Inhibitory effects of trehalose on malignant melanoma cell growth: implications for a novel topical anticancer agent on the ocular surface.

Purpose. To investigate the inhibitory effects of trehalose on malignant melanoma cell growth. Methods. We cultured human malignant melanoma cells in a medium containing trehalose (control/2.5%/5.0%/7.5%/10.0%) and used the MTT assay to evaluate the growth activities. Subsequently, trehalose was topically instilled on subconjunctivally inoculated melanoma cells in F334/NJcl-rmu/rmu rats, followed by a histopathological evaluation of tumor growth. Using flow cytometry, we compared the distribution of the cell cycle, rate of apoptotic cells, and intracellular factors related to the cell cycle in cultured melanoma cells after trehalose treatment. Results. The MTT study showed that proliferation of melanoma cells was significantly inhibited by ≧ 5% of trehalose concentrations in the culture media. Subconjunctivally inoculated melanoma cell masses were significantly smaller in eyes administered trehalose as compared to controls. Flow cytometry analyses demonstrated that the trehalose groups had increased rates of G2/M phase cells and apoptotic cells in the cell culture. These cells also exhibited increased expressions of cell-cycle inhibitory factors. Conclusions. The current results show trehalose inhibits malignant melanoma cell growth by inducing G2/M cell cycle arrest and apoptosis, suggesting trehalose as a potential candidate for a topical agent to inhibit proliferation of malignant tumor cells of the ocular surface.