Consistently, transfection of sh-circ-CSPP1 upregulated Rb and E-cadherin, but downregulated CCNE2, the tumor suppressor protein retinoblastoma (pRb), transcription factor E2F1 and c-myc, well- known as cyclin-dependent kinase inhibitors in HCC cells. Here, E2F1 is linked to hepatocellular carcinoma.