ABL1 and acute lymphoblastic leukemia: However, BCR-ABL overexpression does not always induce leukemia in any progenitor cell types; it has been reported that only pro-B cells or higher progenitors were permissive to B-ALL development (Signer et al., 2010) and that B-progenitors of fetal origin developed more aggressive leukemia with shorter latency than adult BM B-progenitors upon BCR-ABL overexpression (Montecino-Rodriguez et al., 2014).