The purpose of this project is to study the role of TGF-beta in normal prostatic growth, prostatic carcinogenesis, and chemoprevention of prostatic cancer. In spite of the recognized importance of the chemoprevention of cancer, progress in this area of prostate research has been greatly hampered by inadequate experimental animal models and cell lines. To develop a suitable in vitro model for studying chemoprevention of prostate cancer, we have developed several non-tumorigenic (NRP-152) and tumorigenic (NRP-154 and DP-153) cell lines from the dorsal-lateral prostate of carcinogen-treated Lobund-Wistar rats, the only rodent that spontaneously develops prostatic carcinomas with any significant incidence. The NRP-152 cell line, which has been characterized extensively, is highly responsive to androgens, other steroid hormones, and many growth factors in vitro, and has the unique property of organizing into prostatic organoids in the presence of urogential sinus mesenchyme in vivo. Furthermore, we have shown that NRP-152 cells have stem-like properties, since they transdifferentiate from a basal toward a luminal epithelial cell phenotype in culture. Such differentiation is tightly coupled to the expression of TGF-betas and their receptors, suggesting that TGF-beta may play some critical role linked to this differentiation process. Indeed, we have shown that TGF-betas can not only arrest growth of NRP-152 cells in culture, they also induce apoptosis and promote differentiation of these cells, albiet under different conditions. We believe that TGF-beta functions as a key mediator of agents with cancer chemopreventive activity through its ability to relay cellular decisions of whether cells should growth arrest, differentiate, or apoptosis. Consistent with our model, retinoids and tamoxifen, which prevents the formation of prostatic tumors induced by N-methyl-nitrosourea (NMU) and testosterone propionate (TP) in Lobund- Wistar rat, induce the expression of TGF-betas by NRP-152 cells. Moreover, autocrine production of TGF-betas induced by retinoic acid or the antiandrogen hydroxyflutamide can mediate most of the growth inhibitory effects of these agents on NRP-152 cells in culture. We are presently testing our model in vivo by studying the formation of prostatic organoids from wild-type NRP-152 cells or genetically modified NRP-152 cells made defective in TGF-beta signaling or TGF-beta expression. Thus, the NRP-152 cell line is an important tool for mechanistic studies of carcinogenesis and chemoprevention is this tissue.
