Role of microRNA 4717, its effects on programmed cell death protein-1 in hepatitis B infection, and interaction between PDCD1 and miR-4717

It is suggested that programmed cell death protein-1 (PD-1) is involved in hepatitis B virus (HBV) infection, the leading cause of hepatocellular carcinoma globally. This study was multi-aimed, that is, to investigate the role of microRNA (miR) 4717 and its target, PD-1 and to determine how the rs10204525 polymorphism in the 3′ untranslated region (3′UTR) of PD-1 affects its interaction with miR-4717. The expression levels of miR-4717 with various single-nucleotide polymorphisms were measured by reverse transcription–quantitative polymerase chain reaction (RT-qPCR). A total of 54 tissue samples from HBV-infected individuals were collected, genotyped, and categorized into three groups; AA (n = 32), AG (n = 18), and GG (n = 4). The expression levels of gene PDCD1 and its corresponding PD-1 protein were significantly declined in the AA group as compared to AG and GG groups. There was a negative linear association between PDCD1 and miR-4717 in the tissue samples. HEPG2 cells transfected with an miR-4717 mimic or PD-1 small interfering (si)RNA exhibited significantly reduced expression levels of PDCD1 and PD-1, whereas cells transfected with an inhibitor of miR-4717 demonstrated greater expression levels of PDCD1 and PD-1 compared with the scramble control. In addition, cell viability and apoptosis were assessed in cells transfected with an miR-4717 mimic, PD-1 siRNA, or an miR-4717 inhibitor. Results revealed that treatment with the miR-4717 mimic or PD-1 siRNA enhanced viability of cells and reduced apoptosis. The results of this study suggest that rs10204525 polymorphism interferes with the interaction between PD-1 and miR-4717 and therefore induces apoptosis in liver cancer cells.