DNA-Damaging Agents Induce PD-L1 Expression through the Src-STAT1-IRF1 Pathway

Area of Science:

• Oncology
• Immunology
• Molecular Biology

Background:

• Immune checkpoint inhibitors (ICIs) show promise in cancer treatment but face resistance.
• Downregulated programmed cell death-ligand 1 (PD-L1) expression, often due to impaired Janus kinase 1/2 (JAK1/2) signaling, is a key resistance mechanism.
• Discovering JAK-independent pathways to enhance PD-L1 is crucial for improving ICI therapy.

Purpose of the Study:

• To investigate alternative signaling pathways that can upregulate PD-L1 expression independently of JAK1/2.
• To determine if chemotherapeutic agents can restore PD-L1 expression in cancers resistant to ICIs.
• To explore the potential of enhancing ICI efficacy through novel therapeutic strategies.

Main Methods:

• Utilized melanoma cell line A2058 and multiple cancer cell lines.
• Administered chemotherapeutic agents SN-38 and cisplatin.
• Analyzed the expression of interferon regulatory factor 1 (IRF1) and PD-L1.
• Investigated the roles of JAK1/2, signal transducer and activator of transcription 1 (STAT1), Src tyrosine kinase, and IRF1 in PD-L1 regulation.

Main Results:

• SN-38 and cisplatin significantly upregulated IRF1 and PD-L1 expression in A2058 melanoma cells.
• This induction was JAK-independent but STAT1-dependent.
• STAT1 activation was mediated by the Src tyrosine kinase.
• SN-38 demonstrated efficacy in upregulating PD-L1 across various cancer types.

Conclusions:

• DNA-damaging chemotherapeutic agents activate a Src-STAT1-IRF1 signaling axis to enhance PD-L1 expression.
• This pathway offers a potential strategy to overcome ICI resistance in tumors with defective JAK signaling.
• Targeting this axis could improve the clinical efficacy of ICIs in a broader patient population.