Abstract PO-137: Comparative transcriptomic analysis of prostate cancer from African American and Caucasian American men by Gleason score and race
Authors: Abo Muthana Al , Foo Wen-Chi , George Daniel J. , Patierno Steven R. , Freedman Jennifer A. 
Published: January 2022

Abstract
African American (AA) men exhibit 2-3 times higher mortality from prostate cancer compared with Caucasian American (CA) men. Factors contributing to the disparity include societal-, neighborhood- and institutional-level determinants of health. In addition, a number of studies have reported individual-level ancestry-related biological differences, including in mutations, copy number variation, aggregate gene expression and response to treatment between AA and CA prostate cancer patients. Previously, by comparing the transcriptome between 20 AA and 15 CA prostate cancer patients, we identified a large number of race-related Alternative RNA Splicing (ARS) events. Among these, we further demonstrated that an exon skipping event involving exon 20 within PIK3CD increased tumor growth rate, metastatic potential and drug resistance in prostate cancer. To expand our previous findings, we collected non-neoplastic and tumor-paired tissue from 37 AA and 40 CA prostate cancer patients with different Gleason score categories: 14 high grade (4 AA and 10 CA), 22 low grade (10 AA and 12 CA), and 41 intermediate grade (23 AA and 18 CA). DNA and RNA were isolated for ancestral genotyping and RNA seq analysis, respectively. To achieve RNA sequencing depth adequate for ARS analysis, we performed RNA seq of 150 bp paired-end and an average of 5 × 106 reads per sample. The read alignment was done using Star 2 TwoPass pipeline. The rMATS pipeline was used for ARS annotation and quantification. We identified 105,403 ARS events, including 60,657 exon skipping, 17,439 alternative acceptor, 12,737 alternative donor, 9,555 retained intron and 5,015 mutually exclusive exon. Using the Wilcoxon rank-sum test, we compared the Percent Spliced In (PSI) between AA and CA of the same Gleason score category and identified ARS events exhibiting ΔPSI &gt; 15% and p-value &lt; 0.05. Specifically, we identified 536 race-related ARS events in high grade, 492 race-related ARS events in low grade, and 447 race-related ARS events in intermediate grade. Gene Ontology analysis demonstrated that the genes undergoing race-related ARS events function in cellular processes relevant to cancer biology, including metabolic processes in low grade, NF-kappaB signaling in intermediate grade and cell motility in high grade. Specific examples of these genes include ERG and PARP2 in high grade, KLK2 and DNMT1 in intermediate grade, and AURKA and SEMA3A in low grade. These findings support a potential role for the ARS process in diversifying gene expression, potentially contributing to prostate cancer aggressiveness in AA patients. The race-related ARS events identified in our work represent potential biomarkers and/or therapeutic targets for precision oncology in the context of prostate cancer. Further analysis of the function of prioritized race-related ARS events and their association with local ancestry is ongoing. Funding: DoD Prostate Cancer Research Program Health Disparity Research Award. NIH Basic Research in Cancer Health Disparities R01 Award. Prostate Cancer Foundation Movember Challenge Award.
Citation Format: Muthana Al Abo, Wen-Chi Foo, Daniel J. George, Steven R. Patierno, Jennifer A. Freedman. Comparative transcriptomic analysis of prostate cancer from African American and Caucasian American men by Gleason score and race [abstract]. In: Proceedings of the AACR Virtual Conference: 14th AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2021 Oct 6-8. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2022;31(1 Suppl):Abstract nr PO-137.