Gold nanoparticles conjugated with programmed death-ligand 1 antibodies induce apoptosis of SCC-25 oral squamous cell carcinoma cells via programmed death-ligand 1/signal transducer and transcription 3 pathway.

Objective: Objective of this study is to test the anti-cancer effect of the gold nanoparticles conjugated with programmed death-ligand 1 (PD-L1) specific antibodies (PDL1-GNP), on oral squamous cell carcinoma.

Design: To test the effect of PDL1-GNP on oral squamous cell carcinoma, SCC-25 cells, a type of human oral squamous cell carcinoma which were isolated from human tongue, and HaCaT human keratinocytes as normal cell control, were used. Cell viability was tested by the water-soluble tetrazolium-1 and live/dead assays, while apoptotic cell death of SCC-25 cells were monitored by immunofluorescent staining and flow cytometry. The molecular changes during PDL1-GNP-mediated apoptosis were analyzed using Western blot analysis.

Results: PDL1-GNP treatment effectively decreased the growth of SCC-25 cells but not HaCaT cells. The results of the confocal microscopic assay showed that PDL1-GNP specifically bound to the SCC-25 cell membrane. Furthermore, the results of the live/dead, cytochrome c release assays and flow cytometry indicated PDL1-GNP-mediated apoptotic cell death of SCC-25 cells. PDL1-GNP-treated SCC-25 cells showed a phenotype with increased apoptotic proteins, including cleaved form of caspase-3, caspase-9, and poly (ADP-ribose) polymerase 1 (PARP1). PDL1-GNP treatment also effectively decreased B-cell lymphoma 2 (Bcl-2) and PD-L1 protein expression. Phosphorylation of signal transducer and transcription 3 (STAT3) was significantly increased after PDL1-GNP treatment on SCC-25 cells.

Conclusions: PDL1-GNP treatment induced SCC-25 cell apoptosis possibly by inhibiting the function of the PD-L1 protein, since PD-L1 blocks STAT3 phosphorylation, which promotes apoptotic cell death.