Erythropoietin-independent erythroid colony formation in patients with erythroleukaemia (M6) and related disorders

The predictive value of clonogenic stem cell assays for the diagnosis of polycythaemia vera

Spontaneous growth of erythroid progenitor cells is one of the hallmarks of polycythaemia vera (PV). In vitro clonogenic assays can be used to support the diagnosis of PV. However, clonogenic assays are difficult to standardize, and their diagnostic value is accepted as a minor criteria for PV only in the case of positive results. Clonogenic assays need to be validated and normal ranges established carefully before they can be used for diagnostic purposes. In a retrospective study, we analysed the results of 146 consecutive clonogenic assays performed in patients with erythrocytosis between January 1992 and December 2000. Normal ranges were established on the basis of the results from 81 controls. The charts of the 146 patients were reviewed and the patients were allocated to the following diagnostic groups: PV (n = 38) and non-primary erythrocytosis (NPE, n = 65) according to the criteria of Pearson & Messinezy. In total, 43 patients were excluded from the study because of missing data. The clonogenic assay results were correlated with the final clinical diagnosis of the patients. At a cut-off value of 5 erythroid colony-forming unit colonies per well, 29 out of 38 patients with PV showed positive results, and 9 out of 38 patients showed false-negative results. In the NPE group, there were 64 out of 65 real-negative results and 1 out of 65 false-positive result. Thus the positive predictive value of the clonogenic assay for the diagnosis of PV was 97%. We conclude that clonogenic assays, in the case of positive results, and if carefully validated, are very useful and reliable tools for the diagnosis of PV.

Myelodysplastic syndromes. Pathogenesis, diagnosis and treatment

Our understanding of the biology of leukemia and myelodysplasia is still only partial. The diagnosis of myelodysplasia is often based on quantitative and qualitative findings in the peripheral blood and bone marrow. These findings are often shared by other disorders. There is a need for sensitive and inexpensive laboratory tests to determine clonality and karyotypic abnormalities in this disorder. Future classifications of these syndromes will need to be based on morphologic and biologic markers that are closely linked to disease progression, response to treatment, and survival. Our limited understanding of the pathogenesis of MDS decreases the specificity and effectiveness of our therapeutic interventions. Agents that are minimally toxic such as CRA, danazol, 1,25-dihydroxyvitamin D3, androgens, and pyridoxine are seldom useful. Antileukemic therapy and allogeneic bone marrow transplantation have a major role to play in patients younger than 45 years of age; in older patients these treatment modalities remain controversial because of their toxicity. Hematopoietic growth factors, used alone or in combination, may improve the quality of life and improve survival of patients with MDS. Growth factors may also decrease treatment-related mortality associated with chemotherapy and bone marrow transplantation and render these treatment modalities available for a higher percentage of patients. The development of more specific differentiating agents may permit hematopoietic differentiation while minimizing side effects.

Autocrine stimulation by erythropoietin and autonomous growth of human erythroid leukemic cells in vitro

Autonomous colony formation is a frequent event in erythroleukemia. In 13 cases of early erythroid leukemias, we investigated whether erythropoietin (Epo) autocrine stimulation was responsible for the growth factor autonomy. Epo transcripts were detected by Northern blotting in cells from one patient. These cells also expressed an Epo receptor (1,000 receptors per cell) with a 420-pM affinity and Epo was detected in the supernatant of cultured cells. In 8 of the 13 cases, Epo transcripts were revealed by the polymerase chain reaction ranging from 0.5 to 500 copies per cell. In situ hybridization proved that these Epo transcripts were present in the blast cells. No Epo gene abnormalities were detected by Southern blotting. In two cases, leukemic cells were grown in the presence of Epo-neutralizing antibodies or Epo antisense oligomers. In one case, the antibody significantly reduced autonomous growth. In contrast, the antibody had no effect in the second case in which blast cells transcribed the Epo gene at a low level. However, Epo antisense oligomers partially inhibited autonomous growth. This inhibition was reversed by addition of exogenous Epo. Overall, these results suggest that an extracellular or intracellular autocrine Epo stimulation occurs in some cases of erythroid malignancies.

Endogenous BFU-E in peripheral blood in diagnosis of polycythemia vera

Erythroid progenitors (CFU-E and BFU-E) growth in vitro from bone marrow and peripheral blood of patients with polycythemia vera (PV) was studied using a methylcellulose culture technique. The aim of the study was to find out whether the in vitro colony formation of peripheral blood could be used in the differential diagnosis of PV. In all 25 patients studied, endogenous colonies were found in the bone marrow and peripheral blood. The parallel study of both bone marrow and peripheral blood erythroid progenitors indicates that the presence of endogenous BFU-E in peripheral blood is a dependable test for PV. The results presented here showed that the abnormalities in PV erythroid progenitors are expressed at the level of both CFU-E and BFU-E, suggesting multiple changes in the erythroid progenitors. Our finding indicate that peripheral blood BFU-E differ from bone marrow BFU-E with regard to their dependence for further differentiation on BPA, the activity present in PHA-LCM.

Spontaneous erythroid colony formation in the differential diagnosis of erythrocytosis

Erythroid colony formation in vitro was studied in 80 patients with erythrocytosis. 43 of the patients had polycythaemia vera (PV), 18 patients had secondary erythrocytosis, 6 had normal red cell mass, and 13 patients were regarded as unclassified. Spontaneous erythroid colony formation, in the absence of exogenous erythropoietin in the cultures, was discovered in all patients with PV, whereas no patient with secondary erythrocytosis or with normal red cell mass showed this phenomenon. 8 of the 13 patients with unclassified erythrocytosis spontaneously formed erythroid colonies. 7 patient with unclassified erythrocytosis have been followed for 5 yr. 3 of the 4 patients with spontaneous colony growth but none of the 3 without it can now be classified as PV. Thus, spontaneous erythroid colony formation indicates PV even in early and atypical cases. Therefore, the culture of erythroid progenitors is very useful in the differential diagnosis of problematic cases with erythrocytosis.

The production of myeloid blood cells and their regulation during health and disease

The regulation of myelopoiesis in vivo most likely entails a complex set of interactions between cell-derived biomolecules and their target cells: hematopoietic stem and progenitor cells and accessory cells. Stimulating and suppressing factors have been characterized through in vitro studies, and their mechanisms of action in vitro and in vivo have begun to be elucidated. Among those factors being studied are the hematopoietic colony-stimulating factors (CSF): interleukin-3 (multi-CSF), granulocyte-macrophage-CSF, granulocyte-CSF, and macrophage-CSF; other molecules include erythropoietin, B-cell-stimulating factor-1, interleukin-1, interleukin-2, prostaglandin E, leukotrienes, acidic ferritins, lactoferrin, transferrin, the interferons-gamma, -alpha, and -beta, and the tumor necrosis factors-alpha and -beta (lymphotoxin). These factors interact to modulate blood cell production in vitro and in vivo. The proposed review characterizes these biomolecules biochemically and functionally, including receptor-ligand interactions and the secondary messengers within the cell which mediate their functional activity. The production and action of the molecules are described under conditions of hematopoietic disorders, as well as under normal conditions. Studies in vitro are correlated with studies in vivo using animal models to give an overall view of what is known about these molecules and their relevance physiologically and pathologically.

Biology of myelodysplastic syndromes

Myelodysplastic syndromes (MDS) represent a diverse spectrum of disorders ranging from refractory anemia to a preleukemic state. Peripheral cytopenias, cellular marrow, dysplasias and dysfunctions of myeloid and lymphoid cells constitute hematological hallmarks, and are caused by ineffective hemopoiesis. Investigations of cell cultures and cellular functions indicate that the disease originates in a stem cell pluripotent to all myeloid cells and possibly lymphoid cells as well. The disease commonly runs a chronic indolent course, often terminating in acute leukemia or nonleukemic death, notably infections and/or hemorrhage due to cytopenias and cellular dysfunctions. Clonal expansion or clonal evolution appears to be related to the disease progression with a greater degree of malignancy. However, the initial sequence of events causing damage to stem cells is still undefined.

Juvenile monosomy 7 syndrome: evidence that the disease originates in a pluripotent hemopoietic stem cell

The present study was undertaken to investigate the hemopoietic cell from which malignant change evolves in juvenile dyshemopoiesis with monosomy 7. Two male patients, aged 18 and 5 months, were studied using progenitor assays combined with cytogenetics. Both had hepatosplenomegaly, cytopenias and a cellular marrow. The karyotype in direct marrow was 45,XY-7/47,XY,+8/46,XY in patient 1 and 45,XY,-7/46,XY in patient 2. Patient 1 received chemotherapy but developed acute nonlymphocytic leukemia after 17 months and died 20 months after diagnosis. During this time marrow metaphases with 45,XY,-7 increased to 100% (25/25). Patient 2 received an allogeneic marrow transplant 4 months after diagnosis which did not engraft. In both patients progenitors of both small (CFU-E) and large (BFU-E) erythroid colonies were present at normal frequencies. However, the colonies produced were small and poorly hemoglobinized with some erythropoietin-independent maturation. Progenitors of large granulocyte/macrophage colonies (CFU-GM) were present at an elevated frequency in the marrow of patient 1 and in the blood all progenitor classes were markedly increased. Cytogenetic analysis of colonies from this patient showed BFU-E to be 45,XY,-7 or 47,XY,+8 and CFU-GM to be 45,XY,-7 or 47,XY,+8 or 46,XY. In patient 2, most BFU-E were 45,XY,-7, although a few were 46,XY. These data indicate that malignant change in this disease involves hemopoietic stem cells capable of erythroid and in at least some cases, myeloid differentiation.

Polycythemia and the Budd-Chiari syndrome: study of serum erythropoietin and bone marrow erythroid progenitors

The mechanism of polycythemia associated with the Budd-Chiari syndrome is unknown. Erythropoiesis in 10 patients with Budd-Chiari syndrome was studied in an attempt to distinguish prior unrecognized polycythemia vera from secondary polycythemia. Serum erythropoietin was assayed using a mouse fetal liver erythroblast assay. High concentrations of serum erythropoietin were observed in 6 of 7 patients with acute primary Budd-Chiari syndrome. Levels were normal in four patients who were investigated during the chronic phase and were increased in one with persisting polycythemia. In one patient, erythropoietin concentration in the hepatic vein was twice the level measured in peripheral, caval and renal venous blood. Bone marrow erythroid progenitors developed in vitro in the absence of exogenous erythropoietin in all polycythemia vera cases studied in acute and chronic phases, whether polycythemia persisted or not. These findings indicate that hepatic erythropoietin production occurs in the acute phase of Budd-Chiari syndrome and suggest that, in some cases of Budd Chiari syndrome, polycythemia which resolves after the acute phase may be secondary to liver disease.

Colony assays of hematopoietic progenitor cells and correlations to clinical situations

The production of blood cells is a dynamic process that is noticeably aberrant during disease. The availability of colony assays in vitro that allow detection of hematopoietic stem and progenitor cells for the neutrophil, monocyte-macrophage, erythroid and/or megakaryocyte lineages has been of importance for the present understanding of the mechanisms controlling the proliferation, self-renewal capacity, and differentiation of morphologically nonrecognizable immature cells which give rise to the mature progeny circulating in the blood. It is through the use of these assays that the existence of potentially relevant stimulatory and inhibitory feedback interactions has been demonstrated. Abnormalities in these interactions, which may be of significance during leukemia and related disorders, have been uncovered. This communication will discuss regulatory interactions detected via the colony assays, their potential relevance physiologically and pathologically, and the use of these assays for diagnosis, prognosis, and for monitoring the clinical status of patients.