Though some studies showed that serum RBP4 was upregulated in some cancers such as ovarian and pancreatic cancers [34, 35], many other studies found significantly decreased levels of serum RBP4 in cancers such as ovarian cancer [36], HCC [37, 38], head and neck cancer [39], and breast cancer [40]. This evidence concerns the gene RBP4 and hepatocellular carcinoma.