Green does not always mean go: A sulfated galactan from Codium isthmocladum green seaweed reduces melanoma metastasis through direct regulation of malignancy features

Melanoma is the most lethal form of skin cancer, with a worldwide increase in incidence. Despite the increased overall survival of metastatic melanoma patients given recent advances in targeted and immunotherapy, it still has a poor prognosis and available treatment options carry diverse severe side effects. Polysaccharides from seaweed have been shown to exert antitumor activities. Here we show in vitro and in vivo antitumor activities of a sulfated homogalactan (named 3G4S) from Codium isthmocladum seaweed in the B16-F10 murine melanoma cell line. 3G4S did not induce cytotoxicity or proliferation changes; however, it was able to reduce solid tumor growth and metastasis, while not inducing side effects in mice. B16-F10 cells traits related to the metastatic cascade were also impaired by 3G4S, reducing cell invasion, colony-forming capacity and membrane glycoconjugates. Therefore, 3G4S shows promising antitumor activities without the commonly associated drawbacks of cancer treatments and can be further explored.