The overall goal of this program project is to identify and evaluate novel natural product cancer chemopreventive agents. In the discovery process, activity-guided fractionation is employed, utilizing short-term bioassays as a monitor. The first goal of this core is to provide bioassay support of physiological relevance. As validated previously, the current test battery is comprised of assays designed to monitor inhibition of carcinogenesis at the stages of initiation (e.g., induction of quinone reductase activity in cell culture), promotion (e.g., inhibition of cyclooxygenase activity), and progression (e.g., induction of cell differentiation). Mechanistic-based high throughput assay systems have recently been devised, such as a fluorometric assay for inhibition of aromatase, and stably transfected HepG2 cells with reporter genes for ARE, ERE, PPAR, and NF-kappaB. Test materials and assay procedures actually used for specific fractionations are keyed on secondary discriminations also provided by this core. Once lead materials are structurally characterized, additional studies are performed in this core to more fully characterize the potential of the test agent to succeed in clinical intervention trials. With semi-preparative quantities of active leads (0.05-1 g), preliminary mechanistic evaluations will be performed. In addition to in vitro methodologies, this will involve short-term animal studies designed to assess effects on biomarkers of carcinogenesis (e.g., induction of phase II enzymes). In addition, with relatively small quantities of test materials, inhibition of tumorigenesis will be determined in the two-stage mouse skin model. Finally, based on the overall profile of structure, activity, natural abundance, etc., the most promising test materials will be evaluated for chemopreventive activity in full-term models of carcinogenesis with laboratory animals. The specific animal model and administration protocol will be based on the overall profile of the agent. The full-term tumorigenesis systems to be employed include the two-stage mouse skin model, the carcinogen (DMBA or NMU)-induced rat mammary model, the PIN (prostatic intraepithelial neoplasia) prostate model with male Noble rats, and the benzo(a)pyrene-induced lung tumor model in strain A mice. Complete data sets will be prepared and transmitted to organizations capable of promoting more advanced stages of development, such as the National Cancer Institute.
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