The oncolytic activity of the yeast polysaccharides, zymosan and hydroglucan, has been tested against a number of well established mouse tumors. The most significant results were obtained with intravenously injected hydroglucan, which induced total regression of 90–95 per cent of Sarcoma 37 and Sarcoma 180, and 83 per cent of Krebs-2 carcinoma, with no lethality. Lower percentages of regression of these tumors followed administration of the same amounts of hydroglucan by the intraperitoneal, intramuscular, and subcutaneous routes. The ascites forms of these tumors were not affected by either of the yeast products. Likewise nonresponsive were: Carcinoma 755, Rhabdomyosarcoma MC-1a, spontaneous mammary tumors arising in C3H mice, and a transplantable tumor derived therefrom in this laboratory. The mechanism of action of these agents does not appear to be the same as that involved in tumor destruction by bacterial polysaccharides. Tumor resorption and necrosis occur without hemorrhage, through an apparent host-mediated reaction which involves stimulation of phagocytic elements of liver and spleen.
Supported in part by grant No. CY-3228 from the National Cancer Institute, USPHS, and in part by a grant from the New York Cancer Research Institute.