PCNA and hepatocellular carcinoma: For example, coculture of MSCs with hepatoma cells results in an increase in tumor cell apoptosis and decrease in proliferation by down-regulating Bcl-2, c-Myc, proliferating cell nuclear antigen (PCNA), and survivin protein levels in hepatoma tumor cells (Lowe et al., 2010); all of them are targets of Wnt signaling (Gordon and Martinez, 2010; Ji et al., 2016).