THE EFFECT OF TRANSFECTION OF THE CEA GENE ON THE METASTATIC BEHAVIOROF THE HUMAN COLORECTAL-CANCER CELL-LINE MIP-101

Carcinoembryonic antigen (CEA) has been shown to increase the metastat ic potential of some human colorectal cancer cell lines. To investigat e further the mechanisms involved we have produced three clones (6, 8 and 17) from the poorly differentiated human colorectal cancer cell li ne MIP-101 that have been transfected with the full length cDNA encodi ng for human carcinoembryonic antigen (CEA). They produce CEA with a m ol. wt. of 180000 by Western blotting and secrete it into the culture medium. Clone 6 is a high CEA producer, clones 8 and 17 are intermedia te producers. The doubling time for clone 8 was similar to that of the parent cell line while clones 6 and 17 had doubling times nearly twic e that of the parent cells. These clones are tumorigenic when injected subcutaneously in nude mice are positive for CEA by immunoperoxidase staining and the mice have elevated blood levels of CEA. Clone 6 forme d large aggregates in culture while clone 17 formed smaller aggregates . Clone 8 behaved like the parent cell line with rare cell/cell contac t. Clones 6 and 17 also adhered to CEA coated plastic while clone 8, a neo-transfected control and the parent cell line did not. A significa nt increase in the incidence of hepatic tumors was observed with clone 6 (P < 0.01) and clone 17 (P < 0.02) following intrasplenic injection into nude mice. Immunohistopathology of the hepatic tumors showed str ong CEA staining from clones 6 and 17 with weak staining from clone 8. The parent cell line was negative for CEA as were the neo-transfected controls. Of the neo controls none of 10 had liver colonies. Mice inj ected with clone 6 which developed liver metastasis had the highest pl asma levels of CEA (37.3 +/- 8.8 ng/ml). We observed strong CEA staini ng in Kupffer cells in the normal liver adjacent to the CEA producing tumors. This study provides further evidence for the involvement of CE A in the metastatic process.