IRF8-mutant B cell lymphoma evades immunity through a CD74-dependent deregulation of antigen processing and presentation in MHCII complexes
Year: 2024
Type: article
Abstract: In diffuse large B-cell lymphoma (DLBCL), the transcription factor IRF8 is the target of a series of potentially oncogenic events, including, chromosomal translocation, focal amplification, and super-enhancer perturbations. IRF8 is also frequently mutant in DLBCL, but how these variants contribute to lymphomagenesis is unknown. We modeled IRF8 mutations in DLBCL and found that they did not meaningfully impact cell fitness. Instead, IRF8 mutants, mapping either to the DNA-binding domain (DBD) or c-terminal tail, displayed diminished transcription activity towards CIITA, a direct IRF8 target. In primary DLBCL, IRF8 mutations were mutually exclusive with mutations in genes involved in antigen presentation. Concordantly, expression of IRF8 mutants in murine B cell lymphomas uniformly suppressed CD4, but not CD8, activation elicited by antigen presentation. Unexpectedly, IRF8 mutation did not modify MHC CII expression on the cell surface, rather it downmodulated CD74 and HLA- DM, intracellular regulators of antigen peptide processing/loading in the MHC CII complex. These changes were functionally relevant as, in comparison to IRF8 WT, mice harboring IRF8 mutant lymphomas displayed a significantly higher tumor burden, in association with a substantial remodeling of the tumor microenvironment (TME), typified by depletion of CD4, CD8, Th1 and NK cells, and increase in T-regs and Tfh cells. Importantly, the clinical and immune phenotypes of IRF8-mutant lymphomas were rescued in vivo by ectopic expression of CD74. Deconvolution of bulk RNAseq data from primary human DLBCL recapitulated part of the immune remodeling detected in mice and pointed to depletion of dendritic cells as another feature of IRF8 mutant TME. We concluded that IRF8 mutations contribute to DLBCL biology by facilitating immune escape.
Source: Science Advances
Language: English
Subfield: Pathology and Forensic Medicine
Field: Medicine
Domain: Health Sciences
Open Access status: gold
Estimated APC paid: $4,500
Funders: U.S. Department of Veterans Affairs, Cancer Prevention and Research Institute of Texas, University of Texas System, Neuroendocrine Tumor Research Foundation, National Institutes of Health, National Cancer Institute, National Institute of General Medical Sciences, National Institute of Allergy and Infectious Diseases, National Institute of Environmental Health Sciences
Awards: Mays Cancer Center at UT Health SA, Mitochondrial Metabolism and RNA Methylation in Cancer, G2805199789, Mitochondrial 2-hydroxyglutarate dehydrogenases modulate the cellular epitranscriptome, Pharmacological modulation of epigenetic changes in AML, Validation of microRNAs as therapeutic targets in hematological malignancies, Interaction of the TMEM127 tumor suppressor with the mTORC1 lysosomal activating complex, Role of RNA Binding Proteins in BCR/ABL Leukemogenesis, Oxidative stress and RNA methylation, G8788408177, Mechanism-based Targeting of the RNA Processing Machinery of SARS-CoV-2, Mayo Clinic Multiple Myeloma SPORE, Addressing biological and therapeutic gaps in rare neuroendocrine cancer with a novel organoid-based model, Mechanisms of enhancer dynamics and assembly in gene regulation
OpenAlex ID: W4400578706