Detection of circulating tumor cells by nested RT-PCR targeting EGFR/CEA/CK20mRNAs in colorectal carcinoma patients

Background: EGFR is involved in the epidermal growth factors pathway that regulates cellular processes and is associated with the development of many types of cancer including colorectal cancer. Molecular methods with high sensitivity such as nested polymerase chain reaction (PCR) based assays have been used to search for tumor cell specific markers. This study aimed to detect the circulating EGFRmRNA expressing tumor cells and its diagnostic value in colorectal cancer compared with that of known markers of circulating cancer cells CEA and CK20.Subjects and methods: This study included 36 patients diagnosed as having colon cancer of different stages and 18 matched healthy controls. The staging was carried out according to the TNM classification.We used nested RT-PCR-based reverse transcription PCR assay for the detection of circulating cancer cells in the peripheral blood.Results: The blood samples from the colon cancer patients showed detection of EGFR in 15/36 patients (41.7%); CEAmRNA in 22/36 patients (61.1%) and CK20mRNA in 24/36 patients (66.7%). No evidence of EGFR mRNA expression in any of the samples used as controls. 3/18(16.7%) and 4/18 (22.2%) of healthy controls gave a positive result of CEA/CK20mRNAs. There was a statistically significant difference in the prevalence of EGFR/CEA and CK20mRNAs expression between the early disease group (stage I and II) and the advanced disease group (stage IIIand IV) (P < 0.01). Colon cancer patients with a high level of serum CEA exhibited detectable concentrations of EGFR and CEA and CK20mRNAs more often than those with a low serum CEA level, there is significant difference (P < 0.01).Conclusion: EGFR assay might represent a suitable marker for detection of circulating tumor cells in colon cancer patients. CEA and CK20mRNAs are significantly more frequently detected in colon cancer patients than in healthy controls supports the hypothesis that they are promising complementary markers for CRC diagnosis. The assessment of multiple molecular tumor markers improved the sensitivity in detecting circulating tumor cells but due to limited specificity; identification and validation of genes and proteins implicated in metastatic processes need to be furtherinvestigated