Abstract 607: Biotransformed soybean extract (BSE) inhibits melanoma cell growth and viability through activation of the extrinsic apoptotic pathway.

Abstract

Abstract Melanoma is recognized as one of the most aggressive cancers with relatively high propensity for metastasis. The prognosis of melanoma remains poor in spite of treatment advances, emphasizing the importance of additional preventive measures. Isoflavonoids have become not only potential chemopreventive, but also important therapeutic natural agents. In this study, employing A375 melanoma cells, we evaluated the antiproliferative and proapoptotic properties of biotransformed soybean extract (BSE). Chromatographic analysis and ninhydrin-based assays demonstrated that the concentration of daidzein, genistein and aminoacids/peptides present in BSE, fermented by Aspergillus awamori is much higher than in the non biotransformed extract (NBSE). Initial experiments comparing the efficacy of the extracts in preventing cancer cell growth showed that treatment of highly invasive melanoma cells (A375 and 451Lu) with BSE resulted in a dose-dependent inhibition of growth and viability, 24 h post-treatment, as assessed by 3-[4,5-dimethylthiazol-2-yl] 2,5-diphenyl tetrazoliumbromide assay. In contrast, treatment with similar doses of NBSE failed to inhibit melanoma cell viability. Further studies in A375 melanoma cells showed that decrease in cell viability with BSE (1.5-1.9 mg/ml; 24 h) treatment was associated with induction of apoptosis. Immunoblot analysis revealed that BSE treatment resulted in (i) induction of PARP cleavage and activation of caspase-3, -7, and -8; (ii) decreased FLIPL; and (iii) increased expression of TRAIL and its receptor DR4. BSE did not activate the intrinsic apoptotic pathway in A375 melanoma cells, as no change was observed in caspase -9 expression. In addition, the expression of Bcl-2 family of apoptotic proteins such as Bax, Bcl-2 remained unaffected with BSE treated cells. BSE treatment increased the phosphorylation and activation of IKK, IκBα degradation and p65/NFκB translocation to the nucleus suggesting that NFκB signaling may be involved in BSE mediated apoptosis. Taken together, our findings indicate that the biotransformation of soybean plays a crucial role in the anti-cancer effect of the extract observed in melanoma cells and further studies are warranted to define the active agent present in BSE and define its mechanism. Citation Format: Fernanda Maria Pinto Vilela, Deeba N. Syed, Jean-Christopher Chamcheu, Laura C. Castro, Vanessa S. Fortes, Maria Jose V. Fonseca, Hasan Mukhtar. Biotransformed soybean extract (BSE) inhibits melanoma cell growth and viability through activation of the extrinsic apoptotic pathway. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 607. doi:10.1158/1538-7445.AM2013-607 Note: This abstract was not presented at the AACR Annual Meeting 2013 because the presenter was unable to attend.