Expression and clinicopathological significance of Mel-18 and Bmi-1 in oesophageal squamous cell carcinoma.

The Polycomb group (PcG) genes are a general class of regulators that are responsible for maintaining homeotic gene expression throughout cell division. PcG expression plays an important role in oncogenesis of several types of human cancer. Mel-18 and Bmi-1 are key PcG proteins. Studies have shown that Mel-18 is a potential tumour suppression and Bmi-1 is overexpressed in several human malignancies. However, the roles of Mel-18 and Bmi-1 in oesophageal squamous cell carcinoma (ESCC) are still unclear. In this study, we analysed the expression levels of Mel-18 and Bmi-1 in 89 oesophageal cancer tissues and paired normal mucosal tissues using immunohistochemistry, Western blotting and quantitative real-time PCR (QRT-PCR) analyses. We found that the expression of Mel-18 in the carcinoma tissues was significantly lower than that in the noncancerous mucosal tissues (P<0.05), and Bmi-1 expression in the carcinoma tissues was significantly higher than that in the noncancerous mucosal tissues (P<0.05). In addition, the expression of Mel-18 was correlated with clinical stage, depth of invasion and lymph node metastasis (P 0.05). Bmi-1 expression was strongly correlated with the degree of differentiation, clinical stage and lymph node metastasis (P 0.05). Moreover, there was a negative correlation between Mel-18 and Bmi-1 expressions in ESCC (P<0.05). Our study suggests that Mel-18 and Bmi-1 may play a crucial role in ESCC. Mel-18 or Bmi-1 may be a potential biomarker for diagnosis and prognosis of ESCC.