A transgenic model for prostate cancer would be useful for developing new therapies for human prostate cancer (HPC), testing hypotheses about the role of oncogenes in HPC, and developing an understanding of the molecular basis of HPC. We plan to develop such a model by using a promoter known to target genes to the prostate [a truncated MMTV promoter (tMMTV)] to drive an H-ras oncogene (rasT24 - codon 12 mutation) and a mutant mouse p53 gene (codon 172 mutation). We will study the expression of these trans-oncogenes in the dorsal, lateral and ventral prostate and in the coagulating gland (anterior prostate) and correlate expression with the development of hyperplasia, neoplasia and malignant change as assessed by histopathology. Autopsies are planned to evaluate the effects of expression of the trans-oncogenes in other organs, as well as invasion and metastasis. rasT24 oncogene and mutant p53 genes cooperate in cell culture to bring about transformation; we will investigate cooperation in vivo by breeding mice carrying tMMTV rasT24 with mice carrying tMMTV p53 (mut 172). As promoters become available which target genes in a temporal and spacial specific way (probasin, SVSII, and prostatic specific antigen; Dr. Greenberg's project), we will investigate the timing and order of oncogene expression in malignant transformation. Based on findings on p53 mutations in human prostate cancer (Dr. Lebovitz's project), we will target these to the mouse prostate to study the molecular basis for their effects. The molecular basis for tumor formation and progression will be studied by evaluating: 1) endogenous H-ras and p53 genes, as well as trans-oncogenes, for mutation, deletion, rearrangement and amplification; 2) changes in expression of endogenous oncogenes, growth factors and their receptors (e.g., TGF-alpha/EGF, FGF/int-2, the TGF-beta family, IGF-I and IGF-II); and 3) changes in DNA content as measured by flow cytometry and image analysis. We will use tumor formation in nude mice to analyze the biological potential of lesions and study details of how trans-oncogenes regulate endogenous oncogenes and growth factors and bring about transformation by culturing cells from these lesions and comparing them to cultures of normal prostatic epithelial cells. Culturing will be facilitated by making mice carrying a tMMTV neomycin resistance gene and growing the cells in G418. The addition of other oncogenes or growth factors by electroporation will allow us to develop in vitro models for progression.
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