Despite in vivo studies that have reported some additive effect of me

Identifying additional molecular targets for inhibition in combination with mTORC1 blockade is critical if enhanced anti tumor effects are to result. Taking into account that PI3K/AKT protumorigenic signals are mediated through multiple downstream effectors and the recently identified feedback loops by which mTORC1 inhibition further activates PI3K/AKT provides Imatinib a sound rationale for the development of dual PI3K/mTOR inhibitors. A recent study from our laboratory has identified enhanced anti MPNST effects for one such inhibitor, PI103, when tested in vitro. However, to the best of our knowledge, pre clinical testing of such inhibitors in vivo, a critical step prior to the conduct of human clinical trials, has yet to be reported. Interestingly, our initial in vitro based studies using transmission electron microscopy image analyses and LC3 western blotting identified PI103 to induce the accumulation of autophagosomes in MPNST cells. Notably, this morphological Urogenital pelvic malignancy change might represent either enhanced autophagic flux or halted, blocked macroautophagy, multiple experiments are needed in order differentiate between these two potential consequences. Recent published data suggest that PI3K/ mTOR blockade potentially induce the former, i. e. enhanced productive autophagy, in preclinical models of lung and pancreatic cancer, whether this is the case in MPNST remains to be elucidated. Autophagy is a multi step catabolic process characterized by the appearance of cytoplasmic vacuoles, leading to eventual self digestion of cellular organelles and other constituents within autolysosomes. While initially described as a mechanism of cell pifithrin-? death, a large body of evidence supports a role for drug induced autophagy in tumor cell survival, thereby a potential mechanism of therapeutic resistance. These effects might be tumor type, compound, or even context dependent. Unraveling the role of autophagy in a particular therapeutic context is of significant clinical relevance. The goal of the current study was to bridge several knowledge gaps noted above and to: 1) assess the anti tumor effect of dual PI3K/mTOR blockade on the local and metastatic growth of MPNST xenografts, 2) determine whether PI3K/mTOR inhibition in enhanced productive autophagy or autophagy blockade in MPNST cells, and, 3) if the former is the case, to assess the role of drug induced autophagy in therapeutic response. XL765, a highly potent PI3K/mTOR inhibitor, was specifically selected for testing, this compound is now undergoing clinical evaluation in a broad range of other cancer types. Cell lines and reagents MPNST cell lines included the NF1 associated: S462, ST88 14, MPNST642 isolated in our laboratory, and the sporadic MPNST cell lines STS26T and MPNST724, these were propagated and maintained as previously described. We acquired these cell lines between 2008 2011, all were authenticated using DNA fingerprinting as previously described, confirming that no cross contamination has occurred.