Peritoneal Carcinomatosis of Colorectal Origin in Cyclosporine Immunosuppressed Rats.

OBJECTIVE

We evaluate the seeding step of peritoneal carcinomatosis cancer as a surrogate for the role of the omentum in colorectal tumors.

METHODS

The study included 5 groups of adult male Sprague Dawley rats: immunocompetent rats (group 1), immunosuppressed rats without omentectomy (group 2), immunosuppressed rats with omentectomy (group 3), immunosuppressed rats with omentectomy receiving NSAID (group 4), and immunosuppressed rats without omentectomy receiving NSAID (group 5). Except for group 1, the rats were immunosuppressed using cyclosporine orally at a dose of 25 mg/kg/day that was started 48 hours before tumor cell infiltration in the peritoneum. All the rats received an intraperitoneal suspension of 10 million Caco-2 cancer cells. Rats in groups 1, 2, and 3 were followed up without further interventions and rats in groups 4 and 5 received naproxen 180mg/kg until rat sacrifice. Cyclosporine and naproxen were continued in the corresponding groups until the killing after 21 days of tumor cell infiltration.

RESULTS

Fourteen rats survived the experiment during the observation period and remained in good clinical condition except for one rat (from group 4) that deceased at week 2. At day 21 before sacrifice, mean weight variations showed a +4% in group 0, -9% in group 1, -18% in group 2, -31% in group 3 and -36% in group 4. Light microscopy did not identify any tumor cells in the abdominal cavity or thorax solid organs but showed a granulomatous reaction that involved the majority of the organs.

CONCLUSION

The conclusions of this study are limited by the small number of rats as it is a pilot study to design an animal model with peritoneal carcinomatosis. Further steps in this study will include more aggressive cancer cell lines such as HT29 and more aggressive immunosuppression in a larger number of rats.