DETECTION OF COLORECTAL-CANCER CELLS IN PERIPHERAL-BLOOD BY REVERSE-TRANSCRIPTASE POLYMERASE-CHAIN-REACTION FOR CYTOKERATIN-20

The staging of colorectal cancer currently depends an pathological exa mination of the surgical specimen and regional lymph nodes, accompanie d by imaging tests such as computed tomography (CT) scanning. However, alternative molecular methods to detect circulating tumour cells in b lood or bone marrow may provide additional information about the exten t of disease and prognosis. We have previously reported the developmen t of a reverse-transcriptase polymerase chain reaction (RT-PCR) for cy tokeratin 20 (CK 20) mRNA to detect circulating epithelial tumour cell s. In this study, we report on the application of this method for dete cting circulating tumour cells in patients with colorectal cancer. Usi ng this method, CK 20 mRNA was detected in 8/8 human colorectal cancer cell lines, in 8/9 biopsies from primary colorectal rumours and in 9/ 10 biopsies of liver metastasis in patients with metastatic colorectal cancer, suggesting that CK 20 may be a useful target for the detectio n of circulating tumour cells in this patient group. in spiking experi ments, 10 cells were consistently identified in 2 ml of whale blood (1 x 10(6)-1 x 10(7) mononuclear cells). In 12/25 (48%) peripheral blood samples from patients with known metastatic colorectal cancer, CK 20 mRNA was detected. However, there was no correlation between the detec tion of CK 20 mRNA in the peripheral blood and disease progression and survival in this group Of patients. CK 20 mRNA was detected in 1/12 n ormal blood samples, which raises questions about the absolute specifi city of CM 20 expression. (C) 1998 Wiley-Liss, Inc.