8:00 AM Abstract No. 185 - ■ Dr. Constantin Cope Medical Student Research Award Establishment of human metastatic colorectal cancer model in rabbit liver. Pilot study

Abstract

Purpose To develop a human metastatic colorectal cancer model in a rabbit liver. Materials and Methods Immunosuppression was induced in 4 adult New Zealand White rabbits weighing 3.5 to 4.5 kg with daily sub-cutaneous injection of 15 mg/Kg Cyclosporine A (CsA). On day 3 open laparotomy was performed and the 4 livers were injected with 0.2 ml (1.8x10x (5) cells) suspension of HCT-116 and HT-29 human colorectal carcinoma (American Type Culture Collection, Manassas, VA), using a 1 ml luer lock syringe and 25G5/8 needle. On day 10 the CsA dose was reduced to a 10 mg/Kg daily maintenance dose until necropsy. Rabbits were weighed weekly. Closely monitoring for CsA side effects (weight loss, gingival hyperplasia, gut motility modification). Rabbits were serially sacrificed 5, 6, 7, 8 weeks after cells injection. Liver tumor and tissues control were collected for histopathology and immunohistochemical analysis. Results Tumor growth was observed in 3 rabbits (75%) from HT-29 cell. Tumors measured 3, 4 and 6 mm after 5, 6 and 8 weeks sacrifice respectively. Microscopically, tumors were confirmed to contain hyperchromatic, pleomorphic cells surrounded by fibrous stroma and chronic inflammation. Some cells were present in circumscribed clusters suspicious for lymphovascular invasion, while others exhibited single cell infiltration of fibrotic demoplastic-type stroma. Immunohistochemistry showed that the tumor cells stained positively for monoclonal carcinoembryonic antigen (CEA), polyclonal CEA, and cytokeratin 20. Morphologic and immunohistochemical findings are compatible with involvement by the poorly differentiated colorectal cancer cell lines. No gross tumor growth or microscopic viability was observed from HCT-116 cell injection. Extra hepatic manifestations included minimal gum hyperplasia with in 1 rabbit at 2 weeks and 2 rabbits at 5 weeks (75%) under immunosuppressant therapy treated with Azithromycin 62.5 mg by mouth once a day for 7 days. Decrease in gut motility in 3 rabbits (75%) treated with Cisapride 0.5 mg/kg by mouth every 12 hours until improved. 100% recovery reached. Conclusion We successfully developed human metastatic colon cancer model in immunosuppressive rabbit liver using HT-29 cell lines.