CD44 and neoplasm: In addition to OPN’s binding to its canonical CD44 and integrin receptors, a thrombin-cleaved OPN isoform was found to be able to bind to the costimulatory molecule inducible T-cell costimulator ligand (ICOSL), which could affect tumor-infiltrating B cell function as ICOSL expression on antigen-presenting B cells has been well documented (98–100).