Effects Of Gut Microbiome On The Development Of Glioma And Foxp3 Expression Of Glioma Microenvironment In Mice

BackgroundGlioma is the most common primary tumor of central nervous system with high malignancy and poor prognosis.Gut microbiome(GM)is composed of microorganisms with different properties and functions,which play an important role in human physiology and biological activities.The interaction between host and microorganism through the gut-brain axis and brain,which has a certain impact on some central nervous system diseases and malignant tumors.However,the relationship between gut microbiome and glioma growth is still unclear.Exploring the correlation between gut microbiome and glioma progression and explaining the interaction between the both will contribute to the development of adjuvant therapy for glioma and provide new ideas for clinical therapy of glioma.Objective(Ⅰ)To investigate the effect of glioma development on GM of mice.(Ⅱ)To study the effects of GM dysbiosis on glioma development and immune microenvironment components.(Ⅲ)To evaluate the role of balanced GM environment in glioma development.Methods(Ⅰ)Effects of glioma on gut microbiome:implanting GL261-Luc cells into C57BL/6 mice brain on the 0d.Fecal samples were collected at the 1d before tumor implantation,the 14d and 21d of tumor growth,and were analyzed by 16S rDNA sequencing.(Ⅱ)Effects of gut microbiome dysbiosis on glioma progression:ampicillin,vancomycin,neomycin and metronidazole were added into some healthy C57BL/6 mice drinking water to consume GM,while the other mice were given normal drinking water.Implanting GL261-Luc cells into C57BL/6 mice brain on the 7d.Tumor development was monitored by in vivo optical imaging technology.Fecal samples were collected at the 7d before tumor implantation and the 21d of tumor growth,and were analyzed by 16S rDNA sequencing.Immunohistochemistry was used to the expression of CD8 and Foxp3 in mouse brain.(Ⅲ)Effects of gut microbiome homeostasis on glioma progression:the same antibiotics were added in healthy C57BL/6 mice drinking water to consume GM for 7days.After balancing the GM for 24h,the fecal samples of healthy mice were transplanted into some C57BL/6 mice treated with antibiotics.The fecal samples were collected and analyzed by 16S rDNA sequencing.Implanting GL261-Luc cells into C57BL/6 mice brain after 24h.Tumor development was monitored by in vivo optical imaging technology.Immunohistochemistry was used to the expression of CD8 and Foxp3 in mouse brain.Results(Ⅰ)The abundance of Bacteroidia decreased with the growth of glioma,while the abundance of Firmicutes increased with the development of glioma.(Ⅱ)Before tumor cells implantation,the GM structure of mice treated with antibiotics was significantly different from that of mice not treated with antibiotics(P<0.05).After tumor cells implantation,the tumor growth rate of mice treated with antibiotics was significantly higher than that of mice not treated with antibiotics(P=0.004).After 21 days of tumor growth,there was no significant change in CD8 expression and a decrease in Foxp3 expression in the brain of the antibiotic-treated mice compared with the untreated mice.(Ⅲ)Before tumor cells implantation,the GM structure of mice in the fecal transplantation group and those without fecal transplantation group was significantly different(P<0.05).After tumor cells implantation,the tumor development rate of mice in the fecal transplantation group was significantly lower than that in the non-transplantation group(P=0.018).There was no significant difference in CD8 expression between the two groups of mice that received and did not receive fecal transplantation,while Foxp3 expression was up-regulated in the brains of mice that received fecal transplantation.Conclusion(Ⅰ)The development of glioma induces structural changes of mice GM.(Ⅱ)GM can affect glioma growth and regulate the expression of Foxp3 in tumor microenvironment.(Ⅲ)The abundance of Bacteroidia can affect the growth of glioma.