2013 Volume 59 Issue 4 Pages 331-339
Objective: In the Vienna classification, esophageal non-invasive neoplasms are classified as low-grade dysplasia (LGD), high-grade dysplasia (HGD), CIS and suspicion of invasive carcinoma. Polycomb group proteins EZH2 and Bmi-1 are involved in the transactivation of p16 INK4a and p53, and have been implicated in the carcinogenesis, progression, and poor prognosis of several cancers;however, their role in early esophageal carcinogenesis has not yet been elucidated. Therefore, in the current study, we examined the expression of EZH2 and Bmi-1 in association with p53 and p16 INK4a during esophageal squamous carcinogenesis. Materials: We used a series of 60 esophageal squamous intraepithelial lesions (58 patients), resected endoscopically or surgically at Juntendo University Hospital between 2007 and 2011. The 58 patients comprised 50 males and 8 females, with a mean age of 67.1 years (range, 51-81 years). According to the Vienna classification, we classified the lesions into LGD (category 3), HGD (category 4.1), and CIS (category 4.2) to identify possible biological differences between these lesions, 14 low-grade dysplasia (LGD), 23 high-grade dysplasia (HGD), and 23 carcinoma in situ (CIS) specimens. Methods: Immunohistochemical analysis was performed on 3-μm sections of formalin-fixed, paraffin-embedded tumor tissues. Monoclonal antibodies used in the present study were against EZH2, Bmi-1, p16 INK4a, p53, and Ki-67. Immunohistochemical results of each protein were scored as immunolabeling scores (ILSs) from 0 to 3 points according to each quarter of occupation of the squamous epithelium, and were analyzed on the basis of the clinicopathologic variables. Results: All of these lesions had male predominance. Tumor size in CIS was significantly larger than that in LGD (p<0.05). ILSs for all proteins but p16 INK4a showed significant stepwise increases from LGD to HGD to CIS (p < 0.05-0.001). Furthermore, the expressions of all proteins but p16 INK4a were positively related to each other. However, 3 lesions of LGD (21%), 8 lesions of HGD (35%), and 6 lesions of CIS (26%) demonstrated p16 INK4a expression, even under the co-expression of EZH2 and Bmi-1. In HGD, high-EZH2 ILS was significantly associated with larger tumor size (p < 0.05). In addition, high-p53 ILS was associated with larger tumor in CIS (p<0.05). Conclusions: This study indicates that the overexpression of polycomb group proteins EZH2 and Bmi-1, along with p53 and Ki-67, but not p16 INK4a, has an important role during the early stages of esophageal squamous carcinogenesis. Interestingly, unlike other malignant tumors, for example, squamous cell lung cancer, cholangiocarcinoma and colorectal cancer, a minor subset of cases of esophageal squamous intraepithelial neoplasia exhibit the p16 expression, even under the coexpression of EZH2 and Bmi-1.
