Aberrant expression of EZH2 is associated with a poor outcome and P53 alteration in squamous cell carcinoma of the esophagus

Abstract

EZH2 and BMI1 are transcriptional repressors and have been implicated in the progression of human cancers. Squamous cell carcinoma of the esophagus (ESCC) is one of the most aggressive carcinomas in the gastrointestinal tract and generally has an unfavorable outcome. In the present study, we immunohistochemically investigated the expression of EZH2 and BMI1 in 136 surgically resected ESCCs and adjacent epithelium. We also analyzed associations between aberrant expression of EZH2 and BMI1, and both clinicopathological findings and outcome. MYC, RB, and P53 expression was examined in selected cases and analyzed in relation to EZH2 expression. Mutations in the P53 gene were evaluated by direct sequencing. EZH2 mRNA expression was investigated in ESCC cell lines with and without P53 transcriptional activity. The results showed that EZH2 protein and BMI1 protein were upregulated in ESCC tissue in comparison with adjacent non-neoplastic epithelium. Aberrant EZH2 and BMI1 protein expression was observed in 19 (14.0%) and 23 (16.9%), respectively, of the 136 ESCCs. Aberrant EZH2 expression was significantly associated with larger size, greater depth of invasion, presence of distant metastasis, and shorter disease-free survival time. Aberrant BMI1 expression was inversely associated with lymph node metastasis and venous invasion, but not associated with survival of the patients. In addition, aberrant EZH2 expression was associated with P53 alteration in ESCC tissue. EZH2 mRNA expression in ESCC cell lines was reduced by activation of P53. In conclusion, P53 alteration may be involved in dysregulated EZH2 expression, and aberrant expression of EZH2 may play a role in ESCC progression.