CYB561D2 up-regulation activates STAT3 to induce immunosuppression and aggression in gliomas.

Background Fine tuned balance of reactive oxygen species (ROS) is essential for tumor cells and tumor cells use immune checkpoints to evade attack form immunity system. However, it's unclear whether there is any crosstalk between these two pathways. CYB561D2, an antioxidant protein, is part of 5-gene prognosis signature in gliomas and its involvement in gliomas is unknown. Here, we aim to provide a detailed characterization of CYB561D2 in gliomas. Methods CYB561D2 expression was measured in clinical samples of gilomas and normal tissues. The effects of CYB561D2 on immunity related genes and tumor behaviors were investigated in glioma cell lines with various in vitro and in vivo assays. Results CYB561D2 expression was enhanced in gliomas compared to control tissues. CYB561D2 up-regulation was associated with high grading of gliomas and short survival in patients. CYB561D2 expression was induced by H2O2 in glioma cell lines. CYB561D2 and its functional product ascorbate activated STAT3 dose-dependently. CYB561D2 over-expression increased PD-L1, CCL2 and TDO2 expression, and induced immunosuppression in co-cultured T cells. In in vitro assays, CYB561D2 knock-down suppressed cell growth, colony formation, migration and promoted apoptosis. In contrast, CYB561D2 over-expression reduced survival rate in intracranial glioma model and this effect could be blocked by dominant negative-STAT3. The CYB561D2 up-regulation and the positive association of CYB561D2 with PD-L1, CCL2 and TDO2 expression were cross-validated in open-access datasets. Conclusions CYB561D2 up-regulation induces immunosuppression and aggression via activating STAT3 in gliomas and CYB561D2 mediates ROS-tumor immunity crosstalk.