Laminaran from brown alga Dictyota dichotoma and its sulfated derivative as radioprotectors and radiosensitizers in melanoma therapy.

The laminarans are neutral water-soluble β-D-glucans of brown algae possessing potent immunomodulating, radioprotective, and anticancer activities. The aim of the present study was to investigate in vitro anticancer, radioprotective, and radiosensitizing activities of laminaran from brown alga Dictyota dichotoma and its sulfated derivative. The native and sulfated laminarans by themselves at non-toxic doses possessed significant anticancer activity against melanoma cells. Both polysaccharides protected normal epidermal cells, while only sulfated laminaran was able to sensitize melanoma cells to X-rays irradiation resulting in significant inhibition of cell proliferation, colony formation, and migration of cancer cells. The molecular mechanism of this action was related to the inhibition of MMP-2 and MMP-9 proteinases activity as well as down-regulation of kinases' phosphorylation of ERK1/2 signaling cascade. Taken together, the combination of sulfated derivative of laminaran from D. dichotoma with X-ray may serve as a potential treatment strategy for human melanoma.