The cucurbitacins are tetracyclic triterpenes found in plants of the family Cucurbitaceae. Cucurbitacins have been shown to have anticancer and anti-inflamatory activities. In this study, we investigated the anticancer activity of cucurbitacin B and dihydrocucurbitacin B extracted from Thai medicinal plant Trichosanthes cucumerina. A mixture compound of cucurbitacin extracts containing cucurbititacin B and dihydrocucurbitacin B in an 8:1 molar ratio was dissolved in 10% dimethylsulfoxide and diluted with DMEM to the desired concentrations prior to use. Cell viability was assessed by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay. Results indicated that mixture of cucurbitacin B (mixture CuB) from T. cucumerina have cytotoxic effect on breast cancer cell lines, SKBR-3, MCF-7, HBL-100 and T47D with the IC50 of 4.60 µg/ml, 88.75 µg/ml, 55.46 µg/ml and >100 µg/ml respectively. Flow cytometry for cell cycle analysis was performed after treated cells with mixture CuB. We found that growth inhibition effect was attributed at G2/M phase arrest and apoptosis. Western blotting analysis showed increase PARP cleavage and decrease Wnt associated signaling molecules including β-catenin, galectin-3, cyclin D1 and c-Myc. We also found that mixture CuB inhibit nuclear-translocation of β-catenin and galectin-3 when compared with vehicle control cells. The depletion of β-catenin and galectin-3 in the nuclease was confirmed by cellular protein fractionation method. TCF promoter, a downstream signaling of Wnt was also disrupted in cucurbitacin B treated cells. TCF promoter assay system was used for assessment of TCF promoter activity. The relative luciferase activity was reduced when we treated cells with mixture CuB for 24 hours. Our data indicate that cucurbitacin B and their derivative dihydrocucurbitacin B from T. cucumerina induce apoptotic cell death and exhibit growth inhibitory effect via inhibition of Wnt signaling pathway.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 769.