Pomalidomide regulates cytoskeleton in monocytes through Rho GTPases. (A-B) Monocytes were treated with pomalidomide at the indicated concentration or DMSO as a control for 30 minutes, followed by rhodamine-phalloidin staining. Quantitation of staining is normalized and expressed as percent control relative to DMSO treatment. Data represent 3 independent experiments. Columns and error bars represent mean ± SEM (Student t test, *P < .05). (C-D) Representative experiment shows ROCK1 and Rac1 inhibitors decrease pomalidomide-induced F-actin formation in monocytes. Monocyte cells were treated with 1 μM pomalidomide for indicated time points. When ROCK1 or Rac1 inhibitors were used, cells were preincubated for 30 minutes in the presence of 10 μM ROCK1 inhibitor (Y27632) or Rac1 inhibitor, followed by DMSO or pomalidomide incubation. Quantitation of staining (D) is normalized and expressed as percent control relative to DMSO treatment. Data represent 3 independent experiments. Columns and error bars represent mean ± SEM (Student t test, *P < .05). (E) Pomalidomide stabilizes microtubule in human primary monocytes. Cells were treated with DMSO or 1 μM pomalidomide for indicated time points. Microtubule level was determined by Western blot analysis using tubulin antibody after the microtubule depolymerization. Treatment with 2 μM Taxol for 2 hours was used as a positive control. (F) ROCK1 and Rac1 inhibitors block pomalidomide-induced microtubule stabilization. Monocytes were pretreated with ROCK1 or Rac1 inhibitors for 15 minutes before pomalidomide stimulation. Treatment with 2 μM Taxol for 2 hours was used as a positive control.