Preferential expression of functional IL-17R in glioma stem cells: potential role in self-renewal
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Prahlad Parajuli1, Rohit Anand1, Chandramouli Mandalaparty1, Raviteja Suryadevara1, Preethi U. Sriranga1, Sharon K. Michelhaugh1, Simona Cazacu4, Susan Finniss4, Archana Thakur2, Lawrence G. Lum2,3, Dana Schalk2, Chaya Brodie4, Sandeep Mittal1,2
1Department of Neurosurgery, Wayne State University and Karmanos Cancer Institute, Detroit, MI, USA
2Department of Oncology, Wayne State University and Karmanos Cancer Institute, Detroit, MI, USA
3Departments of Internal Medicine, Immunology and Microbiology, and Pediatrics, Wayne State University, Detroit, MI, USA
4Hermelin Brain Tumor Center, Henry Ford Hospital, Detroit, MI, USA
Prahlad Parajuli, e-mail: firstname.lastname@example.org
Keywords: glioma stem cells (GSCs), IL-17, IL-17R, IL-6, NF-κB
Received: July 22, 2015 Accepted: December 26, 2015 Published: January 08, 2016
Gliomas are the most common primary brain tumor and one of the most lethal solid tumors. Mechanistic studies into identification of novel biomarkers are needed to develop new therapeutic strategies for this deadly disease. The objective for this study was to explore the potential direct impact of IL-17−IL-17R interaction in gliomas. Immunohistochemistry and flow cytometry analysis of 12 tumor samples obtained from patients with high grade gliomas revealed that a considerable population (2–19%) of cells in all malignant gliomas expressed IL-17RA, with remarkable co-expression of the glioma stem cell (GSC) markers CD133, Nestin, and Sox2. IL-17 enhanced the self-renewal of GSCs as determined by proliferation and Matrigel® colony assays. IL-17 also induced cytokine/chemokine (IL-6, IL-8, interferon-γ-inducible protein [IP-10], and monocyte chemoattractant protein-1 [MCP-1]) secretion in GSCs, which were differentially blocked by antibodies against IL-17R and IL-6R. Western blot analysis showed that IL-17 modulated the activity of signal transducer and activator of transcription 3 (STAT3), nuclear factor κ-light-chain-enhancer of activated B cells (NF-κB), glycogen synthase kinase-3β (GSK-3β) and β-catenin in GSCs. While IL-17R-mediated secretion of IL-6 and IL-8 were significantly blocked by inhibitors of NF-κB and STAT3; NF-κB inhibitor was more potent than STAT3 inhibitor in blocking IL-17-induced MCP-1 secretion. Overall, our results suggest that IL-17–IL-17R interaction in GSCs induces an autocrine/paracrine cytokine feedback loop, which may provide an important signaling component for maintenance/self-renewal of GSCs via constitutive activation of both NF-κB and STAT3. The results also strongly implicate IL-17R as an important functional biomarker for therapeutic targeting of GSCs.
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