PCNA and hepatocellular carcinoma: Consistently, collagen I-induced upregulation of proliferation (PCNA), phosphorylated ERK1/2, EMT (vimentin and N-cadherin), cancer stem cell marker Nanog was markedly reduced in heat-exposed residual HCC cells pretreated with ERK1/2 inhibitor U0126 (Figs. 2b, 3c).