Gene-environment and gene-gene interactions between CHRNA3 rs1051730, XRCC1 rs25487, and ERCC1 rs735482 variants highly elevate the risk of lung cancer
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Gene-gene and gene-environment interactions play an important role in cancer susceptibility. In this work, we studied the association of XRCC1 rs25487, ERCC1 rs735482, and CHRNA3 rs1051730 variants with lung cancer and assessed the modulatory effect of potential interaction between these variants on disease risk.
In this study, 86 primary lung cancer patients and 64 control subjects were genotyped for CHRNA3 rs1051730, XRCC1 rs25487, and ERCC1 rs735482 by real-time PCR. The frequency of the three studied variants was higher among lung cancer patients than in control subjects, but with no statistical significance. ERCC1 rs735482 variant was associated with 6.9-fold increased risk to develop lung cancer among smokers (p = 0.03). Concomitant presence of CHRNA3 and ERCC1 wild alleles was associated with 2.7-fold elevated risk of lung cancer (p < 0.0001), while concomitant presence of CHRNA3 rs1051730 variant allele with ERCC1 wild allele was associated with 20-fold elevated risk (p < 0.000). Concomitant presence of both variants, ERCC1 rs735482 and CHRNA3 rs1051730, was associated with 9.9-fold elevated risk (p < 0.0001). Meanwhile, the concomitant presence of XRCC1 rs25487 with either ERCC1 rs735482 or CHRNA3 rs1051730 or both was not associated with increased risk of the disease.
Our results emphasize the role of gene-gene interaction in the pathogenesis of lung cancer. Large-scale further studies to clarify the underlying mechanisms are needed.
KeywordsLung cancer Smoking XRCC1 ERCC1 CHRNA3 Polymorphism
Base excision repair
Cholinergic receptor nicotinicα3
Cigarette per day
Double strand breaks
Excision repair cross complementing group 1
Genome-wide association studies
Inter strand crosslinks
Nicotinic acetylcholine receptor subunits
Nucleotide excision repair
Non-small cell lung cancer
Small cell lung cancer
Single-stranded break repair
X-ray repair cross-complementing group 1
Lung cancer is a leading cause of death with a poor survival rate worldwide . Although smoking is the main cause of lung cancer, yet it cannot fully elucidate the epidemiologic incidences of disease among nonsmokers . Gene-gene and gene-environment interactions are currently believed to play a major role in individual’s susceptibility to lung cancer [3, 4].
Polymorphisms of DNA repair genes have been reported as potential markers for disease susceptibility and prognosis . Subjects with low expression and/or activity of DNA repair enzymes have impaired ability to remove tobacco-induced DNA damage and are more likely to develop lung cancer. Excision repair cross complementing group 1 (ERCC1) and X-ray repair cross-complementing group 1 (XRCC1) enzymes are needed to clear DNA damage and have been highlighted as potential biomarkers of clinical outcome in cancer [6, 7, 8, 9, 10].
XRCC1 gene is involved in base excision repair (BER) and single-stranded break repair (SSBR)  and helps in removing oxidative DNA damage induced by exposures to ionizing radiation or alkylating agents . XRCC1 rs25487 variant is a single-nucleotide polymorphism resulting from a nucleotide substitution at codon 399 with an amino acid change from arginine (Arg) to glutamine (Gln) and has been associated with an altered DNA repair activity . Previous studies on this variant and its role in susceptibility to lung cancer gave inconsistent results among different ethnic groups [14, 15, 16, 17].
On the other hand, ERCC1 protein functions in nucleotide excision repair (NER) and DNA inter strand crosslinks (ICL) repair pathways; therefore, it was hypothesized that polymorphisms which alter the expression and/or function of ERCC1 may play a role in cancer pathogenesis [18, 19, 20].
Also, cholinergic receptor nicotinic α3 (CHRNA3) gene coding for nicotinic acetylcholine receptor subunits (nAChRs) harbors another candidate variant, rs1051730 that has been associated with elevated risk of lung cancer in genome-wide association studies (GWAS) [21, 22].
In this study, we aim to examine the association of XRCC1 rs25487, ERCC1 rs735482, and CHRNA3 rs1051730 variants with lung cancer and to assess the modulatory effect of the potential interaction between these variants on disease risk in Egyptian patients.
This study is a case-control study that included 86 unrelated adult patients with primary lung cancer and 64 apparently healthy unrelated controls. Patients were presented to the Chest Diseases clinic of the National Research Center (NRC) from different governorates of Egypt. All subjects gave written informed consent and the study was approved by the local ethics committee. Medical history was obtained from all participants via questionnaire including demographic data, smoking and occupational history, as well as family history of malignancy. Thorough clinical examination and chest radiography were conducted. Exclusion criteria were pulmonary fibrosis, pneumonia, and any anti-cancer medication.
Genomic DNA was extracted from whole peripheral blood using QIAamp DNA extraction kit (Qiagen Hilden, Germany, Cat No. 51304) according to the manufacturer’s protocol. XRCC1 rs25487, ERCC1 rs735482, and CHRNA3 rs1051730 variants were genotyped using TaqMan® SNP Genotyping Assays. All primers and probes were designed by Applied Biosystems (Foster City, CA, USA) and genotyping analyses were performed on ABI 7500 real-time PCR system (Applied Biosystems) according to the manufacturer’s protocol. Negative controls were included in all assays and 10% of samples were randomly selected and analyzed in duplicates and the concordance rate was 100%.
Data were analyzed using IBM SPSS version 20.0 software (Statistical Package for Social Science). Quantitative data were expressed as mean values ± standard deviation (SD) and qualitative data were expressed as frequency (%). Normally distributed data were compared using Student’s t test. The significance of differences between proportions was tested by the Chi-square test (χ2). Differences were considered significant with p value < 0.05. Genotype and allele frequencies between groups were compared by Chi-square test. Univariate logistic regression analysis was used to test the association between studied polymorphisms and diseases and were presented as unadjusted odds ratios (OR) with confidence interval (95% CI).
General characteristics of the studied lung cancer patients and control subjects
Lung cancer (N = 86)
Controls (N = 64)
OR (95% CI)/P
Mean ± SD (Range)
54.2 ± 10.5 (27–75)
50.2 ± 8.5 (37–70)
< 45 year n (%)
≥ 45 year n (%)
Male n (%)
6.4 (2.2–18.1)/< 0.001*
Female n (%)
Histological type n (%)
Squamous cell carcinoma
Non-smokers n (%)
Smoker n (%)
Genotypes and alleles frequencies of the studied SNP in lung cancer patients and control subjects
Lung cancer patients (n = 86)
Controls (n = 64)
p value = 0.36
p value = 0.43
p value = 0.09
p value = 0.6
p value = 0.1
p value = 0.8
Association of studied SNPs with lung cancer under different genetic models of inheritance
(A/G + A/A vs. G/G)
(A/G vs. G/G) or (A/G vs. AA)
(A/G + G/G vs. A/A)
A/G vs. G/G +A/A
0.8 (0.3–2.4)/1.3 (0.3–5.1)
(A/C + C/C vs. A/A)
(A/C vs. A/A or C/C)
A/C + A/A vs. C/C
A/C vs. A/A + C/C
(A/G + GG vs. AA)
(A/G vs. A/A or G/G)
A/G + A/A vs. G/G
A/G vs. A/A + G/G
2.0 (0.7–5.3)/1.3 (0.2–6.7)
Genotypes frequency in different histological types of lung cancer
Histological type of lung cancer
Small cell lung cancer (n = 12)
Non-small cell lung cancer (n = 74)
Association between different genotypes and lung cancer in respect to smoking status
A/A vs. GG
A/C vs. A/A
C/C vs. A/A
A/G vs. A/A
G/G vs. A/A
Gene-gene interaction in lung cancer patients
OR (95% CI)
rs1051730 with rs735482
rs1051730 with rs25487
rs25487 with rs735482
In this work, we studied the association of XRCC1 rs25487, ERCC1 rs735482, and CHRNA3 rs1051730 variants with lung cancer and assessed the modulatory effect of the potential interaction between these variants on disease risk.
To our knowledge, this is the first work to study the three variants together in lung cancer patients. Our results showed higher frequency of the three studied variants among lung cancer patients but with no statistical significance. ERCC1 rs735482 variant was associated with 6.9-fold increased risk to develop lung cancer among smokers emphasizing the role of gene-environment interaction. We demonstrated for the first time that concomitant presence of CHRNA3 and ERCC1 wild alleles was associated with 2.7-fold elevated risk of lung cancer, while concomitant presence of CHRNA3 rs1051730 variant allele with ERCC1 wild allele was associated with 20-fold elevated risk. In addition, concomitant presence of both variants, ERCC1 rs735482 and CHRNA3 rs1051730, was associated with 9.9-fold increased disease risk. Our results confirming the role of gene-gene interaction and indicating variations in more than one gene may play a role in the susceptibility to lung cancer.
Our results support the results of previous studies that have reported lack of association between CHRNA3 rs1051730 and lung cancer [23, 24, 25, 26, 27, 28]. In contrast, CHRNA3 rs1051730 has been reported to be significantly associated with elevated risk for lung cancer among Caucasians, Asians, Japanese, and in European ancestry [21, 29, 30, 31, 32, 33, 34, 35].
Mechanisms of elevated lung cancer risk independent of smoking in individuals with rs1051730 variant is not entirely clear. While David et al. found that rs1051730 was associated with cigarette per day (CPD) and lung cancer in African-Americans , other studies have reported associations between rs1051730 and lung cancer in nonsmokers [33, 37, 38, 39].
In our study, XRCC1 rs25487 was not associated with lung cancer and concomitant presence with either ERCC1 or CHRNA3 variants was not associated with elevated risk for the disease in our population. The association of rs25487 with lung cancer in different ethnic groups gave inconsistent results [40, 41, 42, 43, 44, 45, 46, 47], while some studies reported significant association between the variant allele and lung cancer [40, 41, 42], other studies reported lack of such association [43, 44].
In the present study, ERCC1 rs735482 variant was associated with 6.9-fold elevated risk of lung cancer among smokers. In Chinese population, rs735482 was associated with lung cancer risk . In contrast, Azad et al. reported lack of association with squamous cell carcinoma, the overall survival (OS), or the disease-free survival (DFS) ; however, in a Korean study, rs735482 was associated with poor survival in NSCLC patients . In contrast, better prognosis was associated with the variant allele in lung adenocarcinoma patients . The inconsistent results were attributed to the inconformity to Hardy–Weinberg equilibrium or to the small sample size.
Gene-environment interaction involving ERCC1 rs735482 variant elevates the risk of lung cancer among smokers. Concomitant presence of CHRNA3 rs1051730 and ERCC1 rs735482 variants augments the risk of lung cancer. Our results emphasize the role of gene-gene interaction in the pathogenesis of lung cancer and the underlying mechanisms need to be clarified in future studies.
None to declare.
All authors contributed to the present study. NE and DE designed the study, NE collected the samples and clinic pathological data, DE performed the molecular analysis, and AM analyzed the data. NE and DE wrote the manuscript. All authors have read, revised, and approved the final version of the manuscript.
None to declare.
Ethics approval and consent to participate
The study protocol was approved by Medical Research Ethics Committee (MREC) of the National Research Center of Egypt prior to the study commencement (Ref. no. 14008). All subjects were aware of the study protocol and gave written informed consent.
Consent for publication
The authors declare that they have no competing interests.
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