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HER2 Heterogeneity in Gastric Cancer: A Comparative Study, Using Two Commercial Antibodies
Catalin Bogdan Satala1,2, Ioan Jung1, Raluca Ioana Stefan-van Staden3
1Department of Pathology, George Emil Palade University of Medicine, Pharmacy, Sciences and Technology, Targu-Mures, Romania.
Background:
Although amplification of the gene encoding human epidermal growth factor receptor 2 (HER2) is used as an indicator for response to trastuzumab, the reported response rate is low, and few patients with gastric cancer (GC) benefit from this individualized therapy. The aim of this study was to examine the expression of c-erbB-2 oncoprotein (HER2), in GC samples, using two commercial immunohistochemical (IHC) antibodies, and to validate the results by checking HER2 gene amplification by fluorescence in situ hybridization (FISH).
Methods:
We assessed the IHC expression of HER2 using the polyclonal antibody from Dako and CB11 clone from Leica, in 93 consecutive cases of GC samples. In all of the cases, FISH analysis was also performed using the BOND-MAX platform.
Results:
No significant difference was observed between the two HER2 antibodies. Of the 93 cases, 22.58% demonstrated at least focal and 1+ HER2 positivity. Seven cases (7.53%) exhibited 3+ expression, and another 7 carcinomas (7.53%) were equivocal (2+). HER2 amplification was seen in 11 cases (11.83%), 10 of which were differentiated adenocarcinomas. In 5 of the cases, 2-5 sections were examined, which proved the extremely high intratumorally/intraglandular heterogeneity. FISH heterogeneity was higher in cases with only 2+ positivity on IHC assessment, compared with those showing at least one small focus of 3+ overexpression. HER2 amplification proved to be an independent negative prognostic factor.
Conclusions:
Due to the highly heterogeneous aspect of GC, at least 3-4 slides should be assessed by IHC, before considering a tumor to be HER2-negative. In cases with small 3+ foci representing less than 5% of tumor and in equivocal (2+) cases, FISH analysis remains the gold standard method.
Insights
Gastric cancer (GC) exhibits high human epidermal growth factor receptor 2 (HER2) heterogeneity. Assessing multiple slides with immunohistochemistry (IHC) and using fluorescence in situ hybridization (FISH) for equivocal cases improves HER2 assessment in GC.
Area of Science:
- Oncology
- Gastroenterology
- Molecular Diagnostics
Background:
- Human epidermal growth factor receptor 2 (HER2) amplification guides trastuzumab therapy in gastric cancer (GC).
- Current HER2 assessment methods yield low response rates, indicating a need for improved diagnostic strategies.
- The study investigates HER2 expression and amplification in GC to refine diagnostic accuracy.
Purpose of the Study:
- To evaluate HER2 oncoprotein expression using two distinct immunohistochemical (IHC) antibodies in GC samples.
- To validate IHC findings by assessing HER2 gene amplification via fluorescence in situ hybridization (FISH).
- To analyze the prognostic significance of HER2 amplification in gastric cancer.
Main Methods:
- Analyzed 93 consecutive GC samples for HER2 IHC expression using Dako polyclonal and Leica CB11 antibodies.
- Performed FISH analysis on all samples using the BOND-MAX platform to detect HER2 gene amplification.
- Examined 2-5 tissue sections per case to assess intratumoral heterogeneity.
Main Results:
- No significant difference was found between the two HER2 antibodies.
- HER2 positivity (1+) was observed in 22.58% of cases; 7.53% showed 3+ expression, and 7.53% were equivocal (2+).
- HER2 amplification occurred in 11.83% of cases, predominantly in differentiated adenocarcinomas, and was an independent negative prognostic factor.
Conclusions:
- Gastric cancer's high heterogeneity necessitates assessing 3-4 slides by IHC to reliably determine HER2 status.
- FISH analysis is the gold standard for equivocal (2+) cases and those with small ( <5%) 3+ foci.
- Accurate HER2 assessment is crucial for effective targeted therapy in gastric cancer.
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