Project description:We used microarrays to investigate gene expression changes in leukemic cells from Pax5+/- mice treated with antibiotics. Precursor B cell acute lymphoblastic leukemia (pB-ALL), the most common type of childhood leukemia, is frequently characterized by the cooperation of a genetic predisposition acquired in utero and secondary oncogenic events taking place only in a fraction of predisposed children after birth. Although predisposition can be detected at birth, it is currently unknown which factors determine the development of overt leukemia in genetic carriers and how this can be potentially prevented. Experimental studies have shown that infectious stimuli promote disease onset in genetically predisposed mice. Here, we analyzed the impact of the microbiome on leukemogenesis in a mouse model (Pax5+/- mice) that faithfully mimicks genetic predisposition and leukemogenesis of human pB-ALL related to the synergy of genetic predisposition and exposure to a natural infectious environment. Employing 16S rRNA sequencing and machine learning we can accurately predict a distinct gut microbiome which is determined by a specific constitutional genetic variant. Deprivation of the gut microbiome by antibiotic treatment enhanced pB-ALL development in Pax5+/- predisposed (63% vs. 22%) but not in wildtype mice (0%). This finding was observed in the presence but also -to a lesser extent- in the absence of a natural, infectious environment (48%). The composition of the gut microbiome constitutes a biomarker signature and allows to identify specifically those Pax5+/- mice that developed leukemia. This indicates that the gut microbiome can be used to identify carriers at risk to develop leukemia and to reduce this risk by early-life interventions.
Project description:The majority of childhood leukemias are precursor B-cell acute lymphoblastic leukemias (pB-ALLs) caused by a combination of prenatal genetic predispositions and oncogenic events occurring after birth. Although genetic predispositions are frequent in children (>1% to 5%), fewer than 1% of genetically predisposed carriers will develop pB-ALL. Although infectious stimuli are believed to play a major role in leukemogenesis, the critical determinants are not well defined. Here, by using murine models of pB-ALL, we show that microbiome disturbances incurred by antibiotic treatment early in life were sufficient to induce leukemia in genetically predisposed mice, even in the absence of infectious stimuli and independent of T cells. By using V4 and full-length 16S ribosomal RNA sequencing of a series of fecal samples, we found that genetic predisposition to pB-ALL (Pax5 heterozygosity or ETV6-RUNX1 fusion) shaped a distinct gut microbiome. Machine learning accurately (96.8%) predicted genetic predisposition using 40 of 3983 amplicon sequence variants as proxies for bacterial species. Transplantation of either wild-type (WT) or Pax5+/- hematopoietic bone marrow cells into WT recipient mice revealed that the microbiome is shaped and determined in a donor genotype-specific manner. Gas chromatography-mass spectrometry (GC-MS) analyses of sera from WT and Pax5+/- mice demonstrated the presence of a genotype-specific distinct metabolomic profile. Taken together, our data indicate that it is a lack of commensal microbiota rather than the presence of specific bacteria that promotes leukemia in genetically predisposed mice. Future large-scale longitudinal studies are required to determine whether targeted microbiome modification in children predisposed to pB-ALL could become a successful prevention strategy.