PCNA and liver cancer: From the obtained results, suppression of CD1 and elevation of p21WAF1/Cip1 mRNA and cellular proliferation in CACHD1 knockdown human liver cancer cells, could induce p21WAF1/Cip1-dependent G1 and G2 arrest, which is related to capacity for direct binding to PCNA and inhibition of cyclin-dependent kinase complexes [33].