Abstract 2149: West African genetic ancestry and origin of the BRCA1 locus in Jamaican men with high grade prostate cancer
Authors: Gaston Sandra M. , Griswold Anthony J. , Kryvenko Oleksandr N. , Gu Tianjie , Zhang Guan-Nan , Prakash Nachiketh S. , Avda Yuval , Ajami Tarek , Ritch Chad R. 
Published: March 2024

Abstract
Introduction: Men of West African (WA) ancestry are at higher risk for prostate cancer than men of European (EU) or Asian descent. Caribbean populations provide an opportunity to identify potential founder mutations that contribute to cancer risk. Jamaica has among the highest rates of prostate cancer incidence and mortality in the world and the majority of the population are of WA ancestry. However, there is a significant amount of genetic admixture of EU and Asian ancestry from historic migration patterns. Thus, the population provides a unique cohort for studying the complex interplay between genetic ancestry and prostate cancer. In this pilot study, we characterized the overall and gene locus-specific ancestry of Jamaican prostate cancer patients to explore potential associations with clinicopathologic disease features. We specifically focused this analysis on the BRCA1 locus based on its known association with inherited prostate cancer risk and also with breast cancer risk in patients from the Caribbean.
Methods: A retrospective cohort of 31 Jamaican men (non-US citizens/residents) who travelled to the University of Miami (2015-2020) specifically for robotic prostatectomy were included in the analysis. DNA was prepared from normal prostate tissue and analyzed using the Illumina Global Screening Array version 3 with Multi-Disease Drop-In that includes more than 650,000 genetic markers. Both overall genetic ancestry and allele specific ancestries were determined for each study subject. Clinical and pathological features (age, PSA, stage, grade group (GG)) were also recorded and analyzed using descriptive statistics.
Results: Median age was 67 years, median pre-op PSA was 6.7. The majority of patients were cT1c (91%) and GG 2 (29%) on biopsy. On final pathology most men were ≥pT3 (51%) and the proportion of GG 1, 2 and ≥ 3 was 3%, 52% and 45% respectively. The mean overall West African genetic ancestry was 51.2% (SD 28.4%). Overall % West African ancestry was not associated with pathological GG. In contrast, 50% of the men who were homozygous for African ancestry alleles at the BRCA1 locus had high-grade prostate cancer (GG 3, 4, 5) versus 37% of the men with non-African or heterozygous BRCA1 genotypes.
Conclusions: In a select cohort of Jamaican men, we found that half of patients with BRCA1 alleles derived from West African ancestry also have high grade prostate cancer. BRCA1 of African ancestral origin may contribute to the relatively high prevalence of aggressive prostate cancer in men from Jamaica. Work in progress focuses on an expanded study of associations between allele-specific genetic ancestry and prostate cancer in high-risk populations.
Citation Format: Sandra M. Gaston, Anthony J. Griswold, Oleksandr N. Kryvenko, Tianjie Gu, Guan-Nan Zhang, Nachiketh S. Prakash, Yuval Avda, Tarek Ajami, Chad R. Ritch. West African genetic ancestry and origin of the BRCA1 locus in Jamaican men with high grade prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2149.