Abstract
Melanoma, the most deadly form of skin cancer, is very aggressive and resistant to present therapies. The transcription factor nuclear factor-kappa B (NF-kappa B) has been reported to be constitutively active in many types of cancer. Constitutively active NF-kappa B seen in melanoma likely plays a central role in cell survival and growth. We have established and characterized novel cell lines from our murine melanoma model. Here we report the constitutive activity of NF-kappa B in these melanoma-derived cells, as shown by electrophoretic mobility shift assay and reporter assays. We hypothesized that agents that inhibit NF-kappa B may also inhibit cell proliferation and may induce apoptosis in such melanoma cells. Curcumin has been shown to inhibit NF-kappa B activity in several cell types. In our system, curcumin selectively inhibited growth of melanoma cells, but not normal melanocytes. Curcumin induced melanoma cells to undergo apoptosis, as shown by caspase-3 activation, inversion of membrane phosphatidyl serine, and increases in cells in the sub-G, phase. A curcumin dose-dependent inhibition of NF-kappa B-driven reporter activity correlated with decreased levels of phospho-III(Bot, and decreased expression of NF-kappa B-target genes COX-2 and cyclin D1. This study demonstrates that the use of cells from our model system can facilitate studies of signaling pathways in melanoma. We furthermore conclude that curcumin, a natural and safe compound, inhibits NF-kappa B activity and the expression of its downstream target genes, and also selectively induces apoptosis of melanoma cells but not normal melanocytes. These encouraging in-vitro results support further investigation of curcumin for treatment of melanoma in vivo.