MicroRNA-526b-3p and Wnt/β-catenin Pathways Regulate Programmed Death Ligand 1 to Inhibit Growth and Migration of Gefitinib-Resistant Lung Adenocarcinoma Cells

Abstract

Background: Lung cancer is a malignant tumor that seriously threatens human life and health. Gefitinib is a first-line treatment for epidermal growth factor receptor (EGFR)-mutant lung adenocarcinoma (LUAD), but drug resistance is a major obstacle limiting its efficacy. This work aims to examine the effect and underlying mechanism of programmed death ligand 1 (PD-L1) on gefitinib-resistant LUAD cell growth and migration. Methods: Bioinformatics prediction was utilized to predict the targeted binding microRNAs (miRNAs) of PD-L1, after which further verification was performed through dual-luciferase reporter assay and quantitative Real-Time Polymerase Chain Reaction (qRT-PCR). Transfection of gefitinib-resistant cells was completed with PD-L1 overexpression plasmid and miR-526b-3p mimic. XAV-939, an inhibitor of Wnt/β-catenin, was also used to treat gefitinib-resistant cells. Measurement of β-catenin and PD-L1 protein levels were performed using Western blotting. Cellular biological behaviors were determined using relative functional assays. Results: miR-526b-3p directly targeted PD-L1, and miR-526b-3p level was lower in gefitinib-resistant cells gefitinib-resistant HCC827 (HCC827GR) and gefitinib-resistant PC9 (PC9GR) than in sensitive cell lines HCC827 (containing EGFR deletion from E746 to A750; CC-Y1188) and PC9 (containing EGFR exon 19 deletion; CC-Y1418) (p < 0.001). Moreover, miR-526b-3p mimic reduced gefitinib-resistant cell viability, proliferation, migration and invasion, while PD-L1 up-regulation offset the roles of miR-526b-3p mimic (p < 0.05). XAV-939 diminished PD-L1 and β-catenin levels, and suppressed gefitinib-resistant cellular biological behaviors, which further enhanced the inhibitory effects of miR-526b-3p mimic (p < 0.05). Conclusions: miR-526b-3p and Wnt/β-catenin pathways regulate PD-L1, thereby inhibiting the growth, invasion and migration of gefitinib-resistant LUAD cells.