Advanced metastatic castration-resistant prostate cancer (CRPC) is an aggressive disease with high mortality rate, primarily resulting from the transcriptional addiction driven by Androgen Receptor (AR) signaling. The evolutionarily conserved multi-subunit Mediator complex plays a central role in the regulation of transcription by virtue of its ability to functionally bridge gene-specific transcription factors with the RNA polymerase II- associated basal transcription machinery. MED1 is a key component of the Mediator complex and is responsible for targeting and anchoring the complex to a broad range of nuclear receptors, including AR. We have identified phosphorylation of MED1 catalyzed by CDK7 transcriptional kinase is required for its interaction with AR and as a rate-limiting step in AR-mediated transcription. The underlying hypothesis of this proposal is that the CDK7 mediated phosphorylation of MED1 is necessary for the formation and stability of MED1-AR complex at the chromatin in both nave and anti-androgen refractory CRPC which could be targeted by CDK7 specific inhibitors. The goals of this grant application are to investigate the mechanistic basis of MED1-AR interaction further, and evaluate the CDK7 specific inhibitors in reversing the AR-dependent transcriptional addiction in advanced prostate cancer. The three specific aims of the projects are:
Specific Aim 1 : Investigate the role of p-MED1 in hyper-activation of AR-signaling Specific Aim 2: Investigate the mechanism of increased p-MED1 in enzalutamide refractory PCa.
Specific Aim 3 : Establish the efficacy of CDK7 inhibitor in clinically relevant nave and refractory CRPC models in vivo.
In this grant application, we propose to study the biological functions of transcription coactivator in advanced and treatment-refractory prostate cancer. As such, the studies proposed here will lead to the identification of novel signaling components that facilitate transcription addiction and will offer novel therapies in treating prostate cancer.