HA and OPN compete for Biotin-C21 binding to CD44. (A) Binding of Biotin-C21 to CD44 immobilized on nitrocellulose membranes was displaced with increasing concentrations of HA. No displacement is considered as 100% (controls). Mean ± SEM. n = 7. (B) Competition for Biotin-C21 binding to CD44 with increasing concentrations of C21 (closed triangles) or OPN (open triangles). Mean ± SEM. n = 5 for 8 μM OPN, n = 6 for 0.08 μM OPN and 0.33 μM C21, n = 8 for 0.8 μM OPN, n = 9 for 3.3 and 33 μM C21. P values calculated by analysis of variance and Student-Newman-Keuls test (C21 and HA) or Krustal-Wallis and Dunn's multiple comparisons test (OPN).