(A) CD99-silenced cells showed reduced growth in monolayer conditions compared with controls. Reexpression of CD99 rescued the growth inhibition caused by CD99 knockdown in TC-71 and IOR/BRZ cells. Data are presented as mean ± SEM of experiments performed in triplicate. Absorbance was measured at a wavelength of 550 nm. *P < 0.05, Student’s t test with respect to parental and CD99-reexpressing cells. (B) CD99-silenced cells showed reduced growth in anchorage-independent conditions. Reexpression of CD99 rescued the growth inhibition. Data are presented as mean ± SEM of experiments performed in triplicate. *P < 0.05, **P < 0.001, Student’s t test versus parental and CD99-reexpressing cells. Representative photomicrographs are shown for TC-71–derived cells. Digital images were taken under identical conditions at the same time. Scale bars: 600 μm. (C) Migratory ability of CD99-silenced cells was significantly reduced compared with that of controls. Reexpression of CD99 rescued the migration deficit caused by CD99 knockdown in TC-71 and IOR/BRZ cells. Data are presented as mean ± SEM of experiments performed in triplicate and indicate the number of cells that migrated 12 hours after cell seeding. **P < 0.001, Student’s t test versus parental and CD99-reexpressing cells. (D) Cell adhesion tests to extracellular matrix components demonstrate that CD99-deprived cells adhere faster to collagen I and IV. Data are presented as mean ± SEM of experiments performed in triplicate. *P < 0.05 versus parental and CD9-reexpressing cells, Student’s t test.