Spontaneous immune responses against glioma-associated antigens in a long term survivor with malignant glioma.

BACKGROUND: In patients with high grade glioma, little is known regarding existence of naturally occurring adaptive T cell reactivity against glioma-associated antigens (GAAs). In this report, we characterized GAA-specific CD8+ T cells and innate immune cells in a patient who has survived with anaplastic astrocytoma (AA) for over 12 years without recurrence. METHODS: Peripheral blood mononuclear cells (PBMCs) derived from the long term survivor with AA were evaluated for the frequency, cytotoxic T lymphocyte (CTL) activity and differentiation status of CD8+ cells recognizing GAA-derived epitopes as well as relative numbers of other immune cell subsets. This patient's AA tissue was evaluated for expression of two GAAs EphA2 and interleukin-13 receptor alpha2 subunit (IL-13Ralpha2) by immunohistochemistry. RESULTS: The patient's tumor expressed both EphA2 and IL-13Ralpha2, and in vitro stimulated PBMC demonstrated superior EphA2883-891 and IL-13Ralpha2345-353-specific CTL reactivity compared to PBMC samples from two other patients with progressing malignant glioma. Unstimulated EphA2883-891-reactive CD8+ T cells contained high numbers of CD45RA-/CCR7- late effector and CD45RA-/CCR7+ central memory cells. Among other leukocyte subsets, elevated numbers of NK-T cells were found. CONCLUSION: To our knowledge, the current study is one of the first demonstrating the presence of antigen-experienced, GAA-reactive CD8+ T cells in a patient who has survived with AA for over 12 years without recurrence. Further studies are warranted to determine whether the status of GAA-reactive CD8+ T cells dictates survival of patients and/or response to therapeutic vaccines.

Inhibition of STAT3 promotes the efficacy of adoptive transfer therapy using type-1 CTLs by modulation of the immunological microenvironment in a murine intracranial glioma.

A variety of cancers, including malignant gliomas, show aberrant activation of STAT3, which plays a pivotal role in negative regulation of antitumor immunity. We hypothesized that inhibition of STAT3 signals would improve the efficacy of T cell adoptive transfer therapy by reversal of STAT3-induced immunosuppression in a murine GL261 intracranial glioma model. In vitro treatment of GL261 cells with JSI-124, a STAT3 inhibitor, reversed highly phosphorylated status of STAT3. Systemic i.p. administration of JSI-124 in glioma-bearing immunocompetent mice, but not athymic mice, resulted in prolonged survival, suggesting a role of adaptive immunity in the antitumor effect. Furthermore, JSI-124 promoted maturation of tumor-infiltrating CD11c(+) dendritic cells and activation of tumor-conditioned cytotoxic T cells, enhanced dendritic cells and GL261 production of CXCL-10, a critical chemokine for attraction of Tc1 cells. When i.p. JSI-124 administration was combined with i.v. transfer of Pmel-I mouse-derived type-1 CTLs (Tc1), glioma-bearing mice exhibited prolonged survival compared with i.p. JSI-124 or i.v. Tc1 therapy alone. Flow cytometric analyses of brain infiltrating lymphocytes revealed that JSI-124-treatment enhanced the tumor-homing of i.v. transferred Tc1 cells in a CXCL-10-dependent fashion. Systemic JSI-124 administration also up-regulated serum IL-15 levels, and promoted the persistence of transferred Tc1 in the host. These data suggest that systemic inhibition of STAT3 signaling can reverse the suppressive immunological environment of intracranial tumor bearing mice both systemically and locally, thereby promoting the efficacy of adoptive transfer therapy with Tc1.

Expression of glioma-associated antigens in pediatric brain stem and non-brain stem gliomas.

We investigated the protein expression of three glioma-associated antigens (GAAs) in pediatric brain stem glioma (BSG) and non-brain stem glioma (NBSG) cases with a view to their possible use in immunotherapy. Expression of EphA2, IL-13Ralpha2 and Survivin were studied by immunohistochemistry on paraffin-embedded tissues using a series of 15 BSG cases and 12 NBSG cases. Thirteen of 15 BSGs and all 12 NBSGs expressed at least one of GAAs; and 7 BSGs and 9 NBSGs expressed at least two of these GAAs at higher levels than non-neoplastic brain. There was no association between the tumor grade and levels of GAA expression. Although many cases demonstrated diffuse expression of GAAs throughout specimens, partial or patchy expression was noted in a small number of cases, suggesting a need for targeting multiple GAAs in immunotherapy. These results suggest that EphA2, IL-13Ralpha2 and Survivin are suitable targets for developing vaccine strategies for pediatric glioma.