Three distinct mechanisms underlying human γδ T cell-mediated cytotoxicity against malignant pleural mesothelioma

Our plain-English summary of Three distinct mechanisms underlying human γδ T cell-mediated cytotoxicity against malignant pleural mesothelioma, by Y. Umeyama, H. Taniguchi, H. Gyotoku, et al (Frontiers in Immunology, 2023).

The study

• Authors: Y. Umeyama, H. Taniguchi, H. Gyotoku, H. Senju, H. Tomono, S. Takemoto, H. Yamaguchi, M.S.O. Tagod, M. Iwasaki, Y. Tanaka, H. Mukae
• Journal: Frontiers in Immunology
• Published: 2023;14:1058838
• Cited by: 4 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Introduction: Malignant pleural mesothelioma (MPM) is a rare and highly aggressive thoracic tumor with poor prognosis and limited therapeutic options. Although immune checkpoint inhibitors exhibit a promising effect in some patients with unresectable MPM in clinical trials, the majority of MPM patients show only modest response rates to the currently available treatments. It is thus imperative to develop novel and innovative therapeutic modalities for MPM, including immune effector cell-based therapies.

Methods: γδ T cells were expanded using tetrakis-pivaloyloxymethyl 2-(thiazole-2-ylamino) ethylidene-1,1-bisphosphonate (PTA) and interleukin-2, and the therapeutic potential of γδ T cells was examined through analyzing cell surface markers and cellular cytotoxicity against MPM in vitro using a europium chelate-based time-resolved fluorescence assay system and a luciferase-based luminescence assay system.

Results And Discussion: We successfully expanded γδ T cells from peripheral blood mononuclear cells of healthy donors and MPM patients. γδ T cells expressed natural killer receptors such as NKG2D and DNAM-1 and exhibited a moderate level of cytotoxicity to MPM cells in the absence of antigens. The inclusion of PTA, (E)-4-hydroxy-3- methylbut-2-enyl diphosphate (HMBPP) or zoledronic acid (ZOL) induced a TCR-dependent cytotoxicity in γδ T cells and secreted interferon-γ (IFN-γ). In addition, γδ T cells expressing CD16 exhibited a significant level of cytotoxicity against MPM cells in the presence of an anti-epidermal growth factor receptor (EGFR) mAb, at lower concentrations than in clinical settings, whereas a detectable level of IFN-γ was not produced. Taken together, γδ T cells showed cytotoxic activity against MPM in three distinct mechanisms through NK receptors, TCRs and CD16. Since major histocompatibility complex (MHC) molecules are not involved in the recognition, both autologous and allogeneic γδ T cells could be used for the development of γδ T cell-based adoptive immunotherapy for MPM.

Copyright © 2023 Umeyama, Taniguchi, Gyotoku, Senju, Tomono, Takemoto, Yamaguchi, Tagod, Iwasaki, Tanaka and Mukae.

In plain English

This laboratory study, done entirely in cell culture, tested whether immune cells called gamma delta (γδ) T cells can kill malignant pleural mesothelioma cells. It did not study asbestos exposure. Researchers in Nagasaki, Japan grew γδ T cells from the blood of healthy volunteers and five mesothelioma patients, using a compound called PTA plus interleukin-2. They then tested the cells on two mesothelioma cell lines, MESO-1 and MESO-4. With no added stimulant, the cells showed no detectable killing within 1 hour. After 72 hours, at 200 immune cells per tumor cell, they killed about 60% of MESO-1 and 30% of MESO-4 cells. Adding PTA strengthened killing, and MESO-4 cells were killed with as little as 1 pM PTA. Zoledronic acid sensitized tumor cells less efficiently. γδ T cells with high levels of a protein called CD16 also killed tumor cells when an anti-EGFR antibody was added, but without detectable interferon-gamma. Patients' cells expanded at rates the authors called equivalent to healthy donors'. The authors concluded that γδ T cells killed mesothelioma cells through three distinct mechanisms, and that either a patient's own or donor γδ T cells could be used to develop a cell-based therapy.

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 (in vitro) experimental study using human blood-derived immune cells and mesothelioma cell lines
• Who was studied: γδ T cells grown from the blood of healthy adult volunteers (donors labeled HD04 to HD16) and of five malignant pleural mesothelioma patients (MPM01 to MPM05), collected under approval of Nagasaki University Hospital, Japan, and tested against two human malignant pleural mesothelioma cell lines, MESO-1 and MESO-4. Dates of collection are not given.
• Exposure: Not an asbestos exposure study. The tested treatment was γδ T cells expanded with PTA and interleukin-2. The cells were tested alone, with the stimulants PTA, HMBPP or zoledronic acid (ZOL), or with an anti-EGFR monoclonal antibody.
• Main results:
  • In four healthy donors, after 11 days of PTA and interleukin-2, γδ T cells made up 99.2%, 98.9%, 99.0% and 99.5% of cells. The reported increases in cell numbers were 797-, 2290-, 421- and 294-fold.
  • Without stimulants, in a 1-hour assay, healthy-donor γδ T cells showed no detectable killing of the mesothelioma cell lines, even at 200 effector cells per target cell.
  • Without stimulants, over 72 hours, healthy-donor γδ T cells killed about 60% of MESO-1 cells and 30% of MESO-4 cells at 200 effector cells per target cell.
  • Over 48 hours with PTA, healthy-donor γδ T cells killed MESO-4 cells with only 1 pM PTA. MESO-1 cells required a much higher concentration (printed as 1 mM or greater).
  • Zoledronic acid made the mesothelioma cells susceptible to killing much less efficiently than PTA did.
  • With an anti-EGFR antibody, γδ T cells from donors with high CD16 levels (HD11, HD12) showed a statistically significant level of killing of mesothelioma cells. Cells from donors with low CD16 showed little or low killing.
  • γδ T cells produced interferon-gamma when stimulated with PTA, but essentially none during CD16 (anti-EGFR antibody) mediated killing.
  • In four mesothelioma patients, γδ T cells were 0.13%, 0.68%, 0.20% and 0.11% of lymphocytes before expansion and 15.7%, 83.3%, 71.7% and 20.6% after. The authors described the expansion rates (710-, 911-, 632- and 463-fold) as equivalent to those of healthy donors.
  • γδ T cells from patient MPM05 (17.6% before and 97.6% after expansion) killed both cell lines with PTA, and also killed them with anti-EGFR antibody. They secreted interferon-gamma with PTA but essentially none with the antibody.
• The authors' conclusion: The authors concluded that γδ T cells killed mesothelioma cells through three distinct mechanisms: NK receptors, T cell receptors and CD16. Because MHC molecules are not involved, they concluded that both a patient's own (autologous) and donor (allogeneic) γδ T cells could be used to develop adoptive immunotherapy for mesothelioma.
• Limitations the authors state:
  • The authors noted that without added stimulants, killing of mesothelioma cells required large numbers of γδ T cells and long contact with tumor cells.
  • The authors stated that mesothelioma cells were not efficiently sensitized by HMBPP or zoledronic acid.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Mesothelioma.

Medical terms in this study, explained in our Lexicon: Pleural Mesothelioma, Prognosis, checkpoint inhibitors, Unresectable, Clinical Trial, EGFR, Immunotherapy.

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