title: Brain tumor cells in circulation are enriched for mesenchymal gene expression.
abstract: Glioblastoma (GBM) is a highly aggressive brain cancer characterized by local invasion and angiogenic recruitment, yet metastatic dissemination is extremely rare. Here, we adapted a microfluidic device to deplete hematopoietic cells from blood specimens of patients with GBM, uncovering evidence of circulating brain tumor cells (CTC). Staining and scoring criteria for GBM CTCs were first established using orthotopic patient-derived xenografts (PDX), and then applied clinically: CTCs were identified in at least one blood specimen from 13 of 33 patients (39%; 26 of 87 samples). Single GBM CTCs isolated from both patients and mouse PDX models demonstrated enrichment for mesenchymal over neural differentiation markers compared with primary GBMs. Within primary GBMs, RNA in situ hybridization identified a subpopulation of highly migratory mesenchymal tumor cells, and in a rare patient with disseminated GBM, systemic lesions were exclusively mesenchymal. Thus, a mesenchymal subset of GBM cells invades the vasculature and may proliferate outside the brain.
  
  
  CONCLUSIONS
  GBMs are locally invasive within the brain but rarely metastasize to distant organs, exemplifying the debate over "seed" versus "soil." We demonstrate that GBMs shed CTCs with invasive mesenchymal characteristics into the circulation. Rare metastatic GBM lesions are primarily mesenchymal and show additional mutations absent in the primary tumor.
authors.affiliation: Massachusetts General Hospital Cancer Center, Boston, Massachusetts. Department of Medicine, Harvard Medical School, Boston, Massachusetts.
authors.forename: James P
authors.initials: JP
authors.lastname: Sullivan
authors.affiliation: Massachusetts General Hospital Cancer Center, Boston, Massachusetts. Department of Neurosurgery, Harvard Medical School, Boston, Massachusetts.
authors.forename: Brian V
authors.initials: BV
authors.lastname: Nahed
authors.affiliation: Massachusetts General Hospital Cancer Center, Boston, Massachusetts.
authors.forename: Marissa W
authors.initials: MW
authors.lastname: Madden
authors.affiliation: Massachusetts General Hospital Cancer Center, Boston, Massachusetts.
authors.forename: Samantha M
authors.initials: SM
authors.lastname: Oliveira
authors.affiliation: Massachusetts General Hospital Cancer Center, Boston, Massachusetts.
authors.forename: Simeon
authors.initials: S
authors.lastname: Springer
authors.affiliation: Department of Neurology, Harvard Medical School, Boston, Massachusetts.
authors.forename: Deepak
authors.initials: D
authors.lastname: Bhere
authors.affiliation: Massachusetts General Hospital Cancer Center, Boston, Massachusetts. Department of Neurology, Harvard Medical School, Boston, Massachusetts.
authors.forename: Andrew S
authors.initials: AS
authors.lastname: Chi
authors.affiliation: Massachusetts General Hospital Cancer Center, Boston, Massachusetts. Department of Neurosurgery, Harvard Medical School, Boston, Massachusetts.
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Wakimoto
authors.affiliation: Massachusetts General Hospital Cancer Center, Boston, Massachusetts. Department of Medicine, Harvard Medical School, Boston, Massachusetts.
authors.forename: S Michael
authors.initials: SM
authors.lastname: Rothenberg
authors.affiliation: Massachusetts General Hospital Cancer Center, Boston, Massachusetts. Department of Medicine, Harvard Medical School, Boston, Massachusetts.
authors.forename: Lecia V
authors.initials: LV
authors.lastname: Sequist
authors.affiliation: Center for Engineering in Medicine, Harvard Medical School, Boston, Massachusetts.
authors.forename: Ravi
authors.initials: R
authors.lastname: Kapur
authors.affiliation: Department of Neurology, Harvard Medical School, Boston, Massachusetts. Department of Radiology, Harvard Medical School, Boston, Massachusetts.
authors.forename: Khalid
authors.initials: K
authors.lastname: Shah
authors.affiliation: Massachusetts General Hospital Cancer Center, Boston, Massachusetts. Department of Pathology, Harvard Medical School, Boston, Massachusetts.
authors.forename: A John
authors.initials: AJ
authors.lastname: Iafrate
authors.affiliation: Massachusetts General Hospital Cancer Center, Boston, Massachusetts. Department of Neurosurgery, Harvard Medical School, Boston, Massachusetts.
authors.forename: William T
authors.initials: WT
authors.lastname: Curry
authors.affiliation: Massachusetts General Hospital Cancer Center, Boston, Massachusetts.
authors.forename: Jay S
authors.initials: JS
authors.lastname: Loeffler
authors.affiliation: Massachusetts General Hospital Cancer Center, Boston, Massachusetts. Department of Neurology, Harvard Medical School, Boston, Massachusetts.
authors.forename: Tracy T
authors.initials: TT
authors.lastname: Batchelor
authors.affiliation: Massachusetts General Hospital Cancer Center, Boston, Massachusetts. Department of Pathology, Harvard Medical School, Boston, Massachusetts.
authors.forename: David N
authors.initials: DN
authors.lastname: Louis
authors.affiliation: Center for Engineering in Medicine, Harvard Medical School, Boston, Massachusetts. Department of Surgery, Harvard Medical School, Boston, Massachusetts.
authors.forename: Mehmet
authors.initials: M
authors.lastname: Toner
authors.affiliation: Massachusetts General Hospital Cancer Center, Boston, Massachusetts. Department of Surgery, Harvard Medical School, Boston, Massachusetts. maheswaran@helix.mgh.harvard.edu haber@helix.mgh.harvard.edu.
authors.forename: Shyamala
authors.initials: S
authors.lastname: Maheswaran
authors.affiliation: Massachusetts General Hospital Cancer Center, Boston, Massachusetts. Department of Medicine, Harvard Medical School, Boston, Massachusetts. Howard Hughes Medical Institute, Chevy Chase, Maryland. maheswaran@helix.mgh.harvard.edu haber@helix.mgh.harvard.edu.
authors.forename: Daniel A
authors.initials: DA
authors.lastname: Haber
mesh_terms: D000818:Animals; D014408:Biomarkers, Tumor / Q000097:blood; D001932:Brain Neoplasms / Q000097:blood / Q000473:pathology*; D058750:Epithelial-Mesenchymal Transition; D015870:Gene Expression; D005909:Glioblastoma / Q000097:blood / Q000473:pathology*; D006801:Humans; D051379:Mice; D009360:Neoplastic Cells, Circulating / Q000473:pathology*
chemical_list: D014408:Biomarkers, Tumor