Quantification of micrometastases in lymph nodes of colorectal cancer using real-time fluorescence polymerase chain reaction

The expression of carcinoembryonic antigen (CEA) mRNA was assessed in 102 l ymph nodes (LNs) obtained from seven colorectal cancer patients by both the conventional non-quantitative RT-PCR and quantitative RT-PCR. The number o f CEA-expressing cells was calculated compared with CEA-expressing MKN-45 c ell line as a standard control. Using the quantitative RT-PCR, the relative number of CEA-expressing cells ranged between 1.3x10(3) and 5.7x10(6) in 1 6 histologically positive LNs and between 2.3x10(1) and 8.1x10(5) in 10 his tologically negative and RT-PCR positive LNs. In both histologically and RT -PCR negative LNs, the relative cell number was <4.0x10(2). Our results dem onstrated that quantifying the amount of metastasis might enhance the relia bility of RT-PCR detection assay as a diagnostic tool for the detection of cancer micrometastases.