PD-L1: PD-1 interaction contributes to the functional suppression of T-cell responses to human uveal melanoma cells in vitro.
OBJECTIVE
To assess the expression of PD-L1 on human uveal melanomas and its potential to suppress T-cell function.


METHODS
A panel of primary and metastatic uveal melanoma cell lines was evaluated for PD-L1 expression by RT-PCR and flow cytometric analysis. Uveal melanoma-containing eyes were examined for PD-L1 expression by immunohistochemistry. PD-L1 function was tested by coculturing IFN-gamma-pretreated uveal melanoma cells with activated Jurkat T cells for 48 hours and assessing T-cell production of IL-2 by ELISA.


RESULTS
Five of the nine primary and one of the five metastatic uveal melanoma cell lines tested constitutively expressed PD-L1 protein at various levels. However, all primary and metastatic uveal melanoma cell lines upregulated PD-L1 expression after stimulation with IFN-gamma. Immunohistochemistry demonstrated that PD-L1 was not expressed by primary uveal melanomas in situ. IL-2 production by activated Jurkat T cells was decreased significantly when the cells were cocultured with IFN-gamma-pretreated uveal melanoma cells. More than 70% of IL-2 production was restored by addition of either anti-PD-L1 or anti-PD-1 antibody to the coculture assays (P < 0.01).


CONCLUSIONS
Expression of PD-L1 by uveal melanoma cells regulates T-cell function by suppressing IL-2 production. The results imply that the presence of IFN-gamma in the tumor local microenvironment promotes upregulation of PD-L1 expression by uveal melanoma, which may, in part, promote immune escape by impairing T-cell function. The selective blockade of PD-L1 is a potential strategy in T-cell-based immunotherapy for uveal melanoma.
Yang
Wanhua
W
Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9057, USA.
Chen
Peter W
PW
Li
Haochuan
H
Alizadeh
Hassan
H
Niederkorn
Jerry Y
JY
D015703:Antigens, CD / Q000235:genetics / Q000378:metabolism*; D051017:Apoptosis Regulatory Proteins / Q000235:genetics / Q000378:metabolism*; D060890:B7-H1 Antigen; D018920:Coculture Techniques; D004797:Enzyme-Linked Immunosorbent Assay; D005434:Flow Cytometry; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D007124:Immunoenzyme Techniques; D007371:Interferon-gamma / Q000494:pharmacology; D007376:Interleukin-2 / Q000378:metabolism; D019169:Jurkat Cells; D008213:Lymphocyte Activation; D008545:Melanoma / Q000276:immunology* / Q000473:pathology; D009362:Neoplasm Metastasis; D009363:Neoplasm Proteins / Q000378:metabolism*; D061026:Programmed Cell Death 1 Receptor; D011994:Recombinant Proteins; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013601:T-Lymphocytes / Q000502:physiology*; D014604:Uveal Neoplasms / Q000276:immunology* / Q000473:pathology
D015703:Antigens, CD; D051017:Apoptosis Regulatory Proteins; D060890:B7-H1 Antigen; C423236:CD274 protein, human; D007376:Interleukin-2; D009363:Neoplasm Proteins; C105992:PDCD1 protein, human; D061026:Programmed Cell Death 1 Receptor; D011994:Recombinant Proteins; D007371:Interferon-gamma