[Effect of PSK on DMH (dimethyl hydrazine) induction of cancer]

The effect of PSK on the induction of intestinal tumors by DMH in Wistar rats was examined. One hundred and fifty-one rats were divided into two groups. Seventy-two rats were treated with DMH alone and 79 rats were treated with DMH and PSK. All animals were subjected to a sequential autopsy and all lesions within the GI tract were examined macroscopically and histologically. Tumor incidence in the DMH and PSK treated group was significantly lower than that in the DMH treated alone, and peritoneal disseminations and distant metastases were also significantly decreased in the PSK treated rats. The number of circulating lymphocytes dropped in the 25th and 35th week in the group treated with DMH alone, but the drop in the PSK treated group was not remarkable. DTH reaction to PPD and antibody forming capacity to SRBC were well maintained in the PSK treated rats than in those treated with DMH alone. The most interesting findings in these experiments were the differences concerning the serum blocking activities and serum immunosuppressive factor in these two groups; these were markedly reduced in PSK-treated rats. From these experiments, the mechanisms may be explained by the competitive action of PSK against the immunosuppressive factor produced by a tumor-bearing host.