High‐throughput screen for inhibitors of androgen receptor‐RUNX2 interaction in prostate cancer (977.2)

Metastatic PC (mPC) is managed with AR‐targeted therapies; however, progression is inevitable. AR normally regulates prostate homeostasis but is compromised in PC to promote proliferation. RUNX2, a regulator of osteoblast differentiation, is expressed in many PCs and is associated with progression and metastasis. We found that RUNX2 modulates DNA‐binding and gene regulation by AR. Notably, AR/RUNX2 synergistically activates a subset of genes (type II) that includes the pro‐oncogenes Snai2 and Sox9. Thus, inhibition of AR/RUNX2 may provide a novel target for management of mPC. We devised a robust cell‐based assay (z‐score >0.7) for screening potential inhibitors of the AR/RUNX2 interaction in the C4‐2B PC cell line that expresses doxycycline (dox) inducible RUNX2. These cells were transfected with a type II/YFP reporter and a drug‐independent mCherry control plasmid. The cells were treated with dox to induce RUNX2 expression and DHT to activate AR then analyzed in a 96‐well plate format on a Tecan fluorescent plate reader. Each plate was assayed in duplicate with no drug, 0.25 mg/mL dox, 0.3 nM DHT, and dox+DHT controls. Using dox+DHT treated cells, we screened ~1800 compounds at 1 µM from the NCI Developmental Therapeutics Program library. Hits were identified with a custom algorithm, validated by performing a dose curve in the same assay, and then tested for activity against synergistic activation of endogenous genes by qPCR. Thus far, we have identified one inhibitor that is specific to the AR/RUNX2 synergism and are continuing to test validated hits in the qPCR assay. In the future, we will examine the AR‐RUNX2 inhibitors for efficacy against PC invasiveness in vitro and growth inhibition in PC xenograft mouse models.