[Anti tumor activities of lentinan and micellapist in tumor-bearing mice].

Although Lentinan (LNT) is sold as a medicine, and Micellapist (MME) sold as a food supplement, both LNT and MME are beta-glucans isolated from the Shiitake mushroom (Lentinula edodes). These two substances have been thought to be the same component of Shiitake. In the present study, we evaluated anti tumor activities of LNT and MME in tumor-bearing mice (B10.D2 mice implanted with S908D2 tumor cells) and examined the mechanism of immunopotentiation of these substances. The tumor growth was significantly suppressed in the LNT-treated group. In ex vivo evaluation, the tumor cytotoxicity was significantly reduced by a treatment of splenocytes with anti-CD8 antibody in the LNT-treated group. Furthermore, the tumor cytotoxicity of the LNT-treated group was also significantly reduced by a treatment of splenocytes with anti-CD8 antibody and its complement and with an anti-CD4 and its complement in the effector phase and the induction phase, respectively. A significant prolongation of the survival of tumor-bearing mice as compared to the untreated control group was noted in the LNT-treated group. In the mice treated intraperitoneally with LNT, CD8-positive cells appeared to have suppressed tumor cell proliferation. CD4-positive cells appeared to be involved in this activity of CD8-positive cells. On the other hand, orally administered MME has exerted no clear cytotoxic effects.