Expression of the Protooncogenes c-myc, c-fos, and c-fms in Acute Myelocytic Leukemia at Diagnosis and in Remission

RNA transcript levels of the protooncogenes c-myc, c-fos, and c-fms were measured in bone marrow cells obtained from patients with acute myelocytic leukemia at diagnosis or in complete remission. As controls, normal bone marrow cells were studied. The c-myc RNA levels are significantly higher in acute myelocytic leukemia cells at diagnosis than in remission or in normal marrow cells. In most instances the high c-myc RNA levels are a reflection of the high proportion of immature cells present in leukemic marrows. The bone marrow cells of several patients contain extremely high levels of c-myc RNA, levels which cannot be accounted for by the proportion of immature cells present in the bone marrow. The leukemic cells of patients with morphologically indistinguishable leukemias manifest different patterns of c-myc, c-fos, and c-fms expression. This observation is consistent with differences in behavior of leukemic cells even among patients with the same French-American-British type of leukemia. The normal-appearing bone marrow cells of some acute myelocytic leukemia patients in complete remission differ from normal bone marrow cells in having slightly higher c-myc RNA levels, as well as in the pattern of expression of c-fos and c-fms. The possible use of protooncogene expression patterns to subdivide the French-American-British categories of acute myelocytic leukemia into subtypes with greater prognostic significance is discussed.