A hypothetical model to explain the 'termination' of chronic myeloid leukemia into blastic crisis

Interphase ribosomal RNA cistron staining in chronic myeloid leukaemia

Aim-To evaluate the haemopoietic function of bone marrow blood forming cells in human chronic myeloid leukaemia (CML) by means of silver staining of nucleolar organiser region (AgNOR).Methods-Nucleoli were investigated in bone marrow blast cells and in erythroid, granulocytic, and megakaryocytic cells from 10 haematologically healthy subjects and from 26 patients with chronic myeloid leukemia (17 in benign phase, nine with blast crisis). The investigation was done before treatment, by means of a one step silver staining method. In every case 50 to 100 blasts, promyelocytes, myelocytes, immature (pronormoblastic and basophilic normoblastic) and mature (polychromatic normoblastic) erythroid elements, and megakaryocytes were evaluated for the mean numbers of nucleoli and for the average number of AgNORs per nucleus. Student's t test was used to compare the patient and control groups. Other statistical analyses were carried out by means of the computer assisted "HEMA" system.Results-Compared with controls, activation of NORs was noticed only in CML blasts, while there was a decrease in NORs in the erythroid elements, promyelocytes, and megakaryocytes. The AgNOR score of polychromatic normoblasts and megakaryocytes started to decrease in the benign stage of CML, whereas a similar decrease in pronormoblasts, basophilic normoblasts, and promyelocytes was detected only in patients with CML blast crisis.Conclusions-The loss of AgNOR sites in cell series in CML may be related to intrinsic defects in their proliferation.

Early lymphoid blastic crisis following major karyotypic conversion in a chronic myeloid leukemia patient treated with interferon-alpha

A major karyotypic conversion following interferon-alpha treatment delays or prevents blastic crisis in patients with chronic myeloid leukemia. We report here a 12-year-old boy with Ph1+ chronic myeloid leukemia who, after achieving a major karyotypic conversion following 12 months interferon-alpha treatment, developed an early lymphoid blastic transformation 7 months later while still under interferon-alpha therapy. A number of possible explanations for this quite unexpected event are discussed.

Cell biology of CML--a model linking the chronic and terminal phases

A model for the pathogenesis of chronic myeloid leukaemia (CML) is proposed. It relies on a comparison between normal steady-state and regenerating haemopoiesis and suggests that chronic phase CML stem cells have a finite capacity for self-renewal. According to the model, metamorphosis of the disease occurs once the potential for chronic phase cell production has been exhausted. The model considers also the generation of leukocytosis in the chronic phase and the origin of the terminal phase. Comparison with normal regenerating haemopoiesis allows discrimination between features of CML that are fundamentally abnormal and those which are normally associated with regeneration.