Involvement of cholesterol depletion from lipid rafts in apoptosis induced by methyl-β-cyclodextrin.

Methyl-β-cyclodextrin (M-β-CyD), which is widely used as a lipid rafts disrupting agent, is known to induce cytotoxicity at high concentration. In the present study, we investigated the potential of M-β-CyD as an antitumor drug. M-β-CyD markedly caused apoptotic cell-death in KB cells, a human oral squamous carcinoma cell line, Ihara cells, a highly pigmented human melanoma cell line, and M213 cells, a human cholangiocarcinoma cell line, through cholesterol depletion in cell membranes. The DNA content and mitochondrial transmembrane potential in KB cells were significantly decreased after treatment with M-β-CyD. Additionally, M-β-CyD elevated the caspase-3/7 activity in KB cells. Meanwhile, M-β-CyD did not induce the formation of autophagic vacuoles in KB cells. M-β-CyD drastically inhibited the tumor growth after intratumoral injection to Colon-26 cells-bearing mice. These results strongly suggest that M-β-CyD induced apoptosis in tumor cells and had the potential a novel antitumor agent and/or its lead compound.