Search

Cullin-RING ubiquitin ligases (CRLs) responsible for substrate specificity of ubiquitination and play a key role in cell-cycle control and DNA damage response. In this study, we assessed associations between 16,599 SNPs in 115 CRL genes and lung cancer risk by using summary data of six published genome-wide association studies (GWASs) of 12,160 cases and 16,838 cases of European ancestry. As a result, we identified three independent SNPs in DCAF4 (rs117781739, rs12587742 and rs2240980) associated with lung cancer risk (odds ratio = 0.91, 1.09 and 1.09, respectively; 95% confidence interval = 0.88-0.95, 1.05-1.14 and 1.05-1.13, respectively; and P = 3.99×10-6, 4.97×10-5 and 1.44×10-5, respectively) after multiple comparison correction by a false discovery rate

Background: Analysis of candidate genes in individual studies has had only limited success in identifying particular gene variants that are conclusively associated with lung cancer risk. In the International Lung Cancer Consortium (ILCCO), we conducted a coordinated genotyping study of 10 common variants selected because of their prior evidence of an association with lung cancer. These variants belonged to candidate genes from different cancerrelated pathways including inflammation (IL1B), folate metabolism (MTHFR), regulatory function (AKAP9 and CAMKK1), cell adhesion (SEZL6) and apoptosis (FAS, FASL, TP53, TP53BP1 and BAT3). Methods: Genotype data from 15 ILCCO case-control studies were available for a total of 8431 lung cancer cases and 11 072 controls of European descent and Asian ethnic groups. Unconditional logistic regression was used to model the association between each variant and lung cancer risk. Results: Only the association between a non-synonymous variant of TP53BP1 (rs560191) and lung cancer risk was significant (OR = 0.91, P = 0.002). This association was more striking for squamous cell carcinoma (OR = 0.86, P = 6 × 10-4). No heterogeneity by center, ethnicity, smoking status, age group or sex was observed. In order to confirm this association, we included results for this variant from a set of independent studies (9966 cases/11 722 controls) and we reported similar results. When combining all these studies together, we reported an overall OR = 0.93 (0.89-0.97) (P = 0.001). This association was significant only for squamous cell carcinoma [OR = 0.89 (0.85-0.95), P = 1 × 10-4]. Conclusion: This study suggests that rs560191 is associated to lung cancer risk and further highlights the value of consortia in replicating or refuting published genetic associations. © The Author 2010. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oxfordjournals.org.

Cytochrome P450 (CYP) enzymes, involved in metabolism of tobacco carcinogens, are also involved in estrogen metabolism and many are regulated by estrogens. These genes may thus be of relevance to gender-specific differences in lung cancer risk, particularly in early-onset lung cancer, where a high proportion of women is observed. We conducted a case-control study to investigate genetic polymorphisms in cytochromes that might modify the risk of developing early-onset lung cancer. In total, 638 Caucasian patients under the age of 51 with primary lung cancer and 1300 cancer-free control individuals, matched by age and sex, were included in this analysis. Thirteen polymorphisms in the CYP1A1, CYP1B1, CYP2A13, CYP3A4 and CYP3A5 genes were analyzed. No significant association was found for any of the analyzed polymorphisms and lung cancer risk overall. However, among women, a significantly increased risk of early-onset lung cancer was observed for carriers of the minor allele of CYP1B1 SNP rs1056836 [odds ratio (OR) 1.97; 95% confidence interval (CI) 1.32-2.94; P < 0.001]. Also, a non-significant increase in lung cancer risk was observed in the group of women carriers of the minor allele of CYP2A13 SNP rs1709084 (OR 1.64; 95% CI 1.00-2.70; P = 0.05). The effect of these two polymorphisms was shown to be modified by smoking. Haplotype analysis was performed for CYP1B1 and CYP2A13. No differences between cases and controls were observed for both genes (P = 0.63 and P = 0.42 for CYP1B1 and CYP2A13, respectively). Our results suggest that the CYP1B1 and the CYP2A13 genotypes may contribute to individual susceptibility to early-onset lung cancer in women.

Comparison of multiple DNA adduct types in tumor adjacent human lung tissue: effect of cigarette smoking.Godschalk R, Nair J, van Schooten FJ, Risch A, Drings P, Kayser K, Dienemann H, Bartsch H.German Cancer Research Center (DKFZ), Division of Toxicology and Cancer Risk Factors, Im Neuenheimer Feld 280, 69120 Heidelberg, Germany.Cigarette smokers inhale a broad range of carcinogens derived from tobacco and its pyrolysis products, including free radicals, which induce oxidative stress and subsequent lipid peroxidation (LPO). Miscoding carcinogen-DNA adducts are formed by cigarette smoke constituents and are thought to initiate lung carcinogenesis. The presence of various types of DNA damage was therefore analyzed in tumor adjacent uninvolved lung tissues of 13 smoking and 11 non-smoking operated lung cancer patients. O(4)-ethylthymidine (O(4)etT), 1,N(6)-ethenodeoxyadenosine ( epsilon dA) and 3,N(4)-ethenodeoxycytidine ( epsilon dC) were determined by immuno-enriched (32)P-postlabeling. Polycyclic aromatic hydrocarbon (PAH)-DNA adducts were measured as diagonal radioactive zones after nuclease P1 enriched (32)P-postlabeling. Mean O(4)etT and PAH-DNA adduct levels were higher in lung DNA of smokers than of non-smokers (O(4)etT/10(8) thymidine: 3.8 versus 1.6, P < 0.01; PAH-DNA adducts/10(8) nucleotides: 11.2 versus 2.2, P < 0.01). Pulmonary etheno-DNA adduct levels did not differ between smokers and non-smokers, but large inter-individual variations were observed (80- and 250-fold differences for epsilon dA and epsilon dC, respectively). As all smokers (except one) refrained from smoking at least for 1 week before surgery, our results demonstrate the persistence of O(4)etT and PAH-DNA adducts in human lung. A positive correlation obtained between O(4)etT and PAH-DNA adducts (R = 0.65, P < 0.01) suggests that both adducts are formed from cigarette smoke as the main exposure source. We conclude that in addition to the DNA adducts derived from PAH and tobacco-specific nitrosamines, miscoding O(4)etT lesions are formed by cigarette smoke that contribute to the increased genomic instability and increased lung cancer risk in smokers

Several polymorphisms in DNA repair genes have been reported to be associated with lung cancer risk including XPA (-4G/A), XPD (Lys751Gln and Asp312Asn), XRCC1 (Arg399Gln), APE1 (Asp148Glu) and XRCC3 (Thr241Met). As there is little information on the combined effects of these variants, polymorphisms were analyzed in a case-control study including 463 lung cancer cases [among them 204 adenocarcinoma and 212 squamous cell carcinoma (SCC)] and 460 tumor-free hospital controls. Odds ratios (OR) adjusted for age, gender, smoking and occupational exposure were calculated for the variants alone and combinations thereof. For homozygous individuals carrying the Glu variant of APE1, a protective effect was found (OR = 0.77, CI = 0.51-1.16). Individuals homozygous for the variants XPA (-4A) (OR = 1.53, CI = 0.94-2.5), XPD 751Gln (OR = 1.39, CI = 0.90-2.14) or XRCC3 241Met (OR = 1.29, CI = 0.85-1.98) showed a slightly higher risk for lung cancer overall. In the subgroup of adenocarcinoma cases, adjusted ORs were increased for individuals homozygous for XPA (-4A) (OR = 1.62, CI = 0.91-2.88) and XRCC3 241Met (OR = 1.65; CI = 0.99-2.75). When analyzing the combined effects of variant alleles, 54 patients and controls were identified that were homozygous for two or three of the potential risk alleles [i.e. the variants in nucleotide excision repair, XPA (-4A) and XPD 751Gln, and in homologous recombination, XRCC3-241Met]. ORs were significantly increased when all patients (OR = 2.37; CI = 1.26-4.48), patients with SCC (OR = 2.83; CI = 1.17-6.85) and with adenocarcinoma (OR = 3.05; CI = 1.49-6.23) were analyzed. Combinations of polymorphisms in genes involved in the same repair pathway (XPA + XPD or XRCC1 + APE1) affected lung cancer risk only in patients with SCC. These results indicate that lung cancer risk is only moderately increased by single DNA repair gene variants investigated but it is considerably enhanced by specific combinations of variant alleles. Analyses of additional DNA repair gene interactions in larger population-based studies are warranted for identification of high-risk subjects.