IKZF1 and IKZF3 double-knockout (DKO) cells are viable and susceptible to IMiD-induced toxicity and IRF4 downregulation. (A) Western blot analyses confirm efficient inactivation of IKZF1 and IKZF3 in Cas9-expressing BC-3 and BCBL-1 sequentially transduced with targeting sgRNAs. IRF4 expression was not altered, and GAPDH was the loading control. (B) Growth curve analyses of cell lines described in panel A (n = 3; error bars represent standard error of the mean [SEM]). (C) Pomalidomide IC₅₀ curves of cell lines described in panel A. The BC-3 CRBN knockout (KO) clone was included as an additional control (n = 3; error bars represent SEM). (D) Growth curve analyses after pomalidomide treatment of the cell lines described in panel A; live cell numbers are plotted relative to DMSO-treated controls (n = 3; error bars represent SEM). (E) Representative western blot analysis of IKZF1, IRF4, and MYC expression at all time points analyzed in panel D. GAPDH served as loading control.