E2F1 and hepatocellular carcinoma: qRT‒PCR analysis revealed that E2F1 was downregulated in HCC cells transfected with siRNAs targeting circMYBL2 but was upregulated in HCC cells also transduced with the lentiviral circMYBL2 overexpression vector (LV-circMYBL2) (Fig. 5C).