Hypoxia Promotes Human NSCLC Cell Line A549 Motility and EMT Through Extracellular HSP90α

Background: Epithelial to mesenchymal transition (EMT) is related to invasion and migration during lung cancer development. Extracellular HSP90α (eHSP90α) plays a critical role in tumor malignant progression. Whether eHSP90α participates in EMT of non-small-cell lung cancer (NSCLC) remains unclear. Methods: Human NSCLC cell line A549 were incubated in a hypoxic environment (1% O2) or in a normoxic environment (21% O2). HSP90α monoclonal antibody was used to neutralize eHSP90α, while recombinant HSP90α was used to simulate increased eHSP90α. Invasive potency of NSCLC cells was detected by cell invasion assay and migration assay, while the expression of EMT markers E-ca, vimentin and α-SMA were evaluated by western blot. Result: NSCLC cell lines constitutively secreted HSP90α. eHSP90α blockage inhibited cell motility in normoxic environment. Hypoxia induced NSCLC cells to secret more HSP90α. Hypoxia activated ERK through LRP1, and then enhanced A549 cell motility, down-regulated E-cadherin, up-regulated vimentin and α-SMA, and shifted cell morphology toward a mesenchymal phenotype. Similar results were obtained when cells were treated with recombinant HSP90α in normoxic environment. Inhibition of ERK reversed these effects. Furthermore, in the present of HSP90α monoclonal antibody in hypoxic environment, A549 cells migration and invasion were blocked and pro-motility signaling was attenuated, with less ERK activation and led cell morphology to an epithelial phenotype. Conclusion: eHSP90α promoted cell motility and induced EMT in NSCLC cell lines. Therefore, eHSP90α may become a novel target of non-small cell lung cancer in the clinical treatment.