Y. Hirose1, M. Nagahashi1, H. Ishikawa1, K. Yuza1, K. Miura1, H. Ichikawa1, Y. Shimada1, H. Kameyama1, J. Sakata1, T. Kobayashi1, T. Wakai1 1Niigata University Graduate School Of Medical And Dental Sciences,Division Of Digestive And General Surgery,Niigata, NIIGATA, Japan
Introduction: Preoperative discrimination between benign and malignant biliary structures based on small biopsy specimens is difficult. 5.2 to 24.5 percent of biliary structures resected as malignant proved to be benign after histological examination of the surgical specimens. Recent studies have demonstrated that γH2AX, a sensitive marker for DNA double-strand breaks (DSBs), are detected at higher levels in cancer than in precancerous or normal lesions. However, γH2AX expression in biopsy specimens of biliary structures have not been examined. The aim of this study was to determine the usefulness of γH2AX expression in biopsy specimens to discriminate between benign and malignant tissues.
Methods: We examined biopsy specimens of six extrahepatic bile duct cancer tissues, seven inflammatory tissues of the bile duct, and five normal bile duct tissues. The diagnoses of these samples were confirmed by postoperative histological examination or clinical follow-up. Immunohistochemical examination of γH2AX was performed for each biopsy specimen. The nuclear staining pattern was classified into two patterns: focal staining pattern, characterized by focus formation in the nucleus; and diffuse staining pattern, characterized by peripheral– or pan-nuclear staining. The labeling index (LI) of γH2AX-positive cells was calculated for each staining pattern. Continuous variables were compared using the Mann-Whitney U test or the Kruskal-Wallis test. All tests were two-tailed, and P-values less than 0.05 were considered statistically significant.
Results:Kruskal-Wallis test revealed that the LI of γH2AX-positive cells with focal staining was significantly different between cancerous, inflamed, and normal biopsy tissues . Moreover, Dunn's multiple comparison test revealed that there was a significant difference of LI of γH2AX-positive cells with focal staining between cancer tissues and normal tissues (P < 0.01). On the other hand, there was no significant difference in the LI of γH2AX-positive cells with diffuse staining among the three different types of tissues (Kruskal-Wallis test; P > 0.05).
Conclusion:To our knowledge, this is the first study to examine the LI of γH2AX-positive cells in human biliary biopsy samples. The LI of γH2AX-positive cells with focal staining might be a useful biomarker to discriminate between benign and malignant biliary tissues.