Effective inhibition of a Strongylocentrotus nudus eggs polysaccharide against hepatocellular carcinoma is mediated via immunoregulation in vivo

► We investigated the antitumor activity and its immunological mechanisms of SEP in H22-bearing mice. ► SEP effectively inhibited hepatocellular carcinoma via enhancement of splenocyte proliferation, T cell numbers and activity. ► SEP also elevated IL-2 and TNF-α secretion as well as IgA, IgM and IgG levels in the serum. ► Erk phosphorylation and NFAT promoter activated by SEP promoted the transcription and expression of downstream gene IL-2.