BH3-only protein BNIP3 in tumor progression

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DESCRIPTION (provided by applicant): BNIP3 is a BH3-only BCL-2 family mitochondrial protein. Overexpression of BNIP3 causes mitochondrial dysfunction and a slow necrosis-type of cell death. The expression of the Bnip3 gene is activated in hypoxic microenvironments and is a direct target for the transcription factor HIF-1. Expression of Bnip3 is associated with high-grade invasive tumors of the breast and lung. Our hypothesis suggests that chronic overexpression of Bnip3 in a hypoxic and acidic tumor microenvironment results in the evolution of aggressive tumor cells. We will test this hypothesis in the mouse xenotransplant model of human lung and mammary carcinoma cell lines. Our hypothesis also predicts that BNIP3-induced mitochondrial dysfunction activates the retrograde mitochondrial signaling pathway resulting in activation of expression of markers associated with tumor invasion and survival. We propose to determine the effects of BNIP3 expression on mitochondrial signaling molecules and effector nuclear transcription factors. The role of the mitochondrial signaling pathway in BNIP-3-induced tumor progression will be determined by the use of dominant negative inhibitors of the pathways. Our proposed project will provide support for a new concept that chronic overexpression of a death-promoting molecule in hypoxic solid tumors may lead to the evolution of tumor aggressiveness and progression. Our results may also provide the experimental support to suggest that BNIP3 may be a new prognostic marker for human cancer.