Effect of NVP-BEZ235, a dual PI3K/mTOR inhibitor, on chemotherapy and antiangiogenic response in pancreatic cancer.

Abstract

243 Background: The phosphatidylinositol-3-kinase (PI3K)/AKT and mammalian target of rapamycin (mTOR) signaling pathway dysregulation is a prominent feature of pancreatic ductal adenocarcinoma (PDAC). Gemcitabine (GEM), a standard systemic treatment for PDAC, has limited clinical benefits. The present study investigated the effects of NVP-BEZ235 (BEZ235), a novel dual PI3K/mTOR inhibitor, in combination with gemcitabine and endothelial monocyte activating polypeptide II (EMAP) in experimental PDAC. Methods: Protein expression and cell proliferation were analyzed by Western blotting and WST-1 assay. Animal experiments were performed in murine xenografts. Results: BEZ235 inhibited phospho-AKT (Ser473) and phospho-mTOR (Ser2448) expression in PDAC (AsPC-1), endothelial (HUVECs) and fibroblast (WI-38) cells. NVP-BEZ235 also caused a significant dephosphorylation of downstream mTORC1 target proteins phospho-p70 S6K (Thr389) and phospho-4E-BP1 (Thr37/46). In vitro 72-hour proliferation of four PDAC cell lines was significantly inhibited by BEZ235. Additive effects on proliferation inhibition were observed in the BEZ235 and GEM combination in PDAC cells and in combination of BEZ235 or EMAP with gemcitabine in HUVECs and WI-38 cells. BEZ235, alone or in combination with GEM and EMAP, induced apoptosis in AsPC-1, HUVECs and WI-38 cells as observed by increased expression of cleaved poly (ADP-ribose) polymerase-1 (PARP-1) and caspase-3 proteins. PDAC in vivo therapy demonstrated that compared to controls (median survival: 16 days), animal survival increased after BEZ235 and EMAP therapy alone (both 21 days) and GEM monotherapy (28 days). Further increases in survival occurred in combination therapy groups BEZ235+GEM (30 days, p=0.007), BEZ235+EMAP (27 days, p=0.02), GEM+EMAP (31 days, p=0.001) and BEZ235+GEM +EMAP (33 days, p=0.004). Conclusions: BEZ235 has experimental PDAC antitumor activity in vitro and in vivo that can be enhanced in combination with cytotoxic (GEM) and antiendothelial (EMAP) agents. These findings demonstrate advantages of combination therapy strategies targeting multiple pathways in pancreatic cancer treatment.