Abstract 252: Effects of Black Raspberry Extract (BRB) and Related Compounds on Mutagenesis Induced by the Tobacco Carcinogen, Dibenzo(a,l)pyrene and Its Metabolites in Cultured Rat Oral Fibroblasts

Abstract BRB powder and extracts have been shown to inhibit tumorigenesis in oral and other alimentary-tract sites in animal models; and have promising effects on markers of carcinogenesis in several human trials. The purpose of this study was to compare the inhibitory effects of BRB and two related compounds (protocatechuic acid and kaempferol) on mutagenesis and DNA adduct formation induced by the tobacco carcinogen dibenzo[a,l]pyrene (DBP) and its metabolites, DBP-diol and DBP-diol epoxide (DBPDE), in a rat oral epithelial cell line. Mutagenesis and DNA adduct formation induced by DBP, DBP-diol and DBPDE were monitored in rat oral epithelial and fibroblast cells, containing a lacI mutagenesis reporter gene; and the order of potency in both adduct formation and mutagenesis was DBPDE>>DBP-diol>>DBP in both cell types. In the fibroblasts for mutagenesis, the potencies (in units of mutants/10E5 pfu /uM) were: DBPDE, 16,320; DBP-diol, 25; DBP1.7, (above background); background was 2.9., Similar results were obtained for epithelial cells. Analysis of DNA adducts levels is still in progress and results thus far (in units of cis + trans isomers of anti-DBPDE-dA/10E6 A, are: DBPDE, 2096, DBP-diol ≈1.8, DBP < 1.0. The above results are consistent with mutagenesis being dependent on DNA adducts and indicate this cell culture model reflects initiation of carcinogenesis. The background level of mutagenesis was greater in the epithelial cells, so the fibroblasts were then used for subsequent mutagenesis experiments. As initiation by DBP and DBP-diol requires biotransformation to an ultimate mutagen/carcinogen (in this case DBPDE) we initially assayed inhibition of DBP-diol induced mutagenesis, so that effects of BRB on processes involved in activation, as well as effects on steps after formation of DBPDE would be detected. The parent compound, DBP, was not employed because it was very weakly mutagenic, and studies with DBPDE are still in progress. Treatment of cells with one µM DBP-diol led to an increase in mutant fraction from 2.9 +/- 0.8 to 25 +/- 2.3 mutants/10E5 pfu. When pretreated with BRB and its related compounds 4 hours before the addition of DBP-diol, significant inhibition of mutagenesis was observed. With 3 uM protocatechuic acid mutagenesis was reduced to 15.6 +/- 3.7 and with 3uM kaempferol to 13.3 +/- 4.1 mutants/10E5 pfu. Pretreatment of the cells with 25 ug/ml of an anthocyanin-enriched BRB extract (a concentration previously used in colon cancer cells), reduced mutagenesis to 9.8 +/- 0.35 mutants/10E5 pfu. These results suggest that BRB and specific related components will be protective against carcinogenesis induced by certain tobacco carcinogens. Supported by NIH grant #CA173465. Citation Format: Joseph B. Guttenplan, Wieslawa Kosinska, Tianzhen Han, Kun-Ming Chen, Shangmin Zhang, Krishnegowda Gowdahalli, Amin Shantu, Gary Stoner, Karam El-Bayoumy. Effects of black raspberry extract (BRB) and related compounds on mutagenesis induced by the tobacco carcinogen, dibenzo(a,l)pyrene and its metabolites in cultured rat oral fibroblasts. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 252. doi:10.1158/1538-7445.AM2014-252