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

Our plain-English summary of Tumor Treating Fields dually activate STING and AIM2 inflammasomes to induce adjuvant immunity in glioblastoma, by D. Chen, S.B. Le, T.E. Hutchinson, et al (The Journal of Clinical Investigation, 2022).

The study

• Authors: D. Chen, S.B. Le, T.E. Hutchinson, A.A. Calinescu, M. Sebastian, D. Jin, T. Liu, A. Ghiaseddin, M. Rahman, D.D. Tran
• Journal: The Journal of Clinical Investigation
• Published: 2022;132(8)
• Cited by: 136 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

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.

In plain English

This laboratory and clinical research article studied Tumor Treating Fields (TTFields), low-intensity alternating electric fields used to treat glioblastoma, a brain cancer. It did not study asbestos; mesothelioma was mentioned only as another approved use. In 4 patient-derived and 3 established human glioblastoma cell lines, 24 hours of TTFields produced large clusters of DNA outside the cell nucleus at 5- to greater than 50-fold higher frequency than in untreated cells. These clusters recruited two DNA-sensing proteins, cGAS and AIM2. In two mouse models, brain implants of TTFields-treated tumor cells left mice with no detectable tumor: 10 of 15 (66%) on day 100 in the KR158-luc model and 5 of 12 (42%) on day 50 in the GL261-luc model. In the control groups, 38 of 39 and 28 of 28 mice developed progressive tumors and died. In 12 patients with newly diagnosed glioblastoma, blood taken before and about 4 weeks after starting TTFields showed signs of T-cell clonal expansion in 9. The authors concluded that TTFields could serve as cancer immunotherapy. They also said they could not rule out a contribution from the chemotherapy drug temozolomide in the patients.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Laboratory study in human glioblastoma cell lines, animal experiments in two mouse glioblastoma models, and a before-and-after blood study in patients treated with TTFields
• Who was studied: 4 patient-derived glioblastoma stem-like cell lines and 3 human glioblastoma cell lines; C57BL/6J mice implanted with KR158 or GL261 glioblastoma cells; 12 adult patients with newly diagnosed glioblastoma at the University of Florida
• Exposure: Tumor Treating Fields (alternating electric fields, 200 kHz unless otherwise noted) applied to cells for 24 hours, or for 72 hours before implantation into mice. In patients, TTFields were given with maintenance temozolomide, with a median compliance of 86% of total time over 4 weeks. Asbestos was not studied.
• Main results:
  • In all 7 human glioblastoma cell lines treated with TTFields, large cytosolic micronuclei clusters were seen at 5- to greater than 50-fold higher frequency than in nontreated cells.
  • Mice implanted with TTFields-treated cells carrying normal STING and AIM2 (scrambled shRNA): 10 of 15 (66%) in the KR158-luc model had no detectable tumor on day 100, and 5 of 12 (42%) in the GL261-luc model had no detectable tumor on day 50.
  • In the 3 control groups (untreated cells, or cells with both STING and AIM2 knocked down, with or without TTFields), 38 of 39 (97%) KR158-luc mice and 28 of 28 (100%) GL261-luc mice developed progressive brain tumors and died.
  • When surviving TTFields-immunized mice were rechallenged with twice the number of tumor cells, 6 of 10 (60%) KR158-luc mice and 4 of 5 (80%) GL261-luc mice survived for at least 140 and 125 more days without detectable tumors. None of the 12 naive control mice in each model survived past 45 and 27 days.
  • In the 12 patients, 9 showed a negative change in the T-cell receptor (TCRB) diversity index after TTFields, which the authors interpreted as clonal expansion.
  • In patients, blood taken after TTFields contained higher proportions of plasmacytoid dendritic cells. In the 9 patients with a full plasmacytoid dendritic cell data set, the change in their proportion was moderately negatively correlated with the TCRB diversity index change (Spearman r = –0.608, P = 0.04).
• The authors' conclusion: The authors concluded that these studies defined a therapeutic strategy using TTFields as cancer immunotherapy in glioblastoma and potentially other solid tumors.
• Limitations the authors state:
  • The authors could not rule out a contribution by temozolomide, or delayed immune changes following radiotherapy and temozolomide, to the effects observed in the patient cohort.
  • The authors could not rule out a minor contribution from late apoptosis caused by TTFields to the LDH release measured in cells.
  • The method used to extract T-cell receptor sequences captured only a fraction of the T-cell receptor diversity compared with traditional target-specific sequencing.

Topics

Medical terms in this study, explained in our Lexicon: Tumor Treating Fields (TTFields), Mesothelioma, Apoptosis, Inflammation, Micronuclei, Cytokine, Immunotherapy.

Related studies

• The safety profile of Tumor Treating Fields (TTFields) therapy in glioblastoma patients with ventriculoperitoneal shunts — N.A. Oberheim-Bush, W. Shi, et al. (2022)
• Tumour treating fields therapy for glioblastoma: current advances and future directions — O. Rominiyi, A. Vanderlinden, et al. (2021)
• The Mechanisms of Action of Tumor Treating Fields — J.C. Moser, E. Salvador, et al. (2022)
• A review of tumor treating fields (TTFields): advancements in clinical applications and mechanistic insights — X. Li, K. Liu, et al. (2023)
• Real-Time Monitoring of the Effect of Tumour-Treating Fields on Cell Division Using Live-Cell Imaging — H.T. Le, M. Staelens, et al. (2022)
• Prevention and Management of Dermatologic Adverse Events Associated With Tumor Treating Fields in Patients With Glioblastoma — M.E. Lacouture, M.J. Anadkat, et al. (2020)

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