Experimental colorectal liver metastases. Influence of sex, immunological status and liver regeneration.

The liver is the most frequent site of metastases from colon cancer. To improve our knowledge of liver metastases and to develop new adjuvant therapies, a good animal model is necessary. The aims of this study were to obtain a model of liver metastases with intraportal injection of colon adrenocarcinoma cell aggregates (DHDK12 cell line) and to study the effect of various factors, i.e., sex, liver regeneration and immunosuppression, on the development of liver metastasis. Cell aggregates were injected into the portal vein of 59 syngenic male and female BD IX rats following randomization into three groups. Group 1, (control 12 males and 10 females) received only cell aggregates; group 2 (12 males and 10 females) underwent a 70% hepatectomy before cell injection; group 3 (15 males and 10 females) received cyclosporin A injections at a dose of 10 mg/kg per day for 28 days following cell injection. Autopsy was performed at 10 weeks. Liver metastases were more frequent in the male rats in group 3 than in those in group 1 (80% vs. 30%, p less than 0.04). The rate of liver metastases in females was not increased by immunosuppression (22.2% vs. 12.5%, N.S.). Liver resection (group 2) did not significantly modify the incidence of liver metastasis. No female had liver metastases in this group. This relatively simple model rapidly produces liver metastasis with a high yield, but only in male rats. Besides sexual factors, immunosuppression also increased the rate of experimental liver metastasis, while liver regeneration failed to do so.