Transplantation of 90.000 positive cells as assessed by GFP expression (Fig. 5A) of bone marrow cells retrovirally transduced with the oncogene MLL-AF9 induced myeloid leukemia both in wild type and Par1−/− bone marrow cells with comparable latency, penetrance, and morphology (Fig. 5B and data not shown). The gene discussed is F2R; the disease is myeloid leukemia.