Tumor antigens in glioma.

Immunotherapy applications to glioblastoma represent a new treatment frontier. Antigen-targeted immunotherapy approaches hold enormous potential to elicit antigen-specific anti-tumor effects in central nervous system tumors. Still, the paucity of effective antigen targets remains a significant obstacle in safely and effectively treating glioblastoma and other malignant gliomas with relatively low mutation loads. In this review, we highlight the current understanding of and development of immunotherapy to target 1) shared non-mutant antigens 2) shared mutant antigens (neoantigens) derived from cancer-specific mutations 3) personalized neoantigens derived from tumor-specific genetic alterations containing de novo peptide sequences and 4) virus-derived antigens. We also discuss strategies to enhance tumor immunogenicity and neoantigen prediction. Spatial heterogeneity remains a formidable challenge for immunotherapy of glioma; recent advances in targeting multiple antigens and refining the antigen selection pipeline hold great promise to turn the tide against glioma.

SynNotch-CAR T cells overcome challenges of specificity, heterogeneity, and persistence in treating glioblastoma.

Treatment of solid cancers with chimeric antigen receptor (CAR) T cells is plagued by the lack of ideal target antigens that are both absolutely tumor specific and homogeneously expressed. We show that multi-antigen prime-and-kill recognition circuits provide flexibility and precision to overcome these challenges in the context of glioblastoma. A synNotch receptor that recognizes a specific priming antigen, such as the heterogeneous but tumor-specific glioblastoma neoantigen epidermal growth factor receptor splice variant III (EGFRvIII) or the central nervous system (CNS) tissue-specific antigen myelin oligodendrocyte glycoprotein (MOG), can be used to locally induce expression of a CAR. This enables thorough but controlled tumor cell killing by targeting antigens that are homogeneous but not absolutely tumor specific. Moreover, synNotch-regulated CAR expression averts tonic signaling and exhaustion, maintaining a higher fraction of the T cells in a naïve/stem cell memory state. In immunodeficient mice bearing intracerebral patient-derived xenografts (PDXs) with heterogeneous expression of EGFRvIII, a single intravenous infusion of EGFRvIII synNotch-CAR T cells demonstrated higher antitumor efficacy and T cell durability than conventional constitutively expressed CAR T cells, without off-tumor killing. T cells transduced with a synNotch-CAR circuit primed by the CNS-specific antigen MOG also exhibited precise and potent control of intracerebral PDX without evidence of priming outside of the brain. In summary, by using circuits that integrate recognition of multiple imperfect but complementary antigens, we improve the specificity, completeness, and persistence of T cells directed against glioblastoma, providing a general recognition strategy applicable to other solid tumors.