Correlation Between NKG2DL Expression and Antitumor Effect of Protein-bound Polysaccharide-K in Tumor-bearing Mouse Models

Background/aim We investigated the relationship between the expression of natural killer group 2, member D ligands (NKG2DLs) and the antitumor effects of protein-bound polysaccharide-K (PSK). Materials and methods PSK was administered to evaluate its effectiveness against tumor growth. The expression of Rae-1 and H60 were analyzed in multiple cell lines. Results PSK showed the highest antitumor effects in mice implanted with cells expressing neither Rae-1 nor H60. PSK had little antitumor effect in mice implanted with cells expressing both Rae-1 and H60. A correlation between the expression of NKG2DLs and the antitumor effect of PSK was observed. After PSK administration, INF-γ production in CD8+ T cells increased in mice with cells expressing neither Rae-1 nor H60, but did not change in mice implanted with cells expressing both Rae-1 and H60. Conclusion We demonstrated that the expression of NKG2DLs affects tumor immunity and the efficacy of immuno therapy in tumor-bearing mouse model.