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

• Published in: PloS one Vol. 19; no. 8; p. e0308330
• Main Authors: Ito, Masaki, Koido, Shigeo, Iwamoto, Takeo, Morimoto, Soyoko, Fujiki, Fumihiro, Sugiyama, Haruo, Matsumoto, Saki, Effenberger, Clara, Kiyotani, Kazuma, Shiba, Kiyotaka
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 08.08.2024; Public Library of Science (PLoS)
• Subjects: Antibodies; Antigen (tumor-associated); Antigen presentation; Antigen processing; Antigen-presenting cells; Antigens; Biology and Life Sciences; Cancer; Cancer therapies; Catalytic activity; CD8 antigen; CD8-Positive T-Lymphocytes - drug effects; CD8-Positive T-Lymphocytes - immunology; Cell Line, Tumor; Cleavage; Cloning; Cytotoxicity; Dendritic cells; Enzymes; Epitopes; Epitopes - immunology; Epitopes, T-Lymphocyte - immunology; HLA-A24 Antigen - immunology; Humans; Hydrophobicity; Immunogenicity; Immunotherapy; Inhibitors; Ipilimumab; Leukemia; Low concentrations; Lymphocytes; Lymphocytes T; Major histocompatibility complex; Mass spectrometry; Mass spectroscopy; Medicine and Health Sciences; Melanoma; Mesothelioma; Mesothelioma - drug therapy; Mesothelioma - immunology; Mesothelioma, Malignant - drug therapy; Mesothelioma, Malignant - immunology; Nephroblastoma; Oligopeptides; Pancreatic cancer; Pemetrexed; Peptides; Proteasome Endopeptidase Complex - immunology; Proteasome Endopeptidase Complex - metabolism; Proteasome Inhibitors - pharmacology; Proteasomes; Research and Analysis Methods; T cell receptors; T cells; Toxicity; Transcription factors; Tumors; WT1 protein; WT1 Proteins - immunology; United States > US; Japan
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0308330

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.