Immunohistochemical Characterization of Large Intestinal Adenocarcinoma in the Rhesus Macaque (Macaca mulatta).

In rhesus macaques, adenocarcinomas of either the ileocecal junction or colon are common spontaneous tumors in aging populations. The macaque tumors have similar gross and histologic characteristics compared with their human counterpart, but little is known regarding the immunohistochemical expression of proteins that are commonly implicated in the pathogenesis of these tumors in humans. We performed a retrospective review of 22 cases of large intestinal carcinoma in the rhesus macaque and evaluated the expression pattern of a panel of potentially prognostically significant proteins identified from human studies. Histologic characteristics of the tumors included abundant mucin deposition, transmural spread, and lymphatic invasion. All rhesus adenocarcinomas displayed altered expression of 1 or more of CD10, β-catenin, sirtuin 1, cytokeratin 17, and p53 compared with age-matched controls. Zymographic analysis of active matrix metalloproteinases 2 and 9 in the serum from 5 animals failed to reveal statistically significant differences between adenocarcinoma cases and controls. Based on the data presented herein, large intestinal carcinomas in the macaque share many histomorphologic and immunohistochemical similarities to large intestinal tumors in humans. Further validation of this animal model is considered important for the development of novel therapeutics and a better understanding of the pathogenesis.