Activation of multiple effector pathways of immune system by the antineoplastic immunostimulator acidic polysaccharide ginsan isolated from Panax ginseng

In the present study an acidic polysaccharide ginsan, with a molecular weight of 150,000, devoid of lectin properties, was purified from Panax ginseng C.A. Meyer (Araliaceae). Ginsan induced the proliferation of T cells and B cells. Spleen cells became cytotoxic to a wine range of tumor cells without major histocompatibility complex-restriction after 4 or 5 days culture in vitro with ginsan. For the generation of these ginsan-activated killer (AK) cells adherent macrophages and CD4⁺ cells were needed as accessory cells. The generation of ginsan-AK cells was blocked in the presence of anti-lL-2, anti-IFNγ, anti-IL-1 of anti-TNFα antibodies, showing the importance of these cytokines in the process. The surface phenotypes of the 4 day-cultured ginsan-AK cells was Thy1+, AsGM₁+, CD8+, which is distinct from rlL-2 induced lymphokine activated killer (LAK) cells that were CD8^-. The ginsan also activated macrophages to produce reactive nitrogen intermediates and become tumoricidal. It also exhibited significant in vivo antitumor activity against B16 melanoma cells lines, and in the benzo(a)pyrene-induced autochthonons lung tumor model, at much lower closes than the maximum tolerate doses. Indeed, no mice died, which injected with ginsan at 1 g/kg body weight intraperitoneally. In conclusion, 'ginsan' could potentially be an ideal nontoxic antineoplastic immunostimulator by activating multiple effector arms of the immune system.