Requirement of OPN in migration induced by ATX-LPA axis protects against Taxol-induced apoptosis in SGC7901 cells. (A) Verification of siRNA knockdown of the OPN protein by Western blot showed a significant reduction of OPN protein in clone3 (SGC7901-siRNA-OPN). (B) The effect of OPN on ATX-LPA-induced migration was assayed using a Transwell assay. Either SGC7901, SGC7901-siRNA-vehicle, or SGC7901-siRNA-OPN cells (1 × 105) were added in the upper chambers of the transwells, incubated in DMEM/0.1% BSA or medium containing ATX, LPC, LPA, ATX/LPC2 and allowed to migrate for 48 hours at 37°C. Migrated cells on the lower chamber were quantified. (D) Flow cytometric analysis of apoptosis: SGC7901, SGC7901-siRNA-vehicle, or SGC7901-siRNA-OPN cells were treated with Taxol (50 nM) in the absence or presence of each group: ATX, LPC, LPA, ATX/LPC2 or DMEM/0.1% BSA for 24 hours. Apoptosis was analyzed by flow cytometry. Data shown in Figure 4C and E represents the mean ± SD from three individual experiments. Data are mean ± SD of triplicate determinations. Statistical analysis was performed using Student's t test. *p < 0.05.