Treatment of cancer ascites by intraperitoneal administration of a streptococcal preparation OK-432 with fresh human complement--role of complement-derived chemotactic factor to neutrophils.

The role of complement in the polymorphonuclear leukocyte (PMN)-mediated tumor cell destruction in cancer ascites was investigated in relation to a streptococcal preparation OK-432, a so-called biological response modifier. Incubation of OK-432 with fresh human serum at 37 degrees C for 60 min resulted in the generation of C3a and C5a chemotactic factors. Intraperitoneal (i.p.) injection of the mixture to a patient with cancer ascites revealed an accumulation of PMNs in the ascitic fluid for a longer period with a rapid reduction of the ascitic fluid, than an intraperitoneal injection of OK-432 alone examined in the same patient. PMNs were found to invade clusters of the tumor cells and then form rosettes followed by the destruction of tumor cells. These findings induced by OK-432 continued over 10 days in the presence of fresh serum, while diminished within 3-4 days when OK-432 alone was injected. When fresh human plasma or fresh frozen plasma was used instead of serum and i.p. injected with OK-432 avoiding preincubation, the same cytological and clinical changes were observed in other patients. These data strongly indicate that OK-432 activates human complement either in vitro or in the peritoneal cavity, and induces PMNs to accumulate in the ascitic fluid. Although the mechanism of killing of tumor cells by PMNs is obscure, addition of human serum or plasma to i.p. use of OK-432 seems to be valuable for the management of patients with malignant ascites.