Site-Dependent Immune Escape Due to Impaired Dendritic Cell Cross-Priming

Area of Science:

• Immunology
• Cancer Biology
• Oncology

Background:

• T-cell recognition of tumor neoantigens is crucial for cancer immune surveillance and immunotherapy.
• Tumors can evade immune responses through antigenicity changes or immunosuppressive microenvironments, leading to cancer immunoediting.
• The influence of tissue site of origin on cancer immune surveillance and immunoediting remains poorly understood.

Purpose of the Study:

• To investigate T-cell-mediated surveillance of neoantigen-expressing pancreatic adenocarcinoma in mice.
• To determine if tissue microenvironment affects immune escape and immunoediting processes.
• To identify mechanisms of immune escape and potential therapeutic strategies.

Main Methods:

• Studied T-cell surveillance of murine pancreatic adenocarcinoma cells expressing neoantigens.
• Administered tumor cells via subcutaneous, intravenous, pancreatic, and peritoneal routes.
• Utilized PD-1 and CTLA-4 checkpoint blockade and CD40 agonist treatment.
• Assessed T-cell priming by type I conventional dendritic cells (cDC1) and immune responses.

Main Results:

• Highly antigenic tumors were eliminated after subcutaneous/intravenous challenge but showed selective immune escape in the pancreas and peritoneum.
• Tumor outgrowth occurred without evidence of immunoediting and was resistant to PD-1/CTLA-4 blockade.
• Immune escape correlated with impaired CD8+ T-cell priming by cDC1, which was restored by CD40 agonist treatment.
• CD40 agonist enhanced cDC1 cross-presentation, promoting T-cell priming and epitope spread, leading to immunologic control.

Conclusions:

• Immune escape of highly antigenic tumors can be tissue-restricted and occur independently of immunoediting.
• Specific tissue microenvironments can impose barriers to cDC1-mediated T-cell priming.
• Overcoming cDC1 priming barriers is essential for effective combination immunotherapies against cancer.