Abstract

Detection of HER2 gene amplification in formalin-fixed and paraffin-embedded breast cancer tissues by quantitative real time polymerase chain reaction in ER and PR-positive HER2 immunohistochemistry 0 or ≥ 2+ breast cancer

Amplification of the human epidermal growth factor receptor 2 (HER2) genes and overexpression of its gene product, the HER2 protein was found in 20% of breast cancers. Genetic instability and hence aberrant HER2 amplification may be associated with breast cancer progression. HER2 status determination plays an important role in selecting the best treatment options in early and advanced breast cancer. This is a cross-sectional clinical genetic study of breast cancer patients in Kuwait. The aim of this study is to detect HER2 gene amplification in Formalin-Fixed Paraffin Embedded (FFPE) breast cancer tissue samples with IHC 0 or ≥ 2+ and were ER and PR positive.

Quantitative real time Polymerase Chain Reaction (qPCR) was performed on 44 FFPE breast cancer tissue samples with IHC 0 or ≥2+ and were ER and PR positive. DNA was isolated using NucleoSpin^®DNA FFPE XS kit. Real time PCR was carried out using TaqMan™ Fast advanced Master Mix. The beta actin gene was used as a reference gene to the HER2 gene investigated. The 7500 fast real-time PCR system was used.

Samples that were evaluated as HER2 equivocal and were negative by FISH presented high qPCR values of 10 and 28. A sample that was equivocal and then negative by FISH presented a qPCR value of 28 and was from a grade 3 patient. On the contrary, one HER2 equivocal sample by IHC and positive by FISH presented a qPCR value of 16 which was from a grade I patient. Seven samples that were grade I and II were evaluated as HER2 negative by IHC presented high qPCR values of 9, 12,13, and 15.

Conclusion: Quantitative PCR is a molecular method that is more sensitive than FISH or IHC. The screening for the status of the HER2 gene alongside the protein status by IHC provides thorough evaluation especially in the higher grades of breast cancer who might get more accurate evaluation and might benefit from better treatment options.

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