Evaluation of Carcinoembryonic Antigen mRNA in Living, Necrotic, and Apoptotic Gastric Cancer Cells by Reverse Transcriptase–Polymerase Chain Reaction

Abstract

Purpose. Positive mRNA expression of carcinoembryonic antigen (CEA) is often found in histologically negative lymph nodes, even in early gastric cancer. Therefore, we examined the differences in mRNA expression in MKN45 gastric cancer cells obtained under various cell conditions, namely, living cells, necrosis, and apoptosis, and assessed the possibility of detecting micrometastasis from these results.

Methods. MKN45 cells were cultured with low-dose anticancer drugs (5-fluorouracil (5FU) + cisplatin (CDDP)) or cytokines (tumor necrosis factor alpha (TNFΑ) + interferon gamma (INFΓ)) to induce apoptosis, or subjected to freezing–thawing to induce necrosis. All the treated cells were stained with propidium iodide and Hoechst and the numbers of living, apoptotic, and necrotic cells were counted. CEA mRNA expression was examined by reverse transcriptase–polymerase chain reaction (RT-PCR) and DNA fragmentation was confirmed.

Results. mRNA expression of CEA and CEA/glyceraldehyde-3-phosphate dehydrogenase (GAPDH) tended to decrease as the apoptotic index (AI) increased in the 5FU + CDDP group. On the other hand, almost no change was seen, even when the AI increased, in the TNFΑ + IFNΓ group. mRNA expression in the necrotic cells was the almost same as that in the living cells.

Conclusion. Positive CEA mRNA expression by RT-PCR could suggest the existence of living cancer cells.