The effect of Rock and Rac1 inhibitors on chemotaxis and actin polymerization. (A) Expression of CXCR4 on MM cell lines (MM1S, OPM2, and RPMI8226) detected by flow cytometry showing that MM1S, OPM2, and RPMI8226 had low, intermediate, and high expression of CXCR4, respectively. (B) The effect of ROCK and Rac1 inhibitors on SDF1-induced chemotaxis of MM cell lines that was shown to correlate with the expression of CXCR4; ROCK, but not Rac1, inhibitor prevents the SDF1-induced migration of MM cells. (C) The effect of ROCK and Rac1 inhibitors on the SDF1-induced chemotaxis in MM cells from patient samples showing similar result to those obtained with the cell lines. (D) The effect of ROCK and Rac1 inhibitors on SDF1-induced actin polymerization and polarization detected by confocal microscopy and (E) flow cytometry. It was shown that both inhibitors reduced actin polymerization, but the ROCK inhibitor showed a more profound effect, and only the ROCK inhibitor prevented actin polarization. Panels A-C: Groups compared with SDF1-treated group. *P < .05; #P < .01.