Abstract A095: Metabolic rewiring in African-American prostate cancer: A role for adenosine-inosine axis in tumor progression
Authors: Charles Christy , Gohlke Jie , Lloyd Stacy , Henderson James , Karanam Balasubramaniam , Navone Nora , Kittles Rick , Ambs Stefan , Michailidis George , Putluri Nagireddy , Sreekumar Arun 
Published: September 2020

Introduction: Prostate cancer (PCa) prevalence and mortality are remarkably higher in African-American (AA)men compared to European-American (EA) men. In addition to known differences in socioeconomic status and access to health care, there is increasing evidence to suggest biological differences between AA and EA PCa. Our lab has pioneered the understanding of reprogrammed metabolism, a hallmark of tumor progression, in AA and EA PCa. Analysis of a compendium of 190 metabolites in ancestry verified, pathologically confirmed AA and EA PCa tissues followed by validation of key pathway components in plasma and urine revealed high inosine to adenosine ratio in AA PCa compared to EA PCa. Consistent with this, the enzyme adenosine deaminase (ADA), which converts adenosine to inosine was also found to be elevated in AA PCa. The current study will address the role of adenosine-inosine axis in AA PCa progression and attempt to delineate its significance in the clinical setting. Methods: Analysis of metabolites in tissues, plasma and urine was done using LC/MS. Tissue microarray analysis (TMA) was done to check the expression of ADA in tissues and correlate it to clinical outcomes. To determine the function of ADA in PCa progression, the gene was overexpressed in MDA-PCa-2A (AA) and LNCaP (EA) cells using lentiviral transduction (termed ADA OE). In vitro invasion was assessed using Boyden chamber assay and in vivo tumorigenic properties were examined in nude mice. Molecular studies were performed using qPCR, ELISA and western blotting. Results: Overexpression of the enzyme ADA in PCa cells confers an anchorage-independent growth phenotype (a.k.a. Anoikis Resistance) associated with a reduction in Integrin β1 (ITGB1) levels. Anoikis resistance is a key prerequisite for metastasis and a hallmark of circulating tumor cells (CTCs). ADA OE AA cells exhibited higher invasive potential compared to the EA cells. Molecular analysis revealed downregulation E-cadherin (epithelial marker) and Bim (pro-apoptotic marker), and upregulation of XIAP (anti-apoptotic marker), all of which support anoikis resistance phenotype in these cells. ADA OE cells had reduced cAMP levels, and addition of external cAMP resulted in reversal of anoikis resistance, increased cell adhesion and rescued ITGB1 levels. Mechanistically, it is postulated that high inosine upon ADA OE activates adenosine receptors A1 and A3, which causes a decrease in cAMP levels. Decreased cAMP affects the Epac-Rap1 signaling, a key regulator of integrin-mediated adhesion. Concomitantly, ADA OE cells also showed a decrease in Rap1 levels. Conclusion: Elevated inosine to adenosine ratio associated with increased expression of ADA is a metabolic hallmark in AA PCa, associated with anoikis resistance and possibly increased CTCs. Our findings also strongly support the potential of using inosine to adenosine ratio in plasma or urine as a predictive marker for PCa incidence or progression in AA men. In addition, ADA could serve as a potential therapeutic target for AA PCa.

Citation Format: Christy Charles, Jie Gohlke, Stacy Lloyd, James Henderson, Balasubramaniam Karanam, Nora Navone, Rick Kittles, Stefan Ambs, George Michailidis, Nagireddy Putluri, Arun Sreekumar. Metabolic rewiring in African-American prostate cancer: A role for adenosine-inosine axis in tumor progression [abstract]. In: Proceedings of the Twelfth AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2019 Sep 20-23; San Francisco, CA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2020;29(6 Suppl_2):Abstract nr A095.