THU476 Role Of Mitochondrial Sirtuins 3 And 5 On Glutamine Addiction In Prostate Cancer Cell

Abstract

Abstract Disclosure: K.M. Hasan: None. T.C. Friedman: None. W. Chen: None. Myc-transformed and hypoxic cancer cells are sensitive to glutamine deprivation. Reprogramming to glutamine addiction helps to maintain the TCA cycle pool and anaplerosis that provide cancer cells energy and various macromolecules critical for rapid proliferation. However, the mechanism of glutamine addiction has yet to be fully understood. Here we explore the effect of mitochondrial sirtuins (Sirt3 and Sirt5) on glutamine metabolism in prostate cancer (PCa) cell. We used lentiviral-based knockdown or overexpression methods to examine the effect of Sirt3 and Sirt5 on the growth and proliferation of PC3 and LnCap cells. Cells were grown in both regular or glutamine-free liquid and soft agar media to investigate the effect of Sirt3 and Sirt5 on anchorage-dependent or independent growth, respectively. Cells after the knockdown of Sirt3 and Sirt5 were also grown in media supplemented with cell permeable dimethyl ketoglutarate (DMK), an alternative to ketoglutarate to continue the TCA cycle in the absence of active glutamine metabolism. We showed that anchorage-independent growth (AIG) of PCa cells relied on mitochondrial sirtuins (mtSirts). Inhibition of Sirt3 and Sirt5 activity impaired AIG, and the inhibitory effect was rescued by supplying DMK, suggesting the impact of mtSirts on glutamine metabolism. Most intriguing, our results demonstrated that Sirt3 overexpression enhanced AIG, which can be suppressed by knockdown glutamate dehydrogenase (GDH), suggesting that Sirt3 upregulated glutamine metabolism through GDH activation. Indeed, we found that silencing of Sirt3 and Sirt5 induced the acetylation of GDH and decreased the GDH activity. In agreement, we further observed that glutamine was essential for AIG of prostate cancer cells, and the addition of DMK in a glutamine-free medium rescued the growth, implying that PCa cells are addicted to glutamine. Finally, we showed that the knockdown of Sirt3 and Sirt5 impaired the tumorigenicity of PC3 cells in vivo mouse xenograft model. Thus, we concluded that sirtuins-mediated GDH regulation is a crucial process in the metabolic adaptation of PCa cells that can be a therapeutic target. Presentation: Thursday, June 15, 2023