understand the genetic relationship among various ethnic groups and the ethnic origin, but also predict the risk of SNPs site related disease of different ethnic groups.
Acknowledgements
This work was financially supported by the Upgrade Scheme of the Shenzhen Municipal Key Laboratory (CXB201104220031A, JCYJ20130401102255980). We are grateful to all participants of this study.
Disclosure of conflict of interest
None.
Supporting Information
References
- 1.Roberts-Thomson SJ, McManus ME, Tukey RH, Gonzalez FF, Holder GM. The catalytic activity of four expressed human cytochrome P450s towards benzo[a] pyrene and the isomers of its proximate carcinogen. Biochem Biophys Res Commun. 1993;192:1373–9. doi: 10.1006/bbrc.1993.1568. [DOI] [PubMed] [Google Scholar]
- 2.Kawajiri K, Eguchi H, Nakachi K, Sekiya T, Yamamoto M. Association of CYP1A1 germ li-ne polymorphisms with mutations of the p53 gene in lung cancer. Cancer Res. 1996;56:72–6. [PubMed] [Google Scholar]
- 3.Zhuo W, Zhang L, Qiu Z, Zhu B, Chen Z. Does cytochrome P450 1A1 MspI polymorphism increase acute lymphoblastic leukemia risk? Evidence from 2013 cases and 2903 controls. Gene. 2012;510:14–21. doi: 10.1016/j.gene.2012.08.042. [DOI] [PubMed] [Google Scholar]
- 4.Zhou SF, Liu JP, Chowbay B. Polymorphism of human cytochrome P450 enzymes and its clinical impact. Drug Metab Rev. 2009;41:89–295. doi: 10.1080/03602530902843483. [DOI] [PubMed] [Google Scholar]
- 5.Hecht SS. Biochemistry, biology, and carcinogenicity of tobacco-specific N-nitrosamines. Chem Res Toxicol. 1998;11:559–603. doi: 10.1021/tx980005y. [DOI] [PubMed] [Google Scholar]
- 6.Nebert DW, Menon AG. Pharmacogenomics, ethnicity, and susceptibility genes. Pharmacogenomics J. 2001;1:19–22. doi: 10.1038/sj.tpj.6500002. [DOI] [PubMed] [Google Scholar]
- 7.Chen YC, Hunter DJ. Molecular epidemiology of cancer. CA Cancer J Clin. 2005;55:45–54. doi: 10.3322/canjclin.55.1.45. [DOI] [PubMed] [Google Scholar]
- 8.Liu Y, Meng XW, Zhou LY, Zhang PY, Sun X, Zhang P. Genetic polymorphism and mRNA levels of cytochrome P450IIE1 and glutathione S-transferase P1 in patients with alcoholic liver disease in different nationalities. Hepatobiliary Pancreat Dis Int. 2009;8:162–7. [PubMed] [Google Scholar]
- 9.Hayashi S, Watanabe J, Kawajiri K. Genetic polymorphisms in the 5N-flanking region change transcriptional regulation of the human cytochrome P450IIE1 gene. J Biochem. 1991;110:559–65. doi: 10.1093/oxfordjournals.jbchem.a123619. [DOI] [PubMed] [Google Scholar]
- 10.Ruwali M, Khan AJ, Shah PP, Singh AP, Pant MC, Parmar D. Cytochrome P450 2E1 and head and neck cancer: interaction with genetic and environmental risk factors. Environ Mol Mutagen. 2009;50:473–82. doi: 10.1002/em.20488. [DOI] [PubMed] [Google Scholar]
- 11.Brennan P, Boffetta P. Mechanistic considerations in the molecular epidemiology of head and neck cancer. IARC Sci Publ. 2004;157:393–414. [PubMed] [Google Scholar]
- 12.Kawajiri K, Nakachi K, Imai K, Watanabe J, Hayashi S. The CYP1A1 gene and cancer susceptibility. Crit Rev Oncol Hematol. 1993;14:77–87. doi: 10.1016/1040-8428(93)90007-q. [DOI] [PubMed] [Google Scholar]
- 13.Landi MT, Bertazzi PA, Shields PG, Clark G, Lucier GW, Garte SJ, Cosma G, Caporaso NE. Association between CYP1A1 genotype, mRNA expression and enzymatic activity in humans. Pharmacogenetics. 1994;4:242–6. doi: 10.1097/00008571-199410000-00002. [DOI] [PubMed] [Google Scholar]
- 14.Alexandrov K, Cascorbi I, Rojas M, Bouvier G, Kriek E, Bartsch H. CYP1A1 and GSTM1 genotypes affect benzo[a] pyrene DNA adducts in smokers’ lung: comparison with aromatic/hydrophobic adduct formation. Carcinogenesis. 2002;23:1969–77. doi: 10.1093/carcin/23.12.1969. [DOI] [PubMed] [Google Scholar]
- 15.Lodovici M, Luceri C, Guglielmi F, Bacci C, Akpan V, Fonnesu ML, Boddi V, Dolara P. Benzo(a)pyrene diolepoxide (BPDE)-DNA adduct levels in leukocytes of smokers in relation to polymorphism of CYP1A1, GSTM1, GSTP1, GSTT1, and mEH. Cancer Epidemiol Biomarkers Prev. 2004;13:1342–8. [PubMed] [Google Scholar]
- 16.Sugimura T, Kumimoto H, Tohnai I, Fukui T, Matsuo K, Tsurusako S, Mitsudo K, Ueda M, Tajima K, Ishizaki K. Gene-environment interaction involved in oral carcinogenesis: molecular epidemiological study for metabolic and DNA repair gene polymorphisms. J Oral Pathol Med. 2006;35:11–8. doi: 10.1111/j.1600-0714.2005.00364.x. [DOI] [PubMed] [Google Scholar]
- 17.Sam SS, Thomas V, Reddy SK, Surianarayanan G, Chandrasekaran A. CYP1A1 polymorphisms and the risk of upper aerodigestive tract cancers in an Indian population. Head Neck. 2008;30:1566–74. doi: 10.1002/hed.20897. [DOI] [PubMed] [Google Scholar]
- 18.Hirata H, Hinoda Y, Okayama N, Suehiro Y, Kawamoto K, Kikuno N, Rabban JT, Chen LM, Dahiya R. CYP1A1, SULT1A1, and SULT1E1 polymorphisms are risk factors for endometrial cancer susceptibility. Cancer. 2008;112:1964–73. doi: 10.1002/cncr.23392. [DOI] [PubMed] [Google Scholar]
- 19.Little J, Sharp L, Masson LF, Brockton NT, Cotton SC, Haites NE, Cassidy J. Colorectal cancer and genetic polymorphisms of CYP1A1, GSTM1 and GSTT1: a case-control study in the Grampian region of Scotland. Int J Cancer. 2006;119:2155–64. doi: 10.1002/ijc.22093. [DOI] [PubMed] [Google Scholar]
- 20.Harth V, Schafer M, Abel J, Maintz L, Neuhaus T, Besuden M, Primke R, Wilkesmann A, Thier R, Vetter H, Ko YD, Bruning T, Bolt HM, Ickstadt K. Head and neck squamous-cell cancer and its association with polymorphic enzymes of xenobiotic metabolism and repair. J Toxicol Environ Health A. 2008;71:887–97. doi: 10.1080/15287390801988160. [DOI] [PubMed] [Google Scholar]
- 21.Al-Dayel F, Al-Rasheed M, Ibrahim M, Bu R, Bavi P, Abubaker J, Al-Jomah N, Mohamed GH, Moorji A, Uddin S, Siraj AK, Al-Kuraya K. Polymorphisms of drug-metabolizing enzymes CYP1A1, GSTT and GSTP contribute to the development of diffuse large B-cell lymphoma risk in the Saudi Arabian population. Leuk Lymphoma. 2008;49:122–9. doi: 10.1080/10428190701704605. [DOI] [PubMed] [Google Scholar]
- 22.Pandey SN, Choudhuri G, Mittal B. Association of CYP1A1 Msp1 polymorphism with tobacco-related risk of gallbladder cancer in a north Indian population. Eur J Cancer Prev. 2008;17:77–81. doi: 10.1097/CEJ.0b013e3282b6fdd2. [DOI] [PubMed] [Google Scholar]
- 23.Yu MW, Gladek-Yarborough A, Chiamprasert S, Santella RM, Liaw YF, Chen CJ. Cytochrome P450 2E1 and glutathione S-transferase M1 polymorphisms and susceptibility to hepatocellular carcinoma. Gastroenterology. 1995;109:1266–73. doi: 10.1016/0016-5085(95)90587-1. [DOI] [PubMed] [Google Scholar]
- 24.Persson I, Johansson I, Lou YC, Yue QY, Duan LS, Bertilsson L, Ingelman-Sundberg M. Genetic polymorphism of xenobiotic metabolizing enzymes among Chinese lung cancer patients. Int J Cancer. 1999;81:325–9. doi: 10.1002/(sici)1097-0215(19990505)81:3<325::aid-ijc2>3.0.co;2-s. [DOI] [PubMed] [Google Scholar]
- 25.Fairbrother KS, Grove J, de Waziers I, Steimel DT, Day CP, Crespi CL, Daly AK. Detection and characterization of novel polymorphisms in the CYP2E1 gene. Pharmacogenetics. 1998;8:543–52. doi: 10.1097/00008571-199812000-00011. [DOI] [PubMed] [Google Scholar]
- 26.Rossini A, lima SS, Rapozo DC, Faria M, Albano RM, Pinto LF. CYP2A6 and CYP2E1 polymorphisms in a Brazilian population living in Rio de Janeiro. Braz J Med Biol Res. 2006;39:195–201. doi: 10.1590/s0100-879x2006000200005. [DOI] [PubMed] [Google Scholar]
- 27.Kúry S, Buecher B, Robiou-du-Pont S, Scoul C, Sébille V, Colman H, Le Houérou C, Le Neel T, Bourdon J, Faroux R, Ollivry J, Lafraise B, Chupin LD, Bézieau S. Combinations of cytochrome P450 gene polymorphisms enhancing the risk for sporadic colorectal cancer related to red meat consumptions. Cancer Epidemiol Biomarkers Prev. 2007;16:1460–7. doi: 10.1158/1055-9965.EPI-07-0236. [DOI] [PubMed] [Google Scholar]
- 28.Zienolddiny S, Campa D, Lind H, Ryberg D, Skaug V, Stangeland LB, Canzian F, Haugen A. A comprehensive analysis of phase I and phase II metabolism gene polymorphisms and risk of non-small cell lung cancer in smokers. Carcinogenesis. 2008;29:1164–9. doi: 10.1093/carcin/bgn020. [DOI] [PubMed] [Google Scholar]
- 29.Ulusoy G, Arinç E, Adali O. Genotype and allele frequencies of polymorphic CYP2E1 in the Turkish population. Arch Toxicol. 2007;81:711–8. doi: 10.1007/s00204-007-0200-y. [DOI] [PubMed] [Google Scholar]
Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.