The complex microenvironment of malignant gliomas plays a dynamic and usually cancer-promoting role in glioma progression. Astrocytes, the major stromal cells in the brain, can be activated by glioma microenvironment, resulting in a layer of reactive astrocytes surrounding the gliomas. Reactive astrocytes are universally characterized with the upregulation of glial fibrillary protein and glycoprotein podoplanin. In this work, we investigated the role of reactive astrocytes on malignant glioma microenvironment and the potential mechanism by which glioma cells activated the tumor-associated astrocytes (TAAs). The reactive astrocytes were observed around gliomas in the intracranial syngeneic implantation of rat C6 and mouse GL261 glioma cells in vivo, as well as primary astrocytes cultured with glioma cells condition medium in vitro. Besides, reactive astrocytes exhibited distinct epithelial-to-mesenchymal (-like) transition and enhanced migration and invasion activity, with the decrease of E-cadherin and concomitant increase of vimentin and matrix metalloproteinases. Furthermore, canonical Wnt/β-catenin signaling was activated in TAAs. The Wnt/β-catenin pathway inhibitor XAV939 and β-catenin plasmid were used to verify the regulation of Wnt/β-catenin signaling on TAAs and their invasion ability. Taken together, our findings established that glioma cells remarkably activated astrocytes via upregulating Wnt/β-catenin signaling, with obviously mesenchymal-like transition and increased migration and invasion ability, indicating that glioma cells may stimulate adjacent astrocytes to degrade extracellular matrix and thereby promoting tumor invasiveness.
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This work was supported by National Natural Science Foundation of China (Nos. 81372268, 81173087 and 81202611), Program of State Key Laboratory of Natural Medicines, China Pharmaceutical University (No. SKLNMZZCX201405), Natural Science Foundation for Distinguished Young Scholars of Jiangsu Province (No. BK20130026), the Program for Jiangsu Province Innovative Research Team, and National Found for Fostering Talents of Basic Science (No. J1030830).
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Conflict of interest
The authors declare that they have no conflict of interest.
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