Faculty Bibliography

Two recent studies independently identified polymorphisms in the 8q24 region, including a single nucleotide polymorphism (rs1447295), strongly associated with prostate cancer risk. Here, we replicate the overall association in a large nested case-control study from the National Cancer Institute Breast and Prostate Cancer Cohort Consortium using 6,637 prostate cancer cases and 7,361 matched controls. We also examine whether this polymorphism is associated with breast cancer among 2,604 Caucasian breast cancer cases and 3,118 matched controls. The rs1447295 marker was strongly associated with prostate cancer among Caucasians (P = 1.23 x 10(-13)). When we exclude the Multiethnic Cohort samples, previously reported by Freedman et al., the association remains highly significant (P = 8.64 x 10(-13)). Compared with wild-type homozygotes, carriers with one copy of the minor allele had an OR(AC) = 1.34 (99% confidence intervals, 1.19-1.50) and carriers with two copies of the minor allele had an OR(AA) = 1.86 (99% confidence intervals, 1.30-2.67). Among African Americans, the genotype association was statistically significant in men diagnosed with prostate cancer at an early age (P = 0.011) and nonsignificant for those diagnosed at a later age (P = 0.924). This difference in risk by age at diagnosis was not present among Caucasians. We found no statistically significant difference in risk when tumors were classified by Gleason score, stage, or mortality. We found no association between rs1447295 and breast cancer risk (P = 0.590). Although the gene responsible has yet to be identified, the validation of this marker in this large sample of prostate cancer cases leaves little room for the possibility of a false-positive result

BACKGROUND: Insulin resistance has been linked with colorectal neoplasia through a number of mechanistic and observational studies. Allelic variants of genes encoding components of the insulin pathway, including insulin (INS), insulin receptor (INSR), and insulin receptor substrate-1 and insulin receptor substrate-2 (IRS1 and IRS2) have been associated with hyperinsulinemia and insulin resistance and may, therefore, predict susceptibility to colorectal neoplasia. METHODS: We investigated whether single nucleotide polymorphisms (SNP) in the INS, INSR, IRS1, and IRS2 genes are associated with risk of advanced left-sided colorectal adenoma, a cancer precursor. We analyzed 20 SNPs in a largely Caucasian study population comprising 766 cases with advanced adenomas of the distal colon and 771 controls, all of whom had undergone flexible sigmoidoscopy as part of the screening arm of the Prostate, Lung, Colorectal and Ovarian Cancer Screening Trial. RESULTS: Overall, we found limited evidence for a role of gene variants of the insulin signaling pathway and prevalence of advanced colorectal adenoma. We observed a statistically significant interaction between INSR genotypes and body mass index (BMI) with colorectal adenoma prevalence (P value for global test = 0.003) and suggestion of an interaction between INSR genotypes and glycemic load (P value for global test = 0.06); however, exploration of the interaction of BMI and glycemic load with the individual SNPs in INSR did not suggest a single SNP that may explain the significance of these global tests of interaction and did not yield any consistent patterns. CONCLUSION: These findings do not provide strong evidence for associations between polymorphic variation in genes of the insulin signaling pathway and advanced left-sided colorectal adenoma. Evidence for interaction between INSR variants and BMI and glycemic load for risk of advanced left-sided colorectal adenoma requires independent confirmation, and genotyping of INSR across a broader region and at greater density may be necessary to fully elucidate the nature of these interactions

The CYP19A1 gene encodes the enzyme aromatase, which is responsible for the final step in the biosynthesis of estrogens. In this study, we used a systematic two-step approach that included gene resequencing and a haplotype-based analysis to comprehensively survey common genetic variation across the CYP19A1 locus in relation to circulating postmenopausal steroid hormone levels and breast cancer risk. This study was conducted among 5,356 invasive breast cancer cases and 7,129 controls comprised primarily of White women of European descent drawn from five large prospective cohorts within the National Cancer Institute Breast and Prostate Cancer Cohort Consortium. A high-density single-nucleotide polymorphism (SNP) map of 103 common SNPs (> or =5% frequency) was used to identify the linkage disequilibrium and haplotype patterns across the CYP19A1 locus, and 19 haplotype-tagging SNPs were selected to provide high predictability of the common haplotype patterns. We found haplotype-tagging SNPs and common haplotypes spanning the coding and proximal 5' region of CYP19A1 to be significantly associated with a 10% to 20% increase in endogenous estrogen levels in postmenopausal women [effect per copy of the two-SNP haplotype rs749292-rs727479 (A-A) versus noncarriers; P = 4.4 x 10(-15)]. No significant associations were observed, however, with these SNPs or common haplotypes and breast cancer risk. Thus, although genetic variation in CYP19A1 produces measurable differences in estrogen levels among postmenopausal women, the magnitude of the change was insufficient to contribute detectably to breast cancer

Base excision repair (BER) corrects DNA damage caused by oxidative stress and low folate intake, which are putative risk factors for colorectal neoplasia. To examine the relationship between genetic variation in BER genes and colorectal adenoma risk, we conducted a case-control study of 767 cases of advanced colorectal adenoma and 773 controls from the baseline screening exam of the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial. Cases included participants diagnosed with advanced left-sided adenoma, and controls were subjects without evidence of a left-sided polyp by sigmoidoscopy, frequency-matched to cases on race and gender. Twenty single nucleotide polymorphisms were genotyped in four BER genes (APEX1, PARP1, POLB, and XRCC1), and conditional logistic regression was used to estimate odds ratios (OR) and 95% confidence intervals (95% CI) for the association with colorectal adenoma. Two variants with possible functional significance were associated with risk. The APEX1 51H variant was associated with a borderline significant decreased risk of colorectal adenoma (OR, 0.66; 95% CI, 0.44-1.00), and the XRCC1 399Q variant was inversely associated with risk among Caucasians (OR, 0.80; 95% CI, 0.64-0.99). Homozygotes at two PARP1 loci (A284A and IVS13+118G>A) were also associated with a decreased risk of colorectal adenoma compared with wild-type carriers (OR, 0.70; 95% CI, 0.49-0.98 for both), which was restricted to advanced adenomas displaying histologically aggressive characteristics (OR, 0.51; 95% CI, 0.33-0.78, P = 0.002 for PARP1 A284A). This study suggests that polymorphisms in APEX1, XRCC1, and PARP1 may be associated with advanced colorectal adenoma

Sex hormones have been implicated in prostate carcinogenesis and are thought to modulate cell proliferation and growth. To investigate the association between polymorphisms in hormone-related genes and prostate cancer risk, we conducted a two-stage, case-control study within the screening arm of the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial. Using DNA extracted from blood specimens, we initially genotyped 14 single nucleotide polymorphisms in genes involved in hormone regulation or metabolism (AKR1C3, CYP1A1, CYP1B1, CYP3A4, ESR1, GNRH1, HSD173B, HSD3B2, SHBG, and SRD5A2) in 488 prostate cancer cases and 617 matched controls. Heterozygotes at SHBG D356N were found to be associated with an increased risk of prostate cancer compared with the homozygous wild type, particularly among non-Hispanic whites (odds ratio, 1.54; 95% confidence interval, 1.13-2.09; P = 0.006). No significant associations were observed with the other polymorphisms. The SHBG D356N polymorphism, which has potential functional significance, was subsequently genotyped in additional 769 cases and 1,168 controls. Overall, SHBG D356N heterozygotes were found to have an increased risk of prostate cancer among whites (odds ratio, 1.34; 95% confidence interval, 1.10-1.63; P = 0.0007). This study suggests that genetic variation in SHBG may influence prostate cancer susceptibility

BACKGROUND: Selenium is a potential chemopreventive agent against prostate cancer, whose chemoprotective effects are possibly mediated through the antioxidative properties of selenoenzymes. Interrelations with other antioxidative agents and oxidative stressors, such as smoking, are poorly understood. OBJECTIVES: The aims were to investigate the association between serum selenium and prostate cancer risk and to examine interactions with other antioxidants and tobacco use. DESIGN: A nested case-control study was performed within the screening arm of the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial. Serum selenium in prospectively collected samples was compared between 724 incident prostate cancer case subjects and 879 control subjects, frequency-matched for age, time since initial screen, and year of blood draw. The men were followed for up to 8 y. RESULTS: Overall, serum selenium was not associated with prostate cancer risk (P for trend = 0.70); however, higher serum selenium was associated with lower risks in men reporting a high (more than the median: 28.0 IU/d) vitamin E intake [odds ratio (OR) for the highest compared with the lowest quartile of selenium: 0.58; 95% CI: 0.37, 0.91; P for trend = 0.05; P for interaction = 0.01] and in multivitamin users (OR for highest compared with the lowest quartile of selenium: 0.61; 95% CI: 0.36, 1.04; P for trend = 0.06; P for interaction = 0.05). Furthermore, among smokers, high serum selenium concentrations were related to reduced prostate cancer risk (OR for the highest compared with the lowest quartile of selenium: 0.65; 95% CI: 0.44, 0.97; P for trend = 0.09; P for interaction = 0.007). CONCLUSION: Greater prediagnostic serum selenium concentrations were not associated with prostate cancer risk in this large cohort, although greater concentrations were associated with reduced prostate cancer risks in men who reported a high intake of vitamin E, in multivitamin users, and in smokers

OBJECTIVES: Cigarette smoking is the leading cause of morbidity and mortality worldwide. We investigated the association between smoking behavior and genetic variations in the D2 dopamine receptor (DRD2), which mediates nicotine dependence. To assess the specificity of genetic effects, we also investigated other reward-motivated characteristics (obesity, alcohol consumption). METHODS: Four single nucleotide polymorphisms in DRD2 were genotyped in 2374 participants selected randomly from the screening arm of the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial after stratifying by sex, age, and smoking status. Smoking, obesity, and alcohol consumption were assessed by questionnaire. Single nucleotide polymorphism and haplotype associations were estimated using odds ratios (ORs) and 95% confidence intervals derived from conditional logistic regression models, adjusted for race/ethnicity. RESULTS: DRD2 polymorphisms were associated with the risk of remaining a current smoker and obesity. Current smokers were more likely than former smokers to possess the variant TaqIA allele (rsmusical sharp1800497) in a dose-dependent model (ORCT=1.2, ORTT=1.5, P for linear trend=0.007). The DRD2 haplotype T-C-T-A [TaqIA(C/T)-957(T/C)-IVS6-83(G/T)- -50977(A/G)] was more common among current than former smokers (OR=1.3, P=0.006), particularly among heavy smokers (21+ cigarettes per day; OR=1.6, P=0.006), and was more common among obese than normal weight individuals (OR=1.4, P=0.02). CONCLUSIONS: Genetic variation in DRD2 is a modifier of the reward-motivated characteristics, smoking and obesity. As fewer than 15% of smokers who attempt to quit are able to maintain abstinence for greater than 3 months, our results support that DRD2 is an appropriate molecular target for smoking cessation treatments. Our results further support evaluation of DRD2 antagonists for obesity therapies

BACKGROUND: It is possible that high-glycemic-load diets, through their hyperinsulinemic effects, can increase the risk of colorectal cancer. OBJECTIVE: We analyzed data from a cancer screening study to determine whether persons with high-glycemic-load diets would be at an increased risk of distal adenomas. DESIGN: We included subjects with no prior adenoma or cancer from the Prostate, Lung, Colorectal, and Ovarian screening trial and whose results from flexible sigmoidoscopy exams indicated either no lesions (n = 34 817) or >/=1 distal adenoma (n = 3696). We used a 137-item food-frequency questionnaire to assess usual dietary intake over the preceding 12 mo. Using logistic regression analysis, we calculated, separately for men and women, prevalence odds ratios (ORs) and 95% CIs of sigmoidoscopy-detected, distal adenomas for quintiles of energy-adjusted dietary carbohydrate, glycemic index, and glycemic load. RESULTS: ORs decreased with increasing intakes of carbohydrate for both the men and the women in unadjusted models, but these associations were attenuated in multivariate-adjusted models. Among the men, the association remained significant after adjustment (OR: 0.71; 95% CI 0.60, 0.84; P for trend < 0.0001), but in the women it did not (OR: 0.89; 95% CI: 0.73, 1.10; P for trend = 0.30). The results for glycemic index showed no associations in either men or women. Results for glycemic load closely mirrored those for carbohydrate. CONCLUSION: Despite expectations that increasing glycemic load and glycemic index would increase the risk of adenoma, we observed no association in women and even an inverse association in men

The endothelial cell-specific form of nitric oxide synthase (eNOS) may play an important role in tumor progression via angiogenesis or apoptosis. We studied eNOS -786T > C and 894G > T (Glu298Asp), two functionally significant SNPs, in relation to hazard of breast cancer recurrence or death in 873 women with incident, non-metastatic breast cancer, recruited from two teaching hospitals in Seoul, Korea, 1995-2002. Hazards were estimated by Cox proportional hazard models, in relation to genotype, adjusting for hormone receptor status, lymph node involvement, and tumor size. Women carriers of the eNOS -786C allele had significantly increased hazards of breast cancer recurrence or death, compared with women having the TT genotype (HR = 2.1, 95% CI = 1.03-4.33); risks increased up to 3-fold in ER positive cases (HR = 3.2, 95% CI = 0.95-10.50). The hazard was also increased in eNOS 894T carriers, however, it did not reach statistical significance (HR = 1.8, 95% CI = 0.85-3.93). The combined genotypes containing -786C or 894T was associated with a 2.5-fold risk, compared to the TT-GG genotypes, the most dominant genotype combination (95% CI = 1.29-4.68), with the greatest risks in ER positive cases (HR = 4.9, 95% CI = 1.31-18.36). These results indicate that the eNOS -786C polymorphism, and possibly the 894T polymorphism, are associated with breast cancer recurrence and death, particularly in women with ER positive tumors

Benzene is a recognized hematotoxicant and carcinogen that produces genotoxic damage. DNA double-strand breaks (DSB) are one of the most severe DNA lesions caused directly and indirectly by benzene metabolites. DSB may lead to chromosome aberrations, apoptosis and hematopoietic progenitor cell suppression. We hypothesized that genetic polymorphisms in genes involved in DNA DSB repair may modify benzene-induced hematotoxicity. We analyzed one or more single nucleotide polymorphisms (SNPs) in each of seven candidate genes (WRN, TP53, NBS1, BRCA1, BRCA2, XRCC3 and XRCC4) in a study of 250 workers exposed to benzene and 140 controls in China. Four SNPs in WRN (Ex4 -16 G > A, Ex6 +9 C > T, Ex20 -88 G > T and Ex26 -12 T > G), one SNP in TP53 (Ex4 +119 C > G) and one SNP in BRCA2 (Ex11 +1487 A > G) were associated with a statistically significant decrease in total white blood cell (WBC) counts among exposed workers. The SNPs in WRN and TP53 remained significant after accounting for multiple comparisons. One or more SNPs in WRN had broad effects on WBC subtypes, with significantly decreased granulocyte, total lymphocyte, CD4(+)-T cell, CD8(+)-T cell and monocyte counts. Haplotypes of WRN were associated with decreased WBC counts among benzene-exposed subjects. Likewise, subjects with TP53 Ex4 +119 C > G variant had reduced granulocyte, CD4(+)-T cell and B cell counts. The effect of BRCA2 Ex11 +1487 A > G polymorphism was limited to granulocytes. These results suggest that genetic polymorphisms in WRN, TP53 and BRCA2 that maintain genomic stability impact benzene-induced hematotoxicity