DKK1 and hepatocellular carcinoma: Overexpression of DKK1 is associated with a poor prognosis in human HCC.20 In addition, DKK1 can be used as a serum biomarker for the diagnosis of HCC.21,22 It has been reported that HCC develops with increased frequency in hepatitis B virus surface antigen (HBsAg) transgenic mice.23 We previously reported that DKK1 was upregulated in HBsAg mouse liver tissues and in human HCC.24 Ultimately, the specific role of DKK1 in HCC remains controversial.