Decrease in experimental liver metastasis in mice after treatment with pyran copolymer

Intravenous injection of pyran copolymer (divinyl ether-maleic anhydride) 24 h prior to intravenous injection of B16 melanoma in C57/BL6 mice greatly decreased the number of liver metastases. If the pyran copolymer was administered 3 days after injection of tumor cells, the number of metastases was not significantly decreased. Pyran copolymer has been reported to stimulate interferon production and increase clearance of particulate matter by the reticuloendothelial system. The results of this experiment suggests an important role played by the reticuloendothelial system in experimental liver metastasis.