Inhibition of HIF-1α by PX-478 suppresses tumor growth of esophageal squamous cell cancer in vitro and in vivo.

The aim of this study is to investigate the clinical significance of hypoxia inducible factor-1α (HIF-1α) expression in esophageal squamous cell cancer (ESCC) and clarify the effects of PX-478, a selective HIF-1α inhibitor, on ESCC both in vitro and in vivo. HIF-1α, cyclooxygenase-2 (COX-2) and programmed death ligand-1 (PD-L1) were markedly overexpressed in ESCC tissue and associated with poorer survival. In vitro, both COX-2 and PD-L1 expression of ESCC cells were significantly induced by CoCl₂ treatment, but inhibited by HIF-1α knock-down or PX-478 treatment. Furthermore, PX-478 significantly inhibited tumor cell proliferation by inhibiting the G2/M transition and promoting apoptosis of ESCC cells. In addition, inhibited epithelial-mesenchymal transition was observed after PX-478 treatment. In vivo, PX-478 significantly decreased tumor volume following subcutaneous implantation. Together, our results indicated that PX-478 had significant antitumor activity against HIF-1α over-expressing ESCC tumors in vitro and in vivo. These results opened up the possibility of inhibiting HIF-1α for targeted therapy of ESCC.