Abstract:

Objective To discuss the expression of programmed cell death-ligand 1 （PD-L1） in the oral squamous cell carcinoma （OSCC） cells and its effect on biological behavior of the OSCC CAL27 cells， and to clarify the possible mechanism. Methods Western blotting method was used to detect the expression levels of PD-L1 protein in the oral epithelial HOK cells and OSCC CAL27， TCA8113， and SCC15 cells； immunofluorescence staining method was used to detect the expression and localization of PD-L1 protein in the CAL27 cells. The CAL27 cells were divided into control group （transfected with si-NC） and si-PD-L1 group （transfected with si-PD-L1）. Western blotting method was used to detect the interference efficiency of the cells in two groups； CCK-8 assay was used to detect the proliferative activities of the cells in two groups at different time points； plate clone formation assay was used to detect the numbers of clone formation of the cells in two groups； cell scratch healing assay was used to detect the scratch healing rates of the cells in two groups； Transwell chamber assay was used to detect the numbers of migration and invasion cells in two groups. Results The expression level of PD-L1 protein in the OSCC cells was higher than that in the HOK cells （P<0.05 or P<0.01）； PD-L1 expressed in the cytoplasm and nucleus of the CAL27 cells. The CCK-8 assay and plate clone formation assay results showed that compared with control group， the proliferative activities of the CAL27 cells in si-PD-L1 group at different time points were significantly decreased（P<0.05 or P<0.01）， and the numbers of clone formation were significantly decreased （P<0.01）. The cell scratch healing assay results showed that compared with control group， the scratch healing rates of the cells in si-PD-L1 group were significantly decreased （P<0.05 or P<0.01）. The Transwell chamber assay results showed that compared with control group， the numbers of migration and invasion cells in si-PD-L1 group were significantly decreased （P<0.01）. Conclusion The expression of PD-L1 in the OSCC cells is higher than that in normal oral epithelial cells， and knocking down PD-L1 expression can inhibit the proliferation， clone formation， migration and invasion capabilities of the OSCC cells.

Key words: Oral squamous cell carcinoma, Programmed cell death-ligand 1, Cell proliferation, Cell migration, Cell invasion