Herein, we used several cell-type-specific murine Cre lines to conditionally knockout Vps33b in endothelial cells (ECs), BM mesenchymal stem cells (MSCs) and megakaryocytes (MKs) to determine the roles of different niche cell-derived exosomes in B-ALL development. The gene discussed is VPS33B; the disease is precursor B-cell acute lymphoblastic leukemia.