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Published on: May 1, 2015
PD-L1 Influences Cell Spreading, Migration and Invasion in Head and Neck Cancer Cells
Jonas Eichberger1,2, Daniela Schulz1,2, Kristian Pscheidl1
1Department of Oral and Maxillofacial Surgery, University Hospital Regensburg, 9305 Regensburg, Germany.
Abstract:
The programmed cell death protein-1 (PD-1)/programmed cell death ligand-1 (PD-L1) axis blockade has been implemented in advanced-stage tumor therapy for various entities, including head and neck squamous cell carcinoma (HNSCC). Despite a promising tumor response in a subgroup of HNSCC patients, the majority suffer from disease progression. PD-L1 is known to influence several intrinsic mechanisms in cancer cells, such as proliferation, apoptosis, migration and invasion. Here, we modulated PD-L1 expression in three HNSCC cell lines with differential intrinsic PD-L1 expression. In addition to an alteration in the epithelial-to-mesenchymal transition (EMT) marker expression, we observed PD-L1-dependent cell spreading, migration and invasion in a spheroid spreading assay on four different coatings (poly-L-lysine, collagen type I, fibronectin and Matrigel®) and a chemotactic transwell migration/invasion assay. Furthermore, the overexpression of PD-L1 led to increased gene expression and small interfering ribonucleic acid (siRNA) knockdown and decreased gene expression of Rho-GTPases and related proteins in a RT2 Profiler™ PCR Array. Rac1 and Rho-GTPase pulldown assays revealed a change in the activation state concordantly with PD-L1 expression. In summary, our results suggest a major role for PD-L1 in favoring cell motility, including cell spreading, migration and invasion. This is presumably caused by altered N-cadherin expression and changes in the activation states of small Rho-GTPases Rho and Rac1.
Insights
Programmed cell death ligand-1 (PD-L1) influences cancer cell motility. Modulating PD-L1 impacts head and neck squamous cell carcinoma (HNSCC) cell spreading, migration, and invasion, suggesting a role in tumor progression.
Area of Science:
- Oncology
- Cancer Biology
- Immunotherapy
Background:
- The programmed cell death protein-1 (PD-1)/programmed cell death ligand-1 (PD-L1) pathway is a target in advanced cancer therapy, including head and neck squamous cell carcinoma (HNSCC).
- While PD-1/PD-L1 blockade shows promise, many HNSCC patients do not respond, indicating other roles for PD-L1 in tumor progression.
- PD-L1 is implicated in intrinsic cancer cell mechanisms like proliferation, apoptosis, migration, and invasion.
Purpose of the Study:
- To investigate the role of PD-L1 in modulating intrinsic cancer cell behaviors.
- To examine how altered PD-L1 expression affects cell motility, epithelial-to-mesenchymal transition (EMT), and Rho-GTPase activity in HNSCC cell lines.
Main Methods:
- PD-L1 expression was modulated in three HNSCC cell lines with varying intrinsic PD-L1 levels.
- Cell spreading, migration, and invasion were assessed using spheroid spreading and transwell assays on different extracellular matrix coatings.
- Gene expression of Rho-GTPases was analyzed using RT2 Profiler PCR Arrays, and their activation states were measured via pulldown assays.
Main Results:
- Modulation of PD-L1 expression altered epithelial-to-mesenchymal transition (EMT) marker expression.
- PD-L1 expression levels correlated with cell spreading, migration, and invasion capabilities across various substrates.
- Overexpression of PD-L1 increased, while siRNA knockdown decreased, the gene expression of Rho-GTPases; activation states of Rac1 and Rho-GTPases changed concordantly with PD-L1 expression.
Conclusions:
- PD-L1 plays a significant role in promoting cancer cell motility, including spreading, migration, and invasion.
- Altered N-cadherin expression and changes in Rho and Rac1 GTPase activation states are likely mechanisms underlying PD-L1's pro-motility effects.
- These findings suggest PD-L1's involvement in HNSCC progression beyond immune evasion.
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