Combined aberrant expression of Bmi1 and EZH2 is predictive of poor prognosis in glioma patients

Background and objectivesBmi1 and EZH2 are involved in tumorigenesis of gliomas. However, clinicopathologic significance of their expression in gliomas is unknown; especially, the prognostic value of combined expression of Bmi1 and EZH2 has not been explored.MethodsBmi1 and EZH2 expression in human gliomas and nonneoplastic brain tissues was measured by immunohistochemistry.ResultsBoth Bmi1 and EZH2 expressions in glioma tissues were significantly higher than those in corresponding nonneoplastic brain tissues (both P < 0.001). Additionally, the upregulations of Bmi1 and EZH2 proteins were both significantly associated with advanced WHO grades (both P < 0.001) and low KPS (P = 0.008 and 0.01, respectively). Moreover, the overall survival of patients with high Bmi1 protein expression (P = 0.006) or high EZH2 protein expression (P = 0.01) was obviously lower than those with low expressions. More interestingly, glioma patients with combined overexpression of Bmi1 and EZH2 proteins had the shortest overall survival (P < 0.001). Furthermore, multivariate analysis showed that Bmi1n expression (P = 0.02), EZH2 expression (P = 0.03), and combined expression of Bmi1 and EZH2 (P = 0.008), were all independent prognostic factors for overall survival in glioma patients.ConclusionsOur data suggest for the first time that the combination of Bmi1 and EZH2 overexpression may be a highly sensitive marker for the prognosis in glioma patients.