Association of rare, recurrent nonsynonymous variants in the germline of prostate cancer patients of African ancestry.

BACKGROUND: Although men of African ancestry (AA) have the highest mortality rate from prostate cancer (PCa), relatively little is known about the germline variants that are associated with PCa risk in AA men. The goal of this study is to systematically evaluate rare, recurrent nonsynonymous variants across the exome for their association with PCa in AA men. METHODS: Whole exome sequencing (WES) of germline DNA in two AA PCa patient cohorts of Johns Hopkins Hospital (N = 960) and Wayne State University (N = 747) was performed. All nonsynonymous variants present in both case cohorts, with a carrier rate between 0.5% and 1%, were identified. Their carrier rates were compared with rates from 8128 African/African American (AFR) control subjects from The Genome Aggregation Database (gnomAD) using Fisher's exact test. Significant variants, defined as false discovery rate (FDR) adjusted p-value ≤ 0.05, were further evaluated in AA PCa cases (N = 132) and controls (N = 1184) from the UK Biobank (UKB). RESULTS: Two variants reached a pre-specified statistical significance level. The first was p.R14Q in GPRC5C (found in 0.47% of PCa cases and 0.01% of population controls); odds ratio (OR) for PCa was 37.46 (95% confidence interval CI 4.68-299.72), pexact = 7.01E-06, FDR-adjusted p-value = 0.05. The second was p.R511Q in IGF1R (found in 0.53% of PCa cases and 0.01% of population controls); OR for PCa was 21.54 (95%CI 4.65-99.76), pexact = 5.51E-06, FDR-adjusted p-value = 0.05. The mean percentage of African ancestry was similar between variant carriers and noncarriers of each variant, p > 0.05. In the UKB AA men, GPRC5C R14Q was 0.76% and 0.08% in cases and controls, respectively, OR for PCa was 9.00 (95%CI 0.56-145.23), pexact = 0.19. However, IGF1R R511Q was not found in cases or controls. CONCLUSIONS: This WES study identified two rare, recurrent nonsynonymous PCa risk-associated variants in AA. Confirmation in additional large populations of AA PCa cases and controls is required.

The HOXB13 variant X285K is associated with clinical significance and early age at diagnosis in African American prostate cancer patients.

BACKGROUND: Recently, a novel HOXB13 variant (X285K) was observed in men of African descent with prostate cancer (PCa) in Martinique. Little is known about this or other variants in HOXB13 which may play a role in PCa susceptibility in African-American (AA) men. METHODS: We sequenced HOXB13 in an AA population of 1048 men undergoing surgical treatment for PCa at Johns Hopkins Hospital. RESULTS: Seven non-synonymous germline variants were observed in the patient population. While six of these variants were seen only once, X285K was found in eight patients. In a case-case analysis, we find that carriers of this latter variant are at increased risk of clinically significant PCa (1.2% carrier rate in Gleason Score ≥7 PCa vs. 0% in Gleason Score <7 PCa, odds ratio, OR = inf; 95% Confidence Interval, 95%CI:1.05-inf, P = 0.028), as well as PCa with early age at diagnosis (2.4% carrier rate in patients <50 year vs. 0.5% carrier rate in patients ≥50 year, OR = 5.25, 95% CI:1.00-28.52, P = 0.03). CONCLUSIONS: While this variant is rare in the AA population (~0.2% MAF), its ancestry-specific occurrence and apparent preferential association with risk for the more aggressive disease at an early age emphasizes its translational potential as an important, novel PCa susceptibility marker in the high-risk AA population.