Muribaculum intestinale negatively impacts glioma growth in mice through the toll-like receptor 2

Glioblastoma (GBM) is the most common and malignant brain tumor in adult humans. Recent studies have demonstrated a link between the composition of the gut microbiota and glioma progression. Here, we describe that the growth of glioma in mice is inversely correlated with the relative abundance of the anaerobic bacterium Muribaculum intestinale in the feces. We found that M. intestinale administration: 1) induced an inflammatory environment in the gut; 2) reduced glioma growth; 3) increased the pro-inflammatory profile of tumor-associated microglial cells and the frequency of CD8+ T cells; and 4) increased the peripheral TNF-α levels. The effects induced by M. intestinale administration were significantly attenuated upon toll-like receptor 2 (TLR2) silencing using TLR2-targeting siRNA. As a pattern-recognition receptor, TLR2 detects microbial-associated molecular patterns and orchestrates host immune responses to infection. Collectively, these data demonstrate that M. intestinale induces a pro-inflammatory response in glioma bearing mice, inhibiting tumor growth via TLR2-dependent signaling.