To evaluate the potential involvement of CREBBP/EP300 in proliferation, we evaluated the sensitivity of the human CML cell line K562 to the CREBBP/EP300 bromodomain inhibitor CBP30 [10], the EP300/CREBBP HAT activity inhibitor C646 [19] and as a positive control, the BET pan inhibitor JQ1 [6]. Here, CREBBP is linked to chronic myelogenous leukemia, BCR-ABL1 positive.