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Abstract Disclosure: P. Cao: None. D. Awad: None. J. Han: None. D.E. Frigo: Grant Recipient; Self; GTx, Inc.. Other; Self; Familial relationship with Biocity Biopharmaceuticals, Hummingbird Bioscience, Bellicum Pharmaceuticals, Maia Biotechnology, Alms Therapeutics, Hinova Pharmaceuticals and Barricade Therapeutics. Ferroptosis induction has recently been recognized as a novel therapeutic approach to alter the outcomes of drug-resistant cancer. Ferroptosis is cell death that is caused by the intracellular accumulation of toxic lipid hydroperoxides. Due to their elevated metabolism, castration-resistant prostate cancer (CRPCs) are highly prone to ferroptosis; yet, many of them manage to avert this cellular fate. We have identified a key enzyme involved in lipid metabolism, adipose triglyceride lipase (ATGL), that engenders CRPCs with the ability to resist ferroptosis. Our data has shown that ATGL deletion by CRISPR-Cas9 knockout method sensitized human CRPC cell lines such as C4-2, C4-2BLT, and PC3 cells to the ferroptosis inducer RSL3. In all cases, RSL3-mediated cell death could be blocked by the antioxidant Ferrostatin-1, confirming ferroptosis as the mechanism of cell death. Knocking out ATGL also augmented the ferroptosis inducer-mediated increase in lipid peroxides as indicated by the increased ratio of oxidized to non-oxidized C11-BODIPY 581/591. With regards to the mechanism for the sensitivity of ATGL KO to ferroptosis induction, previous research has established that the enzyme long-chain acyl-CoA synthetase 4 (ACSL4) is universally essential to facilitate ferroptosis. More specifically, ATGL(PNPLA2) was found to inversely correlate with ACSL4 in the Taylor et al., the TCGA PanCancer Atlas, and Metastatic Prostate Adenocarcinoma (SU2C/PCF Dream Team) datasets in both primary and metastatic tumors. qPCR and western blot analysis of ACSL4 levels further showed that ACSL4 expression is closely tied to the lipase activity of ATGL. Addition of arachidonic acid significantly induced ferroptosis when combined with RSL3 in a dose-dependent manner only in ATGL KO cells. This indicates that PUFAs can render ATGL KO cells even more sensitive to RSL3-induced ferroptosis while cells with functional ATGL remain highly resistant, further reinforcing that ATGL is an essential safeguard of CRPC against ferroptosis. ATGL KO cells also demonstrated sensitivity to the antiandrogen Enzalutamide. The combination of Enzalutamide and RSL3 substantially decreased cell viability in ATGL KO cells as compared to control cells, indicating a strong synergy effect particularly seen in ATGL KO cells. In summary, this work demonstrates that ATGL is an important and novel regulator of ferroptosis in CRPC and supports the use of ferroptosis inducer as a new therapeutic approach in CRPC. Presentation: 6/2/2024
Cao et al. (Tue,) studied this question.