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 cis-regulatory elements and trans-acting factors required for AR enhancer activity in a cell line model. In FY22, we used novel Cas9 base editors to perform a high resolution mutational analysis of the endogenous AR enhancer. We identified cis-elements at single nucleotide resolution that are required for AR transcription and cancer cell proliferation. For validation studies we developed a competition based assay using serial imaging and single molecule RNA FISH in collaboration with the LGCP microscopy core. We are currently investigating the mechanism of these deleterious mutations including assessing transcription factor binding, chromatin modifications, accessibility, and DNA looping.