Prevention of carcinomatosis and bloody malignant ascites in the rat by an inhibitor of angiogenesis.

It has previously been shown that protamine sulfate is an angiogenesis inhibitor. Regional infusion of protamine into the peritoneal cavity is now reported to prevent the growth of intraperitoneal vascularized tumor masses in rats. Walker 256 carcinoma was implanted directly into the liver or into the peritoneal cavity of rats. Hepatic implants grew in the liver with metastases to the wound and mesentery. Injected tumor cells grew as solid tumor masses in the mesentery. Bloody ascites developed after 7 days. Animals received an intraperitoneal infusion of protamine or saline. Protamine significantly inhibited growth of solid tumors in the mesentery (P less than 0.001). Histology showed tumor cells growing only in monolayer but without vascularization. Ascites was not bloody. In saline-treated animals large vascularized tumors grew in the peritoneal cavity and ascites became bloody.