IMiDs upregulate intracellular THBS-1 expression in a proteasome-dependent manner. (A) Immunoblot analysis for THBS-1 and IKZF1 protein levels in MEG01 cells treated for 24 hours with DMSO or 10 μM lenalidomide. (B) Time course analysis of THBS-1 protein expression in MEG01 cells treated with 10 μM lenalidomide and pomalidomide for the indicated times. (C) Immunoblot analysis for THBS-1 in MEG01 cells treated with thalidomide, lenalidomide, and pomalidomide at indicated concentrations for 24 hours. (D) Relative mRNA expression levels of THBS1 in MEG01 cells. Cells were treated with DMSO, 10 μM lenalidomide, or pomalidomide for 24 hours. Data are from 9 independent experiments and are expressed as means ± standard error of the mean (SEM). P values were determined by 2-tailed Student t test. (E) Immunoblot analysis for THBS-1 in MEG01 cells treated with 10 μg/mL cycloheximide for the indicated times. (F) Immunoblot analysis for THBS-1 in MEG01 cells treated with 10 μM IMiDs and/or 1 μM MG132 for 24 hours. Results are representative of 2 (panel A) and 3 (panels B, C, E, and F) independent experiments. Cont, control; IB, immunoblotting; Len, lenalidomide; Pom, pomalidomide; Thal, thalidomide.