Cancer risk and low-penetrance susceptibility genes in gene-environment interactions

Cigarette smoking, MDM2 SNP309, gene-environment interactions, and lung cancer risk: a meta-analysis

MDM2 SNP309 polymorphism was found to contribute to genetic susceptibility to lung cancer in humans. However, association studies on these polymorphisms in lung cancer cases have shown conflicting results. In order to derive a more precise estimation of the relationship, a meta-analysis was performed. Odds ratio (OR) with 95% confidence interval (CI) was applied to assess the strength of association between MDM2 SNP309 polymorphism and risk of lung cancer development. The logistic regression indicated that the genetic model was most likely to be recessive. Using a recessive model, the pooled OR estimating the genotype GG against the T-allele carriers (GT + TT) were calculated. Eight studies, including 6063 cases and 6678 controls, were involved in this meta-analysis. Overall meta-analysis indicated that MDM2 SNP309 GG genotypes have an approximate 16% increased risk for lung cancer development with a statistical significance (OR = 1.16; 95% CI: 1.01-1.34). In the subgroup analyses based on ethnicities, no significant elevated risk was associated with MDM2 SNP309 genotypes found in Asian and Europeans. No significant increased risk was associated with MDM2 SNP309 genotypes found in ever smokers. MDM2 SNP309 GG genotype had an approximate 36% enhanced risk of lung cancer development with statistical significance in never smokers (OR = 1.36; 95% CI: 1.10-1.68). Although some bias cannot be excluded, this meta-analysis supports the view that MDM2 SNP309 gene is a low-penetrance susceptible gene in the development of lung cancer, and the relationship of MDM2 SNP309 and lung cancer is stronger for never smokers.

Evaluation of environmental and personal susceptibility characteristics that modify genetic risks

Study design in understanding gene-environment interaction plays a crucial role. Different study designs with their advantages and limitations are described in this chapter. Gene penetrance has been studied in several cancers, including breast and prostate cancer. Compared with high-penetrance genes, such as breast cancer (BRCA)1, BRCA2 in breast cancer, gene-environment interaction plays a major role in cancer development where low-penetrance genes are the major players. Genetic polymorphism is determined in low- and high-penetrance genes to identify cancer-related polymorphisms. The role of genetic and epigenetic factors in cancer development is discussed. Preventive approaches, especially in the epigenetic field, show promise. A discussion about different epidemiological methods with examples is provided.

Association of single nucleotide polymorphisms in PIM-1 gene with the risk of Korean lung cancer

PURPOSE

The expression of the PIM-1 gene, which is a proto-oncogene that encodes a serine/threonine kinase, is associated with multiple cellular functions such as proliferation, differentiation, apoptosis and tumorigenesis. In particular, several studies have reported that the PIM-1 gene is associated with the development of lymphoma, leukemia and prostate cancer. Therefore, this study was conducted to evaluate the association between the single nucleotide polymorphisms in the PIM-1 gene and the risk of lung cancer occurrence in the Korean population.

MATERIALS AND METHODS

To evaluate the role of the PIM-1 gene in the development of lung cancer, the genotypes of the PIM-1 gene were determined in 408 lung cancer patients and 410 normal subjects.

RESULTS

We found that the T-C-T-C haplotypes of the PIM-1 gene (-1196 T>C, IVS4 +55 T>C, IVS4 +1416 T>A and +3684 C>A) were associated with an increased risk of lung cancer [adjusted odds ratio (aOR): 3.98; 95% CI: 1.24 approximately 12.75, p-value: 0.020]. In particular, these haplotypes showed an increased risk of lung cancer in males (aOR: 5.67; 95% CI: 1.32~24.30, p-value: 0.019) and smokers (aOR: 7.82; 95% CI: 1.75 approximately 34.98, p-value: 0.007).

CONCLUSIONS

The present results suggest that the T-C-T-C haplotype of the PIM-1 gene could influence the risk of developing smoking-related lung cancer in the Korean population. Additional functional studies with an larger sample sized analysis are warranted to reconfirm our findings.

Polymorphisms in the Caspase7 gene and the risk of lung cancer

BACKGROUND

Caspase7 (CASP7) is an executioner CASP that conducted a coordinated program of proteolysis that results in the destruction of critical cell structures, and it plays an important role in the development and progression of cancer. The purpose of this study is to comprehensively evaluate potential functional polymorphisms in the CASP7 gene in relation to the risk of lung cancer.

METHODS

We first captured seven single nucleotide polymorphisms (SNPs) in the regulating region, exons and exon-intron boundaries of the CASP7 gene using public database and then determined their frequencies in 27 healthy Korean individuals. Next, we examined four SNPs (rs12415607g.C>A; rs11593766g.T>G; rs2227310g.C>G; and rs10787498g.T>C) in a case-control study that consisted of 720 lung cancer patients and 720 healthy controls.

RESULTS

Of the four SNPs studied in the case-control study, only the distribution of the rs2227310g.C>G genotypes differed significantly between the cases and controls (P=0.03). The rs2227310 GG genotype was associated with a significantly increased risk of lung cancer when compared with the rs2227310 CC genotype [adjusted odds ratio (OR)=1.42, 95% confidence interval (CI)=1.05-1.93, P=0.02] and with the combined rs2227310 CC and CG genotype (adjusted OR=1.38, 95% CI=1.05-1.81, P=0.02). Consistent with the results of genotyping analysis, the ATGT haplotype (rs12415607A/rs11593766T/rs2227310G/rs10787498T) was associated with a significantly increased risk of lung cancer when compared to other haplotypes (adjusted OR=1.21, 95% CI=1.04-1.42, P=0.02).

CONCLUSION

These results suggest that the CASP7 polymorphisms contribute to the genetic susceptibility to lung cancer.

The genetic polymorphisms of HER-2 and the risk of lung cancer in a Korean population

Background

Human Epidermal Growth Factor Receptor 2 (HER-2; also known as erbB-2 or neu), a proto-oncogene of the receptor tyrosine kinase superfamily, has been associated with carcinogenesis and prognosis of human cancers, acting as a binding partner of other epidermal growth factor receptor (EGFR) family in the activation of EGFR signaling. Amplification of the HER-2 gene has been reported in lung cancer, where it has been associated with poor prognosis. In this study, we investigated whether the four polymorphisms (-3444C>T, -1985 G>T, I655A A>G and P1170A C>G) of the HER-2 gene are associated with the risk of lung cancer in Korean populations.

Methods

The frequencies of 4 polymorphisms of the HER-2 gene were examined by the polymerase chain reaction-restriction fragment length polymorphism or the single-nucleotide polymorphism-identification technology assay in the 407 lung cancer patients and 407 healthy controls.

Results

The frequencies of the 4 polymorphisms were not significantly different between patient and control groups in overall subjects. However, in the subgroup analysis, the 3 single nucleotide polymorphisms (-3444C>T, -1985G>T and P1170A C>G) showed statistically significant differences in the subgroups of females, non-smokers, and non-drinkers (p < 0.05). Additionally, we found the association between the risk of lung cancer and the polymorphisms of HER-2 gene in non-smoker subgroups with adenocarcinoma (p < 0.05).

Conclusion

Our results suggest that the polymorphisms of the HER-2 gene are associated with an increased susceptibility to lung cancer in females, non-smokers and non-drinkers subgroups in the Korean population.

Styrene Metabolism, Genotoxicity, and Potential Carcinogenicity

This report reviews styrene biotransformation, including minor metabolic routes, and relates metabolism to the genotoxic effects and possible styrene-related carcinogenicity. Styrene is shown to require metabolic activation in order to become notably genotoxic and styrene 7,8-oxide is shown to contribute quantitatively by far the most (in humans more than 95%) to the genotoxicity of styrene, while minor ring oxidation products are also shown to contribute to local toxicities, especially in the respiratory system. Individual susceptibility depending on metabolism polymorphisms and individual DNA repair capacity as well as the dependence of the nonlinearity of the dose-response relationships in the species in question and the consequences for risk evaluation are analyzd.

AMBIENCE: a novel approach and efficient algorithm for identifying informative genetic and environmental associations with complex phenotypes

We developed a computationally efficient algorithm AMBIENCE, for identifying the informative variables involved in gene-gene (GGI) and gene-environment interactions (GEI) that are associated with disease phenotypes. The AMBIENCE algorithm uses a novel information theoretic metric called phenotype-associated information (PAI) to search for combinations of genetic variants and environmental variables associated with the disease phenotype. The PAI-based AMBIENCE algorithm effectively and efficiently detected GEI in simulated data sets of varying size and complexity, including the 10K simulated rheumatoid arthritis data set from Genetic Analysis Workshop 15. The method was also successfully used to detect GGI in a Crohn's disease data set. The performance of the AMBIENCE algorithm was compared to the multifactor dimensionality reduction (MDR), generalized MDR (GMDR), and pedigree disequilibrium test (PDT) methods. Furthermore, we assessed the computational speed of AMBIENCE for detecting GGI and GEI for data sets varying in size from 100 to 10(5) variables. Our results demonstrate that the AMBIENCE information theoretic algorithm is useful for analyzing a diverse range of epidemiologic data sets containing evidence for GGI and GEI.

Significance of alterations in plasma lipid profile levels in breast cancer

HYPOTHESES

The relationship between lipids and breast cancer is obscure. Until now, conflicting results have been reported on the association between lipids and risk of breast cancer in women. Therefore, the major aim of this study is to examine the role of alterations in lipid profile in breast cancer.

STUDY DESIGN

Plasma lipids (ie, total cholesterol [TC], high-density lipoprotein [HDL], low-density lipoprotein [LDL], very-low-density lipoprotein [VLDL], and triglycerides [TG]) were analyzed from 70 controls, 30 patients with benign breast disease (BBD), 125 untreated breast cancer patients, and 93 posttreatment follow-up samples.

METHODS

Samples were analyzed using highly sensitive and specific spectrophotometric methods.

RESULTS

Plasma TC, LDL, VLDL, and TG were significantly lower (p = .042, p = .003, p = .024, p = .014, respectively) in patients with BBD compared with controls. Plasma TC and HDL were significantly lower (p = .026, p = .0001, respectively), and VLDL and TG were significantly higher (p = .009, p = .05) in breast cancer patients as compared with controls. Plasma VLDL and TG were significantly higher in breast cancer patients as compared with patients with BBD. The receiver-operating characteristic curve showed that plasma TC, LDL, VLDL, and TG levels could significantly discriminate (p = .001, p = .005, p = .005, p = .005, respectively) between controls and patients with BBD. Plasma levels of TC, HDL, VLDL, and TG could significantly distinguish (p = .01, p = .002, p = .001, p = .002, respectively) between controls and breast cancer patients. Plasma levels of VLDL and TG could significantly discriminate (p = .000, p = .000, respectively) between patients with BBD and breast cancer patients. Odds ratio analysis revealed that higher levels of TC and HDL were significantly associated with a reduction in breast cancer risk (p = .01 and p = .0001, respectively), whereas higher levels of VLDL and TG were significantly associated with increased breast cancer risk (p = .001 and p = .002, respectively). Plasma VLDL and TG levels were significantly lower in complete responders as compared with pretreatment levels (p = .000, p = .000, respectively), and plasma TC and LDL levels were significantly lower in nonresponders as compared with pretreatment levels (p = .015, p = .009, respectively).

CONCLUSION

The alterations in lipid profile levels showed a significant correlation with breast cancer risk, disease status, and treatment outcome.

Identification of polymorphisms in the Caspase-3 gene and their association with lung cancer risk

Caspase-3 (CASP-3) is a primary effector CASP that executes programmed cell death, and it plays an important role in the development and progression of cancer. Polymorphisms in the CASP-3 gene may influence CASP-3 production and/or activity, thereby modulating the susceptibility to lung cancer. To test this hypothesis, we first screened for polymorphisms in the CASP-3 gene by direct sequencing of genomic DNA samples from 27 healthy Koreans, and then evaluated their associations with lung cancer in a case-control study that consisted of 582 lung cancer patients and 582 healthy controls. Individuals with at least one variant allele of the -928A > G, 77G > A, and 17532A > C polymorphisms were at a significantly decreased risk for lung cancer in comparison to the carriers with each homozygous wild-type allele [adjusted odds ratio (OR) = 0.79, 95% confidence interval (CI) = 0.62-1.00, P = 0.05; adjusted OR = 0.78, 95% CI = 0.61-0.99, P = 0.04; and adjusted OR = 0.74, 95% CI = 0.58-0.95, P = 0.02, respectively]. Consistent with the results of genotyping analysis, the GAGC haplotype carrying the variant allele at all of the -928A > G, 77G > A, and 17532A > C loci was associated with a significantly decreased risk of lung cancer compared to the AGGA haplotype carrying no variant alleles at the three loci (adjusted OR = 0.66, 95% CI = 0.51-0.86, P = 0.002 and Bonferroni corrected P = 0.008). These results suggest that the CASP-3 polymorphisms and their haplotypes contribute to the genetic susceptibility to lung cancer.

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.

Putative association of the single nucleotide polymorphisms in RASSF1A promoter with Korean lung cancer

SUMMARY

The RASSF1 gene, a putative tumor suppressor gene located on human chromosome 3p21, has attracted a great deal of attention because of frequent allelic loss and gene silencing via promoter hypermethylation in a variety of human malignancies. To evaluate the role of RASSF1A gene in lung cancer risk, genotypes of the RASSF1A promoter region (-710 C>T and -392T>C) were determined in 410 lung cancer patients and 410 normal subjects. Furthermore, to examine potential effects of the common haplotypes (C-C, T-T and C-T haplotypes) on RASSF1A transcription, luciferase reporter assays were performed in H2009 and H358 non-small cell lung cancer (NSCLC) cell lines. We found that ht2 C-T haplotype was associated with susceptibility to the risk of lung cancer in dominant (odds ratio (OR): 0.69; 95% CI: 0.46-0.99) model. In particular, we found that C-T haplotype showed a decreased risk of lung cancer in males (codominant OR: 0.59; 95% CI: 0.38-0.93 and dominant OR: 0.58; 95% CI: 0.35-0.96) and in smokers (codominant OR: 0.58; 95% CI: 0.36-0.93 and dominant OR: 0.56; 95% CI: 0.33-0.96). Interestingly, C-T haplotype induced transcriptional activity by 50-60% compared with other haplotypes in NSCLC cell lines. These results suggest that RASSF1A promoter polymorphisms affect RASSF1A expression, further contributing to the genetic susceptibility to lung cancer.

Identification of polymorphisms in the XIAP gene and analysis of association with lung cancer risk in a Korean population

The X-linked inhibitor of apoptosis protein (XIAP) is a potent mammalian IAP, and has been shown to play an important role in development and progression of cancer. Polymorphisms in the XIAP gene may influence XIAP production or activity, thereby modulating susceptibility to lung cancer. To test this hypothesis, we first screened for polymorphisms in the XIAP gene by direct sequencing of genomic DNA samples from 27 healthy Korean women and then performed a case-control study to evaluate the association between the polymorphisms and the risk of lung cancer. The XIAP genotypes were determined by polymerase chain reaction amplification and melting curve analysis in 582 lung cancer patients and in 582 healthy control subjects who were frequency-matched for age and sex. We identified 12 single nucleotide polymorphisms (SNPs), one novel SNP [30051C>G (A321G) in exon 3] and the following 11 known SNPs: 192G>C (rs5956578), 262C>T (rs28382699), 318C>T (rs5958318), and 374C>T (rs12687176) in the putative promoter; 26615A>G (rs2355676) in intron 1; 41725A>G (rs5958338) in intron 5; 42009A>C (Q423P, rs5956583) in exon 6; 48162T>C (rs17334739) and 48228C>T (rs28382739) in intron 6; and 48542A>G (rs28382740) and 49333G>T (rs28382742) in 3'-UTR. Four of these 12 SNPs were selected for large-scale genotyping based on their frequencies and haplotype tagging status: 262C>T, 318C>T, 374C>T, and 42009A>C. The four XIAP polymorphisms and their haplotypes exhibited no apparent relationship with the risk of lung cancer. In addition, we observed no evidence of effect modification by age, sex, smoking history, or tumor histology. These results suggest that XIAP polymorphisms do not significantly affect susceptibility to lung cancer in Koreans.

Frequency of TP53 mutations in relation to Arg72Pro genotypes in non small cell lung cancer

Mutations in the TP53 gene are important events during human lung carcinogenesis. The TP53 gene harbors several polymorphisms, and functional studies have shown that the Arg72Pro polymorphism alters both wild-type and mutant p53 protein activity. Thus, we hypothesized that certain Arg72Pro genotypes may influence the frequency and pattern of somatic mutations in TP53. We therefore examined the status of the Arg72Pro polymorphism and TP53 mutations in 260 non-small-cell lung cancer cases. Here we report a significant trend toward lower frequency of TP53 mutations with increasing number of Pro72 alleles (P = 0.02). Overall, Pro72 allele carriers had significantly lower frequency of TP53 mutations compared with Arg72 homozygotes (P = 0.02). In addition, carriage of the Pro72 variant was related to a lower frequency of mutations affecting the hotspot codon 273. Mutations at codon 273 accounted for 10.6% of the mutations in Arg72 homozygotes and 1.7% of the mutations in Pro72 allele carriers. Our results suggest that the genotype of the Arg72Pro polymorphism may modulate the frequency of TP53 mutations in non-small-cell lung cancer.

A novel rasH2 mouse carcinogenesis model that is highly susceptible to 4-NQO-induced tongue and esophageal carcinogenesis is useful for preclinical chemoprevention studies

We investigated the susceptibility of 4-nitroquinoline 1-oxide (4-NQO)-induced tongue carcinogenesis in male CB6F1-Tg-rasH2 @Jcl mice (Tg mice). The Tg mice were administered 4-NQO (20 p.p.m. in drinking water) for 2, 4, 6 or 8 weeks, and thereafter they were untreated up to week 24. At week 24, a higher incidence (80%) of tongue neoplasm with dysplasia was noted in the mice that received 4-NQO for 8 weeks in comparison with the other groups (20% incidence for each) treated with 4-NQO for 2, 4 and 6 weeks. Esophageal tumors also developed in the Tg mice were 4-NQO. Immunohistochemical observation revealed that the EP receptors, especially EP(1) and EP(2), expressed in the tongue and esophageal lesions induced by 4-NQO, thus suggesting the involvement of prostaglandin (PG) E(2) and EP(1,2) receptors in the tongue and esophageal carcinogenesis. Using this animal model, we investigated the potential chemopreventive ability of pitavastatin (1, 5 and 10 p.p.m. in diet for 15 weeks), starting 1 week after the cessation of 4-NQO-exposure (20 p.p.m. in drinking water for 8 weeks). Dietary pitavastatin at 10 p.p.m. significantly reduced the incidence and multiplicity of the tongue, but not esophageal neoplasms by the modulation of prostaglandin E2 biosynthesis, EP(1) and EP(2) expression and proliferation. Our results thus suggest that a rasH2 mouse model of 4-NQO-induced tongue and esophageal carcinogenesis can be utilized for investigating the pathogenesis of cancer development in these tissues and may well prove to be useful for identifying candidate cancer chemopreventive agents for the upper digestive organs.

Polymorphisms of CAK genes and risk for lung cancer: A case–control study in Chinese population

The incidence of lung cancer has been increasing over recent decades. Previous studies show that polymorphisms of the genes involved in carcinogen-detoxication, DNA repair and cell cycle control compose of the risk factors for lung cancer. Recent observations reveal that the components of CAK: Cdk7, MAT1 and cyclin H, may play important roles in cell cycle control, transcriptional control, and DNA repairing process, all of which are important in carcinogenesis. To test whether the genetic variants of CAK genes modify the risk of lung cancer, we compared the manifestation of 25 single nucleotide polymorphisms (SNPs) and the haplotypes of Cdk7, MAT1 and cyclin H between 500 patients with lung cancer and 517 healthy controls. Our results indicated that the genotype frequency of MAT1 79023A/G (p = 0.042) and MAT1 85693C/T (p = 0.005) of cases significantly differed from those of the controls. Further analyses revealed that cyclin H 11817C/T, MAT1 12199A/G, MAT1 70650A/G, MAT1 79023A/G and MAT1 85693C/T significantly influenced the susceptibility of lung cancer in a dominant genetic model while cyclin H 12128A/T and MAT1 42172A/G did in a recessive model. Strongest association between cyclin H alleles and lung cancer patients was found in the non-smoke subpopulation. The haplotype 'TAC' (p = 0.007) increased and the haplotype 'TTC' (p = 0.043) decreased the risk of lung cancer. The potential gene-gene and gene-environmental interactions on lung cancer risk was evaluated using MDR software. A significant interaction between the three CAK component genes was identified and the combination of smoking status and genetic factors barely increased the accuracy. Our results suggested that genetic variants in CAK genes, Cdk7, cyclin H, MAT1, might modulate the risk of lung cancer in a gene-gene interaction mode, which consist to the biochemical interaction of corresponding proteins.

Polymorphism in the hMSH2 gene (gISV12-6T > C) is a prognostic factor in non-small cell lung cancer

Genetic polymorphisms at the genes involved in mismatch repair may determine individual's susceptibility to cancer initiation and progression. However, the prognostic significance of hMSH2 gIVS12-6T>C polymorphism (T-C substitution at the -6 intronic splice acceptor site of exon 13) in non-small cell lung cancer (NSCLC) remains unclear. Therefore, we investigated the frequency of hMSH2 gIVS12-6T>C polymorphism in 156 NSCLC patients and 235 cancer-free individuals matched for age, gender and smoking habit. The correlations between hMSH2 genotypes and protein expression and survival of the patients were also analyzed. The frequencies of hMSH2 genotypes T/T, T/C, and C/C were 37.4%, 43.0%, and 19.6%, respectively, and the variant (C) allele was represented at a significantly higher frequency in the general Taiwanese population than in non-Asian populations (P<0.0001, chi(2) test). No significant difference in hMSH2 genotype distribution was found between NSCLC patients and cancer-free controls (P=0.255, multivariate logistic regression). However, the homozygous wild-type T/T genotype was significantly associated with a poor prognosis (P=0.007, log-rank test). Our study showed that the frequency of the variant C allele was significantly higher in the general Taiwanese population than in non-Asian populations and the T/T genotype of hMSH2 gIVS12-6T>C polymorphism was a poor prognostic factor in NSCLC patients.

Genetic pathways and mutation profiles of human cancers: site- and exposure-specific patterns

Cancer is a complex disease that involves the accumulation of both genetic and epigenetic alterations of numerous genes. Data in the Genetic Alterations in Cancer database for gene mutations and allelic loss [loss of heterozygosity (LOH)] in human tumors (e.g. lung, oral, esophagus, stomach and colon/rectum) were reviewed. Results for the genes and pathways implicated in tumor development at these sites are presented. Mutation incidence, spectra and codon specificity are described for lung, larynx and oral tumors. LOH occurred more frequently than gene mutations in tumors from all sites examined. The cell cycle gene, TP53 (all sites), and cell signaling gene, APC (colorectal and gastric cancers), were the only genes with similar incidences of LOH and mutation. Alterations of one or more cell cycle and cell signaling genes were reported for tumors from each site. Site-specific activation was apparent in the cell signaling mitogen-activated protein kinase oncogenes (KRAS in lung, HRAS in oral cancers and BRAF in esophageal and colorectal cancers). Analysis of genetic changes in lung tumors showed that the incidence of mutations in the TP53 and KRAS genes and the incidence of LOH in the FHIT gene were significantly greater in smokers versus non-smokers (P < 0.01). In lung and oral cancers, the TP53 GC --> TA transversion frequency increased with tobacco smoke exposure (P < 0.05). Furthermore, the TP53 mutational hot spots for lung and laryngeal cancers from smokers included codons 157, 245 and 273, whereas for oral tumors included codons 280 and 281.

Polymorphisms in XPC, XPD, XRCC1, and XRCC3 DNA repair genes and lung cancer risk in a population of northern Spain

BACKGROUND

Polymorphisms in DNA repair genes have been associated to repair DNA lesions, and might contribute to the individual susceptibility to develop different types of cancer. Nucleotide excision repair (NER), base excision repair (BER), and double-strand break repair (DSBR) are the main DNA repair pathways. We investigated the relationship between polymorphisms in two NER genes, XPC (poly (AT) insertion/deletion: PAT-/+) and XPD (Asp312Asn and Lys751Gln), the BER gene XRCC1 (Arg399Gln), and the DSBR gene XRCC3 (Thr241Met) and the risk of developing lung cancer.

METHODS

A hospital-based case-control study was designed with 516 lung cancer patients and 533 control subjects, matched on ethnicity, age, and gender. Genotypes were determined by PCR-RFLP and the results were analysed using multivariate unconditional logistic regression, adjusting for age, gender and pack-years.

RESULTS

Borderline association was found for XPC and XPD NER genes polymorphisms, while no association was observed for polymorphisms in BER and DSBR genes. XPC PAT+/+ genotype was associated with no statistically significant increased risk among ever smokers (OR = 1.40; 95%CI = 0.94-2.08), squamous cell carcinoma (OR = 1.44; 95%CI = 0.85-2.44), and adenocarcinoma (OR = 1.72; 95%CI = 0.97-3.04). XPD variant genotypes (312Asn/Asn and 751Gln/Gln) presented a not statistically significant risk of developing lung cancer (OR = 1.52; 95%CI = 0.91-2.51; OR = 1.38; 95%CI = 0.85-2.25, respectively), especially among ever smokers (OR = 1.58; 95%CI = 0.96-2.60), heavy smokers (OR = 2.07; 95%CI = 0.74-5.75), and adenocarcinoma (OR = 1.88; 95%CI = 0.97-3.63). On the other hand, individuals homozygous for the XRCC1 399Gln allele presented no risk of developing lung cancer (OR = 0.87; 95%CI = 0.57-1.31) except for individuals carriers of 399Gln/Gln genotype and without family history of cancer (OR = 0.57; 95%CI = 0.33-0.98) and no association was found between XRCC3 Thr241Met polymorphism and lung cancer risk (OR = 0.92; 95%CI = 0.56-1.50), except for the 241Met/Met genotype and squamous cell carcinoma risk (OR = 0.47; 95%CI = 0.23-1.00).

CONCLUSION

In conclusion, we analysed the association between XPC, XPD, XRCC1, and XRCC3 polymorphisms and the individual susceptibility to develop lung cancer in the Spanish population, specifically with a highly tobacco exposed population. We attempt to contribute to the discovery of which biomarkers of DNA repair capacity are useful for screening this high-risk population for primary preventing and early detection of lung cancer.

Association of HSP70-hom genetic variant with prostate cancer risk

Because of the importance of androgens to prostate cancer (PCa) development, several candidate genes along androgen pathway have been under intensive study. Given the role of the molecular chaperone HSP70 in the regulation of the androgen receptor (AR) transactivation function, we first chose to explore the association between the HSP70-hom functional genetic variant (+2437 T > C) and prostate cancer risk by genotyping DNA samples from 101 unselected PCa patients and 105 healthy men. There was a trend towards lower frequency of TC and CC genotypes among patients when compared with healthy controls, however the difference did not reach the statistical significance (TC genotype: OR = 0.53, P = 0.05; CC genotype: OR = 0.42, P = 0.16). Moreover, individuals carrying at least one C allele have a statistically significant lower susceptibility for PCa (OR = 0.51 (0.26-0.97); P = 0.02). Since some factors may influence tumor progression rather than initiation, we also examined the relationship between the HSP70-hom polymorphism and the clinical characteristics of the malignancy at the time of diagnosis. The stratified analysis of the genotypes with the clinical stage and tumor grade showed that there was no significant difference in the risk estimates according to prognostic indicators of PCa disease in our population study. This is the first report on the studies of HSP70 SNPs in PCa and our data suggest that this genetic variant may be a genetic marker for PCa susceptibility in Tunisians.

Sequence variations in DNA repair gene XPC is associated with lung cancer risk in a Chinese population: a case-control study

Background

The nucleotide excision repair (NER) protein, xeroderma pigmentosum C (XPC), participates in recognizing DNA lesions and initiating DNA repair in response to DNA damage. Because mutations in XPC cause a high risk of cancer in XP patients, we hypothesized that inherited sequence variations in XPC may alter DNA repair and thus susceptibility to cancer.

Methods

In this hospital-based case-control study, we investigated five XPC tagging, common single nucleotide polymorphisms (tagging SNPs) in 1,010 patients with newly diagnosed lung cancer and 1,011 matched cancer free controls in a Chinese population.

Results

In individual tagging SNP analysis, we found that rs3731055AG+AA variant genotypes were associated with a significantly decreased risk of lung adenocarcinoma [adjusted odds ratio (OR), 0.71; 95% confidence interval (CI), 0.56–0.90] but an increased risk of small cell carcinomas [adjusted OR, 1.79; 95% CI, 1.05–3.07]. Furthermore, we found that haplotype ACCCA was associated with a decreased risk of lung adenocarcinoma [OR, 0.78; 95% CI, 0.62–0.97] but an increased risk of small cell carcinomas [OR, 1.68; 95% CI, 1.04–2.71], which reflected the presence of rs3731055A allele in this haplotype. Further stratified analysis revealed that the protective effect of rs3731055AG+AA on risk of lung adenocarcinoma was more evident among young subjects (age ≤ 60) and never smokers.

Conclusion

These results suggest that inherited sequence variations in XPC may modulate risk of lung cancer, especially lung adenocarcinoma, in Chinese populations. However, these findings need to be verified in larger confirmatory studies with more comprehensively selected tagging SNPs.

Genetic variants inMGMTand risk of lung cancer in Southeastern Chinese: a haplotype-based analysis

O6-alkylguanine-DNA alkyltransferase (MGMT) is a universal DNA repair protein involved in the DNA direct reversal repair pathway that copes with alkylating carcinogens. Reduced MGMT expression as well as enzyme activity may result in an increased susceptibility to cancers. To elucidate the role of sequence variation in MGMT in the etiology of lung cancer, we conducted a comprehensive association study focusing on linkage disequilibrium (LD) structure of common variations across the MGMT sequence and its modification effect on smoking-related lung cancer risk. We rebuilt the LD block of MGMT by genotyping 39 SNPs and selected a subset of 10 haplotype-tagging SNPs (htSNP) and three pre- and interblock SNPs to capture variation across MGMT. By using a haplotype-based multifactor dimensionality reduction (MDR) analysis, we found that there were significant more-than-multiplicative interactions between diplotypes in block 5 and cumulative smoking and additive interaction between genotypes of preblock SNP rs1625649:C>A and smoking status in relation on lung cancer risk. Diplotypes in block 3 and block 5, genotypes of rs1625649:C>A, and trichotomized cumulative smoking are the four factors included in the MDR-defined best model on lung cancer risk. When these variables were combined and dichotomized, we found that subjects carrying the combined risk stratum had a significantly increased risk for lung cancer of 4.10-fold (odds ratio [OR]=4.10, 95% confidence interval [CI]=3.12-5.37, P=2.09 x 10(-24)). These findings suggest that genetic variants in MGMT may modulate the risk of smoking-related lung cancer. This haplotype-based interaction analysis might provide a "proof-of-principle" approach for studying candidate genes in cancer susceptibility.

No association between p73 G4C14-to-A4T14 polymorphism and the risk of lung cancer in a Korean population

A member of the p53 family, p73 may play an important role in the development of lung cancer. Variations in the DNA sequence in the p73 gene can lead to alterations in the production of p73 and/or activity, which can affect an individual's susceptibility to lung cancer. To test this hypothesis, this study examined the association between the G4C14-to-A4T14 polymorphism in the p73 gene and the risk of lung cancer in a Korean population. The p73 G4C14-to-A4T14 genotypes were determined in 582 lung cancer patients and 582 healthy age- and gender-matched control subjects. Compared with the GC/GC genotype, the GC/AT and the AT/AT genotypes were not significantly associated with the risk of lung cancer [adjusted odds ratio (OR) = 1.08, 95% confidence interval (CI) = 0.84-1.38; and adjusted OR = 1.37, 95% CI = 0.83-2.24, respectively]. In addition, the risk estimate for the combined variant genotype (GC/AT + AT/AT) was similar to that of the GC/GC genotype (a dominant model for the AT allele, adjusted OR = 1.12, 95% CI = 0.88-1.41). These results suggest that the p73 G4C14-to-A4T14 polymorphism does not significantly affect susceptibility to lung cancer in the Korean population.

Combined effects of p73 and MDM2 polymorphisms on the risk of lung cancer

p73, a structural and functional homologue of p53, plays an important role in modulating cell-cycle control and apoptosis. MDM2 represses the transcriptional activity of p73 and thus attenuates its activity. Based on the interaction between p73 and MDM2 in cell-cycle control and apoptosis, we investigated the association between p73 G4C14-to-A4T14 and MDM2 309T > G polymorphisms, alone and in combination, on the risk of lung cancer in a Korean population. The p73 and MDM2 genotypes were determined in 582 lung cancer patients and in 582 healthy control subjects who were frequency-matched for age and gender. The p73 AT/AT and MDM2 309 GG genotypes were associated with a nonsignificant increased risk of lung cancer (adjusted odds ratio [OR] = 1.37, 95% confidence interval [CI] = 0.83-2.24; and adjusted OR = 1.29, 95% CI = 0.92-1.80, respectively), compared with their wild-type genotypes, respectively. When the p73 and MDM2 polymorphisms were combined, the risk of lung cancer increased in a dose-dependent manner as the number of variant alleles increased (Ptrend = 0.01). Subjects with three or four variant alleles were at a significantly increased risk of lung cancer (adjusted OR = 1.74, 95% CI = 1.11-2.74, P = 0.02) compared to subjects with zero variant allele. These results suggest an additive effect of the p73 and MDM2 variant alleles on an increased risk of lung cancer.

Lung cancer risk prediction: a tool for early detection

Although 45% of men and 39% of women will be diagnosed with cancer in their lifetime, it is difficult to predict which individuals will be affected. For some cancers, substantial progress in individual risk estimation has already been made. However, relatively few models have been developed to predict lung cancer risk beyond effects of age and smoking. This paper reviews published models for lung cancer risk prediction, discusses their potential contribution to clinical and research settings and suggests improvements to the risk modeling strategy for lung cancer. The sensitivity and specificity of existing cancer risk models is less than optimal. Improvement in individual risk prediction is important for selection of individuals for prevention or early detection interventions. In addition to smoking, factors related to occupational exposure, personal medical history and family history of cancer can add to the predictive power. A good risk prediction model is one that can identify a small fraction of the population in which a large proportion of the disease cases will occur. In the future, genetic and other biological markers are likely to be useful, although they will require rigorous evaluation. Validation is essential to establish the predictive effect and for ongoing monitoring of the model's continued relevance.

TSP1 and MMP9 genetic variants in sporadic prostate cancer

Angiogenesis plays an important role in the initiation and progression of many malignancies including prostate cancer (PCa). Therefore, genes implicated in angiogenic pathways could be susceptibility candidate genes for this malignancy. In this respect, we investigated the impact of functional genetic variants of TSP1 (N700S) and MMP9 (-1562 C/T) genes on the development and progression of PCa. This case-control study included 101 PCa patients and 106 healthy controls analyzed by polymerase chain reaction -restriction fragment length polymorphism assay. No association was observed between any of the TSP1 genotypes and PCa risk or severity; however, subjects carrying one copy of the MMP9 T allele exhibited threefold higher risk of developing PCa (OR = 2.86; P = 0.004). Regarding prognostic value, a significant association was found between the occurrence of the MMP9 T allele and the high-grade tumor (OR = 3.21; P = 0.004) and the advanced disease (OR = 2.47; P = 0.026). We also analyzed the effect of the combined genotypes on PCa risk. The patients with two high-risk genotypes exhibited 2.8-fold higher risk of developing PCa than those with only low-risk genotypes, but the association was not statistically significant. These findings suggest that MMP9 polymorphism is an independent risk factor of PCa development and aggressiveness.

GSTM1 and TNF-alpha gene polymorphisms and relations between blood lead and inflammatory markers in a non-occupational population

Inflammation is known to be an important underlying condition in the development of a variety of diseases. To investigate whether blood lead induces inflammatory reactions in non-occupationally exposed adults and the effects of genetic susceptibility associated with GSTM1 and TNF-alpha gene polymorphisms on this inflammatory response, we measured blood lead levels in 300 healthy university students. Total serum TNF-alpha and IL-6 levels and WBC counts were determined to evaluate the inflammatory response. Allelic loss of GSTM1 and the TNF-alpha-308 G>A polymorphism were determined by PCR and RFLP. Positive relations between blood lead and three inflammation biomarkers were shown in male subjects with blood lead > or =2.51microg/dl (median value) (TNF-alpha, p=0.015; IL-6, p=0.082; and WBC, p=0.044). However, subgroup analysis by genotype showed an effect of blood lead on the three biomarkers only in individuals with the GSTM1 null (TNF-alpha, p=0.020; IL-6, p=0.096; and WBC, p=0.017) or TNF-alpha GG (TNF-alpha, p=0.017; IL-6, p=0.088; and WBC, p=0.095) genotype, and not in individuals with GSTM1 present (all three inflammatory biomarkers, p>0.1) or the TNF-alpha GA or AA (all three biomarkers, p>0.1) genotype. These results suggest that blood lead affects the inflammatory response and that GSTM1 and TNF-alpha gene polymorphisms are genetic factors associated with lead-induced inflammatory response.

Polymorphisms in the caspase-8 gene and the risk of lung cancer

Caspase-8 (CASP-8) is an initiator CASP in the cell death receptor-mediated apoptotic pathway, and plays an important role in the development of cancer. Polymorphisms and their haplotypes in the CASP-8 gene can result in alterations in CASP-8 expression and/or activity, thereby modulating the susceptibility to lung cancer. To test this hypothesis, we examined the association of -678_-673delAGTAAG (-678del) and IVS12-19G-->A polymorphisms and their haplotypes with the risk of lung cancer in a Korean population. The CASP-8 genotypes were determined in 432 lung cancer patients and 432 healthy age- and gender-matched control subjects. The distributions of the CASP-8 -678del and IVS12-19G-->A genotypes were not significantly different between the overall lung cancer cases and the controls. When the cases were categorized by tumor histology, however, the IVS12-19 AA genotype and the combined IVS12-19 GA + AA genotype were associated with a significantly decreased risk of small cell carcinoma (SmCC) compared with the IVS12-19 GG genotype [adjusted odds ratio (OR) = 0.14, 95% confidence interval (CI) = 0.03-0.64, P = 0.01; and adjusted OR = 0.56, 95% CI = 0.33-0.96, P = 0.03, respectively]. Consistent with the genotyping analyses, the -678del-/IVS12-19A haplotype containing 94% of the IVS12-19A allele in the study population was associated with a significantly decreased risk of SmCC compared with the -678del-/IVS12-19G (adjusted OR = 0.58, 95% CI = 0.36-0.93, P = 0.023, and Pc = 0.046). These findings suggest that the CASP-8 gene may contribute to an inherited predisposition to SmCC of the lung.

Polymorphisms in the FAS and FASL genes and risk of lung cancer in a Korean population

BACKGROUND

The FAS and FASL system play an important role in regulating extrinsic apoptotic pathway and inappropriate regulation of this signaling pathway contributes to lung tumorigenesis. Polymorphisms in the promoter region of the FAS (-1377G>A and -670A>G) and FASL (-844C>T) have been shown to alter the transcriptional activities of these genes. In order to evaluate the contribution of these polymorphisms to the risk of lung cancer, we carried out a case-control study in a Korean population.

METHODS

The FAS and FASL genotypes were determined in 582 lung cancer patients and 582 healthy control subjects who were frequency-matched for age and gender.

RESULTS

The FAS and FASL genotypes and the FAS haplotypes exhibited no apparent relationship with the risk of lung cancer. In addition, there was no significant interaction between the FAS and FASL polymorphisms in the development of lung cancer.

CONCLUSION

These results suggest that the FAS-1377G>A and -670A>G and FASL-844C>T polymorphisms do not significantly affect the susceptibility to lung cancer in Koreans.

MDM2 309T>G polymorphism and risk of lung cancer in a Korean population

BACKGROUND

The MDM2 protein plays an important role in regulating cell proliferation and apoptosis by interaction with multiple proteins including p53 and Rb. A polymorphism (309T>G) in the MDM2 promoter has been shown to result in higher levels of MDM2 RNA and protein. In order to evaluate the association of the MDM2 309T>G polymorphism and lung cancer risk, we carried out a case-control study in a Korean population.

METHODS

The MDM2 genotypes were determined in 582 lung cancer patients and in 582 healthy control subjects who were frequency matched for age and gender.

RESULTS

The distribution of the MDM2 309T>G genotypes was not significantly different between overall lung cancer cases and controls. However, when the cases were categorized by tumor histology, the 309GG genotype was associated with a significantly increased risk of adenocarcinoma (adjusted OR=1.91, 95% CI=1.16-3.14, P=0.01) compared to the 309TT genotype. In addition, the risk of adenocarcinoma increased as the number of 309G alleles increased (P(trend)=0.01).

CONCLUSION

Our findings suggest that the MDM2 309T>G polymorphism may be used as a marker for genetic susceptibility to adenocarcinoma of the lung.

Association of VEGF genetic polymorphisms with prostate carcinoma risk and clinical outcome

OBJECTIVES

Vascular endothelial growth factor (VEGF) is a potent stimulus of angiogenesis that has an important role in many human malignancies including prostate carcinoma (PCa). We evaluated the role of the functional VEGF polymorphisms as genetic markers for PCa susceptibility and prognosis.

METHODS

The study included 101 patients with PCa and [corrected] 100 age-matched healthy men. The VEGF genotypes -1154G>A were identified by allele-specific polymerase chain reaction (AS-PCR) and the genotypes -634G>C and 936C>T were identified by restriction fragment length polymorphism-polymerase chain reaction (RFLP-PCR).

RESULTS

A negative association was found between VEGF -1154AA genotype and PCa risk (OR=0.27; P=0.009). Furthermore, the presence of the VEGF -1154A allele appeared to be associated with a decreased [corrected] risk of higher tumor grade (OR=0.37; P=0.01). A significant increased risk of prostate cancer was associated with the VEGF -634 (GC+CC) combined genotype (OR=1.95; P=0.02). The VEGF -634C allele was associated with the aggressive phenotype of prostate cancer as defined by the high histological grade (OR=3.48; P=0.007). The VEGF -1154A/-634G haplotype was negatively associated with PCa risk (OR=0.48; P=0.005) and high tumor grade compared to low grade (OR=0.37; P=0.02).

CONCLUSIONS

Genetic variations in the VEGF may predict not only PCa risk but also tumor aggressiveness.

Association of a functional polymorphism in the promoter of the MDM2 gene with risk of nonsmall cell lung cancer

Lung cancer is the leading cause of cancer mortality in the world. Although exposure to carcinogens is considered to be the main cause, genetic variation may contribute to lung cancer risk. Murine double minute 2, MDM2, is a key regulator of p53 activity and recently a polymorphism in the promoter region of the MDM2 gene was characterized. This single nucleotide polymorphism, SNP309, was shown to influence MDM2 transcription, MDM2 protein levels and p53 activity. The aim of this study was to investigate whether this functionally important SNP is associated with risk of nonsmall cell lung cancer. The study consisted of 341 nonsmall cell lung cancer cases and 412 healthy controls of Norwegian origin. Our results indicate that the G/G genotype of SNP309 is associated with lung cancer risk with an odds ratio of 1.62 (95% CI: 1.06-2.50). Interestingly, the strongest effect of the polymorphism was seen among women. Females homozygous for SNP309 G/G had associated odds ratio 4.06 (1.29-12.8). We also explored the MDM2 SNP309 in relation to TP53 gene mutations and age at nonsmall cell lung cancer diagnosis. Our results indicate that the G/G genotype of SNP309 is associated with higher age at diagnosis in individuals with TP53 mutations (p=0.037).

DNA sequence context affects repair of the tobacco-specific adduct O(6)-[4-Oxo-4-(3-pyridyl)butyl]guanine by human O(6)-alkylguanine-DNA alkyltransferases

The repair protein O(6)-alkylguanine-DNA alkyltransferase (AGT) protects cells from the mutagenic and carcinogenic effects of alkylating agents by removing O(6)-alkylguanine adducts from DNA. Recently, we established that AGT protects against the mutagenic effects of pyridyloxobutylation resulting from the metabolic activation of the tobacco-specific nitrosamines (TSNA) 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone and N-nitrosonornicotine by repairing O(6)-[4-oxo-4-(3-pyridyl)butyl]guanine (O(6)-pobG). There have been several epidemiologic studies examining the association between the I143V/K178R AGT genotype and lung cancer risk. Two studies have found positive associations, suggesting that AGT proteins differ in their repair of DNA damage caused by TSNA. However, it is not known how this genotype alters the biochemical activity of AGT. We proposed that AGT proteins may differ in their ability to remove large O(6)-alkylguanine adducts, such as O(6)-pobG, from DNA. Therefore, we examined the repair of O(6)-pobG by wild-type (WT) human, I143V/K178R, and L84F AGT proteins when contained in multiple sequence contexts, including the twelfth codon of H-ras, a mutational hotspot within this oncogene. The AGT-mediated repair of O(6)-pobG was more profoundly influenced by sequence context than that of O(6)-methylguanine. These differences are not the result of secondary structure (hairpin) formation in DNA. In addition, the I143V/K178R variant seems less sensitive to the effects of sequence context than the WT or L84F proteins. These studies indicate that the sequence dependence of O(6)-pobG repair by human AGT (hAGT) varies with subtle changes in protein structure. These data establish a novel functional difference between the I143V/K178R protein and other hAGTs in the repair of a toxicologically relevant substrate, O(6)-pobG.

Glu346Lys Polymorphism in the Methyl-CpG Binding Domain 4 Gene and the Risk of Primary Lung Cancer

BACKGROUND

Methyl-CpG binding domain 4 (MBD4) protein functions as a DNA repair enzyme and minimizes mutations at 5-methylcytosine. Polymorphisms in the DNA repair gene MBD4 may be associated with differences in DNA repair capacity and thereby influence an individual's susceptibility to lung cancer. To test this hypothesis, we examined the potential association between the MBD4 Glu346Lys polymorphism and the risk of lung cancer in a Korean population.

METHODS

The MBD4 Glu346Lys genotypes were determined in 432 lung cancer patients and 432 healthy age- and gender-matched control subjects.

RESULTS

The distribution of the MBD4 Glu346Lys genotypes was not significantly different between the overall lung cancer cases and the controls. However, when the cases were categorized by tumor histology, the Lys346Lys genotype was associated with a significantly decreased risk of adenocarcinoma (AC) as compared with the Glu346Glu genotype [adjusted odds ratio (OR) = 0.50, 95% confidence interval (CI) = 0.26-0.97, P = 0.04]. On the stratification analysis, the protective effect of the Lys346Lys genotype against AC was statistically significant in older individuals and heavier smokers (adjusted OR = 0.08, 95% CI = 0.01-0.64, P = 0.02; and adjusted OR = 0.09, 95% CI = 0.01-0.72, P = 0.02, respectively).

CONCLUSIONS

Our findings suggest that the MBD4 Glu346Lys polymorphism could be used as a marker for genetic susceptibility to AC of the lung.

Germline genetic polymorphisms of CYP1A1, GSTM1 and GSTT1 genes in Indian cervical cancer: Associations with tumor progression, age and human papillomavirus infection

OBJECTIVES

Host genetic factors may play a role in human papillomavirus (HPV)-associated tumorigenesis, although the issue continues to be a focus of much debate. Biotransformation is critical in carcinogenic activity of numerous environmental carcinogens. It is therefore possible that polymorphisms of genes producing functional changes in xenobiotic metabolizing enzymes may be susceptible factors in cervical carcinogenesis. This study looked into possible relationships among these factors.

METHODS

In this case-control study, we analyzed leukocyte DNA from a total of 312 subjects for germline polymorphisms of CYP1A1 (m1 and m2), GSTM1 and GSTT1 at various stages of the cervical tumor progression spectrum, using PCR and RFLP.

RESULTS

Both m1 and m2 polymorphisms of the CYP1A1 gene were more frequent among cases (36.1% for m1 and 38.1% for m2) compared to control subjects (18.2% and 17.6% respectively). The odds ratio of a subject with homozygous CYP1A1 m1 and m2 variant being a case was highest (m1 OR = 4.77 [95% CI = 1.28-17.77]; P = 0.02 and m2 OR = 5.48 [95% CI = 1.49-20.19]; P = 0.011) respectively. The distribution of m1 and m2 CYP1A1 genotypes was also studied as a function of age and in relation to the presence of HPV 16 infection. The risk due to CYP1A1 m1 genotype, when adjusted for HPV status, showed a significantly increased risk (OR = 3.58, 95% CI = 1.88-6.81; P = 0.0001). Similar results were observed in the case of CYP1A1 m2 variant and HPV 16. There was a significant over-representation of both m1 (25.9% vs. 13.9%) and m2 (27.9% vs. 13.3%) polymorphisms in older women (46 years or more). GSTM1 and GSTT1 deletions were also prominent among cases (53.7% and 16.3% respectively) compared to controls (32.7% and 9.7% respectively). A higher proportion of both GSTT1 and GSTM1 deletions were also detected in HPV-16-positive subjects.

CONCLUSIONS

These results suggest that polymorphisms in the CYP1A1, GSTM1 and GSTT1 genes may render women more susceptible to the development of cervical cancer. The association between this susceptibility and the presence of human papillomavirus infection further emphasizes the significance of the genetic polymorphisms.

Caspase 9 promoter polymorphisms and risk of primary lung cancer

Caspase-9 (CASP-9) is an initiator CASP in the apoptosome-driven apoptosis pathway and plays an important role in the development and progression of cancer. Polymorphisms in the promoter region of the CASP-9 gene may influence the promoter activity of this gene, thereby modulating susceptibility to lung cancer. To test this hypothesis, we examined the association of four polymorphisms [-1263A>G, -905T>G, -712C>T and -293_-275delCGTGAGGTCAGTGCGGGGA (-293del)] in the CASP-9 promoter with the risk of lung cancer in a Korean population. The CASP-9 genotypes were determined in 432 lung cancer patients and 432 healthy controls that were frequency-matched for age and gender. The -1263 GG genotype was associated with a significantly decreased risk of lung cancer compared with the -1263 AA genotype or combined -1263 AA+AG genotype [adjusted odds ratio (OR)=0.64, 95% confidence interval (95% CI)=0.42-0.98, P=0.04 and adjusted OR=0.67, 95% CI=0.46-0.97, P=0.01, respectively]. For the -712C>T polymorphism, individuals with at least one -712T allele were at a significantly increased risk of lung cancer compared with those harboring the -712 CC genotype (adjusted OR=1.42, 95% CI=1.06-1.89, P=0.02). Consistent with the results of genotype analyses, the -1263G/-712C (G-C) haplotype was associated with a significantly decreased risk of lung cancer [adjusted OR=0.59, 95% CI=0.47-0.75, P and Bonferroni corrected P (Pc)<0.001]. Moreover, the risk of lung cancer decreased in a dose-dependent manner as the number of the G-C haplotypes increased (adjusted OR=0.60, 95% CI=0.45-0.81, P=0.0007 and Pc=0.0014 for the G-C heterozygotes and adjusted OR=0.34, 95% CI=0.17-0.68, P=0.0023 and Pc=0.0046 for the G-C homozygotes; P(trend)<0.001). The promoter assay revealed the G-C haplotype to have a significantly higher promoter activity than the -1263G/-712T and -1263A/-712C haplotypes. These results suggest that CASP-9 promoter polymorphisms affect CASP-9 expression and contribute to genetic susceptibility to lung cancer.

O6-alkylguanine-DNA alkyltransferase gene polymorphisms and the risk of primary lung cancer

O6-alkylguanine-DNA alkyltransferase (AGT) plays an important role in the repair of O6-alkylguanine adducts, which are major mutagenic lesions produced by environmental carcinogens. Polymorphisms in the AGT gene may affect the capacity to repair DNA damage and thereby have influence on individual's susceptibility to smoking-related cancer. To test this hypothesis, we investigated the potential association of AGT polymorphisms (485C > A, Leu53Leu (C > T) and Leu84Phe] with the risk of lung cancer in a Korean population. The AGT genotypes were determined in 432 lung cancer patients and in 432 healthy controls who were frequency-matched for age and gender. The 485 AA genotype was associated with a significantly increased risk for overall lung cancer as compared with the 485 CC genotype and the combined 485 CC + CA genotype, respectively (adjusted odds ratio (OR) = 1.83, 95% confidence interval (CI) = 1.12-2.99, P = 0.02, and Bonferroni corrected P-value (Pc) = 0.04; and adjusted OR = 1.67, 95% CI = 1.05-2.66, P = 0.03, respectively). When the lung cancer cases were categorized by the tumor histology, the 485 AA genotype was associated with a significantly increased risk of adenocarcinoma (AC) and small cell carcinoma (SmCC), respectively, as compared with the combined 485 CC + CA genotype (adjusted OR = 2.54, 95% CI = 1.39-4.66, P = 0.003; and adjusted OR = 2.19, 95% CI = 1.06-4.55, P = 0.04, respectively). However, the genotype distributions of the Leu53Leu and Leu84Phe polymorphisms were not significantly different between the lung cancer cases and the controls. On a promoter assay, the 485C > A polymorphism did not have an effect on the promoter activity of the AGT gene. These results suggest that the effect of the AGT 485C > A polymorphism on the risk of lung cancer may be secondary to linkage disequilibrium (LD) with either another AGT variant or with a true susceptibility gene, and that the AGT 485C > A polymorphism could be used as a marker for the genetic susceptibility to lung cancer.

Polymorphisms in the hMSH2 Gene and the Risk of Primary Lung Cancer

Polymorphisms in the DNA repair genes may be associated with differences in the capacity to repair DNA damage, and so this can influence an individual's susceptibility to lung cancer. To test this hypothesis, we investigated the association of hMSH2 -118T>C, IVS1+9G>C, IVS10+12A>G, and IVS12-6T>C genotypes and their haplotypes with the risk of lung cancer in a Korean population. The hMSH2 genotypes were determined in 432 lung cancer patients and in 432 healthy controls who were frequency matched for age and gender. The hMSH2 haplotypes were estimated based on a Bayesian algorithm using the Phase program. The presence of at least one IVS10+12G allele was associated with a significantly decreased risk of adenocarcinoma, as compared with the IVS10+12AA genotype [adjusted odds ratio (OR), 0.59; 95% confidence interval (95% CI), 0.40-0.88; P = 0.01], and the presence of at least one IVS12-6C allele was associated with a significantly increased risk of adenocarcinoma, as compared with the IVS12-6TT genotype (adjusted OR, 1.52; 95% CI, 1.02-2.27; P = 0.04). Consistent with the results of the genotyping analysis, the TGGT haplotype with no risk allele was associated with a significantly decreased risk of adenocarcinoma, as compared with the TCAC haplotype with two risk allele [i.e., IVS10+12A and IVS12-6C allele; adjusted OR, 0.49; 95% CI, 0.30-0.78; P = 0.003 and P(c) (Bonferroni corrected P value) = 0.012]. The effect of the hMSH2 haplotypes on the risk of adenocarcinoma was statistically significant in the never smokers and younger individuals (adjusted OR, 0.45; 95% CI, 0.27-0.75; P = 0.002 and P(c) = 0.004; and adjusted OR, 0.44; 95% CI, 0.23-0.85; P = 0.014 and P(c) = 0.028, respectively) but not in the ever-smokers and older individuals. These results suggest that the hMSH2 polymorphisms and their haplotypes may be an important genetic determinant of adenocarcinoma of the lung, particularly in never smokers.

Gene-gene, gene-environment & multiple interactions in colorectal cancer

This review comprehensively evaluates the influence of gene-gene, gene-environment and multiple interactions on the risk of colorectal cancer (CRC). Methods of studying these interactions and their limitations have been discussed herein. There is a need to develop biomarkers of exposure and of risk that are sensitive, specific, present in the pathway of the disease, and that have been clinically tested for routine use. The influence of inherited variation (polymorphism) in several genes has been discussed in this review; however, due to study limitations and confounders, it is difficult to conclude which ones are associated with the highest risk (either individually or in combination with environmental factors) to CRC. The majority of the sporadic cancer is believed to be due to modification of mutation risk by other genetic and/or environmental factors. Micronutrient deficiency may explain the association between low consumption of fruit/vegetables and CRC in human studies. Mitochondrial modulation by dietary factors influences the balance between cell renewal and death critical in colon mucosal homeostasis. Both genetic and epigenetic interactions are intricately dependent on each other, and collectively influence the process of colorectal tumorigenesis. The genetic and environmental interactions present a good prospect and a challenge for prevention strategies for CRC because they support the view that this highly prevalent cancer is preventable.

Relationship between cyclooxygenase 8473T>C polymorphism and the risk of lung cancer: a case-control study

BACKGROUND

Cyclooxygenase-2 (COX-2) plays an important role in the development of lung cancer. DNA sequence variations in the COX-2 gene may lead to altered COX-2 production and/or activity, and so they cause inter-individual differences in the susceptibility to lung cancer. To test this hypothesis, we investigated the association between the 8473T>C polymorphism in the 3'-untranslated region of the COX-2 gene and the risk of lung cancer in a Korean population.

METHODS

The COX-2 genotypes were determined using PCR-based primer-introduced restriction analysis in 582 lung cancer patients and in 582 healthy controls that were frequency-matched for age and gender.

RESULTS

The distribution of the COX-2 8473T>C genotypes was not significantly different between the overall lung cancer cases and the controls. However, when the cases were categorized by the tumor histology, the combined 8473 TC + CC genotype was associated with a significantly decreased risk of adenocarcinoma as compared with the 8473 TT genotype (adjusted OR = 0.64; 95% CI = 0.46-0.90, P = 0.01). On the stratification analysis, the protective effect of the combined 8473 TC + CC genotype against adenocarcinoma was statistically significant in the males, older individuals and ever-smokers (adjusted OR = 0.59; 95% CI = 0.39-0.91, P = 0.02; adjusted OR = 0.55; 95% CI = 0.33-0.93, P = 0.03; and adjusted OR = 0.57; 95% CI = 0.37-0.87, P = 0.01, respectively).

CONCLUSION

These findings suggest that the COX-2 8473T>C polymorphism could be used as a marker for the genetic susceptibility to adenocarcinoma of the lung.

Bladder cancer predisposition: a multigenic approach to DNA-repair and cell-cycle-control genes

The candidate-gene approach in association studies of polygenic diseases has often yielded conflicting results. In this hospital-based case-control study with 696 white patients newly diagnosed with bladder cancer and 629 unaffected white controls, we applied a multigenic approach to examine the associations with bladder cancer risk of a comprehensive panel of 44 selected polymorphisms in two pathways, DNA repair and cell-cycle control, and to evaluate higher-order gene-gene interactions, using classification and regression tree (CART) analysis. Individually, only XPD Asp312Asn, RAG1 Lys820Arg, and a p53 intronic SNP exhibited statistically significant main effects. However, we found a significant gene-dosage effect for increasing numbers of potential high-risk alleles in DNA-repair and cell-cycle pathways separately and combined. For the nucleotide-excision repair pathway, compared with the referent group (fewer than four adverse alleles), individuals with four (odds ratio [OR] = 1.52, 95% CI 1.05-2.20), five to six (OR = 1.81, 95% CI 1.31-2.50), and seven or more adverse alleles (OR = 2.50, 95% CI 1.69-3.70) had increasingly elevated risks of bladder cancer (P for trend <.001). Each additional adverse allele was associated with a 1.21-fold increase in risk (95% CI 1.12-1.29). For the combined analysis of DNA-repair and cell-cycle SNPs, compared with the referent group (<13 adverse alleles), the ORs for individuals with 13-15, 16-17, and >or=18 adverse alleles were 1.22 (95% CI 0.84-1.76), 1.57 (95% CI 1.05-2.35), and 1.77 (95% CI 1.19-2.63), respectively (P for trend = .002). Each additional high-risk allele was associated with a 1.07-fold significant increase in risk. In addition, we found that smoking had a significant multiplicative interaction with SNPs in the combined DNA-repair and cell-cycle-control pathways (P<.01). All genetic effects were evident only in "ever smokers" (persons who had smoked >or=100 cigarettes) and not in "never smokers." A cross-validation statistical method developed in this study confirmed the above observations. CART analysis revealed potential higher-order gene-gene and gene-smoking interactions and categorized a few higher-risk subgroups for bladder cancer. Moreover, subgroups identified with higher cancer risk also exhibited higher levels of induced genetic damage than did subgroups with lower risk. There was a significant trend of higher numbers of bleomycin- and benzo[a]pyrene diol-epoxide (BPDE)-induced chromatid breaks (by mutagen-sensitivity assay) and DNA damage (by comet assay) for individuals in higher-risk subgroups among cases of bladder cancer in smokers. The P for the trend was .0348 for bleomycin-induced chromosome breaks, .0036 for BPDE-induced chromosome breaks, and .0397 for BPDE-induced DNA damage, indicating that these higher-order gene-gene and gene-smoking interactions included SNPs that modulated repair and resulted in diminished DNA-repair capacity. Thus, genotype/phenotype analyses support findings from CART analyses. This is the first comprehensive study to use a multigenic analysis for bladder cancer, and the data suggest that individuals with a higher number of genetic variations in DNA-repair and cell-cycle-control genes are at an increased risk for bladder cancer, confirming the importance of taking a multigenic pathway-based approach to risk assessment.

Methylenetetrahydrofolate reductase 677C/T gene polymorphism, gastric cancer susceptibility and genomic DNA hypomethylation in an at-risk Italian population

We performed a case-control study to examine the relationship between MTHFR C677T gene polymorphism (MTHFR677C/T) and gastric cancer susceptibility in at-risk populations in central Italy. To explore genomic DNA hypomethylation as a potential etiologic mechanism, this phenomenon was evaluated in carriers of the MTHFR677T/T genotype and carriers of the wild-type MTHFR677C/C genotype. Lymphocyte genomic DNA from 162 gastric cancer patients and 164 controls was used for MTHFR677C/T genotyping. Unconditional regression analysis with ORs and 95% CIs was used to investigate the association of the polymorphism with disease. Genomic DNA methylation status by an established enzymatic assay that measures the DNA accepting capacity of methyl groups (inversely related to endogenous methylation) was assessed in a random sample of 40 carriers of the wild-type MTHFR677C/C genotype and 40 carriers of the MTHFR677T/T genotype. The global allelic distribution was in Hardy-Weinberg equilibrium. The MTHFR677T allele was significantly associated with gastric cancer risk with an OR of 2.49 (95% CI 1.48-4.20) in heterozygous MTHFR677C/T carriers and an OR of 2.85 (95% CI 1.52-5.35) in homozygous MTHFR677T/T carriers. This risk association was retained in subgroup analyses by tumor histotype and location. Genomic DNA hypomethylation status in MTHFR677T/T carriers was significantly higher than in subjects with wild-type MTHF677C/C genotype (p = 0.012). In the studied population, MTHFR677T played the role of a moderate-penetrance gastric cancer susceptibility allele. Possession of the MTHFR677T/T genotype was significantly associated with genomic DNA hypomethylation. These findings deserve further investigation in the context of novel strategies for gastric cancer prevention.

Less efficient g2-m checkpoint is associated with an increased risk of lung cancer in African Americans

Cell cycle checkpoints play critical roles in the maintenance of genomic integrity. The inactivation of checkpoint genes by genetic and epigenetic mechanisms is frequent in all cancer types, as a less-efficient cell cycle control can lead to genetic instability and tumorigenesis. In an on-going case-control study consisting of 216 patients with non-small cell lung cancer, 226 population-based controls, and 114 hospital-based controls, we investigated the relationship of gamma-radiation-induced G2-M arrest and lung cancer risk. Peripheral blood lymphocytes were cultured for 90 hours, exposed to 1.0 Gy gamma-radiation, and harvested at 3 hours after gamma-radiation treatment. gamma-Radiation-induced G2-M arrest was measured as the percentage of mitotic cells in untreated cultures minus the percentage of mitotic cells in gamma-radiation-treated cultures from the same subject. The mean percentage of gamma-radiation-induced G2-M arrest was significantly lower in cases than in population controls (1.18 versus 1.44, P < 0.01) and hospital controls (1.18 versus 1.40, P = 0.01). When dichotomized at the 50th percentile value in combined controls (population and hospital controls), a lower level of gamma-radiation-induced G2-M arrest was associated with an increased risk of lung cancer among African Americans after adjusting for baseline mitotic index, age, gender, and pack-years of smoking [adjusted odd ratio (OR), 2.25; 95% confidence interval (95% CI), 0.97-5.20]. A significant trend of an increased risk of lung cancer with a decreased level of G2-M arrest was observed (P(trend) = 0.02) among African Americans, with a lowest-versus-highest quartile adjusted OR of 3.74 (95% CI, 0.98-14.3). This trend was most apparent among African American females (P(trend) < 0.01), with a lowest-versus-highest quartile adjusted OR of 11.75 (95% CI, 1.47-94.04). The results suggest that a less-efficient DNA damage-induced G2-M checkpoint is associated with an increased risk of lung cancer among African Americans. Interestingly, we observed a stronger association of DNA damage-induced G2-M arrest and lung cancer among African Americans when compared with Caucasians. If replicated, these results may provide clues to the exceedingly high lung cancer incidence experienced by African Americans.

MnSOD Val-9Ala Genotype, Pro- and Anti-oxidant Environmental Modifiers, and Breast Cancer Among Women on Long Island, New York

Excessive oxidative stress may induce and promote breast carcinogenesis. Manganese superoxide dismutase (MnSOD) is critical to management of oxidative stress by catalyzing the formation of hydrogen peroxide from two superoxide anions. To examine the relationship between MnSOD Val-9Ala polymorphism, breast cancer and potential modifiers, we analyzed data from a large population-based case-control study. Study participants completed an in-home interviewer-administered questionnaire, and self-completed a Block food frequency questionnaire. Age-adjusted unconditional logistic models included 1034 cases and 1084 controls. As compared with Val/Val genotype, we found no association between MnSOD Ala/Val (OR = 0.98, 95% CI: 0.79-1.21) and Ala/Ala (OR = 1.00, 95% CI: 0.79-1.28) genotypes and breast cancer. Results did not differ by menopausal status, stage of tumor, or estrogen and progesterone receptor status. No discernable patterns of interaction were found between this MnSOD variant and anti-oxidative exposures, including fruit and vegetable intake or NSAID use, or pro-oxidant exposures, including smoking and alcohol. This study provides little evidence that variation in Val-9Ala polymorphism of MnSOD alone or through substantial interaction with key exposures believed to be pro- or anti-oxidant properties influences breast cancer risk.

Polymorphisms of DNA repair genes XRCC1 and XRCC3, interaction with environmental exposure and risk of chronic gastritis and gastric cancer

AIM

To evaluate the association between polymorphisms XRCC1 Arg194Trp and Arg399Gln and XRCC3 Thr241Met and the risk for chronic gastritis and gastric cancer, in a Southeastern Brazilian population.

METHODS

Genotyping by PCR-RFLP was carried out on 202 patients with chronic gastritis (CG) and 160 patients with gastric cancer (GC), matched to 202 (C1) and 150 (C2) controls, respectively.

RESULTS

No differences were observed among the studied groups with regard to the genotype distribution of XRCC1 codons 194 and 399 and of XRCC3 codon 241. However, the combined analyses of the three variant alleles (194Trp, 399Gln and 241Met) showed an increased risk for chronic gastritis when compared to the GC group. Moreover, an interaction between the polymorphic alleles and demographic and environmental factors was observed in the CG and GC groups. XRCC1 194Trp was associated with smoking in the CG group, while the variant alleles XRCC1 399Gln and XRCC3 241Met were related with gender, smoking, drinking and H pylori infection in the CG and GC groups.

CONCLUSION

Our results showed no evidence of a relationship between the polymorphisms XRCC1 Arg194Trp and Arg399Gln and XRCC3 Thr241Met and the risk of chronic gastritis and gastric cancer in the Brazilian population, but the combined effect of these variants may interact to increase the risk for chronic gastritis, considered a premalignant lesion. Our data also indicate a gene-environment interaction in the susceptibility to chronic gastritis and gastric cancer.

A promoter polymorphism (-77T>C) of DNA repair gene XRCC1 is associated with risk of lung cancer in relation to tobacco smoking

X-ray repair cross complementing group 1 (XRCC1) is one of the major DNA repair proteins involved in the base-excision repair pathway. Functional Polymorphisms in the XRCC1 gene may lead to decreased DNA repair capacity and thus confer inherited predisposition to cancer risk. In this case-control study of 710 patients with incident lung cancer and 710 cancer-free controls who were frequency matched on age, sex and residential area, we genotyped a novel T>C transition at the promoter region (-77T>C) of XRCC1 and other two common non-synonymous polymorphisms (Arg194Trp and Arg399Gln) to determine their associations with risk of lung cancer. We found that compared with the -77TT wild-type homozygote, the variant genotypes were associated with significantly increased risk of lung cancer [adjusted odds ratio (OR)=1.51; 95% confidence interval (CI)=1.17-1.94 for -77TC; OR=2.98; 95% CI=0.93-9.59 for -77CC; and OR=1.55; 95% CI=1.21-1.98 for -77TC/CC]. By contrast, no significant associations were observed between the other two exonic variants (Arg194Trp and Arg399Gln) and lung cancer risk. Furthermore, we observed a 9.82-fold increased risk (95% CI=5.66-17.02) for heavy smokers carrying the -77C variant (-77TC/CC) and a 4.07-fold increased risk (95% CI=2.85-5.81) for heavy smokers not carrying the variant. However, the interaction between the -77T>C variant and cumulative smoking was not statistically significant (P=0.1560). These findings indicate that the new XRCC1 -77T>C polymorphism may contribute to the aetiology of lung cancer. Further functional studies are warranted to elucidate the underlying molecular mechanisms of the association.

Biomonitoring of inhaled complex mixtures--ambient air, diesel exhaust and cigarette smoke

Human biomonitoring comprises the determination of biomarkers in body-fluids, cells and tissues. Biomarkers are generally assigned to one of three classes, namely, biomarkers of exposure, effect or susceptibility. Since biomarkers represent steps in an exposure-disease continuum, their application in epidemiological studies ('molecular epidemiology') shows promise. However, to be a predictor of disease, a biomarker has to be validated. Validation criteria for a biomarker include intrinsic qualities such as specificity, sensitivity, knowledge of background in the population, existence of dose-response relationships, degree of inter- and intra-individual variability, knowledge of the kinetics, confounding and modifying factors. In addition, properties of the sampling and analytical procedures are of relevance, including constraints and non-invasiveness of sampling, stability of sample as well as simplicity, high sensitivity, specificity and speed of the analytical method. It is of particular importance to prove by suitable studies that the biomarker of exposure indicates the actual exposure, the biomarker of effect strongly predicts the actual risk of disease and the biomarker of susceptibility actually modifies the risk. Biomonitoring of the exposure to complex mixtures such as polluted ambient air, diesel exhaust or tobacco smoke is a particular challenge since these exposures have many constituents in common and many people were exposed to more than one of these mixtures. Data on the exposure to polycyclic aromatic hydrocarbons (PAH) and benzene from ambient air, diesel exhaust and tobacco smoke will be presented. In addition, some source-specific biomarkers such as nitro-arenes and nicotine metabolites as well as their application in population groups will be discussed. The second part of the presentation addresses the application of biomarkers for assessing so called 'potentially reduced exposure products' (PREPs). According to a recent report of the Institute of Medicine (USA), "reducing risk of disease by reducing exposure to tobacco toxicants is feasible" and "surrogate biological markers that are associated with tobacco-related diseases could be used to offer guidance as to whether or not PREPs are likely to be risk-reducing." In general, the same validation criteria apply as discussed above. In addition, it is suggested that a panel of biomarkers should be used, representing both smoke phases (gas and particulate phase) and the various chemical classes of smoke constituents (e.g., carbonyls, benzene, PAH, tobacco-specific nitrosamines, aromatic amines). Also, a panel of biomarkers of effect should cover the major known adverse effects of smoking (e.g., oxidative stress, inflammatory processes, lipid peroxidation, lipometabolic disorders, mutagenic effects). Biomarkers of nicotine and carbon monoxide uptake are of interest for evaluating the smoking and inhalation behavior, respectively. Finally, suitable study designs for evaluating PREPs are discussed. It is concluded that suitable biomarkers for assessing the exposure to complex mixtures such as ambient air, diesel exhaust and tobacco smoke as well as for evaluating the exposure-reducing properties of PREPs are already available. Future efforts should focus on the development and validation of biomarkers of effect.