Proliferative characteristics of Philadelphia-negative myeloproliferative neoplasms - clinical implications.

INTRODUCTION: Philadelphia-negative myeloproliferative neoplasms (Ph- MPN) are characterized by overproduction of one or more blood cell lines. METHODS: We studied the proliferative characteristics of 91 patients with de novo Ph- MPN. Colony-forming cells (CFC) and endogenous colonies (EC), from bone marrow (BM) and/or peripheral blood (PB), were analyzed by colony assay based on methylcellulose. The level of circulating CD34+ cells was determined by flow cytometry. RESULTS: The total number of PB CFC in primary myelofibrosis (PMF) was increased compared to the control sample (P < 0.01) and essential thrombocythemia (ET) (P < 0.05). The highest number of BM and PB EC was observed in polycythemia vera (PV) (P < 0.01). Increased levels of CD34+ cells characterized early-prefibrotic (57%) and advanced-fibrotic PMF (90%) as compared to PV (34%) and ET (32%) (P < 0.01). In the whole Ph- MPN group, the total number of PB CFC (P < 0.01), PB EC (P < 0.05), and CD34+ cells (P < 0.01) correlated with the degree of BM fibrosis. Higher levels of circulating CD34+ cells in PMF correlated with the total number of PB EC (P < 0.05) and degree of BM fibrosis (P < 0.01). CONCLUSIONS: Exploration of the PB proliferative characteristics of Ph- MPN on diagnosis may be helpful in revealing early-prefibrotic PMF. Monitoring the levels of circulating CD34+ cells may provide a sensitive indicator of fibrotic evolution in PV and PMF.

Pure red-cell aplasia as the presenting feature of the carcionoid tumor of the thymus: case report.

Acquired pure red-cell aplasia (PRCA) is an uncommon disorder of erythrocytopoiesis that can develop in association with thymic tumors. We present the very rare case of a severely anemic 62-year-old man with PRCA and a concurrent neuroendocrine carcinoid tumor of the thymus. The anterior mediastinal thymus tumor was completely excised, and following histological and immunohistochemical analyses (showing positive staining for cytokeratin, chromogranin A, synaptophysin, and neuron-specific enolase) the diagnosis of a (grade I; T(1)N(0)M(0)) typical carcinoid tumor of the thymus was made. Postoperatively the anemia persisted despite no signs of residual tumor on CT chest. A hematological work up found: normocellularity with <0.5% erythroblasts and preserved megakaryocytopoiesis and granulocytopoiesis in a trephine biopsy; reduced numbers of Colony Forming Unit Erythroid (CFU-E) and normal numbers of Burst-Forming Unit Erythroid (BFU-E) in bone marrow colony-forming assays; a markedly increased level of serum erythropoietin; normal T and B-cell numbers with a normal CD4/CD8 ratio; and no clonal T-cell receptor -gamma and -delta gene rearrangement) The patient responded favorably to a therapeutic trial of glucocorticoid immunosuppressive treatment (prednisone 1 mg/kg/day) with a normalization of the reticulocyte count and hematocrit, suggesting an immunologic mechanism for the PRCA. Though the exact mechanisms underlying the association between the PRCA and the carcinoid tumor of the thymus remain unknown.

In vitro sensitivity of hematopoietic progenitors to tiazofurin in refractory acute myeloid leukemia and in the blast crisis of chronic myeloid leukemia.

The effect of Tiazofurin (TR) on the in vitro growth of bone marrow (BM) and peripheral blood (PB) leukemic progenitors was investigated in 29 patients. Nineteen of the patients were suffering the blast crisis of chronic myeloid leukemia (bcCML) and ten patients refractory acute myeloid leukemia (AML). PB and BM mononuclear cells were cultured in methylcellulose alone or with concentrations of TR ranging between 10 and 200 microM. TR produced a dose dependent inhibition of colony forming unit (CFU)-blast growth in all the samples tested from BM and PB. The most effective concentrations of TR used were 150 and 200 microM, while concentrations of less than 50 microM TR were not adequate for 50% inhibition of cell growth (IC50). Differences were found in the response of CFU-blasts to TR related to the type of underlying leukemia. Inhibition of CFU-blast growth was more pronounced in bcCML than in AML in both the BM and PB samples. The concentration of TR required to induce IC50 in bcCML was 50 microM, while the same effect in AML required a concentration of 150 microM. Analysis of the control samples also revealed that CFU-blasts from bcCML produced smaller numbers of colonies, though these differences were not statistically significant. It has therefore been demonstrated that TR has strong in vitro anti-leukemic activity, more pronounced in bcCML than in refractory AML. We thus feel this study gives further rationale for the clinical application of TR, and would strongly support this.

Biological and clinical significance of clonogenic assays in patients with myelodysplastic syndromes.

Biological and clinical significance of growth pattern of hematopoietic progenitors were investigated in 117 patients with primary myelodysplastic syndromes (MDSs) at referral. Abnormal (i.e., "leukemic" or absent) growth of GM colonies (CFU-GM) and GM clusters was found in 47% of patients with "advanced" MDS (RAEB, RAEB-t, and CMML) and in 15% of "low-risk" (RA/RARS) patients. In vitro erythropoiesis was decreased in most of the patients, with significantly lower number of BFU-E in "advanced" MDS than in RA/RARS patients. Megakaryocyte progenitors (CFU-MK) were very low or absent in almost all the patients, regardless of the FAB type. Significant correlation was demonstrated between the number of BFU-E and hemoglobin concentration and between number of CFU-MK and platelet count. Growth capacity of GM progenitors appears to be in proportion to "myeloproliferative" capacity of the malignant clone. T-cell depletion had no influence on growth capacity of hematopoietic progenitors, nor did colony growth respond in a dose-dependent manner to different concentrations of LCM. Growth capacity of MDS hematopoietic progenitors was independent of Bournemouth score, of the presence and type of cytogenetic abnormality, and of the expression of CD95 and caspase-3 antigens on bone marrow cells. However, in patients with "abnormal" growth of GM progenitors, CD34 antigen expression was significantly higher than in patients with "normal" growth. "Abnormal" GM growth was found to be independently predictive regarding the survival and the risk for AML development. In contrast, the prognostic value of erythroid and megakaryocyte cultures was found to be limited.

Pure red cell aplasia evolving through the hyperfibrotic myelodysplastic syndrome to the acute myeloid leukemia: some pathogenetic aspects.

The authors report a 58-year-old female who originally presented with acquired pure red cell aplasia (PRCA). At diagnosis, the karyotype was normal, the serum erythropoietin level was highly elevated and no T-cell mediated inhibition of erythropoiesis was demonstrated in coculture studies. Conventional immunosuppressive therapy proved ineffective. A year later a diagnosis of hyperfibrotic myelodysplastic syndrome was assessed. The sequential bone marrow examinations in the course of the three years showed a progressive increase in bone marrow fibrosis, erythroid hyperplasia and dysmegakaryocytopoiesis, terminating in the acute myeloid leukemia. This sequence of the events included the appearance of del(5)(q13q33), four years after setting a diagnosis of PRCA. The authors suggest that the absence of both cytogenetic abnormality and the signs of dyshematopoiesis at the diagnosis of PRCA does not exclude ultimately a "clonal" category of the disease. Thus, repeated hematological and cytogenetical reevaluations are recommended.

Megakaryocyte progenitors in paroxysmal nocturnal haemoglobinuria are sensitive to complement.

We have investigated growth in vitro of bone marrow megakaryocytic progenitors (CFU-Mk) in 7 patients with paroxysmal nocturnal haemoglobinuria (PNH) to determine the sensitivity of CFU-Mk to complement. Bone marrow light density mononuclear cells were exposed to fresh or heat-inactivated AB human serum in the presence of medium or isotonic sucrose solution. We found that the proliferative activity of bone marrow CFU-Mk in PNH patients was significantly lower than in controls. In addition, the number of CFU-Mk in PNH bone marrow cells exposed to isotonic sucrose and complement was reduced to 25% of that in PNH cells exposed to isotonic sucrose without complement. In conclusion, our finding showed an increased sensitivity of CFU-Mk in PNH bone marrow cells to complement, supporting the hypothesis that the PNH defect is present at the level of CFU-Mk.

The inhibitory effect of human macrophage inflammatory protein-1 alpha (LD78) on acute myeloid leukemia cells in vitro.

Macrophage inflammatory protein-1 alpha (MIP-1 alpha) has recently been shown to inhibit proliferation of immature hemopoietic progenitors. In addition, significant inhibition of early and mature leukemic progenitors in acute myeloid leukemia (AML) has been obtained with MIP-1 alpha. We performed a study of 25 AML patients at diagnosis to evaluate the effect of a human homolog of MIP-1 alpha (LD78) on bone marrow (BM) and peripheral blood (PB) leukemic progenitors (colony-forming unit-AML [CFU-AML]) and AML cell proliferation. A methylcellulose culture system was used for CFU-AML and incorporation of 3H-TdR for AML cell proliferation. We found that LD78 inhibits CFU-AML colony formation up to 100% for the BM in 14/16 samples studied with the average maximal inhibition of 62.7 +/- 9.1% and up to 100% for the PB in 12/13 samples studied with the average maximal inhibition of 71.4 +/- 9.9%. In addition to this, LD78 inhibited AML cell proliferation up to 60% for the BM in 10/18 samples studied with the average maximal inhibition of 17.8 +/- 3.5%, and up to 87.1% for the PB cell proliferation in 10/16 samples studied with the average maximal inhibition of 27.5 +/- 6.8%. Our results have shown that LD78 is more active on AML progenitors than on AML cell proliferation. Inhibition of the AML cells, although less than that of the progenitors, indicates that more limited activity of LD78 on more mature leukemic cells is present in AML.

The determination of spontaneous megakaryocyte colony formation is an unequivocal test for discrimination between essential thrombocythaemia and reactive thrombocytosis.

Spontaneous colony formation from bone marrow megakaryocyte progenitors (BMsCFU-Mk) was studied in 24 patients with essential thrombocythaemia (ET), 20 patients with reactive thrombocytosis (RT), 20 patients with polycthaemia rubra vera with thrombocytosis (PRVtr), 16 patients with chronic myeloid leukaemia with thrombocytosis (CMLtr) and 18 normal control subjects (C). The culture medium which was used in the methylcellulose assay in vitro contained 30% of plasma from a single patient with hereditary haemochromatosis. Remarkable BMsCFU-Mk growth was recorded in all patients with ET but in none with RT or in C. BMs-CFU-Mk were present in 11/20 patients with PRVtr and 7/16 patients with CMLtr. Spontaneous bone marrow erythroid progenitors (BMsBFU-E) were also determined in these patients. BMsBFU-E were found in 21/24 patients with ET and none in the patients with RT and C. All patients with PRVtr and one patient with CMLtr showed BMsBFU-E. We conclude that our implementation of the in vitro methylcellulose assay allows the BMsCFU-Mk to be used as an unequivocal test for discrimination between ET and RT which has not been shown in previously published studies. In addition, we present evidence that in 10 patients BMsCFU-Mk and/or BMsBFU-E growth in the test persisted after long-lasting haematological remission.