Companion Diagnostics and Cancer Biomarkers Activation of AR Sensitizes Breast Carcinomas to NVP-BEZ235's Therapeutic Effect Mediated by PTEN and KLLN Upregulation

NVP-BEZ235 is a newly developed dual PI3K/mTOR inhibitor, being tested in multiple clinical trials, including breast cancer. NVP-BEZ235 selectively induces cell growth inhibition in a subset, but not all, breast cancer cell lines. However, it remains a challenge to distinguish between sensitive and resistant tumors, particularly in the pretreatment setting. Here, we used ten breast cancer cell lines to compare NVP-BEZ235 sensitivity and in the context of androgen receptor (AR) activation during NVP-BEZ235 treatment. We also used female SCID mice bearing breast tumor xenografts to investigate the beneficial effect of dihydrotestosterone/NVP-BEZ235 combination treatment compared with each alone. We found that AR-positive breast cancer cell lines aremuchmore sensitive toNVP-BEZ235 comparedwithAR-negative cells, regardless of PTEN or PI3KCA status. ReintroducingAR expression inNVP-BEZ235 nonresponsiveAR-negative cells restored the response.DHT/NVP-BEZ235 combination not only resulted in amore significant growth inhibition than either drug alone, but also achieved tumor regression and complete responses for ARþ/ERþ tumors. This beneficial effect was mediated by dihydrotestosterone (DHT)-induced PTEN and KLLN expression. Furthermore, DHT could also reverse NVP-BEZ235–induced side effects such as skin rash and weight loss. Our data suggest that AR expressionmay be an independent predictive biomarker for response toNVP-BEZ235. AR induction could add benefit during NVP-BEZ235 treatment in patients, especially with ARþ/ERþ breast carcinomas. Mol Cancer Ther; 13(2); 517–27. 2013 AACR.