Accumulating evidence suggests a link between adenosine monophosphate-activated protein kinase (AMPK), a well known regulator of energy homeostasis and insulin sensitivity, and cancer cell growth and survival through the regulation of mTOR signaling pathways, the suppression of inflammatory cytokines, especially interleukin (IL)-6, the stimulation of Akt dephosphorylation through protein phosphatase (PP)2A activation, and modulation of the expression of multiple oncogenes and tumor suppressors. Our screening of an in-house, thiazolidinedione-based focused compound library identified a lead agent, Cpd 53, that despite lacking PPAR agonist activity, activates AMPK and inhibits LPS-induced IL-6 secretion in THP-1 macrophages with low microM potency, and inhibits the proliferation of human breast cancer cells with IC50 of 1 - 2 microM by modulating the functional/expression status of various biomarkers related to AMPK, mTOR-p70S6K signaling, Akt, and IL-6 production. We hypothesize that Cpd 53 can be structurally optimized to generate novel AMPK activators with sub-microM potency that can block mammary tumorigenesis at clinically feasible concentrations and in the absence of dose-limiting toxicities. The following Specific Aims will be carried out to test our hypothesis. Specific Aim 1. To continue the structural modification of Cpd 53 and to conduct mechanistic validation of optimal agents. Cpd 53 will undergo further modifications via combinatorial synthesis with the goal of generating derivatives with sub-5M potency and cancer cell selectivity in different breast cancer cell lines vis-`- vis normal breast epithelial cells. The optimal candidate(s) will be subjected to mechanistic characterizations of signaling targets pertinent to AMPK activation. Specific Aim 2. To assess the in vivo efficacy of two optimized AMPK activators in MCF-7 and MDA-MB-231 xenograft tumor models. We hypothesize that targeting AMPK activation with a small-molecule agent constitutes a potentially successful strategy to suppress breast tumor growth irrespective of the functional status of ER and/or other genetic abnormalities. Two structurally optimized and mechanistically validated derivatives will be tested for in vivo efficacy in comparison to Cpd 53 and metformin. Maximum tolerated doses for each agent will be determined, followed by evaluation of tumor suppressive activity, intratumoral biomarker modulation, and toxicity. Specific Aim 3. To assess the in vivo efficacy of the optimal AMPK activator to block mammary tumorigenesis in a carcinogen-induced mammary tumor model. We hypothesize that the most active AMPK activator identified in Aim 2 will block mammary tumorigenesis in vivo at clinically attainable concentrations and in the absence of limiting toxicity. The safety of chronic oral treatment with this agent will also be examined in carcinogen-untreated animals. As AMPK represents a therapeutically relevant target for the treatment of the metabolic syndrome and cancer, there is a growing interest in the development of novel pharmacological activators for this fuel-sensing enzyme. Cpd 53's ability to target tumor metabolism, and survival signaling via AMPK activation and modulation of mTOR signaling is of high translational value to develop an effective chemopreventive strategy for breast cancer.