PCNA and hepatocellular carcinoma: Thus, increased Dnmt1 protein expression may play an important role in the malignant progression of HCC, which indicates that it is associated with a poor prognosis in HCC patients.35 In this study, As2O3-NPs also reduced the expression of DNA methyltransferases in vivo.36,37 PCNA plays an important role in DNA replication, and As2O3-NPs decreased PCNA expression.