PD-L1 Expression Affects Neoantigen Presentation.

Area of Science:

• Immunology
• Oncology
• Cancer Immunotherapy

Background:

• Tumor PD-L1 expression is a biomarker for immune checkpoint blockade (ICB) therapy.
• Clinical benefits from ICB therapy have been observed even in patients lacking PD-L1 expression.
• Understanding innate tumor resistance mechanisms is crucial for improving immunotherapy.

Purpose of the Study:

• To investigate the relationship between innate tumor resistance and anti-tumor cytotoxic T lymphocyte (CTL) responses against neoantigens.
• To assess the impact of PD-L1 expression on CTL activation and tumor response during ICB therapy.
• To identify novel neoantigens and T cell receptor (TCR) repertoires for cancer immunotherapy.

Main Methods:

• Assessed the interaction between PD-L1-positive and PD-L1-deleted colorectal tumors with CTLs under ICB therapy in mice.
• Utilized immunogenomics and antigen libraries to identify neoantigens in PD-L1-deficient models.
• Identified relevant TCR repertoires and confirmed the response of engineered CTLs to tumor cells.
• Investigated the efficacy of neoantigen-pulsed dendritic cell (DC) therapy in reversing tumor tolerance.

Main Results:

• PD-L1 deletion in tumors led to robust CTL activation and enhanced anti-tumor responses.
• Identified three H2-K^b-restricted, immunogenic neoantigens associated with PD-L1 deficiency.
• Identified three TCR repertoires that confer specific anti-tumor activity.
• Neoantigen-pulsed DC therapy successfully reversed tumor tolerance in a preclinical model.

Conclusions:

• Innate tumor resistance influences responsiveness to neoantigen-based therapies.
• PD-L1 deficiency can enhance anti-tumor CTL responses, highlighting its potential in immunotherapy.
• Mixed neoantigen peptides presented via DC therapy show promise for overcoming innate resistance in tumors.