BMP4 and acute lymphoblastic leukemia: In this study, we analyzed the behaviour of MSC in paediatric patients with acute lymphoblastic leukemia (ALL-MSCs), with special emphasis in the inverse correlation between high levels of BMP4 production in the cultures and MSC proliferation at diagnosis, during treatment and after remission (out of therapy), as well the relevance of leukemic cells in the powerfully enhanced BMP4 production of MSC at diagnosis and finally the important contribution of BMP4 in maintaining MSC in the hematopoietic niche.