EP300 and cancer: Deregulated HAT activity is particularly linked to cancer formation and progression.9, 14, 15, 16 Certain types of leukemia are characterized by the occurrence of fusion proteins with increased HAT activity.17 Furthermore, lysine acetylation of the oncogenic fusion protein AML1-ETO by the HAT p300 has been demonstrated in patient blasts using western blotting and is required for leukemic transformation in mouse models as shown by mutation studies.