Abstract 3590: Mechanisms and inhibition RIOK2 for obesity-driven prostate cancer

Obesity is associated with greater risk of high-grade prostate cancer (PC), recurrence after therapy, metastases, and PC specific mortality. The fact that obesity is a PC risk factor creates an opportunity to identify and target the mechanisms underlying obesity-enhanced lethal PC. We exploited this link by performing an shRNA in vivo screen in obese mice targeting the entire kinome, which found Right Open Reading Frame Kinase 2 (RIOK2) as essential for PCs in obese mice. We found RIOK2 gene signature is correlated with a 56% increased risk of metastatic PC. Moreover, when we queried only men with a BMI ≥ 30 kg/m2 we found that high levels of RIOK2 gene signature increased the risk of metastasis by an additional 50%. RIOK2, a serine/threonine kinase, is critical for de novo ribosome maturation and assembly, which is essential to maintain the high proliferation rates in cancer cells. Indeed, we found that RIOK2 loss reduced de novo protein synthesis in PC cells and decreased cell viability. Conversely, RIOK2 overexpression enhanced PC cell growth. As our goal is to find actionable PC targets to reduce obesity effects on PC, we conducted a protein structure based compound screen in silico and identified a lead kinase inhibitor of RIOK2 (kiRIOK2). Our lead kiRIOK2 inhibits cell proliferation, protein synthesis, anchorage-independent growth and invasion of multiple PC lines in the µM range. SAR optimized kiRIOK2 have increased efficacy and bioavailability. Our studies are providing probes and mechanistic insights to further investigate the role of RIOK2 in PC biology. In the long-term, this may help mitigate the added risk of obesity on PC metastasis and PC-specific mortality. Citation Format: Everardo Macias, Jiyoon Cho, Drew Rosowicz, Zahra Heidari, Sungyong You, Erick J. Maravilla, Jen-Tsan Chi, Stephen J. Freedland. Mechanisms and inhibition RIOK2 for obesity-driven prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3590.