Combined CYP1A1/GSTM1 at-risk genotypes are overrepresented in squamous cell lung carcinoma patients but underrepresented in elderly tumor-free subjects

Association between the combined effects of GSTM1 present/null and CYP1A1 MspI polymorphisms with lung cancer risk: an updated meta-analysis

Background: Many studies have been performed to explore the combined effects of glutathione-S-transferase M1 (GSTM1) present/null and cytochrome P4501A1 (CYP1A1) MspI polymorphisms with lung cancer (LC) risk, but the results are contradictory. Two previous meta-analyses have been reported on the issue in 2011 and 2014. However, several new articles since then have been published. In addition, their meta-analyses did not valuate the credibility of significantly positive results.

Objectives: We performed an updated meta-analysis to solve the controversy following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines.

Methods: False-positive report probability (FPRP), Bayesian false discovery probability (BFDP), and the Venice criteria were used to verify the credibility of meta-analyses.

Results: Twenty-three publications including 5734 LC cases and 7066 controls met the inclusion criteria in the present study. A significantly increased risk of LC was found in overall analysis, Asians and Indians. However, all positive results were considered as ‘less-credible’ when we used the Venice criteria, FPRP, and BFDP test to assess the credibility of the positive results.

Conclusion: These positive findings should be interpreted with caution and results indicate that significant associations may be less-credible, there are no significantly increased LC risk between the combined effects of GSTM1 present/null and CYP1A1 MspI polymorphisms.

ADME pharmacogenetics: future outlook for Russia

This systematic review reflects the results of pharmacogenetic studies in the Russian Federation aimed at studying the genes involved in the drug biotransformation system. The works of Russian researchers found by us are mostly devoted to microsomal liver oxidation enzymes (metabolism) and membrane transporter systems (absorption and excretion). This review presents population-ethnic and associative clinical studies on the genes of the CYP450 system, noncytochrome oxidation enzymes ( SULT1A1, CES1), membrane transporter system genes ( ABCB1, SLCO1B1) and warfarin biotransformation enzymes ( VKORC1, GGCX). The information is structured in the form of 11 tables, divided by regions of the Russian Federation.

Combined effects of CYP1A1 MspI and GSTM1 genetic polymorphisms on risk of lung cancer: an updated meta-analysis

Genetic polymorphisms of cytochrome P450 1A1 (CYP1A1) and glutathione S-transferase M1 (GSTM1) genes might contribute to the variability in individual susceptibility to lung cancer, but the reported results from individual studies are not always consistent. We therefore conducted a meta-analysis to systematically estimate the associations between polymorphisms of these two genes and risk of lung cancer. Twenty-one studies with 8,926 subjects were finally enrolled into this study. Meta-analysis was performed by RevMan 5.2. Odds ratio (OR) and its 95 % confidence interval (CI) were calculated to evaluate the susceptibility to lung cancer. Compared with the wild-type homozygous genotype, significantly elevated risk of lung cancer were associated with variant CYP1A1 MspI (m1/m2 + m2/m2 vs. m1/m1: OR = 1.27, 95 % CI = 1.12-1.43, P < 0.001) and deletion of GSTM1 (null vs. present: OR = 1.26, 95 % CI = 1.13-1.40, P < 0.001). Both the two genetic polymorphisms were independently associated with the risk of lung cancer. The pooled OR of lung cancer for population with both CYP1A1 MspI and GSTM1 mutations (MspI m1/m2 or m2/m2 and GSTM1 null) was 1.62 (95 % CI 1.27-2.07, P < 0.001) when compared with those without any of the above mutations, which is higher than single genetic polymorphism. In the stratified analysis, significantly higher risks of lung cancer associated with above genetic polymorphisms were found only in Asian population. This meta-analysis suggests that the CYP1A1 MspI and GSTM1 polymorphisms correlate with increased lung cancer susceptibility independently, and that there is an interaction between the two genes. However, the associations vary in different ethnic populations.

CYP1A1 gene polymorphisms and smoking status as modifier factors for lung cancer risk

OBJECTIVE

Lung cancer remains the most prevalent malignancy worldwide. Susceptibility to lung cancer has been shown to be modulated by inheritance of polymorphic genes. Several metabolic enzymes are currently under investigation for their possible role in lung cancer susceptibility, including members of the cytochrome P450 (CYP) superfamily. The aim of this work was to identify the correlation between CYP1A1 m1 and m2 polymorphisms and lung cancer risk and figure its interactions with smoking as genetic modifiers in the etiology of lung cancer in the Egyptian population.

MATERIALS AND METHODS

One hundred and ten patients with lung cancer and one hundred and ten controls were enrolled in the study. CYP1A1 m1 and m2 polymorphisms were determined using polymerase chain reaction restriction fragment length polymorphism.

RESULTS

Subjects carrying TC and CC genotypes of CYP1A1 m1 and AG and GG genotypes of CYP1A1 m2 were significantly more likely to develop lung cancer especially squamous cell carcinoma. The proportion of lung cancer attributable to the interaction of smoking and CYP1A1 m1 and CYP1A1 m2 polymorphisms was 32% and 52% respectively.

CONCLUSION

Our results revealed that CYP1A1 m1 and m2 polymorphisms contribute to smoking related lung cancer risk in the Egyptian population.

CASP-1, -2 and -5 gene polymorphisms and cancer risk: A review and meta-analysis

Accumulating evidence suggests the CASP gene family is important in the development of carcinogenesis. These genetic polymorphisms have been extensively investigated as a potential risk factor for cancer, but results have been inconclusive. This Human Genome Epidemiology (HuGE) review and meta-analysis was performed to investigate the associations between CASP-1, -2 and -5 and cancer risk. A literature search of Pubmed, Embase, Web of Science and CBM databases was conducted from inception through September 1st, 2012. Four case-control studies with a total of 1,592 cancer cases and 1,833 healthy controls were included in the present meta-analysis. Crude odds ratios (ORs) with 95% confidence intervals (CIs) were used to assess the strength of association. Five polymorphisms were examined, including rs501192 (G>A), rs4647297 (C>G), rs507879 (T>C), rs3181320 (G>C) and rs523104 (G>C). Meta-analysis results showed that the rs3181320*C allele/carrier were associated with increased risk of various types of cancers (OR=1.26; 95% CI, 1.04-1.54; P=0.020 and OR=1.33; 95% CI, 1.00-1.75; P=0.047, respectively). However, similar associations were not found in the rs501192, rs4647297, rs507879 and rs523104 polymorphisms (all P>0.05). Results from the current meta-analysis suggest that the rs3181320*C allele/carrier in CASP-5 gene are potential risk factors for cancer.

Genetic polymorphisms involved in carcinogen metabolism and DNA repair and lung cancer risk in a Japanese population

BACKGROUND

Several components of overall lung carcinogenesis, carcinogen metabolic and DNA repair pathways may be involved in individual genetic susceptibility to lung cancer.

METHODS

We evaluated the role of cytochrome P450 (CYP) 1A1 rs4646903 and rs104894, glutathione S-transferase (GST) M1 and GSTT1 deletion polymorphisms, GSTP1 rs1695, x-ray repair, excision repair cross-complementing group 2 (ERCC2) rs13181, complementing defective in Chinese hamster 1 rs25487, and XRCC3 rs861539 in a case-control study comprising 462 lung cancer cases and 379 controls in a Japanese population. Unconditional logistic regression was used to assess the adjusted odds ratios (OR) and 95% confidence intervals (95% CI).

RESULTS

CYP1A1 rs4646903 (OR = 1.72, 95% CI = 1.25-2.38), rs1048943 (OR = 1.40, 95% CI = 1.02-1.92), the GSTM1 deletion polymorphism (OR = 1.38, 95% CI = 1.01-1.89), GSTP1 rs1695 (OR =1.48, 95% CI = 1.04-2.11), ERCC2 rs13181 (OR = 1.89, 95% CI = 1.28-2.78), and Chinese hamster 1 rs25487 (OR = 1.54, 95% CI = 1.12-2.13) were associated with lung cancer risk whereas the GSTT1 deletion polymorphism and XRCC3 rs861539 were not. A pertinent combination of multiple "at-risk" genotypes of CYP1A1 rs4646903, the GSTM1 deletion polymorphism and ERCC2 rs13181 was at a 5.94-fold (95% CI = 2.77-12.7) increased risk of lung cancer.

CONCLUSIONS

A pertinent combination of multiple at-risk genotypes may detect a high-risk group. Further studies are warranted to verify our findings.

CYP1A1 MspI and exon7 gene polymorphisms and lung cancer risk: an updated meta-analysis and review

BACKGROUND

Many studies have examined the association between the CYP1A1 MspI and exon 7 gene polymorphisms and lung cancer risk in various populations, but their results have been inconsistent.

METHODS

To assess this relationship more precisely, a meta-analysis and review were performed. The PubMed, Embase, Web of Science, and CNKI database was searched for case-control studies published up to June 2010. Data were extracted and pooled odds ratios (OR) with 95% confidence intervals (CI) were calculated.

RESULTS

Ultimately, 64 studies, comprising 18,397 subjects from 49 case-control studies of the MspI genotype and 18,518 patients from 40 case-control studies of the exon 7 genotype, were included. A significantly elevated lung cancer risk was associated with 2 MspI genotype variants (for type C vs. Type A: OR = 1.26, 95% CI = 1.12-1.42; for types B and C combined vs. Type A: OR = 1.20, 95% CI = 1.13-1.28) in overall population. In the stratified analysis, a significant association was found in Asians, Caucasians, lung SCC, lung AC and Male population, not in mixed population, lung SCLC and female population. However, inconsistent results were observed for CYP1A1 exon7 in our meta-analysis, two variants of the exon 7 polymorphism were associated with a significantly higher risk for lung cancer (for Val/Val vs. Ile/Ile: OR = 1.24, 95% CI = 1.09-1.42; for (Ile/Val +Val/Val) vs. Ile/Ile: OR = 1.15, 95% CI = 1.07-1.24) in overall population. In the stratified analysis, a significant assocation was found in Asians, Caucasians, lung SCC and Female population, not in mixed population, lung AD, lung SCLC and Male population. Additionally, a significant association was found in smoker population and not found in non-smoker populations for CYP1A1 MspI and exon7 gene.

CONCLUSIONS

This meta-analysis suggests that the MspI and exon 7 polymorphisms of CYP1A1 correlate with increased lung cancer susceptibility and there is an interaction between two genotypes of CYP1A1 polymorphism and smoking, but these associations vary in different ethnic populations, histological types of lung cancer and gender of case and control population.

Selection of extreme phenotypes: the role of clinical observation in translational research

Systematic collection of phenotypes and their correlation with molecular data has been proposed as a useful method to advance in the study of disease. Although some databases for animal species are being developed, progress in humans is slow, probably due to the multifactorial origin of many human diseases and to the intricacy of accurately classifying phenotypes, among other factors. An alternative approach has been to identify and to study individuals or families with very characteristic, clinically relevant phenotypes. This strategy has shown increased efficiency to identify the molecular features underlying such phenotypes. While on most occasions the subjects selected for these studies presented harmful phenotypes, a few studies have been performed in individuals with very favourable phenotypes. The consistent results achieved suggest that it seems logical to further develop this strategy as a methodology to study human disease, including cancer. The identification and the study with high-throughput techniques of individuals showing a markedly decreased risk of developing cancer or of cancer patients presenting either an unusually favourable prognosis or striking responses following a specific treatment, might be promising ways to maximize the yield of this approach and to reveal the molecular causes that explain those phenotypes and thus highlight useful therapeutic targets. This manuscript reviews the current status of selection of extreme phenotypes in cancer research and provides directions for future development of this methodology.

Coding polymorphisms in Casp5, Casp8 and DR4 genes may play a role in predisposition to lung cancer

Apoptosis plays a role in the elimination of DNA-damaged cells thus protecting the host from cancer development. Some data indicate that normal variations within the sequence of apoptotic genes may lead to suboptimal apoptotic capacity and therefore increased cancer risk. We tested 19 coding apoptotic gene SNPs in 2-stage molecular epidemiological study. For the preliminary sorting of SNP candidates, we employed a "comparison of extremes" approach, where 111 patients with highly pronounced LC susceptibility (non-smokers or young-onset light smokers) were analyzed against 110 subjects with the evidence for LC tolerance (elderly tumor-free heavy smokers). Three genotypes demonstrated possible association with LC risk (Leu/Leu-homozygotes for Casp5 Val318Leu versus other genotypes: OR=2.47 (95% CI: 1.07-5.69), p=0.03; His-carriers for Casp8 His302Asp: OR=2.26 (95% CI: 1.18-4.31), p=0.02; Arg-carriers for DR4 Lys441Arg: OR=1.89 (95% CI: 1.05-3.40), p=0.03), and therefore were selected for the validation. The extended study included 2 case-control series, namely subjects from Russia (351 LC cases and 538 controls) and Moldova (296 LC cases and 295 controls). Interestingly, all three candidate genotypes consistently demonstrated OR above 1 both in Russian and in Moldovian groups. Although the combined Mantel-Haenszel analysis yet failed to reach statistical significance (OR=1.22 (95% CI: 0.90-1.65), p=0.21; OR=1.17 (95% CI: 0.92-1.50), p=0.21; OR=1.19 (95% CI: 0.95-1.51), p=0.14, respectively), the obtained data indicate that Casp5, Casp8 and DR4 gene polymorphisms may deserve consideration in large-scale case-control studies of LC risk modifiers.

Glutathione S-transferase M1 (GSTM1) polymorphisms and lung cancer: a literature-based systematic HuGE review and meta-analysis

Multiple genes have been studied for potential associations with lung cancer. The gene most frequently associated with increased risk has been glutathione S-transferase M1 (GSTM1). The glutathione S-transferase enzyme family is known to catalyze detoxification of electrophilic compounds, including carcinogens, therapeutic drugs, environmental toxins, and products of oxidative stress. In this review, the authors summarize the available evidence associating lung cancer with the GSTM1 gene. They describe results from an updated meta-analysis of 98 published genetic association studies investigating the relation between the GSTM1 null variant and lung cancer risk including 19,638 lung cancer cases and 25,266 controls (counting cases and controls in each study only once). All studies considered, the GSTM1 null variant was associated with an increased risk of lung cancer (odds ratio (OR) = 1.22, 95% confidence interval (CI): 1.14, 1.30), but no increase in risk was seen (OR = 1.01, 95% CI: 0.91, 1.12) when only the five largest studies (>500 cases each) were considered. Furthermore, while GSTM1 null status conferred a significantly increased risk of lung cancer to East Asians (OR = 1.38, 95% CI: 1.24, 1.55), such a genotype did not confer increased risk to Caucasians. More data regarding the predictive value of GSTM1 genetic testing are needed before population-based testing may be reasonably considered.