title: Induction of antitumor immunity by intracerebrally implanted rat C6 glioma cells genetically engineered to secrete cytokines.
abstract: To test whether cytokine gene therapy can be applied to an immunologically privileged site, such as the brain, we investigated antitumor immunity in the brain induced by cytokine-secreting glioma cells. Three cytokine genes, interleukin-2 (IL-2), interleukin-4 (IL-4), and granulocyte-macrophage colony-stimulating factor (GM-CSF) were transduced into a rat C6 glioma cell line via a retroviral vector, S2. Rats intracerebrally (IC) implanted with the C6 cells genetically engineered to secrete the cytokines, especially GM-CSF, manifested significantly higher survival rates than those with C6 cells or with C6 cells bearing the control vector (p < 0.002). In vivo, C6 tumors bearing the cytokine genes grew more slowly than wild-type tumors at any time point, and eventually diminished within 6 weeks after tumor cell implantation. Histopathological and immunohistochemical studies revealed that different cytokines induced diverse immune reactions. In the IL-2 group, CD4+ and CD8+ T cells dominated from day 3 to week 4, but disappeared at week 6. Some granulocytes were noted between weeks 2 and 4. In the IL-4 group, eosinophils were noted from day 3 to week 4, and CD4+ and CD8+ T cells, as well as macrophages at week 2. At week 6, only residual levels of macrophages and CD8+ T cells remained. In the GM-CSF group, granulocytes appeared as early as day 1 post-IC tumor implantation, and macrophages at day 2. CD4+ and CD8+ T cells were found from day 3 to week 4. At week 6, only residual CD4+ T cells and macrophages remained. Long-lasting antitumor immunity was confirmed in all groups by rechallenging surviving rats with wild-type C6 cells in the brain 100 days after implanting cytokine gene-bearing C6 cells. In vivo depletion of GM-CSF by anti-GM-CSF antibody further confirmed that the immune reaction induced by GM-CSF-secreting tumor cells were mainly from the action of GM-CSF, rather than the immunogenicity of C6 cells.
authors.affiliation: Department of Surgery, National Taiwan University Hospital, Taipei, R.O.C.
authors.forename: S H
authors.initials: SH
authors.lastname: Tseng
authors.forename: L H
authors.initials: LH
authors.lastname: Hwang
authors.forename: S M
authors.initials: SM
authors.lastname: Lin
mesh_terms: D000818:Animals; D001932:Brain Neoplasms / Q000235:genetics / Q000276:immunology* / Q000401:mortality / Q000473:pathology / Q000628:therapy; D018014:Gene Transfer Techniques; D015316:Genetic Therapy; D005822:Genetic Vectors / Q000235:genetics; D005910:Glioma / Q000235:genetics / Q000276:immunology* / Q000401:mortality / Q000473:pathology / Q000628:therapy; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000037:antagonists & inhibitors / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D007376:Interleukin-2 / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D015847:Interleukin-4 / Q000235:genetics / Q000276:immunology*; D016246:Lymphocytes, Tumor-Infiltrating; D051381:Rats; D017208:Rats, Wistar; D012190:Retroviridae / Q000235:genetics; D016019:Survival Analysis; D014407:Tumor Cells, Cultured
chemical_list: D007376:Interleukin-2; D015847:Interleukin-4; D016178:Granulocyte-Macrophage Colony-Stimulating Factor