Antitumor effect of combined intraperitoneal administration of human recombinant interferon-beta and interferon-gamma against intraabdominal carcinomatosis in nude mice.

The development of useful therapy for intraabdominal carcinomatosis originating from gastrointestinal cancer is an important theme in cancer therapy. We developed recently an experimental model of intraabdominal carcinomatosis in nude mice by intraperitoneal transplantation of human colon cancer cells (RPMI 4788). Using this model, we investigated the antitumor effects of recombinant human interferon (rIFN)-beta and rIFN-gamma administered singly or in combination. Treatment was initiated 2 days after CD-1 nude mice were inoculated intraperitoneally with 5 X 10(6) RPMI 4788 cells. Intraperitoneal administration for 10 consecutive days of either rIFN-beta (2.5 X 10(5) IU/mouse/day) or rIFN-gamma (2.5 X 10(5) JRU/mouse/day) resulted in a significant prolongation of survival compared with the saline control group [survival in the control: 41.8 +/- 5.6 days (mean +/- SD)]. Combined administration of rIFN-beta and rIFN-gamma for 10 days yielded a marked synergistic effect on the prolongation of survival (114.0 +/- 8.2 days). However, combined administration of rIFN-beta and rIFN-gamma in a single dose equal to the total dose given fractionally over 10 days did not yield a synergistic effect. These results suggest that daily administration of rIFN-beta and rIFN-gamma combined may provide a highly potent antitumor effect against human peritoneal carcinomatosis.