In summary, based on the results of the IHC analysis of tumor specimens for at least four treatment resistance proteins (p53, MRP1, AKR1B10, and AKR1B1), patients with AML can be classified into three prognostic groups, the so-called Urayasu classification for AML, as follows: Group 1 (favorable prognosis); Group 2 (intermediate prognosis); and Group 3 (poor prognosis). The gene discussed is CD9; the disease is acute myeloid leukemia.