Abstract 1157: Uncovering a novel role of peroxisomal β-oxidation in advanced, treatment-resistant prostate cancer
Authors: Mah Chui Yan , Nguyen An D. , Niijima Takuto , Helm Madison , Dehairs Jonas , Ryan Feargal J. , Ryan Natalie , Mills Ian G. , Swinnen Johannes V. , Lynn David J. , Nassar Zeyad D. , Butler Lisa M. 
Published: April 2023

Background and Aims: Prostate cancer (PCa) is highly reliant on lipids for energy, hence targeting fatty acid oxidation (FAO) is a highly promising approach to the treatment of PCa. Recent work by our group and others have shown that FAO is critical for cell viability and survival, and is one of the key drivers of treatment resistance. Although FAO occurs in both the mitochondria and peroxisomes, the functional relevance and therapeutic exploitability of peroxisomal FAO (perFAO) in PCa has not been extensively explored compared to the mitochondria. Herein, we aim to investigate the therapeutic efficacy of targeting perFAO in clinical prostate tumors and PCa cells, and explore its role in PCa progression.

Methods and Results: Pharmacological inhibition of perFAO using the clinical agent, thioridazine, significantly suppressed proliferation, migration, and colony formation of a range of advanced and treatment-resistant PCa cells. Further, we evaluated the therapeutic efficacy of thioridazine in a more clinically relevant setting using patient-derived tissues and showed a significant inhibition of cell proliferation (n = 11, p &lt; 0.05). Next, we performed a bioinformatics analysis of clinical RNAseq datasets composed of primary and metastatic PCa tissues and identified DECR2, the auxiliary enzyme of perFAO, as a key target of perFAO in PCa. DECR2 is overexpressed in metastatic castrate-resistant PCa (CRPC) tissues compared to primary PCa and benign tissues, and is significantly associated with shorter relapse-free survival (p &lt; 0.01). DECR2 knockdown significantly suppressed proliferation and migration of CRPC and enzalutamide-resistant PCa cells, and markedly reduced LNCaP tumor growth in vivo. In contrast, overexpression of DECR2 in LNCaP cells significantly increased tumor growth in vivo. Interestingly, analysis of a published proteomics dataset of PCa cells that are either androgen-dependent or resistant to androgen receptor (AR) inhibitors revealed a significant correlation of peroxisomal genes (MSigDB) with acquired resistance to AR inhibition. Notably, DECR2 overexpression was significantly associated with shorter overall survival (p &lt; 0.05) in a metastatic CRPC cohort treated with AR inhibitors. We further showed that DECR2 overexpression in LNCaP cells significantly reduced sensitivity to AR inhibitor treatments and androgen-deprivation, suggesting a role for perFAO in promoting survival and treatment resistance.

Conclusion: Our study has revealed a novel role for perFAO in PCa progression and treatment resistance. Importantly, this study also identified DECR2 as a key regulator of tumor cell proliferation and lipid metabolism, representing a potential novel therapeutic target for advanced, treatment-resistant PCa that currently lacks effective targeted therapies.

Citation Format: Chui Yan Mah, An D. Nguyen, Takuto Niijima, Madison Helm, Jonas Dehairs, Feargal J. Ryan, Natalie Ryan, Ian G. Mills, Johannes V. Swinnen, David J. Lynn, Zeyad D. Nassar, Lisa M. Butler. Uncovering a novel role of peroxisomal β-oxidation in advanced, treatment-resistant prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1157.