Prognostic value of microRNA-125a expression status in molecular groups of pediatric medulloblastoma.

PURPOSE: Medulloblastoma (MB) is the most common malignant pediatric brain tumor. Current treatment allows decent survival rates but often with life-long morbidity. Molecular classification provides a base for novel therapeutic approaches. However, these groups are heterogeneous. MicroRNA-125a has a tumor suppressor function. It is downregulated in several tumors. The expression of microRNA-125a in MB patients remains unclear. Therefore, this study was designed to evaluate the expression of microRNA-125a in molecular groups of pediatric MB patients in Egyptian population and its clinical significance.

METHODS: Formalin-fixed, paraffin-embedded tissue blocks from 50 pediatric MB patients were retrospectively collected. Immunohistochemistry for β-catenin, GAB1, YAP1, and p53 was done for molecular classification. MicroRNA-125a expression analysis was done using qRT-PCR. Follow-up data were obtained from patients' records.

RESULTS: MicroRNA-125a expression was significantly lower in MB patients showing large cell/anaplastic (LC/A) histology and in the non-WNT/non-SHH group. Lower levels of microRNA-125a showed a tendency toward poor survival rates; however, difference was not significant. Infants and larger preoperative tumor size were significantly associated with lower survival rates. On a multivariate analysis, preoperative tumor size was an independent prognostic factor.

CONCLUSION: MicroRNA-125a expression was significantly lower in categories of pediatric MB patients with worse prognosis namely LC/A histology and the non-WNT/non-SHH group suggesting a pathogenetic role. MicroRNA-125a expression could represent a promising prognostic factor and a potential therapeutic target in the non-WNT/non-SHH group which represents the most common and the most heterogeneous group of pediatric MBs coupled with the highest rates of disseminated disease. Preoperative tumor size represents an independent prognostic factor.