title: Stable luciferase expression does not alter immunologic or in vivo growth properties of GL261 murine glioma cells.
abstract: BACKGROUND
  GL261 cells are murine glioma cells that demonstrate proliferation, invasion, and angiogenesis when implanted in syngeneic C57BL/6 mice, providing a highly useful immunocompetent animal model of glioblastoma. Modification of tumor cells for luciferase expression enables non-invasive monitoring of orthotopic tumor growth, and has proven useful for studying glioblastoma response to novel therapeutics. However, tumor modification for luciferase has the potential for evoking host immune response against otherwise syngeneic tumor cells, thereby mitigating the tumor cells' value for tumor immunology and immunotherapy studies.
  
  
  METHODS
  GL261 cells were infected with lentivirus containing a gene encoding firefly luciferase (GL261.luc). In vitro proliferation of parental (unmodified) GL261 and GL261.luc was measured on days 0, 1, 2, 4, and 7 following plating, and the expression of 82 mouse cytokines and chemokines were analyzed by RT-PCR array. Cell lines were also evaluated for differences in invasion and migration in modified Boyden chambers. GL261 and GL261.luc cells were then implanted intracranially in C57BL/6 mice, with GL261.luc tumor growth monitored by quantitative bioluminescence imaging, and all mice were followed for survival to compare relative malignancy of tumor cells.
  
  
  RESULTS
  No difference in proliferation was indicated for GL261 vs. GL261.luc cells (p>0.05). Of the 82 genes examined by RT-PCR array, seven (9%) exhibited statistically significant change after luciferase modification. Of these, only three changed by greater than 2-fold: BMP-2, IL-13, and TGF-β2. No difference in invasion (p=0.67) or migration (p=0.26) was evident between modified vs. unmodified cells. GL261.luc cell luminescence was detectable in the brains of C57BL/6 mice at day 5 post-implantation, and tumor bioluminescence increased exponentially to day 19. Median overall survival was 20.2 days versus 19.7 days for mice receiving implantation with GL261 and GL261.luc, respectively (p=0.62). Histopathologic analysis revealed no morphological difference between tumors, and immunohistochemical analysis showed no significant difference for staining of CD3, Ki67, or CD31 (p>0.05 for all).
  
  
  CONCLUSIONS
  Luciferase expression in GL261 murine glioma cells does not affect GL261 proliferation, invasion, cytokine expression, or in vivo growth. Luciferase modification increases their utility for studying tumor immunology and immunotherapeutic approaches for treating glioblastoma.
authors.affiliation: The Brain Tumor Research Center, Department of Neurological Surgery, University of California, San Francisco, CA 505 Parnassus Ave., Room 779 M, San Francisco, CA, 94143-0112, USA. aaronclark8833@gmail.com.|Department of Neurological Surgery, University of California, San Francisco, 505 Parnassus Ave., M779, Box 0112, San Francisco, CA, 94117, USA. aaronclark8833@gmail.com.
authors.forename: Aaron J
authors.initials: AJ
authors.lastname: Clark
authors.affiliation: The Brain Tumor Research Center, Department of Neurological Surgery, University of California, San Francisco, CA 505 Parnassus Ave., Room 779 M, San Francisco, CA, 94143-0112, USA. michaelsafaee@gmail.com.
authors.forename: Michael
authors.initials: M
authors.lastname: Safaee
authors.affiliation: Department of Neurological Surgery, Northwestern University, Feinberg School of Medicine, 676 N. St. Clair St., Suite 2210, Chicago, IL, 60611-2922, USA. taemin.oh@northwestern.edu.
authors.forename: Taemin
authors.initials: T
authors.lastname: Oh
authors.affiliation: The Brain Tumor Research Center, Department of Neurological Surgery, University of California, San Francisco, CA 505 Parnassus Ave., Room 779 M, San Francisco, CA, 94143-0112, USA. michaeleivan@gmail.com.
authors.forename: Michael E
authors.initials: ME
authors.lastname: Ivan
authors.affiliation: Pathology Core Facility, Feinberg School of Medicine, Northwestern University, 710 N. Fairbanks Court, Room 8-419, Chicago, IL, USA. v-parini@northwestern.edu.
authors.forename: Vamsi
authors.initials: V
authors.lastname: Parimi
authors.affiliation: Department of Neurological Surgery, Northwestern University, Feinberg School of Medicine, 676 N. St. Clair St., Suite 2210, Chicago, IL, 60611-2922, USA. rintaro.hashizume@northwestern.edu.
authors.forename: Rintaro
authors.initials: R
authors.lastname: Hashizume
authors.affiliation: The Brain Tumor Research Center, Department of Neurological Surgery, University of California, San Francisco, CA 505 Parnassus Ave., Room 779 M, San Francisco, CA, 94143-0112, USA. tomoko.ozawa@ucsf.edu.
authors.forename: Tomoko
authors.initials: T
authors.lastname: Ozawa
authors.affiliation: Department of Neurological Surgery, Northwestern University, Feinberg School of Medicine, 676 N. St. Clair St., Suite 2210, Chicago, IL, 60611-2922, USA. charles.james@northwestern.edu.
authors.forename: Charles D
authors.initials: CD
authors.lastname: James
authors.affiliation: Department of Neurological Surgery, Northwestern University, Feinberg School of Medicine, 676 N. St. Clair St., Suite 2210, Chicago, IL, 60611-2922, USA. orin.bloch@northwestern.edu.
authors.forename: Orin
authors.initials: O
authors.lastname: Bloch
authors.affiliation: Department of Neurological Surgery, Northwestern University, Feinberg School of Medicine, 676 N. St. Clair St., Suite 2210, Chicago, IL, 60611-2922, USA. aparsa@nmff.org.
authors.forename: Andrew T
authors.initials: AT
authors.lastname: Parsa
mesh_terms: D000818:Animals; D001932:Brain Neoplasms / Q000276:immunology / Q000473:pathology*; D002455:Cell Division; D045744:Cell Line, Tumor; D016207:Cytokines / Q000276:immunology; D005910:Glioma / Q000276:immunology / Q000473:pathology*; D008156:Luciferases / Q000235:genetics*; D051379:Mice
chemical_list: D016207:Cytokines; D008156:Luciferases