Quantitative analysis of TEM-8 and CEA tumor markers indicating free tumor cells in the peripheral blood of colorectal cancer patients

Abstract

Colorectal cancer (CRC) remains the third most common cancer in the world. Approximately in 50 percent of patients, metastatic disease is a major cause of death. Therefore, early diagnosis of CRC is crucial for a successful outcome. For the detection of circulating cancer cells, this study applied a sensitive method that employed specific tumor markers for early detection. A total of 80 blood samples from 40 CRC patients and 40 age-matched healthy controls were collected for the study. The circulating mRNA levels of two CRC tumor markers, tumor endothelial marker 8 (TEM-8) and carcinoembryogenic antigen (CEA) were evaluated using an absolute quantitative real-time PCR assay in a Stratagene Mx-3000P real-time PCR system. GAPDH was used as the endogenous control. TEM-8 and CEA were primarily detected more in the CRC patients rather than in the controls: 22/40 vs 9/40, p=0.009 and 30/40 vs 11/40, p=0.00054, respectively. In the CRC patients, the mRNA level of these markers was significantly higher in comparison to the normal controls (p=0.018 and 0.01). The overall sensitivity of this panel was 65% with a specificity of 75%. Statistical analysis for demographic variants did not reach significant values. TEM-8 and CEA markers were detected more frequently and in significantly higher levels in the blood samples of patients compared with samples from age-matched healthy controls. The copy number of CEA and TEM-8 mRNA, as detected by a real-time quantitative PCR, appears to be a promising marker for evaluating the risk of tumor spread.