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Screening Bioactive Nanoparticles in Phagocytic Immune Cells for Inhibitors of Toll-like Receptor Signaling
Published on: July 26, 2017
In vivo CRISPR screening identifies LTA4H as a target for potentiating immunotherapy efficacy via the LTB4-neutrophil
Guanwen Yang1, Haokai Qin2, Qi Wang3
1Department of Urology, Zhongshan Hospital, Fudan University, Shanghai, China; Department of Urology, Shanghai Xuhui Central Hospital / Zhongshan - Xuhui Hospital, Fudan University, Shanghai, China; Department of Urology, Minhang Hospital, Fudan University, Shanghai, China.
Abstract:
Despite the clinical success of PD-1 blockade, therapeutic resistance remains a major barrier. Using an in vivo CRISPR-Cas9 screen with a metabolism-focused sgRNA library in MC38 and B16 syngeneic tumor models, we identified leukotriene A4 hydrolase (LTA4H) as a candidate regulator of PD-1 resistance. Lta4h ablation was associated with enhanced PD-1 responsiveness, increased CD8+ T and NK-cell infiltration and function, and reduced myeloid accumulation. Single-cell and spatial transcriptomic analyses showed that LTA4H is expressed in both malignant and myeloid compartments, with LTA4H-high tumor regions associated with myeloid-enriched niches and TGF-β related signaling. Mechanistically, hypoxia-induced HIF1α upregulated Lta4h in tumor cells, supporting tumor cells as one relevant source of LTA4H/LTB4. LTA4H-LTB4 signaling was linked to myeloid remodeling and TGF-β1 production in LTB4-conditioned neutrophils. Pharmacological blockade of LTB4 receptor signaling with the BLT1 antagonist CP-105696 improved tumor control in combination with PD-1 blockade. These findings identify intratumoral LTA4H-LTB4 signaling as a metabolic-immune pathway associated with suppressive myeloid remodeling and support further investigation of LTB4 receptor blockade to improve PD-1 blockade responses.
Insights
Leukotriene A4 hydrolase (LTA4H) regulates resistance to PD-1 blockade immunotherapy. Inhibiting LTA4H signaling enhances anti-tumor immunity and improves treatment response by reducing suppressive myeloid cells.
Area of Science:
- Immunology
- Metabolic pathways
- Cancer research
Background:
- Programmed cell death protein 1 (PD-1) blockade is a successful cancer immunotherapy.
- Therapeutic resistance to PD-1 blockade remains a significant clinical challenge.
- Identifying novel regulators of PD-1 resistance is crucial for improving patient outcomes.
Purpose of the Study:
- To identify novel regulators of PD-1 blockade resistance using a CRISPR-Cas9 screen.
- To elucidate the role of leukotriene A4 hydrolase (LTA4H) in modulating anti-tumor immunity and PD-1 responsiveness.
- To investigate the therapeutic potential of targeting the LTA4H-LTB4 pathway in combination with PD-1 blockade.
Main Methods:
- In vivo CRISPR-Cas9 screen with a metabolism-focused sgRNA library in MC38 and B16 tumor models.
- Single-cell and spatial transcriptomic analyses to assess LTA4H expression and tumor microenvironment composition.
- Pharmacological blockade of the leukotriene B4 (LTB4) receptor using CP-105696.
Main Results:
- LTA4H was identified as a key regulator of PD-1 resistance.
- Lta4h ablation enhanced PD-1 responsiveness, increasing CD8+ T and NK-cell infiltration and function while reducing myeloid accumulation.
- LTA4H expression in tumor and myeloid cells was linked to myeloid-enriched niches and TGF-β signaling.
- Hypoxia-induced HIF1α upregulated Lta4h in tumor cells.
- LTA4H-LTB4 signaling promoted myeloid remodeling and TGF-β1 production.
- Combination therapy with PD-1 blockade and a BLT1 antagonist (CP-105696) improved tumor control.
Conclusions:
- Intratumoral LTA4H-LTB4 signaling represents a metabolic-immune pathway driving suppressive myeloid remodeling.
- Targeting LTA4H and its downstream signaling offers a promising strategy to overcome PD-1 blockade resistance.
- Further investigation into LTB4 receptor blockade is warranted to enhance PD-1 blockade efficacy.
