SPP1 and hepatocellular carcinoma: Several other biomarkers are suggested for use in the early diagnosis and prognostication of HCC, including osteopontin (OPN), midkine (MK), neopterin, squamous cell carcinoma antigen (SCCA), Mac-2-binding protein (M2BP), cyclic guanosine monophosphate (cGMP), and interleukin-6 (IL-6) [30,31,32,33,34].