Detection of Topoisomerase IIα Gene Amplification in Archival Breast Cancer Specimens by Quantitative Real-Time Polymerase Chain Reaction
Author(s):
Maisaa A. Alwohhaib, Salah K. Al-Waheeb and Ghaneema E. Alshammari
Topoisomerase IIα is an important nuclear enzyme involved in cell division. The inhibition of the DNA topoisomerase IIα is achieved by using anthracyclines which are powerful drugs for the treatment of breast cancer. The sensitivity of topo II inhibitors such as anthracyclines is dependent on the expression level of topo IIα in target cancer cells. Accordingly accurate determination of the amplification level of topo IIα in breast cancer patient is crucial to identify the patients who will benefit from the treatment. The aim of this study focusses on the detection of topo IIα gene amplification status in invasive breast cancer compared to the normal values and its association with the HER2 gene status.
Forty-four (44) FFPE tissue samples were examined for topo IIα and HER2 genes quantity by qPCR. Statistical analysis using one sample t-test to determine the significant difference between the mean of the relative fold values of each gene from the normal sample value. Pearson correlation test was performed using Excel to determine the relation between the topo IIα Ct values and the HER2 Ct values.
Out of 44 patients 21 showed down regulation of the topo IIα gene (48%) and 23 showed up-regulation (52%). Only 2 samples out of 44 showed down regulation of the HER2 gene (0.05%) and 42 showed up-regulation (95%%). The statistical t-test performed on the relative values of the topo IIα gene and the HER2 gene separately showed a significant difference from the normal sample relative fold value. A positive correlation was found between the topo IIα gene and the HER2 gene relative values (r = 0.61522262 and p-value = 0.00000838321).
This study confirmed the association of the topo IIα gene abnormal fold values with HER2 gene amplification and its association with invasive histological types of breast cancer. Cut-off values of the amplification of the key genes such as HER2 and topo IIα should be established. The results of this study may add to the information required to understand the functional roles of these genes in the diagnosis of breast cancer and the use of target therapy.