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Plant polysaccharide PSK: cytostatic effects on growth and invasion; modulating effect on the expression of HLA and adhesion molecules on human gastric and colonic tumor cell surface.

2001; National Institutes of Health; Volume: 21; Issue: 2A Linguagem: Inglês

Chikage Iguchi, Yoshinori Nio, Hiroshi Takeda, Kunihiro Yamasawa, Noriyuki Hirahara, Tomoko Toga, Masayuki Itakura, Katsuhiro Tamura,

Monoclonal and Polyclonal Antibodies Research

PSK is a plant polysaccharide widely used for cancer immunotherapy in Japan and other Asian countries. It is considered that its antitumor effect is derived from its immunomodulating activity on the tumor-bearing host. The present study was designed to assess the direct action of PSK on in vitro proliferation and invasion of human KATO-3 gastric and Colo205 colonic cancer cell lines, and the expression of surface molecules such as HLA and adhesion molecules on these cells. The in vitro growth of KATO-3 cells was significantly inhibited by 100 micrograms/ml of PSK 48 hrs after culture initiation, and that of Colo205 was significantly inhibited by 10 and 100 micrograms/ml of PSK 24 hrs after culture initiation. The effect of PSK on the in vitro invasion of the tumor cells, assessed with a Matrigel invasion chamber, revealed that invasion of KATO-3 and Colo205 cells was inhibited by more than 10 micrograms/ml and more than 5 micrograms/ml of PSK, respectively. KATO-3 cells expressed HLA-ABC, HLA-A2/A28, HLA-DR very weakly, at almost baseline levels, but HLA-B27, B2-microglobulin and HLA-DQ were expressed at various levels. After treatment of KATO-3 cells with PSK, the expression of HLA-B27 and beta 2-microglobulin was significantly enhanced. Colo205 cells expressed all class-I antigens tested in this study at different levels, but class-II antigens at almost baseline levels. PSK also enhanced the expression of class-I antigens on Colo205 cells. ICAM-1 was expressed on KATO-3, but not on Colo205. The expression of ICAM-1 was enhanced to a greater extent by treatment with 10 micrograms/ml than with 100 micrograms/ml of PSK. Adenocarcinoma antigen AC-81 was strongly expressed on both cell lines, but PSK-treatment significantly enhanced its expression. These results suggested that enhancement of HLA class-I expression on tumor cells after PSK treatment may be one of the mechanisms responsible for the induction of anti-tumor immunity by PSK.