Microbe-Mediated Activation of Toll-like Receptor 2 Drives PDL1 Expression in HNSCC
Jacqueline E Mann1,2, Megan L Ludwig1,3, Aditi Kulkarni1
1Department of Otolaryngology-Head and Neck Surgery, University of Michigan, Ann Arbor, MI 48109, USA.
Abstract:
As immunotherapies targeting the PDL1 checkpoint have become a mainstay of treatment for a subset of head and neck squamous cell carcinoma (HNSCC) patients, a detailed understanding of the mechanisms underlying PDL1-mediated immune evasion is needed. To elucidate factors regulating expression of PDL1 in HNSCC cells, a genome-wide CRISPR profiling approach was implemented to identify genes and pathways conferring altered PDL1 expression in an HNSCC cell line model. Our screen nominated several candidate PDL1 drivers, including Toll-like Receptor 2 (TLR2). Depletion of TLR2 blocks interferon-γ-induced PDL1 expression, and stimulation of TLR2 with either Staphylococcus aureus or a bacterial lipopeptide mimetic, Pam3CSK4, enhanced PDL1 expression in multiple models. The data herein demonstrate a role for TLR2 in modulating the expression of PDL1 in HNSCC models and suggest that microbiota may directly modulate immunosuppression in cancer cells. Our study represents a step toward disentangling the diverse pathways and stimuli regulating PDL1 expression in HNSCC and underscores a need for future work to characterize the complex microbiome in HNSCC patients treated with immunotherapy.
Insights
Toll-like Receptor 2 (TLR2) drives programmed death-ligand 1 (PDL1) expression in head and neck squamous cell carcinoma (HNSCC). This suggests that bacteria may directly influence cancer immune evasion, impacting immunotherapy effectiveness.
Area of Science:
- Immunology
- Oncology
- Microbiology
Background:
- Programmed death-ligand 1 (PDL1) checkpoint inhibitors are crucial for treating some head and neck squamous cell carcinoma (HNSCC) patients.
- Understanding PDL1-mediated immune evasion mechanisms is vital for optimizing HNSCC immunotherapy.
Purpose of the Study:
- To identify genes and pathways regulating PDL1 expression in HNSCC cells.
- To investigate the role of Toll-like Receptor 2 (TLR2) in PDL1 modulation within HNSCC models.
Main Methods:
- Genome-wide CRISPR screening was employed to identify PDL1 regulatory factors in an HNSCC cell line.
- Experiments involved gene depletion, interferon-γ induction, and TLR2 stimulation with bacterial components (Staphylococcus aureus, Pam3CSK4).
Main Results:
- Toll-like Receptor 2 (TLR2) was identified as a key regulator of PDL1 expression in HNSCC.
- TLR2 depletion inhibited interferon-γ-induced PDL1 expression.
- TLR2 stimulation enhanced PDL1 expression in multiple HNSCC models.
Conclusions:
- Toll-like Receptor 2 (TLR2) plays a significant role in modulating PDL1 expression in head and neck squamous cell carcinoma.
- Microbiota may directly influence cancer immunosuppression by affecting PDL1 expression.
- Further research is needed to explore the HNSCC microbiome's impact on immunotherapy outcomes.
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