LAUSR

Introduction & Objectives: Spermine (Spm) is a typical metabolite that is highly concentrated in healthy prostate epithelium maintaining cell growth and functions. Our previous studies found that Spm was significantly decreased in PCa tissue than in benign prostate tissue, as was the urinary Spm in PCa. This study aimed to reveal the specific role of Spm in PCa. Materials & Methods: In this study, Spm was resupplied to castration-resistant prostate cancer (CRPC) cells (PC3 and DU145). Following Spm treatment, MTT (methyl thiazolyl tetrazolium) and EdU (5-ethynyl-2’-deoxyuridine) assay were used to determine the cell proliferation of CRPC cell lines. Cellular apoptosis, cell cycle distribution and mitochondrial membrane potential were analyzed by flow cytometry. Cellular reactive Oxygen species (ROS) level was measured by fluorescence microscope. mRNA and ATAC sequencing in spermine-treated CRPC cells were performed to reveal the related mechanism for Spm effect. Results: In the in vitro studies, Spm was found to inhibit the cell viability of CRPC cells. Transwell assays demonstrated that Spm impaired migration and invasion ability. And Spm blocked tumor progression by inducing G2/M arrest and cellular apoptosis in CRPC cells dose-dependently. mRNA seq revealed that a series of genes were altered after Spm treatment and indicated the potential functional pathway of Spm might be mitophagy. We integrated mRNA seq data with ATAC seq profiles and accessed those genes regulated by polyamine metabolism and Spm-induced mitophagy. Results showed the sequencing tracks for the HMOX1 locus contain higher ATAC-seq peaks at the promoter under Spm treatment. Spm could affect oxidative phosphorylation which will lead to mitophagy and mitochondrial metabolism by modulating the transcriptional accessibility of genes. After Spm treatment, cellular ROS was upregulated while the mitochondrial membrane potential collapsed. Subsequently, western blot results showed that PINK1-mediated mitophagy related-proteins were significantly regulated. Conclusion: Our results indicated that Spm treatment led to mitochondrial dysfunction and subsequently degraded through mitophagy in CRPC cells. Our findings could provide a theoretical basis and have preliminary clinical implications in developing Spm as a promising agent against CRPC by inducing cellular mitophagy in CRPC cells. Citation Format: Jingkai Sun, Peter Ka-Fung Chiu, Tingting Xie, Jeremy Yuen-Chun Teoh, Chi-Fai Ng. Investigation the function and application of spermine in castration-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 520.