KMT2A and leukemia: We subsequently confirmed that CCI-006 activated an ER stress response in PER-485 cells: the compound induced a rapid increase in eIF2α phosphorylation (p-eIF2α), exclusively in sensitive MLL-r leukemia cells (Fig. 3a, b), thereby signaling the activation of an unfolded protein response (UPR) that halts cap-mediated mRNA translation to protect against ER stress (reviewed in ref. [17]).