Association Between Bmi1 And Clinicopathologic Status Of Esophageal Squamous Cell Carcinoma

AIM To investigate the expression and clinicopathological roles of Bmi1 in esophageal squamous cell carcinoma (ESCC) tissue, and its relationship to the prognosis of the patients.METHODS Quantitative real-time polymerase chain reaction(PCR) and immunohistochemical staining for Bmi1 were performed in cancerous and adjacent non-cancerous paraffin-embedded esophageal specimens, and statistical analysis were made between the Bmi1 expression and clinicopathological parameters as well as prognosis of patients.RESULTS The Bmi1 expression level was inaffected by gender and age(p>0.05). The level of Bmi1 mRNA in ESCC was significantly higher than that in the adjacent non-cancerous tissues(2.181±2.158 vs 0.931±0.894, p=0.0152), and its over- expression was aggressively associated with lymph node metastasis (3.580±2.487 vs1.703±0.758, p=0.0003), poorer cell differentiation(p=0.0000) and advanced pathological stage(3.827±2.673 vs 1.590±0.735, p =0.0001). The patients were divided into the high-expression and the low-expression groups based on the median expression level of Bmi1 mRNA, a shorter overall survival time in the former group was observed(p=0.0356). Immunohistochemical staining for Bmi1 oncoprotein showed diffusely positive, focally positive and negative expression in 44, 16 and 10 of 70 ESCC cases, respectively, compared with three, two and five of 10 adjacent non-cancerous cases,the oncoprotein was overexpressed in the cancerous tissues(p=0.027). The positive rate of the oncoprotein in samples of histological grade Ⅲwas higher than that of gradeⅡ(p=0.031), but its expression had no relation to the lymph node metastasis and pathological staging. There was no statistical difference between the expression of Bmi1 oncoprotein and the 5-year survival rate(p=0.1704). In addition, in 70 ESCC samples, Bmi1 showed high intense expression in the cytoplasm and less or even no expression at the nucleus.CONCLUSIONS Bmi1 was overexpressed in ESCC. Increased Bmi1 mRNA expression was significantly associated with ESCC progression and cumulative survival. The oncoprotein was largely distributed in the cytoplasm of tumor cells while less or even no in the nucleus,and its expression was related to poorer cell differentiation but lymph node metastasis, pathological stage and prognosis.