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Prognostic Significance of PD-L1 Expression and Its Tumor-Intrinsic Functions in Hypopharyngeal Squamous Cell Carcinoma

Authors Cui P, Jing P, Liu X, Xu W

Received 20 April 2020

Accepted for publication 6 July 2020

Published 17 July 2020 Volume 2020:12 Pages 5893—5902


Checked for plagiarism Yes

Review by Single-blind

Peer reviewer comments 3

Editor who approved publication: Professor Lu-Zhe Sun

Peng Cui, Peihang Jing, Xiuxiu Liu, Wei Xu

Department of Otorhinolaryngology Head and Neck Surgery, Shandong Provincial ENT Hospital, Cheeloo College of Medicine, Shandong University, Jinan, Shandong, People’s Republic of China

Correspondence: Wei Xu
Department of Otorhinolaryngology Head and Neck Surgery, Shandong Provincial ENT Hospital, Cheeloo College of Medicine, Shandong University, No. 4, Duanxing West Road, Jinan 250021, Shandong Province, People’s Republic of China
Tel +86 531 83086271

Purpose: The expression of programmed death-ligand 1 (PD-L1) is common in various solid human cancers and it is an important therapeutic target. However, the expression pattern, clinical significance and potential mechanism of PD-L1 in hypopharyngeal squamous cell carcinoma (HSCC) are still lacking.
Methods: PD-L1 expression in HSCC tumor tissues and paired adjacent hypopharyngeal mucosal tissues was detected using immunohistochemistry assay, and the clinical significance of PD-L1 in HSCC was characterized. In vitro assays including cell viability assays, migration assays, invasion assays as well as Western blot assays were performed to illuminate the biological functions and underlying molecular mechanisms of PD-L1 in HSCC development.
Results: PD-L1 expression was detected in HSCC samples but we found no positive expression in matched normal hypopharyngeal mucosal tissues. The levels of PD-L1 expression were significantly correlated with advanced clinical progression and poor patient survival. Multivariable analysis of Cox model showed that PD-L1 expression was an independent predictor for the prognosis of HSCC patients. Functional experiments showed that the ectopic expression of PD-L1 markedly influenced the proliferation, migration and invasion of FaDu cells in vitro. Mechanistically, investigations demonstrated that PD-L1 could promote the epithelial–mesenchymal transition of FaDu cells. Meanwhile, PD-L1 knockdown inhibited, while PD-L1 overexpression activated the Akt-mTOR signaling pathway in FaDu cells. The EMT induced by PD-L1 overexpression could be reversed by the Akt inhibitor.
Conclusion: In summary, the expression of PD-L1 can act as a significant biomarker for the adverse clinicopathological features and poor prognosis of patients with HSCC. PD-L1 can promote the proliferation, migration and invasion of FaDu cells and consequently enhance the aggressiveness. Moreover, PD-L1 induces EMT through AKT-mTOR signaling pathway. These suggest that PD-L1 has important tumor-intrinsic functions independent of its immunopathogenic effects.

Keywords: PD-L1, hypopharyngeal squamous cell carcinoma, prognosis, epithelial–mesenchymal transition

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