Hypoxia promotes vasculogenic mimicry formation by the Twist1-Bmi1 connection in hepatocellular carcinoma

Aggressive tumor cells can mimic embryonic vasculogenic networks and form vasculogenic mimicry (VM). Preliminary studies demonstrated that hypoxia can promote VM formation; however, the underlying mechanism remains unclear. The present study aimed to investigate the role of the Twist1-Bmi1 connection in hypoxia-induced VM formation and the underlying mechanism. In the in vitro experiments, western blot analysis demonstrated that hypoxia upregulated the expression of Twist1, Bmi1, epithelial-mesenchymal transition (EMT) markers, stem cell markers and VM-associated markers. The 3D culture assay showed that hypoxia promoted VM formation in hepatocellular carcinoma (HCC) cell lines. Using transfection and in vitro cell experiments, the Twist1-Bmi1 connection was confirmed to have an important role in inducing EMT, cell stemness and VM formation. In the in vivo experiments, the murine hypoxia models were established via incomplete femoral artery ligation and the mechanism by which hypoxia promoted Twist1 and Bmi1 expression and led to VM formation was demonstrated by immunohistochemistry staining and endomucin/periodic acid Schiff double-staining. In conclusion, hypoxia upregulate the expression of Twist1 and Bmi1, and these two proteins have an important role in inducing EMT and cancer cell stemness, which contributed to VM formation.