A Critical Role of Intracellular PD-L1 in Promoting Ovarian Cancer Progression

Area of Science:

• Immunology
• Oncology
• Molecular Biology

Background:

• Immune checkpoint inhibitors targeting PD-1/PD-L1 interactions offer durable responses in some cancers.
• However, response rates for PD-1/PD-L1 blockade are low in ovarian cancer, suggesting alternative mechanisms of immune evasion.

Purpose of the Study:

• To investigate the role of intracellular PD-L1 in ovarian cancer progression.
• To explore the impact of PARP inhibitors on intracellular PD-L1 accumulation.
• To evaluate therapeutic strategies targeting intracellular PD-L1.

Main Methods:

• Analysis of PD-L1 localization in ovarian cancer patient tumors and cell lines.
• Treatment of ovarian cancer cells and xenografts with PARP inhibitors and a cell-penetrating antibody targeting intracellular PD-L1.
• Assessment of cell proliferation, apoptosis, cell cycle, DNA damage, and STING activation.

Main Results:

• Ovarian cancer PD-L1 is predominantly intracellular, and PARP inhibitors increase its accumulation.
• Mutation of the PD-L1 acetylation site reduces PD-L1 levels, impairs colony formation, and induces cell cycle arrest and apoptosis.
• Targeting intracellular PD-L1 with a cell-penetrating antibody reduces tumor growth, enhances DNA damage, and activates STING signaling.

Conclusions:

• Intracellular PD-L1 plays a critical role in ovarian cancer progression.
• PARP inhibitors and strategies targeting intracellular PD-L1 show therapeutic potential in ovarian cancer.