To assess the cellular selectivity of SIM1 for BET proteins in a BET-relevant cellular background and also determine if BRD2 preference was observed in this context, multiplexed tandem mass tag (TMT) labeling mass spectrometry proteomic experiments were performed to monitor protein levels in a quantitative and unbiased fashion. Acute myeloid leukemia (AML) MV4;11 cells were treated in triplicate with DMSO, 10nM SIM1, or 10nM cis-SIM1 for 4h.