Background

There are conflicting data regarding the role of sex hormones in colorectal cancer development. Whereas clinical trials data indicate that hormone therapy use reduces the risk of colorectal cancer, data from prospective cohort studies suggest that circulating estrogen levels are positively associated with colorectal cancer risk. A surrogate measure of lifetime estrogen exposure is reproductive history. We investigated the relationship between reproductive factors and the risk of colorectal cancer.

Methods

Subjects were postmenopausal women enrolled in the National Institutes of Health–American Association of Retired Persons Diet and Health Study, a cohort of 214 162 individuals (aged 50–71 years) that included 2014 incident cases of colorectal cancer that occurred over a mean follow-up of 8.2 years. Questionnaires were used to collect data on reproductive factors, including ages at menarche, birth of first child, and menopause; parity, and use of oral contraceptives. Multivariable Cox proportional hazards models were constructed to examine associations between these reproductive factors and the risk of colorectal cancer, with adjustment for established colorectal cancer risk factors. All statistical tests were two-sided.

Results

Age at menopause (≥55 vs <40 years: hazard ratio [HR] = 1.50, 95% confidence interval [CI] = 1.23 to 1.83; Ptrend = .008) and age at birth of first child (≥30 vs ≤19 years: HR = 1.26, 95% CI = 1.01 to 1.58; Ptrend = .05) were positively associated with the risk of colorectal cancer. Among women with no history of hormone therapy use, age at menarche (≥15 vs 11–12 years: HR = 0.73, 95% CI = 0.57 to 0.94; Ptrend = .02) and parity (≥5 children vs no children: HR = 0.80, 95% CI = 0.63 to 1.02; Ptrend = .10) were inversely associated with the risk of colorectal cancer.

Conclusion

These data support a role for sex hormones in colorectal tumorigenesis and suggest that greater endogenous estrogen exposure may increase the risk of colorectal cancer in postmenopausal women.

Red meat consumption has been positively associated with colorectal cancer; however, the biologic mechanism underlying this relationship is not understood. Red meat is a major source of iron, which may play a role in colorectal carcinogenesis via increased crypt cell proliferation, cytotoxicity, and endogenous N-nitrosation. In a nested case-control study within the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial, we prospectively evaluated multiple iron exposure parameters, including dietary intake and serum measures of iron, ferritin, transferrin, total iron binding capacity (TIBC), and unsaturated iron binding capacity (UIBC) in relation to incident colorectal adenoma in 356 cases and 396 matched, polyp-free controls. We also investigated variation in eight key genes involved in iron homeostasis in relation to colorectal adenoma in an additional series totaling 1,126 cases and 1,173 matched controls. We observed a positive association between red meat intake and colorectal adenoma (odds ratio comparing extreme quartiles [ORq4-q1] = 1.59, 95% confidence interval [CI]: 1.02-2.49, P-trend = 0.03). Serum TIBC and UIBC were inversely associated with colorectal adenoma (ORq4-q1 = 0.57, 95% CI: 0.37-0.88, P-trend = 0.03; and ORq4-q1 = 0.62, 95% CI: 0.40-0.95, P-trend = 0.04, respectively). Colorectal adenoma was not associated with serum ferritin, iron, or transferrin saturation, or with polymorphisms in genes involved in iron homeostasis. Serum TIBC and UIBC, parameters which have a reciprocal relationship with overall iron load, were inversely related to colorectal adenoma, suggesting that individuals with lower iron status have a reduced risk of colorectal adenoma.

BACKGROUND

It is hypothesized that inflammation may mediate the relationship between obesity and endometrial cancer risk. We examined the associations of three inflammation markers, C-reactive protein (CRP), interleukin (IL)-6, and tumor necrosis factor (TNF)-α, with risk of endometrial cancer.

METHODS

A case-cohort study was nested within the Women’s Health Initiative, a cohort of postmenopausal women. Baseline plasma samples of 151 incident endometrial cancer cases and 301 subcohort subjects not using hormones were assayed.

RESULTS

CRP, but not IL-6 or TNF-α, was positively associated with endometrial cancer risk after adjusting for age and BMI [hazard ratio comparing extreme quartiles (HRq4-q1) = 2.29; 95% confidence interval (CI) = 1.13–4.65; ptrend = 0.012). After additional adjustment for estradiol and insulin, this association was attenuated (HRq4-q1 = 1.70;95% CI= 0.78–3.68; ptrend = 0.127). Obesity (BMI ≥ 30 kg/m2) was associated with endometrial cancer risk in an age-adjusted model. The obesity effect was reduced by 48%, 67%, and 77% when either estradiol, CRP, or insulin, respectively, was included in the model, and it became null when all three factors were adjusted for simultaneously.

CONCLUSIONS

The association between inflammation, as indicated by a relatively high level of CRP, and endometrial cancer risk may partially be explained by hyperinsulinemia and elevated estradiol. Nevertheless, all three factors contribute to and mediate the link between obesity and endometrial cancer in postmenopausal women not using hormones.

IMPACT

The association between obesity and endometrial cancer risk in postmenopausal women may be attributed to inflammation, insulin resistance, and elevated estrogen.

Background

Inflammation is hypothesized to play a role in colorectal tumorigenesis. Circulating levels of C-reactive protein (CRP), a serologic marker of the inflammatory response, have been positively associated with colorectal cancer development in some studies; however, there are limited data on the relation of CRP with colorectal adenomas, established precursors of colorectal cancer.

Methods

A nested case-control investigation of CRP levels and incident colorectal adenoma was conducted in the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial, a randomized trial of 154,942 individuals designed to test the efficacy of flexible sigmoidoscopy on colorectal cancer mortality when performed once, and then repeated 3-5 years later. Serum CRP levels were measured in baseline blood specimens from participants who were free of polyps in the left-sided colorectum at the baseline screening procedure, but who were found at the subsequent screen to have at least one colorectal adenoma(N=356), and in a set of polyp-free, frequency-matched controls(N=396).

Results

In a multivariable logistic regression model that included established colorectal adenoma risk factors, a 1-unit increase in log CRP level was associated with a 15% reduction in risk of developing colorectal adenoma (OR=0.85, 95%CI, 0.75-0.98, Ptrend=0.01). This association did not differ according to body size, smoking behavior, gender, use of non-steroidal anti-inflammatory drugs, or adenoma location.

Conclusions

High circulating CRP levels may be protective against colorectal adenoma development.

Impact

Though at contrast with mechanistic data on inflammation and colorectal tumorigenesis, this finding is not inconsistent with prior results on CRP and colorectal adenoma and warrants further investigation.

Objective

To evaluate the expression of G-coupled protein receptor 30 (GPR30) and estrogen receptor beta (ERβ) in uterine carcinosarcoma.

Study Design

Immunohistochemistry was performed using antibodies to GPR30, ERβ, estrogen receptor alpha (ERα), and progesterone receptor (PR). The staining intensity and percentage of positive cells were scored for each tissue section. Expression levels were compared using the Wilcoxon rank-sum test. Correlation was evaluated by Spearman’s rho and logistic regression.

Results

Compared with normal endometrium, carcinosarcoma had lower ERα and PR expression (both p<0.01) but higher GPR30 epithelial expression (p=0.03). Advanced stage carcinosarcoma had higher GPR30 (p<0.01) and ERβ (p=0.02) epithelial expression compared with early stage carcinosarcoma. Expression of GPR30 and ERβ correlated with each other (p<0.01), and not with ERα or PR.

Conclusions

In uterine carcinosarcoma, GPR30 and ERβ are coordinately overexpressed and expression levels increase in advanced stage disease, supporting the involvement of alternative estrogen receptors in disease progression.

Background

The insulin-like growth factor (IGF) axis has been hypothesized to influence the rate of human immunodeficiency virus (HIV) disease progression. This premise is based largely on laboratory models showing that IGF-I stimulates thymic growth and increases lymphocyte numbers and that IGF-binding protein (IGFBP)–3 has an opposing effect, inhibiting hematopoietic stem cell development.

Methods

We studied 1422 HIV-infected women enrolled in a large cohort that entailed semiannual follow-up (initiated in 1994). Baseline serum samples were tested for IGF-I and IGFBP-3 to determine their associations with incident clinical acquired immunodeficiency syndrome (AIDS) and CD4+ T cell count decline prior to April 1996 (before the era of highly active antiretroviral therapy [HAART]).

Results

Low IGF-I levels (Ptrend = .02) and high IGFBP-3 levels (Ptrend = .02) were associated with rapid CD4+ T cell count decline. Only IGFBP-3, however, was significantly associated with AIDS incidence (hazard ratio for highest vs. lowest quartile, 2.65 [95% confidence interval, 1.30–5.42]; Ptrend = .02) in multivariable models.

Conclusions

These findings suggest that serum levels of IGFBP-3 (and possibly IGF-I) are associated with the rate of HIV disease progression in women and, more broadly, that interindividual heterogeneity in the IGF axis may influence HIV pathogenesis. If correct, the IGF axis could be a target for interventions to slow HIV disease progression and extend the time before use of HAART becomes necessary.

Background

Observational studies and randomized trials have suggested that estrogens and/or progesterone may lower the risk for colorectal cancer. Inherited variation in the sex-hormone genes may be one mechanism by which sex hormones affect colorectal cancer, although data are limited.

Method

We conducted a comprehensive evaluation of single nucleotide polymorphisms (SNPs) in genes encoding 3 hormone receptors (ESR1, ESR2, PGR) and 5 hormone synthesizers (CYP19A1 and CYP17A1, HSD17B1, HSD17B2, HSD17B4) among 427 women with incident colorectal cancer and 871 matched controls who were Caucasians of European ancestry from 93676 postmenopausal women enrolled in the Women's Health Initiative Observational cohort. A total of 242 haplotype-tagging and functional SNPs in the 8 genes were included for analysis. Unconditional logistic regression with adjustment for age and hysterectomy status was used to estimate odds ratios (ORs) and 95% confidence intervals (CIs).

Results

We observed a weak association between the CYP17A1 rs17724534 SNP and colorectal cancer risk (OR per risk allele (A) = 1.39, 95% CI = 1.09-1.78, corrected p-value = 0.07). In addition, a suggestive interaction between rs17724534 and rs10883782 in 2 discrete LD blocks of CYP17A1 was observed in relation to colorectal cancer (empirical p value = 0.04). Moreover, one haplotype block of CYP19A1 was associated with colorectal cancer (corrected global p value = 0.02), which likely reflected the association with the tagging SNP, rs1902584, in the block.

Conclusion

Our findings offer some support for a suggestive association of CYP17A1 and CYP19A1 variants with colorectal cancer risk.

Obesity is a major risk factor for endometrial cancer, a relationship thought to be largely explained by the prevalence of high estrogen levels in obese women. Obesity is also associated with high levels of insulin, a known mitogen. However, no prospective studies have directly assessed whether insulin and/or insulin-like growth factor-I (IGF-I), a related hormone, are associated with endometrial cancer while accounting for estrogen levels. We therefore conducted a case-cohort study of incident endometrial cancer in the Women’s Health Initiative Observational Study, a prospective cohort of 93,676 postmenopausal women. The study involved all 250 incident cases and a random subcohort of 465 subjects for comparison. Insulin, total IGF-I, free IGF-I, IGF-binding protein-3, glucose, and estradiol levels were measured in fasting baseline serum specimens. Cox models were used to estimate associations with endometrial cancer, particularly endometrioid adenocarcinomas, the main histologic type (n = 205). Our data showed that insulin levels were positively associated with endometrioid adenocarcinoma [hazard ratio contrasting highest versus lowest quartile (HRq4-q1), 2.33; 95% confidence interval (95% CI), 1.13–4.82] among women not using hormone therapy after adjustment for age and estradiol. Free IGF-I was inversely associated with endometrioid adenocarcinoma (HRq4-q1, 0.53; 95% CI, 0.31–0.90) after adjustment for age, hormone therapy use, and estradiol. Both of these associations were stronger among overweight/obese women, especially the association between insulin and endometrioid adenocarcinoma (HRq4-q1, 4.30; 95% CI, 1.62–11.43). These data indicate that hyperinsulinemia may represent a risk factor for endometrioid adenocarcinoma that is independent of estradiol. Free IGF-I levels were inversely associated with endometrioid adenocarcinoma, consistent with prior cross-sectional data.

Objectives

Carcinogenic action of meat-related exposures, such as heterocyclic amines (HCAs), polycyclic aromatic hydrocarbons (PAHs), and N-nitroso compounds (NOCs), might explain positive associations between red and processed meat and colorectal neoplasia. Single nucleotide polymorphisms in xenobiotic metabolizing enzyme (XME) genes could alter activation/detoxfication of these compounds.

Methods

We evaluated interactions between several XME genes (CYP1A1, CYP1B1, CYP2A6, CYP2C9, CYP2E1, CYP3A4, EPHX1, GSTM1, GSTM2, GSTT1, NAT1, NAT2, NQO1, SULT1A1, and SULT1A2) and meat-related exposures using a pathway-based approach in 720 advanced colorectal adenoma cases of the distal colon or rectum and 746 controls from the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial. Using meat-related databases, we estimated intake of the HCAs, 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) and 2-amino-1-methyl-6-phenyl-imidazo[4,5-b]pyridine (PhIP), the PAH, benzo[a]pyrene (B[a]P), and nitrate/nitrite, as NOC precursors.

Results

There were possible interactions between PhIP and CYP1B1 (Pinteraction=0.019) and NQO1 (Pinteraction=0.007), B[a]P and CYP1B1 (Pinteraction=0.005) and CYP3A4 (Pinteraction=0.021), and nitrate/nitrite and CYP1A1 (Pinteraction=0.022) in relation to colorectal adenoma. However, none of these interactions were statistically significant using a false discovery rate threshold of 0.20.

Conclusions

Common variants in XME genes may modify the association of HCAs, PAHs, and nitrate/nitrite with advanced colorectal adenoma, but investigation in other populations is required, especially within consortia.

Adiposity and adipocyte-derived cytokines have been implicated in prostate carcinogenesis. However, the relationship of adipokine gene variants with prostate cancer risk has not been thoroughly investigated. We therefore examined common variants of the IL6, LEP, LEPR, TNF, and ADIPOQ genes in relation to prostate cancer in a case-control study nested within a large cohort of Finnish men. The study sample consisted of 1,053 cases of prostate cancer, diagnosed over an average 11 years of follow up, and 1,053 controls matched to the cases on age, intervention group, and date of baseline blood draw. Logistic regression was used to model the relative odds of prostate cancer. We also examined genotypes in relation to serum insulin, IGF-1, and IGF-1:IGFBP-3 among 196 controls. Variant alleles at three loci (−14858A>G, −13973A>C, −13736C>A) in a potential regulatory region of the LEP gene conferred a statistically significant 20% reduced risk of prostate cancer. For example, at the −14858A>G locus, heterozygotes and homozygotes for the A allele had an odds ratio (OR) of prostate cancer of 0.76 (95% confidence interval [95% CI]= 0.62, 0.93) and 0.79 (95% CI = 0.60, 1.04), respectively. At 13288G>A, relative to the GG genotype, the AA genotype was associated with a suggestive increased risk of prostate cancer (OR = 1.29; 95% CI, 0.99,1.67; P-trend = 0.05). Polymorphisms in the IL6, LEPR, TNF, and ADIPOQ genes were not associated with prostate cancer. Allelic variants in the LEP gene are related to prostate cancer risk, supporting a role for leptin in prostate carcinogenesis.

Objectives

To evaluate the relationship of hormone (ERα, ERβ, PR) and growth factor receptor (IGF1R, HER2) expression with disease progression in uterine carcinosarcoma.

Study Design

Immunohistochemistry was performed on tissue arrays using standard methodology. Differences between groups were evaluated by the Wilcoxon rank-sum test. Interactions between tumor stage and receptor expression were determined by linear trend analysis.

Results

Compared to normal endometrium, carcinosarcomas exhibited low ERα and PR expression (all P<0.01), but overexpressed ERβ (P=0.02). ERβ expression increased in advanced stage disease (P=0.02). IGF1R expression was lower in carcinosarcoma compared with normal endometrium (P=0.01). HER2 expression was elevated and increased with disease progression (P<0.01).

Conclusions

In uterine carcinosarcoma, ERβ expression is elevated and increases with disease progression, whereas ERα and PR are suppressed. HER2 expression is increased while IGF1R is lower than in normal endometrium. These data support a potential role for ERβ in disease progression via crosstalk with HER2.

Significant reductions in prostate cancer incidence and mortality were observed in men randomized to receive 50 mg supplemental vitamin E (α-tocopherol) per day in the Alpha-Tocopherol, Beta-Carotene Cancer Prevention (ATBC) Study. We hypothesized that variation in key vitamin E transport genes might directly affect prostate cancer risk or modify the effects of vitamin E supplementation. Associations between prostate cancer risk and 13 polymorphisms in two genes – TTPA and SEC14L2 – were examined in 982 incident prostate cancer cases and 851 controls drawn from the ATBC Study. There was no association between the genetic variants and prostate cancer risk. Significant interactions were observed, however, between two variants in SEC14L2 (IVS11+931A>G and IVS11−896A>T) and the trial α-tocopherol supplement such that vitamin E supplementation reduced prostate cancer risk among men who were homozygous for either common allele [odds ratios (OR) and 95% confidence intervals (CI) = 0.52 (0.30−0.90) and 0.64 (0.46−0.88), respectively] and nonsignificantly increased risk among those who carried one or two copies of either variant allele [ORs = 1.27 (0.90−1.79) and 1.21 (0.96−1.52), respectively] (both p for interaction < 0.05). Genotype-phenotype analyses revealed significant but modest differences in baseline circulating concentrations of α-tocopherol and serum responses to the vitamin E supplementation for several polymorphisms. This study demonstrates that genetic variation in TTPA and SEC14L2 is associated with serum α-tocopherol but does not have a direct impact on prostate cancer. Our results do, however, suggest that polymorphisms in SEC14L2 may modify the effect of vitamin supplementation regimens on prostate cancer risk.

Background

The positive association between obesity and postmenopausal breast cancer has been attributed, in part, to the fact that estrogen, a risk factor for breast cancer, is synthesized in adipose tissue. Obesity is also associated with high levels of insulin, a known mitogen. However, no prospective studies have directly assessed associations between circulating levels of insulin and/or insulin-like growth factor (IGF)-I, a related hormone, and the risk of breast cancer independent of estrogen level.

Methods

We conducted a case–cohort study of incident breast cancer among nondiabetic women who were enrolled in the Women's Health Initiative Observational Study (WHI-OS), a prospective cohort of 93 676 postmenopausal women. Fasting serum samples obtained at study entry from 835 incident breast cancer case subjects and from a subcohort of 816 randomly chosen WHI-OS subjects were tested for levels of insulin, glucose, total IGF-I, free IGF-I, insulin-like growth factor binding protein-3, and estradiol. Multivariable Cox proportional hazards models were used to estimate associations between levels of the serologic factors and baseline characteristics (including body mass index [BMI]) and the risk of breast cancer. All statistical tests were two-sided.

Results

Insulin levels were positively associated with the risk of breast cancer (hazard ratio [HR] for highest vs lowest quartile of insulin level = 1.46, 95% confidence interval [CI] = 1.00 to 2.13, Ptrend = .02); however, the association with insulin level varied by hormone therapy (HT) use (Pinteraction = .01). In a model that controlled for multiple breast cancer risk factors including estradiol, insulin level was associated with breast cancer only among nonusers of HT (HR for highest vs lowest quartile of insulin level = 2.40, 95% CI = 1.30 to 4.41, Ptrend < .001). Obesity (BMI ≥30 kg/m2) was also associated with the risk of breast cancer among nonusers of HT (HR for BMI ≥30 kg/m2 vs 18.5 to <25 kg/m2 = 2.12, 95% CI = 1.26 to 3.58, Ptrend = .003); however, this association was attenuated by adjustment for insulin (Ptrend = .40).

Conclusion

These data suggest that hyperinsulinemia is an independent risk factor for breast cancer and may have a substantial role in explaining the obesity–breast cancer relationship.

Objective

The purpose of this study was to determine the clinical utility of CA125 measurement in patients with uterine carcinosarcoma (CS).

Methods

Ninety-five consecutive patients treated for CS at a single institution were identified. All 54 patients who underwent preoperative CA125 measurement were included in the study. Data were abstracted from the medical records. Tests of association between preoperative CA125 and previously identified clinicopathologic prognostic factors were performed using Fisher’s exact test and Pearson chi-square test. To evaluate relationship of CA125 elevation and survival, a Cox proportional hazard model was used for multivariate analysis, incorporating all of prognostic factors identified by univariate analysis.

Results

Preoperative CA125 was significantly associated with the presence of extrauterine disease (P<0.001), deep myometrial invasion (P<0.001), and serous histology of the epithelial component (P=0.005). Using univariate survival analysis, stage (HR=1.808, P=0.004), postoperative CA125 level (HR=9.855, P<0.001), and estrogen receptor positivity (HR=0.314, P=0.029) were significantly associated with survival. In the multivariate model, only postoperative CA125 level remained significantly associated with poor survival (HR=5.725, P=0.009).

Conclusion

Preoperative CA125 elevation is a marker of extrauterine disease and deep myometrial invasion in patients with uterine CS. Postoperative CA125 elevation is an independent prognostic factor for poor survival. These findings indicate that CA125 may be a clinically useful serum marker in the management of patients with CS.

Background

Estrogen and androgen have been linked to the regulation of circulating hepatocyte growth factor (HGF), an adipose tissue-derived cytokine. It is possible that the CYP19A1 gene which alters sex hormones production may influence HGF levels. We examined the association between the CYP19A1 gene variants and plasma HGF concentrations.

Design

We evaluated 45 common and putative functional variants of CYP19A1 and circulating levels of HGF among 260 postmenopausal women who later developed colorectal cancer from the Women's Health Initiative Observational Cohort. As the distribution of HGF levels was highly skewed, we transformed HGF concentrations for all women into a log-, ranked-, or normal score-scale value. Multiple linear regression with adjustment for age was used to evaluate the associations.

Results

We observed an association between the rs7172156, rs1008805, rs6493494, rs749292, and rs11636639 variants and HGF levels in ranked and normal score scales (corrected p values ≤0.02), although the association of these 5 SNPs with log-scale HGF was not significant (corrected p values ≥0.16). The associations remained unchanged after additional adjustment for hormone therapy use and estradiol levels. These 5 SNPs, which were in linkage disequilibrium (pairwise D′≥97%, r2≥56%), constituted a block with 2 common haplotypes accounting for 82% frequency. The most common haplotype, TCCCA, was associated with lower ranked- or normal score-transformed HGF levels (corrected p values ≤0.001), whereas the second most common haplotype, CTTCA, was associated with higher ranked- or normal score-transformed HGF levels (corrected p values ≤0.02).

Conclusion

Our findings of a potential association between the CYP19A1 variants and circulating HGF levels warrant confirmation in studies with larger sample size.

Sex hormone-binding globulin (SHBG) is a glycoprotein responsible for the transport and biologic availability of sex steroid hormones, primarily testosterone and estradiol. SHBG has been associated with chronic diseases including type 2 diabetes (T2D) and with hormone-sensitive cancers such as breast and prostate cancer. We performed a genome-wide association study (GWAS) meta-analysis of 21,791 individuals from 10 epidemiologic studies and validated these findings in 7,046 individuals in an additional six studies. We identified twelve genomic regions (SNPs) associated with circulating SHBG concentrations. Loci near the identified SNPs included SHBG (rs12150660, 17p13.1, p = 1.8×10−106), PRMT6 (rs17496332, 1p13.3, p = 1.4×10−11), GCKR (rs780093, 2p23.3, p = 2.2×10−16), ZBTB10 (rs440837, 8q21.13, p = 3.4×10−09), JMJD1C (rs7910927, 10q21.3, p = 6.1×10−35), SLCO1B1 (rs4149056, 12p12.1, p = 1.9×10−08), NR2F2 (rs8023580, 15q26.2, p = 8.3×10−12), ZNF652 (rs2411984, 17q21.32, p = 3.5×10−14), TDGF3 (rs1573036, Xq22.3, p = 4.1×10−14), LHCGR (rs10454142, 2p16.3, p = 1.3×10−07), BAIAP2L1 (rs3779195, 7q21.3, p = 2.7×10−08), and UGT2B15 (rs293428, 4q13.2, p = 5.5×10−06). These genes encompass multiple biologic pathways, including hepatic function, lipid metabolism, carbohydrate metabolism and T2D, androgen and estrogen receptor function, epigenetic effects, and the biology of sex steroid hormone-responsive cancers including breast and prostate cancer. We found evidence of sex-differentiated genetic influences on SHBG. In a sex-specific GWAS, the loci 4q13.2-UGT2B15 was significant in men only (men p = 2.5×10−08, women p = 0.66, heterogeneity p = 0.003). Additionally, three loci showed strong sex-differentiated effects: 17p13.1-SHBG and Xq22.3-TDGF3 were stronger in men, whereas 8q21.12-ZBTB10 was stronger in women. Conditional analyses identified additional signals at the SHBG gene that together almost double the proportion of variance explained at the locus. Using an independent study of 1,129 individuals, all SNPs identified in the overall or sex-differentiated or conditional analyses explained ∼15.6% and ∼8.4% of the genetic variation of SHBG concentrations in men and women, respectively. The evidence for sex-differentiated effects and allelic heterogeneity highlight the importance of considering these features when estimating complex trait variance.

Author Summary

Sex hormone-binding globulin (SHBG) is the key protein responsible for binding and transporting the sex steroid hormones, testosterone and estradiol, in the circulatory system. SHBG regulates their bioavailability and therefore their effects in the body. SHBG has been linked to chronic diseases including type 2 diabetes and to hormone-sensitive cancers such as breast and prostate cancer. SHBG concentrations are approximately 50% heritable in family studies, suggesting SHBG concentrations are under significant genetic control; yet, little is known about the specific genes that influence SHBG. We conducted a large study of the association of SHBG concentrations with markers in the human genome in ∼22,000 white men and women to determine which loci influence SHBG concentrations. Genes near the identified genomic markers in addition to the SHBG protein coding gene included PRMT6, GCKR, ZBTB10, JMJD1C, SLCO1B1, NR2F2, ZNF652, TDGF3, LHCGR, BAIAP2L1, and UGT2B15. These genes represent a wide range of biologic pathways that may relate to SHBG function and sex steroid hormone biology, including liver function, lipid metabolism, carbohydrate metabolism and type 2 diabetes, and the development and progression of sex steroid hormone-responsive cancers.

The European Prospective Investigation into Cancer and nutrition (EPIC) is a long-term, multi-centric prospective study in Europe investigating the relationships between cancer and nutrition. This study has served as a basis for a number of Genome-Wide Association Studies (GWAS) and other types of genetic analyses. Over a period of 5 years, 52,256 EPIC DNA samples have been extracted using an automated DNA extraction platform. Here we have evaluated the pre-analytical factors affecting DNA yield, including anthropometric, epidemiological and technical factors such as center of subject recruitment, age, gender, body-mass index, disease case or control status, tobacco consumption, number of aliquots of buffy coat used for DNA extraction, extraction machine or procedure, DNA quantification method, degree of haemolysis and variations in the timing of sample processing. We show that the largest significant variations in DNA yield were observed with degree of haemolysis and with center of subject recruitment. Age, gender, body-mass index, cancer case or control status and tobacco consumption also significantly impacted DNA yield. Feedback from laboratories which have analyzed DNA with different SNP genotyping technologies demonstrate that the vast majority of samples (approximately 88%) performed adequately in different types of assays. To our knowledge this study is the largest to date to evaluate the sources of pre-analytical variations in DNA extracted from peripheral leucocytes. The results provide a strong evidence-based rationale for standardized recommendations on blood collection and processing protocols for large-scale genetic studies.