Methodologic Evaluation of EGFR Expression in Colorectal Cancer

ABSTRACT

PURPOSE: The epidermal growth factor receptor (EGFR) is a one of the transmembrane receptor proteins that play an important role in initiating tumor cell signaling and growth and is regarded as a promising target for cancer therapy. The EGFR expression rate has been reported to vary according to the detection method. The aims of this study were to evaluate the EGFR expression rate of a colorectal carcinoma by using immunohistochemical staining (IHC) and semiquantitative reverse transcription-polymerase chain reaction (RT-PCR) and to analyze the correlation between these methods. METHODS: EGFR expression was investigated in tissue sections from 33 patients with a colorectal adenocarcinoma by using IHC and semiquantitative RT-PCR. IHC was performed with antibodies in a 140 dilution and a 180 dilution. The results of the three detection methods were compared with one another. RESULTS: The mean age of the patients was 61.9+/-12.2 years, and the male-to-female ratio was 1.21. The EGFR expression rates were 93.9% (31/33) in IHC with a 140 dilution, 87.9% (29/33) in IHC with a 180 dilution, and 66.7% (22/33) in RT-PCR. The result of IHC with a 140 dilution significantly correlated with the result of IHC with a 180 dilution (Pearson correlation 0.684, P<0.01). There was no correlation between semiquantitative RT-PCR and IHC (140 dilution, 180 dilution). CONCLUSIONS: The EGFR expression obtained by using IHC was consistent with different antibody dilutions. The expression rate obtained by using RT-PCR was significantly lower than that obtained by using IHC, and there was no statistical correlation between the expressions of EGFR obtained by using RT-PCR and IHC. A standardization for EGFR detection methods is needed to draw any conclusion concerning their activity in colorectal cancer.