Protection From Carcinogen Toxicity to Cultured Oral Cells by Raspberries

Objectives: One goal of this project is to reduce toxicity in oral cells exposed to DNA-damaging carcinogens, by treatment with black raspberry extract (BRBE) and its subfractions. It was previously shown that DNA damage from a tobacco-smoke carcinogen, dibenzo(a,l)pyrene (DBP) in cultured oral cells, was more rapidly repaired when cells were post-treated with BRBE. Thus, if DNA damage leads to toxicity, treatment with BRBE should also reduce DBP toxicity. A second goal is to determine the effects of BRBE on cell death by a second DNA-damaging carcinogen – UV light. A related goal was to determine the effects of BRBE on expression of several DNA repair genes.
Methods: Cell lines of human oral leukoplakia (MSK leuk1) and oral squamous cell cancer (1483) were treated with the ultimate carcinogenic metabolite of DBP, DBP-diolepoxide (DBPDE) or irradiated with UV light. The cells were then post-treated with BRBE. We monitored the number of dead cells in cell supernatant, as well as cell survival -the latter using an MTT assay. BRBE was then partially fractionated to generate several aqueous and organic extracts. Lastly, a qPCR assay was run to identify genes in the DNA repair pathway modulated by BRBE.
Results: Cell toxicity increased with dose of DBPDE, or UV irradiation time. BRBE reduced cell death by 50 – 90% at concentrations from 12 - 150ug/ml and cell survival was increased by BRBE. Most of the protective components of BRBE partitioned into n-butanol. In the qPCR assay, ERCC3, a gene important in the nucleotide excision repair pathway, was induced four fold over control by BRBE.
Conclusions: The results of this study suggest application in terms of enhancing DNA damage repair. As DNA damage can lead to cancer, this study may translate into the use of certain BRB extracts for the prevention of oral cancer in smokers.