The Cotton-Top Tamarin as an Animal Model of Colorectal Cancer Metastasis

Summary

The lack of satisfactory animal models for colorectal cancer has restricted the study of and significant progress in diagnosing and treating this very important human disease. High incidences of colon cancer in the cotton-top tamarin, Saguinus oedipus oedipus, mean that this animal is a potentially useful model for the study of causative agents and mechanistic and therapeutic aspects of this disease.

Age-dependent colonic carcinomas have been diagnosed in 35% of the tamarins that died after one year or more of colony-residence time. Colon cancer occurred in both sexes and in both feral and colony-born animals; all segments of the large bowel were affected. From January 1981 through July 1984, 70% (33/47) of the cotton-tops dying between 4 and 7 years of colony age had colonic cancer. Most tumors were diagnosed antemortem, diagnoses were followed by contrast radiography until the animal was moribund. The tumors metastasized early in the course of the disease (metastases have been found before the primary tumor was recognized grossly), first to the regional lymph nodes and eventually to the lungs, pancreas, and adrenals. No liver metastases have been found in the 81 cases diagnosed to date; the reason for the difference between the metastatic sites in tamarins and the common metastatic site of the liver in human colonic cancer is unknown. Colonic cancers in tamarins arise in the base of the crypts in flat (nonpolypoid) epithelium in the presence of chronic colitis, which can develop acute exacerbations with accompanying diarrhea and weight loss; this association resembles that between long-standing ulcerative colitis in humans and the carcinoma in situ that often develops subsequently. Not only can genetic and nutritional factors be manipulated in this animal model, but also experimental therapeutic protocols can be evaluated prior to human trials; such studies are not always feasible in humans. Investigations of immunologic, anatomic, and physiologic parameters as well as endoscopic biopsy examinations may help in understanding the causative agents, the development, and the metastatic characteristics of this disease and in identifying and developing diagnostic markers for colon cancer.