Targeting the PI3K/AKT/mTOR pathway with MLN0128 (mTORC1/2 inh) and MLN1117 (PI3K alpha inh) in bladder cancer: Rational for its testing in clinical trials.

369 Background: PI3K/AKT/mTOR pathway is a promising target for cancer treatment being commonly deregulated in human bladder tumors and resulting in the promotion of tumor cell growth, survival, and resistance to chemotherapy. The aim of this study is to characterize the effects of MLN0128, a novel mammalian target of rapamycin (mTOR) complex 1 and 2 (mTORC1/2) dual inhibitor, and MLN1117, an orally bioavailable inhibitor of the class I phosphoinositide 3-kinase (PI3K) alpha isoform that may be more efficacious and less toxic than pan-PI3K inhibitors as bladder cancer therapies. Methods: We evaluated the effects of MLN0128 and MLN1117 both as single agents and in combination with each other or with a SOC chemotherapy agent (paclitaxel). The effects of the agents alone or in combination were analysed in a panel of six bladder cancer cell lines and in tumor xenografts. These models were selected based on specific genomic alterations that could be considered as potential therapeutic targets (PIK3CA and TSC mutations). Molecular effects of both agents and the combinations on cell-cycle, apoptosis, autophagy and on cell viability were tested in the bladder cancer cell lines. The in vivo effects on tumor growth inhibition were also assessed. Results: Both MLN0128 and MLN1117 inhibit the PI3K/AKT/mTOR pathway and reduce cell proliferation in bladder cancer cell lines with diverse genetic backgrounds. Combination of MLN0128 + MLN1117 produced synergistic antiproliferative effects in cell lines and improved the effect of each drug alone in vitro and in vivo, with no signs of toxicity in these models. Similar effects were observed with the combination of paclitaxel + MLN0128. Conclusions: Our results show that MLN0128 and MLN1117 are promising investigational agents that might be of value for bladder cancer patients. Further investigation as novel anti-cancer agents alone or in combination with chemotherapy in clinical trials in humans is warranted.