Activation of AR sensitizes breast carcinomas to NVP-BEZ235's therapeutic effect mediated by PTEN and KLLN upregulation

Abstract

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 are muchmore sensitive to NVP-BEZ235 compared with AR-negative cells, regardless ofPTEN or PI3KCA status. Reintroducing ARexpression in NVP-BEZ235 nonresponsive AR-negative cells restored the response. DHT/NVP-BEZ235 combination not only resulted in a more significant growth inhibition than either drug alone, but also achieved tumor regression and complete responses for AR + /ER + 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 ARexpression may be an independent predictive biomarker for response to NVP-BEZ235. AR induction could add benefit during NVP-BEZ235 treatment in patients, especially with AR + /ER + breast carcinomas. Mol Cancer Ther; 13(2); 517-27. © 2013 American Association for Cancer Research.