Small‐Molecule Inhibition of the Androgen Receptor (AR)‐RUNX2 Interaction in Prostate Cancer (PC)

Abstract

The advent of prostate carcinogenesis is associated with alterations in AR transcriptional activity to promote cancerous phenotypes. In particular, the transcription factor RUNX2 has been shown to modulate AR activity in a locus‐dependent manner. The AR and RUNX2 interact to inhibit a majority of genes they co‐regulate, dubbed Type I, including the tumor‐suppressor NKX3.1. Interestingly, they cooperatively express a small set of genes in a synergistic manner (Type II) including the oncogenes, SNAI2 and SOX9. We devised a robust fluorescent cell‐based assay (z‐score >0.7) to screen for inhibitors of the oncogenic AR‐RUNX2 interaction in the C4‐2B PC cell line with doxycycline‐inducible RUNX2. These cells were transfected with a type II/YFP reporter and a control mCherry plasmid. The cells were treated with doxycycline to induce RUNX2 expression and DHT to activate AR then analyzed in a 96‐well plate format on a Tecan fluorescent plate reader. We identified two compounds from the NCI Developmental Therapeutics Program compound library that inhibited the AR‐RUNX2 interaction; which were validated by a dose curve in the same assay and qPCR for activity against synergistic activation of SNAI2 and SOX9. One compound was reported to inhibit the epidermal growth factor receptor (EGFR) so we sought to investigate the role of EGFR signaling in the AR‐RUNX2 interaction. Knockdown of EGFR changed the regulation of SNAI2 from that of a Type II gene to a canonical Type I gene, suggesting that EGFR signaling is necessary for the synergism. Moving forward, we aim to identify the component of EGFR signaling that facilitates Type II gene regulation as a potential therapeutic target in prostate cancer.