MicroRNA-26b-5p enhances T cell responses by targeting PIM-2 in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a common tumor malignancy threatening a significant number of people worldwide. Although microRNAs (miRNAs) have been shown to play essential role in tumorigenesis, little is known about their role in T cells functions during HCC progression. The abundances of miR-26b-5p were detected in HCC tissues or cells, T cells and H22 cells by quantitative real-time polymerase chain reaction (qRT-PCR). Regulation effect of miR-26b-5p on proviral integrations of moloney virus 2 (PIM2) was investigated by qRT-PCR, western blot (WB) and immunohistochemical analysis. The effect of miR-26b-5p and PIM-2 on cytokines secretion in CD4+ and CD8+ cells was evaluated by commercial enzyme linked immunosorbent assays (ELISA) kit. The interaction between miR-26b-5p and PIM-2 was probed by luciferase activity and RNA immunoprecipitation (RIP). H22 subcutaneous model was established to investigate the interaction of miR-26b-5p with HCC and immune competence. The abundance of miR-26b-5p was decreased in HCC and associated with poor survival. Addition of miR-26b-5p contributed to secretion of tumor necrosis factor α (TNF-α), interferon-γ (IFN-γ), interleukin-6 (IL-6) and IL-2 in CD4+ and CD8+ cells. Interestingly, PIM-2 was negatively regulated by miR-26b-5p and PIM-2 knockdown reversed anti-miR-26b-5p-mediated immunosuppression. Moreover, inhibitory effect of miR-26b-5p on HCC tumorigenesis was dependent on immune competence. miR-26b-5p enhanced T cells responses by targeting PIM-2 in HCC, uncovering a promising therapeutic opportunity of HCC through reactivating immune system. •Low miR-26b-5p expression is associated with HCC.•Addition of miR-26b-5p promotes cytokines secretion in CD4+ and CD8+ cells.•PIM-2 is a target of miR-26b-5p•PIM-2 depletion reverses anti-miR-26b-5p-mediated inhibitory on cytokines secretion in CD4+ and CD8+ cells•MiR-26b-5p inhibits subcutaneous HCC growth in mice•The inhibitory effect of miR-26b-5p requires immune competence