The relationship between epidermal growth factor receptor (EGFR) mRNA levels and protein expression in primary colorectal cancer and corresponding liver metastases

Abstract

15021 Background: As it has been well known that epidermal growth factor receptor (EGFR) is strongly related to tumor proliferation and metastasis, several EGFR-targeted drugs have been developed recently. It has been reported that EGFR mRNA levels are associated with response probability in patients treated with EGFR-targeted drugs. We had reported that EGFR mRNA levels in primary colorectal cancer (CRC) are correlated with those in corresponding liver metastases. In this study, our aim was to determine how EGFR mRNA levels are associated with protein expression levels evaluated by immunohistochemistry, and whether immunohistochemical expression in primary CRC correlate with those in liver metastases, as well as mRNA expression. Methods: Thirty-two pairs of primary CRC and corresponding liver metastases were analyzed. Formalin-fixed, paraffin-embedded tumor specimens were dissected using laser-captured microdissection and EGFR mRNA expression levels were quantified by real-time RT-PCR. Same samples were also evaluated EGFR immunohistochemistry. Results: There was a significant correlation for EGFR mRNA expression between primary cancer and corresponding liver metastases (rs=0.78, p<0.0001). In protein levels, 21 of 25 patients with negative expression in primary cancer showed negative in liver metastases, and 4 out of 7 with positive in primary cancer also showed positive in liver metastases (p=0.046, Fisher’s Exact Test). When protein expression and mRNA levels were compared in liver metastases, the patients with positive protein expression showed significantly higher mRNA levels than those with negative protein expression. However no differences in mRNA levels were observed between positive and negative protein expressions in primary CRC. Conclusions: EGFR protein expression showed similar results with mRNA levels in liver metastases, though discrepancy was observed in primary CRC. Author Disclosure Employment or Leadership Consultant or Advisory Role Stock Ownership Honoraria Research Expert Testimony Other Remuneration Response Genetics Inc.