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Isaac Yang, Thomas J. Kremen, Adrian J. Giovannone, Elena Paik, Sylvia K. Odesa, Robert M. Prins and Linda M. Liau

Object

Little is known about the quantitative modulation of major histocompatibility complex (MHC) Class I expression on human gliomas that is effected by interferons; even less is known about the immunogenic peptides that are accommodated in the peptide-binding motifs of MHC Class I alleles in these brain tumors. In this article the authors investigated the ability of interferon (IFN)α and IFNγ to upregulate MHC Class I expression and to modulate acid-eluted Class I—bound peptides on human glioblastoma multiforme (GBM) cells in vitro.

Methods

Early-passage primary human GBM cell cultures and U87MG GBM cells were incubated with varying doses of INFα or IFNγ ranging between 0 and 2000 U/ml. Upregulation of MHC Class I expression was assayed by immunocytochemical analysis, flow cytometry, and Western blot analysis. Modulation of acid-eluted MHC Class I—bound peptides from the IFN-treated GBM cells was examined with the aid of mass spectroscopy.

The in vitro expression of the MHC Class I molecule was upregulated by both IFNα and IFNγ in a dose-dependent manner. Interferon-γ exhibited a more potent effect on MHC Class I upregulation, peaking at 10 U/ml; whereas the effect of IFNα was less marked, reaching a plateau at 500 U/ml. In addition, a native peptide eluted from MHC Class I molecules of human GBM cells was identified and found to be consistently upregulated by IFN treatment.

Conclusions

Interferon-α and IFNγ can significantly upregulate the MHC Class I molecules that are expressed on the cell surface of human GBM cells as well as the potentially immunogenic peptides bound to the MHC. These results may help explain the molecular basis for increased immunogenicity with IFN treatment of human GBMs and might provide added insight into the design of future antitumor vaccines for human brain tumors.

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Linda M. Liau, Keith L. Black, Robert M. Prins, Steven N. Sykes, Pier-Luigi DiPatre, Timothy F. Cloughesy, Donald P. Becker and Jeff M. Bronstein

Object. An approach toward the treatment of intracranial gliomas was developed in a rat experimental model. The authors investigated the ability of “professional” antigen-presenting cells (dendritic cells) to enhance host antitumor immune responses when injected as a vaccine into tumor-bearing animals.

Methods. Dendritic cells, the most potent antigen-presenting cells in the body, 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-presenting cells on the basis of expressed major histocompatibility molecules, as analyzed by fluorescence-activated cell sorter cytofluorography. These dendritic cells were then pulsed (cocultured) ex vivo with acid-eluted tumor antigens from 9L glioma cells. Thirty-eight adult female Fischer 344 rats harboring 7-day-old intracranial 9L tumors were treated with three weekly subcutaneous injections of either control media (10 animals), unpulsed dendritic cells (six animals), dendritic cells pulsed with peptides extracted from normal rat astrocytes (10 animals), or 9L tumor antigen—pulsed dendritic cells (12 animals). The animals were followed for survival. At necropsy, the rat brains were removed and examined histologically, and spleens were harvested for cell-mediated cytotoxicity assays.

The results indicate that tumor peptide-pulsed dendritic cell therapy led to prolonged survival in rats with established intracranial 9L tumors implanted 7 days prior to the initiation of vaccine therapy in vivo. Immunohistochemical analyses were used to document a significantly increased perilesional and intratumoral infiltration of CD8+ and CD4+ T cells in the groups treated with tumor antigen—pulsed dendritic cells compared with the control groups. In addition, the results of in vitro cytotoxicity assays suggest that vaccination with these peptide-pulsed dendritic cells can induce specific cytotoxic T lymphocytes against 9L tumor cells.

Conclusions. Based on these results, dendritic antigen-presenting cells pulsed with acid-eluted peptides derived from autologous tumors represent a promising approach to the immunotherapy of established intracranial gliomas, which may serve as a basis for designing clinical trials in patients with brain tumors.