In the United States, lung cancer leads all other cancers in both incidence and mortality rate. Clearly, there is an urgent need to develop novel chemopreventive and therapeutic approaches for lung cancer. Toward this goal, we have investigated novel strategies targeting intracellular mechanisms that promote survival and suppress apoptosis of premalignant and malignant human bronchial epithelial (HBE) cells and lung cancer cells. One effective strategy is to use the deguelin, isolated from Mundulea sericea (Leguminosae), which targets Akt that plays a major role in cell survival, transformation, end apoptosis. This proposal is based on findings which have shown that: A) Akt is constitutively active in pramalignant and malignant HBE cells. B) Akt is also highly active in most NSCLC cell lines, probably owing to the activating mutations of ras, overexpression of the tyrosine kinase receptor EGFR family and one of its ligands, transforming growth factor alpha (TGF-alpha), elevated levels of the subunits of PI3K, and reduced level of PTEN expression. C) Activation of Akt is an early biochemical effect of tobacco components; increased expression of pAkt (Ser473) has been observed in reactive epithelium specimens (bronchial hyperplasia and squamous metaplasia), bronchial dysplasia, and NSCLC from current and formal smokers. D) Targeting the Akt pathway using pharmacological or genetic approaches efficiently inhibited Akt activity and suppressed the proliferation of premalignant and malignant HBE cells as well as NSCLC cells without detectable cytotoxicity on normal HBE cells. E) Deguelin strongly inhibited Akt activity, in association with suppression of the growth and induction of apoptosis in premalignant and malignant HBE cells as well as a subset of NSCLC cells, with minimum effects on normal HBE cells at in vitro dosages attainable in vivo. F) Deguelin also inhibited expression of COX-2, which is largely regulated by Akt, that participates in xenobiotic metabolism, angiogenesis, inhibition of immune surveillance, and suppression of apoptosis during tumorigenesis. G) Pharmacokinetic studies in rats and mouse showed that a nontoxic dose of deguelin (1 mu/M), delivered intravenously or by oral gavage, is achievable in a variety of tissues in vivo, including lung tissue. All of these findings provide a strong rationale to use deguelin as a chemopreventive and/or chemotherapeutic agent in lung cancer. We recently found that deguelin decreased the levels of a subset of client proteins of heat-shock protein 90, including PDK-1 and Akt, in NSCLC cells, suggesting that deguelin inactivated APt pmt|y by regulating the function of Hsp90. These and other studies have led to the following hypotheses: 1) Akt activation is sufficient for HBE cell transformation and is required for the survival of transformed HBE cells. 2) Inhibition of Akt activity prevents lung tumor development. 3) Deguelin inactivates Akt by decreasing stability of PDK-1 and Akt through blockade of Hsp90 in transformed HBE and NSCLC cells. In this RO1 application, I propose to test these hypotheses by exploring the following Specific Aims: 1) To determine whether constitutive activation of the Akt induces malignant transformation of HBE cells. 2) To determine whether inhibition of Akt activity by deguelin demonstrates lung cancer chemopreventive and/or therapeutic activity in mouse models of lung cancer. 3) To investigate the mechanism through which deguelin inactivates Akt in transformed HBE cells and NSCLC cells. We expect that evaluating the chemopreventive/chemotherapeutic activities of deguelin in animal model of lung cancer and understanding the mechanism by which deguelin regulates Akt activity may lead to the development of novel strategies for chemoprevention as well as treatment in lung cancer.
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