MicroRNA-519 inhibits hypoxia-induced tumorigenesis of pancreatic cancer by regulating immune checkpoint PD-L1

Pancreatic cancer is highly prevalent and exhibits a high incidence and mortality rate. Hypoxia contributes to tumorigenesis and the progression of pancreatic cancer. To the best of our knowledge, the role of microRNA (miR)-519 has not been investigated in hypoxia-induced pancreatic cancer progression. The purpose of the present study was to elucidate the mechanism underlying miR-519-mediated regulation of pancreatic cancer progression. Reverse transcription-quantitative PCR and western blotting were performed to investigate miR-519 and programmed death ligand 1 (PD-L1) mRNA and protein levels, respectively. Additionally, a Transwell assay was performed to examine the invasiveness of PANC-1 and SW1990 cells. Cells were subsequently stained with Annexin V to determine the apoptotic rate of cells. Furthermore, bioinformatics analysis and a dual-luciferase reporter assay were performed to confirm the direct association between miR-519 and PD-L1, and a xenograft experiment was conducted to test the role of miR-519 in vivo. The results revealed that the expression levels of miR-519 in pancreatic cancer cells were reduced following hypoxia treatment. Furthermore, transfection with miR-519 mimics inhibited PANC-1 and SW1990 cell invasiveness, and induced apoptosis under hypoxic conditions. PD-L1 was also identified as a downstream target of miR-519, and rescued the miR-519 mimic-attenuated tumorigenesis of pancreatic cancer cells under hypoxic conditions. Additionally, treatment with miR-519 mimics significantly suppressed the tumor growth of PANC-1 cells. The results of the present study indicated a novel mechanism of miR-519-mediated tumorigenesis in pancreatic cancer cells under hypoxic conditions. The conclusions may be crucial for the improvement of future pancreatic cancer treatment.