Tumor Treating Fields dually activate STING and AIM2 inflammasomes to induce adjuvant immunity in glioblastoma.

Dongjiang Chen,Son B Le,Maryam Rahman,Tarun E Hutchinson,Tianyi Liu,Ashley Ghiaseddin,Anda-Alexandra Calinescu,David D Tran,Dan Jin,Mathew Sebastian

doi:10.1172/jci149258

Abstract

Tumor Treating Fields (TTFields), an approved therapy for glioblastoma (GBM) and malignant mesothelioma, employ noninvasive application of low-intensity, intermediate-frequency, alternating electric fields to disrupt the mitotic spindle, leading to chromosome missegregation and apoptosis. Emerging evidence suggests that TTFields may also induce inflammation. However, the mechanism underlying this property and whether it can be harnessed therapeutically are unclear. Here, we report that TTFields induced focal disruption of the nuclear envelope, leading to cytosolic release of large micronuclei clusters that intensely recruited and activated 2 major DNA sensors — cyclic GMP-AMP synthase (cGAS) and absent in melanoma 2 (AIM2) — and their cognate cGAS/stimulator of interferon genes (STING) and AIM2/caspase 1 inflammasomes to produce proinflammatory cytokines, type 1 interferons (T1IFNs), and T1IFN-responsive genes. In syngeneic murine GBM models, TTFields-treated GBM cells induced antitumor memory immunity and a cure rate of 42% to 66% in a STING- and AIM2-dependent manner. Using single-cell and bulk RNA sequencing of peripheral blood mononuclear cells, we detected robust post-TTFields activation of adaptive immunity in patients with GBM via a T1IFN-based trajectory and identified a gene panel signature of TTFields effects on T cell activation and clonal expansion. Collectively, these studies defined a therapeutic strategy using TTFields as cancer immunotherapy in GBM and potentially other solid tumors.

Highlights

GBM is the most common and lethal brain cancer in adults and one of the least immunogenic tumors [1]
Large cGAS and AIM2-recruited cytosolic micronuclei clusters were observed in the human lung and pancreatic adenocarcinoma cell lines A549 and PANC-1, respectively, after a 24-hr exposure to TTFields at 150 kHz (Fig. S4A, C), suggesting that this phenomenon is common in tumor cells and may manifest TTFields’ general effects on the nuclear envelope
Consistent with TTFields inducing the immune system via a T1IFNbased trajectory and with the findings in the tumor microenvironment (TME) of KR158 and GL261 models, we discovered in post-TTFields peripheral blood mononuclear cells (PBMCs) higher proportions of pDCs (C31) (Figs. 12B; S19A) and a monocyte subtype (C17) expressing T1IFN-responsive genes (T1IRGs) (e.g., IFI44L, MX1 and ISG15) (Figs. 12C; S19B)

Summary

Introduction

GBM is the most common and lethal brain cancer in adults and one of the least immunogenic tumors [1]. Besides systemic T lymphopenia and anergy and dysfunctional cytokine profiles among others, GBM tumors possess a profoundly immunosuppressed or “cold” tumor microenvironment (TME), characterized by scant tumor infiltrating lymphocytes (TILs) and an abundance of inhibitory cells including myeloid derived suppressor cells (MDSCs) and regulatory T cells (Tregs). The blood brain barrier (BBB) diminishes exposure of tumor-associated neoantigens to immune cells and vice versa, severely hindering immunotherapeutic efforts [2]. Overcoming these hurdles promises a long-lasting, multilayered, immune-mediated tumor control. To “heat up” the cold GBM TME, recent efforts have focused on tumor cell-extrinsic pathways with mixed results, such as dendritic cell (DC)-based vaccination, immune checkpoint blockade, re-wiring the cytokine milieu or disrupting BBB integrity to recruit tumor-specific cytotoxic T lymphocytes (CTLs) [4]. It remains a challenge to leverage a direct, active role of tumor cells in reversing the immunosuppressive state of the GBM TME

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Conclusion