Although nearly all prostate cancer initially are androgen responsive, maximum androgen blockade using combined antiandrogen and GnRH agonist treatment only moderately increases progression-free survival or median survival. These clinical and experimental findings suggest that other growth promoters modulate prostate cancer cell proliferation. Our immunologic, genetic, and biochemical studies show that (a) rat prostate cancer cells and their conditioned media contain large quantities of FGF-like (fibroblast growth factor-like) mitogens, (b) bFGF-like (basic FGF-like) mitogen production is cell line specific, and (c) rat prostate cancer cells contain FGF receptors; however, functional status apparently differs among cell lines. These findings support our hypothesis that FGFs are important effectors of prostate cancer cell proliferation. We will address issues of FGF regulation of prostate cancer cell function by studies using androgen and exogenous FGF responsive T5 and androgen and exogenous FGF unresponsive C3 clonally derived rat prostate cancer cells.
Our specific aims are: (1)We will test the hypotheses that prostate cancer cell associated mitogens are precursors of conditioned medium FGF-like mitogens and that truncated FGF receptor-like polypeptides serve as carriers for extracellular FGF transport. (2) We will use plasmid pKK233-2 to construct vectors for generation of rat bFGF and aFGF (acidic FGF) in E coli. Homogenous FGFs will be used as assay standards, as mitogens during in vitro studies of FGF modulation of prostate cancer cell proliferation, and used to produce polyclonal bFGF and aFGF antibodies in rabbits. Antibodies will be used for quantification of cancer cell bFGF-like and aFGF-like mitogens, for mitogen identification during purification, and for immunocytochemical localization of FGFs in prostate cancer cells. (3)We will define how prostate cancer cell bFGF-like mitogens are related to prototypic bFGF and examine potential cause for cell line specific expression of a novel 23/24 kDa bFGF-like mitogen. (4) We will define FGF modulation of prostate cancer cell proliferation by employing FGF immunoneutralization and by constructing regulable antisense rat bFGF and aFGF expression vectors. Stably transformed cells will be used for in vitro assessments of FGF modulation of prostate cancer cell proliferation. (5) We will define the functional status of C3 cell FGF receptors (these cells are unresponsive to exogenous FGFs) and test the hypothesis that demonstrated TGF-Beta1 modulation of T5 cell responsiveness to exogenous FGFs is achieved by altering FGF receptor signal transduction. (6) We will determine whether mitogens other that FGFs, known to be expressed in normal and other neoplastic prostate tissue, and expressed in C3 and T5 prostate cancer cells. These studies will provide new, basic information detailing: (a) prostate cancer cell FGF synthesis and secretion, (b) the role of FGF-like mitogens as affecters of prostate cancer cell function, and (c) mechanisms of FGF signal transduction in prostate cancer.
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