Myeloid and erythroid lineage expression of haemopoietic progenitors derived from an abnormal clone in erythroleukaemia

Target cell of leukemic transformation in acute megakaryoblastic leukemia

Acute megakaryoblastic leukemia (AMkL) is a newly defined acute leukemia in which the differentiation of proliferating blasts is arrested at the megakaryocytic precursor stage. In order to clarify whether a target cell of leukemic transformation in AMkL is a cell committed to megakaryocytic lineage, or a multipotential stem cell, we examined AMkL patients with regard to: a) the presence of myelodyplastic features in residual erythroid and granulocytic cells, b) coexistence of myeloperoxidase (MPO)-positive blasts with megakaryoblasts, and c) the presence of the same chromosomal abnormality in erythroid and granuloid colony-forming cells as seen in megakaryoblasts. Regarding the former two items, results were compared with those from megakaryoblastic crisis of chronic myelocytic leukemia (CML-MkBC) and transient myeloproliferative disorder in Down syndrome (DS-TMD), which are thought to be multipotential stem cell disorders. Among 18 patients with AMkL, three, all complicating myelofibrosis, had marked myelodysplastic changes of erythroid series and/or granulocytic series. In 4 out of 7 patients with CML-MkBC, 5 out of 8 patients with DS-TMD, and 7 out of 18 patients with AMkL, MPO-positive blasts, even though rare, were observed in addition to PPO-positive blasts. All except one of these patients with AMkL also showed complicating myelofibrosis. In one case of AMkL with myelofibrosis, chromosomal analysis of cultured cells of individual colonies revealed that all the analysable metaphases from both CFU-GM and BFU-E had the same chromosomal abnormality as megakaryoblasts. This study has clarified that a considerable proportion of AMkL cases, particularly those with complicating myelofibrosis or showing acute myelofibrosis, arise against the background of a multipotential stem cell disorder, even if blasts are exclusively megakaryocytic in phenotype.

Morphologic, immunologic and cytogenetic studies in erythroleukaemia: evidence for multilineage involvement and identification of two distinct cytogenetic-clinicopathological types

Clinical features, as well as morphology, immunophenotype and cytogenetics were retrospectively studied in 20 patients with an original diagnosis of erythroleukaemia (EL) reclassified according to the FAB criteria. Fifteen patients had de novo EL, five patients had therapy-related EL. Myelodysplasia preceded the onset of EL in eight cases and myelodysplastic features involving multiple haemopoietic lineages were observed at leukaemia presentation in all cases. Immunologic findings confirmed multilineage involvement, showing sub-population of cells expressing platelet-associated markers in more than 50% of cases tested and the presence of a myelomonocytic component, besides glycophorin A-positive cells. Cytogenetically, major karyotype aberrations (MAKA), defined by the presence of three or more aberrant events in the same clone, were observed in 14 cases, minor karyotype aberrations (MIKA) were observed in four cases and normal karyotype in two cases. No differences in the cytological-cytogenetic picture of our patients with de novo EL, and with therapy-related EL were found suggesting that aetiological factors and/or pathogenetic mechanisms common to EL and secondary leukaemia may exist. All patients with MAKA had leftward shift of erythropoiesis with proerythroblasts and basophilic erythroblasts usually representing more than 50% of all erythroid cells. In patients with MIKA or normal karyotype, maturatio of erythroid cells, though morphologically abnormal, was quantitatively preserved and early erythroblasts never exceeded 25% of erythroid cells. Clinically, the haemoglobin level at presentation, as well as in the proportion of patients achieving complete remission after chemotherapy, appeared to be lower in the maturation arrest-MAKA group as compared to the preserved maturation-MIKA/normal karyotype group. Median survival was shorter in the former group (3.5 months) than in the latter (median 13 months). Morphologic-immunologic-cytogenetic studies thus allow for the identification of two distinct cytogenetic-clinicopathological types of EL.

Maturation of human acute myeloid leukaemia in vitro: the response to five recombinant haematopoietic factors in a serum-free system

The abilities of human recombinant IL-3, GM-CSF, G-CSF, M-CSF and Epo to induce maturation in human AML cells in vitro were investigated using cell specimens from 25 AML patients. The experiments were carried out under exactly defined serum-free culture conditions. In the absence of CSFs, monocytic and/or granulocytic maturation was detected in 14/25 cases. IL-3, GM-CSF, G-CSF and M-CSF elevated the proportions of monocyte/macrophages in 3/25, 2/25, 1/25 and 6/25 cases respectively, and increased the percentages of mature granulocytes in 2/25, 1/25, 1/25 and 0/25 cases, and if so only to a limited extent (values below 50%). The 3H-thymidine (3H-TdR) uptake studies revealed that IL-3, GM-CSF, G-CSF and M-CSF were efficient stimulators of DNA synthesis of AML cells in 19, 15, 13 and four of those cases, respectively. Thus, although the cells in most cases responded to CSFs by activation of DNA synthesis, they were unable to give rise to terminally differentiated stages. Provision of CSFs in combination was more frequently effective in enhancing maturation and also increased the magnitude of maturation response. Monocytic versus granulocytic maturation of AML cells after culture did not correlate with the FAB cytology nor with the type of CSF presented; but generally granulocytic maturation was an infrequent phenomenon. Epo stimulated erythroid differentiation and DNA synthesis only in the case of erythroleukaemia, but it had no effect on the cells of 10 other AML cases. Extrapolation of these in vitro findings would suggest that CSFs would have a limited therapeutic utility to induce AML cell maturation in vivo and that hazards of stimulating blast cell proliferation with these factors may be anticipated.

Difference of cell lineage expression of haematopoietic progenitor cells in Philadelphia-positive acute lymphoblastic leukaemia and chronic myelogenous leukaemia

It is still difficult to clinically distinguish Philadelphia (Ph1)-positive acute lymphoblastic leukaemia (ALL) from Ph1-positive chronic myelogenous leukaemia (CML) in lymphoid crisis. In this study we tried to discriminate between these two disorders by simultaneous analyses of cell morphology and karyotype in single in vitro colonies. We studied three patients with Ph1-positive ALL and four with Ph1-positive CML in various phases of the disease. Bone marrow and peripheral blood cells obtained directly from all seven patients showed abnormal karyotypes including Ph1-chromosomes. Normal karyotypes were found in a small proportion of cells from two ALL patients, but none were found in any from the CML patients. The patients' mononuclear cells (MNCs) were plated at 1-5 x 10(4)/ml in semi-solid medium containing methylcellulose plus phytohaemagglutinin-stimulated leucocyte conditioned medium and erythropoietin. After 9-14 d cultivation, granulocyte-macrophage, erythroid and mixed colonies obtained were used for simultaneous analysis of cell morphology and karyotype. Morphological examination showed that these colonies contained neutrophils, eosinophils, basophils, macrophages and/or erythroblasts in various combinations. No lymphoblast colonies were obtained under the culture conditions used. Cytogenetic examination revealed that all metaphase cells observed in colonies obtained from Ph1-positive ALL patient MNCs had a normal karyotype, whereas those in colonies from Ph1-positive CML patient MNCs had abnormal karyotypes, including Ph1 chromosomes, suggesting that the difference between the two disorders involved a difference in cell lineage. Our results showed that this method was a practicable method for distinguishing Ph1-positive ALL from Ph1-positive CML in lymphoid crisis.

Multilineage expression of haemopoietic precursors with an abnormal clone in idiopathic myelofibrosis

To clarify the lineage involvement of haemopoietic progenitor cells in idiopathic myelofibrosis (MF), simultaneous analysis of morphology and chromosomes were performed on single colonies from a 70-year-old Japanese woman with typical presentation of MF. The cytogenetic analysis of unstimulated peripheral blood cells revealed three cell lines 47,XX,-6,+9,+der(6)t (1;6)(1qter----1q21::6p21----6qter), 46,XX,-6,+der(6) and 46,XX. Of 91 metaphases examined, the numbers of each cell line were 43, 41 and 7, respectively. Blood mononuclear cells were plated at 2 X 10(3) or 1 X 10(4)/ml in methylcellulose medium containing phytohaemagglutinin-stimulated leucocyte conditioned medium and erythropoietin. On days 10, 12 and 14 of culture, 47 individual colonies were lifted and served for morphological and cytogenetic examination. Morphological examination revealed that the colonies contained neutrophils (n), macrophages (m), basophils (b), erythrocytes (E) and megakaryocytes (M). Twenty-two of the 47 colonies had analysable metaphases, yielding totally 158 metaphases. Twelve colonies contained three or more metaphases. Eight colonies (3bE, 1E, 2b, 1nEM, 1bEM) were of the abnormal cell line 46,XX,-6,+der(6), and four colonies (2E, 1bE, 1mE) were of the karyotypically normal cell line 46,XX. The other abnormal cell line 47,XX,-6,+9,+der(6) was not detected in any of the metaphases obtained from single colonies. These results provided direct evidence that the pluripotent stem cells were involved in MF.