['Sorafenib is a promising treatment for hepatocellular carcinoma (HCC) but recent toxicity concerns suggest that new strategies for its use are needed. One approach for reducing toxicity is to use lower doses of sorafenib in combination with other complementary mechanisms. Celecoxib, a cyclooxygenase-2 inhibitor, has been shown to inhibit HCC, and we hypothesized that low-dose sorafenib co-administered with celecoxib could act synergistically in the inhibition of HCC. In this study, the effect of sorafenib was tested in combination with celecoxib on the growth of human HCC cells in vitro.', 'Two human HCC cell lines, HepG2 and Huh7, were treated with sorafenib and celecoxib, alone and in combination, and the effect of these treatments on growth, apoptosis, and expression of phospho-AKT was evaluated by WST-8, DNA content, and immunocytochemical assays, respectively.', 'When compared to the actions of either agent alone, the combination of low concentrations of sorafenib (<5 μM) and celecoxib (<20 μM) resulted in enhanced inhibition of both cell growth and AKT activation, and increased the induction of apoptosis. Combination index (CI) analysis showed that the growth inhibition effect was synergistic.'] Does combining celecoxib with sorafenib synergistically inhibit hepatocellular carcinoma cells in vitro?