The members of the KDM5 family of lysine demethylases are best known for their ability to demethylate di- and trimethylated histone H3 at lysine 4 (H3K4me3). However, recent studies suggest at least three family members (KDM5A, KDM5B and KDM5C) promote prostate cancer growth and progression and may serve as effective therapeutic targets for this disease. Previous work from our laboratory has shown that 2-4(4-methylphenyl)-1,2-benzisothiazol-3(2H)-one (PBIT), a compound that inhibits the enzymatic activity of multiple KDM5 isoforms, reduces the viability of castration-resistant prostate cancer cells. The goal of this study was to further characterize the anti-tumor effects of PBIT within human prostate cancers. Two models of human castration-resistant prostate cancer were used to define the effects of PBIT: the androgen receptor (AR) positive C4-2B cells and the PC3 cells, which express little to no AR. Our group initially demonstrated via quantitative RT-PCR analysis that PC3 and C4-2B cells express varying amounts of KDM5A, KDM5B, and KDM5C, the therapeutic targets of PBIT. Presto Blue assays were next performed to determine the extent to which PBIT alters cell proliferation. Micromolar concentrations of PBIT significantly reduced prostate cancer cell proliferation in a time- and concentration-dependent manner. Data from Cell Death ELISAs suggest that PBIT at a concentration of 10 μM did not significantly induce apoptosis within C4-2B or PC3 cells. However, PBIT does appear to induce cellular senescence within the PC3 cell line. The level of senescence associated beta-galactosidase staining was increased in PC3 cells following treatment with 10 μM PBIT. Furthermore, PBIT increased protein levels of a second senescence marker, lamin B1. Together, these data suggest that the induction of senescence contributes to the anti-proliferative effect of PBIT.

Citation Format: Tunde M. Smith, Zhenbang Chen, LaMonica V. Stewart. The KDM5 inhibitor PBIT reduces proliferation of castration-resistant prostate cancers via the induction of senescence [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3266.