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-a levels. The effects induced by M. intestinale administration were significantly reduced upon toll-like receptor 2 (TLR2) silencing using siRNA targeting TLR2. These receptors recognise microbial patterns and control 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. Overall design: To investigate the effects of M. intestinale treatment on the gut tissue of glioma beraring mice, bulk mRNA sequencing was performed in the distal colon tissues of vehicle and M. intestinale glioma mice.