Androgen receptor-dependent enhancers in prostate cancer

Prostate cancer is one of the leading causes of cancer-related death in European men. In almost all patients, Androgen Receptor (AR)-mediated transcription is critical for the development and proliferation of cancer. Upon activation, the AR binds to DNA and induces the expression of genes essential for cellular differentiation and tumor growth. AR-mediated transcription is driven by distal regulatory enhancer elements that control gene expression by looping to gene promoters. However, there are exponentially more AR binding sites than differentially expressed genes. It is unknown how these regions work to induce transcription. Delineating the regulatory logic of AR-mediated transcription is critical to understanding how this transcription factor drives prostate cancer growth and progression. To identify these specific AR enhancers, we functionally tested all clinical AR binding sites with a massively multi-parallel enhancer assay to create the first "map" of AR transcriptional activity. From this, we found that only a subset of ARBS had functional enhancer activity AR. Those AR-regulated enhancers act as a regulatory hub that frequently cooperates with other ARBS to drive transcription. Yet intriguingly, we observed that many of the minimal enhancer activity sites are often required for gene transcription, suggesting that ARBS have different functions that are independent of only enhancer activity. To explore this, we systematically characterized the KLK gene locus and found that AR occupancy is dependent on other AR binding sites in the same transcriptional network. Overall, this work provides fundamental insights into AR functions to drive gene activation.