CDK4 and esophageal squamous cell carcinoma: Inhibition of GSK-3β causes ESCC cells to stall in G0/G1 and G2/M phases, and it also downregulates the expression of cyclin D1 and cyclin dependent kinase 4 (CDK4) and upregulates the expression of cyclin B1 (Bolidong et al., 2020).