The p53 and ARF pathways are frequently disrupted in Eμ-Myc lymphoma.35 However, we found that mRNA levels of p53 target genes, such as Mdm2 and Bax, as well as the CDKN2A gene that encodes the ARF protein were similar across end-stage Eμ-Myc and Eμ-Myc/c-rel–/– tumour cells (not shown), suggesting that c-Rel loss does not lead to further disruption of these pathways. This evidence concerns the gene MDM2 and lymphoma.