Enhancing the immunogenicity of Wilms tumor 1 epitope in mesothelioma cells with immunoproteasome inhibitors

Our plain-English summary of Enhancing the immunogenicity of Wilms tumor 1 epitope in mesothelioma cells with immunoproteasome inhibitors, by M. Ito, S. Koido, T. Iwamoto, et al (PloS One, 2024).

The study

• Authors: M. Ito, S. Koido, T. Iwamoto, S. Morimoto, F. Fujiki, H. Sugiyama, S. Matsumoto, C. Effenberger, K. Kiyotani, K. Shiba
• Journal: PloS One
• Published: 2024;19(8):e0308330
• Cited by: 3 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

The immunogenicity of cancer cells is influenced by several factors, including the expression of the major histocompatibility complex class I (MHC-I), antigen expression, and the repertoire of proteasome-produced epitope peptides. The malignant pleural mesothelioma cell line ACC-MEOS-4 (MESO-4) expresses high levels of MHC-I and Wilms tumor 1 (WT1) tumor antigens. Using a functional T cell reporter assay specific for the HLA-A*24:02 restricted WT1 epitope (WT1235, CMTWNQMNL), we searched for factors that augmented the immunogenicity of MESO-4, focusing on proteasomes, which have a central role in the antigen processing machinery. ONX-0914, a selective inhibitor of the immunoproteasome subunit β5i, enhanced immunogenicity dose-dependently at low concentrations without cytotoxicity. In addition, CD8+ T lymphocytes recognizing WT1 showed greater cytotoxicity against MESO-4 pre-treated with ONX-0914. MESO-4 expresses a standard proteasome (SP) and immunoproteasome (IP). Notably, IP has distinct catalytic activity from SP, favoring the generation of antigenic peptides with high affinity for MHC-I in antigen-presenting cells and cancer cells. In vitro, immunoproteasome digestion assay and mass spectrometry analysis showed that IP cleaved WT1235 internally after the hydrophobic residues. Importantly, this internal cleavage of the WT1235 epitope was mitigated by ONX-0914. These results suggest that ONX-0914 prevents the internal destructive cleavage of WT1235 by IP, thereby promoting the specific presentation of the WT1 epitope by MESO-4. In conclusion, selective IP inhibitors might offer a means to modulate cancer cell immunogenicity by directing the presentation of particular tumor epitopes.

Copyright: © 2024 Ito et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

In plain English

This laboratory study used mesothelioma cell lines and immune cells from pancreatic cancer patients; no patients were treated, and asbestos exposure was not examined. The authors tested whether drugs blocking the proteasome, the cell's protein-cutting machinery, would help T cells recognize malignant pleural mesothelioma cells through the protein WT1. They used engineered 'reporter' T cells that glow when they detect a WT1 fragment, WT1235, displayed on the tissue-type molecule HLA-A*24:02. In the MESO-4 cell line, the drug ONX-0914 increased recognition from 10 nM, rising with dose up to 160 nM. ONX-0914 mainly blocks the immunoproteasome part called β5i. Only its highest tested concentration, 200 nM, caused cell death after 48 hours. It did not change WT1 or MHC-I levels. MESO-4 cells pre-treated with 100 nM ONX-0914 were more susceptible to killing by WT1-reactive T cells. In test-tube experiments, the immunoproteasome cut the WT1 fragment internally, and ONX-0914 inhibited this cutting. The authors suggested that combining WT1-targeted T-cell therapy with such an inhibitor may improve treatment, and said animal studies are needed.

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) study using human mesothelioma cell lines and other cultured cells
• Who was studied: Malignant pleural mesothelioma cell lines ACC-MESO-4 (MESO-4), ACC-MESO-1 (MESO-1) and HMMME, obtained from RIKEN BRC in Japan. Also used: T2-A24 and 293-A*24 cells, engineered reporter T cells, and WT1-reactive CD8-positive T cells induced from stored blood cells (PBMCs) of pancreatic cancer patients in a previous clinical trial.
• Exposure: No asbestos exposure was studied. The cells were treated with four proteasome inhibitor drugs: MG132, epoxomicin, bortezomib and ONX-0914 (an immunoproteasome-selective inhibitor).
• Main results:
  • The reporter T cells react specifically to the WT1235 epitope when it is presented on HLA-A*24:02.
  • In MESO-4 cells, ONX-0914 increased WT1-specific recognition by reporter T cells at 10 nM, and the increase rose with dose from 10 to 160 nM.
  • Only the highest concentration of ONX-0914 tested (200 nM) caused MESO-4 cell death after 48 hours. Bortezomib was toxic at 10 nM.
  • ONX-0914 did not change WT1 protein levels in MESO-4 cells.
  • ONX-0914 did not change MHC-I (HLA-A*24 and HLA-ABC) levels in MESO-4 cells.
  • MESO-4 cells pre-treated with 100 nM ONX-0914 were susceptible to killing by WT1-reactive cytotoxic T cells. The figure title describes this as an increase in sensitivity.
  • In test-tube digestion experiments, the immunoproteasome cut the WT1235 epitope internally, mainly after tryptophan and methionine, and ONX-0914 inhibited this internal cutting.
  • ONX-0914 also improved recognition of MESO-1 cells engineered to carry HLA-A*24:02:01, and of HMMME cells.
• The authors' conclusion: The authors concluded that ONX-0914 suppresses the immunoproteasome's internal cutting of the WT1235 epitope and enhances WT1-specific recognition of MESO-4 cells. They suggested that combining WT1235-targeted T-cell transfer therapy with an inhibitor such as ONX-0914 may improve treatment of mesothelioma.
• Limitations the authors state:
  • Animal studies are still needed to determine whether ONX-0914 has anti-tumor activity in mesothelioma.
  • ONX-0914 also inhibited cutting by the standard proteasome, and the authors could not tell whether this reflected the purity of the standard proteasome used or the drug's specificity.
  • Other proteasome components and aminopeptidases may also contribute to the drug's effect.
  • The role of the immunoproteasome in mesothelioma is still unknown.
  • Whether intermediate proteasomes are functional in MESO-4 cells was not determined.

Topics

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

Medical terms in this study, explained in our Lexicon: Wilms Tumor 1 (WT-1), Mesothelioma, Pleural Mesothelioma.

Related studies

• Turning back the Wheel: Inducing Mesenchymal to Epithelial Transition via Wilms Tumor 1 Knockdown in Human Mesothelioma Cell Lines to Influence Proliferation, Invasiveness, and Chemotaxis — T. Plönes, M. Fischer, et al. (2017)
• Proteasome stress sensitizes malignant pleural mesothelioma cells to bortezomib-induced apoptosis — F. Cerruti, G. Jocollè, et al. (2017)
• Wilms tumor 1/cytokeratin dual-color immunostaining reveals distinctive staining patterns in metastatic melanoma, metastatic carcinoma, and mesothelial cells in pleural fluids: an effective first-line test for the workup of malignant effusions — J.R. Conner, E.S. Cibas, et al. (2014)
• Recombinant Immunotoxin with T-cell Epitope Mutations That Greatly Reduce Immunogenicity for Treatment of Mesothelin-Expressing Tumors — R. Mazor, J. Zhang, et al. (2015)
• Withaferin A inhibits the proteasome activity in mesothelioma in vitro and in vivo — H. Yang, Y. Wang, et al. (2012)
• Expression of Wilms' tumor gene (WT1) is associated with survival in malignant pleural mesothelioma — S. Cedrés, M.A. Montero, et al. (2014)

Browse more research in PloS One, or return to medical research.