MDM2 and meningioma: In addition, accumulating evidences indicate that hypermethylation-associated loss of function of RB [8, 58], overexpression of the MDM2 gene/protein [25, 26] and loss of expression of MEG3 (an anti-proliferative tumor suppressor that induces activation of p53 by a transcriptional effect) [42] in higher grade meningiomas, might further contribute to dysregulation of both cell cycle-associated pathways during meningioma progression.