Use of bone-marrow culture in prediction of acute leukaemic transformation in preleukaemia

Leukemic cluster growth in culture is an independent risk factor for acute myeloid leukemia and short survival in patients with myelodysplastic syndrome

In patients with myelodysplastic syndrome (MDS) precursor cell cultures (colony-forming unit cells, CFU-C) can provide an insight into the growth potential of malignant myeloid cells. In a retrospective single-center study of 73 untreated MDS patients we assessed whether CFU-C growth patterns were of prognostic value in addition to established criteria. Abnormalities were classified as qualitative (i.e. leukemic cluster growth) or quantitative (i.e. strongly reduced/absent growth). Thirty-nine patients (53%) showed leukemic growth, 26 patients (36%) had strongly reduced/absent colony growth, and 12 patients showed both. In a univariate analysis the presence of leukemic growth was associated with strongly reduced survival (at 10 years 4 vs. 34%, p = 0.004), and a high incidence of transformation to AML (76 vs. 32%, p = 0.01). Multivariate analysis identified leukemic growth as a strong and independent predictor of early death (relative risk 2.12, p = 0.03) and transformation to AML (relative risk 2.63, p = 0.04). Quantitative abnormalities had no significant impact on the disease course. CFU-C assays have a significant predictive value in addition to established prognostic factors in MDS. Leukemic growth identifies a subpopulation of MDS patients with poor prognosis.

Diagnostic and prognostic value of colony formation of hematopoietic progenitor cells in myeloid malignancies

Hematopoietic progenitor cells are capable of forming colonies of mature blood cells in semisolid media in response to specific growth factors. Colony assays have been extensively used for many years to study normal and malignant hematopoiesis in vitro. In fact, these assays have provided an excellent research tool for investigating growth and differentiation of progenitor cells in response to positive and negative regulators of hematopoiesis. However, apart from their role in basic research, colony assays are also widely used in routine clinical practice in the diagnosis of various hematologic disorders, such as aplastic anemia, myelodysplastic syndromes and myeloproliferative disorders. This review summarizes our current knowledge on the diagnostic value and prognostic significance of the growth of progenitor cells in peripheral blood and bone marrow in patients with myeloid malignancies.

Circulating myeloid colony-forming cells predict survival in myelodysplastic syndromes

The growth characteristics and the prognostic value of cytokine-stimulated myeloid colony formation from peripheral blood mononuclear cells (PBMC) of patients with myelodysplastic syndromes (MDS) are largely unknown. In this study we have determined the number of myeloid colony-forming units (mCFUs) in semisolid medium from 112 MDS patients and correlated them with French-American-British (FAB) type, the international prognostic scoring system (IPSS), karyotype, peripheral blood (PB) and bone marrow (BM) blast cells, cytopenias, lactate dehydrogenase (LDH), and survival data. Concerning the FAB classification, lower median mCFUs were found in patients with refractory anemia (RA) and refractory anemia with ringed sideroblasts (RARS) compared to refractory anemia with excess of blast cells (RAEB) and refractory anemia with excess of blasts cells in transformation (RAEB-T). In vitro growth in MDS clearly correlated with the cytogenetic risk groups defined by the IPSS (30.5/10(5) PBMCs with favorable karyotypes, 191 in the intermediate prognostic group, 677 with unfavorable cytogenetics, p=0.015 favorable vs unfavorable). BM blast cells >5% (60.5 vs 255 colonies, p=0.032) as well as LDH levels above the normal limit (64.5 vs 425 colonies, p=0.045) were also associated with higher colony formation. Patients were stratified according to the number of circulating mCFUs into a low growth, intermediate growth and high growth group. Median survival was 343 days in the high growth, 1119 days in the low growth, and 2341 days in the intermediate growth group ( p=0.0002). Multivariate analyses revealed colony growth ( p=0.0056), PB blast cells ( p=0.0069), cytogenetic risk group ( p=0.024), and platelet count ( p=0.018) to predict survival in our patients. After inclusion of the IPSS risk categories, mCFU levels remained a highly predictive parameter for survival ( p=0.0056) and acute myeloblastic leukemia (AML) transformation ( p=0.0003).

The prognostic value of in vitro cultures of erythroid and megakaryocyte progenitors in myelodysplastic syndromes

The prognostic value of colony formation by granulocyte-macrophage progenitors (CFU-GM) in myelodysplastic syndromes (MDS) has been investigated in several studies. We studied the in vitro growth patterns of hematopoietic progenitors of 83 patients with an MDS to find out whether erythroid (BFU-E) and megakaryocyte (CFU-Meg) cultures yield additional prognostic information to that obtained with CFU-GM cultures. Thirty-nine of 82 patients showed normal CFU-GM colony formation; the others had either excessive growth of colonies/clusters or reduced growth. Five of 74 patients had normal BFU-E and nine of 39 patients normal CFU-Meg growth; the others showed reduced or absent colony formation. The cultures of each cell lineage had a similar prognostic impact: the patients with a normal growth pattern had a lower risk of developing leukemia and a longer survival than those with an abnormal growth pattern (significant difference or trend). All patients with normal BFU-E or CFU-Meg colony growth also had normal CFU-GM colony formation, and all patients with normal BFU-E growth also had normal CFU-Meg growth. Among the patients with normal CFU-GM cultures, those with normal erythroid or megakaryocyte colony formation had a trend towards a better outcome compared to those with an abnormal growth pattern in the same cell lineage. In conclusion, erythroid and megakaryocyte cultures did not significantly contribute to the prognostic information obtained with CFU-GM cultures in MDS.

Investigation of the effects of 50 Hz magnetic fields on purified human hematopoietic progenitors

Epidemiological reports suggest a possible association between exposure to extremely low frequency electromagnetic fields (ELF-EMFs) and the frequency of leukemia in men working in the field of electricity or in children living near power lines. At present, there is no experimental evidence for such an association. In this study we investigated the effects of 50 Hz EMFs (sinusoidal EMF of 10 microT or 1 mT) on human purified hematopoietic progenitor cells which are the first targets of a leukemogenic process. The results failed to reveal any significant changes in cell proliferation, cell kinetics, ultrastructure or clonogenic potential of these progenitors which could be related to a leukemogenic effect.

Producton of tumor necrosis factor and granulocyte colony stimulating factor by bone marrow accessory cells in myelodysplastic patients

This paper reports on the production of tumor necrosis factor (TNF) and granulocyte macrophage colony-stimulating factor (GM-CSF) by cultured mononuclear adherent cells derived from bone marrow of 25 patients affected by myelodysplastic syndrome (MDS) of different FAB subtypes. Mean production of GM-CSF was much lower than in controls, without significant differences among different subtypes. Mean production of TNF was similar in MDS patients and in controls, but noteworthy differences were observed between patients with RA, RAEB and RAEB-t and patients with RARS and CMML. Growth of bone marrow granulocyte macrophage and erythroid progenitors did not correlate with TNF and GM-CSF production, although in MDS subtypes with higher GM-CSF levels, colony growth was slightly higher than in subtypes with lower GM-CSF production.

c-kit ligand augments granulocyte-macrophage colony growth from patients with 5q- syndrome

In vitro studies may serve as a guide to clinical strategies with cytokines. In this study, marrows from 26 patients with myelodysplastic syndrome (MDS) were assayed for myeloid progenitor cells in agar gel. Colony stimulating activity was provided by the recombinant human colony stimulating factors granulocyte-macrophage colony stimulating factor (GM-CSF), granulocyte colony stimulating factor (G-CSF), interleukin 3 (IL-3), fusion protein (FP), c-kit ligand (KL) or GM-CSF combined with other cytokines (KL, IL-3). Decreased colony forming units granulocyte-macrophage (CFU-GM) were detected in most cases (69%) compared with normal controls. Neither FP nor the combination of GM-CSF + IL-3 produced more colonies than GM-CSF alone. The number of CFU-GM did not correlate with French American British (FAB) class. All marrows (7) from patients with 5q- showed augmentation of GM-CSF induced colonies with the addition of KL. In contrast, KL augmentation was noted in only 42% of other MDS marrows (p = 0.01). This in vitro result suggests that 5q- may predict a group of MDS patients with a likelihood to respond to the combination of GM-CSF + KL.

Impairment of GM-CSF production in myelodysplastic syndromes

In this study we evaluated the production of granulocyte/macrophage-colony stimulating factor (GM-CSF), interleukin-6 (IL-6) and tumour necrosis factor-alpha (TNF-alpha) by enriched bone marrow (BM) macrophages in 15 patients affected by myelodysplasia and 20 normal BM donors. The presence of GM-CSF, IL-6 and TNF-alpha in the culture supernatants of BM macrophages was detectable only after stimulation with lipopolysaccharide (LPS), whereas no differences were present in the amount of IL-6 and TNF-alpha between myelodysplastic patients and normal controls, GM-CSF production appeared eight-fold reduced in BM macrophage culture supernatants from myelodysplastic patients with respect to normal controls. After further experiments, we concluded that the impaired release of GM-CSF by BM macrophages could not be due to a different production kinetic in myelodysplastic patients. Moreover, the number of multipotent (CFU-GEMM), granulocyte/macrophage (CFU-GM) and erythroid (BFU-E) progenitors was significantly impaired in myelodysplastic patients. In conclusion, we demonstrated that the production of GM-CSF by purified adherent cells from MDS patients is markedly impaired in spite of the peripheral blood cytopenia. This selective defect in GM-CSF production, along with an intrinsic defect of haematopoietic progenitor cells, might contribute to the impairment of haematopoiesis always observed in myelodysplastic patients.

Myelodysplastic syndromes: immunohistochemical and morphometric evaluation of proliferative activity in erythropoiesis and endoreduplicative capacity of megakaryocytes

An immunohistochemical and morphometric analysis was performed on bone marrow trephine biopsies in 40 patients with primary myelodysplastic syndromes (MDS) to evaluate the proliferative activity in erythropoiesis and the endoreduplicative capacity of megakaryocytes. Control groups included normal bone marrow and marrow from cases presenting with pernicious anaemia. Double-immunostaining was applied with a monoclonal antibody (PC10) directed against proliferating cell nuclear antigen (PCNA), followed by antibodies against glycophorin C (Ret40f) or platelet glycoprotein IIIa (Y2/51-CD61) for the identification of the erythroid and megakaryocytic cell lineage. Comparison with normal bone marrow showed a reduction of erythropoiesis accompanied by an increase in atypical (micro-) megakaryocytes. Erythroid precursors displayed significant enhancement of PCNA-immunostaining. Megakaryocytes showed no increase in the relative frequency of PC10-positive cells (PCNA-labelling index). In pernicious anaemia, predominance of macrocytic-megaloblastoid erythropoiesis was associated with a striking increase in PCNA-labelling. Cell kinetic studies in this disorder revealed an abnormal arrest, particularly in S-phase which generates an over-expression of PCNA. Similar conditions were believed to be present in MDS with secondary folate deficiency. This mechanism explains the relatively high rate of positively-reacting pro- and erythroblasts which is not invariably accompanied by an increase in cell proliferation. Determination of megakaryocyte size and PCNA-staining capacity resulted in a significant increase in PC10-positive cells among micromegakaryocytes. Our findings on this cell lineage are in keeping with the assumption of a block in endoreduplicative activity at higher ploidy levels, associated with an apparently not-deregulated endomitosis in small-sized megakaryocytes of lower ploidy stages.

Macrophages (phagocytic-histiocytic reticular cells) in reactive-inflammatory lesions of the bone marrow and in myelodysplastic syndromes (MDS). An immunohistochemical and morphometric study by use of a new monoclonal antibody (PG-M1)

An immunohistochemical and morphometric study was performed on trephine biopsies of the bone marrow in 52 patients (28 males/24 females; age 68 years) with various subtypes of myelodysplastic syndromes (MDS) to determine the number of macrophages (phagocytic-histiocytic reticular cells). Quantifications included the haemosiderin-storing subpopulation (Prussian-blue reaction) of this lineage as well as the iron-free compartment. The latter was identified by a new monoclonal antibody (PG-M1) which is specifically directed against histiocytic reticular cells. Bone marrow specimens of individuals without haematological disorders and those showing reactive lesions served as controls. In comparison with the normal bone marrow and inflammatory changes (i.e. rheumatoid arthritis) 23 of the 52 patients with MDS revealed a significant increase in macrophages. This increase encompassed not only the iron-laden subpopulation but also the total number of phagocytic reticular cells. Accumulation of macrophages in MDS was speculated to be due to a premature and enforced degradation of dysplastic cell elements leading to phagocytosis of haemosiderin and debris material. Moreover, cells of the monocyte-macrophage system could be involved in the complex pathomechanism of fibrillogenesis, since in a considerable percentage of patients with MDS, an increase in reticulin (argyrophilic) fibres was noticeable. Our finding of an expansion of the macrophage compartment in about half of the patients with MDS is in keeping with results of cell culture studies on colony formation of granulocyte-macrophage precursors (CFU-GM).

Myelodysplastic syndrome (MDS)-associated inhibitory activity on haematopoietic progenitor cells: contribution of monocyte-derived lipid containing macrophages (MDLM)

We studied myelodysplastic syndrome-associated inhibitory activity (MDS-IA), which inhibited colony formation in vitro of normal granulocyte-macrophage progenitors (CFU-GM). When adherent marrow cells were incubated with fetal calf serum for 21-24 d, monocyte-derived lipid containing huge macrophages (MDLM) developed. MDLM from MDS marrow (MDS-MDLMs) and their conditioned medium (MDLM-CM) consistently suppressed the growth of normal CFU-GM colony formation. MDS-IA was active on CFU-GM during the S-phase and relatively resistant to heating. Monoclonal antibody against H subunit (acidic) ferritin and polyclonal antibody against placental ferritin neutralized the inhibitory activity of MDS-MDLMs. In addition, cell lysates of MDS-MDLMs reacted to both monoclonal anti-H subunit ferritin and polyclonal anti-placental ferritin in Western blotting analysis, indicating that the inhibitory activity was predominantly acidic isoferritin. On the other hand, MDLMs obtained from normal bone marrow had a CFU-GM enhancing activity. These results suggest that MDS-MDLMs may be responsible for the suppression of granulopoiesis in patients with MDS and that the suppression may be mediated by soluble factors, notably H subunit isoferritin.

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.

Functional studies of bone marrow haemopoietic and stromal cells in the myelodysplastic syndrome (MDS)

Long-term bone marrow culture (LTBMC) was used to investigate the proliferative behaviour of marrow cells from a spectrum of cases of the myelodysplastic syndrome (MDS), and the results compared with those obtained in the conventional short-term clonal assay. Two broad patterns of growth were revealed in LTBMC. In one group the incidence of haemopoietic progenitor cells steadily declined to abnormally low levels at 4 weeks, while in a second group they were maintained near normal levels for periods of up to 7 weeks. These growth patterns, which were not predictable from clonogenic assays on the marrow cells prior to LTBMC, or from the morphology of the bone marrow, may reflect the stage of evolution of the disease. Further studies of clonality are required to establish whether or not patients exhibiting the second pattern have a potentiality to harbour residual normal haemopoiesis. LTBMC was also used to study the function of MDS marrow stroma in terms of its ability to sustain the growth of normal haemopoietic progenitor cells. Although the phenotype of the cultured adherent cell layer, obtained from some patients, was atypical, no consistent functional defect of MDS stroma could be identified by studying the level of haemopoiesis reached by normal cells seeded into MDS stroma.

Myelodysplastic syndrome (MDS)-associated inhibitory activity on haemopoietic progenitor cells

We studied MDS-associated inhibitory activity, which inhibited colony formation in vitro of granulocyte-macrophage progenitors (CFU-GM). Macrophages obtained from MDS bone marrow mononuclear cells (BM-MNC) when pretreated with granulocyte-macrophage colony stimulating factor (GM-CSF) suppressed the growth of normal CFU-GM. These macrophages were designated as 'MDS-derived inhibitory macrophages'. Media conditioned by MDS-derived inhibitory macrophages (MDS-CM) also suppressed the growth of normal CFU-GM. In the MDS-CM, high levels of prostaglandin E2 (PGE2) and ferritin were found. However, MDS-CM did not contain detectable levels of tumour necrosis factor (TNF) or gamma-interferon (gamma-IFN). Antiserum against human placental ferritin and/or against PGE2 blocked the haemopoietic inhibitory activity to some extent. These results suggest that inhibitory macrophages may be responsible for the suppression of granulopoiesis in patients with MDS and that the suppression may be mediated by soluble factors including PGE2 and ferritin.

Bone marrow cultures and prognosis in primary myelodysplastic syndromes

Bone marrow cultures and survival time were studied in 39 patients with primary myelodysplastic syndromes. We divided the patients into two groups according to the CFU-GM numbers on day 10: type I with low colony (CFU-GM less than 30) and type II with normal to high colony formation (CFU-GM greater than or equal to 30). The median survival time was shorter for patients with an in vitro growth type II (5 months) than it was for patients with an in vitro growth type I (greater than 36 months). No relations was found between growth types and FAB-type, Bournemouth score or initial karyotype. The initial bone marrow blast percentage correlated well with the in vitro growth number.

Pathobiology of myelodysplastic syndromes

The myelodysplastic/preleukemic syndromes represent unique clinical situations since patients with initially mild hemopoietic abnormalities can be singled out from those progressing into frank myeloid leukemia. Here we confront data focused on the identification of critical cellular, molecular biological, cytogenetic and physiological defects leading to leukemic progression. An increasing amount of data supports our earlier hypothesis according to which the impairment of an endogenous (intracellular) life-cycle suppressor gene-product, or functionally related regulatory genes, plays the decisive role in the course of disease progression. The identification of systemic as well as clonally transmissible defects have clinical importance since in some cases the therapeutic application of the appropriate physiological substances may result in long lasting hematological remission.

Regulatory abnormalities in the marrow of patients with myelodysplastic syndromes

Regulation of haemopoiesis in the marrow of patients with myelodysplastic syndromes (MDS) was evaluated by assaying (1) the production of haemopoietic regulators acting upon multipotent and committed progenitors by MDS marrow cells, and (2) the responsiveness of MDS marrow progenitors to stimulation with granulocyte colony-stimulating factor (G-CSF). The levels of multipotent progenitor cell colony-stimulating activity (CFU-GEMMCSA) in 7 d bone marrow-conditioned medium (BMCM) from MDS patients were markedly reduced as compared to controls. MDS BMCM also exhibited reduced levels of burst-promoting activity (BPA) for primitive erythroid (BFU-E) progenitors. Both CFU-GEMMCSA and BPA detected in BMCM were completely neutralized by antibodies directed against interleukin-3. MDS BMCM exhibited markedly reduced levels of murine-active CSA. This activity was partially neutralized by anti-CSF-1 antibodies. Levels of regulators in BMCM of refractory anaemia (RA), sideroblastic anaemia. RA with excess blasts, and chronic myelomonocyte leukaemia were virtually the same. CFU-GEMM and BFU-E growth in MDS marrow (n = 9) was markedly reduced. A 5-fold saturating dose of G-CSF induced an approximately 2-fold increase in CFU-GEMM in four of eight MDS and a 1.5-fold increase of BFU-E in five of nine MDS, but not in control (n = 5) marrow cell cultures. Impaired haemopoiesis in MDS marrow may be related to abnormalities both in regulator production by marrow accessory cells and in regulator responsiveness of multipotent and committed progenitors.

Enrichment of haemopoietic progenitor cells from the marrow of patients with myelodysplasia

Myeloid and erythroid progenitors from myelodysplastic marrows have been separated from accessory cell populations likely to influence their in-vitro growth. Myeloid colony-forming cells were enriched 23-fold and erythroid progenitors 5-7-fold but, in both cases, retained their abnormal growth characteristics. After enrichment and removal of lymphocytes and monocytes, erythroid burst formation became markedly more dependent on the addition of 5637 bladder carcinoma conditioned medium as an exogenous source of haemopoietic growth factors. This suggests that lymphocytes and monocytes usually support erythropoiesis in cultures of myelodysplastic marrow and demonstrates that erythroid burst-forming progenitor cells from myelodysplastic patients can respond to these populations in vitro. Haemopoietic failure in myelodysplasia appears to result from a defect within the preleukaemic clonogenic cell, rather than from an aberration in exogenous factors. The procedure outlined here can be used as a first step towards the isolation of these abnormal progenitors.

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.

Leukocyte-derived inhibitory activity in patients with myelodysplastic syndrome

Leukocyte-derived inhibitory activity inhibiting the entry of normal progenitor cells of granulocytes and macrophages (CFU-GM) into the S-phase of a cell cycle was investigated in 16 patients with different forms of myelodysplastic syndrome (MDS). The presence of this inhibitory activity was analysed in medium conditioned with low-density cells obtained from peripheral blood of MDS patients. The inhibition rate was measured by 3H-thymidine suicide technique with subsequent cultivation of pretreated cells in semisolid agar medium. Low-density cells from MDS patients of various types were studied: from the twelve patients with refractory anaemia (RA or RAS) only three were positive, one patient with chronic myelomonocytic leukaemia (CMML) was negative while one patient with refractory anaemia with excess of blasts (RAEB) and two patients with RAEB in transformation (RAEB-T) were positive with respect of the described test. In two patients with RA, who underwent a long-term investigation, the production of leukocyte-derived inhibitory activity preceded the development of disease into RAEB or RAEB-T. In five positive cases, supernatants were incubated with antiserum against human placental ferritin; with one exception, the inhibitory activity was neutralized.

Significance of in vitro cultures in myelodysplastic syndromes

Bone marrow samples from 20 controls, 41 patients suffering from various types of myelodysplasia and 19 suffering from ANLL were investigated by in vitro cultures. The cultures were stimulated by various concentrations of leucocyte conditioned medium (LCM) and PHA-stimulated conditioned medium (PCM) and were examined after 7 and 14 d. We found that, in clinically stable MDS, growth patterns and dose-response to CM's were mostly within the normal range. With progressive blastic transformation, these features became abnormal with an increase in cluster growth. Clusters responding to a high dose of LCM, persisting after 14 d and enhanced by PCM may represent 'early' clonogenic cells. These clusters were found in progressive MDS with increased numbers of blast cells. Clusters formed by 'late' clonogenic cells were found in normal bone marrow and stable MDS. In ANLL the disturbance of proliferation and maturation seems to be much more pronounced than in progressive MDS with blastic transformation. We conclude that the interpretation of in vitro bone marrow culture data in terms of a disorderly arrangement of clonogenic cells in MDS and ANLL is facilitated by comparing different conditioned medium stimulations and by scoring after different time intervals.

The concept of preleukemia: clinical and laboratory studies

Thirty-five years ago, a handful of astute clinical hematologists began to notice that some of their patients with acute nonlymphocytic leukemia had a history of a preceding ill-defined hemopathy. This "preleukemic" hemopathy was increasingly reported anecdotally and through careful retrospective analyses. In more recent prospective studies, this syndrome has been relatively well defined. Indeed, it is widely accepted that there exists a hematopoietic abnormality not recognizable as classical, overt, acute nonlymphocytic leukemia, which, nonetheless, can represent an early phase of leukemia. In this manuscript, the author reviews the original case reports, the initial retrospective studies, and the prospective studies which have clarified some of the clinical and laboratory features of the preleukemic syndrome. The notion that the preleukemic syndrome represents an established neoplastic process will be reviewed with special attention to assessment of clonal hematopoiesis, cytogenetic studies, and clonal evolution. Studies on induced leukemia and preleukemia in experimental animals and humans will be reviewed as will be the semantic issues which have complicated our ability to compare interinstitutional studies. A simple classification scheme of the myelodysplastic syndromes will be presented as will be a framework agenda for future studies on the pathophysiology of these syndromes.

The technique of premature chromosome condensation to study the leukemic process: review and speculations

The technique of premature chromosome condensation involves the fusion of mitotic cells with interphase cells resulting in the immediate condensation of the interphase chromatin into discrete chromosome units, the prematurely condensed chromosomes (PCC). The ability to visualize the interphase chromosomes of bone marrow and blood cells by this technique has proved useful in the study of human leukemia. This article describes how the PCC technique has been used to predict clinical outcome as well as gain insight into the biology of leukemia.

Myelodysplastic syndromes: pathogenesis, functional abnormalities, and clinical implications

The myelodysplastic syndromes represent a preleukaemic state in which a clonal abnormality of haemopoietic stem cell is characterised by a variety of phenotypic manifestations with varying degrees of ineffective haemopoiesis. This state probably develops as a sequence of events in which the earliest stages may be difficult to detect by conventional pathological techniques. The process is characterised by genetic changes leading to abnormal control of cell proliferation and differentiation. Expansion of an abnormal clone may be related to independence from normal growth factors, insensitivity to normal inhibitory factors, suppression of normal clonal growth, or changes in the immunological or nutritional condition of the host. The haematological picture is of peripheral blood cytopenias: a cellular bone marrow, and functional abnormalities of erythroid, myeloid, and megakaryocytic cells. In most cases marrow cells have an abnormal DNA content, often with disturbances of the cell cycle: an abnormal karyotype is common in premalignant clones. Growth abnormalities of erythroid or granulocyte-macrophage progenitors are common in marrow cultures, and lineage specific surface membrane markers indicate aberrations of differentiation. Progression of the disorder may occur through clonal expansion or through clonal evolution with a greater degree of malignancy. Current attempts to influence abnormal growth and differentiation have had only limited success. Clinical recognition of the syndrome depends on an acute awareness of the signs combined with the identification of clonal and functional abnormalities.

Predictive value of bone marrow cultures in 48 patients with acute myeloblastic leukaemia or myelodysplasia both secondary to treatment of other malignant diseases

The growth pattern of bone marrow cells in agar cultures was studied in 48 patients with acute myeloblastic leukaemia or myelodysplasia, secondary to cytoreductive treatment, and compared to other laboratory findings. At diagnosis the status of the patients was: acute myeloblastic leukaemia (AML) in 9, acute myeloproliferative syndrome (AMS) in 13 and preleukaemic syndrome (PL) in 26 patients. 20 of the 39 patients with AMS and PL developed acute leukaemia, 15 of them within 1 year. 15 died of complications to cytopenia and only 4 are still alive and without leukaemia, observed from 8 to 55 months. Progression to AML was predicted from the agar cultures by increased cluster growth. Among 18 patients with increased cluster growth at diagnosis 14 subsequently developed AML. Among 21 patients with normal or decreased cluster growth at diagnosis 6 patients developed AML, but after conversion of the growth pattern to increased cluster growth. In 2 patients the increased cluster growth disappeared spontaneously and the patients are long-term leukaemia-free survivors. Colony growth pattern, conversely, was not related to leukaemic progression. Only 1 patient had normal growth pattern at diagnosis with respect to both clusters and colonies. Survival was short, with a median of about 7 months, unrelated to growth pattern and leukaemic progression.

Growth of solid tumor cells in clonogenic assays: a prognostic factor?

Clonogenic assays can be used to study several characteristics of hemopoietic and solid tumor cells. Treatment of ovarian cancer patients, anticancer drug development and studies of tumor cell biology (self-renewal and cytogenetics) seem to be facilitated by these techniques, in spite of their limitations. This paper reviews data showing that good in vitro clonal growth might be a poor prognostic factor. These results are remarkable but only few patients have been studied and detailed analyses looking at other prognostic factors are lacking. However, studies of in vitro growth characteristics of hemopoietic malignancies have shown similar results. Further follow-up should substantiate these initial findings in solid tumors.

Erythroid and granulocyte-macrophage colony formation in myelodysplastic syndromes

Colony formation by haematopoietic progenitors from the bone marrow was studied in 44 patients with a myelodysplastic syndrome. Erythroid progenitors BFU-E and CFU-E were cultured in methyl cellulose, and granulocyte-macrophage precursors CFU-GM in agar. 3 of 32 patients showed normal numbers of BFU-E colonies; in all the other cases the number of these colonies was below the normal range. CFU-E colony formation was subnormal in all cases. 23 of 44 patients grew normal numbers of colonies and clusters in CFU-GM cultures. These patients had refractory anaemia with ring sideroblasts (FAB-classification) or 5q-karyotype anomaly in the marrow. Patients lacking both of these findings exhibited reduced colony formation or excessive growth of colonies and/or clusters, with few exceptions. In conclusion, we found that erythroid colony formation was defective in all cases. Normal granulocyte-macrophage colony formation was associated with refractory anaemia with ring sideroblasts or the presence of 5q- karyotype anomaly.