Real-time PCR (TaqMan PCR) quantification of carcinoembryonic antigen (CEA) mRNA in the peripheral blood of colorectal cancer patients.

Reverse transcriptase-polymerase chain reaction (RT-PCR) has been utilized to detect living micrometastases of cancer cells in the lymph node, ascites or circulation system. However, the method was so sensitive that false-positives happened frequently. Therefore we have developed a quantification of CEA mRNA using real-time PCR to detect living cancer cells in the circulating blood and examined its usefulness as a predictive marker for liver metastases of colon cancer. In cell spiking experiments, it was possible to detect CEA mRNA in 10(1) cancer cells diluted in 10(7) normal lymphocytes. In the blood samples of cancer patients, the CEA mRNA level was significantly higher in Dukes' D patients than in the other clinical stages of colorectal cancer. This indicates that quantification of CEA mRNA is useful for the evaluation of colorectal cancer progress and that the post-operative increase of CEA mRNA can be a predictive marker for micrometastasis.