In the context of leukemia evolution, although transgenic mice in which Dicer 1 or Sbds was abrogated in perivascular stromal cells presented myelodysplastic changes and subsequent evolution to leukemia (9, 71), there is, so far, no evidence clearly demonstrating that dysfunction in perivascular stromal cells causes de novo leukemia in vivo. This evidence concerns the gene SBDS and leukemia.