LAUSR

Advanced prostate cancer (PCa) is currently incurable, and development of novel treatments requires a greater understanding of key pathways that are altered during PCa progression. We have focussed on fatty acid metabolism, as the major source of energy for PCa cells, and have implicated a monounsaturated fatty acid (MUFA), cis-vaccenic acid (cVA), as a critical regulator of PCa cell homeostasis. Production of cVA requires stearoyl-CoA desaturase 1 (SCD1), the enzyme attributed to general MUFA production, and whose activity is important in a range of cancer types. Nonetheless, the specific role of cVA has not previously been studied, in PCa nor cancer more generally. To elucidate the role of cVA in PCa more precisely, we used SCD1 inhibition to study PCa responses to broad MUFA depletion and specific MUFA supplementation, comparing the responses of cVA with its more common structural isomer oleate. To accomplish these aims, we utilised cell line models of PCa (LNCaP, MR49F and V16D) and a benign prostate cell line (PNT1A) to perform cell viability, lipidomic and flow cytometric assays. In addition, responses in clinically-relevant patient-derived tumor explants were measured by proliferative (Ki67) and cell death (CC3) marker staining. Pharmacological SCD1 inhibition (SCDi; A939572) decreased cell viability and increased cell death in PCa cell lines and patient-derived tumor explants, while only minimally affecting the benign prostate cell line PNT1A. Phenotypically, analysis of mitochondrial function and lipidomic changes under SCDi suggested a role for MUFAs in regulating mitochondrial membrane composition via cardiolipins, and oxidative stress levels. This in turn has the potential to regulate cell death, control tumor burden, and influence overall PCa patient survival. Supplementation of cVA or oleate under SCDi demonstrated that only cVA was successful at rescuing cell viability, and cVA, but not oleate, could rescue changes observed in mitochondrial-related lipids, suggesting that cVA regulation of mitochondrial function was a major determinant of its effect on cell viability. Additionally, cVA alone dose-dependently increased PCa cell viability, implicating cVA as an important oncogenic factor. Together, these data identify cVA as a novel substrate required for PCa cell viability, likely via regulation of mitochondrial homeostasis and associated cell death pathways. In summary, this research has revealed more precise insights into the oncogenic effects of an overlooked MUFA, cVA, in PCa, and may uncover new druggable targets that are more selective, to improve treatment options for advanced PCa. Citation Format: Julia S. Scott, Reuben Young, Swati Irani, Jonas Dehairs, Stephen Blanksby, Johannes V. Swinnen, Zeyad D. Nassar, Lisa M. Butler. A fat lot of good: A novel monounsaturated fatty acid promotes prostate cancer growth and survival [abstract]. In: Proceedings of the AACR Special Conference: Advances in Prostate Cancer Research; 2023 Mar 15-18; Denver, Colorado. Philadelphia (PA): AACR; Cancer Res 2023;83(11 Suppl):Abstract nr A031.