NDRG1 and meningioma: For this purpose, 44 WHO grade I meningiomas, including 8 showing regrowth after radiosurgery, were analysed for Ki-67 and NDRG4 protein expression, loss of 1p36 and promotor hypermethylation of the genes NDRG1-4, SFRP1, HOXA9 and MGMT.