SPP1 and neoplasm: Other new tumor biomarkers have been proposed, such as osteopontin (OPN), vascular endothelial growth factor (VEGF), angiopoietin 2 (ANG-2), Golgi protein 73 (Gp-73), insulin growth factor-1 (IGF-1), hepatic growth factor (HGF), and c-MET among others [5], but they are still a long way from clinical use.