Topoisomerase IIalpha and HER2/neu gene alterations and their correlation in pancreatic ductal adenocarcinomas

Abstract

To investigate the changes of topoisomerase IIalpha (TOP2A) and HER2/neu genes in pancreatic ductal adenocarcinomas of Chinese patients, and to determine their roles during carcinogenesis and tumor progression. Expressions of TOP2A and HER2/neu proteins were detected by using immunohistochemistry, while gene amplifications of TOP2A and HER2/neu were assessed by using multi-color fluorescence in situ hybridization (FISH). All the samples were of paraffin embedded and 10% formalin fixed tissue, including 26 cases of pancreatic ductal adenocarcinomas with adjacent non-neoplastic pancreatic tissues, 10 cases of chronic panreatitis, and 10 cases of normal pancreas. The correlation between TOP2A and HER2/neu gene status was analyzed. By immunohistochemistry, the nuclear positive index of TOP2A in pancreatic ductal adenocarcinomas varied from 0.5% to 70%, and the positive rate of HER2/neu in pancreatic ductal adenocarcinomas was 46.2% (12/26). By FISH, 9/10 TOP2A amplified adenocarcinomas showed TOP2A and HER2/neu gene coamplification, while one case with HER2/neu gene amplification adenocarcinoma showed no TOP2A amplification. No expression of TOP2A, HER2/neu proteins and no amplification of TOP2A and HER2/neu gene were detected in adjacent non-neoplastic pancreatic tissues, chronic pancreatitis tissues and normal pancreas. No relationship was found between protein expression and gene amplification of TOP2A and HER2/neu (P > 0.05). TOP2A gene amplification was significantly correlated with HER2/neu gene amplification (P < 0.01). Protein expression of TOP2A and HER2/neu are not associated with the gene amplification. There is a significant correlation between TOP2A amplification and HER2/neu gene amplification. Co-amplification of TOP2A and HER2/neu may play an important role in the carcinogenesis and progression of pancreatic carcinoma. Evaluation of the status of TOP2A and HER2/neu may be helpful to achieve target therapy of pancreatic carcinoma.