Targeting epigenetic and post-transcriptional gene regulation by PSF impairs hormone therapy-refractory cancer growth.

RNA-binding protein PSF functions as an epigenetic modifier by interacting with long non-coding RNAs and the co-repressor complex. PSF also promotes RNA splicing events to enhance oncogenic signals. In this study, we conducted an in vitro chemical array screen and identified multiple small molecules that interact with PSF. Several molecules inhibited RNA binding by PSF and decreased prostate cancer cell viability. Among these molecules and its derivatives was a promising molecule, No.10-3 (7,8-dihydroxy-4-(4-methoxyphenyl)chromen-2-one), that was the most effective at blocking PSF RNA binding ability and suppressing treatment-resistant prostate and breast cancer cell proliferation. Exposure to No. 10-3 inhibited PSF target gene expression at the mRNA level. Treatment with No. 10-3 reversed epigenetically repressed PSF downstream targets, such as cell cycle inhibitors, at the transcriptional level. Chromatin immunoprecipitation-sequencing (ChIP-seq) in prostate cancer cells revealed that No. 10-3 enhances histone acetylation to induce expression of apoptosis as well as cell cycle inhibitors. Furthermore, No. 10-3 exhibited anti-tumor efficacy in a hormone therapy-resistant prostate cancer xenograft mouse model, suppressing treatment-resistant tumor growth. Taken together, this study highlights the feasibility of targeting PSF-mediated epigenetic and RNA splicing activities for the treatment of aggressive cancers.