Base excision repair regulates PD-L1 expression in cancer cells

Area of Science:

• Molecular Biology
• Cancer Research
• Immunology

Background:

• Programmed death-ligand 1 (PD-L1) is crucial for cancer immunotherapy efficacy.
• The precise regulation of PD-L1 expression in cancer cells, especially concerning DNA damage and repair, is not fully understood.

Purpose of the Study:

• To investigate the role of oxidative DNA damage and repair mechanisms in regulating PD-L1 expression in cancer cells.
• To elucidate the signaling pathways involved in PD-L1 upregulation under oxidative stress.

Main Methods:

• Induction of oxidative DNA damage using hydrogen peroxide (H2O2).
• Depletion of base excision repair (BER) enzymes.
• Assessment of PD-L1 expression and DNA damage signaling pathways (ATR/Chk1).
• Analysis of The Cancer Genome Atlas (TCGA) data for correlations between PD-L1, BER/SSBR gene expression, microsatellite instability, and neoantigen production.

Main Results:

• Exogenous hydrogen peroxide (H2O2) treatment significantly upregulates PD-L1 expression in cancer cells.
• Depletion of BER enzymes exacerbates PD-L1 upregulation in response to H2O2.
• PD-L1 upregulation in BER-depleted cells is dependent on ATR/Chk1 kinase activity, indicating mediation by DNA damage signaling.
• TCGA data analysis revealed a negative correlation between PD-L1 expression and BER/single-strand break repair (SSBR) gene expression. Tumors with low BER/SSBR exhibit high microsatellite instability and neoantigen production.

Conclusions:

• PD-L1 expression in cancer cells is regulated by oxidative DNA damage and associated signaling pathways.
• The base excision repair (BER) pathway plays a role in modulating PD-L1 upregulation under oxidative stress.
• These findings suggest a link between DNA damage response, neoantigen production, and PD-L1 expression, potentially impacting cancer immunotherapy outcomes.