Targeting the USP1 dependent KDM4A protein stability as a potential prostate cancer therapy

Abstract Background: Prostate cancer is the most commonly diagnosed malignancy and second leading cause of cancer death in American men. The histone demethylase KDM4A is reported to be overexpressed and plays a vital in multiple cancers through controlling gene expression by epigenetic regulation of H3K9 or H3K36 methylation marks. The biological role and mechanism of KDM4A in regulating AR activity in prostate cancer, however, remain to be established. Methods: KDM4A expression in PTEN knockout mouse was determined using western blotting, Real-time PCR and immunohistochemical. Functional assays, such as cell survival, cell colony formation, anchorage-independent growth and a xenograft tumor model were used to determine the oncogenic role of KDM4A in prostate cancer cells. Association of KDM4A with USP1 and the deubiquitination assay were determined by co-immunoprecipitation, immunofluorescent staining and immunoblotting. USP1-KDM4A axis promotes AR-dependent c-Myc expression was further investigated using western blotting, chromatin immunoprecipitation and Real-time PCR. The specific USP1 inhibitor ML323 was used for assessing the role of USP1 in prostate cancer cell survival. Co-expression of KDM4A with USP1 was determined by immunohistochemical staining in 146 prostate cancer tissue samples. Results: Herein, we reported KDM4A expression was upregulation in PTEN knockout mouse prostate tissue. Depletion of KDM4A in prostate cancer cells inhibited their proliferation and survival in vivo and vitro. Further studies reveal that USP1 is a deubiquitinase that regulates KDM4A K48-linked deubiquitin and stability. Interestingly, we found c-Myc was a key downstream effector of USP1-KDM4A/AR axis in driving prostate cancer cell proliferation. Notably, upregulation of KDM4A expression with high USP1 expression were observed in 70% of prostate tumors and inhibition of USP1 promotes prostate cancer cells response to therapeutic agent_enzalutamide. Our studies propose USP1 may be an anti-cancer therapeutic target in prostate cancer. Conclusions: Our findings demonstrate that USP1 deubiquitinates and stabilizes KDM4A, which promotes recruitment of AR to the c-Myc gene enhancer and highlight USP1 potential as an anti-cancer therapeutic target in prostate cancer. Keywords: USP1; Prostate cancer; KDM4A; Deubiquitination; Tumorigenesis