PLK4 and glioblastoma: PLK4 overexpression and over-activation have been associated with a number of peripheral adult tumors like colorectal [25], breast [26,27], lung [28] cancer, melanoma [29], lymphoma [30], bone [31], gastric [32] and pancreatic [33] cancer; pediatric peripheral tumors like osteosarcoma [31], and adult central nervous system (CNS) tumors like glioblastoma multiforme (GBM) [34].