Experimental Study Of Treatment Of Intracranial G422 Glioblastoma With Bone Marrow-derived Dendritic Cells Pulsed With Tumor Extracts

Objective : To investigate the anti-tumor efficacy of dendritic cell (DC) -based vaccines pulsed with tumor extracts in an mice model of intracranial G422 glioblastoma and to discuss the feasibility of this active immunotherapy strategy for gliomas.Methods : Dendritic cells, the most potent antigen-presenting cells in the body, were isolated from mouse bone marrow precursors stimulated in vitro with granulocyte-macrophage colony-stimulating factor(GM-CSF) and interleukin-4. These dendritic cells were then pulsed ex vivo with tumor extracts.Tumor extracts were obtained from G422 glioblastoma by using a special ultrasonic cleaner. 104 adult female mouse were treated with three weekly spaced one week apart subcutaneous injections of either PBS, unpulsed dendritic cells, G422 tumor extracts, or dendritic cells pulsed with G422 tumor extracts. 7 days after the third immunization , spleens of 24 mouse were harvested for cell-mediated cytotoxicity assays and other 80 mouse were challenged in the brain with G422 tumor cells. Another 80 adult female mouse harboring 4-day-old intracranial G422 glioblastomas were treated with three weekly spaced one week apart subcutaneous injections of either PBS, unpulsed dendritic cells, G422 tumor extracts,or dendritic cells pulsed with G422 tumor extracts. These mouse were followed for survival. The mouse brains were removed and examined pathologically when they died. Survival estimates and median survival were determined using the method of Kaplan and Meier. The method ofStudent-Newman-Keuls was used for calculating the significance of cytotoxic activity.Results : Immunization using dendriric cells pulsed with tumor extracts induced G422-specific CTL responses that were statistically significant compared with mouse treated with PBS, impulsed dendritic cells or G422 tumor extracts(PO.Ol). One group of mouse were challenged with G422 tumor cells after received either PBS, impulsed dendritic cells, G422 tumor extracts, or dendritic cells pulsed with G422 tumor extracts. No mouse in the control group survived for more than 30 days and the survival times were (21.42+1. 86), (24.00 + 2.36) and (22.25 + 1.89) days, respectively. In contrast,significantly prolonged survival was observed in the tumor extract-pulsed dendritic cell-treated group [survival time (32.42 + 3.80) days], with 60.0% mouse surviving for more than 30 days(P<0.01).The survival of intracranial tumor-bearing mouse injected sudcutaneously with the syngeneic bone marrow-derived dendritic cells pulsed with tumor extracts was significantly prolonged relative to the survival of mouse receiving PBS, unpulsed dendriric cells,or tumor extracts(P<0.05). 35.0% mouse treatment with tumor extract-pulsed dendritic cells were alive at 25 days whereas none of the control groups survived past 25 days. Mouse treated with PBS, unpulsed dendritic cells, or tumor extracts had survival times of (17.00+1.62),(17.58+ 1. 80) and (16.92 + 2. 20) days, respectively. In contrast,mouse in the tumor extract-pulsed dendritic cell-treated group had a significantly longer survival time of (22.00 + 3. 12) days.Conclusion : Based on these results , dendtitic cells pulsed with tumor extracts derived from autologous tumors represent a promising approch to the immunotherapy of gliomas , which can specifically activate antitumor T cells and lead to significantly prolonged survival in tumor -bearing animals. This may therefore be a useful approach treatment of gliomas in humans in the future.