HER2 amplification and chromosome 17 polysomy status
Current methods to evaluate HER2 amplification in breast tumor samples rely on immunohistochemistry (IHC) to assess HER2 overexpression, which, for equivocal IHC HER2 expression (IHC2+), may be complemented by fluorescence in-situ hybridization (FISH) to detect HER2 gene amplification. These methods are labor-intensive and require a high level of expertise for analysis. Molecular methods may provide simpler, faster and unbiased alternatives.
The present study was conducted using DNA extracted from tumors from 7 patients with breast cancer, provided by Institut Gustave Roussy
(France)§, and results obtained by Crystal Digital PCR were compared to those obtained using standard diagnostic procedure.
Figure 2. Classification of patients 1-7 regarding HER2 amplification using current diagnostic procedure (IHC and FISH) (A), or by Crystal Digital PCR (B).
Results obtained with IHC/FISH and Crystal Digital PCR were in agreement for patients 1-4 samples, deemed positive for HER2 amplification by both methods, as well as for samples from patients 6 and 7 identified as negative for HER2 amplification. Crystal Digital PCR™ additionally identified a case of chromosome 17 polysomy for patient 6. However, whereas HER2 amplification was identified for patient 5 sample using standard diagnostic procedure, Crystal Digital PCR identified the elevated HER2 signal as attributable to chromosome 17 polysomy.
[I] Jacquemier et al. “SISH/CISH or qPCR as alternative techniques to FISH for determination of HER2 amplification status on breast tumors core needle biopsies:a multicenter experience based on 840 cases”. BMC Cancer. 2013 ; 13:351. PMID: 23875536
 Whale et al. “Comparison of microfluidic digital PCR and conventional quantitative PCR for measuring copy number variation”. Nucleic Acids Res. 2012 ;40:11. PMID: 22373922
§ Courtesy of Dr Cécile Jovelet, Translational Research Laboratory, Institut Gustave Roussy, France