Transforming growth factor-beta in benign and malignant prostate

BACKGROUND. The present review summarizes the cellular action of TGF-beta i n benign and malignant growth of the prostate. METHODS. TGF-beta is a pleiotropic growth factor. It plays an important rol e in the regulation of growth and differentiation in many cells. In benign prostatic epithelia, its action is mediated through a paracrine mechanism. It inhibits proliferation and induces apoptosis in prostatic epithelia. It provides a mechanism to maintain epithelial homeostasis in the prostate. In prostatic stroma, its continual action leads to smooth muscle differentiat ion. This effect of TGF-beta may regulate the development of prostatic smoo th muscle nodules in benign prostatic hyperplasia. RESULTS. As prostatic epithelial cells undergo malignant transformation, tw o major events occur regarding TGF-beta action. These include the loss of e xpression of functional TGF-beta receptors and overproduction of TGF-beta i n malignant cells. The loss of expression of functional TGF-beta receptors provides a growth advantage to cancer cells over their benign counterparts. The overproduction of TGF-beta by cancer cells has a multitude of adverse consequences. TGF-beta can promote extracellular matrix production, induce angiogenesis, and inhibit host immune function. The biological consequence of these activities is an enhanced tumorigenicity in prostate cancer. Resul ts of our recent studies with a rat prostate cancer model suggest that the immunosuppressive effect of TGF-beta seems to be the primary cause of tumor progression. This is because, if these cancer cells were engineered to red uce the production of TGF-beta, tumor growth was inhibited in syngeneic hos ts but not in immune compromised hosts. CONCLUSIONS. Our future research should take advantage of this knowledge to devise therapeutic strategies aimed at eradicating prostate cancer. (C) 19 99 Wiley-Liss, Inc.