Anna M. Ray

Germline Mutations in HOXB13 and Prostate-Cancer Risk

BACKGROUND Family history is a significant risk factor for prostate cancer, although the molecular basis for this association is poorly understood. Linkage studies have implicated chromosome 17q21-22 as a possible location of a prostate-cancer susceptibility gene. METHODS We screened more than 200 genes in the 17q21-22 region by sequencing germline DNA from 94 unrelated patients with prostate cancer from families selected for linkage to the candidate region. We tested family members, additional case subjects, and control subjects to characterize the frequency of the identified mutations. RESULTS Probands from four families were discovered to have a rare but recurrent mutation (G84E) in HOXB13 (rs138213197), a homeobox transcription factor gene that is important in prostate development. All 18 men with prostate cancer and available DNA in these four families carried the mutation. The carrier rate of the G84E mutation was increased by a factor of approximately 20 in 5083 unrelated subjects of European descent who had prostate cancer, with the mutation found in 72 subjects (1.4%), as compared with 1 in 1401 control subjects (0.1%) (P=8.5x10(-7)). The mutation was significantly more common in men with early-onset, familial prostate cancer (3.1%) than in those with late-onset, nonfamilial prostate cancer (0.6%) (P=2.0x10(-6)). CONCLUSIONS The novel HOXB13 G84E variant is associated with a significantly increased risk of hereditary prostate cancer. Although the variant accounts for a small fraction of all prostate cancers, this finding has implications for prostate-cancer risk assessment and may provide new mechanistic insights into this common cancer. (Funded by the National Institutes of Health and others.).

Genome-wide association study of prostate cancer in men of African ancestry identifies a susceptibility locus at 17q21

In search of common risk alleles for prostate cancer that could contribute to high rates of the disease in men of African ancestry, we conducted a genome-wide association study, with 1,047,986 SNP markers examined in 3,425 African-Americans with prostate cancer (cases) and 3,290 African-American male controls. We followed up the most significant 17 new associations from stage 1 in 1,844 cases and 3,269 controls of African ancestry. We identified a new risk variant on chromosome 17q21 (rs7210100, odds ratio per allele = 1.51, P = 3.4 × 10−13). The frequency of the risk allele is ∼5% in men of African descent, whereas it is rare in other populations (<1%). Further studies are needed to investigate the biological contribution of this allele to prostate cancer risk. These findings emphasize the importance of conducting genome-wide association studies in diverse populations.

Genetic polymorphisms in CYP17 , CYP3A4 , CYP19A1 , SRD5A2 , IGF-1 , and IGFBP-3 and prostate cancer risk in African-American men: The Flint Men's Health Study

Association studies have examined the significance of several candidate genes based on biological pathways relevant to prostate carcinogenesis, including both the androgen and insulin‐like growth factor pathways. Clinical and epidemiologic evidence suggest that androgens, specifically testosterone and dihydrotestosterone (DHT) are important not only in normal prostate growth but in the pathogenesis of prostate cancer. Similarly, the insulin‐like growth factor‐1 (IGF‐1) signaling pathway regulates both cellular proliferation and apoptosis. Therefore, genes involved in the biosynthesis, activation, metabolism and degradation of androgens and the stimulation of mitogenic and antiapoptotic activities of prostate epithelial cells represent important candidates for affecting the development and progression of prostate cancer.

The androgen receptor CAG and GGN repeat polymorphisms and prostate cancer susceptibility in African-American men: results from the Flint Men’s Health Study

AbstractRepeat lengths of the CAG and GGN microsatellites in exon 1 of the androgen receptor (AR) gene have been hypothesized to be associated with prostate cancer risk. In vitro studies have showed an inverse association between AR CAG and GGN repeat length and activity levels of the AR product. It is known that men of African descent have a higher incidence of and greater mortality from prostate cancer than men of Caucasian or Asian descent and, on average, a smaller number of repeats at AR CAG and GGN. Consistent with these findings, studies have also found increased AR protein expression levels in benign prostatic hyperplasia and prostatic diseased tissues from men of African descent. Despite these findings, limited studies have been conducted to evaluate the association between repeat lengths at AR CAG and prostate cancer risk in African Americans. Our study is the first such study to examine whether repeat length of the AR GGN repeat is associated with prostate cancer risk in African Americans. We found no evidence for an association between AR CAG or GGN repeat lengths and prostate cancer risk in a population-based sample of African Americans.

Chromosome 17q12 variants contribute to risk of early-onset prostate cancer

In a recent genome-wide association study by Gudmundsson and colleagues, two prostate cancer susceptibility loci were identified on chromosome 17q. The first locus, at 17q12, was distinguished by two intronic single-nucleotide polymorphisms (SNPs) in the TCF2 gene (rs4430796 and rs7501939). The second locus was in a gene-poor region of 17q24, where the strongest evidence of association was for SNP rs1859962. To determine if these loci were also associated with hereditary prostate cancer, we genotyped them in a family-based association sample of 403 non-Hispanic white families, including 1,015 men with and without prostate cancer. SNPs rs4430796 and rs7501939, which were in strong linkage disequilibrium (r(2) = 0.68), showed the strongest evidence of prostate cancer association. Using a family-based association test, the A allele of SNP rs4430796 was overtransmitted to affected men (P = 0.006), with an odds ratio of 1.40 (95% confidence interval, 1.09-1.81) under an additive genetic model. Notably, rs4430796 was significantly associated with prostate cancer among men diagnosed at an early (<50 years) but not later age (P = 0.006 versus P = 0.118). Our results confirm the prostate cancer association with SNPs on chromosome 17q12 initially reported by Gudmundsson and colleagues. In addition, our results suggest that the increased risk associated with these SNPs is approximately doubled in individuals predisposed to develop early-onset disease. Importantly, these SNPs do not account for a significant portion of our prior prostate cancer linkage evidence on chromosome 17. Thus, there likely exist one or more additional independent prostate cancer susceptibility loci in this region.

Early Onset Prostate Cancer Has A Significant Genetic Component

Prostate cancer (PCa) affects more than 190,000 men each year with ∼10% of men diagnosed at ≤55 years, that is, early onset (EO) PCa. Based on historical findings for other cancers, EO PCa likely reflects a stronger underlying genetic etiology.

Hereditary prostate cancer as a feature of Lynch Syndrome

Lynch Syndrome is an autosomal dominant condition characterized by early onset colorectal cancer (CRC) and is associated with cancers of the gastrointestinal and reproductive tracts. Germline mutations in DNA mismatch repair (MMR) genes have been causally associated with cancers of Lynch Syndrome. We investigated the occurrence of prostate cancer (PCa) in families with a history of colorectal cancer to assess prostate cancer as a feature of the Lynch Syndrome spectrum. Family pedigrees containing at least one CRC case as well as those meeting guidelines for Lynch Syndrome were identified and tumors were requested from participants who underwent radical prostatectomy (RP). Selected families were analyzed for association with type of PCa and clinical characteristics of aggressive disease. Microsatellite Instability (MSI) analysis was preformed on available tumors and correlated to loss of expression in MMR genes by immunohistochemical (IHC) staining. 95 individuals were identified as members of potential Lynch Syndrome families who underwent RP and 35 tumors from 31 families were received for MSI analysis. Two tumors from two unrelated families with known MMR mutations were MSI-high and one additional case from a third family was MSI-low. The remainder of the prostate cancer cases demonstrated no evidence of MSI. PCa incidence in families enriched for hereditary PCa with a history of Lynch Syndrome cancers is not strongly suggestive of the presence of an MMR mutation. However prostate tumors in known MMR mutation carriers did display MSI and loss of gene expression suggesting that PCa may arise in Lynch Syndrome due to defective DNA mismatch repair.

Genetic variation in adiponectin (ADIPOQ) and the type 1 receptor (ADIPOR1), obesity and prostate cancer in African Americans.

Adiponectin is a protein derived from adipose tissue suspected to have an important role in prostate carcinogenesis. Variants in the adiponectin gene (ADIPOQ) and its type 1 receptor (ADIPOR1) have been recently linked to risk of both breast and colorectal cancer. Therefore, we set out to examine the relationship between polymorphisms in these genes, obesity and prostate cancer in study of African-American men. Ten single-nucleotide polymorphisms (SNPs) in ADIPOQ and ADIPOR1 were genotyped in DNA samples from 131 African-American prostate cancer cases and 344 controls participating in the Flint Mens Health Study. Logistic regression was then used to estimate their association with prostate cancer and obesity. While no significant associations were detected between any of the tested SNPs and prostate cancer, the rs1501299 SNP in ADIPOQ was significantly associated with body mass (P=0.03). Genetic variation in ADIPOQ and ADIPOR1 did not predict risk of prostate cancer in this study of African-American men. However, the rs1501299 SNP in ADIPOQ was associated with obesity. Further investigation is warranted to determine if racial differences exist in the influence of the adiponectin pathway on prostate cancer risk.

Analysis of the Gene Coding for the BRCA2-Interacting Protein PALB2 in Hereditary Prostate Cancer

The genetic basis of susceptibility to prostate cancer (PRCA) remains elusive. Mutations in BRCA2 have been associated with increased prostate cancer risk and account for around 2% of young onset (<56 years) prostate cancer cases. PALB2 is a recently identified breast cancer susceptibility gene whose protein is closely associated with BRCA2 and is essential for BRCA2 anchorage to nuclear structures. This functional relationship made PALB2 a candidate PRCA susceptibility gene.

Genome-wide linkage scan for prostate cancer susceptibility from the University of Michigan Prostate Cancer Genetics Project: suggestive evidence for linkage at 16q23.

Prostate cancer linkage studies have been used to localize rare and presumably highly penetrant cancer susceptibility genes. Underlying genetic heterogeneity, as well as the high sporadic background of the disease, has resulted in many signals that are often not reproducible between research studies.