MDM4 and glioblastoma: Although drugs for promoting the refolding of mutant proteins into wild-type conformations have not been successful, continuous efforts have been put in inhibiting the negative regulatory proteins of p53, MDM2 and MDM4, which aims at neutralizing defective MDM2 and MDM4 produced by amplification of MDM2 and MDM4 gene in GBM patients [105, 106].