Androgen receptor and MYC equilibration centralizes on developmental super-enhancer

Area of Science:

• Oncology
• Molecular Biology
• Genetics

Background:

• Androgen receptor (AR) signaling drives prostate cancer (PCa) progression.
• AR can repress gene transcription, including MYC, and supraphysiological androgen therapy shows efficacy in some PCa patients.
• The precise mechanisms of AR-mediated repression and its interplay with MYC in PCa remain incompletely understood.

Purpose of the Study:

• To elucidate the mechanism by which AR represses MYC transcription in prostate cancer.
• To investigate the reciprocal regulation between AR and MYC.
• To understand the role of this AR-MYC interaction in the development of castration-resistant prostate cancer (CRPC).

Main Methods:

• Chromatin conformation capture (3C) methods were employed to analyze interactions between the MYC promoter and its super-enhancer.
• In vitro and in vivo models were used to assess MYC expression changes upon androgen deprivation and MYC overexpression.
• Analysis of AR and MYC binding sites and histone modifications (H3K27 acetylation) was performed.

Main Results:

• AR-mediated repression of MYC is independent of direct AR chromatin binding and involves coactivator redistribution.
• AR disrupts the interaction between the MYC super-enhancer (within PCAT1) and the MYC promoter.
• Androgen deprivation increases MYC expression, while MYC overexpression suppresses global AR activity.
• Shared AR/MYC binding sites are enriched for active enhancers (H3K27 acetylation).

Conclusions:

• An intricate regulatory balance exists between AR and MYC in prostate cancer.
• Increased MYC expression during androgen deprivation contributes to castration-resistant PCa.
• Decreased MYC levels may predict response to supraphysiological androgen therapy.