Epidermal growth factor receptor and epidermal growth factor receptor variant III gene expression in metastatic colorectal cancer

Purpose: The epidermal growth factor receptor (EGFR) variant type III (variously called EGFRvIII, de2-7 EGFR, or Delta EGFR) has an in-frame deletion of the extracellular domain and is found in numerous types of human tumors. Because EGFRvIII has been reported to be tumor specific and has oncogenic potential, it is being investigated as a potential therapeutic target, but to our knowledge, there is only 1 previous report about EGFRvIII by immunohistochemistry in colorectal cancer. Our aim was to indicate the frequency of gene expressions of EGFRvIII and EGFR in metastatic colorectal cancer (mCRC). Patients and Methods: Forty-five patients with mCRC who received the chemotherapy for metastatic disease were analyzed for the EGFRvIII variant. Paraffin-embedded tumor tissues were dissected using laser-captured microdissection and analyzed for the EGFR and EGFRvIII messenger RNA expression using a quantitative real-time reverse-transcriptase polymerase chain reaction method. Gene expression values (relative messenger RNA levels) are expressed as ratios (differences from the cycle threshold values) between the target gene and internal reference gene (beta-actin). Twenty-five women and 20 men with a median age of 55 years (range, 25-76 years) were included in this study. Results: We did not find any expression of EGFRvIII in these 45 patients except for control cell lines as U87.EGFRvIII. However, EGFR gene expression was found in 43 of 45 (95.6%) with a range of 0.38-2.83. Conclusion: Our results demonstrate that the expression of EGFRvIII is rare, but most colon cancer demonstrates EGFR gene expression. We conclude that EGFRvIII does not play an important role in mCRC.