γ-Glutamylcyclotransferase as a novel immunohistochemical biomarker for the malignancy of esophageal squamous tumors.

Recently, overexpression of γ-glutamylcyclotransferase (GGCT) has been reported in various cancer tissues suggesting that it has significant potential as a diagnostic marker. The aim of this study was to examine the suitability of GGCT for the detection of high-risk lesions at an early stage of esophageal squamous cell carcinoma (ESCC). A total of 200 lesions, including 120 invasive ESCC, 80 esophageal squamous intraepithelial neoplasia consisting of 40 low-grade intraepithelial neoplasia (LGIEN) and 40 high-grade intraepithelial neoplasia (HGIEN), as well as 20 confounding lesions, were examined by immunohistochemical (IHC) staining for GGCT. IHC staining for Ki-67 and p53 was also performed in esophageal squamous intraepithelial neoplasia to compare the diagnostic power of GGCT. Increased expression of GGCT was common in invasive ESCC and HGIEN (87.5% and 85.0%, respectively), but was much less frequently observed in LGIEN (17.5%). GGCT expression significantly correlated with the presence of lymph node metastasis and the degree of differentiation. In the differential diagnosis of LGIEN and HGIEN, GGCT possessed both high sensitivity and high specificity, while Ki-67 and p53 only possessed either high sensitivity or high specificity. Additionally, GGCT expression was higher in 7 out of 8 ESCC cell lines (KYSE series) than in a normal esophageal squamous cell line (Het-1A). The expression levels strongly correlated with enzymatic activity (r=.92; P<.001). These results indicate that overexpressed GGCT retains its enzymatic activity and can become a valuable biomarker for the diagnosis of HGIEN that is likely to progress to subepithelial invasion.