Expressions of Mel-18 and Bmi-1 in esophageal squamous cell carcinoma and their clinical significance

Abstract

Objective To analyze the expression levels and clinicopathological significances of Mel-18 and Bmi-1 in esophageal squamous cell carcinoma (ESCC) tissues and paired normal mucosal tissues. Methods The expression levels of Mel-18 and Bmi-1 were measured by real-time PCR and Western blot in ESCC tissues and pericarcinous tissues from 29 patients with ESCC. ESCC tissues and pericarcionous tissues from 60 ESCC patients in chip library were collected too. The expressions of Mel-18 and Bmi-1 protein in 89 ESCC specimens were analyzed by immunohistochemistry. The relationship between Mel-18 and Bmi-1 expressions and the clinicopathological parameters of ESCC were analyzed. Results The real-time PCR showed that the negative expression rate of Mel-18 mRNA was 55.17% (16/29) and the positive expression rate of Bmi-1 mRNA was 62.07% (18/29) in ESCC tissue. Western blot indicated that the level of Mel-18 protein was significantly lower (0.724±0.095 vs. 0.899±0.089, t=2.319, P=0.028), while the level of Bmi-1 was significantly higher (0.980±0.068 vs. 0.729±0.066, t=2.863, P=0.008) in ESCC tissues than that in pericarcinous tissues. The immunohistochemistry showed that the negative expression rate of Mel-18 protein [66.3% (59/89) vs. 31.5% (28/89), χ2=21.606, P<0.05] and the positive expression rate of Bmi-1 [74.2% (66/89) vs. 30.3% (27/89), χ2=34.249, P<0.05] in ESCC tissues were significantly higher than those in pericarcinous tissues. The Mel-18 expression was correlated with clinical stage (χ2=8.003, P=0.004), depth of invasion (χ2=17.094, P=0.001) and lymph node metastasis (χ2=5.156, P=0.026). The Bmi-1 expression has a correlation with the differentiation degree (χ2=14.625, P=0.001), clinical stage (χ2=7.863, P=0.005) and lymph node metastasis (χ2=5.771, P=0.005). In addition, there were negative correlations between Mel-18 and Bmi-1 in ESCC according to results of real-time PCR and immunohistochemistry (r=-0.592, P=0.001; r=-0.285, P=0.007). Conclusions The expression level of Mel-18 was significantly lower, and the expression level of Bmi-1 was significantly higher in ESCC tissues compared with those in para-carcinoma tissues. Mel-18 and Bmi-1 may be the new biomarkers for diagnosis and prognosis of ESCC. Key words: Esophageal neoplasms; Carcinoma, squamous cell; Mel-18; Bmi-1