Inflammatory activation of microglia by Staphylococcus aureus caused phenotypic alterations and affected glioblastoma growth

: As the most common type of tumour in brain, glioma has a high rate of morbidity and mortality and easily penetrates the surrounding normal brain parenchyma. The immunosuppressive microenvironment, which is similar to that in other neoplasms, is believed to participate in the tumorigenesis of glioma. Thus, many experts are seeking to exploit microenvironment as a therapeutic target. In the present study, we focused on microglia polarization to investigate the anti-glioma response of microglia inflammatory activation by Staphylococcus aureus in vitro and in vivo. First, we found that intratumor injection of S. aureus delayed glioma growth in C57/BL6 mice. Then, we showed that inflammatory microglia activated by S. aureus inhibited glioma cell proliferation, migration, and invasion. This inhibition was likely related to the phenotypic switch observed in microglia. In intracranial tumour models, the microglia activated by S. aureus exerted antitumour efficacy and prolonged animal survival. Taken together, our results suggest that microglia activated by S. aureus have antitumour efficacy, which may be a potential therapeutic agent for glioma. SIGNIFICANCE OF THE STUDY: In this study, we mainly demonstrated the antitumour efficacy of microglia after activated by S. aureus. Firstly, we found that intratumor injection of S. aureus inhibited the tumour growth in intracranial orthotopic glioma model. In addition, we found that the microglia around the glioma may exert antitumour efficacy, and its phenotype may be altered by stimulation of S. aureus. Our data manifested that S. aureus did not directly suppress cell proliferative, migration, and invasion capacity, but by activating microglia. And in mice GL261 GBMs, injection of microglia after cocultured with S. aureus inhibited tumour growth and prolonged animal survival.