CDK6 and hepatocellular carcinoma: Given the role of GSK3β in β-catenin degradation by ubiquitination, we showed that CDK6 knockdown in HCC cells increased β-catenin ubiquitination, as determined by ubiquitination and western blot assays (Fig. 7a), reduced transcription of Wnt target genes (including AXIN2, CMYC and CCND2) (Fig. 7b), reduced β-catenin accumulation and decreased transactivating activity of β-catenin as determined by a TOP/FOP reporter assay (Fig. 7c, d).