Expression of cytokeratin 20 in the blood of patients with disseminated carcinoma of the pancreas, colon, stomach, and lung.

Cytokeratins are constituents of the intermediate filaments of epithelial cells that are expressed in various combinations depending on the epithelial type and the degree of differentiation. The recently identified cytokeratin 20 (CK-20) was found to be expressed in colonic, gastric, and pancreatic carcinoma tumor tissues. A low rate of incidence of expression of CK-20 was found in tumor tissue from lung carcinoma but no expression was found in blood even with the sensitive reverse transcriptase-polymerase chain reaction (RT-PCR) method. The objective of the current study was to examine whether CK-20 expression in the blood can be used as a biomarker for the detection of dissemination in patients with carcinoma of the colon, stomach, and pancreas. In the current study, RT-PCR was used to determine the expression of CK-20 in the blood cells from patients with metastatic colon carcinoma (n = 22), metastatic pancreatic carcinoma (n = 28), metastatic gastric carcinoma (n = 18), metastatic lung carcinoma (n = 13), no metastatic colon carcinoma (n = 13) and no known malignant diseases (n = 22). RNA was extracted from cell pellets and analyzed by RT-PCR using primers for CK-20. In the group of 22 patients with metastatic colon carcinoma, 14 were found to be CK-20 positive (sensitivity of 63.6% and specificity of 92.3%), 22 of the 28 pancreatic carcinoma patients showed positive CK-20 expression, and 12 of 18 patients with gastric carcinoma showed positive CK-20 expression. All patients with metastatic lung carcinoma except 1 were negative (12 of 13 patients), and 12 of 13 patients with colonic carcinoma with no known metastases also were negative. Negative CK-20 results were obtained in all 22 patients with no known malignant diseases. The results of the current study indicate that because of its high sensitivity, RT-PCR of CK-20 is a potential biomarker for detecting metastases in blood samples from patients with carcinoma of the colon, stomach, and pancreas.