SIGNALING MECHANISMS IN REGULATION OF TUMOR ANGIOGENESIS

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DESCRIPTION (provided by applicant): Cancer is currently one of the most prevalent causes of death in the U.S.A. A major therapeutic option aims to slow the progression of cancer (example: use of anti-VEGF in colon cancer). Therefore, a renewed effort must be made to identify relevant molecular pathways, which could be exploited as therapeutic targets. Progression of many types of cancers is associated with up-regulation of several proangiogenic factors (HIF- 1a, VEGF, bFGF, PDGF, and MMP's etc.) which promotes tumor angiogenesis. These angiogenic factors activate different signaling pathways that regulate cell proliferation, migration and apoptosis. The long-term goals of my laboratory aims to understand the complex signaling mechanisms of angioinhibitors from extracellular matrix (type IV collagen NC1 domains, which are normally present in the blood), and to determine their role in antiangiogenic signaling. Recently my laboratory determined that a1(IV)NC1 mediates multiple signaling mechanisms to regulate tumor angiogenesis. However, its complex influences on tumor- angiogenesis and tumor growth are far from being fully understood. The present grant proposal is specifically directed at elucidating the mechanism whereby a1(IV)NC1 inhibits expression of the pro-angiogenic molecules, and its role in inhibition of tumor growth. In this study we aim to test our hypothesis: "a1(IV)NC1 promotes endothelial cell apoptosis through a1¿1 integrin and inhibits MMP-2 activation through an integrin independent pathway. These activities are critical for the antiangiogenic and antitumorogenic activity of a1(IV)NC1". Towards this end, we have generated an a1(IV)NC1 transgenic mouse model and adenoviruses, cloned and expressed a1(IV)NC1 in the baculovirus expression system and will use this protein for studies outlined in the specific aims. (1) Investigate the angioinhibitory signaling mechanisms by which a1(IV)NC1 inhibits the expression of angiogenic factors, including investigation of possible biochemical pathways. (2) Investigate the complex interactions between a1(IV)NC1/MMP-2 and identify the complementary binding sites involved in this interaction and function. (3) To investigate inhibition of tumor growth by a1(IV)NC1 in a1-integrin null and a1(IV)NC1 transgenic mice. The above Specific aims will be accomplished using cell cultures, a1 integrin null, a1(IV)NC1 transgenic mice and adenoviruses harboring a1(IV)NC1 domain expression cassettes. We will analyze these models using immunoblotting, co-immunoprecipitation, immunohistochemistry, Matrigel plug, and tumor studies. Successful completion of the proposed work will provide valuable insights that may facilitate the development of new antiangiogenic tumor therapies. PUBLIC HEALTH RELEVANCE: Cancer is currently one of the most prevalent causes of death in the USA, and current therapeutic options aim only to slow the progression of cancer. Therefore, a renewed effort must be made to identify nontoxic endogenous circulating anticancer molecules which could be exploited as therapeutic targets. My laboratory has cloned and expressed one such circulating molecule, and is presently testing it in a cell culture system and in live mice having tumors. The data being developed from these proposed studies have potential applications to cure solid tumor growth (cancers) in which angiogenesis contributes to the disease phase.