Biom-05. The Gut-Microbiota Composition in Pediatric Brain Tumors: An Emerging Crucial Player

BACKGROUND Central nervous system (CNS) tumors represent the main cause of cancer-related deaths in children diagnosed at 0–14 years. It has been demonstrated that the bidirectional interaction between gut microbiota and brain, called microbiota-gut-brain axis, has a key role in pathophysiological processes, mediating proliferation of brain tumor cells. The aim of this study was to determine whether the gut microbiota composition of pediatric patients affected by CNS tumors has peculiarities. METHODS We included 42 pediatric patients from the clinical study NET-2019-12371188 that were divided in two groups: i) 12 affected by SNC tumors (group 1); ii) 30 affected by other tumor types (group 2), non related to CNS. From their stool samples, microbial DNA was extracted, 16S DNA libraries were generated and sequenced on IONS5xl (ThermoFisher). From the resulting operational taxonomic unit (OTU) tables, the composition of gut-microbiota was analyzed. RESULTS To determine the richness of gut microbiota in terms of different taxa, alpha diversity analysis was performed. We applied the number of observed features as data matrix and it was lower in group 1 compared to group 2 (p-value= 0.003); on the other side, the homogeneity of taxonomic groups was determined by Pielou’s evenness index, that was higher in group 1 (p-value=0.018), compared to group 2. Beta-diversity measured with unweighted UniFrac metrics revealed that the taxonomic and phylogenetics composition of gut microbiota is different between group 1 and 2 (p-value= 0.03). Finally, linear discriminant analysis effect size (LEfSe) revealed an increase of genus from RF32 order in group 1, while in group 2 genus Blautia ad genus from Coriobacteriaceaea family increased. CONCLUSIONS In conclusion, gut microbiota has a peculiar composition in pediatric patients affected by CNS tumors.