Introduction: In vivo experiments in glioma have shown that cancer stem cells (CSCs) are uniquely resilient to current treatment regimens, contributing to both cancer resistance and recurrence. However, due to the lack of specific markers, identification of CSCs has presented a major challenge to their targeting and achieving cure. To identify new biomarkers and potential therapeutic targets we sought to find unique proteins from brain tumor-derived CSCs.
Methods: In this study, we compared the proteomes of glioma derived stem cells to their differentiated progeny to identify novel CSC-specific proteins. Proteomic analysis was performed using a novel “multidimensional” capillary isoelectric focusing nano-reversed-phase liquid chromatography with tandem mass spec (CIEF-nRPLC-MS). The expression of potential CSC markers was confirmed through western blot and immunohistochemistry. We also tested the impact of candidate proteins in patient brain tumor tissues and assessed their potential for clinical applications.
Results: We isolated several differentially expressed proteins, one of which was ciliary neurotrophic factor receptor subunit-alpha (CNTFRa). Considering its biological relevance in glial cell differentiation we focused our study on this protein. Using western blot and immunofluorescence, we confirmed CNTFRa down-regulation in differentiated CSC progeny and identified CNTFRa expression in patient glioma samples. Additionally, CNTFRa expression rose proportionally in tumors of increasing grade, which highlights its potential use for tumor prognosis. To assess the potential of CNTFRa as a therapeutic target, antibody-dependent cell-mediated-cytotoxicity (ADCC) was tested and the result showed increased cytotoxicity in CNTFRa expressing tumor cells.
Conclusions: Our results suggest a critical role for CNTFRa in primary brain tumors, based on robust expression levels in both whole tumor extracts and purified CSCs. CNTFRa may serve as a tool in the histologic diagnosis of glioma and has the potential to be used for targeted imaging. Furthermore, CNTFRa may be a promising therapeutic target, both through receptor-directed immunotherapy and receptor-mediated pro-differentiation effects.
Patient Care: The prognosis for high grade glioma remains poor due to the resilient nature of its CSC component. Through its targeting, CNTFRa as a CSC marker, has diagnostic, prognostic and therapeutic implications.
Learning Objectives: After this talk, the audience will be introduced to a novel proteomics technique (CIEF-nRPLC-MS) and will learn of a new potential target for glioma CSCs: CNTFRa. This target has diagnostic, prognostic and therapeutic applications.