Podoplanin is expressed in human OS cell lines and promotes platelet aggregation. A: Western blot analysis showing that podoplanin is endogenously expressed in three human OS cell lines, MG-63, HOS, and U-2 OS. The different sized bands are due to differences in glycosylation patterns between the cell lines. B: The platelet aggregation–inducing capability of three human OS cell lines, MG-63, HOS, and U-2 OS was estimated by incubating the cells with mouse platelet-rich plasma, and was quantified by light transmittance. Platelet aggregation is induced in three human OS cell lines that express endogenous podoplanin. C: Podoplanin knockdown in OS cells. Control (Co) and podoplanin (PDPN) siRNA-transfected MG-63 cells were analyzed for podoplanin expression by Western blot. Numerical values represent podoplanin expression levels relative to β-actin quantified by densitometric analysis. D: Podoplanin siRNA inhibits platelet aggregation of MG-63 cells. Platelet aggregation was attenuated in podoplanin siRNA–transfected MG-63 cells.