In vitro growth pattern and differentiation predict for progression of myelodysplastic syndromes to acute nonlymphocytic leukaemia

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.

Bone marrow mononuclear cells of MDS patients are characterized by in vitro proliferation and increased apoptosis independently of stromal interactions

Enhanced proliferation of MDS progenitors is abrogated by increased apoptosis of their progeny in vivo. We investigated whether bone marrow mononuclear cells (BMMNC) of MDS patients also showed enhanced proliferation and apoptosis in vitro in comparison with acute myeloid leukemia (AML) and normal BM (NBM). NBM showed a decrease in the number of clusters in time due to apoptosis of clusters and due to development of clusters into colonies with low apoptotic level. In MDS patients, about two-fold more clusters have developed at day 4, and in contrast with NBM, the total number of clusters at day 7 remained high in spite of an increasing percentage of apoptotic clusters (from 52 to 76%) in combination with more colony formation. The number of clusters and colonies showed a sharp decrease at day 10 because of persistently high apoptosis at cluster level and increasing apoptosis in colonies. BMMNC of AML patients showed a decreased proliferation with enhanced apoptosis at cluster level in contrast to a relatively low apoptotic levels in the colony-forming cells. This data show that increased proliferation is abrogated by enhanced apoptosis in MDS, whereas AML showed decreased proliferation with a low level of apoptosis in colony-forming cells. These growth profiles of BMMNC are independent of stromal influences and may represent intrinsic features of the MDS progenitors and accessory cell interactions.

Programmed cell death is an intrinsic feature of MDS progenitors, predominantly found in the cluster-forming cells

OBJECTIVE

Bone marrows (BM) of myelodysplastic syndrome (MDS) patients show increased proliferation and premature programmed cell death (PCD) in vivo as well as in vitro. We explored the proliferative capacity and apoptotic propensity of CD34+ progenitor cells of MDS patients excluding accessory cell interference.

MATERIALS AND METHODS

CD34+/CD3-/CD19- cells of 5 MDS patients and 5 normal BM were sorted as single cells into single wells and were cultured in liquid medium. Wells were evaluated on days 4, 7, 10, and 14. PCD was determined by staining with annexin V-FITC. Growth rate and cell doubling time (Td) were calculated for each colony-forming cell.

RESULTS

Normal BM CD34+ cells formed clusters and colonies and both showed increasing PCD in time, although within colonies the degree of apoptosis was twice as high (about 25%) as compared with clusters at all time points. In MDS increased cluster formation was observed at all evaluation points when compared to normal BM, whereas the number of colonies was markedly reduced (1/7 of normal). These colonies were also smaller, usually smaller than 100 cells. Significantly enhanced levels of PCD of clusters (53-79%) in combination with longer cell doubling times explain this slower formation of smaller colonies. Surprisingly, these colonies showed considerably lower levels of PCD (7-32%) as compared to normal (1-48%, median values).

CONCLUSIONS

In the absence of stromal influences and accessory cells, this study in MDS patients showed intrinsically enhanced proliferation and apoptosis of cluster-forming cells, as the opposite was true for colony-forming cells.

Role of physiologic concentrations of stem cell factor in leukemic type growth of myelodysplastic CD34+ cells

The stem cell factor (SCF: a ligand for c-kit) plays a central role in the growth of myelodysplastic (MDS) progenitor cells with leukemic type growth. In this study, the role of physiologic concentrations of SCF on the proliferation and differentiation on MDS progenitor cells was further analyzed in the presence of combined cytokines. For this purpose, marrow CD34+ cells were purified up to 94% for 12 normal individuals and 90% for 18 MDS patients, using monoclonal antibodies and immunomagnetic microspheres. The purified CD34+ cells were cultured for 14 days with saturating doses of cytokines, including recombinant human macrophage colony stimulating factor (rM-CSF), granulocyte-CSF (rG-CSF), granulocyte/macrophage-CSF (rGM-CSF), interleukin-3 (rIL-3) and rSCF. The clonal growth of MDS CD34+ cells supported by a combination of all the above cytokines was then subdivided into the two patterns of leukemic or non-leukemic. The role of various concentrations of rSCF (0, 0.5, 5, 50 and 500 ng ml(-1)), with or without the above cytokines, in proliferation and differentiation of MDS CD34+ cells was analyzed in each group. The physiologic concentration of SCF at 5 ng ml(-1) significantly increased undifferentiated 'blast cell' colonies or clusters in leukemic type growth of MDS CD34+ cells over that seen in normal CD34+ cells. SCF is present in plasma at a level of ng ml(-1). This means that progenitor cells are continuously exposed to stimulation by SCF in vivo and that MDS leukemic cells have a growth advantage over normal blasts.

Growth characteristics of myelodysplastic CD34+ cells

Myelodysplastic syndromes (MDS) are a heterogeneous group of disorders of hematopoiesis entailing hyperproliferative and ineffective hematopoiesis associated with morphologic evidence of marrow cell dysplasia resulting in refractory cytopenia(s), and an increased risk of transformation into acute myeloblastic leukemia (AML). The administration of colony-stimulating factor(s) (CSFs) to patients with MDS increased blood neutrophil concentrations, in most patients, and it was anticipated to be of benefit to prevent infections. The progression to AML while being treated with CSFs has come under close scrutiny. In vitro studies are expected to produce more pertinent criteria for selection of patients who are likely to benefit, as well as the overall benefits of various therapies. For this purpose, in vitro colony assays are an excellent approach for investigation of the biologic characteristics of MDS progenitor cells. The stem cell phenotype CD34 is the one of the best markers of progenitor cells, and can be used for the purification of these cells to unify levels of maturation; a direct comparison of proliferative and differentiative capacity of MDS progenitor cells with normal CD34+ cells can thus be made. The properties of MDS CD34+ cells are described here in association with proliferation and differentiation, with special emphasis on the role of stem cell factor (a ligand for c-kit) in leukemic type growth of MDS CD34+ cells.

Proliferation and differentiation of myelodysplastic CD34+ cells

Myelodysplastic syndromes (MDS) are a heterogeneous group of disorders of hematopoiesis involving hyperproliferative and ineffective hematopoiesis associated with morphologic evidence of marrow cell dysplasia resulting in refractory cytopenia(s), and an increased risk of transformation into acute myeloblastic leukemia (AML). The administration of colony-stimulating factor(s) (CSFs) to patients with MDS increased blood neutrophil concentrations, in most patients, and was also expected to be beneficial and to prevent infections. However, the progression to AML during the treatment with CSFs was suspected in some patients. Therefore, extensive in vitro studies were expected to lead to the establishment of criteria for selection of patients who are likely to benefit from CSF's as well as to establish the overall value of the different types of CSFs therapy. For this purpose, in vitro colony assays provide an excellent tool for investigating the biologic characteristics of MDS progenitor cells. However, conditions of the culture must be such that each progenitor can express its full potential for proliferation and differentiation. Because of the above, MDS progenitor cells cannot be used because they carry an impairment in proliferation and differentiation. To address this problem, one needs to know how many cells are being handled and the maximum numbers of colonies and clusters expected. CD34, a stem cell phenotype, is at present one of the best markers of progenitor cells, and can be used for purposes of purification. Using a defined number of CD34+ cells, it was feasible to make direct investigations on MDS progenitor cells. In this review the properties of MDS progenitor cells are described, in association with proliferation and differentiation, with special emphasis on the phenotypic subpopulations of MDS CD34+ cells.

Prognostic implications in myelodysplastic syndromes: A review of 62 cases

We retrospectively reviewed 62 MDS patients (15 RA, 3 RARS, 10 CMML, 20 RAEB, 14 RAEBT) to clarify the current problems in their management. Median survival of RA and RARS patients was 67.9 months and significantly longer than that of CMML, RAEB, or RAEB-T patients with median survivals of 16.1, 16.8, and 9.5 months, respectively. Karyotypic abnormalities were observed in 58% of the patients examined. Forty-two patients died, 16 (38%) of leukemic transformation and 21(50%) of bone marrow failure. While most of the RAEB-T patients of all ages and all the RAEB patients diagnosed below 60 years of age died of transformation, 70% of the older RAEB patients died of infection. Prognosis after transformation was poor and 12 patients died within two months. These results indicate that management after transformation and treatment against infection in RAEB patients with advanced age are crucial to improve the prognosis in MDS.

Prediction of 18-month survival in patients with primary myelodysplastic syndrome. A regression model and scoring system based on the combination of chromosome findings and the Bournemouth score

The predictive potential of six selected factors was assessed in 72 patients with primary myelodysplastic syndrome using univariate and multivariate logistic regression analysis of survival at 18 months. Factors were age (above median of 69 years), dysplastic features in the three myeloid bone marrow cell lineages, presence of chromosome defects, all metaphases abnormal, double or complex chromosome defects (C23), and a Bournemouth score of 2, 3, or 4 (B234). In the multivariate approach, B234 and C23 proved to be significantly associated with a reduction in the survival probability. The similarity of the regression coefficients associated with these two factors means that they have about the same weight. Consequently, the model was simplified by counting the number of factors (0, 1, or 2) present in each patient, thus generating a scoring system called the Lausanne-Bournemouth score (LB score). The LB score combines the well-recognized and easy-to-use Bournemouth score (B score) with the chromosome defect complexity, C23 constituting an additional indicator of patient outcome. The predicted risk of death within 18 months calculated from the model is as follows: 7.1% (confidence interval: 1.7-24.8) for patients with an LB score of 0, 60.1% (44.7-73.8) for an LB score of 1, and 96.8% (84.5-99.4) for an LB score of 2. The scoring system presented here has several interesting features. The LB score may improve the predictive value of the B score, as it is able to recognize two prognostic groups in the intermediate risk category of patients with B scores of 2 or 3. It has also the ability to identify two distinct prognostic subclasses among RAEB and possibly CMML patients. In addition to its above-described usefulness in the prognostic evaluation, the LB score may bring new insights into the understanding of evolution patterns in MDS. We used the combination of the B score and chromosome complexity to define four classes which may be considered four possible states of myelodysplasia and which describe two distinct evolutional pathways.

Proliferation and differentiation of myelodysplastic CD34+ cells in serum-free medium: II. Response to combined colony-stimulating factors

To investigate the role of colony stimulating factors (CSFs) in the proliferation and differentiation of progenitor cells from myelodysplastic syndromes (MDS), marrow progenitor cells from 18 MDS patients were highly purified using CD34 monoclonal antibody and immunomagnetic microspheres (MDS CD34+ cells). These cells were cultured in serum-free medium with various combinations of five colony stimulating factors (CSFs): recombinant human interleukin-3 (rIL-3), granulocyte/macrophage-CSF (rGM-CSF), granulocyte-CSF (rG-CSF), macrophage-CSF (rM-CSF), and erythropoietin (rEP). Among the tested CSFs, such as rM-CSF, rG-CSF, rGM-CSF and rIL-3, a combination of the first three CSFs was the most effective stimulus for the proliferation of non-erythroid MDS progenitor cells. An increase of undifferentiated "blast" cell colonies in 5/18 MDS patients occurred and these 5 patients belonged to the high-risk group. In the presence of these three CSFs, rIL-3 had no effect on the proliferation and differentiation of MDS CD34+ cells; however, IL-3 was efficient for the proliferation of MDS CD34+ cells to the erythroid lineage. rGM-CSF or rIL-3 alone did not efficiently support proliferation and differentiation of CD34+ cells. M-CSF is present in normal human serum at a concentration of 550 +/- 110 U/ml, a concentration exceeding that used in this study (100 U/ml). Therefore, in vivo administration of G-CSF combined with GM-CSF to MDS patients may be one of the most effective CSF combinations for proliferation of MDS progenitor cells to the non-erythroid lineage. However, the effect on the capacity for differentiation was minimal, especially in patients belonging to the high-risk group.

Allogeneic bone marrow transplantation in patients with myelodysplastic syndromes

Myelodysplastic syndromes (MDS) represent an acquired group of clonal disorders of the pleuripotent stem cells, resulting in progressive life-threatening cytopenias or transformation into acute leukemias. A major issue of using alloBMT in MDS is the criteria used for patient selection. Therapeutic trials of lesser intensity such as differentiating agents, and cytokines could be the preferable choice for patients with good prognostic features. On the other hand, patients with poor prognostic features may urgently need to establish a normal hematopoiesis through allogeneic bone marrow transplantation (alloBMT). Important prognostic indicators in MDS include FAB classification, presence of abnormal localization of immature precursors, degree of cytopenias and cytogenetic abnormalities. We used a novel preparative regimen--"BAC" consisting of the consecutive administration of 1 mg/kg of busulfan every 6 hours for 16 doses followed by 2 g/M2 of cytosine arabinoside (ara-C) given every 12 hours for four doses, and finally 60 mg/kg of cyclophosphamide daily for 2 days. Thirty two patients transplanted had a median age of 33 years. Nine of the patients had either RA or RARS, 21 had RAEB or RAEB-T and 2 were unclassified MDS. Twenty two of our patients had chromosomal abnormalities while 10 had a normal karyotype analysis. Nine of the 32 patients had documented leukemic transformation and received induction therapy prior to BMT. The median time from diagnosis to BMT was 5.6 months, ranging from 1.3 to 30.2 months. Nineteen out of 32 patients are alive without disease, with a median follow up of 24 months. The actuarial event-free survival for the entire group is 52%. Two patients have relapsed with an actuarial relapse rate of 12%. Only significant favorable prognostic indicator for the event-free survival was in the recipient of a genotypically matched graft (76%) compared to recipients of a non-genotypic graft (23%) (p = 0.02). "BAC" is a unique preparative regimen for alloBMT in MDS with excellent results.

Prognostic implications of bone marrow culturing in myelodysplastic syndrome: a retrospective analysis

To assess the predictive role of bone marrow culturing in MDS in vitro data of 205 patients were correlated with progression to AML and survival. Both in vitro growth pattern and in vitro differentiation were significantly predictive for progression to AML. Other predictive parameters were FAB classification and the presence of cytogenetic abnormalities in all metaphases analysed. Since FAB classification and in vitro bone marrow culturing appeared confounding variables, the in vitro data were analysed for high risk patients, RAEB and RAEBt and low risk patients, RA and RARS. In 91/110 RAEB(t) patients the estimated chance to develop AML was 25% in cases of normal growth versus 62% if abnormal (p < 0.06). In 82/87 RA(RS) patients the estimated chance to develop AML was 5% and 40% respectively (p = 0.0004). After AML progression median survival was only 2 months (0-16.1 months). In RAEB(t) patients bone marrow culturing did not discriminate for better survival, although a trend was shown. The estimated median survival was 16 months if growth was normal versus 8 months if abnormal (p = 0.07). In RA(RS) patients the median survival also was not significantly different, 31 versus 22 months respectively (p = 0.39). However, if in vitro growth and differentiation were both normal a significant difference in median survival was observed, 35 versus 22 months (p = 0.016). In conclusion, in vitro bone marrow culturing has predictive value for AML development in RA(RS) patients. In RAEB(t), due to many patients dying early in cytopenia, the predictive value is less pronounced. Especially normal growth in RA(RS) patients makes progression to AML very unlikely and these patients should be considered for a supportive approach. In RA(RS) patients with normal growth and differentiation (about 25% of all patients) in vitro bone marrow culturing also predicts a better survival.

Impaired proliferation and differentiation of myelodysplastic CD34+ cells

The myelodysplastic syndromes (MDS) are a heterogeneous group of disorders of hematopoiesis entailing hyperproliferative and ineffective hematopoiesis resulting in refractory cytopenia(s), and increased risk of transformation into acute myeloblastic leukemia (AML). The widely used classification defined by the French-American-British group (FAB) recognizes 5 cytological subtypes of different prognosis, based essentially on the presence and the frequency of marrow blasts. The percentage of marrow blasts does not exceed 30%, hence, direct investigations of biological and biochemical events of MDS blast cells have been hampered. The CD34 antigen is currently unique in its narrow specificity of expression on human lymphohematopoietic progenitor cells. This cell membrane phosphoglycoprotein has been used for immunologic blast cell purification, notwithstanding the frequency of marrow blasts, and has provided a set of tools for investigations of MDS i.e. a direct comparison of the nature of blast cells in each of the MDS subtypes, using immunologic, biologic, biochemical and molecular biological methodology. A combination of serum-free medium and a purification method for blast cells provided evidence that the progenitor cell growth abnormalities in these disorders involve a defect in the capacity of progenitor cells to respond to stimulation with growth factor(s), and has presented direct evidence for the manner in which myelodysplastic CD34+ cells are impaired.

New treatment approaches for myelodysplastic syndrome and secondary leukaemias

Allogeneic BMT is the treatment of choice for patients with MDS or sAML, offering a good chance of long-term disease-free survival if the transplant is performed in an early stage of disease or if the patient receives the transplant in complete remission after polychemotherapy. The transplant is limited to a minority of relatively young patients (aged below 55 years) with an HLA-identical sibling. Allogeneic BMT may also be considered when a closely- or fully-matched unrelated donor has been identified for a young and fit patient. All patients, including those without an excess of blasts, should be conditioned with bone marrow ablative therapy rather than an immune suppressive regime, such as cyclophosphamide alone. For the majority of patients there is no standard therapy other than appropriate supportive care. Relatively young patients below the age of 60 years with poor risk features can be considered for treatment with combination chemotherapy. Maintaining remission after remission-induction chemotherapy is a difficult issue. Patients not eligible for allogeneic BMT could be treated with post-remission chemotherapy or autologous BMT in the framework of prospective studies. Older patients can be considered for treatment with haematopoietic growth factors alone or in combination with differentiating agents such as low-dose Ara-C. This treatment should be delivered within the context of carefully designed and conducted trials.

Combination of mitoxantrone and etoposide in the treatment of myelodysplastic syndromes transformed into acute myeloid leukemia

Mitoxantrone and etoposide have both been shown to be effective in de novo acute myeloid leukemia. Therefore, the combination of mitoxantrone and etoposide, the NOVE regimen, was examined in the treatment of myelodysplastic syndromes (MDS) transformed into acute myeloid leukemia (AML). Twenty-one previously untreated patients (eight females, thirteen males) with a median age of 56 years (range 28-67 years) were studied. Diagnosis of MDS was made within the range of six months to three years before transformation into AML occurred. The NOVE regimen consisted of mitoxantrone 10 mg/m2 day 1-5, and of etoposide 100 mg/m2 day 1-5. After one single course of therapy eleven patients achieved a complete remission (CR) and three patients a partial remission (PR). Nine patients (six in CR and three in PR) received a second course, and the PR was completed to a CR in one patient. Thus, the overall response rate was 66% (14/21 patients), and the CR rate was 57% (12/21 patients). Median duration of CR was 7 months (range 2-10 months). Median survival was 10 months (range 3-20 months) for complete responders and 3 months (range 1-10 months) for patients who did not achieve a CR. For patients with subsequent CR, median time of granulocytopenia (< 500/microliters) and thrombocytopenia (< 20.000/microliters) was 20 days and 18 days, respectively. In conclusion, the NOVE regimen appears to be effective in AML secondary to MDS. However, strategies for remission maintenance are warranted.

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.

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.

In vitro growth of erythroid progenitor cells (BFU-E) and production of burst-promoting activity (BPA) by T lymphocytes in patients with myelodysplastic syndromes

The in vitro growth of circulating erythroid progenitors (BFU-E) populations and the production of burst-promoting activity (BPA) by T lymphocytes have been studied in 17 patients with myelodysplastic syndromes. Based on the in vitro growth patterns of BFU-E, four groups of patients have been identified: i) normal BFU-E growth; ii) low spontaneous BFU-E growth, but normal response to LCM; iii) impaired BFU-E response to LCM; iv) no BFU-E growth. The pattern of BFU-E growth seems to be related to the clinical stage of the disease rather than to the FAB subgroup to which the patients belong. The ability of T lymphocytes to stimulate BFU-E growth was significantly reduced in all patients. The possible mechanisms inducing the impaired production of BPA by T lymphocytes are discussed. The in vitro evaluation of circulating erythroid precursors can supply useful prognostic information and possibly indications concerning the responsiveness of erythropoietic stem cells to recombinant human erythropoietin in vivo.