CDKN1A and acute lymphoblastic leukemia: Semi-quantitative evaluation of the expression of two bona fide p53 target genes, MDM2 and CDKN1A revealed that both transcripts were markedly increased in primary BCP-ALL as compared to healthy donors, whereas only CDKN1A mRNA but not MDM2 was increased in relapse BCP-ALL (Fig. 1b).