A study on colon cancer-prone rats of WF-Osaka strain

We have established a colon cancer-prone substrain in WF strain rats strictly bred by sister x brother mating for more than 20 years. Colon carcinomas were located only in the ascending colon with no remote metastases. Each incidence of colon carcinoma varied from 30 to 40% in the respective investigation. There was no apparent sex difference. Approximately 9% of colon carcinomas were associated with gastric carcinoma in the prepyloric region and they died within four months of age due to malnutrition and intestinal bleeding. There were a few cases of carcinomas of the terminal ileum and the rectum. All of these carcinomas from three different portions showed histologically well differentiated tubular adenocarcinoma. It was found that about 40% of colon carcinomas showed spontaneous regression in the period from four to twelve months old. We have also succeeded in establishing two lines of the transplantable colon carcinoma (C1 and C2) and the transplantable gastric carcinoma (S1 and S3) from those of spontaneous colon carcinomas and gastric carcinomas. Then recipient female rats inoculated intraperitoneally with these transplantable carcinomas newly developed adenocarcinomas of the corpus uteri, which had never been found in the rats of this strain. In addition, the transplantable tumor line of adenocarcinoma of the corpus uteri was also established (U2). When transplanted these tumors intraperitoneally (S1, S3, C1, C2 and U2), male and female recipient rats extremely increased in the incidence of carcinomas of the stomach and the colon. As far as female recipient rats were concerned, a large number of carcinomas of the corpus uteri were also found regardless of the derivation of tumors. We believe that the established colon cancer-prone rat strain (WF-Osaka) as well as those of transplantable tumor lines will open a further research fields and will be available as an animal model of colon cancer for human beings.