Antitumor effect of combined use of OK-432 and yeast cell wall with mitomycin-C in mice.

Tumor-inhibitory effect of combined use of mitomycin-C and streptococcal preparation (OK-432) or yeast cell wall (YCW) was examined. Twenty-four hours after intraperitoneal inoculation of Ehrlich carcinoma cells, combination therapy was carried out and tumor growth was observed for 40 days. About one-half of mice treated with yeast cell wall at a single dose of 1 mg survived free of tumor. Mitomycin-C at a single dose of 2 microgram was not effective. However, in combination with yeast cell wall, tumor suppression was observed in 70% of the mice. This tumor-inhibitory effect was enhanced by subsequent treatment with OK-432 or yeast cell wall. When these materials were injected separately or in combination with mitomycin-C, the number of peritoneal exudate cells increased about 3 to 6 times after 3 days and these cells exhibited cytotoxic effect on tumor cells. Hemagglutinating antibody to sheep erythrocytes was hardly affected by the combination therapy.