PI3 kinase/Akt signaling mediates epithelial-mesenchymal transition in hypoxic hepatocellular carcinoma cells

Hypoxia activates genetic programs that facilitate cell survival; however, in cancer, it may promote invasion and metastasis. Although the exact mechanisms driving hypoxia-induced invasion and metastasis remain elusive, we hypothesized that epithelial-mesenchymal transition (EMT) may play a major role. We investigated this in vitro by treating hepatocellular carcinoma cells under 1.0% O₂. After the hypoxia treatment, the cells exhibited some morphological changes including cell elongation, cytoskeletal rearrangement, and junctional disruption. Moreover, expression of the epithelia-specific marker E-cadherin was decreased and expression of the myofibroblast-specific marker vimentin was detected in the treated cells. Cell migration and ECM gel invasion were increased. These findings were consistent with events observed during EMT. Hypoxia-induced EMT is accompanied by increased phosphorylation, activation of Akt and the downstream signaling. Hypoxia-induced EMT was blocked by PI3K inhibitor LY294002. The results suggest that the PI3K/Akt-dependent signaling pathways serve to regulate hypoxia-induced EMT of hepatocellular carcinoma cells.