EP300 and cancer: After being found to be tumor suppressors in a variety of cancers,385 CBP/p300 has lately come to light as essential regulators of transcriptional activation mediated by enhancers and super-enhancers, especially with regard to important oncogenes.386,387 In ALL, binding sites for the MYB transcription factor are created upstream of the TAL1 oncogene by heterozygous somatic mutations.