Treatment of intracranial gliomas with bone marrow-derived dendritic cellspulsed with tumor antigens

Object. An approach toward the treatment of intracranial gliomas was develo ped in a rat experimental model. The authors investigated the ability of "p rofessional" antigen-presenting cells (dendritic cells) to enhance host ant itumor immune responses when injected as a vaccine into tumor-bearing anima ls. Methods. Dendritic cells, the most patent antigen-presenting cells in the b ody, were isolated from rat bone marrow precursors stimulated in vitro with granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin- 4. Cultured cell populations were confirmed to be functional antigen-presen ting cells on the basis of expressed major histocompatibility molecules, as analyzed by fluorescence-activated cell sorter cytofluorography. These den dritic cells were then pulsed (cocultured) ex vivo with acid-eluted tumor a ntigens from 9L glioma cells. Thirty-eight adult female Fischer 344 rats ha rboring 7-day-old intracranial 9L tumors were treated with three weekly sub cutaneous injections of either control media (10 animals), unpulsed dendrit ic cells (six animals), dendritic cells pulsed with peptides extracted from normal rat astrocytes (10 animals), or 9L tumor antigen-pulsed dendritic c ells (12 animals). The animals were followed for survival. At necropsy, the rat brains were removed and examined histologically, and spleens were harv ested for cell-mediated cytotoxicity assays. The results indicate that tumor peptide-pulsed dendritic cell therapy led t o prolonged survival in rats with established intracranial 9L tumors implan ted 7 days prior to the initiation of vaccine therapy in vivo. Immunohistoc hemical analyses were used to document a significantly increased perilesion al and intratumoral infiltration of CD8(+) and CD4(+) cells in the groups t reated with tumor antigen-pulsed dendritic cells compared with the control groups. In addition. the results of in vitro cytotoxicity assays suggest th at vaccination with these peptide-pulsed dendritic cells can induce specifi c cytotoxic T lymphocytes against 9L tumor cells. Conclusions. Based on these results, dendritic antigen-presenting cells pul sed with acid-eluted peptides derived from autologous tumors represent a pr omising approach to the immunotherapy of established intracranial gliomas. which may serve as a basis for designing clinical trials in patients with b rain tumors.