CNTF receptor subunit α as a marker for glioma tumor-initiating cells and tumor grade: laboratory investigation.
OBJECTIVE
Tumor-initiating cells are uniquely resilient to current treatment modalities and play an important role in tumor resistance and recurrence. The lack of specific tumor-initiating cell markers to identify and target these cells presents a major obstacle to effective directed therapy.


METHODS
To identify tumor-initiating cell markers in primary brain tumors, the authors compared the proteomes of glioma tumor-initiating cells to their differentiated progeny using a novel, nongel/shotgun-based, multidimensional liquid-chromatography protein separation technique. An in vivo xenograft model was used to demonstrate the tumorigenic and stem cell properties of these cells. Western blot and immunofluorescence analyses were used to confirm findings of upregulated ciliary neurotrophic factor receptor subunit-α (CNTFRα) in undifferentiated tumor-initiating cells and gliomas of increasing tumor grade. Sequencing of the CNTFRα coding regions was performed for mutation analysis. Finally, antibody-dependent cell-mediated cytotoxicity was used to establish the role of CNTFRα as a potential immunotherapeutic target.


RESULTS
Ciliary neurotrophic factor receptor subunit-α expression was increased in tumor-initiating cells and was decreased in the cells' differentiated progeny, and expression levels increased with glioma grade. Mutations of CNTFRα are not common in gliomas. Functional studies using CNTF treatment in glioma tumor-initiating cells showed induction of differentiation through the CNTFRα pathway. Treatment with anti-CNTFRα antibody resulted in increased antibody-dependent cell-mediated cytotoxicity in CNTFRα expressing DAOY cells but not in cell lines that lack CNTFRα.


CONCLUSIONS
These data indicate that CNTFRα plays a role in the formation or maintenance of tumor-initiating cells in gliomas, is a marker that correlates with histological grade, may underlie treatment resistance in some cases, and is a potential therapeutic target.
Surgical Neurology Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda.
Jie
J
Lu
Surgical Neurology Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda.
Alexander
A
Ksendzovsky
Surgical Neurology Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda.
Chunzhang
C
Yang
Surgical Neurology Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda.
Gautam U
GU
Mehta
Surgical Neurology Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda.
Raymund L
RL
Yong
Rose Ella Burkhardt Brain Tumor and Neuro-Oncology Center, Department of Neurosurgery, The Neurological Institute, Cleveland Clinic, Cleveland, Ohio.
Robert J
RJ
Weil
Department of Neurological Surgery, University of Virginia Health System, Charlottesville, Virginia.
Deric M
DM
Park
Surgical Neurology Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda.
Harry M
HM
Mushlin
Calibrant Biosystems, Gaithersburg, Maryland.
Xueping
X
Fang
Calibrant Biosystems, Gaithersburg, Maryland.
Brian M
BM
Balgley
Department of Neurological Surgery, University of Virginia Health System, Charlottesville, Virginia.
Dae-Hee
DH
Lee
Calibrant Biosystems, Gaithersburg, Maryland.
Cheng S
CS
Lee
Surgical Neurology Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda.
Russell R
RR
Lonser
Surgical Neurology Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda.
Zhengping
Z
Zhuang
D000818:Animals; D014408:Biomarkers, Tumor / Q000235:genetics / Q000378:metabolism*; D015153:Blotting, Western; D001932:Brain Neoplasms / Q000378:metabolism / Q000473:pathology* / Q000601:surgery*; D002853:Chromatography, Liquid; D053739:Ciliary Neurotrophic Factor Receptor alpha Subunit / Q000235:genetics / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D015972:Gene Expression Regulation, Neoplastic; D005910:Glioma / Q000378:metabolism / Q000473:pathology* / Q000601:surgery*; D006801:Humans; D051379:Mice; D008819:Mice, Nude; D009154:Mutation; D060787:Neoplasm Grading; D014411:Neoplastic Stem Cells / Q000378:metabolism* / Q000473:pathology; D014183:Transplantation, Heterologous; D015854:Up-Regulation
D014408:Biomarkers, Tumor; D053739:Ciliary Neurotrophic Factor Receptor alpha Subunit