It was found for the first time in 2004 that KLF6 expression in glioblastoma multiforme (GBM) can inhibit the growth and tumorigenicity of glioblastoma which could then activate the p21Cip1/Waf1 promoter both in vitro and in vivo (Kimmelman et al., 2004). Here, CDKN1A is linked to glioblastoma.