Effects of Black Raspberries on Apoptosis in Experimental Oral Cancer

Objective: Our laboratory is interested in the application of whole foods for cancer chemoprevention. We have recently demonstrated that black raspberries(BRB) inhibit proliferation of human oral cancer cells in vitro, and prevent experimental oral cancer development in long-term dietary and topical hamster cheek pouch(HCP) bioassays. Translation of these findings to the clinical setting demonstrated transcriptional changes in human oral cancers following short-term topical black raspberry(BRB) administration(mean:14.7d). Apoptosis-related genes (i.e., AURKA, BIRC5, BCL2) were significantly overexpressed in tumors while short-term BRB application significantly reduced their expression. Utilization of the HCP model to elucidate human-relevant BRB-mediated mechanisms of chemoprevention requires comparative molecular carcinogenesis studies. We hypothesize that short-term application of BRB to established HCP tumors, a bioassay that mimics our human clinical trial, will reduce the expression of anti-apoptotic genes and modify rates of apoptosis/proliferation. Method: First, in an effort to establish the expression profiles in non-BRB treated tissues, qRT-PCR (Bax, Bcl2, Birc5) was performed on RNA from untreated pouches and dimethylbenz(a)anthracene-induced tumors. Second, Bax, Bcl2, and Birc5, expression was assessed in existing tumors exposed to short-term topical BRB solution(10%) or vehicle. Additionally, rates of proliferation-BrdU/Ki-67 and apoptosis-CASP3/TUNEL will be determined using IHC. Result: Gene expression analysis revealed that Birc5 and Bcl2 were significantly higher in non-BRB treated tumors relative to untreated control pouches (4-fold,5-fold,p<0.001;t-test). Short-term application of BRB solution had no effect on tumor number or size. Investigation of changes in mRNA (Bax, Bcl2, Birc5), proliferation, and apoptosis in tumors after BRB application are being conducted. Conclusion: The expression profile of anti-apoptosis genes evaluated in HCP tumors, relative to normal oral mucosa, is similar to that observed in human oral cancers patients. These data further establish the usefulness of the HCP in food-based cancer chemoprevention studies. The role of apoptosis in BRB-mediated chemoprevention is under investigation. [NIH/NCI R03-CA128043; NIDCR T32-DE14320]