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International Journal of Molecular Epidemiology and Genetics logoLink to International Journal of Molecular Epidemiology and Genetics
. 2013 Mar 18;4(1):11–34.

DNA repair genotype and lung cancer risk in the beta-carotene and retinol efficacy trial

Jennifer A Doherty 1,2, Lori C Sakoda 2,3, Melissa M Loomis 2, Matt J Barnett 2, Liberto Julianto 2, Mark D Thornquist 2, Marian L Neuhouser 2, Noel S Weiss 2,4, Gary E Goodman 2, Chu Chen 2,4,5
PMCID: PMC3612452  PMID: 23565320

Abstract

Many carcinogens in tobacco smoke cause DNA damage, and some of that damage can be mitigated by the actions of DNA repair enzymes. In a case-control study nested within the Beta-Carotene and Retinol Efficacy Trial, a randomized chemoprevention trial in current and former heavy smokers, we examined whether lung cancer risk was associated with variation in 26 base excision repair, mismatch repair, and homologous recombination repair genes. Analyses were limited to Caucasians (744 cases, 1477 controls), and logistic regression was used to calculate odds ratios (ORs) and 95% confidence intervals (CIs) for individual SNPs and common haplotypes, with adjustment for matching factors. Lung cancer associations were observed (p<0.05) with SNPs in MSH5 (rs3131379, rs707938), MSH2 (rs2303428), UNG (rs246079), and PCNA (rs25406). MSH5 rs3131379 is a documented lung cancer susceptibility locus in complete linkage disequilibrium with rs3117582 in BAT3, and we observed associations similar in magnitude to those in prior studies (per A allele OR 1.37, 95% CI 1.13-1.65). UNG was associated with lung cancer risk at the gene level (p=0.02), and the A allele of rs246079 was associated with an increased risk (per A allele OR 1.15, 95% CI1.01-1.31). We observed stronger associations with UNG rs246079 among individuals who carried the risk genotypes (AG/AA) for MSH5 rs3131379 (pinteraction= 0.038). Our results provide additional evidence to suggest that the MSH5/BAT3 locus is associated with increased lung cancer risk among smokers, and that associations with other SNPs may vary depending upon MSH5/BAT3 genotype. Future studies to examine this possibility are warranted.

Keywords: Lung cancer, base excision repair, mismatch repair, homologous recombination repair, DNA repair, genetic polymorphism

Introduction

Lung cancer is the leading cause of cancer death worldwide, with over a million deaths annually [1]. The large majority (80-90%) of lung cancers develop in individuals who are either current or former cigarette smokers [2]. Tobacco smoke exposure can result in various types of damage to DNA, either directly by forming DNA adducts, or through the production of reactive oxygen or nitrogen species. These lesions are repaired by a wide variety of DNA repair mechanisms, including (but not limited to) base excision repair (BER), nucleotide excision repair (NER), mismatch repair (MMR), and double-strand break repair (DSB) which includes homologous recombination (HR) and non-homologous end-joining [3]. Therefore, it is plausible that genetic variation in these important pathways might influence lung cancer risk. Indeed, two of the five validated lung cancer susceptibility loci to date map to regions that include genes related to DNA repair. The 6p21.33 locus in the HLA region contains the genes BAT3 and MSH5, and MSH5 is a member of the mutS homolog gene family, involved in MMR. The association with the 12p13 locus is specific to squamous cell lung cancer, and this locus contains the RAD52 homolog gene which is involved in DSB and HR [4]. A recent meta-analysis of 16 GWAS studies with 14,900 cases and 29,485 controls of European descent confirmed these associations as well as those with 5p15 (TERT/CLPTM1L), and 15q25.1 (CHRNA5/CHRNA3/CHRNB4), and reported an additional association for squamous cell carcinoma at 9p21 (CDKN2A/p16INK4A/p14ARF/CDKN2B/p15INK4B/ANRIL) [5]. An additional locus at 6p21.31, containing HLADQA1, was reported in a Japanese GWAS study [6].

Many candidate gene and candidate pathway studies as well as meta-analyses have investigated whether genetic variants in DNA repair pathways are associated with lung cancer risk, with mixed results for genes in MMR [7-15], BER [8,15-32], and HR [8,15,16,19-22,27,29,32]; NER will not be discussed since we have previously reported our findings from analyses of NER genes and lung cancer risk [33]. Herein we report results from our systematic evaluation of associations between 176 tag and functional SNP variants in genes involved in MMR (MLH1, MSH2, MSH4, MSH5, and MSH6), BER (APEX1, LIG3, MBD4, MPG, MUTYH, NEIL1, NEIL2, NTHL1, OGG1, PCNA, PNKP, POLB, POLI, PPP1R13L, RAD18, SMUG1, TDG, UNG, and XRCC1), and HR (XRCC2 and XRCC3) and risk of lung cancer in a nested case-control study of heavy smokers.

Materials and methods

Study population

Details of this study have been published previously [33]. In brief, this nested case-control study is comprised of participants from the multicenter β-Carotene and Retinol Efficacy Trial (CARET), which was a randomized, double-blinded, placebo-controlled chemoprevention trial to assess safety and efficacy of daily supplementation with β-carotene and retinyl palmitate among individuals at high risk of developing lung cancer [34-36]. The trial included men and women ages 50-69 years who were current or former heavy smokers (i.e., quit within six years prior to enrollment) with a cigarette smoking history of ≥20 pack-years (n=14,254). The trial also included men ages 45-69 years with a documented history of occupational asbestos exposure who were current or former heavy smokers (i.e., quit within fifteen years prior to enrollment) (n=4,060). Participants were asked to complete a questionnaire at baseline and annually thereafter, to obtain extensive information about smoking history as well as other risk factors. At baseline and every two years following, they were also asked to complete a food frequency questionnaire (FFQ) describing dietary intake in the prior year. After a mean of four years of follow up, the intervention was stopped in 1996 due to higher lung cancer incidence and overall mortality rates in the intervention versus placebo arm. CARET continued follow up for lung cancer and other outcomes until 2005. Tumor histology data were obtained from pathology reports collected as part of the CARET endpoint review process and through the California, Oregon, and Washington state cancer registries, since about 85% of all participants resided in these states at the time of CARET enrollment.

Participants were eligible for the present nested case-control study if they had provided a whole blood specimen for genetic research between February 1994 and January 1997. Cases included the 793 individuals who were diagnosed with primary lung cancer, and two lung cancer-free controls were matched to each case on age (±4 years), sex, race/ethnicity, enrollment year (two year intervals), baseline smoking status (current or former), history of occupational asbestos exposure, and length of follow-up. Controls were additionally required to have completed at least one FFQ. DNA was extracted from whole blood, and eighteen controls were excluded due to low DNA yield (≤10 μg), leaving a total of 793 cases and 1,568 controls available for genotyping. Three cases were excluded after genotyping, because their diagnoses were later learned to be benign or carcinoid lung tumors.

The Institutional Review Board of the Fred Hutchinson Cancer Research Center and the five other participating institutions approved all study protocols, and all participants provided written informed consent.

SNP selection and genotyping

Tag SNPs were selected from HapMap Phase I and II Centre d’Etude du Polymorphism Humain (CEU; NCBI build 36, dbSNP build 129) for the region spanning ±2,500 base pairs of each candidate gene using the ldSelect algorithm [37] to classify SNPs with a minor allele frequency (MAF) of >=5% into bins with a pair-wise linkage disequilibrium (LD) threshold of r2>=0.8. Additional putative functional SNPs were also selected (for more details, please see Sakoda et al. [33]). We assayed a total of 185 SNPs using three methods: 137 were genotyped in a custom 384-plex Illumina GoldenGate assay that included SNPs in DNA repair, cell cycle control and drug metabolism; 45 were genotyped using individual Applied Biosystem TaqMan assays; and three were genotyped using Sequenom at the Genome Analysis Core Facility at the University of California, San Francisco. Eleven SNPs failed assays, were monomorphic, or genotype frequencies among the non-Hispanic white controls deviated from those expected under Hardy-Weinberg equilibrium as assessed using Fisher’s exact test (p<0.001). After excluding these SNPs, the large majority of SNPs had genotype call success of greater than 99%; 8 SNPs had call success between 95.1 and 98.9%. Genotype concordance for all SNPs was 100% in a set of 82 randomly-placed blind duplicates. Data were excluded for 3 case and 6 control samples that failed the Illumina assays or were identified by Illumina to be gender-mismatched, leaving 787 cases and 1,562 controls available for analysis. A subset of the CARET samples (397 cases and 393 controls) were previously analyzed using the Illumina HumanHap300 BeadChip in an initial GWA study of lung cancer by Hung et al. [38], and these data (394 cases and 391 controls) are also included in the latest metaanalysis [5].

Genotype analysis

Due to small numbers of Hispanic and non-White individuals (43 cases, 85 controls), all analyses were restricted to non-Hispanic whites (744 cases, 1,477 controls). Odds ratios (OR) and 95% confidence intervals (95% CI) were calculated using logistic regression (Stata® 11, StataCorp, College Station, TX) and were adjusted for the case-control matching variables (age, sex, enrollment year, baseline smoking status, and occupational asbestos exposure), using the most common homozygous genotype as the reference group. Per allele ORs and 95% CIs were calculated by coding SNP genotypes according to the number of minor alleles carried (0, 1, or 2).

We examined whether SNP associations varied by age (<70, ≥70 years), sex (male, female), smoking status at baseline (former, current), the number of pack-years smoked at baseline or time of blood draw (defined as the product of the average number of cigarette packs smoked per day and the total number of years smoked, divided into thirds of the distribution among controls), occupational asbestos exposure (yes, no), trial arm assignment (intervention, placebo), and tumor histology (non-small cell lung cancer, small cell lung cancer). Since MSH5 rs3131379/BAT3 rs3117582 and CHRNA5/CHRNA3/CHRNB4 rs16969968 are validated lung cancer susceptibility loci, we also examined associations stratified by these SNPs. Wald p-values of the cross product of SNP genotype and the categorical exposure of interest were generated to formally test for departure from multiplicative relationships. As these are exploratory analyses, the reported p-values are not adjusted for multiple comparisons.

Haplotype analysis

Pairwise linkage disequilibrium (LD) patterns were visualized for each gene region using Haploview, version 4.2 [39]. Haplotype imputation from tagSNP genotype data was conducted using the haplo.stats package (http://mayoresearch.mayo.edu/schaid_lab/software.cfm) in R, version 2.10.1. The expectation-maximization algorithm was used to calculate haplotype frequencies and global tests for each gene were used to evaluate whether there were case-control differences in haplotype frequencies. Additive model ORs and 95% CIs were calculated for each imputed haplotype with a frequency of >1% using the most common haplotype as the reference group, and adjusting for the matching variables.

In order to address issues of multiple testing, we performed gene-set analyses which take into account the number of SNPs tested and the LD between SNPs in each gene (PLINK version 1.04) [40]. Test statistics were averaged for SNPs in each gene and max(T) permutation was performed 10,000 times to calculate empirical p-values taking into account the matching factors.

Results

Baseline characteristics of this nested case-control study have been reported previously [33]. Two thirds of the participants were male, and 73% of participants were current smokers. The distribution of matching factors was broadly similar between cases and controls, though cases were slightly older than controls and were more likely to have reported a heavier smoking history. We successfully evaluated a total of 175 SNPs, with SNP coverage (the proportion of common SNPs represented by the genotyped SNPs through LD in the HapMap Phase I and II CEU populations) for all genes at >=95%, except for MLH1 (89%), MBD4 (93%) and XRCC2 (94%).

We observed associations with lung cancer for SNPs in the MMR genes MSH5 and MSH2, and in the BER genes PCNA and UNG. We observed a marginal association with a SNP in MPG. Specifically, the minor alleles of the MSH5 SNPs rs3131379 and rs707938 were associated with an increased risk of lung cancer, and there was no association with the only non-synonymous SNP in that gene (rs6905572). Perallele ORs (95% CI) for rs3131379 (A allele) and rs707938 (G allele) were, respectively 1.37 (1.13-1.65) and 1.15 (1.01-1.31) (Table 1). For rs3131379, the ORs and 95% CIs for one or two copies of the A allele (compared to none) were 1.31 (1.06-1.62) and 2.30 (1.12-4.72). The rs3131379 A allele was carried in a single haplotype that also contained the minor allele for rs707938 (although the minor allele for rs707938 was carried in several additional haplotypes), at a frequency of 11% in controls and 14% in cases. Compared to the haplotype containing no variant alleles, this haplotype was associated with an increased risk (OR 1.43, 95% CI 1.15-1.77; global p-value 0.02) (Table 3). Risk of lung cancer associated with this SNP/haplotype did not appear to vary by gender, current/former cigarette smoking, pack-years of smoking, asbestos exposure, or randomization arm, nor did it differ between small cell and non-small cell histologies (data are not shown, but are available upon request). MSH2 rs2303428 was associated with an increased risk of lung cancer (per-G-allele OR 1.24, 95% CI 1.01-1.52), and this association did not vary by any subgroup. The only haplotype that included the rs2303428 G allele was not associated with risk, nor were any other haplotypes in this gene (Table 3).

Table 1.

Per-allele ORs for BER, HR, and MMR SNPs and lung cancer risk among non-Hispanic white smokers

Major allele Minor allele   Genotype distributiona All


MAFc Cases Controls (744 cases, 1,477 controls)

Pathway Gene SNP (A) (a) (%) AA Aa aa AA Aa aa OR (95% CI) p-value
MMRb MLH1 rs1800734 G A 23.0% 470 212 46 858 520 66 0.91 (0.78, 1.06) 0.215
MMR MLH1 rs1540354 T A 17.0% 499 226 18 1026 399 50 1.05 (0.89, 1.24) 0.553
MMR MLH1 rs4579 G A 45.0% 224 361 159 454 719 304 1.03 (0.91, 1.17) 0.652
MMR MSH2 rs10188090 G A 37.0% 275 366 102 576 706 194 1.06 (0.93, 1.21) 0.394
MMR MSH2 rs2059520 A G 34.0% 299 355 84 626 675 166 1.05 (0.92, 1.20) 0.442
MMR MSH2 rs2303428 A G 9.0% 589 142 13 1204 266 6 1.24 (1.01, 1.52) 0.043
MMR MSH2 rs12998837 T A 13.0% 532 165 12 1068 313 32 1.00 (0.83, 1.21) 0.991
MMR MSH2 rs6544991 A C 18.0% 506 220 17 1008 413 52 0.97 (0.82, 1.14) 0.699
MMR MSH2 rs13425206 C A 4.0% 690 53 1 1356 118 2 0.90 (0.65, 1.24) 0.509
MMR MSH2 rs17036577 A G 9.0% 623 117 4 1227 241 8 0.96 (0.76, 1.20) 0.723
MMR MSH2 rs1863332 A C 8.0% 614 120 9 1239 226 12 1.09 (0.88, 1.36) 0.423
MMR MSH2 rs1981929 A G 41.0% 272 348 124 513 712 251 0.95 (0.84, 1.08) 0.459
MMR MSH2 rs4638843 G C 12.0% 581 151 11 1135 313 27 0.92 (0.76, 1.12) 0.41
MMR MSH2 rs4952887 G A 8.0% 627 108 9 1255 209 11 1.08 (0.86, 1.35) 0.506
MMR MSH2 rs6741393 G A 3.0% 697 45 2 1380 92 2 1.00 (0.71, 1.42) 0.992
MMR MSH2 rs6753135 G A 12.0% 579 152 12 1139 317 19 0.98 (0.81, 1.19) 0.828
MMR MSH2 rs10191478 G T 43.0% 229 376 139 477 730 270 1.04 (0.92, 1.18) 0.54
MMR MSH2 rs4987188 G A 2.0% 713 31 0 1428 47 1 1.29 (0.82, 2.04) 0.27
MMR MSH4 rs5745325 G A 28.0% 384 306 54 773 576 128 0.98 (0.86, 1.13) 0.797
MMR MSH4 rs5745433 A C 26.0% 424 247 69 823 547 106 1.02 (0.89, 1.17) 0.752
MMR MSH4 rs3819949 A G 34.0% 339 297 91 633 614 188 0.94 (0.82, 1.07) 0.333
MMR MSH4 rs2047435 G A 13.0% 552 173 17 1110 343 22 1.06 (0.89, 1.28) 0.507
MMR MSH4 rs1146644 G A 42.0% 249 363 131 515 683 278 1.00 (0.88, 1.13) 0.995
MMR MSH4 rs1498313 A G 40.0% 275 327 141 528 717 230 1.05 (0.92, 1.19) 0.477
MMR MSH4 rs5745513 T A 8.0% 616 122 4 1248 219 8 1.10 (0.88, 1.39) 0.39
MMR MSH4 rs5745549 G A 3.0% 690 53 1 1388 85 3 1.19 (0.85, 1.67) 0.317
MMR MSH5 rs6905572 G A 13% 572 162 10 1120 333 24 0.95 (0.79, 1.15) 0.621
MMR MSH5 rs3131379 G A 11% 548 180 16 1166 292 15 1.37 (1.13, 1.65) 0.001
MMR MSH5 rs707937 C G 20% 477 236 29 948 469 56 1.01 (0.86, 1.18) 0.884
MMR MSH5 rs707938 A G 32% 322 318 104 681 635 161 1.15 (1.01, 1.31) 0.038
MMR MSH5 rs707939 C A 35% 326 343 73 620 673 176 0.91 (0.80, 1.04) 0.184
MMR MSH5 rs2299851 G A 10% 604 133 5 1202 256 17 0.99 (0.80, 1.22) 0.928
MMR MSH5 rs3117572 G A 17% 514 201 29 1014 416 47 1.00 (0.85, 1.18) 0.999
MMR MSH5 rs3131382 G A 6% 645 80 6 1273 164 4 1.04 (0.80, 1.35) 0.76
MMR MSH5 rs1802127 C T 2% 716 28 0 1427 49 1 1.10 (0.69, 1.76) 0.683
MMR MSH6 rs1800932 A G 18% 498 220 25 990 428 53 1.00 (0.85, 1.18) 0.984
MMR MSH6 rs1800937 G A 11% 599 136 9 1169 297 10 0.95 (0.77, 1.17) 0.615
MMR MSH6 rs1800935 A G 29% 381 289 66 736 604 125 0.97 (0.84, 1.11) 0.641
MMR MSH6 rs2710163 A G 39% 278 340 124 551 690 233 1.02 (0.90, 1.16) 0.748
MMR MSH6 rs2348244 A G 14% 545 185 13 1084 358 33 0.98 (0.82, 1.18) 0.856
MMR MSH6 rs3136245 G A 19% 488 226 27 960 465 48 1.00 (0.85, 1.17) 0.972
MMR MSH6 rs330792 A C 11% 565 170 9 1156 307 14 1.13 (0.93, 1.37) 0.23
MMR MSH6 rs1800936 C T 13% 574 155 15 1110 350 17 0.94 (0.77, 1.13) 0.501
MMR MSH6 rs3136329 A G 42% 242 359 140 481 731 259 1.03 (0.90, 1.16) 0.701
BERb APEX1 rs1760945 C T 8% 637 100 4 1249 213 10 0.92 (0.73, 1.17) 0.509
BER APEX1 rs1760944 C A 39% 270 352 119 547 694 231 1.03 (0.91, 1.18) 0.607
BER APEX1 rs3136817 T C 25% 411 276 57 840 541 96 1.08 (0.93, 1.24) 0.313
BER APEX1 rs1130409 A C 47% 192 361 190 413 723 338 1.10 (0.98, 1.25) 0.116
BER LIG3 rs3135962 A C 7% 647 95 2 1264 207 6 0.91 (0.71, 1.16) 0.443
BER LIG3 rs3135989 A C 6% 644 97 2 1301 174 1 1.17 (0.90, 1.51) 0.249
BER LIG3 rs2074516 G C 10% 598 135 8 1184 276 17 0.96 (0.78, 1.18) 0.696
BER LIG3 rs4796030 C A 42% 242 377 123 486 730 261 0.99 (0.87, 1.13) 0.904
BER LIG3 rs1052536 G A 47% 189 396 156 415 742 320 1.04 (0.91, 1.18) 0.584
BER MBD4 rs3138360 G A 6% 666 77 1 1292 174 3 0.85 (0.64, 1.12) 0.253
BER MBD4 rs140696 G A 9% 604 137 3 1210 257 10 1.04 (0.84, 1.29) 0.727
BER MBD4 rs9821282 G A 16% 537 185 20 1035 408 34 0.94 (0.79, 1.11) 0.453
BER MPG rs1013358 T C 14% 577 153 14 1093 354 30 0.86 (0.71, 1.04) 0.110
BER MPG rs2562182 A G 16% 559 164 18 1044 400 32 0.84 (0.70, 1.00) 0.050
BER MPG rs743725 C T 19% 518 203 23 978 450 49 0.88 (0.75, 1.04) 0.140
BER MUTYH rs3219489 G C 25% 417 279 42 825 562 79 1.00 (0.86, 1.15) 0.948
BER MUTYH rs3219487 G A 8% 628 112 3 1240 225 9 0.96 (0.76, 1.21) 0.728
BER MUTYH rs3219484 G A 7% 638 106 0 1273 198 6 1.01 (0.79, 1.30) 0.930
BER MUTYH rs3219474 A G 8% 631 109 4 1255 212 6 1.04 (0.82, 1.32) 0.747
BER NEIL1 rs7182283 G T 50% 185 359 192 349 777 339 1.04 (0.91, 1.18) 0.578
BER NEIL1 rs4462560 C G 26% 428 274 41 813 565 99 0.91 (0.78, 1.05) 0.194
BER NEIL2 rs4841593 C G 8% 621 120 2 1256 209 11 1.08 (0.86, 1.36) 0.510
BER NEIL2 rs904009 A C 24% 434 252 57 851 535 88 1.02 (0.88, 1.18) 0.804
BER NEIL2 rs2010628 G T 23% 445 248 51 881 521 75 1.03 (0.89, 1.20) 0.664
BER NEIL2 rs8191529 G C 9% 634 105 5 1229 240 8 0.87 (0.69, 1.10) 0.238
BER NEIL2 rs804267 A G 33% 333 319 92 669 651 155 1.05 (0.92, 1.20) 0.456
BER NEIL2 rs8191534 T A 23% 441 250 53 865 528 82 1.01 (0.88, 1.17) 0.858
BER NEIL2 rs8191542 G C 22% 437 260 38 889 503 70 1.06 (0.91, 1.24) 0.422
BER NEIL2 rs8191589 T A 22% 443 263 37 889 516 72 1.04 (0.89, 1.20) 0.645
BER NEIL2 rs4840581 G A 45% 232 359 153 442 724 309 0.96 (0.85, 1.09) 0.563
BER NEIL2 rs4840583 C T 45% 219 367 158 425 771 281 1.03 (0.90, 1.17) 0.687
BER NEIL2 rs804256 T C 36% 304 338 102 597 695 185 1.01 (0.88, 1.15) 0.914
BER NEIL2 rs8191604 A C 26% 409 276 57 807 569 99 1.00 (0.87, 1.15) 0.987
BER NEIL2 rs4840585 A C 8% 627 115 2 1258 208 10 1.05 (0.83, 1.32) 0.700
BER NEIL2 rs1874546 C G 24% 456 254 31 859 526 83 0.87 (0.75, 1.01) 0.074
BER NEIL2 rs8191649 C T 22% 466 233 45 889 519 69 0.96 (0.83, 1.12) 0.620
BER NEIL2 rs6982453 A G 49% 200 389 154 374 755 345 0.92 (0.81, 1.04) 0.189
BER NEIL2 rs1534862 G A 23% 454 243 46 864 534 78 0.95 (0.82, 1.10) 0.464
BER NEIL2 rs6997097 A G 7% 654 84 4 1281 186 7 0.92 (0.71, 1.19) 0.514
BER NEIL2 rs1043180 G A 12% 575 160 8 1127 333 17 0.94 (0.77, 1.14) 0.533
BER NEIL2 rs2645450 T C 23% 426 273 45 878 531 68 1.10 (0.95, 1.28) 0.187
BER NEIL2 rs904015 G A 35% 321 327 95 614 678 174 0.99 (0.87, 1.13) 0.877
BER NTHL1 rs12447809 G T 19% 474 233 37 960 463 54 1.07 (0.92, 1.26) 0.361
BER NTHL1 rs1132368 G A 4% 689 54 1 1348 128 0 0.86 (0.62, 1.20) 0.379
BER NTHL1 rs2531213 A G 3% 697 47 0 1378 99 0 0.93 (0.65, 1.33) 0.672
BER NTHL1 rs3211995 G A 17% 517 205 22 1009 427 41 0.95 (0.81, 1.13) 0.579
BER NTHL1 rs2516740 A C 23% 452 255 37 880 524 73 0.96 (0.83, 1.12) 0.593
BER NTHL1 rs2516739 G A 22% 459 248 37 886 517 72 0.95 (0.82, 1.10) 0.495
BER OGG1 rs159153 A G 29% 353 307 84 748 584 140 1.11 (0.97, 1.27) 0.127
BER OGG1 rs1052133 C G 23% 440 265 39 873 519 85 1.00 (0.86, 1.16) 0.992
BER OGG1 rs293795 A G 18% 498 222 24 990 438 49 0.98 (0.83, 1.15) 0.815
BER OGG1 rs293794 A G 18% 499 221 24 986 439 49 0.97 (0.83, 1.14) 0.736
BER OGG1 rs293796 G A 8% 623 110 8 1260 207 8 1.14 (0.91, 1.43) 0.253
BER PCNA rs3729558 G C 47% 223 373 148 422 719 335 0.92 (0.81, 1.05) 0.205
BER PCNA rs17349 G A 12% 594 140 8 1147 309 19 0.88 (0.72, 1.07) 0.199
BER PCNA rs25406 G A 40% 239 370 135 553 675 249 1.14 (1.01, 1.29) 0.038
BER PCNA rs25405 A G 12% 591 141 8 1145 306 19 0.89 (0.73, 1.09) 0.262
BER PCNA rs4239761 A G 19% 476 233 34 970 439 68 1.04 (0.90, 1.22) 0.587
BER PNKP rs7257463 T A 34% 319 327 98 628 685 164 1.04 (0.92, 1.19) 0.518
BER PNKP rs1290646 G A 50% 188 383 172 373 734 366 0.96 (0.85, 1.09) 0.558
BER PNKP rs3739177 C T 8% 615 124 5 1259 211 7 1.20 (0.96, 1.51) 0.112
BER PNKP rs2257103 G A 39% 265 362 115 546 699 224 1.04 (0.92, 1.19) 0.519
BER PNKP rs2353005 G A 16% 543 187 14 1057 379 41 0.92 (0.77, 1.10) 0.356
BER POLB rs3136711 T C 8% 627 111 6 1247 219 11 1.03 (0.82, 1.29) 0.829
BER POLB rs2976244 A T 7% 645 95 2 1288 177 11 0.98 (0.76, 1.25) 0.851
BER POLB rs3136790 A C 11% 585 154 5 1170 286 18 1.00 (0.82, 1.22) 0.991
BER POLB rs3136797 C G 2% 716 28 0 1430 46 1 1.15 (0.72, 1.84) 0.569
BER POLB rs2073664 G A 6% 647 89 2 1288 168 11 0.96 (0.75, 1.24) 0.761
BER POLI rs3730668 C A 41% 283 336 116 524 681 254 0.91 (0.80, 1.03) 0.135
BER POLI rs476630 G A 29% 367 300 77 750 600 126 1.08 (0.95, 1.24) 0.248
BER POLI rs686881 A G 6% 643 100 1 1310 161 6 1.20 (0.92, 1.54) 0.173
BER POLI rs3730814 C A 23% 431 272 40 886 499 89 1.04 (0.90, 1.20) 0.593
BER POLI rs3218786 A G 3% 701 40 2 1391 82 0 1.06 (0.73, 1.53) 0.771
BER POLI rs8305 A G 30% 359 315 70 716 630 131 1.03 (0.90, 1.18) 0.673
BER POLI rs596986 G C 6% 643 100 1 1310 161 6 1.20 (0.92, 1.54) 0.173
BER PPP1R13L rs6966 T A 16% 539 185 20 1048 377 47 0.95 (0.80, 1.12) 0.524
BER PPP1R13L rs4803817 A G 23% 451 255 36 874 510 88 0.94 (0.81, 1.09) 0.425
BER PPP1R13L rs10412761 A G 40% 282 357 105 541 681 252 0.92 (0.81, 1.05) 0.204
BER PPP1R13L rs1005165 G A 17% 527 194 22 1016 410 45 0.93 (0.78, 1.10) 0.367
BER RAD18 rs4389469 C T 40% 282 349 113 547 691 239 0.97 (0.85, 1.10) 0.619
BER RAD18 rs369032 A G 38% 285 357 102 579 674 224 0.99 (0.87, 1.13) 0.915
BER RAD18 rs2035221 G A 9% 613 123 6 1227 235 10 1.05 (0.85, 1.31) 0.641
BER RAD18 rs593205 G C 8% 605 136 3 1251 211 12 1.23 (0.99, 1.53) 0.066
BER RAD18 rs373572 A G 26% 402 283 56 800 571 105 1.02 (0.88, 1.17) 0.805
BER RAD18 rs13088787 C A 13% 569 165 10 1127 326 24 0.98 (0.81, 1.19) 0.868
BER RAD18 rs615967 T C 21% 461 253 30 920 480 77 0.99 (0.85, 1.15) 0.850
BER RAD18 rs604092 A G 18% 501 220 22 1004 414 56 1.00 (0.85, 1.18) 0.962
BER SMUG1 rs971 G A 34% 324 323 93 654 647 172 1.03 (0.90, 1.17) 0.654
BER SMUG1 rs3087404 G A 46% 226 358 157 437 714 325 0.96 (0.85, 1.09) 0.573
BER TDG rs172814 A G 16% 548 186 10 1052 384 40 0.87 (0.72, 1.03) 0.113
BER TDG rs4135054 G A 11% 573 163 8 1170 291 16 1.11 (0.91, 1.35) 0.290
BER TDG rs4135061 A G 27% 404 297 41 788 578 109 0.93 (0.80, 1.07) 0.305
BER TDG rs4135064 G A 9% 599 140 4 1221 246 9 1.13 (0.91, 1.40) 0.274
BER TDG rs4135081 A G 37% 273 370 101 579 695 200 1.06 (0.93, 1.21) 0.388
BER TDG rs3751206 G A 7% 644 96 2 1292 174 9 1.04 (0.81, 1.34) 0.735
BER TDG rs4135087 G A 10% 610 130 3 1184 278 13 0.87 (0.70, 1.08) 0.197
BER TDG rs167715 A G 11% 576 160 8 1164 294 19 1.05 (0.87, 1.28) 0.598
BER TDG rs10861152 G A 39% 291 350 97 538 715 216 0.91 (0.80, 1.03) 0.142
BER TDG rs1866074 A G 51% 178 387 178 377 689 409 0.96 (0.85, 1.09) 0.517
BER TDG rs4135106 A G 7% 654 86 2 1282 183 9 0.88 (0.68, 1.14) 0.326
BER TDG rs4135128 G C 9% 617 123 3 1241 218 17 1.02 (0.82, 1.27) 0.849
BER UNG rs3890995 A G 18% 491 233 20 986 461 30 1.06 (0.89, 1.25) 0.529
BER UNG rs1018783 T A 16% 492 232 20 1033 403 41 1.13 (0.96, 1.33) 0.152
BER UNG rs2569987 A G 17% 501 223 19 1009 421 45 1.01 (0.86, 1.19) 0.893
BER UNG rs246079 A G 42% 217 381 145 485 750 241 1.15 (1.01, 1.31) 0.034
BER UNG rs34259 C G 20% 446 266 30 938 476 62 1.10 (0.94, 1.28) 0.245
BER XRCC1 rs25487 C T 37% 288 365 91 604 664 209 1.00 (0.88, 1.14) 0.950
BER XRCC1 rs25486 A G 37% 288 365 90 599 664 209 1.00 (0.87, 1.13) 0.946
BER XRCC1 rs25489 C T 4% 685 57 2 1348 128 1 0.94 (0.69, 1.29) 0.701
BER XRCC1 rs1799782 G A 5% 661 82 1 1320 153 4 1.05 (0.80, 1.38) 0.733
BER XRCC1 rs3213344 G C 5% 661 80 1 1320 150 5 1.03 (0.78, 1.35) 0.844
BER XRCC1 rs3213334 G A 24% 434 266 44 866 509 102 0.99 (0.85, 1.14) 0.851
BER XRCC1 rs2023614 G C 8% 633 107 1 1249 220 6 0.92 (0.72, 1.18) 0.513
BER XRCC1 rs2854510 A G 21% 470 245 28 936 461 78 0.96 (0.82, 1.12) 0.586
BER XRCC1 rs2854509 C A 22% 456 242 42 914 480 80 1.02 (0.88, 1.18) 0.793
BER XRCC1 rs3213266 G A 8% 630 111 2 1238 232 7 0.92 (0.73, 1.16) 0.477
BER XRCC1 rs3213255 A G 43.0% 242 375 126 491 712 274 0.98 (0.86, 1.11) 0.759
HRb XRCC2 rs3218536 G A 7% 631 109 2 1262 210 5 1.05 (0.82, 1.33) 0.715
HR XRCC2 rs6964582 G C 4% 663 77 2 1349 124 2 1.26 (0.95, 1.68) 0.114
HR XRCC2 rs3218438 T C 9% 598 138 8 1215 247 15 1.10 (0.89, 1.35) 0.378
HR XRCC2 rs3218408 A C 22% 430 278 35 901 494 78 1.08 (0.93, 1.25) 0.316
HR XRCC2 rs3218373 C A 9% 617 119 7 1230 235 10 1.03 (0.82, 1.28) 0.808
HR XRCC2 rs2040639 G A 48% 212 366 166 387 767 322 0.97 (0.85, 1.10) 0.625
HR XRCC3 rs861539 G A 39% 307 333 104 536 724 217 0.89 (0.78, 1.01) 0.067
HR XRCC3 rs3212102 C T 3% 711 33 0 1402 75 0 0.88 (0.58, 1.33) 0.539
HR XRCC3 rs3212090 G A 32% 311 354 78 694 628 151 1.12 (0.98, 1.28) 0.087
HR XRCC3 rs3212079 G A 7% 644 99 1 1271 191 12 0.93 (0.73, 1.19) 0.585
HR XRCC3 rs861530 C T 29% 362 328 54 733 625 119 1.01 (0.88, 1.17) 0.839
HR XRCC3 rs1799794 A G 18% 477 245 22 980 442 48 1.08 (0.92, 1.27) 0.340
HR XRCC3 rs861528 G A 26% 427 267 45 807 550 107 0.90 (0.78, 1.04) 0.157
a

Among all cases and controls; AA, homozygous major allele; Aa, heterozygous; aa, homozygous minor allele; numbers do not sum to total due to missing.

b

MMR, mismatch repair; BER, base excision repair; HR, homologous recombination.

c

MAF, minor allele frequency.

Table 3.

MSH2, MSH5, PCNA, and UNG haplotypes and lung cancer risk

graphic file with name ijmeg0004-0011-t1.jpg

For the BER genes, the A allele of PCNA rs25406 was associated with an increased risk of lung cancer (per-allele OR 1.14, 95% CI 1.01-1.29; Table 1), with an association present only among individuals ages 70 years and older (per allele OR 1.38 (1.14-1.66)); among women (1.37 (1.10-1.70)); and among participants who had not been exposed to asbestos (1.22 (1.06-1.40)) (data are not shown, but are available upon request). The G allele of UNG rs246079 was associated with lung cancer risk (per-allele OR 1.15, 95% CI 1.01-1.31; Table 1), and associations did not vary by subgroup. The p-value for gene-level significance for UNG was 0.02, and the haplotype that contained the major allele for all of the SNPs was more frequent in controls than cases (41.1% versus 37.9%, respectively). Four out of five of the other haplotypes included the minor allele of rs246079 and all had ORs that were greater than 1. Only the combined rare genotypes were strongly associated with an increased risk (OR 2.35, 95% CI 1.27-4.36; Table 3). The G allele of MPG rs2562182 was marginally associated with a decreased risk of lung cancer (per-allele OR 0.84, 95% CI 0.70, 1.00; Table 1), and this association was present only among individuals receiving placebo (per allele OR 0.68 (0.51-0.90)). While the p-value for gene-level significance for XRCC2 was 0.03, no SNPs (Table 1) or haplotypes in this gene were individually associated with risk. None of the SNPs in XRCC1 were associated with lung cancer risk overall, but the magnitude of the associations between 4 SNPs (representing 2 SNPs with r2<0.80) in XRCC1 and lung cancer risk appeared to differ between men and women, with interaction p-values less than 0.004 and 0.0001 for rs3213334 (data are not shown, but are available upon request).

In exploratory analyses stratified by the known lung cancer susceptibility loci CHRNA5 rs16969968 and MSH5 rs3131379 genotypes, we observed a departure from a multiplicative relationship (p<0.05) for SNPs in MSH2, MSH4, MSH5, LIG3, and XRCC2 by rs16969968 genotype, with generally stronger associations among individuals carrying the rs16969968 GG genotype than the AG/AA (risk) genotypes. When we stratified by MSH5 rs3131379 genotype, associations with lung cancer were generally stronger among individuals carrying at least one of the rs3131379 A (risk) alleles compared to the GG genotype (Table 2), with a departure from a multiplicative relationship for at least one SNP in each of the MMR genes studied (MLH1, MSH2, MSH4, and MSH6), as well as in the BER genes MUTYH, NTHL1, RAD18, and UNG and the HR gene XRCC2. Among SNPs for which we observed an overall association with lung cancer risk, associations varied by rs3131379 genotype only for UNG rs246079. The per G allele ORs and 95% CIs among AA/AG carriers and among GG carriers were 1.48 (1.13, 1.94) and 1.07 (0.92, 1.24), respectively (pinteraction= 0.038; Table 2).

Table 2.

Per-allele ORs for BER, HR, and MMR SNPs and lung cancer risk among non-Hispanic white smokers, stratified by MSH5 rs3131379 and CHRNA5 rs16969968 genotypes

rs16969968 GG rs16969968 AG/AA rs3131379 GG rs3131379 AG/AA
(258 ca, 624 co) (483 ca, 852 co) (548 ca, 1,166 co) (196 ca, 307 co)




Pathway Gene SNP OR (95% CI) OR (95% CI) pc OR (95% CI) OR (95% CI) pc
MMRb MLH1 rs1800734 0.99 (0.77, 1.28) 0.85 (0.70, 1.03) 0.410 0.93 (0.78, 1.11) 0.84 (0.61, 1.15) 0.505
MMR MLH1 rs1540354 0.99 (0.76, 1.30) 1.11 (0.90, 1.37) 0.605 0.95 (0.78, 1.15) 1.40 (1.01, 1.95) 0.039
MMR MLH1 rs4579 1.01 (0.82, 1.25) 1.03 (0.88, 1.21) 0.905 1.07 (0.92, 1.23) 0.91 (0.70, 1.19) 0.344
MMR MSH2 rs10188090 1.13 (0.91, 1.41) 1.00 (0.85, 1.18) 0.392 1.01 (0.87, 1.17) 1.22 (0.93, 1.61) 0.190
MMR MSH2 rs2059520 1.12 (0.89, 1.40) 1.02 (0.86, 1.21) 0.561 1.00 (0.85, 1.16) 1.25 (0.95, 1.65) 0.141
MMR MSH2 rs2303428 1.42 (1.01, 2.01) 1.13 (0.87, 1.47) 0.280 1.30 (1.03, 1.64) 1.05 (0.67, 1.66) 0.457
MMR MSH2 rs12998837 1.01 (0.75, 1.36) 1.01 (0.79, 1.28) 0.992 0.88 (0.71, 1.10) 1.47 (1.01, 2.13) 0.025
MMR MSH2 rs6544991 0.99 (0.75, 1.30) 0.95 (0.77, 1.18) 0.840 0.86 (0.71, 1.04) 1.41 (1.00, 1.98) 0.012
MMR MSH2 rs13425206 1.00 (0.59, 1.69) 0.84 (0.55, 1.28) 0.642 0.89 (0.62, 1.29) 0.88 (0.43, 1.81) 0.973
MMR MSH2 rs17036577 0.77 (0.52, 1.15) 1.08 (0.81, 1.43) 0.179 0.94 (0.72, 1.22) 0.98 (0.62, 1.56) 0.796
MMR MSH2 rs1863332 1.08 (0.74, 1.57) 1.12 (0.86, 1.47) 0.865 1.09 (0.86, 1.40) 1.17 (0.73, 1.88) 0.816
MMR MSH2 rs1981929 0.90 (0.73, 1.11) 0.98 (0.84, 1.15) 0.549 0.97 (0.84, 1.12) 0.91 (0.70, 1.17) 0.606
MMR MSH2 rs4638843 0.98 (0.72, 1.33) 0.90 (0.70, 1.15) 0.595 1.07 (0.86, 1.33) 0.57 (0.38, 0.86) 0.009
MMR MSH2 rs4952887 1.53 (1.05, 2.22) 0.88 (0.66, 1.16) 0.022 1.12 (0.87, 1.44) 1.00 (0.62, 1.61) 0.663
MMR MSH2 rs6741393 1.20 (0.66, 2.16) 0.85 (0.55, 1.32) 0.342 1.12 (0.76, 1.65) 0.65 (0.30, 1.44) 0.260
MMR MSH2 rs6753135 0.90 (0.64, 1.26) 1.01 (0.79, 1.28) 0.616 0.99 (0.80, 1.24) 0.90 (0.60, 1.35) 0.768
MMR MSH2 rs10191478 1.16 (0.93, 1.44) 0.97 (0.83, 1.14) 0.197 1.01 (0.87, 1.17) 1.15 (0.89, 1.50) 0.354
MMR MSH2 rs4987188 1.55 (0.73, 3.27) 1.09 (0.61, 1.97) 0.487 1.71 (1.04, 2.83) 0.38 (0.11, 1.39) 0.034
MMR MSH4 rs5745325 1.26 (1.01, 1.57) 0.85 (0.71, 1.02) 0.009 0.90 (0.77, 1.06) 1.26 (0.96, 1.66) 0.035
MMR MSH4 rs5745433 0.97 (0.77, 1.23) 1.05 (0.88, 1.25) 0.589 0.97 (0.83, 1.14) 1.20 (0.91, 1.58) 0.250
MMR MSH4 rs3819949 0.86 (0.69, 1.07) 0.97 (0.82, 1.15) 0.407 0.97 (0.83, 1.13) 0.84 (0.64, 1.10) 0.359
MMR MSH4 rs2047435 0.97 (0.71, 1.31) 1.13 (0.90, 1.43) 0.464 1.18 (0.96, 1.45) 0.74 (0.50, 1.09) 0.053
MMR MSH4 rs1146644 0.85 (0.69, 1.05) 1.09 (0.93, 1.28) 0.072 1.11 (0.96, 1.28) 0.69 (0.53, 0.89) 0.002
MMR MSH4 rs1498313 0.95 (0.78, 1.17) 1.11 (0.94, 1.30) 0.275 1.05 (0.91, 1.22) 1.03 (0.80, 1.33) 0.842
MMR MSH4 rs5745513 1.64 (1.16, 2.31) 0.87 (0.64, 1.19) 0.008 1.06 (0.81, 1.38) 1.23 (0.78, 1.94) 0.526
MMR MSH4 rs5745549 0.83 (0.48, 1.44) 1.60 (1.02, 2.51) 0.067 1.59 (1.08, 2.34) 0.45 (0.21, 0.97) 0.005
MMR MSH5 rs6905572 1.01 (0.74, 1.38) 0.93 (0.73, 1.19) 0.785 1.01 (0.82, 1.25) 0.80 (0.48, 1.34) 0.385
MMR MSH5 rs3131379 1.12 (0.82, 1.52) 1.55 (1.22, 1.97) 0.101 NA NA
MMR MSH5 rs707937 0.93 (0.72, 1.21) 1.07 (0.88, 1.31) 0.361 1.02 (0.86, 1.22) 1.30 (0.84, 2.01) 0.361
MMR MSH5 rs707938 0.96 (0.77, 1.19) 1.28 (1.09, 1.51) 0.028 1.03 (0.87, 1.21) 1.16 (0.79, 1.71) 0.593
MMR MSH5 rs707939 1.18 (0.95, 1.47) 0.78 (0.65, 0.92) 0.003 0.96 (0.83, 1.12) 0.98 (0.67, 1.42) 0.975
MMR MSH5 rs2299851 0.90 (0.63, 1.28) 1.05 (0.80, 1.37) 0.418 1.05 (0.83, 1.32) 0.85 (0.48, 1.49) 0.485
MMR MSH5 rs3117572 0.90 (0.69, 1.19) 1.06 (0.86, 1.30) 0.435 1.11 (0.93, 1.32) 0.68 (0.40, 1.13) 0.094
MMR MSH5 rs3131382 0.82 (0.53, 1.28) 1.19 (0.86, 1.65) 0.217 1.15 (0.88, 1.52) 0.60 (0.24, 1.49) 0.186
MMR MSH5 rs1802127 0.90 (0.37, 2.19) 1.18 (0.68, 2.05) 0.596 1.02 (0.61, 1.71) 1.99 (0.58, 6.82) 0.342
MMR MSH6 rs1800932 0.93 (0.71, 1.22) 1.05 (0.86, 1.29) 0.550 1.08 (0.90, 1.31) 0.75 (0.54, 1.04) 0.068
MMR MSH6 rs1800937 0.79 (0.55, 1.15) 1.03 (0.80, 1.33) 0.298 0.81 (0.64, 1.04) 1.53 (1.01, 2.33) 0.012
MMR MSH6 rs1800935 0.88 (0.70, 1.11) 1.02 (0.86, 1.22) 0.370 0.98 (0.83, 1.14) 0.91 (0.69, 1.21) 0.751
MMR MSH6 rs2710163 1.05 (0.85, 1.29) 1.03 (0.87, 1.20) 0.914 1.09 (0.94, 1.26) 0.81 (0.62, 1.06) 0.063
MMR MSH6 rs2348244 1.07 (0.80, 1.42) 0.95 (0.75, 1.19) 0.562 1.05 (0.85, 1.28) 0.82 (0.56, 1.21) 0.271
MMR MSH6 rs3136245 1.12 (0.86, 1.44) 0.94 (0.76, 1.16) 0.371 1.03 (0.86, 1.23) 0.93 (0.66, 1.32) 0.569
MMR MSH6 rs330792 1.19 (0.87, 1.63) 1.09 (0.85, 1.40) 0.675 1.14 (0.91, 1.43) 1.08 (0.72, 1.60) 0.801
MMR MSH6 rs1800936 0.85 (0.62, 1.19) 0.99 (0.78, 1.25) 0.585 0.84 (0.67, 1.05) 1.38 (0.93, 2.04) 0.032
MMR MSH6 rs3136329 1.04 (0.84, 1.30) 1.01 (0.86, 1.18) 0.799 0.96 (0.83, 1.11) 1.24 (0.96, 1.61) 0.090
BERb APEX1 rs1760945 0.83 (0.55, 1.26) 0.96 (0.72, 1.29) 0.521 0.97 (0.74, 1.27) 0.81 (0.49, 1.33) 0.576
BER APEX1 rs1760944 0.96 (0.78, 1.18) 1.09 (0.92, 1.28) 0.307 1.05 (0.91, 1.21) 0.99 (0.76, 1.30) 0.622
BER APEX1 rs3136817 1.05 (0.84, 1.32) 1.10 (0.92, 1.32) 0.729 1.01 (0.86, 1.20) 1.21 (0.92, 1.61) 0.288
BER APEX1 rs1130409 1.21 (0.99, 1.49) 1.05 (0.90, 1.23) 0.327 1.06 (0.92, 1.22) 1.23 (0.96, 1.58) 0.376
BER LIG3 rs3135962 0.78 (0.51, 1.21) 0.97 (0.71, 1.33) 0.348 1.01 (0.76, 1.33) 0.63 (0.35, 1.14) 0.147
BER LIG3 rs3135989 1.72 (1.11, 2.66) 0.94 (0.68, 1.30) 0.029 1.18 (0.88, 1.60) 1.09 (0.63, 1.87) 0.807
BER LIG3 rs2074516 0.86 (0.61, 1.21) 1.01 (0.78, 1.31) 0.586 0.97 (0.77, 1.22) 1.01 (0.64, 1.58) 0.883
BER LIG3 rs4796030 0.88 (0.71, 1.09) 1.04 (0.88, 1.22) 0.202 0.99 (0.86, 1.15) 0.95 (0.73, 1.24) 0.785
BER LIG3 rs1052536 1.18 (0.96, 1.46) 0.98 (0.84, 1.16) 0.190 1.03 (0.89, 1.19) 1.07 (0.82, 1.38) 0.812
BER MBD4 rs3138360 0.87 (0.56, 1.35) 0.85 (0.59, 1.22) 0.907 0.84 (0.61, 1.17) 0.83 (0.48, 1.44) 0.985
BER MBD4 rs140696 1.02 (0.72, 1.45) 1.09 (0.82, 1.44) 0.702 1.02 (0.79, 1.31) 1.14 (0.73, 1.78) 0.756
BER MBD4 rs9821282 0.94 (0.71, 1.25) 0.95 (0.76, 1.19) 0.882 0.93 (0.76, 1.14) 0.95 (0.67, 1.33) 0.977
BER MPG rs1013358 1.04 (0.76, 1.42) 0.76 (0.61, 0.97) 0.146 0.84 (0.68, 1.03) 0.95 (0.63, 1.42) 0.537
BER MPG rs2562182 0.91 (0.67, 1.25) 0.80 (0.64, 0.99) 0.525 0.82 (0.67, 1.01) 0.92 (0.61, 1.39) 0.501
BER MPG rs743725 0.95 (0.71, 1.26) 0.86 (0.70, 1.05) 0.628 0.88 (0.73, 1.06) 0.92 (0.63, 1.32) 0.758
BER MUTYH rs3219489 0.90 (0.70, 1.16) 1.04 (0.86, 1.25) 0.419 0.90 (0.76, 1.07) 1.30 (0.97, 1.74) 0.028
BER MUTYH rs3219487 1.22 (0.86, 1.75) 0.85 (0.62, 1.16) 0.153 0.93 (0.71, 1.21) 1.06 (0.66, 1.69) 0.628
BER MUTYH rs3219484 0.80 (0.52, 1.23) 1.16 (0.85, 1.58) 0.159 1.10 (0.83, 1.45) 0.77 (0.44, 1.34) 0.277
BER MUTYH rs3219474 0.86 (0.58, 1.28) 1.20 (0.89, 1.62) 0.182 1.09 (0.82, 1.44) 0.91 (0.58, 1.43) 0.487
BER NEIL1 rs7182283 1.14 (0.92, 1.40) 0.98 (0.83, 1.15) 0.267 1.04 (0.90, 1.21) 1.01 (0.78, 1.30) 0.780
BER NEIL1 rs4462560 0.88 (0.70, 1.12) 0.93 (0.77, 1.13) 0.705 0.86 (0.72, 1.01) 1.11 (0.82, 1.51) 0.137
BER NEIL2 rs4841593 1.01 (0.70, 1.46) 1.16 (0.86, 1.56) 0.561 1.14 (0.88, 1.48) 0.91 (0.56, 1.51) 0.462
BER NEIL2 rs904009 1.07 (0.84, 1.37) 0.98 (0.82, 1.17) 0.569 0.97 (0.82, 1.14) 1.20 (0.90, 1.62) 0.221
BER NEIL2 rs2010628 1.09 (0.85, 1.40) 1.00 (0.83, 1.20) 0.572 1.01 (0.86, 1.20) 1.09 (0.81, 1.47) 0.718
BER NEIL2 rs8191529 0.81 (0.56, 1.18) 0.92 (0.68, 1.24) 0.666 0.91 (0.70, 1.18) 0.75 (0.44, 1.25) 0.512
BER NEIL2 rs804267 1.09 (0.87, 1.36) 1.03 (0.87, 1.21) 0.716 1.03 (0.89, 1.20) 1.11 (0.84, 1.46) 0.675
BER NEIL2 rs8191534 1.05 (0.82, 1.34) 0.99 (0.82, 1.18) 0.699 0.97 (0.82, 1.15) 1.16 (0.86, 1.55) 0.333
BER NEIL2 rs8191542 1.20 (0.94, 1.55) 0.98 (0.80, 1.18) 0.198 1.04 (0.88, 1.24) 1.13 (0.83, 1.54) 0.662
BER NEIL2 rs8191589 1.15 (0.90, 1.48) 0.96 (0.80, 1.17) 0.292 1.02 (0.85, 1.21) 1.09 (0.80, 1.48) 0.724
BER NEIL2 rs4840581 0.89 (0.73, 1.09) 1.02 (0.87, 1.20) 0.308 0.99 (0.86, 1.15) 0.87 (0.68, 1.12) 0.372
BER NEIL2 rs4840583 1.07 (0.86, 1.33) 1.00 (0.85, 1.17) 0.593 1.00 (0.86, 1.16) 1.12 (0.86, 1.46) 0.436
BER NEIL2 rs804256 0.98 (0.80, 1.21) 1.04 (0.88, 1.23) 0.781 1.03 (0.89, 1.20) 0.94 (0.72, 1.22) 0.584
BER NEIL2 rs8191604 0.98 (0.78, 1.25) 1.00 (0.84, 1.20) 0.949 0.97 (0.82, 1.14) 1.11 (0.84, 1.48) 0.395
BER NEIL2 rs4840585 0.99 (0.68, 1.45) 1.11 (0.82, 1.49) 0.640 1.12 (0.86, 1.46) 0.87 (0.52, 1.44) 0.417
BER NEIL2 rs1874546 0.77 (0.59, 0.99) 0.94 (0.78, 1.14) 0.207 0.87 (0.73, 1.04) 0.85 (0.63, 1.14) 0.869
BER NEIL2 rs8191649 1.03 (0.80, 1.33) 0.91 (0.75, 1.10) 0.447 0.93 (0.78, 1.11) 1.07 (0.79, 1.44) 0.448
BER NEIL2 rs6982453 0.90 (0.72, 1.11) 0.92 (0.79, 1.09) 0.834 0.92 (0.80, 1.07) 0.89 (0.69, 1.16) 0.787
BER NEIL2 rs1534862 1.02 (0.79, 1.30) 0.89 (0.74, 1.08) 0.432 0.92 (0.78, 1.10) 1.02 (0.76, 1.37) 0.562
BER NEIL2 rs6997097 0.85 (0.55, 1.30) 0.94 (0.68, 1.30) 0.728 0.84 (0.62, 1.13) 1.18 (0.71, 1.96) 0.237
BER NEIL2 rs1043180 0.94 (0.69, 1.29) 0.96 (0.74, 1.23) 0.984 0.94 (0.75, 1.17) 1.03 (0.67, 1.58) 0.688
BER NEIL2 rs2645450 1.05 (0.82, 1.33) 1.16 (0.96, 1.40) 0.550 1.09 (0.92, 1.29) 1.14 (0.84, 1.55) 0.757
BER NEIL2 rs904015 1.10 (0.88, 1.36) 0.92 (0.78, 1.09) 0.225 0.96 (0.82, 1.12) 1.08 (0.83, 1.40) 0.466
BER NTHL1 rs12447809 0.95 (0.72, 1.24) 1.13 (0.93, 1.37) 0.336 1.00 (0.83, 1.20) 1.30 (0.95, 1.79) 0.145
BER NTHL1 rs1132368 1.04 (0.62, 1.75) 0.73 (0.48, 1.12) 0.329 0.65 (0.43, 0.96) 1.90 (1.01, 3.58) 0.007
BER NTHL1 rs2531213 0.83 (0.47, 1.46) 1.09 (0.68, 1.77) 0.466 1.02 (0.68, 1.54) 0.66 (0.32, 1.39) 0.316
BER NTHL1 rs3211995 0.89 (0.67, 1.20) 0.97 (0.79, 1.20) 0.753 0.91 (0.75, 1.11) 1.03 (0.73, 1.44) 0.501
BER NTHL1 rs2516740 1.01 (0.78, 1.30) 0.92 (0.76, 1.11) 0.465 0.88 (0.74, 1.05) 1.18 (0.87, 1.60) 0.097
BER NTHL1 rs2516739 0.97 (0.75, 1.25) 0.92 (0.76, 1.11) 0.650 0.88 (0.73, 1.05) 1.17 (0.86, 1.58) 0.107
BER OGG1 rs159153 1.01 (0.80, 1.26) 1.18 (1.00, 1.40) 0.256 1.07 (0.92, 1.25) 1.24 (0.95, 1.62) 0.332
BER OGG1 rs1052133 1.02 (0.80, 1.29) 1.01 (0.83, 1.22) 0.997 1.01 (0.85, 1.19) 0.97 (0.71, 1.32) 0.804
BER OGG1 rs293795 0.79 (0.60, 1.05) 1.11 (0.90, 1.35) 0.066 0.95 (0.79, 1.15) 1.08 (0.76, 1.54) 0.424
BER OGG1 rs293794 0.81 (0.61, 1.07) 1.08 (0.88, 1.32) 0.114 0.95 (0.79, 1.14) 1.06 (0.75, 1.50) 0.484
BER OGG1 rs293796 0.96 (0.65, 1.41) 1.26 (0.95, 1.67) 0.228 1.15 (0.88, 1.49) 1.13 (0.71, 1.81) 0.918
BER PCNA rs3729558 0.93 (0.76, 1.14) 0.91 (0.78, 1.07) 0.977 0.94 (0.81, 1.08) 0.87 (0.67, 1.13) 0.607
BER PCNA rs17349 1.07 (0.78, 1.47) 0.78 (0.60, 1.02) 0.165 0.81 (0.64, 1.02) 1.11 (0.74, 1.69) 0.204
BER PCNA rs25406 1.07 (0.87, 1.32) 1.19 (1.02, 1.40) 0.522 1.16 (1.01, 1.34) 1.08 (0.82, 1.40) 0.636
BER PCNA rs25405 1.07 (0.77, 1.47) 0.81 (0.62, 1.05) 0.212 0.83 (0.66, 1.05) 1.11 (0.73, 1.68) 0.263
BER PCNA rs4239761 1.10 (0.86, 1.41) 1.03 (0.85, 1.26) 0.751 1.02 (0.85, 1.22) 1.10 (0.81, 1.51) 0.670
BER PNKP rs7257463 1.02 (0.82, 1.27) 1.05 (0.89, 1.24) 0.821 1.08 (0.93, 1.26) 0.96 (0.73, 1.26) 0.472
BER PNKP rs1290646 0.97 (0.78, 1.21) 0.96 (0.82, 1.12) 0.859 0.92 (0.80, 1.07) 1.09 (0.84, 1.41) 0.297
BER PNKP rs3739177 1.40 (0.97, 2.02) 1.09 (0.81, 1.45) 0.309 1.24 (0.96, 1.59) 1.11 (0.66, 1.87) 0.775
BER PNKP rs2257103 1.00 (0.81, 1.24) 1.07 (0.91, 1.26) 0.553 1.06 (0.92, 1.23) 0.99 (0.76, 1.30) 0.688
BER PNKP rs2353005 0.76 (0.57, 1.02) 1.04 (0.83, 1.30) 0.106 0.98 (0.81, 1.20) 0.76 (0.53, 1.10) 0.221
BER POLB rs3136711 0.99 (0.67, 1.45) 1.05 (0.79, 1.39) 0.853 1.02 (0.79, 1.33) 1.02 (0.64, 1.63) 0.952
BER POLB rs2976244 1.14 (0.76, 1.71) 0.88 (0.64, 1.21) 0.324 0.95 (0.71, 1.26) 1.05 (0.64, 1.73) 0.706
BER POLB rs3136790 1.11 (0.79, 1.54) 0.94 (0.73, 1.22) 0.468 0.96 (0.76, 1.22) 1.12 (0.74, 1.67) 0.562
BER POLB rs3136797 1.79 (0.93, 3.44) 0.73 (0.35, 1.49) 0.076 0.88 (0.48, 1.63) 1.67 (0.76, 3.67) 0.211
BER POLB rs2073664 1.14 (0.75, 1.72) 0.88 (0.64, 1.22) 0.330 0.94 (0.70, 1.27) 1.00 (0.60, 1.66) 0.834
BER POLI rs3730668 0.89 (0.72, 1.10) 0.89 (0.76, 1.05) 0.892 0.94 (0.81, 1.08) 0.83 (0.64, 1.08) 0.423
BER POLI rs476630 1.02 (0.82, 1.27) 1.15 (0.97, 1.37) 0.362 1.14 (0.98, 1.34) 0.94 (0.70, 1.25) 0.210
BER POLI rs686881 1.14 (0.74, 1.77) 1.20 (0.87, 1.65) 0.888 1.17 (0.87, 1.56) 1.37 (0.78, 2.42) 0.581
BER POLI rs3730814 0.99 (0.78, 1.25) 1.11 (0.92, 1.34) 0.389 1.12 (0.95, 1.32) 0.83 (0.61, 1.15) 0.093
BER POLI rs3218786 1.62 (0.85, 3.08) 0.84 (0.53, 1.33) 0.087 1.07 (0.71, 1.63) 1.16 (0.48, 2.81) 0.924
BER POLI rs8305 1.12 (0.89, 1.41) 1.00 (0.84, 1.18) 0.471 0.94 (0.81, 1.11) 1.26 (0.96, 1.66) 0.059
BER POLI rs596986 1.14 (0.74, 1.77) 1.20 (0.87, 1.65) 0.888 1.17 (0.87, 1.56) 1.37 (0.78, 2.42) 0.581
BER PPP1R13L rs6966 0.99 (0.74, 1.33) 0.91 (0.74, 1.13) 0.735 0.95 (0.78, 1.16) 0.94 (0.67, 1.33) 0.933
BER PPP1R13L rs4803817 0.96 (0.75, 1.22) 0.94 (0.78, 1.14) 0.996 0.99 (0.83, 1.17) 0.80 (0.58, 1.09) 0.252
BER PPP1R13L rs10412761 0.92 (0.75, 1.14) 0.91 (0.78, 1.07) 0.936 0.94 (0.81, 1.09) 0.87 (0.67, 1.12) 0.657
BER PPP1R13L rs1005165 0.91 (0.69, 1.20) 0.91 (0.73, 1.12) 0.840 0.90 (0.74, 1.10) 1.01 (0.71, 1.44) 0.563
BER RAD18 rs4389469 0.93 (0.75, 1.15) 0.99 (0.84, 1.16) 0.623 1.00 (0.87, 1.16) 0.87 (0.67, 1.13) 0.307
BER RAD18 rs369032 0.93 (0.75, 1.15) 1.04 (0.88, 1.22) 0.414 1.00 (0.87, 1.16) 0.96 (0.73, 1.25) 0.724
BER RAD18 rs2035221 1.02 (0.70, 1.49) 1.05 (0.80, 1.38) 0.922 1.23 (0.95, 1.58) 0.67 (0.42, 1.08) 0.029
BER RAD18 rs593205 1.37 (0.96, 1.97) 1.15 (0.87, 1.53) 0.453 1.28 (1.00, 1.66) 1.06 (0.67, 1.66) 0.439
BER RAD18 rs373572 1.01 (0.80, 1.28) 1.01 (0.84, 1.21) 0.970 1.04 (0.88, 1.22) 0.95 (0.71, 1.26) 0.533
BER RAD18 rs13088787 0.94 (0.69, 1.29) 1.01 (0.80, 1.29) 0.666 1.09 (0.88, 1.35) 0.72 (0.48, 1.09) 0.072
BER RAD18 rs615967 0.95 (0.74, 1.21) 1.02 (0.84, 1.25) 0.584 0.94 (0.78, 1.12) 1.13 (0.83, 1.53) 0.356
BER RAD18 rs604092 0.99 (0.76, 1.29) 1.01 (0.82, 1.24) 0.927 0.95 (0.79, 1.15) 1.14 (0.83, 1.57) 0.383
BER SMUG1 rs971 0.92 (0.73, 1.14) 1.10 (0.94, 1.30) 0.181 0.95 (0.82, 1.11) 1.28 (0.98, 1.67) 0.064
BER SMUG1 rs3087404 0.92 (0.75, 1.13) 0.99 (0.85, 1.16) 0.601 0.92 (0.80, 1.06) 1.10 (0.85, 1.43) 0.200
BER TDG rs172814 1.05 (0.79, 1.41) 0.77 (0.61, 0.97) 0.107 0.88 (0.72, 1.08) 0.81 (0.56, 1.18) 0.711
BER TDG rs4135054 1.03 (0.74, 1.44) 1.17 (0.92, 1.50) 0.578 1.13 (0.90, 1.42) 1.05 (0.70, 1.57) 0.817
BER TDG rs4135061 0.98 (0.77, 1.25) 0.90 (0.75, 1.07) 0.518 0.90 (0.76, 1.06) 1.04 (0.77, 1.41) 0.409
BER TDG rs4135064 0.95 (0.66, 1.37) 1.25 (0.95, 1.64) 0.264 1.14 (0.89, 1.47) 1.08 (0.70, 1.66) 0.848
BER TDG rs4135081 1.10 (0.89, 1.37) 1.03 (0.87, 1.21) 0.620 1.04 (0.89, 1.21) 1.12 (0.85, 1.47) 0.651
BER TDG rs3751206 1.06 (0.68, 1.66) 1.03 (0.76, 1.39) 0.891 1.10 (0.83, 1.46) 0.91 (0.52, 1.57) 0.483
BER TDG rs4135087 0.83 (0.59, 1.19) 0.92 (0.70, 1.22) 0.598 0.85 (0.66, 1.10) 0.86 (0.57, 1.29) 0.968
BER TDG rs167715 0.91 (0.64, 1.27) 1.13 (0.89, 1.44) 0.348 0.97 (0.77, 1.21) 1.43 (0.95, 2.16) 0.096
BER TDG rs10861152 0.95 (0.77, 1.18) 0.89 (0.75, 1.05) 0.637 0.88 (0.75, 1.02) 0.99 (0.76, 1.30) 0.408
BER TDG rs1866074 1.09 (0.89, 1.33) 0.88 (0.75, 1.03) 0.115 0.96 (0.84, 1.11) 0.95 (0.73, 1.24) 0.940
BER TDG rs4135106 0.88 (0.57, 1.37) 0.87 (0.63, 1.19) 0.912 0.87 (0.65, 1.17) 0.94 (0.54, 1.61) 0.789
BER TDG rs4135128 0.96 (0.65, 1.42) 1.03 (0.79, 1.36) 0.796 1.09 (0.85, 1.39) 0.86 (0.52, 1.42) 0.360
BER UNG rs3890995 0.95 (0.72, 1.27) 1.12 (0.91, 1.39) 0.375 1.03 (0.85, 1.25) 1.16 (0.82, 1.65) 0.601
BER UNG rs1018783 1.05 (0.80, 1.39) 1.16 (0.95, 1.43) 0.576 1.03 (0.85, 1.25) 1.45 (1.04, 2.03) 0.085
BER UNG rs2569987 1.01 (0.77, 1.34) 1.00 (0.81, 1.23) 0.848 1.08 (0.89, 1.30) 0.82 (0.58, 1.16) 0.175
BER UNG rs246079 1.06 (0.85, 1.31) 1.21 (1.03, 1.43) 0.326 1.07 (0.92, 1.24) 1.48 (1.13, 1.94) 0.038
BER UNG rs34259 1.13 (0.87, 1.45) 1.07 (0.88, 1.29) 0.723 1.02 (0.86, 1.22) 1.34 (0.98, 1.83) 0.128
BER XRCC1 rs25487 0.91 (0.73, 1.13) 1.05 (0.90, 1.24) 0.309 0.98 (0.84, 1.14) 1.09 (0.83, 1.42) 0.566
BER XRCC1 rs25486 0.90 (0.73, 1.13) 1.04 (0.88, 1.23) 0.343 0.97 (0.84, 1.13) 1.08 (0.83, 1.41) 0.548
BER XRCC1 rs25489 1.06 (0.64, 1.74) 0.87 (0.58, 1.31) 0.604 0.87 (0.61, 1.24) 1.28 (0.64, 2.58) 0.323
BER XRCC1 rs1799782 1.07 (0.68, 1.68) 1.05 (0.74, 1.49) 0.997 1.05 (0.77, 1.42) 1.17 (0.60, 2.27) 0.784
BER XRCC1 rs3213344 1.09 (0.69, 1.71) 1.00 (0.70, 1.42) 0.799 1.02 (0.75, 1.39) 1.17 (0.60, 2.27) 0.732
BER XRCC1 rs3213334 1.09 (0.86, 1.38) 0.95 (0.79, 1.14) 0.400 0.98 (0.83, 1.16) 0.99 (0.74, 1.32) 0.990
BER XRCC1 rs2023614 0.87 (0.59, 1.30) 0.96 (0.70, 1.31) 0.705 0.86 (0.65, 1.14) 1.18 (0.71, 1.97) 0.269
BER XRCC1 rs2854510 1.01 (0.78, 1.31) 0.93 (0.76, 1.12) 0.574 1.01 (0.84, 1.20) 0.82 (0.60, 1.12) 0.299
BER XRCC1 rs2854509 1.17 (0.92, 1.50) 0.96 (0.79, 1.15) 0.203 1.02 (0.86, 1.21) 1.01 (0.75, 1.35) 0.952
BER XRCC1 rs3213266 0.88 (0.60, 1.30) 0.94 (0.70, 1.27) 0.792 0.85 (0.65, 1.12) 1.20 (0.73, 1.96) 0.226
BER XRCC1 rs3213255 1.12 (0.91, 1.39) 0.91 (0.78, 1.07) 0.124 1.01 (0.87, 1.17) 0.88 (0.68, 1.14) 0.387
HRb XRCC2 rs3218536 0.90 (0.60, 1.36) 1.18 (0.87, 1.60) 0.227 1.08 (0.82, 1.42) 0.95 (0.57, 1.58) 0.644
HR XRCC2 rs6964582 1.43 (0.90, 2.30) 1.18 (0.81, 1.70) 0.502 1.18 (0.84, 1.66) 1.57 (0.89, 2.78) 0.400
HR XRCC2 rs3218438 1.43 (1.03, 1.98) 0.94 (0.72, 1.23) 0.047 0.97 (0.76, 1.24) 1.62 (1.04, 2.52) 0.032
HR XRCC2 rs3218408 1.00 (0.78, 1.30) 1.11 (0.93, 1.34) 0.495 1.18 (0.99, 1.40) 0.83 (0.61, 1.13) 0.049
HR XRCC2 rs3218373 1.08 (0.76, 1.54) 1.02 (0.77, 1.35) 0.785 1.08 (0.84, 1.39) 0.89 (0.57, 1.42) 0.466
HR XRCC2 rs2040639 0.93 (0.75, 1.15) 0.97 (0.82, 1.13) 0.854 0.93 (0.80, 1.08) 1.09 (0.84, 1.41) 0.340
HR XRCC3 rs861539 0.90 (0.72, 1.11) 0.88 (0.75, 1.04) 0.936 0.89 (0.77, 1.04) 0.87 (0.67, 1.14) 0.852
HR XRCC3 rs3212102 0.93 (0.47, 1.86) 0.85 (0.50, 1.46) 0.872 0.73 (0.44, 1.23) 1.20 (0.56, 2.54) 0.278
HR XRCC3 rs3212090 1.08 (0.86, 1.34) 1.17 (0.98, 1.39) 0.646 1.20 (1.03, 1.40) 0.95 (0.72, 1.26) 0.133
HR XRCC3 rs3212079 1.18 (0.81, 1.74) 0.80 (0.58, 1.10) 0.107 0.91 (0.68, 1.22) 0.94 (0.59, 1.49) 0.881
HR XRCC3 rs861530 1.05 (0.83, 1.33) 0.98 (0.82, 1.18) 0.717 0.93 (0.79, 1.10) 1.25 (0.93, 1.67) 0.070
HR XRCC3 rs1799794 0.99 (0.75, 1.29) 1.13 (0.92, 1.39) 0.372 1.02 (0.84, 1.22) 1.27 (0.91, 1.77) 0.226
HR XRCC3 rs861528 0.88 (0.69, 1.12) 0.90 (0.75, 1.08) 0.900 0.91 (0.77, 1.07) 0.88 (0.66, 1.17) 0.878

aAmong all cases and controls; AA, homozygous major allele; Aa, heterozygous; aa, homozygous minor allele; numbers do not sum to total due to missing.

b

MMR, mismatch repair; BER, base excision repair; HR, homologous recombination.

c

p-value for interaction.

Discussion

As expected, we observed an association between the MSH5 rs3131379/BAT3 rs3117582 known susceptibility locus and lung cancer risk. These genes lie in the highly complex human leukocyte antigen (HLA) region on 6p21.33. The HLA locus on 6p21.31 has also been reported to be associated with lung cancer risk among Japanese individuals [6]. Interestingly, one of the major findings from The Cancer Genome Atlas comprehensive genomic analysis of squamous cell cancers is the description of somatic loss-of-function mutations in the HLA-A class I major histocompatibility gene, which is also located in the 6p21.3 region [41]. Our other observations include an increased risk of lung cancer associated with a SNP in UNG, particularly among individuals who were already at increased risk because they carried at least one of the MSH5 rs3131379 A alleles; and an increased risk of lung cancer associated with certain SNPs in MSH2 and PCNA. Like SMUG1, TDG, and MBD4, UNG is a BER uracil-DNA glycosylase which repairs the mis-incorporation of the RNA constituent uracil. UNG binds to PCNA at replication foci, and is the major enzyme that removes uracil from U:A pairs. It may also be involved in short patch BER of uracil and pre-replication repair of U:G pairs [42]. MSH2 is typically involved in post-replicative MMR, forming heterodimers with MSH6 to repair base mismatches and small insertion deletion loops, and with MSH3 to repair larger insertion deletion loops [43]. MSH2 also binds to PCNA [42,44]. Lynch Syndrome, which is associated with a dramatically increased risk of colon, endometrial and ovarian cancers as well as several other cancer types, is characterized by mutations in MLH1, MSH2, and MSH6. Mutations in MSH2 confer particularly high risks, though this does not appear to be true for lung cancer [45]. PCNA performs a central role not only in DNA repair, but also in DNA replication and recombination. It forms a trimer that encircles DNA at replication forks, where it recruits other proteins [46].

While UNG and MSH2 perform distinct functions with respect to DNA repair, they have a similar and overlapping role in adaptive immunity [42]. The main function of the adaptive immune system, to recognize and remember specific pathogens, is performed through the differentiation of immunoglobulin (Ig) genes. In humans, this is achieved through two processes, somatic hypermutation (SHM) which yields antibody diversification, and class switch recombination (CSR), which produces the five Ig isotypes IgM, IgD, IgE, IgE, and IgA [42]. Both somatic hypermutation and class switch recombination are initiated by activation-induced cytidine deaminase (AID) which allows the introduction of uracil, forming key intermediate U:G pairings in Ig DNA. Recognition of the U:G pairs in specific regions of Ig by both UNG and MSH2 coupled with MSH6 allows for accumulation of mutations and diversification. Both UNG and MSH2 bind to PCNA, and additional DNA repair genes including APE1, POLN, POLB, and others are involved in the later steps, particularly for class switch recombination [47]. Mouse models deficient in either UNG or MSH2 result in mice able to produce antibodies at a level 2 to 3-fold lower than in wild type mice [48], and models deficient in UNG result in mice that develop B-cell lymphomas late in life [42]. However, deficiency in both UNG and MSH2 results in mice incapable of antibody gene diversification [48]. In humans, mutations in UNG alone result in the autosomal recessive hyper-IgM syndrome, a class switch recombination disorder characterized by IgG, IgA, and IgE deficiencies [49].

In the lung, innate and adaptive immunity launch inflammatory responses to a variety of insults such as particulate matter in cigarette smoke and other pollutants, microbial infections, and cell damage/injury. Chronic inflammation, and the interaction between innate and adaptive immune response, play central roles in cancer development [50]. Chronic pulmonary inflammation has been hypothesized to be an underlying mechanism for the increased risk of lung cancer associated with tobacco smoking, chronic obstructive pulmonary disease [51], silicosis, asbestosis [52], and lung infections (i.e., tuberculosis, pneumonia [53]), and the increased incidence of lung cancer among individuals with human immunodeficiency virus [54].

Very few prior studies have interrogated variants in UNG, MSH2, and PCNA and lung cancer risk, and only in the context of candidate gene studies of DNA repair. Two comprehensive studies described in more detail below [8,15] that examined DNA repair pathway genotype data from samples assayed using the Illumina HumanHap300 BeadChip, did not observe differences in the genotype distribution between cases and controls for SNPs in MSH2, UNG or PCNA, but they did not directly measure the SNPs associated with risk in our study. A relatively small study of French Caucasian smokers (151 lung cancer cases and 172 hospital controls) [11] did not observe associations with MSH2 rs2303428 (G allele frequency 0.10 in cases, 0.12 in controls) or PCNA rs25406 (A allele frequency 0.40 in cases, 0.47 in controls (p=0.09)); data from this study is also included in the meta-analysis by Kazma et al. [15] described below. Two other studies examined associations with MSH2 rs2303428. A Korean study with 432 lung cancer patients matched to 432 healthy controls on age and gender observed that carriage of at least one C allele was associated with an increased risk of adenocarcinoma, compared to the TT genotype (adjusted OR, 1.52; 95% CI, 1.02-2.27; P = 0.04) [13], and while the confidence limit does not exclude 1, an elevated OR (1.29 (0.83—1.99)) was observed in a Taiwanese study of 156 NSCLC patients and 235 controls matched for age, gender and smoking [14]. A candidate SNP study of Caucasian smokers that included 343 NSCLC cases and 413 population-based controls matched on age, gender and smoking did not observe an association with PCNA rs25406 (MAF 0.38 in cases, 0.38 in controls; AG, and AA, versus GG, OR 0.73 (0.52–1.0) and 1.15 (0.74–1.79) [22]. These studies do not provide rigorous support for or against associations with the SNPs of interest, since a much larger sample size is needed in order to obtain stable risk estimates of the magnitude expected.

The largest and most comprehensive interrogations of DNA repair pathways and lung cancer risk were performed by Kazma et al. [15] and Yu et al. [8] Kazma et al. [15] included 1,655 SNPs in 211 DNA repair genes in 6,911 individuals pooled from four studies. Yu et al. [8] interrogated 1806 SNPs in 125 DNA repair genes in 1154 lung cancer cases and 1137 controls matched by smoking status. With the exception of MSH5 rs3131379, the SNPs that were associated with risk in our study are not present on the HumanHap300 BeadChip, but SNPs in LD with them (in HapMap-CEU) were not associated with risk in either study (UNG, rs2430682, in LD with rs246079 (r2=0.89); MSH2, rs2042649, in LD with rs2303428 (r2=1.0)). While they examined associations with SNPs in PCNA, none of the SNPs were in LD >0.52 with the SNP (rs25406) that we observed to be associated with risk in our study.

The variants (after MSH5 rs3131379) that were most strongly associated with lung cancer risk in Kazma et al. were in the genes UBE2N, SMC1L2, and POLB, with suggestive associations for variants in RAD52 and POLN [15]. Yu et al. observed associations with SNPs in XRCC4, but they were not replicated in a meta-analysis of these SNPs in four GWAS studies totaling ~12,000 cases and ~48,000 controls [8]. Other studies of DNA repair genes have reported associations with additional candidate SNPs. A hospital-based study of smokers including 722 cases and 929 controls interrogated 29 SNPs in the BER genes MPG, OGG1, PARP1, and XRCC1, one SNP in PARP1 and two SNPs in XRCC1 (rs1799782 and rs3213255) were associated with lung cancer risk [31]. Meta-analyses of selected SNPs have observed associations with OGG1 Ser326Cys rs1052133 [20,55,56] and XRCC3 T241M rs861539 [20]. Of the genes reported to be associated with lung cancer risk in prior studies, we only examined variants in POLB, XRCC1, OGG1 and XRCC3, and they were not related to risk in our study.

An important difference between our study and the meta-analysis by Kazma et al. is the prevalence of smoking, because Kazma et al. specifically limited their analysis to studies that included both smokers and non-smokers in order to evaluate interactions between SNPs and smoking. In our study, among the controls, none were never smokers, 27.6% were former, and 72.4% were current smokers, whereas in Kazma et al., 38.8% of the controls were never smokers, 25.6% were former, and 34.5% were current smokers. The distribution was identical in the cases and controls for our study because they were matched on smoking exposure, but the distribution in cases from Kazma et al. --9.7% never, 20.5% former, and 68.9% current--differed considerably from the distribution in their controls. It is possible that there are underlying differences in the distribution of genotypes in the controls due to differences in smoking exposure. A well-documented example of this is genetic variation in the nicotinic acetylcholine receptor gene cluster on chromosome 15q25.1. For rs1051730 (which is in complete LD with rs16969968 (r2=1.0, HapMap-CEU)), the frequency of the T allele increases with increasing numbers of cigarettes smoked, with a large difference in frequency between individuals smoking 1-10 cigarettes per day (T allele frequency 0.305) and 31 or more cigarettes per day (T allele frequency 0.391) [57]. Matching controls to cases based on cigarette smoking (as we did) is arguably an advantage when attempting to identify genetic factors that might differentiate between the ~20 % of smokers who develop lung cancer from the ~80 % who do not.

In conclusion, we observed associations with SNPs in UNG, MSH2, and PCNA, all of which are involved both in DNA repair pathways and also in adaptive immunity, and the associations with the UNG variants were stronger among individuals carrying the documented MSH5/BAT3 lung cancer susceptibility allele, which was also associated with risk in our study. We were unable to confirm associations reported in prior studies with POLB, XRCC1, OGG1 and XRCC3 SNPs, and we did not evaluate variation in UBE2N, SMC1L2, RAD52, or POLN. Our study was not large enough to be able to reliably identify the presence of true weak associations, and is limited by having genotype data on only two of the five documented lung cancer susceptibility loci described to date in Caucasian populations [5]. However, our study differs from most other prior studies because it is prospective in nature and includes only heavy smokers, with cases and controls matched on smoking history. Because lung cancer is so rapidly fatal, case control study response proportions can be very low, and our study is likely to have a more representative case group, specific to smoking-associated lung cancer, than case-control studies. Furthermore, no prior studies have reported pathway-based SNP results stratified by know lung cancer susceptibility loci. The patterns of associations observed should be viewed as hypothesis-generating, requiring follow up in other studies of smoking-related lung cancer.

Acknowledgements

We thank the CARET participants, along with the CARET investigators and staff at all participating trial institutions, for their effort and contribution to this research.

Abbreviations

APEX1

apurinic/apyrimidinic-endonuclease-1

CARET

β-Carotene and Retinol Efficacy Trial

CI

confidence interval

LIG3

ligase III

MBD4

methyl binding domain 4

MLH1

MutL homolog 1, colon cancer, nonpolyposis type 2 (E. coli)

MPG

N-methylpurine-DNA glycosylase

MSH2

mutS homolog 2, colon cancer, nonpolyposis type 1 (E. coli)

MSH4

mutS homolog 4, colon cancer, nonpolyposis type 1 (E. coli)

MSH5

mutS homolog 5, colon cancer, nonpolyposis type 1 (E. coli)

MSH6

mutS homolog 6, colon cancer, nonpolyposis type 1 (E. coli)

MUTYH

mutY homolog (E. coli)

NEIL1

nei endonuclease VIII-like 1 (E. coli)

NEIL2

nei endonuclease VIII-like 2 (E. coli)

NTHL1

nth endonuclease III-like 1 (E. coli)

OGG1

8-oxo-guanine glycosylase-1

OR

odds ratio

PCNA

proliferating cell nuclear antigen

PNKP

polynucleotide kinase 3’-phosphatase

POLB

polymerase (DNA directed), beta

POLI

polymerase (DNA directed) iota

PPP1R13L

protein phosphatase 1, regulatory subunit 13 like

RAD18

RAD18 homolog (S. cerevisiae)

SD

standard deviation

SMUG1

single strand selective monofunctional uracil-DNA glycosylase

SNP

single nucleotide polymorphism

TDG

thymine/uracil mismatch DNA glycosylase

UNG

uracil-DNA glycosylase

XRCC1

X-ray repair complementing defective repair in Chinese-hamster cells 1

XRCC2

X-ray repair complementing defective repair in Chinese-hamster cells 2

XRCC3

X-ray repair complementing defective repair in Chinese-hamster cells 3

Financial support

This work is supported by R01 CA111703 and U01 CA63673 from the National Cancer Institute of the U.S. National Institutes of Health (NIH).

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