CDKN1A and glioblastoma: MiR‐17‐92 cluster inhibition decreases cell proliferation and induces apoptosis in glioblastoma spheroids culture by up‐regulating the expression of CDKN1A (cyclin‐dependent kinase inhibitor 1A), E2F1 and PTEN.15 MiR‐17‐92 cluster is regarded as the first miRNA cluster with oncogenic potential,15 the cluster includes 6 single mature miRNAs, miR‐19 has been supposed to be the key oncogenic miRNA among the six members of miR‐17‐92 cluster.