PD-L1 tumor-intrinsic signaling and its therapeutic implication in triple-negative breast cancer

Area of Science:

• Oncology
• Molecular Biology
• Cancer Therapeutics

Background:

• Programmed death ligand 1 (PD-L1) is a known target in cancer immunotherapy.
• The tumor-intrinsic functions of PD-L1 in cancer biology and therapeutic development are less understood.
• Triple-negative breast cancer (TNBC) remains a challenging subtype with limited targeted therapies.

Purpose of the Study:

• To elucidate a novel tumor-intrinsic mechanism of PD-L1 in promoting triple-negative breast cancer (TNBC) progression.
• To investigate the role of PD-L1 in regulating the epithelial-mesenchymal transition (EMT) and metastatic potential in TNBC.
• To evaluate the therapeutic potential of targeting the intrinsic PD-L1 signaling pathway in TNBC.

Main Methods:

• Investigated the interaction between PD-L1 and PTP1B in TNBC cells.
• Assessed the effect of PD-L1 on p38-MAPK and GSK3β activity.
• Examined the regulation of Snail stability and degradation by the PD-L1/PTP1B/GSK3β axis.
• Utilized PD-L1 antibodies to target tumor-intrinsic and extrinsic functions in TNBC mouse models (immunodeficient and immunocompetent).

Main Results:

• PD-L1 directly inhibits PTP1B, maintaining p38-MAPK activity and inhibiting GSK3β.
• This cascade prevents GSK3β-mediated degradation of Snail, promoting EMT and TNBC metastasis.
• Antibodies targeting intrinsic PD-L1/Snail pathway restricted TNBC progression in immunodeficient mice.
• Combined targeting of intrinsic and extrinsic PD-L1 functions demonstrated synergistic tumor suppression in immunocompetent models.

Conclusions:

• PD-L1 intrinsically promotes TNBC progression and metastasis by stabilizing Snail through a novel signaling pathway.
• Targeting this tumor-intrinsic PD-L1 pathway represents a promising therapeutic strategy for PD-L1-overexpressing TNBC.
• Dual targeting of PD-L1's intrinsic and extrinsic functions offers enhanced efficacy for TNBC treatment.