Ring-shaped double minutes in human acute myelocytic leukemia and in the murine SEW A sarcoma. A comparison

Direct bone marrow preparations for chromosome analysis in 376 patients with leukemia and/or myeloproliferative disease revealed 40 cases in which the stemlines contained varying frequencies of double minutes (DM). In the case presented, part of the DM were clearly ring-shaped and bore an amazing resemblance to those recently described in a subline of the SEWA mouse ascites sarcoma. A comparative study of incidence and morphology of the DM of the 2 materials was therefore undertaken. While they shared many characteristics, the main difference between them was the striking functional stability of the human DM versus the highly erratic behavior of the murine DM. It was striking that about half of the 12–13 cases of DM in leukemia from the literature resembled the present case in having fairly large, ring-shaped DM that, although most likely acentric, maintained a remarkable mitotic stability. The genes they carry, which speculatively may be assumed to stimulate the malignant capacity of the leukemic cells, are therefore incorporated in the stemline karyotype much more permanently than if they had been carried by “ordinary” DM.