Responses on integrin ligation are attenuated by concomitant SYK inhibition. (A) Mean of MFI of pAkt expression in primary CLL cells cultured with or without VCAM-1–coated plates in the presence or absence of R406. Displayed are the mean values as assessed by flow cytometry (n = 9). (B) F-actin formation increased on VCAM-1 contact in DMSO control-treated cells but not in R406 pretreated cells, determined by confocal microscopy of CLL cells. Cells attached to VCAM-1 or poly-L-lysine (control)–coated slides and were stained with phalloidin-Alexa594 (representative example). (C) Quantification of F-actin formation by flow cytometry using phalloidin-Alexa488 for 7 primary CLL samples. The up-regulation induced by VCAM-1 contact in control cells (P < .001) was in part abrogated by concomitant SYK inhibition (P = .06). (D) CLL cells adhered less effective toward a VCAM-1–coated surface during SYK inhibition as determined by flow chamber analysis. The mean of triplicates for control and R406-treated samples (n = 10) were calculated, and the cell count of control-treated cells was determined as 100% (P < .01). Photographs of a representative example are displayed. (E) CLL cell treatment with R406 resulted in a reduced expression of the active conformation of CD29 compared with vehicle control (n = 20, P < .01).