This study suggests association between expression changes in several DSB repair genes in a common functional pathway in breast cancer and the significant association between abnormal expression of these genes and important clinical prognostic factors.

Background: Amplification of HER2 is seen in 20-30% of breast cancer cases. Measurement of HER2 gene amplification appears to be of vital importance in planning the treatment schedule for patients with breast carcinoma. The aim of our study was to evaluate HER2 amplification status in malignant and benign breast tumors by differential PCR (dPCR). Materials and Methods:The genomic DNA was extracted using the phenol/chloroform extraction procedure from 76 different breast tissues. Differential PCR was performed using the DNA samples isolated from fresh and paraffin-embedded breast cancer tissues. The relative copy number ratio of target gene (HER2) to control gene (INF-γ) was measured. dPCR products were then separated by electrophoresis using 2% agarose gel. The intensity of HER2 and INFγ bands were determined for each sample by ImageJ software. Results: According to the ratio between the band intensity of HER2 to INFγ in tumour and also normal samples, 7% and 26% rates of HER2 amplification were observed in benign and malignant samples respectively. The ratio showed a 2-5 fold increase in HER2 gene copy number for tissues with HER2 amplification; whereas, a one-fold increase was found in other samples. Conclusion: Differential PCR provides a relatively rapid and inexpensive technique to assess the HER2 gene amplification, especially alongside immunohistochemistry as a routine assessing method.