Current understanding of the human microbiome in glioma

Abstract

There is mounting evidence that the human microbiome is highly associated with a wide variety of central nervous system diseases. However, the link between the human microbiome and glioma is rarely noticed. The exact mechanism of microbiota to affect glioma remains unclear. Recent studies have demonstrated that the microbiome may affect the development, progress, and therapy of gliomas, including the direct impacts of the intratumoral microbiome and its metabolites, and the indirect effects of the gut microbiome and its metabolites. Glioma-related microbiome (gut microbiome and intratumoral microbiome) is associated with both tumor microenvironment and tumor immune microenvironment, which ultimately influence tumorigenesis, progression, and responses to treatment. In this review, we briefly summarize current knowledge regarding the role of the glioma-related microbiome, focusing on its gut microbiome fraction and a brief description of the intratumoral microbiome, and put forward the prospects in which microbiome can be applied in the future and some challenges still need to be solved.

Keywords: glioma; gut microbiome; immune microenvironment; intratumoral microbiome; metabolism.

Figure 1

Hypothesis of the relationship among gut microbiome, intratumoral microbiome and glioma. Chemotherapy, radiotherapy and immunotherapy can change the glioma microenvironment and gut microenvironment, thus changing the composition of microbiome, thus shaping the immune microenvironment of glioma and further affecting the therapeutic efficacy.

Figure 2

Gut metabolites affect the functions of immune cells and glioma immune microenvironment, which shapes the immune state into the suppressive type. Metabolites also change the epigenetic landscape of glioma cells, then altering the behavior of tumor.

Figure 3

Application and transformation of microbiome. Stool and/or tumor samples from the population are collected and then sequenced. According to the analysis of the sequencing results, glioma patients can be diagnosed and classified, as well as guided personalized treatment.