Mammalian target of rapamycin (mTOR) is a critical regulator of cell growth and proliferation, serving as the central integration point for multiple homeostatic inputs, including growth factor availability, energy levels and amino-acid sufficiency. Constitutive, unregulated mTOR kinase activity is a nearly universal feature of cancer cells, and defects in the mTOR signaling network have also been implicated in metabolic disorders and benign tumor syndromes. For these reasons there has been intense interest in the clinical application of derivatives of the natural product rapamycin which inhibits some aspects of mTOR-mediated signal transduction. While rapamycin has shown promise as an anti-cancer agent in clinical trials, the potential contribution of rapamycin-insensitive aspects of mTOR signaling to cancer progression, including the recently identified feedback loop involving the direct activation of Akt by mTOR, points to the critical need for additional therapeutic avenues in the treatment of diseases associated with deregulation of the mTOR signaling network. In order facilitate the identification of additional small molecules targeting mTOR, we will develop a high throughput, cell-based assay for the quantitative detection of rpS6 phosphorylation as a measure of the activation state of the mTOR pathway. Using this assay, we will perform a series of pilot studies, starting with known inhibitors of mTOR signaling, such as rapamycin and wortmannin, and culminating in pilot screens of a library comprising 200 commercially available kinase inhibitors, as well as a larger library of chemically diverse bioactive compounds. In addition, we will develop a series of secondary assays, combining high content imaging, biochemical assays, and cell based functional readouts, to evaluate targets identified in our high throughput assay for their ability to modulate mTOR signaling. Particular emphasis will be placed on identifying compounds that are able to act as 'broad spectrum' mTOR inhibitors that block the activity of both mTORC1 and mTORC2. Specific inhibitors identified through this work will not only serve as valuable research tools but may advance the treatment of diseases involving hyperactive mTOR signaling. In many cancers, the defective regulation of a key protein in the cell known as mTOR directly contributes to the uncontrolled growth of malignant cells. Rapamycin is a drug that blocks some, but not all, cellular functions of mTOR and has shown some promise in cancer treatment, but it is not always effective. Our work is aimed at finding new drugs to specifically inhibit all aspects of mTOR activity, with the goal of improving treatments for cancers involving mis-regulation of mTOR signaling. ? ?
| Lipinski, Marta M; Hoffman, Greg; Ng, Aylwin et al. (2010) A genome-wide siRNA screen reveals multiple mTORC1 independent signaling pathways regulating autophagy under normal nutritional conditions. Dev Cell 18:1041-52 |
