Extracellular ATP promotes breast cancer invasion and EMT via HIF-2 alpha signaling

Extracellular ATP has been shown to play an important role in invasion and the epithelial-mesenchymal transition (EMT) process in breast cancer; however, the mechanism is unclear. Here, by using a cDNA microarray, we demonstrated that extracellular ATP could stimulate hypoxia-inducible factor (HIF) signaling and upregulate hypoxia-inducible factor 1/2 alpha (HIF-1/2 alpha) expression. After knocking down HIF-1/2 alpha using siRNA, we found that ATP-driven invasion and EMT were significantly attenuated via HIF2A-siRNA in breast cancer cells. By using ChIP assays, we revealed that the biological function of extracellular ATP in invasion and EMT process depended on HIF-2 alpha direct targets, among which lysyl oxidase-like 2 (LOXL2) and matrix metalloproteinase-9 (MMP-9) mediated ATP-driven invasion, and E-cadherin and Snail mediated ATP-driven EMT, respectively. In addition, using silver staining and mass spectrometry, we found that phosphoglycerate kinase 1 (PGK1) could interact with HIF-2 alpha and mediate ATP-driven HIF-2 alpha upregulation. Furthermore, we demonstrated that expressions of HIF-2 alpha and its target proteins could be regulated via ATP by AKT-PGK1 pathway. Using a Balb/c mice model, we illustrated the function of HIF-2 alpha in promoting tumor growth and metastasis in vivo. Moreover, by exploring online databases, we found that molecules involved in ATP-HIF-2 alpha signaling were highly expressed in human breast carcinoma tissues and were associated with poor prognosis. Altogether, these findings suggest that extracellular ATP could promote breast carcinoma invasion and EMT via HIF-2 alpha signaling, which may be a potential target for future anti-metastasis therapy.