SPP1 and hepatocellular carcinoma: The search for serum protein markers for early detection of HCC has identified numerous promising candidates including: des-gamma-carboxy-prothrombin (PIVKA-II), glypican-3, the ratio of glycosylated AFP (L3 fraction) to total AFP, alpha fucosidase, Dickkopf-1 (DKK1), and osteopontin [163,164,165,166,167,168].