CDKN1A and glioma: In vitro, irradiated glioma cell lines die up to 20%, but 60–80% of cells are arrested in the cell cycle, exhibiting senescence markers, such as senescence-associated β-galactosidase (SA-β-gal), H3me9 histone methylation, and p53/p21-positivity as well as upregulating SASP and NF-κB transcriptional activity [231].