The long-term objective of our multidisciplinary research is to understand the role that sex hormones may play in the initiation of proliferative preneoplastic prostatic lesions in humans and their progression to malignancy. For these purposes we have developed a rat model in which we can consistently induce dysplastic lesions in the dorsolateral (DLP) prostate by the chronic simultaneous administration of testosterone (T) and estradiol-17beta (E2). The dysplastic lesions closely approximate those commonly found in the human prostate and, like their counterpart, frequently develop into invasive neoplasms. Our current research program is focused on investigating endocrinological and molecular mechanisms that we believe are implicated in the pathogenesis of the early aberrant proliferative lesions. Specifically, we propose to investigate whether the androgen-supported estrogen treatment increases in nuclear type II estrogen receptor (ER) levels in the DLP initiates and sustains a cascade of events responsible for dysplastic development. The proposed receptor- mediated events include this enhanced expression of the TGF-alpha/EGF and EGF receptor autocrine loop and an increase in the levels of guanosine triphosphate (GTP) bound to p21(ras). To test this hypothesis we will first confirm and extend our preliminary data which indicates that there is enhancement of this autocrine loop and ras transcript expression in DLPs harboring dysplastic lesions. For these purposes we will use Northern and Western blots, binding assays and immunoassays for assessing the functional levels of components of the autocrine loop, and measurements of GTP/GDP binding to p21(ras). To determine whether the enhancement of all or some, the pathway components are directly mediated by increases in type II nuclear ER we will administer specific competitive inhibitors of the receptor binding to rats simultaneously treated with T+E2. Since our collaborative research has recently shown that T+E2 treatment causes DNA adduct formation exclusively in the DLP, we will also determine whether point mutations occur in the GTpase regions of ras genes that could be responsible for increases we may find in GTP binding to p21(ras). For these purposes we will use single-strand conformation polymorphism to screen tissues and direct nucleotide sequencing to positively identify the mutation. Our studies will employ a multidisciplinary approach which includes pathology, endocrinology and molecular biology. Data from this project are expected to yield important information concerning the role sex steroids play in the pathogenesis of atypical proliferative pre-cancerous lesions in the prostate. An understanding of the mechanisms involved in the genesis of these lesions in our animal model should prove valuable in deciphering the causes of prostate dysplasia in humans.
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