Butein Induces Apoptosis in Human Uveal Melanoma Cells Through Mitochondrial Apoptosis Pathway

Purpose: To study the cytotoxic effects and related signaling pathways of butein on human uveal melanoma cells in vitro. Materials and Methods: Three human uveal melanoma cell lines (M17, SP6.5, and C918), retinal pigment epithelial (RPE) cells and scleral fibroblasts were treated with butein at different dosages. The effects of butein on cell viability were assessed by using the MTT assay. Cell apoptosis was determined using annexin V-FITC/ethidium homodimer III flow cytometry. Mitochondrial transmembrane potential changes were assessed by using the JC-1 fluorescent reader, cytosol cytochrome c levels, and the activities of caspase-3, -8, and -9 were measured by using an enzyme-linked immunosorbent assay or colorimetric assay. Results: Butein reduced the cell viability of cultured human uveal melanoma cells in a dose-dependent manner (10, 30, and 100 mu M), with IC50 at 13.3 mu M and 15.8 mu M in SP6.5 and M17 cell lines, respectively. Similar effects were also found in a highly aggressive and metastatic C918 cell line (IC50 16.7 mu M). Butein at lower concentrations (10-30 mu M) selectively reduced the cell viability of uveal melanoma cells, without affecting cell viability of RPE cells and fibroblasts. Butein-induced apoptosis of melanoma cells, increased mitochondrial permeability and the level of cytosol cytochrome c, caspase-9 and -3 activities (but not caspase-8) in a dose-dependent manner. Conclusions: Butein has selectively potent pro-apoptotic effects on cultured human uveal melanoma cells via the intrinsic mitochondrial pathway.