Frequent Loss of IRF2 in Cancers Leads to Immune Evasion through Decreased MHC Class I Antigen Presentation and Increased PD-L1 Expression
Department of Pathology; Department of Bioinformatics and Integrative Biology; Department of Microbiology and Physiological Systems; Department of Medicine, Gastroenterology Division; Garber Lab
Amino Acids, Peptides, and Proteins | Biochemistry, Biophysics, and Structural Biology | Cancer Biology | Computational Biology | Genetic Phenomena | Hemic and Immune Systems | Immunity | Immunopathology | Immunoprophylaxis and Therapy | Neoplasms
To arise and progress, cancers need to evade immune elimination. Consequently, progressing tumors are often MHC class I (MHC-I) low and express immune inhibitory molecules, such as PD-L1, which allows them to avoid the main antitumor host defense, CD8(+) T cells. The molecular mechanisms that led to these alterations were incompletely understood. In this study, we identify loss of the transcription factor IRF2 as a frequent underlying mechanism that leads to a tumor immune evasion phenotype in both humans and mice. We identified IRF2 in a CRISPR-based forward genetic screen for genes that controlled MHC-I Ag presentation in HeLa cells. We then found that many primary human cancers, including lung, colon, breast, prostate, and others, frequently downregulated IRF2. Although IRF2 is generally known as a transcriptional repressor, we found that it was a transcriptional activator of many key components of the MHC-I pathway, including immunoproteasomes, TAP, and ERAP1, whose transcriptional control was previously poorly understood. Upon loss of IRF2, cytosol-to-endoplasmic reticulum peptide transport and N-terminal peptide trimming become rate limiting for Ag presentation. In addition, we found that IRF2 is a repressor of PD-L1. Thus, by downregulating a single nonessential gene, tumors become harder to see (reduced Ag presentation), more inhibitory (increased checkpoint inhibitor), and less susceptible to being killed by CD8(+) T cells. Importantly, we found that the loss of Ag presentation caused by IRF2 downregulation could be reversed by IFN-stimulated induction of the transcription factor IRF1. The implication of these findings for tumor progression and immunotherapy are discussed.
DOI of Published Version
J Immunol. 2019 Oct 1;203(7):1999-2010. doi: 10.4049/jimmunol.1900475. Epub 2019 Aug 30. Link to article on publisher's site
Journal of immunology (Baltimore, Md. : 1950)
Kriegsman B, Vangala P, Chen BJ, Meraner P, Brass AL, Garber M, Rock KL. (2019). Frequent Loss of IRF2 in Cancers Leads to Immune Evasion through Decreased MHC Class I Antigen Presentation and Increased PD-L1 Expression. Program in Bioinformatics and Integrative Biology Publications. https://doi.org/10.4049/jimmunol.1900475. Retrieved from https://escholarship.umassmed.edu/bioinformatics_pubs/156