RB1 and neoplasm: Other candidate genes for which different mechanisms of alteration (e.g. epigenetic silencing) have been reported in GBM, include the RBBP5 gene (a member of the RB pathway) amplified at 1q32 [23], the CXCL12 (CXCR4 ligand involved in chemoattraction and tumor invasion) and the HK1(a member of the hexokinase family, known to regulate apoptotic pathways) genes [25].