MicroRNA-155-5p suppresses PD-L1 expression in lung adenocarcinoma.

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MiR‐155‐5p is a key oncogenic microRNA that maintains immune homeostasis and mediates cross‐talk between inflammation and tumorigenesis. High expression of programmed death ligand‐1 (PD‐L1) also plays an important role in immune tolerance in tumors. The present study aimed to explore the relationship between miR‐155‐5p and PD‐L1 in lung adenocarcinoma (LUAD) cells A549 and H1650. The expression levels of miR‐155‐5p and PD‐L1 in LUAD patients were detected by a quantitative reverse transcriptase‐polymerase chain reaction (qRT‐PCR) and mimics of miR‐155‐5p were used to model increased expression in A549 or H1650 cells. After 24 h, we measured levels of PD‐L1 by qRT‐PCR, western blotting and flow cytometry. In addition, we identified two sites in the PD‐L1 3′‐UTR (5′‐AGCAUUA‐3′ and 5′‐GCAUUAA‐3′) that can be bound by miR‐155‐5p using TargetScan (http://www.targetscan.org). Compared to normal tissue, miR‐155‐5p was overexpressed in tumor tissue (P = 0.0456), whereas the expression of PD‐L1 was not significantly different (P = 0.1349). The expression levels of miR‐155‐5p and PD‐L1 were negatively correlated (r = −0.6409, P = 0.0459 and r = −0.7544, P = 0.0117). Exogenous overexpression of miR‐155‐5p decreased the mRNA, total protein and membrane protein expression levels of PD‐L1 both in A549 and H1650 cells (P < 0.05). Taken together, our data suggest that miR‐155‐5p may suppress the expression of PD‐L1 in LUAD.