A member of the SIBLING family of glycoproteins (Rangaswami et al.), Osteopontin (OPN) functions as T-helper 1 cytokine, and plays an important role in cell signaling, migration, and activation (Weber et al., 2002). Osteopontin has been shown to regulate inflammation both in vitro and in vivo (Agnholt et al.; Kiefer et al.), and has been implicated in the pathophysiology of numerous cancers, including prostate (Thalmann et al.), lung (Chambers et al.), ovarian (Kim et al.), and breast etiologies (Weber et al., 2015). In humans, OPN is initially secreted as a 317 amino acid protein which is subject to tissue-specific post-translational modifications by glycosylation, phosphorylation, and transglutamination (Kazanecki et al.; Sodek et al.). This protein product contains a His-residue tag at the amino end of the polypeptide chain. For consistency and reproducibility across your applications, Osteopontin from STEMCELL comes lyophilized with ≥ 92% purity, and endotoxin levels are verified to be ≤ 1.0 EU/μg protein.