The goals of this project are to identify and characterize growth factors and growth factor receptors active on epithelial and mesenchymal cells of the normal prostate, as well as on epithelial tumor/stromal elements of primary and metastatic prostate carcinomas, and to determine those mechanisms that produce a selective advantage for the seeding of bone metastases in prostate cancer patients. This proposal is based on the premise that normal prostatic epithelial and mesenchymal cells maintain active intercellular signals required for the development and differentiation of this organ. It is our hypothesis that analogous interactions between metastatic epithelial prostate cells and stromal elements in normal bone are present and mimic those of normal prostate, recreating a perfect environment for tumor seeding and growth. This hypothesis is supported by the fact that osseous metastases are identified in up to 80% of patients dying of prostate cancers, being symptomatic in the majority of cases, and their clinical complications usually dictating the final outcome of the disease. The main objective is to translate basic research findings to the clinical setting, concerning mechanisms of tumor progression.
The specific aims are:
Aim #1 : To determine the modes of action of developmental and clinically relevant tyrosine kinases in human prostatic tissue. We will analyze the phenotype of growth factor receptors and their corresponding growth factor ligands on epithelial/mesenchymal cells of the normal prostate, as well as on tumor/stromal elements of primary and metastatic prostate carcinomas. We will assess the sensitivity and specificity of a panel of well characterized antibodies and molecular probes to specific growth factor receptors and their corresponding growth factor ligands, including EGFr, TGFalpha, EGF, FGFr, aFGF, bFGF, c-kit, SCF, trk receptors and neurotrophins. We will use immunohistochemistry and in situ hybridization on consecutive tissue sections. We plan to complement cellular localization by immunoblotting and northern blot assays, using tissue from the same block. Morphologic evaluation will be assessed in all cases.
Aim #2 : To characterize the differentially expressed and activated growth factor receptors expressed by prostatic tumor/stromal elements of primary versus different metastatic sites (i.e., lymph node versus bone lesions). We will perform high resolution two-dimensional electrophoresis followed by immunoblotting and microsequencing techniques. These studies will be done in collaboration with Dr. Paul Tempst (Microchemistry Laboratory).
Aim #3 : To investigate the mechanisms implicated in signal transduction mediated by binding of growth factors to their putative receptors by means of in vitro model systems. We will also analyze co-cultures of prostate cancer cells with fibroblasts from different sources, including bone. Attempts will be made to investigate the action of transfected NIH 3T3 cells with appropriate constructs of specific growth factors on prostate carcinoma cells. Blocking assays based on monoclonal antibodies to specific growth factor receptors will also be conducted and may serve as the basis for future preclinical studies.
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