The Influence of Distinct Regulatory miRNAs of the p15/p16/RB1/E2F Pathway on the Clinical Progression of Glioblastoma Multiforme.

Objective: The microRNAs (miRNAs) -26a, -24, and -21 have been reported as regulators of the P15/P16/RB1/E2F pathway, which plays a major role in glioblastoma multiforme (GBM) progression. In the present study, their predictive marker for the progression of GBMs is evaluated and described.

Methods: The expression of miRNA-21, -24, and -26a was analyzed as fold change (FC) in tumor specimens of 104 patients with GBM and 8 specimen of non-neoplastic brain tissue as control group. The results were referred to the individual clinical data sets and evaluated statistically.

Results: The FC of miRNA-21, -24, and -26a was 1.51 ± 1.35, 0.75 ± 0.67, and 0.39 ± 0.24 in the tumor samples. Within the control group, FC of miRNA-21, -24, and -26a was 0.31 ± 0.51, 0.66 ± 0.33, and 0.18 ± 0.11, respectively. MiRNA-26a and -21 were significantly overexpressed in GBM samples compared with healthy brain tissue (miRNA-21: P < 0.001; miRNA-26a: P = 0.011). High expression ofmiRNA-24 trended for a prolonged overall survival (P = 0.07). Patients with high miRNA-26a expression showed a significantly prolonged progression-free survival (hazard ratio 0.21; 95% confidence interval 0.09-0.51], P < 0.001) and overall survival (hazard ratio 0.3; 95% confidence interval 0.136-0.682], P = 0.003). The effect of miRNA-26a was mediated via regulation of mRNA of RB1. There was a significant inverse correlation between mRNA-26a and mRNA expression of RB1.

Conclusions: The expression levels of miRNA-26a and -24 turned out to be promising predictors of further clinical course in patients with GBM multiforme.