The slow progressive myeloid tumor cells, such as those involved in myelodysplastic syndromes and chronic myeloid leukemia in the chronic phase, were shown to be difficult to engraft in NOD/SCID-β2-microglobulin-deficient or NOG mice (the previous reports [41]–[43] and our unpublished data), suggesting that the engraftment failure did not always indicate a lack of leukemogenecity of the transplanted cells. The gene discussed is HLA-G; the disease is myelodysplastic syndrome.