PRKD1 and hepatocellular carcinoma: As AKT, ERK, 70-kDa ribosomal S6 kinase (S6K1) and PKD have been demonstrated to be upstream regulators of GSK-3β in different cellular contexts [22-25], we thus evaluated which pathways are required for TNF-α induced phosphorylation of GSK-3β in HCC cells.