P210^BCR-ABL leads to increased integrin-mediated adhesion to fibronectin. (A) Each set of points makes up an individual spin and is the number of cells (adherent fraction) at a particular location on the coverslip that experiences a known shear stress relative to the count at the center where the shear stress is zero. Expression of MigP210^BCR-ABL (▦) allowed a higher fraction of cells to remain attached compared to vector control MigRI cells (•), indicating that MigP210^BCR-ABL–expressing cells bound more tightly to fibronectin. Coverslips coated with BSA alone did not support significant cell binding to either MigRI (▾) or MigP210^BCR-ABL (data not shown) cells. Binding of MigRI or MigP210^BCR-ABL cells to BSA-coated surfaces was comparable, and at times so few cells remained attached after a spin that a detachment profile could not be generated. Curves fitted to the experimental points for MigRI-expressing cells on BSA-only–coated coverslips (▿), MigRI cells on fibronectin-coated coverslips (○), and MigP210^BCR-ABL on fibronectin-coated coverslips (□). The dashed line represents an adherent fraction of 0.5. The critical shear stress (τ₅₀) is defined as the point on the abscissa (shear stress) that corresponds to an adherent fraction of 0.5 along the fitted curve. (B) τ₅₀ was determined for spins with 2 populations each of cells expressing MigRI (•) or MigP210^BCR-ABL (○), indicating that an average of 1.5 to 1.6 times as much force is needed to detach 50% of MigP210^BCR-ABL–expressing cells from fibronectin in our system. Each circle represents τ₅₀ for a particular spin, and rectangles denote standard deviations above and below the mean. Significance is shown and is determined by comparing the MigRI population (#1 or #2) with the corresponding MigP210^BCR-ABL population (#1 or #2). (C) MigRI cells were treated with a GRGDSP (RGD) peptide (P = .001), 0.02% sodium azide (NaAZ) (P =.001), or 1 mM EDTA (EDTA) (P = .001) and were assayed for the ability to bind fibronectin compared with untreated MigRI cells. MigRI cells were incubated on coverslips coated with BSA only as a negative control (P = .001). The percentage change in critical shear stress is relative to untreated MigRI cells.