Presence of carcinoembryonic antigen in hepatic neoplasms of Rivulus ocellatus marmoratus

Carcinoembryonic antigen (CEA), a glycoprotein, is found in the embryonic gut and liver, and is in malignant neoplasms of the intestine and liver of humans. CEA is used as a diagnostic marker for liver and gut neoplasms. The objective of this preliminary study was to determine the usefulness of CEA as a diagnostic marker in liver neoplasms of the mangrove rivulus, Rivulus ocellatus marmoratus, and to compare the results to those reported in mammals. A commercially-available polyclonal antibody kit, Autoprobe III (Fisher Scientific, Houston, Texas), which utilizes avidin-biotinperoxidase complex was used to stain CEA. Diethylnitrosamine-induced neoplasms and control livers from a previous study were used. These paraffin sections were stored at room temperature for at least six years. Both Bouinʹs-fixed and formalin-fixed tissues were used. A positive control (1-day-old mangrove rivulus larvae), and a negative control (omission of CEA antibody) were also used. CEA was found as red deposits in the gut mucosa, epidermis, and the brush boarder and tubular epithelium of the kidney of the 1-day-old-fish, control fish and the fish that had liver neoplasms. No CEA was found in the negative controls, the livers of postive controls and the normal adult livers. The liver tumors that had characteristics of biliary neoplasms stained positively for CEA, but the hepatocellular neoplasms were negative. The presence of CEA in the gut mucosa and the biliary neoplasms of fish is similar to the results of similar studies of human tissues.