Simple SummaryAfrican ancestry is a significant risk factor for aggressive prostate cancer (PCa), with southern African ethnicity conferring a nearly 3-fold increased global risk for associated mortality. It is well understood that epigenetic alterations drive PCa initiation and progression, coupled with somatic alterations in genes encoding epigenetic enzymes. However, differences in the somatic alterations in these genes in African- versus European-derived prostate tumors and how they may contribute to PCa health disparities has yet to be investigated, which forms the objective of this study. With current PCa care almost exclusively based on and tailored for men of European ancestry, the identification of African-specific novel PCa epigenetic cancer drivers (n= 18), including therapeutic potential (6/18), offers clinical significance with the possibility of improving healthcare approaches and health outcomes for men of African ancestry.AbstractProstate cancer is driven by acquired genetic alterations, including those impacting the epigenetic machinery. With African ancestry as a significant risk factor for aggressive disease, we hypothesize that dysregulation among the roughly 656 epigenetic genes may contribute to prostate cancer health disparities. Investigating prostate tumor genomic data from 109 men of southern African and 56 men of European Australian ancestry, we found that African-derived tumors present with a longer tail of epigenetic driver gene candidates (72 versus 10). Biased towards African-specific drivers (63 versus 9 shared), many are novel to prostate cancer (18/63), including several putative therapeutic targets (CHD7,DPF3,POLR1B,SETD1B,UBTF, andVPS72). Through clustering of all variant types and copy number alterations, we describe two epigenetic PCa taxonomies capable of differentiating patients by ancestry and predicted clinical outcomes. We identified the top genes in African- and European-derived tumors representing a multifunctional “generic machinery”, the alteration of which may be instrumental in epigenetic dysregulation and prostate tumorigenesis. In conclusion, numerous somatic alterations in the epigenetic machinery drive prostate carcinogenesis, but African-derived tumors appear to achieve this state with greater diversity among such alterations. The greater novelty observed in African-derived tumors illustrates the significant clinical benefit to be derived from a much needed African-tailored approach to prostate cancer healthcare aimed at reducing prostate cancer health disparities.