Abstract
Gliomas are highly malignant brain tumors that are highly invasive and resistant to conventional therapy. Receptor tyrosine kinases (RTKs) such as PDGFRα (platelet-derived growth factor receptor-α), which show frequent aberrant activation in gliomas, are associated with a process of epithelial-mesenchymal transition (EMT), a cellular alteration that confers a more invasive and drug-resistant phenotype. Although this phenomenon is well documented in human cancers, the processes by which RTKs including PDGFRα mediate EMT are largely unknown. Here, we report that SHP-2 (encoded by PTPN11) upregulates an EMT inducer, ZEB1, to mediate PDGFRα-driven glioma EMT, invasion and growth in glioma cell lines and patient-derived glioma stem cells (GSCs) using cell culture and orthotopic xenograft models. ZEB1 and activated PDGFRα were coexpressed in invasive regions of mouse glioma xenografts and clinical glioma specimens. Glioma patients with high levels of both phospho-PDGFRα (p-PDGFRα) and ZEB1 had significantly shorter overall survival compared with those with low expression of p-PDGFRα and ZEB1. Knockdown of ZEB1 inhibited PDGFA/PDGFRα-stimulated glioma EMT, tumor growth and invasion in glioma cell lines and patient-derived GSCs. PDGFRα mutant deficient of SHP2 binding (PDGFRα-F720) or phosphoinositide 3-kinase (PI3K) binding (PDGFRα-F731/42), knockdown of SHP2 or treatments of pharmacological inhibitor for PDGFRα-signaling effectors attenuated PDGFA/PDGFRα-stimulated ZEB1 expression, cell migration and GSC proliferation. Importantly, SHP-2 acts together with PI3K/AKT to regulate a ZEB1-miR-200 feedback loop in PDGFRα-driven gliomas. Taken together, our findings uncover a new pathway in which ZEB1 functions as a key regulator for PDGFRα-driven glioma EMT, invasiveness and growth, suggesting that ZEB1 is a promising therapeutic target for treating gliomas with high PDGFRα activation.