Src-dependent modulation of IFNγ-induced PD-L1 expression in human breast cancer cell lines

Area of Science:

• Oncology
• Immunology
• Molecular Biology

Background:

• Triple-negative breast cancer (TNBC) has a poor prognosis and limited treatment options.
• Immune checkpoint inhibitors (ICIs) show promise for TNBC but face resistance.
• Understanding mechanisms of immune evasion in TNBC is crucial for developing effective therapies.

Purpose of the Study:

• To investigate the role of Src tyrosine kinase in regulating programmed death-ligand 1 (PD-L1) expression induced by interferon-gamma (IFNγ) in TNBC.
• To determine if Src inhibition can enhance T-cell-mediated cytotoxicity against TNBC cells.

Main Methods:

• Stimulation of TNBC and luminal A breast cancer cell lines with IFNγ.
• Assessment of Src phosphorylation at Y419.
• Pharmacological inhibition of Src using specific inhibitors.
• Measurement of PD-L1 mRNA and protein expression.
• Analysis of PD-L1-related transcription factors.
• Co-culture assays with CD8+ T-cells to evaluate T-cell-mediated cytotoxicity.

Main Results:

• IFNγ stimulation induced time-dependent Src phosphorylation at Y419 in both TNBC and luminal A cells.
• Src inhibition significantly suppressed IFNγ-induced PD-L1 mRNA and protein expression.
• Src inhibition reduced the activation of PD-L1-related transcription factors, indicating transcriptional regulation.
• TNBC cells showed greater susceptibility to T-cell-mediated cytotoxicity than luminal A cells.
• Src inhibition further enhanced T-cell-mediated cytotoxicity against TNBC cells.

Conclusions:

• Src tyrosine kinase plays a critical role in mediating IFNγ-induced PD-L1 expression in TNBC cell lines.
• Src inhibition enhances T-cell-mediated cytotoxicity against TNBC, suggesting a mechanism for overcoming immune evasion.
• Targeting Src may be a viable combinatorial strategy to augment antitumor immunity in TNBC.