The understanding of the mechanisms of normal and abnormal prostate growth is fundamental to the development of novel rational therapeutic approaches for the treatment of the two major diseases of the prostate: benign prostatic hyperplasia (BPH) and cancer. Among the molecular mechanisms that regulate normal cell proliferation, the interaction between cells and extracellular matrix, mediated by the Integrin family of cell adhesion receptors, plays a dominant role in signaling and gene induction in differentiation and proliferation. Previous work from the applicant's laboratory has led to the identification of a novel alternatively spliced form of the ubiquitous B1A integrin, designated, B1C. At variance with signals transduced by the main form B1A, which potentiates cell proliferation, expression of B1C inhibits cell growth. Accordingly, B1C expression is down-regulated in prostate glands which exhibit regenerative features and in prostate cancer. Therefore, a role for B1C, B1A integrins and their ligands in the regulation of normal and aberrant prostate cell growth is hypothesized and will constitute the focus of the present application. In the first specific aim, the relative expression of B1A, B1C and their ligands (fibronectin, laminin and collagen), will be investigated in normal and hyperplastic prostate tissues by immunohistochemistry. Tissues collected for the NIDDK-NIH-sponsored BPH-Trial or tissue samples displaying morphologic features of hyperplasia will be used. When feasible, selected larger specimens will be processed for immunoblotting and RNA analysis. In the second aim, the relationship between B1A and B1C expression and proliferation of epithelial prostate cells will be investigated. This will be done by transiently transfecting the various integrin subunits in normal prostate cells and by testing their proliferative potential by BrdU or 3H-thymidine incorporation. In the third aim, it is hypothesized that integrin functions in prostate cell growth may be modulated by released soluble mediators. The effect of transforming growth factor (TGF)B1, known to be released by prostate stromal cells, on B1A and B1C integrin expression and cell adhesion properties of normal prostate cells will be analyzed. The study will be performed by immunofluorescence, immuno-precipitation and cell adhesion assays. The proposed studies will provide new insights into the potential patho-physiological role of integrins and matrix proteins in prostate cell growth and may help to elucidate new ways to limit or prevent, in BPH, aberrant cell growth in vivo.
