Amplification of the HER-2/neu Oncogene and Topoisomerase II-alpha by Chromogenic in Situ Hybridization in Breast Cancer

Kim, Ho Sung; Kim, Beom Gyu; Cha, Seong Jae; Lee, Tae Jin; Park, Sung Jun; Lim, Hyun Muck; Park, Sung Il

Abstract

PURPOSE: HER-2/neu is the most frequently amplified oncogene in breast cancer. Topoisomerase II-alpha is a key enzyme in DNA replication and it is a molecular target for many anti-cancer drugs that are called topo II inhibitors; in addition, it is a new marker of proliferation. Because of the physical proximity of the ER-2/neu and topoisomerase II-alpha genes, co-amplification of the HER-2/neu and topoisomerase II-alpha may be important determinates of the response to chemotherapy for advanced breast cancer patients.
METHODS
We studied the correlation of gene amplification of HER-2/neu and topoisomerase II-alpha by chromogenic in situ hybridization (CISH) in 43 infiltrating duct carcinomas of the breast. The over-expression of HER-2/neu protein and the staining index for the proliferation marker of topoisomerase II-alpha were examined immunohistochemically. The correlations between the status of HER-2/neu and topoisomerase II-alpha and the other clinicopathologic variables such as tumor size, lymph node metastasis, TNM stage, histologic grade, nuclear grade, and the estrogen receptor and progesteron receptor were investigated.
RESULTS
Of the 43 infiltrating ductal carcinomas, the amplifications of HER-2/neu and topoisomerase II-alpha by CISH were observed in 8 cases (18.6%) and 14 cases (32.6%), respectively. Amplification of HER-2/neu showed the statistically significant correlations with tumor size, histologic grade and the topoisomerase II-alpha staining index. Amplification of topoisomerase II-alpha showed statistically significant correlations with axillary lymph node metastasis, the stage, the nuclear grade and the estrogen receptor status.
CONCLUSION
These data suggest that amplification of HER-2/neu oncogene and topoisomerase II-alpha by CISH may be valuable for determining the response to chemotherapy, and detection of HER-2/neu and topoisomerase II-alpha in tumor sections may have prognostic value in human breast cancer.