232 THE CASTRATION-INDUCED OXIDATIVE STRESS MAKES PROSTATE CANCER CELLS CASTRATION RESISTANT THROUGH TWIST1 AND ANDROGEN RECEPTOR OVEREXPRESSION

Phorbol 12-myristate 13-acetate (PMA) induces cellular apoptosis in prostate cancer cells, the growth of which is governed by androgen/androgen receptor (AR) signaling, but the mechanism by which PMA exerts this effect remains unknown. Therefore, in this study, we investigated the mechanistic action of PMA in prostate cancer cells with regard to AR. We showed that PMA decreased E2F1 as well as AR expression in androgen-dependent prostate cancer LNCaP cells. Furthermore, PMA activated JNK and p53 signaling, resulting in the induction of cellular apoptosis. In LNCaP cells, androgen deprivation and a novel anti-androgen enzalutamide (MDV3100) augmented cellular apoptosis induced by PMA. Moreover, castration-resistant prostate cancer (CRPC) C4-2 cells were more sensitive to PMA compared with LNCaP cells and were sensitized to PMA by enzalutamide. Finally, the expression of PKC, E2F1, and AR was diminished in PMA-resistant cells, indicating that the gain of independence from PKC, E2F1, and AR functions leads to PMA resistance. In conclusion, PMA exerted its anti-cancer effects via the activation of pro-apoptotic JNK/p53 and inhibition of pro-proliferative E2F1/AR in prostate cancer cells including CRPC cells. The therapeutic effects of PMA were augmented by androgen deletion and enzalutamide in androgen-dependent prostate cancer cells, as well as by enzalutamide in castration-resistant cells. Taken together, PMA derivatives may be promising therapeutic agents for treating prostate cancer patients including CRPC patients.

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Splicing Factor Prp8 Interacts With NESAR and Regulates Androgen Receptor in Prostate Cancer Cells

Molecular Endocrinology ◽

10.1210/me.2015-1112 ◽

2015 ◽

Vol 29 (12) ◽

pp. 1731-1742 ◽

Cited By ~ 8

Author(s):

Dan Wang ◽

Minh M. Nguyen ◽

Khalid Z. Masoodi ◽

Prabhpreet Singh ◽

Yifeng Jing ◽

...

Keyword(s):

Prostate Cancer ◽

Androgen Receptor ◽

Cancer Cells ◽

Splicing Factor ◽

Luciferase Assay ◽

Nuclear Accumulation ◽

Physical Interaction ◽

Mrna Levels ◽

Prostate Cancer Cells ◽

Castration Resistant

Abstract Androgen receptor (AR) plays a pivotal role in the development of primary as well as advanced castration-resistant prostate cancer. Previous work in our lab identified a novel nuclear export signal (NES) (NESAR) in AR ligand-binding domain essential for AR nucleocytoplasmic trafficking. By characterizing the localization of green fluorescence protein (GFP)-tagged NESAR, we designed and executed a yeast mutagenesis screen and isolated 7 yeast mutants that failed to display the NESAR export function. One of those mutants was identified as the splicing factor pre-mRNA processing factor 8 (Prp8). We further showed that Prp8 could regulate NESAR function using short hairpin RNA knockdown of Prp8 coupled with a rapamycin export assay in mammalian cells and knockdown of Prp8 could induce nuclear accumulation of GFP-tagged AR in PC3 cells. Prp8 expression was decreased in castration-resistant LuCaP35 xenograft tumors as compared with androgen-sensitive xenografts. Laser capture microdissection and quantitative PCR showed Prp8 mRNA levels were decreased in human prostate cancer specimens with high Gleason scores. In prostate cancer cells, coimmunoprecipitation and deletion mutagenesis revealed a physical interaction between Prp8 and AR mainly mediated by NESAR. Luciferase assay with prostate specific antigen promoter-driven reporter demonstrated that Prp8 regulated AR transcription activity in prostate cancer cells. Interestingly, Prp8 knockdown also increased polyubiquitination of endogenous AR. This may be 1 possible mechanism by which it modulates AR activity. These results show that Prp8 is a novel AR cofactor that interacts with NESAR and regulates AR function in prostate cancer cells.

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