Molecular Profiles of Prostate Cancer in Men of Middle Eastern Ancestry Identifies Key Differences with Western Populations: A Multiethnic SNP Array Study

Background: Our knowledge of prostate cancer (PCa) genomics mainly reflects European (EUR) and Asian (ASN) populations. Our understanding of the influence of Middle Eastern (ME) and African (AFR) ancestry on the mutational profiles of prostate cancer is limited. Design, setting and participants: To characterize genomic differences between ME, EUR, ASN and AFR ancestry, fluorescent in situ hybridization (FISH) studies for NKX3-1 deletions and MYC amplification was carried out on 42 tumors arising in individuals of ME ancestry. These were supplemented by analysis of copy number profiles of 401 tumors of all ancestries. Outcome measurement and statistical analysis: FISH results of NKX3-1 and MYC were assessed in the ME cohort and compared to other ancestries. Gene level copy number aberrations (CNAs) for each sample were statistically compared between ancestry groups. Results and Limitation: NKX3-1 deletions by FISH were observed in 17/42 (17.5%) prostate tumors arising in men of ME ancestry, while MYC amplifications were only observed in 1/42 (0.23%). Using CNAs called from arrays, the incidence of NKX3-1 deletions was significantly lower in ME vs. other ancestries (20% vs. 52%; p = 2.3 x 10-3). No differences in MYC amplifications was noted between the two cohorts using array-based CNAs. Across the genome, tumors arising in men of ME ancestry had fewer CNAs than those of other ancestries (p = 0.014). Additionally, the somatic amplification of 21 specific genes was more frequent in tumors arising in men of ME vs. EUR ancestry (Proportions test; Q < 0.05). Those included amplifications in the glutathione S-transferase family on chromosome 1 (GSTM1, GSTM2, GSTM5) and the IQ Motif Containing family on chromosome 3 (IQCF1, IQCF2, IQCF13, IQCF4, IQCF5, IQCF6). Conclusion: Significant differences in genetic background exists between different ancestries. The lower number of somatic CNAs observed in prostate cancer arising in men of ME ancestry may explain the relatively good prognosis in this population. Larger studies are warranted.