Application of array CGH in breast cancer oncology :comparison with IHC and FISH

Currently, we have known that about 15%~25% of breast cancer patients have HER2 gene amplification. For these patients, the present study demonstrated that drugs such as Transtuzumab(Herceptin), Lapatinib (Tykerb) can be used to delay the recurrence and progression. Therfore, the detection of HER2 has become a very important test to determine the treatment plan for breast cancer patients.
The most common HER2 gene test is immunohistochemical staining(Immunohistochemistry;IHC), which is faster and cheaper in testing. However, its major disadvantages are that the results are hardly quantified and just determined by the color density, which is judged by the interpreter’s subjective opinions. Another technique is Fluorescent in-situ hybridization(FISH) which is used when the immunohistochemical staining(IHC) revealed equivocal(2+). The method of Fluorescent in-situ hybridization(FISH) is dectecting the ratio of the HER2 gene expression in chromosome 17 over the gene expression in the centromere. However, it is known that FISH will produce false negative in those patients with chromosome 17 polypoidy or fales positve in those patients with a large number of deletion in centromere in chromosome 17. According to breast cancer HER2 gene testing guidelines published by the American Society of Clinical Oncology (ASCO) in 2007, there are about 20% HER2 gene test results may be incorrect. (Wolff AC et al 2007)However ,another reference published in 2009 indicated that the concordance between IHC and FISH has been up to 98%(Middleton LP et al 2009), which is better than the requirements(95%) in the guideline.
In order to understand the role of HER2 gene in chromosome17 , we can utilize the new molecular diagnostic techniques, Array Comparative Genomic Hybridization(aCGH), providing another choice to detect HER2 gene. It can screen the whole genome in the same time. Thus, with the time of personalized medicine comes, gene detection will be the medical trends.
It is significant that the specific gene amplification or deletion in variant tumors is associated with the new drug development and the treatments. As a result, it will be extremely helpful for the cancer researches in the future by the Array Comparative Genomic Hybridization(aCGH).