Mechanism of epigenetic activation during disease progression

Division Of Basic Sciences - Nci

Investigators

Abstract

In previous work, we showed that activation of an enhancer of AR occurs in response in response to androgen-targeted therapies and contributes to castration-resistance by increasing AR expression. Since that discovery, multiple laboratories have confirmed that the AR enhancer is frequently amplified in castration-resistant prostate cancers and associated with resistance to anti-androgen therapy. However, the mechanism of how the enhancer is activated during the transition from primary prostate cancer, where it is almost never active, to castration-resistant disease, where it is active in 80-90% of cancers, is unknown. To elucidate the mechanism of enhancer activation we are taking a functional genomics approach to identify trans-acting factors that bind to and activate the AR enhancer in a cell line model. Leveraging our experience with epigenome editing, we performed a pooled CRISPR-based screen to identify transcription factors (TFs) that bind to the AR enhancer and activate transcription. We identified TFs that decrease AR expression when knocked out and bind to the AR enhancer by ChIP. We subsequently validated these factors across different prostate cancer cell lines. In parallel we adapted novel Cas9 base editors to generate deleterious point mutations within the endogenous AR enhancer to identify cis-acting elements at the nucleotide level.