[Production of experimental colonic cancer in dog. A comparative study of administrative methods of carcinogen]

It may be useful for therapeutic purposes if experimental colonic cancer can be produced in larger animals. Our protocols for experiment to produce colonic cancer in dog were as follows: Two beagle and 12 mongrel dogs were used. Endoscopic examination was done every month or every other month. 1,2-Dimethylhydrazine (DMH) was given subcutaneously in 3 mongrel dogs once a week for 25 months. The protrusion like verruca was observed macroscopically in colonic mucosa in two of them. Histologically it was like lymph follicle hyperplasia in the submucosa. N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) soaked in sponge was inserted daily into the rectum of 2 beagle and 2 mongrel dogs for about 20.4 months. A leiomyoma of the colon was detected histologically in one beagle. N-ethyl-N'-nitro-N-nitrosoguanidine (ENNG) soaked in sponge was inserted daily into the rectum of 4 mongrel dogs for about 26.5 months. During follow up study, adenoma of the colon was detected by biopsy in one dog. ENNG suppository (containing 50 mg of ENNG) was administered through the anus in 3 mongrel dogs. Colon cancer was induced in all of three dogs. There were metastases to the liver, lung and lymph nodes in one of them. Colonic cancer was successfully induced in dogs by suppository of ENNG into the rectum. This model seems to be the most useful for producing experimental colonic cancer.