Immunization with dendritic cells pulsed with tumor extract increases survival of mice bearing intracranial gliomas

The purpose of this study is to investigate the efficacy of dendritic cell-mediated immunotherapy against intracranial gliomas. Cloned DC2.4 dendritic cells originating from C57BL/6 mice were pulsed with glioma GL261 cell extracts and administered i.p. to C57BL/6 mice with intracranial GL261 gliomas. The survival of mice with and without pulsed dendritic cells was monitored after intracranial implantation of the GL261 glioma cells. Fluorescence activated cell sorting (FACS) analysis showed that DC2.4 cells express high levels of MHC class I and class II molecules, costimulatory molecules B7-1 and B7-2, and the cell adhesion molecule ICAM-1. Antigen-presenting capabilities in these dendritic cells were initially characterized in vitro by a mixed lymphocyte reaction, showing that Balb/c CD4(+) and CD8(+) T cells were able to generate allogeneic responses to DC2.4 cells. Tumor extract-pulsed DC2.4 dendritic cells were then used for the treatment of C57BL/6 mice with syngeneic GL261 gliomas. Animals with intracranial GL261 gliomas and vaccinated i.p. with pulsed DC2.4 dendritic cells exhibited significantly enhanced survival, relative to animals treated with saline or non-pulsed DC2.4 cells alone. In addition, cured animals showed an increased delayed-type hypersensitivity response to GL261 cells and survived when rechallenged with intracranial GL261 gliomas. In summary these results indicate that dendritic cells pulsed with tumor extract can enhance immune responses to tumor antigen and therefore represent a potential immunotherapeutic approach for treating patients with intracranial gliomas.