Introduction: Preclinical models of glioblastoma that recapitulate the human disease are needed. GL261 are murine carcinogen-induced glioma cells that demonstrate profound proliferation, invasion, and angiogenesis when implanted in syngeneic C57BL/6 mice, providing a powerful immunocompetent animal model. Luciferase expression allows for non-invasive monitoring of tumor growth, as long as the insertion of the gene does not induce phenotypic changes.
Methods: GL261 cells were infected with a lentivirus containing the firefly luciferase gene (GL261.luc). Proliferation was measured at day 0, 1, 2, 4, and 7. Differences in 82 mouse cytokines and chemokines were analyzed by commercially available RT-PCR array. GL261 and GL261.luc cells were implanted intracranially in C57BL/6 mice. In vivo growth was measured by quantitative bioluminescence imaging bi-weekly and mice were followed for overall survival. Differences in continuous variables were compared by Student’s t-test. Kaplan-Meier curves estimated overall survival and log-rank test was used to compare differences.
Results: There was no difference in proliferation between wild-type GL261 and GL261.luc cells at any of the observed time points (p>0.05). Of the 82 genes tested, only 6 (7%) exhibited greater than or equal to 2-fold change with luciferase expression. These genes were BMP2, CSF2, CCL20, IL13, PF4, and TGFB2. When GL261.luc cells were implanted into C57BL/6 mice, luciferase activity steadily increased at day 5(5.7x10*4 p/sec/cm*2/sr), 8(4.8x10*4), 13(3.6x10*5), and 19(7.3x10*6). Median overall survival was 20.2 days in mice implanted with GL261 cells and 19.7 days in those with GL261.luc cells (p=0.62). We have successfully silenced the B7-H1 gene in GL261.luc cells and will use this to study its effect on the tumor microenvironment.
Conclusions: Luciferase expression in GL261 murine glioma cells does not affect cytokine expression or in vivo growth. This provides a powerful preclinical model to evaluate glioma biology and immunology.
Patient Care: The GL261.luc model can be used to evaluate the efficacy of immunotherapeutic modalities in the pre-clincal setting.
Learning Objectives: By the conclusion of this session, participants should be able to; 1)discuss the importance of immunocompetent mouse models of glioblastoma, 2)describe the effects of luciferase expression on immunologically important cytokine expression by GL261, 3)describe the applications of the GL261.luc model.