[Antitumor activity of schizophyllan (SPG) against syngeneic ACI/N rat tumor, AMC-60 fibrosarcoma and BC-47 bladder cancer].

The antitumor activity of schizophyllan (SPG) against syngeneic ACI/N rat tumor, AMC-60 fibrosarcoma and BC-47 bladder cancer was investigated. Intramuscular injection of SPG caused a marked suppression of AMC-60 tumor growth. Results obtained with cytotoxicity tests in vitro and lymphoblastogeneic response in vitro suggest the association of enhanced macrophage cytostasis and high reactivity of lymphoid cells with the resistance of the host to AMC-60 tumor. Moreover, SPG showed pronounced antitumor activity against BC-47 bladder cancer. The highest therapeutic effectiveness was obtained when SPG injection was started at an advanced stage of the tumor, 4 out of 15 rats treated being completely cured of cancer. Cytotoxicity tests in vitro and neutralization tests in vivo indicated the important role of cytotoxic lymphocytes as well as activated macrophages in the host defence mechanism against BC-47 cancer. This, taken together with the fact that the rats cured completely by SPG therapy acquired transplantation resistance to BC-47 cancer, shows that SPG may promote tumor immunity in the host.