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CRISPR-Cas9 screening identifies an IRF1-SOCS1-mediated negative feedback loop that limits CXCL9 expression and
Imran G House1, Emily B Derrick1, Kevin Sek1
1Cancer Immunology Program, Peter MacCallum Cancer Centre, Melbourne, VIC 3000, Australia; Sir Peter MacCallum Department of Oncology, The University of Melbourne, Parkville, VIC 3010, Australia.
Abstract:
CXCL9 expression is a strong predictor of response to immune checkpoint blockade therapy. Accordingly, we sought to develop therapeutic strategies to enhance the expression of CXCL9 and augment antitumor immunity. To perform whole-genome CRISPR-Cas9 screening for regulators of CXCL9 expression, a CXCL9-GFP reporter line is generated using a CRISPR knockin strategy. This approach finds that IRF1 limits CXCL9 expression in both tumor cells and primary myeloid cells through induction of SOCS1, which subsequently limits STAT1 signaling. Thus, we identify a subset of STAT1-dependent genes that do not require IRF1 for their transcription, including CXCL9. Targeting of either IRF1 or SOCS1 potently enhances CXCL9 expression by intratumoral macrophages, which is further enhanced in the context of immune checkpoint blockade therapy. We hence show a non-canonical role for IRF1 in limiting the expression of a subset of STAT1-dependent genes through induction of SOCS1.
Insights
Researchers found that targeting IRF1 or SOCS1 boosts CXCL9 expression in macrophages, enhancing antitumor immunity. This discovery offers new strategies for improving immune checkpoint blockade therapy effectiveness.
Area of Science:
- Immunology
- Molecular Biology
- Cancer Research
Background:
- CXCL9 expression predicts response to immune checkpoint blockade (ICB) therapy.
- Enhancing CXCL9 expression is a therapeutic goal to augment antitumor immunity.
Purpose of the Study:
- To identify regulators of CXCL9 expression using CRISPR-Cas9 screening.
- To develop strategies for enhancing CXCL9 expression and antitumor immunity.
Main Methods:
- Generated a CXCL9-GFP reporter line via CRISPR knockin.
- Performed whole-genome CRISPR-Cas9 screening to identify CXCL9 regulators.
- Investigated the role of IRF1, SOCS1, and STAT1 signaling in CXCL9 regulation.
Main Results:
- Identified IRF1 as a limiter of CXCL9 expression in tumor and myeloid cells via SOCS1 induction.
- Discovered a subset of STAT1-dependent genes, including CXCL9, that do not require IRF1 for transcription.
- Demonstrated that targeting IRF1 or SOCS1 significantly enhances CXCL9 expression in macrophages, further boosted by ICB therapy.
Conclusions:
- IRF1 plays a non-canonical role in limiting STAT1-dependent gene expression through SOCS1 induction.
- Targeting IRF1 or SOCS1 represents a promising strategy to enhance CXCL9-mediated antitumor immunity, particularly in combination with ICB therapy.
