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The promise of adaptive cancer immunotherapy in treating highly malignant tumors such as glioblastoma multiforme (GBM) can only be realized through expanding its benefits to more patients. Alleviating various modes of immune suppression has so far failed to achieve such expansion, but exploiting endogenous immune enhancers among mutated cancer genes could represent a more direct approach to immunotherapy improvement. We found that Isocitrate Dehydrogenase-1 (IDH1), which is commonly mutated in gliomas, enhances glioma vaccine efficacy in mice and discerns long from short survivors after vaccine therapy in GBM patients. Extracellular IDH1 directly enhanced T cell responses to multiple tumor antigens, and prolonged experimental glioma cell lysis. Moreover, IDH1 specifically bound to and exhibited sialidase activity against CD8. By contrast, mutant IDH1R132H lacked sialidase activity, delayed killing in glioma cells, and decreased host survival after immunotherapy. Overall, our findings identify IDH1 as an immunotherapeutic enhancer that mediates the known T cell-enhancing reaction of CD8 desialylation. This uncovers a new axis for immunotherapeutic improvement in GBM and other cancers, reveals novel physiological and molecular functions of IDH1, and hints at an unexpectedly direct link between lytic T cell function and metabolic activity in target cells., (© 2023. The Author(s).)

Tyrosinase-related protein (TRP)-2 is not only expressed on glioma cells, but is naturally processed and presented by their surface MHC molecules and is recognized by TRP-2-specific cytotoxic T cells. After active immunotherapy, we detected TRP-2-specific cytotoxic T lymphocyte (CTL) activity in patients' peripheral blood mononuclear cells (PBMC). Tumor cells from postvaccination resections showed significantly lower TRP-2 expression and higher sensitivity to carboplatin and temozolomide than those autologous cell lines from prevaccination resections in two patients who demonstrated CTL response to TRP-2. One of two patients underwent treatment with temozolomide after recurrence and responded dramatically. TRP-2-transfected cell line (TRP-2-U373) resulted in significant drug resistance to carboplatin and temozolomide compared to wild-type U-373 (W-U373). There was no significant difference, however, in the mRNA expression of other common drug resistance related proteins, such as BCRP-1, MGMT, MDR-1, MRP-1 and MRP-3, after TRP-2 transfection. TRP-2-U373 tumor cells were immunoselected by a TRP-2-specific CTL line. The immunoselected cells (IS-TRP-2-U373) demonstrated significantly increased sensitivity to carboplatin and temozolomide compared to TRP-2-U373. For the first time, we provide evidence that immunological targeting of tumor-associated antigen TRP-2 significantly increases sensitivity to chemotherapy.

Interleukin 12 (IL-12) isa cytokine that promotesan antitumor Th1-type pattern of differentiation in mature naïveT cells. Despite its therapeutic success in multiple animal models of cancer, the utility of systemically administered recombinant cytokine has been limited by its toxicity. This has encouraged the development of local IL-12 delivery systems through gene transfer. To determine the effect of local adenoviral delivery of IL- 12 on glioma immunogenicity, mice bearing GL-26 gliomas in the right corpus striatum were treated with direct intratumoral administration of AdmIL-12, AdLacZ, or normal saline. Survival was significantly prolonged in AdmIL-12-treated animals and immunohistochemistry demonstrated robust CD4+ and CD8+ T-cell infiltration in these mice compared to the two control groups. Glioma-infiltrating T lymphocytes from mice that received AdmIL-12 also demonstrated relatively increased, albeit statistically nonsignificant tumor killing. Based on IL-12's known ability to enhance Th1-type cytotoxic antitumor immune responses, we postulate our findings to be a result of localized induction of tumor immunity.

Mature T cells can be functionally divided into two categories distinguished by surface expression of either CD4 or CD8, which in turn corresponds to restriction by and binding to class II or class I major histocompatibility complex proteins, respectively. CD8 can be expressed as a homodimer of the alpha-chain, or as a heterodimer of alpha- and beta-chains on human and mouse T cells, although most peripheral T cells seem to express CD8 alpha beta heterodimers exclusively (reviewed in ref. 9). Functional characterization of CD8 has focused primarily on the effect of the alpha-chain, which enhances or reconstitutes T-cell responses in homodimeric form and may play a specific role in thymic selection. In contrast, no role has been ascribed to CD8 beta or alpha beta heterodimers specifically. Here we show that CD8 alpha beta transfectants produce more interleukin-2 than CD8 alpha transfectants in response to specific stimuli. Increased interleukin-2 is also observed in cells expressing hybrid CD8 beta-alpha molecules (extracellular CD8 beta plus CD8 alpha transmembrane and cytoplasmic regions) on their surface. These results indicate that external portions of CD8 beta could be critical and that they may act independently of CD8 alpha in mediating their augmentation effect.

Patchwork homology observed between divergent members of polymorphic multigene families is thought to reflect evolution by short-tract gene conversion (nonreciprocal recombination), although this mechanism cannot usually be confirmed in higher organisms. In contrast to meiotic conversions observed in laboratory yeast strains, apparent conversions between polymorphic sequences, such as the class I loci of the major histocompatibility complex (MHC), are short and do not seem to be associated with reciprocal recombination (crossover, exchanges). We have now integrated two nonallelic murine class I genes into yeast to characterize their meiotic recombination. We found no crossovers between the MHC genes, but short-tract 'microconversions' of 1-215 base-pairs were observed in about 6% of all meioses. Strikingly, one of these events was accompanied by a single base-pair mutation. These results underscore both the importance of meiotic gene conversion and sequence heterology in determining conversion patterns between divergent genes.