PD-L2 glycosylation promotes immune evasion and predicts anti-EGFR efficacy
Yiqi Xu1,2, Zhenyue Gao1,2, Ruxin Hu1
1Department of Cell Biology, School of Basic Medical Sciences, Tianjin Medical University, Tianjin, People's Republic of China.
Background:
Combination therapy has been explored for advanced head and neck squamous cell carcinoma (HNSCC) owing to the limited efficacy of anti-epidermal growth factor receptor (EGFR) therapy. Increased expression and glycosylation of immune checkpoint molecules in tumors are responsible for cetuximab therapy refractoriness. The role of programmed death ligand 2 (PD-L2), a ligand of PD-1, in the immune function is unclear. Here, we examined the regulatory mechanism of PD-L2 glycosylation and its role in antitumor immunity and cetuximab therapy.
Methods:
Single-cell RNA sequencing and immunohistochemical staining were used to investigate PD-L2 expression in cetuximab-resistant/sensitive HNSCC tissues. The mechanism of PD-L2 glycosylation regulation was explored in vitro. The effects of PD-L2 glycosylation on immune evasion and cetuximab efficacy were verified in vitro and using mice bearing orthotopic SCC7 tumors.
Results:
The PD-L2 levels were elevated and N-glycosylated in patients with cetuximab-resistant HNSCC. Glycosylated PD-L2 formed a complex with EGFR, which resulted in the activation of EGFR/signal transducer and activator of transcription 3 (STAT3) signaling and decreased the cetuximab binding affinity to EGFR. The N-glycosyltransferase fucosyltransferase (FUT8), a transcriptional target of STAT3, was required for PD-L2 glycosylation. Moreover, glycosylation modification stabilized PD-L2 by blocking ubiquitin-dependent lysosomal degradation, which consequently promoted its binding to PD-1 and immune evasion. Inhibition of PD-L2 glycosylation using Stattic, a specific STAT3 inhibitor, or PD-L2 mutation blocking its binding to FUT8, increased cytotoxic T lymphocyte activity and augmented response to cetuximab.
Conclusions:
Increased expression and glycosylation of PD-L2 in tumors are an important mechanism for cetuximab therapy refractoriness. Thus, the combination of PD-L2 glycosylation inhibition and cetuximab is a potential therapeutic strategy for cancer.
Insights
In head and neck cancer, elevated and glycosylated PD-L2 hinders cetuximab effectiveness. Inhibiting PD-L2 glycosylation alongside cetuximab may improve cancer therapy outcomes.
Area of Science:
- Oncology
- Immunology
- Molecular Biology
Background:
- Advanced head and neck squamous cell carcinoma (HNSCC) shows limited response to anti-EGFR therapy.
- Tumor immune checkpoint molecule glycosylation contributes to cetuximab resistance.
- The specific role of programmed death ligand 2 (PD-L2) in immune function requires clarification.
Purpose of the Study:
- To investigate the regulatory mechanisms of PD-L2 glycosylation.
- To determine PD-L2's role in antitumor immunity and cetuximab therapy efficacy.
- To explore PD-L2 glycosylation as a therapeutic target in HNSCC.
Main Methods:
- Utilized single-cell RNA sequencing and immunohistochemistry to analyze PD-L2 in HNSCC tissues.
- Conducted in vitro experiments to explore PD-L2 glycosylation regulation.
- Verified the impact of PD-L2 glycosylation on immune evasion and cetuximab efficacy in vitro and in vivo mouse models.
Main Results:
- Elevated and N-glycosylated PD-L2 was observed in cetuximab-resistant HNSCC.
- Glycosylated PD-L2 formed a complex with EGFR, activating STAT3 signaling and reducing cetuximab binding.
- PD-L2 glycosylation, regulated by STAT3-dependent FUT8, stabilized PD-L2, promoting immune evasion.
- Inhibiting PD-L2 glycosylation enhanced T-cell activity and cetuximab response.
Conclusions:
- Tumor PD-L2 expression and glycosylation are key mechanisms of cetuximab resistance in HNSCC.
- Targeting PD-L2 glycosylation in combination with cetuximab presents a promising therapeutic strategy for cancer treatment.
