Given that the upregulated HBsAg and HBV DNA levels are linked to a high risk of development of HCC (Tseng et al., 2012; Gai et al., 2013; Kawanaka et al., 2014), PIN1 plays important roles in tumor development (Kozono et al., 2018); PIN4 is critical for PGCIα induction and tumor progression (Frattini et al., 2018); and inhibition or knockdown of PIN1 and PIN4 significantly reduced HBV DNA and HBsAg levels. Here, PIN4 is linked to hepatocellular carcinoma.