Chromogenic in situ Hybridization Analysis of EGFR Gene Copies in Colon Adenocarcinoma Based on Intra-Operative Imprints and Tissue Microarrays
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Evangelos Tsiambas1,7*, Dimitrios N Rigopoulos2*, Christos Kravvaritis3, Andreas C Lazaris4, Nikolaos Kavantzas4, Athanasios Niotis5, Theodoros H Niotis5, Dimitrios Tsounis6, Andreas Karameris7, Efstratios Patsouris4
1) Medical School, University of Athens;
2) Dept of Internal Medicine, 401 GA Hospital, Athens;
3) Dept of Forensic Services, Medical School, University of Thessaly, Larisa;
4) Dept of Pathology, Medical School, National and Kapodistrian University, Athens;
5) Dept of Surgery, 417 VA Hospital (NIMTS), Athens;
6) Dept of Gastroenterology, 251 AF Hospital, Athens;
7) Dept of Pathology, 417 VA Hospital, Athens, Greece.
*Authors equally contributed
Abstract
Background: Although Epidermal Growth Factor Receptor (EGFR) over expression is a frequent event in colon adenocarcinoma (CA), identification of EGFR gene deregulation mechanisms - combined to k-ras mutations - remains the basic criterion for rational application of anti-EGFR targeted therapeutic strategies.
Aim: To detect EGFR gene numerical alterations in CA based on a combination of intra-operative imprints and the corresponding tissue microarrays.
Methods: 60 paraffin embedded primary CAs were cored at 1.5 mm diameter and transferred to the final microarray block. Chromogenic in situ hybridization (CISH) was performed using EGFR gene and chromosome 7 centromeric probes in the tissue microarray and also in the corresponding intra-operative imprints.
Results: CISH analysis detected 4/60 (6.6%) EGFR gene amplified cases, whereas chromosome 7 aneuploidy was identified in 11/60 (18.3%) cases. Significant association was established by correlating stage to chromosome 7 (p=0.024). A high value of concordance (kappa=1) was observed comparing overall gene status based on the tissue cores and the corresponding imprints, whereas EGFR/CEN 7 copies were more numerous in imprints than in tissue microarrays (p=0.03).
Conclusions: Intra-operative imprint cytology provides accurate and fast results in detecting EGFR gene/chromosome 7 centromeric signals by CISH due to the nuclear integrity and monolayer formation of the examined cells. Based on this molecular analysis, gastroenterologists and oncologists can handle those patients in a rational way regarding targeted therapies. Furthermore, chromosome 7 aneuploidy is associated with a more advanced stage in CA.
Key words
Colon adenocarcinoma - gene - tissue microarrays - imprints.
