Suppression of liver metastasis by biological response modifiers (BRMs) and the significance of local immunity in the liver

Efficacy of a combination therapy with two biological response modifiers (BRMs), oral PSK and systemic IL-2, was evaluated in a mouse model system of hepatic metastasis from colon cancer. Hepatic metastasis was significantly suppressed and the duration of survival was significantly prolonged by combination therapy, but not by either therapy alone. The therapeutic effects were attributable to the mechanism that non-MHC restricted cytotoxicity of hepatic non-parenchymal lymphocytes activated by IL-2 was augmented by PSK-activated Kupffer cells with direct cell-to-cell contact. These results suggest that local immunity in the liver plays an important role in the formation and development of hepatic metastasis and that the combination of these two BRMs may provide an effective new clinical therapy.

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