MDM2 and glioblastoma: By documenting P1- and P2-MDM2-induced transcripts in a glioblastoma cell line (Tp265MG) with no MDM2 gene amplification and homozygously deleted TP53 and p14ARF, it was demonstrated that exon 2-derived transcripts, that is, transcripts initiated from the supposedly p53-responsive promoter (P2), were detectable even in the complete absence of all protein products of the TP53 gene.