Antitumor activity of endostatin against carcinogen-induced rat primary mammary tumors

Endostatin, a M-r, 20,000 fragment of collagen XVIII, potently inhibits the growth of experimental tumors implanted in mice. Here we report the clonin g, expression, and antitumor activity of the rat form of endostatin, When t ested on breast carcinomas arising in female virgin rats after intragastric administration of 9,10-dimethyl-1,2-benzanthracene (DMBA), endostatin indu ced significant inhibition of mammary tumor growth in all of the treated ra ts during a 4-week treatment period without signs of systemic toxicity. Int erestingly, this arrest of tumor growth persisted throughout a four-week of f-therapy period. Moreover, endostatin was effective in counteracting the d evelopment of multiple primary tumors. These results confirm that rat endos tatin is a potent anticancer agent in a carcinogen-induced, spontaneously a rising rat breast cancer model, It not only stops the growth of existing tu mors but also decreases the incidence of the development of multiple neopla stic lesions.