IKZF1 drives the activity of lenalidomide in sensitive TCL cells. (A) Cell count and percent PI⁺ in TCL lines treated with 1 μM lenalidomide (len), pomalidomide (pom), or DMSO. The experiment was performed in triplicate and replicated twice. Data are presented as mean plus or minus SD. Comparisons are by 2-way ANOVA and Bonferroni correction for multiple comparisons. (B) SU-DHL-1 cells were treated with 2.5 μM len (left), 1 μM pom (right), or DMSO for 5 hours, and protein abundance was quantified using TMT mass spectrometry–based proteomics. Significant changes were assessed by a moderated t test as implemented in the limma package, with the log₂ fold change (log₂FC) shown on the y-axis, and −log₁₀(P values) on the x-axis (3 independent biological replicates for each IMiD drug and DMSO control). (C) Western blot analysis for IKZF1, IL-10, and ZFP91 proteins in SU-DHL-1 cells treated with IMiDs for 5 hours. (D) Western blot analysis in SU-DHL-1 cells treated with 2.5 μM len for indicated durations. (E) qPCR analysis in SU-DHL-1 cells treated with 2.5 μM len for indicated durations. Gene expression is normalized to RPS18. Data are presented as mean of 3 replicates plus or minus SEM. (F) Western blot analysis of doxycycline (dox)-induced sgRNA²³ targeting IKZF1 or nontargeting control (NTC). (G) Cell count and percent PI⁺ in SU-DHL-1 cells with dox-induced expression of sgRNA targeting IKZF1 or NTC. The experiment was performed in triplicate and replicated twice. Data are presented as mean plus or minus SD. Comparisons are by 2-way ANOVA and Bonferroni correction for multiple comparisons. **P < .01; ***P < .001. IB, immunoblot; qPCR, quantitative polymerase chain reaction; SEM, standard error of the mean; sgRNA, single-guide RNA; TMT, tandem mass tag.