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Hellenic Archives of Pathology, Volume 20, Issues 1-3, 2006
Comparative study of EGFR protein
and gene expression using IHC
and FISH in colon carcinomas
Bobos M., Kostopoulos I., Papadimitriou S.C., Vrettou E.
Department of Pathology, Aristotle University Medical School, Thessaloniki, Greece
Introduction-Aim: Colorectal cancer is one of the leading causes of cancer related-deaths worldwide. EGFR glycoprotein is frequently expressed in colorectal carcinomas and recent research is focused on its prognostic and therapeutic implications. There are few data on the correlation of EGFR protein expression and gene status in colorectal carcinomas. In the present study we evaluated the correlation of EGFR protein expression with EGFR gene numerical aberrations in colorectal carcinomas.
Materials and Methods: We investigated 61 colorectal carcinomas for EGFR expression with immunohistochemistry and EGFR gene and chromosome 7 status using EGFR Spectrum Orange/CEP7 Spectrum Green probes by fluorescent in situ hybridization (FISH).
Results: EGFR protein expression was detected in 33/61 cases (54 %) and overexpression (2+, 3+) in 11/33 cases. EGFR/CEP7 ratio ranged from 0.86-8.11 with a mean of 1.17. High level amplification (EGFR/CEP7 ratio >2) of EGFR gene was observed in one IHC EGFR negative case, whereas low level amplification (EGFR/CEP7 ratio >1.3-2) in 2 cases (EGFR 1+, EGFR-). Increased EGFR gene signals were found in 24/61 (39%) cases, while gene indeterminate or definitive loss was not detected. CEP7 gain was calculated in 13 cases, indeterminate loss in 4 cases and definitive loss in 1 case. Polyploidy and polysomy were observed in 10 and 4 cases, respectively. EGFR gene amplification was found only in low-grade carcinomas with high pathologic stage (C2) and advanced clinical stage (TNM stage III). EGFR gene copy gain was detected in low and high grade tumors of early and advanced clinical stage (II-IV).
Conclusions: EGFR immunohistochemical expression was independent of gene status. The detected EGFR gene amplification in negative for protein expression cases suggests that FISH method may be useful in cases where the production of EGFR protein is absent.
Key words: Colon carcinoma, EGFR, FISH, immunohistochemistry.
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