Cultured human tumor cells produce without stimulation by exogenous mitogens a variety of growth factors and cytokines. Individual factors can autostimulate tumor cell growth, but the same growth factors are also released into the microenvironment of tumors. Thus, they are likely to interact with normal tissue constituents such as fibroblasts, endothelial cells and keratinocytes and may have paracrine functions critical to the survival of tumor cells in vivo. This proposal focuses on the multifunctional role of basic fibroblast growth factor (bFGF) because this factor is uniquely expressed by melanoma cells, has potent angiogenic properties, is mitogenic for fibroblasts, and activates proteolytic enzymes that are implicated in melanoma invasion and metastasis. Two strategies will address the multifunctional role of bFGF. The first is to suppress synthesis in melanoma cells with antisense bFGF cDNA constructs. Melanoma cells unable to produce bFGF will be tested in monoculture for modulation of growth factor independence, activities of serine and metalloproteinase activities, and invasiveness through reconstructed basement membranes. Three- dimensional coculture systems resembling either epidermis or dermis of the normal human skin have been developed as models of cell-cell interactions in vitro to determine whether melanoma cells not synthesizing bFGF fail to stimulate keratinocyte and fibroblast proliferation or interactive extracellular matrix formation. Human skin grafted onto immunodeficient mice will be used as a model to study interactions of melanoma cells transfected with antisense bFGF cDNA constructs with normal skin cells under in vivo conditions and the focus will be on tumor vascularization, stroma formation, and invasion and metastasis. The second strategy is to induce bFGF synthesis in """"""""advanced"""""""" and normal melanocytes. bFGF-overexpressing melanocytes will be tested for growth factor independence and stimulation of fibroblasts and keratinocytes in the in vitro models and for their angiogenic and invasive properties in the in vivo model. These studies will contribute to a better understanding of the paracrine and autocrine roles of melanocytic cell-derived bFGF.
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