Induction of apoptosis by sulforaphane in highly metastatic B16F-10 melanoma cells

Sulforaphane (SFN) is a naturally occurring isothiocyanate found in cruciferous vegetables, such as broccoli, cabbage, cauliflower, etc. SFN has received a great deal of attention because of its ability to inhibit cell proliferation and induce apoptosis in several tumor cell lines. Previously, we have demonstrated that SFN inhibits the metastasis of B16F-10 melanoma cells in both in vivo and in vitro models. Melanomas are among the aggressive tumor types because of their notorious resistance to treatment and their high tendency to metastasize. In this study, we investigated the influence of SFN on the induction of apoptosis in B16F-10 melanoma cells, which was evidenced by morphological changes such as membrane blebbing, presence of apoptotic bodies, DNA condensation, and also by nuclear DNA fragmentation. SFN-induced apoptosis was associated with the activation of caspases 3 and 9, Bax, and p53 and the downregulation of Bcl-2, caspase-8, Bid, and NF-kB. Caspase-3 is a most likely candidate to mediate SFN-induced apoptosis. In addition to the caspase-dependent pathway, our results also showed the involvement of proinflammatory cytokines, namely tumor necrosis factor-alpha (TNF-α), interleukin (IL)-1β, IL-6, IL-12p40, and granulocyte-macrophage colony-stimulating factor (GM-CSF), and the nuclear translocation of factors kappa B (NF-κB) p65, NF-κB p50, NF-κB c-Rel, c-FOS, ATF-2, and CREB-1 in SFN-induced apoptosis. These results raise the possibility that SFN may be a promising candidate for molecular-targeting chemotherapy against melanoma.