Extracellular matrix (ECM)-integrin signaling affects tumor growth, migration, invasion, and senescence. We developed a cell model of prostate carcinogenesis in which an androgen-dependent (AD) human prostate cancer cell line, LNCaP, was observed to progress to an androgen-independent (AI) state upon cellular interaction with either prostate or bone fibroblasts in vivo in castrated hosts. The resulting LNCaP sublines, C4, C4-2, and C4-2B, share lineage relationships with parental LNCaP, but with an altered downstream ECM-integrin signaling pathway. We analyzed cell attachment to ECM and assessed integrin isotypes and distribution by immunoprecipitation, western blotting, immunohistochemistry, and confocal microscopy. These analyses support the notion that prostate cancer cells, when progressing from the AD to the AI state, undergo functional integrin switching. The hypothesis of this proposal is that ECM-integrin interaction contributes to AI and metastatic progression of prostate cancer cells by altering critical downstream ECM- cell signal cascades. Understanding the molecular events of this important switch will facilitate our ability to develop novel therapeutic approaches to interfere with prostate cancer development and its distant dissemination. Two areas of research are emphasized. First, we propose to investigate the biology of integrin switching during prostate cancer progression. The adhesion of LNCaP and its lineage-derived sublines to osteopontin (OPN) and vitronectin (VN) will be determined and the roles of alphavbeta3 integrin in this adhesion process will be investigated. The significance of alphavbeta3 integrin acquisition during prostate cancer progression and its possible role in prostate cancer cell proliferation, migration and invasion in vitro and the functions of the alphavbeta3 integrin in prostate cancer metastasis and tumor angiogenesis in vivo will be evaluated. A strategy is proposed to investigate the therapeutic intervention of alphavbeta3 integrin and vascular endothelial growth factor receptor-mediated pathways, either singularly or in combination with a novel anti- angiogenic steroid, squalamine, extracted and purified from shark stomach. Second, the key intracellular signaling pathways that mediate the mitogenic, migratory, and invasive behaviors of prostate cancer cells in response to ECM will be assessed. The possible roles of OPN- and VN-mediated integrin signaling in prostate cancer cells, particularly the cell adhesion kinase-beta (PYK2) signaling pathway, will be evaluated, manipulated by genetic approaches, compared with focal adhesion kinase, and correlated with the biology of the prostate cancer cells.
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