Antimesothelioma Immunotherapy by CTLA-4 Blockade Depends on Active PD1-Based TWIST1 Vaccination

Our plain-English summary of Antimesothelioma Immunotherapy by CTLA-4 Blockade Depends on Active PD1-Based TWIST1 Vaccination, by Z. Tan, M.S. Chiu, C.W. Yan, et al (Molecular Therapy Oncolytics, 2020).

The study

• Authors: Z. Tan, M.S. Chiu, C.W. Yan, Y.C. Wong, H. Huang, K. Man, Z. Chen
• Journal: Molecular Therapy Oncolytics
• Published: 2020;16:302-317
• Cited by: 11 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Checkpoint immunotherapy is a major breakthrough for cancer treatment, yet its efficacy is often limited against many types of malignancies, including malignant mesothelioma. Considering that the immunotherapeutic efficacy depends on immunosurveillance, we sought to develop an active immunization method to break immune tolerance to tumor self-antigen. Here, we demonstrated that TWIST1, the basic helix-loop-helix transcription factor, was associated with human mesothelioma tumorigenesis and required for the invasion and metastasis of mesothelioma in the immune-competent murine AB1 model. When conventional TWIST1 vaccines were not effective in vivo, programmed cell death protein 1 (PD1)-based vaccination provided prophylactic control by inducing long-lasting TWIST1-specific T cell responses against both subcutaneous and metastatic mesothelioma lethal challenges. Furthermore, while CTLA-4 blockade alone did not show any immunotherapeutic efficacy against established mesothelioma, its combination with PD1-based vaccination resulted in 60% complete remission. Mechanistically, these functional T cells recognized a novel highly conserved immunodominant TWIST1 epitope, exhibited cytotoxic activity and long-term memory, and led to durable tumor regression and survival benefit against established AB1 mesothelioma and 4T1 breast cancer. We concluded that PD1-based vaccination controls mesothelioma by breaking immune tolerance to the tumor self-antigen TWIST1. Our results warrant clinical development of the PD1-based vaccination to enhance immunotherapy against a wide range of TWIST1-expressing tumors.

© 2020 The Authors.

In plain English

This laboratory and animal study tested a DNA vaccine against the transcription factor TWIST1 in mouse mesothelioma. Using TCGA data from 87 mesothelioma patients, TWIST1 expression was higher in advanced-stage (TNM III and IV) than early-stage tumours, and overall survival was shorter in the 42 patients with strong expression than the 45 with weak expression. In murine AB1 cells, TWIST1 knockout reduced invasion and lung metastasis after tail-vein injection; overexpression increased metastatic activity, though the authors noted it did not further enhance metastasis significantly. A soluble PD1-TWIST1 fusion DNA vaccine, given by electroporation, raised TWIST1-specific CD4+ and CD8+ T cell responses that conventional sTWIST1 vaccine did not; used prophylactically, with subcutaneous AB1 challenge two weeks after the third dose, it gave 37.5% tumour-free survival among 8 vaccinated mice. Against established AB1 tumours, anti-CTLA-4 alone showed no antitumour activity and sPD1-TWIST1 alone caused regression in 1/6 mice, whereas the combination eradicated tumours in 6/10 mice. Responding T cells recognised a peptide within minipool 37-39. The authors concluded that sPD1-based vaccination breaks tolerance to TWIST1 and controls mesothelioma in these mouse models.

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: preclinical study in mice and cell lines, combined with analysis of a public human tumour gene-expression dataset
• Who was studied: Murine AB1 and AE17 mesothelioma and 4T1 breast cancer cell lines, immunocompetent BALB/c mice and SCID mice; plus gene-expression and survival data from 87 patients in the TCGA mesothelioma cohort (26 stage I-II, 61 stage III-IV)
• Exposure: Not an asbestos-exposure study: the intervention was a soluble PD1-TWIST1 fusion DNA vaccine (compared with conventional sTWIST1 DNA vaccine and sham), 100 micrograms per dose by intramuscular electroporation three times, with or without anti-CTLA-4 antibody 200 micrograms per intraperitoneal injection
• Main results:
  • In the TCGA mesothelioma cohort, TWIST1 expression was higher in advanced-stage tumours, and patients with strong TWIST1 expression had significantly reduced overall survival
  • In mice given AB1 cells intravenously, TWIST1 overexpression increased lung metastasis while knockout suppressed it and prolonged tumour-free survival
  • The authors qualified this in the Discussion: silencing TWIST1 nearly abolished metastatic ability, but overexpression did not significantly further enhance metastasis
  • Prophylactic sPD1-TWIST1 vaccination (8 vaccinated mice, challenged subcutaneously two weeks after the third vaccination) inhibited AB1 growth and gave 37.5% tumour-free survival, unlike sTWIST1 or mock vaccine
  • Antitumour effect depended on TWIST1 in the challenge cells: 2/5 mice rejected wild-type AB1, overexpressing tumours were completely rejected, and all mice challenged with TWIST1 knockout cells developed tumours and died within 30 days
  • Memory challenge 120 days after last vaccination: 3/7 sPD1-TWIST1-vaccinated mice were tumour-free at 30 days, while all control mice developed tumours
  • Against established AB1 tumours, anti-CTLA-4 alone had no activity and all those mice were euthanised within 40 days; sPD1-TWIST1 alone caused regression in 1/6 mice
  • Combined sPD1-TWIST1 plus anti-CTLA-4 eradicated tumours in 6/10 mice, versus 1/7 tumour-free with sTWIST1 plus anti-CTLA-4; tumour volume at day 25 was lower than anti-CTLA-4 alone (p = 0.0224) and PBS (p = 0.0386)
  • Mice cured by the combination rejected a later subcutaneous rechallenge with AB1-Luc cells, while all naive mice succumbed
  • T cell reactivity mapped mainly to minipool 37-39, not to the previously reported epitope LYQVLQSDEL; killing was by CD8+ and not CD4+ T cells
• The authors' conclusion: The authors concluded that sPD1-based TWIST1 DNA vaccination breaks tolerance to the self-antigen TWIST1, induces long-lasting T cell responses and, combined with CTLA-4 blockade, promotes rejection of established mouse mesothelioma, providing a basis for future clinical study
• Limitations the authors state:
  • The authors stated that how the CD8+ cytotoxic T cells mediate the antitumour activity has not yet been worked out
  • The authors noted the epitope specificity they observed may depend on the PD1-based vaccination approach and the tumour type
  • The authors described the work as preclinical, serving as a foundation for future clinical studies rather than evidence in patients

Topics

Medical terms in this study, explained in our Lexicon: Immunotherapy, CTLA-4, Mesothelioma, Carcinogenesis, Metastasis.

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• Synergistic effect of CTLA-4 blockade and cancer chemotherapy in the induction of anti-tumor immunity — W.J. Lesterhuis, J. Salmons, et al. (2013)
• SS1P Immunotoxin Induces Markers of Immunogenic Cell Death and Enhances the Effect of the CTLA-4 Blockade in AE17M Mouse Mesothelioma Tumors — Y. Leshem, E.M. King, et al. (2018)
• CTLA4 blockade in mesothelioma: finally a competing strategy over cytotoxic/target therapy? — L. Calabrò, G.L. Ceresoli, et al. (2015)
• CTLA-4 blockade in mesothelioma: ineffective or reason for optimism? — A. Thomas, R. Hassan (2017)
• Small vessel vasculitis and dry gangrene secondary to combined CTLA-4 and PD-1 blockade in malignant mesothelioma — J. Kefas, C. Harwood, et al. (2022)

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