Indole-3-carbinol enhances ultraviolet B-induced apoptosis.by sensitizing human melanoma cells

Abstract

Indole-3-carbinol (13C) has been found to act against several types of cancer, while ultraviolet B (UVB) is known to induce the apoptosis of human melanoma cells. Here, we investigated whether 13C can sensitize G361 human melanoma cells to UVB-induced apoptosis. We examined the effects of combined 13C and UVB (13C/UVB) at various dosages. 13C (200 mu M)/UVB (50 mJ/cm(2)) synergistically reduced melanoma cell viability, whereas 13C (200 mu M) or UVB (50 MJ/cm(2)), separately, had little effect on cell viability DNA fragmentation assays indicated that 13C/UVB induced apoptosis. Further results show that 13C/UVB activates caspase-8, -3, and Bid and causes the cleavage of poly(ADP-ribose) polymerase. Moreover, 13C decreased the expression of the anti-apoptotic protein, Bcl-2, whereas UVB increased the translocation of Bax to mitochondria. Thus, an increased Bax/Bcl-2 ratio by 13C/UVB may result in melanoma apoptosis. In conclusion, our study demonstrated that 13C sensitizes human melanoma cells by down-regulating Bcl-2.