AZD6244 treatment effects actin organization and reduces invasion. Drug treatment results in a marked re-organization of the actin cytoskeleton. Here, MLL cells were sparsely plated and actin staining was performed using rhodamine-phalloidin and DAPI as a counterstain for nuclei. Actin organization changed from predominantly cortical for untreated and DMSO-treated cells to arrangement into stress fibers in response to the AZD6244 (A). This was accompanied by a change in cell shape from predominantly spherical and loosely adherent to flatter cells that appeared to adhere more strongly to the substrate. Immunoblot analysis revealed no change in either α5β1 integrin expression or in fibronectin secretion (B).