HOXA9 and meningioma: Epigenetic alterations are frequently observed in meningiomas and involve hypermethylation of the tumor suppressor genes p73 in grade I meningiomas and TIMP3, GSTP1, MEG3, HOXA6, HOXA9, PENK, WNK2, and UPK3A with an increasing frequency following grade progression of the tumors [214].