The cancer biomarker osteopontin: combination with other markers.

Osteopontin (OPN) is a biomarker for cancer progression and prognosis in multiple tumor types, however, it has not yet found entry into clinical diagnostics. In recent years, there has been an increasing recognition that marker combinations may have better diagnostic or prognostic potential than individual molecules. While various studies have analyzed OPN in conjunction with other markers, a comprehensive review of their published results is still lacking. OPN in tumor tissue or in the blood has been investigated in conjunction with a broad range of other markers in diverse types of cancer. OPN has been combined with cancer-specific markers, functionally converging biomolecules (angiogenesis, motility/adhesion, extracellular matrix, bone) and synergizing biomolecules (fibrinolytic system, calcium homeostatic proteins, squamous cell carcinoma antigen, NF-κB pathways, proteases). Clinical parameters of interest have been cancer detection, assessment of progression, and prognosis/treatment response. Some marker combinations with OPN are promising for detection, diagnosis or prognosis in various types of cancer. Yet, surprisingly, in many cases, the published results are conflicting, and no clear metrics have been developed for utilizing marker combinations in clinical decision making. With the current intense interest in multiplex marker panels, additional, large-scale studies are needed to realize the full diagnostic and prognostic potential of OPN.