[The management of malignant ascites with a streptococcal preparation, OK-432: relation between the clinical effect and auto-tumor cell killing activity by OK-432-induced ascites-derived lymphocytes].

Twelve patients with malignant ascites caused by gastro-intestinal cancer were treated by intraperitoneal administration of OK-432. Tumor cells from these patients were separated from ascitic fluid and cultured in vitro before OK-432 therapy. OK-432 was given intraperitoneally one to two times a week at doses ranging from 5 to 20 KE suspended in saline. Mononuclear lymphocytes were collected from the fluid at various intervals throughout the therapy. The effect of ascites-derived lymphocytes on ascites-derived autologous tumor cell growth was studied in vitro using microplate assay. Nine (responders) of 12 patients showed complete disappearance or significant reduction of ascitic fluid. Ascites-derived lymphocytes slightly inhibited autologous tumor cell growth only in one case before OK-432 therapy. Lymphocytes collected from ascites after OK-432 injection significantly inhibited auto-tumor cell growth in all of 9 responders. In 3 non-responders, however, auto-tumor cell growth inhibition was found only in one case. Interestingly, lymphocytes from non-responders significantly inhibited the growth of tumor cells taken from responders. Conversely, lymphocytes from responders did not inhibit non-responder-derived tumor cell growth. These findings imply that auto-tumor killing by OK-432-induced lymphocytes may depend more on the condition of the tumor cells than on the condition of the lymphocytes, and that the measurement of auto-tumor killing activity by ascites-derived lymphocytes may be useful as an indicator in OK-432 therapy.