title: Na⁺/K⁺-ATPase β2-subunit (AMOG) expression abrogates invasion of glioblastoma-derived brain tumor-initiating cells.
abstract: BACKGROUND
  Mechanisms of glioma invasion remain to be fully elucidated. Glioma cells within glioblastoma multiforme (GBM) range from well-differentiated tumor cells to less-differentiated brain tumor-initiating cells (BTICs). The β2-subunit of Na(+)/K(+)-ATPase, called the adhesion molecule on glia (AMOG), is highly expressed in normal glia but is thought to be universally downregulated in GBM. To test our hypothesis that expression of AMOG is heterogeneous in GBM and confers a less invasive phenotype, we compared it between BTICs and differentiated cells from patient-matched GBM and then tested GBM invasion in vitro after AMOG overexpression.
  
  
  METHODS
  Immunohistochemistry, immunoblotting, and real-time PCR were used to characterize AMOG protein and mRNA expression in tumor samples, BTICs, and differentiated cells. Matrigel invasion assay, scratch assay, and direct cell counting were used for testing in vitro invasion, migration, and proliferation, respectively.
  
  
  RESULTS
  While AMOG expression is heterogeneous in astrocytomas of grades II-IV, it is lost in most GBM. BTICs express higher levels of AMOG mRNA and protein compared with patient-matched differentiated tumor cells. Overexpression of AMOG decreased GBM cell and BTIC invasion without affecting migration or proliferation. Knockdown of AMOG expression in normal human astrocytes increased invasion.
  
  
  CONCLUSIONS
  AMOG expression inhibits GBM invasion. Its downregulation increases invasion in glial cells and may also represent an important step in BTIC differentiation. These data provide compelling evidence implicating the role of AMOG in glioma invasion and provide impetus for further investigation.
authors.affiliation: Corresponding Author: Andrew T. Parsa, MD, PhD, Department of Neurological Surgery, University of California, San Francisco, 505 Parnassus Ave., San Francisco, CA 94117. parsaa@neurosurg.ucsf.edu.
authors.forename: Matthew Z
authors.initials: MZ
authors.lastname: Sun
authors.forename: Joseph M
authors.initials: JM
authors.lastname: Kim
authors.forename: Michael C
authors.initials: MC
authors.lastname: Oh
authors.forename: Michael
authors.initials: M
authors.lastname: Safaee
authors.forename: Gurvinder
authors.initials: G
authors.lastname: Kaur
authors.forename: Aaron J
authors.initials: AJ
authors.lastname: Clark
authors.forename: Orin
authors.initials: O
authors.lastname: Bloch
authors.forename: Michael E
authors.initials: ME
authors.lastname: Ivan
authors.forename: Rajwant
authors.initials: R
authors.lastname: Kaur
authors.forename: Taemin
authors.initials: T
authors.lastname: Oh
authors.forename: Shaun D
authors.initials: SD
authors.lastname: Fouse
authors.forename: Joanna J
authors.initials: JJ
authors.lastname: Phillips
authors.forename: Mitchel S
authors.initials: MS
authors.lastname: Berger
authors.forename: Andrew T
authors.initials: AT
authors.lastname: Parsa
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism*; D001932:Brain Neoplasms / Q000378:metabolism* / Q000401:mortality / Q000473:pathology*; D027682:Cation Transport Proteins / Q000378:metabolism*; D015816:Cell Adhesion Molecules, Neuronal / Q000378:metabolism*; D015536:Down-Regulation; D005909:Glioblastoma / Q000378:metabolism* / Q000401:mortality / Q000473:pathology*; D006801:Humans; D009361:Neoplasm Invasiveness; D015996:Survival Rate; D014407:Tumor Cells, Cultured
chemical_list: C504190:ATP1B2 protein, human; D027682:Cation Transport Proteins; D015816:Cell Adhesion Molecules, Neuronal; D000251:Adenosine Triphosphatases
keywords: AMOG; Na+/K+-ATPase β2-subunit; brain tumor-initiating cells; glioblastoma; invasion