A new and advantageous model for colorectal cancer: its comparison with previous models for a common human disease.

Weekly subcutaneous injection of 10 mg/kg body wt. of N-nitrosobis(2-oxopropyl)amine (BOP), a pancreatic carcinogen in Syrian golden hamsters, induced colorectal cancer in MRC rats in 67% of all males and 33% of all females that survived beyond 43 and 68 weeks, respectively. Tumors were concentrated in specific segments of the large bowel and not found in the small intestine. Although the distribution of cancer in the cecum, and ascending and descending colon was similar in both sexes, rectal cancer predominated significantly in males. These data and the tumor morphology indicate the present model more closely resembles the corresponding human disease than do models in previous relevant experimental studies.