Inhibition of fucoidan on breast cancer cells and potential enhancement of their sensitivity to chemotherapy by regulating autophagy.

Fucoidan is a marine-origin sulfated polysaccharide that has gained attention for its anticancer activities. However, the inhibitory effect of fucoidan on breast cancers by regulating autophagy and its mechanism are not clear, and the chemotherapeutic sensitization of fucoidan is largely unknown. In the present study, the anticancer potential of fucoidan was revealed in MCF-7 and MDA-MB-231 cells. Additionally, we also studied the chemotherapeutic sensitization of fucoidan by combining chemotherapeutic drugs doxorubicin (ADM) and cisplatin (DDP) with fucoidan on breast cancer cells. In the two kinds of human breast cancer cells, cell viability was determined by 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay. Apoptosis was examined with flow cytometry. Transfection assay was used to examine autophagy flow. Western blot was used to examine the expressions of related proteins. Results suggested that fucoidan could induce autophagy and might enhance the sensitivity of breast cancer cells to chemotherapeutic drugs. Mechanistically, fucoidan induced autophagy in breast cancer cells by down-regulating m-TOR/p70S6K/TFEB pathway. In conclusion, our research revealed that fucoidan could induce autophagy of breast cancer cells by mediating m-TOR/p70S6K/TFEB pathway, thus inhibiting tumor development. Furthermore, fucoidan might enhance the sensitivity of breast cancer cells to ADM and DDP, and this enhancement was related to autophagy.