[Show abstract][Hide abstract] ABSTRACT: BACKGROUND: Mammographic breast density and endogenous sex-hormone levels are both strong risk factors for breast cancer. This study investigated whether there is evidence for a shared genetic basis between these risk factors. METHODS: Using data on 1286 women from 617 families we estimated the heritabilities of serum estradiol, testosterone and sex-hormone binding globulin (SHBG) levels and of three measures of breast density (dense area, non-dense area and percent density). We tested for associations between hormone levels and density measures, and estimated the genetic and environmental correlations between pairs of traits using variance and co-variance components models and pedigree-based maximum likelihood methods. RESULTS: We found no significant associations between estradiol, testosterone or SHBG levels and any of the three density measures, after adjusting for BMI. The estimated heritabilities were 63%, 66% and 65% for square-root transformed adjusted percent-density, dense area and non-dense area respectively, and 40%, 25% and 58% for log-transformed adjusted estradiol, testosterone and SHBG. We found no evidence of a shared genetic basis between any hormone levels and any measure of density, after adjusting for BMI. The negative genetic correlation between dense and non-dense areas remained significant even after adjustment for BMI and other covariates (p=-0.34, se=0.08, P=0.0005). Conclusions and Impact: Breast density and sex hormones can thus be considered as independent sets of traits, each of which can be used as intermediate phenotypes in the search for breast cancer susceptibility loci.
Full-text · Article · Oct 2012 · Cancer Epidemiology Biomarkers & Prevention
[Show abstract][Hide abstract] ABSTRACT: Genome-wide association studies (GWAS) have successfully identified common genetic variants that contribute to breast cancer risk. Discovering additional variants has become difficult, as power to detect variants of weaker effect with present sample sizes is limited. An alternative approach is to look for variants associated with quantitative traits that in turn affect disease risk. As exposure to high circulating estradiol and testosterone, and low sex hormone-binding globulin (SHBG) levels is implicated in breast cancer etiology, we conducted GWAS analyses of plasma estradiol, testosterone, and SHBG to identify new susceptibility alleles. Cancer Genetic Markers of Susceptibility (CGEMS) data from the Nurses' Health Study (NHS), and Sisters in Breast Cancer Screening data were used to carry out primary meta-analyses among ~1600 postmenopausal women who were not taking postmenopausal hormones at blood draw. We observed a genome-wide significant association between SHBG levels and rs727428 (joint β = -0.126; joint P = 2.09 × 10(-16)), downstream of the SHBG gene. No genome-wide significant associations were observed with estradiol or testosterone levels. Among variants that were suggestively associated with estradiol (P<10(-5)), several were located at the CYP19A1 gene locus. Overall results were similar in secondary meta-analyses that included ~900 NHS current postmenopausal hormone users. No variant associated with estradiol, testosterone, or SHBG at P<10(-5) was associated with postmenopausal breast cancer risk among CGEMS participants. Our results suggest that the small magnitude of difference in hormone levels associated with common genetic variants is likely insufficient to detectably contribute to breast cancer risk.
[Show abstract][Hide abstract] ABSTRACT: Percent mammographic density adjusted for age and body mass index (BMI) is one of the strongest risk factors for breast cancer
and has a heritable component that remains largely unidentified. We performed a three-stage genome-wide association study
(GWAS) of percent mammographic density to identify novel genetic loci associated with this trait. In stage 1, we combined
three GWASs of percent density comprised of 1241 women from studies at the Mayo Clinic and identified the top 48 loci (99
single nucleotide polymorphisms). We attempted replication of these loci in 7018 women from seven additional studies (stage
2). The meta-analysis of stage 1 and 2 data identified a novel locus, rs1265507 on 12q24, associated with percent density,
adjusting for age and BMI (P = 4.43 × 10−8). We refined the 12q24 locus with 459 additional variants (stage 3) in a combined analysis of all three stages (n = 10 377) and confirmed that rs1265507 has the strongest association in the 12q24 region (P = 1.03 × 10−8). Rs1265507 is located between the genes TBX5 and TBX3, which are members of the phylogenetically conserved T-box gene family and encode transcription factors involved in developmental
regulation. Understanding the mechanism underlying this association will provide insight into the genetics of breast tissue
Full-text · Article · Apr 2012 · Human Molecular Genetics
[Show abstract][Hide abstract] ABSTRACT: Mammographic density adjusted for age and body mass index (BMI) is a heritable marker of breast cancer susceptibility. Little is known about the biologic mechanisms underlying the association between mammographic density and breast cancer risk. We examined whether common low-penetrance breast cancer susceptibility variants contribute to interindividual differences in mammographic density measures.
We established an international consortium (DENSNP) of 19 studies from 10 countries, comprising 16,895 Caucasian women, to conduct a pooled cross-sectional analysis of common breast cancer susceptibility variants in 14 independent loci and mammographic density measures. Dense and nondense areas, and percent density, were measured using interactive-thresholding techniques. Mixed linear models were used to assess the association between genetic variants and the square roots of mammographic density measures adjusted for study, age, case status, BMI, and menopausal status.
Consistent with their breast cancer associations, the C-allele of rs3817198 in LSP1 was positively associated with both adjusted dense area (P = 0.00005) and adjusted percent density (P = 0.001), whereas the A-allele of rs10483813 in RAD51L1 was inversely associated with adjusted percent density (P = 0.003), but not with adjusted dense area (P = 0.07).
We identified two common breast cancer susceptibility variants associated with mammographic measures of radiodense tissue in the breast gland.
We examined the association of 14 established breast cancer susceptibility loci with mammographic density phenotypes within a large genetic consortium and identified two breast cancer susceptibility variants, LSP1-rs3817198 and RAD51L1-rs10483813, associated with mammographic measures and in the same direction as the breast cancer association.
Full-text · Article · Mar 2012 · Cancer Epidemiology Biomarkers & Prevention
[Show abstract][Hide abstract] ABSTRACT: Percent mammographic breast density (PMD) is a strong heritable risk factor for breast cancer. However, the pathways through which this risk is mediated are still unclear. To explore whether PMD and breast cancer have a shared genetic basis, we identified genetic variants most strongly associated with PMD in a published meta-analysis of five genome-wide association studies (GWAS) and used these to construct risk scores for 3,628 breast cancer cases and 5,190 controls from the UK2 GWAS of breast cancer. The signed per-allele effect estimates of single-nucleotide polymorphisms (SNP) were multiplied with the respective allele counts in the individual and summed over all SNPs to derive the risk score for an individual. These scores were included as the exposure variable in a logistic regression model with breast cancer case-control status as the outcome. This analysis was repeated using 10 different cutoff points for the most significant density SNPs (1%-10% representing 5,222-50,899 SNPs). Permutation analysis was also conducted across all 10 cutoff points. The association between risk score and breast cancer was significant for all cutoff points from 3% to 10% of top density SNPs, being most significant for the 6% (2-sided P = 0.002) to 10% (P = 0.001) cutoff points (overall permutation P = 0.003). Women in the top 10% of the risk score distribution had a 31% increased risk of breast cancer [OR = 1.31; 95% confidence interval (CI), 1.08-1.59] compared with women in the bottom 10%. Together, our results show that PMD and breast cancer have a shared genetic basis that is mediated through a large number of common variants.
[Show abstract][Hide abstract] ABSTRACT: Two single nucleotide polymorphisms (SNPs) at 6q25.1, near the ESR1 gene, have been implicated in the susceptibility to breast cancer for Asian (rs2046210) and European women (rs9397435). A
genome-wide association study in Europeans identified two further breast cancer susceptibility variants: rs11249433 at 1p11.2
and rs999737 in RAD51L1 at 14q24.1. Although previously identified breast cancer susceptibility variants have been shown to be associated with breast
cancer risk for BRCA1 and BRCA2 mutation carriers, the involvement of these SNPs to breast cancer susceptibility in mutation carriers is currently unknown.
To address this, we genotyped these SNPs in BRCA1 and BRCA2 mutation carriers from 42 studies from the Consortium of Investigators of Modifiers of BRCA1/2. In the analysis of 14 123 BRCA1 and 8053 BRCA2 mutation carriers of European ancestry, the 6q25.1 SNPs (r2 = 0.14) were independently associated with the risk of breast cancer for BRCA1 mutation carriers [hazard ratio (HR) = 1.17, 95% confidence interval (CI): 1.11–1.23, P-trend = 4.5 × 10−9 for rs2046210; HR = 1.28, 95% CI: 1.18–1.40, P-trend = 1.3 × 10−8 for rs9397435], but only rs9397435 was associated with the risk for BRCA2 carriers (HR = 1.14, 95% CI: 1.01–1.28, P-trend = 0.031). SNP rs11249433 (1p11.2) was associated with the risk of breast cancer for BRCA2 mutation carriers (HR = 1.09, 95% CI: 1.02–1.17, P-trend = 0.015), but was not associated with breast cancer risk for BRCA1 mutation carriers (HR = 0.97, 95% CI: 0.92–1.02, P-trend = 0.20). SNP rs999737 (RAD51L1) was not associated with breast cancer risk for either BRCA1 or BRCA2 mutation carriers (P-trend = 0.27 and 0.30, respectively). The identification of SNPs at 6q25.1 associated with breast cancer risk for BRCA1 mutation carriers will lead to a better understanding of the biology of tumour development in these women.
Full-text · Article · Jun 2011 · Human Molecular Genetics
[Show abstract][Hide abstract] ABSTRACT: High-percent mammographic density adjusted for age and body mass index is one of the strongest risk factors for breast cancer. We conducted a meta analysis of five genome-wide association studies of percent mammographic density and report an association with rs10995190 in ZNF365 (combined P = 9.6 × 10(-10)). Common variants in ZNF365 have also recently been associated with susceptibility to breast cancer.
[Show abstract][Hide abstract] ABSTRACT: A recent study reported genetic variants in the TERT-CLPTM1L locus that were associated with mean telomere length, and with risk of multiple cancers.
We evaluated the association between single nucleotide polymorphism (SNP) rs401681 (C > T) and mean telomere length, using quantitative real-time PCR, in blood-extracted DNA collected from 11,314 cancer-free participants from the Sisters in Breast Screening study, the Melanoma and Pigmented Lesions Evaluative Study melanoma family study, and the SEARCH Breast, Colorectal, Melanoma studies. We also examined the relationship between rs401618 genotype and susceptibility to breast cancer (6,800 cases and 6,608 controls), colorectal cancer (2,259 cases and 2,181 controls), and melanoma (787 cases and 999 controls).
The "per T allele" change in mean telomere length (DeltaCt), adjusted for age, study plate, gender, and family was 0.001 [95% confidence intervals (CI), 0.01-0.02; P trend = 0.61]. The "per T allele" odds ratio for each cancer was 1.01 for breast cancer (95% CI, 0.96-1.06; P trend = 0.64), 1.02 for colorectal cancer (95% CI, 0.94-1.11; P trend = 0.66), and 0.99 for melanoma (95% CI, 0.84-1.15; P trend = 0.87).
We found no evidence that this SNP was associated with mean telomere length, or with risk of breast cancer, colorectal cancer, or melanoma.
Our results indicate that the observed associations between rs401681 and several cancer types might be weaker than previously described. The lack of an association in our study between this SNP and mean telomere length suggests that any association with cancer risk at this locus is not mediated through TERT.
[Show abstract][Hide abstract] ABSTRACT: Mammographic breast density (MBD) has a strong genetic component. Investigating the genetic models for mammographic density may provide further insights into the genetic factors affecting breast cancer risk.
To evaluate the familial aggregation of MBD and investigate the genetic models of susceptibility.
We used data on 746 women from 305 families participating in the Sisters in Breast Screening study. Retrieved mammograms were digitized, and percent mammographic density was determined using the Cumulus software. Linear regression analysis was done to identify the factors that are associated with mammographic density and a multivariate regression model was constructed. Familial correlations between relative pairs were calculated using the residuals from these models. Genetic models of susceptibility were investigated using segregation analysis.
After adjusting for covariates, the intraclass correlation coefficient among the residuals was 0.26 (95% confidence interval, 0.16-0.36) in sister-sister pairs and 0.67 (0.27-1.00) among the monozygotic twin pairs. The most parsimonious model was a Mendelian single major gene model in which an allele with population frequency 0.39 (95% confidence interval, 0.33-0.46) influenced mammographic density in an additive fashion. This model explained 66% of the residual variance.
These results confirm that MBD has a strong heritable basis, and suggest that major genes may explain some of the familial aggregation. These results may have implications for the search of genes that control mammographic density.
Full-text · Article · May 2009 · Cancer Epidemiology Biomarkers & Prevention
[Show abstract][Hide abstract] ABSTRACT: Constitutive activation of the RET receptor tyrosine kinase underlies the genesis and progression of multiple endocrine neoplasia type 2 (MEN 2), a dominantly inherited cancer predisposition. Importantly, although kinase activation represents a common theme in neoplasias, not all activating mutations are functionally equivalent. Consistent with this, we ascertained a patient with classical features of MEN 2B, but lacking either of the classical mutations in RET (M918T or A883F). Instead, the patient harbors a novel pair of germ line missense mutations in cis at codons 804 and 805. We evaluated the potential physiochemical effects of these substitutions in silico, predicting both to be moderately deleterious in isolation, but severely deleterious in combination. Consistent with this postulate, we show that the identified tandem mutations (V804M/E805K) are biologically active, transforming cells in culture and that their transforming capacity in combination is distinctly synergistic. Furthermore, the V804M/E805K tandem lesion confers resistance to the small molecule receptor tyrosine kinase inhibitor, PP1, suggesting a mode of action distinct from that known for classical MEN 2B mutations. To address this question, we used homology molecular modeling in silico to model the active site of RET. We predict that RET804 constitutes a critical gatekeeper residue that, when mutated in combination with RET805, induces a conformational change in the hinge region that locks the active site in a position permissive for ATP hydrolysis. Our findings have implications both in the clinic and in the successful development of novel kinase-targeted anticancer drugs.
[Show abstract][Hide abstract] ABSTRACT: We report the finding of a novel missense mutation at codon 833 in the tyrosine kinase of the RET proto-oncogene in a patient with a carcinoma of the thyroid. In vitro experiments demonstrate that the R833C mutation induces transformed foci only when present in the long 3' splice isoform and, in keeping with a model in which the receptor has to dimerize to be completely activated, glial cell line-derived neurotrophic factor stimulation leads the RET(R833C) receptor to a higher level of activation. Tyrosine kinase assays show that the RET(R833C) long isoform has weak intrinsic kinase activity and phosphorylation of an exogenous substrate is not elevated even in the presence of glial cell line-derived neurotrophic factor. Furthermore, the R833C mutation is capable of sustaining the transformed phenotype in vivo but does not confer upon the transformed cells the ability to degrade the basement membrane in a manner analogous to metastasis. Our functional characterization of the R833C substitution suggests that, like the V804M and S891A mutations, this tyrosine kinase mutation confers a weak activating potential upon RET. This is the first report demonstrating that the introduction of an intracellular cysteine can activate RET. However, this does not occur via dimerization in a manner analogous to the extracellular cysteine mutants.
[Show abstract][Hide abstract] ABSTRACT: Germ line missense mutations in the RET proto-oncogene are responsible for the inherited cancer syndrome multiple endocrine neoplasia type 2A (MEN2A). The clinical presentation of the disease and the age at onset varies even within families, where patients carry the same mutation. These variations in phenotypes suggest a role for genetic modifiers, and recently, it has been reported that polymorphisms within RET (G691S/S904S) may have such a modifier effect on the age at onset. Here, we investigate whether this observed association could be confirmed in a larger set of 384 individuals from MEN2 families from four different European populations. In addition, we tested as modifiers four other single nucleotide polymorphisms (SNPs), which we have found in a previous association study of RET, its coreceptors, and ligands to be associated with the risk of developing sporadic medullary thyroid carcinoma. We could not replicate the association between G691S/S904S and modifier effects in MEN2A families in any of the four European families analyzed. Of the other SNPs tested, only RET A432A showed a positive weak effect on tumor spectrum within MEN2A, which requires replication in a larger series.
[Show abstract][Hide abstract] ABSTRACT: Medullary thyroid carcinoma (MTC) is a characteristic tumor occurring in individuals with multiple endocrine neoplasia type 2 who carry germ-line mutations in RET (rearranged during transfection). However, most MTC occur in individuals without a family history.
The objective of this study was to explore the possibility that susceptibility in these cases results from low penetrance alleles of RET, its coreceptors, and ligands.
We carried out an association study in 135 sporadic MTC (sMTC) patients and 533 controls from the United Kingdom population.
We analyzed 33 polymorphisms in all nine genes involved in the glial cell line-derived neurotropic factor receptor-alpha (GFRalpha)-RET complex. This is the first association study in which all genes involved in this complex have been investigated for susceptibility to sMTC. We did not find any association between single nucleotide polymorphisms in the exonic regions of the GFRalpha2, GFRalpha3, GFRalpha4, glial cell line-derived neurotropic factor, neurturin, or persephin genes and risk of developing sMTC. We found a strong association between the disease and specific haplotypes of RET. We not only confirmed the previously described association with G691S and S904S (for heterozygotes: odds ratio, 1.85; range, 1.22-2.82; P = 0.004), but we found a novel protective effect associated with a specific haplotype (odds ratio, 0.39; range, 0.21-0.72; P = 0.005) revealing the existence of different genetic variants in the RET oncogene that either increase or decrease risk of sMTC.
Full-text · Article · Dec 2005 · Journal of Clinical Endocrinology & Metabolism
[Show abstract][Hide abstract] ABSTRACT: The effect of mutations at codon 804 in the RET protooncogene is disputed. Some studies have suggested that the V804L mutation causes the low penetrance multiple endocrine neoplasia type 2 syndrome, with late onset and relatively indolent course, whereas others have reported that V804L and V804M have an aggressive potential. In this paper, we report three apparently unrelated medullary thyroid carcinoma cases homozygous for these mutations. To clarify the phenotypic heterogeneity associated with these mutations, we compare the clinical data and age of diagnosis among these three homozygous patients, six other heterozygous cases from the same populations, and other homozygous and heterozygous subjects reported previously. The data are consistent with a model in which codon 804 mutations have low penetrance, the developing of medullary thyroid carcinoma being associated with a second germline or somatic mutation. The activity and (in the case of somatic mutations) timing of these other genetic alterations in the RET gene may explain the wide clinical variability associated with germline mutations at codon 804.
[Show abstract][Hide abstract] ABSTRACT: Percent mammographic breast density (PMD) is a strong heritable risk factor for breast cancer. However, the pathways through which this risk is mediated are still unclear. To explore whether PMD and breast cancer have a shared genetic basis, we identified genetic variants most strongly associated with PMD in a published meta-analysis of five genome-wide association studies (GWAS) and used these to construct risk scores for 3,628 breast cancer cases and 5,190 controls from the UK2 GWAS of breast cancer. The signed per-allele effect estimates of single-nucleotide polymorphisms (SNP) were multiplied with the respective allele counts in the individual and summed over all SNPs to derive the risk score for an individual. These scores were included as the exposure variable in a logistic regression model with breast cancer case-control status as the outcome. This analysis was repeated using 10 different cutoff points for the most significant density SNPs (1%-10% representing 5,222-50,899 SNPs). Permutation ana