Extended cytogenetic follow-up of patients with myelodysplastic syndrome (MDS)

The prognostic significance of clonal karyotype status in myelodysplastic syndrome (MDS) is assessed after an extended follow-up period of 5 years. There are three karyotype, single abnormalities or multiple abnormalities at the time of referral. However, there is no correlation between the size of the abnormal clone and prognosis. Karyotype status has independent prognostic significance in 'high risk' MDS so that patients with a refractory anaemia with excess of blasts (RAEB)/RAEB in transformation (RAEB-t) and a normal karyotype survive significantly longer than those with an abnormal karyotype (P < 0.001) and do not differ significantly from patients with refractory anaemia (RA). Significant differences in survival according to karyotype status are also seen in patients with chronic myelomonocytic leukaemia (P < 0.001) but not in those with primary acquired sideroblastic anaemia and RA. Among patients studied sequentially, those who retained a normal karyotype survived significantly longer than those who developed an abnormality on follow-up (P < 0.001). The risk of leukaemic transformation was also increased in patients who presented with or subsequently developed a clonal karyotype abnormality compared with those who remained normal (P < 0.05).

Cell-cycle progression rates and sister chromatid exchange frequencies in the bone marrow of patients with myelodysplastic syndrome and acute myeloid leukemia

The proliferation characteristics of leukemic cells may be a determining factor in disease course and response to therapy. The present study compares the rate of cell-cycle progression in the bone marrow of 16 hematologically normal subjects, 19 patients with acute myeloid leukemia (AML), and 23 patients with myelodysplastic syndrome (MDS). The frequency of sister chromatid exchanges (SCE) in bone marrow cells is also compared. MDS and AML patients showed a reduction in the rate of cell-cycle progression compared with normal subjects. Patients with 'high risk' MDS (RAEB/RAEB-t) did not differ significantly from patients with AML but had a significantly slower rate of cell-cycle progression than patients with 'low-risk' MDS (PASA/RA). There was no correlation between the rate of cell-cycle progression and clonal karyotype status or the percentage of blast cells in either MDS or AML. There were no significant differences in SCE frequency between normal subjects and MDS or AML patients.

Desferrithiocin is an effective iron chelator in vivo and in vitro but ferrithiocin is toxic

The efficacy and toxicity of the siderophore desferrithiocin (DFT), which has shown potential application in iron chelation therapy, were assessed in vivo and in vitro. DFT was evaluated in vivo in two ways: firstly, by measuring the effect of a single dose of DFT (10-100 mg/kg) on 59Fe excretion in iron-loaded rats labelled with 59Fe; and secondly, by examining the effect of the daily oral administration for 2 weeks of DFT (10-25 mg/kg/d) on the growing rat. DFT and its ferric complex, ferrithiocin (FT), were assessed in vitro from their effects on transferrin and iron uptake and mobilization from rat hepatocytes in culture using transferrin doubly labelled with 125I and 59Fe. Both oral and subcutaneous DFT were highly effective in promoting iron excretion in vivo, but showed evidence of toxicity after oral administration for 2 weeks at 25 mg/kg/d. In addition, DFT was much more effective than desferrioxamine or pyridoxal isonicotinyl hydrazone in reducing hepatocyte iron in vitro. However, FT was cytotoxic, causing membrane disruption and release of intracellular aspartate aminotransferase. It was concluded that DFT should not be considered for chronic iron chelation therapy without extensive further evaluation.

Chromosome aberrations following cytotoxic therapy in patients in complete remission from lymphoma

The frequency of chromosome aberrations in the peripheral blood of patients successfully treated for Hodgkin's disease (HD) and non-Hodgkin's lymphoma is compared with that seen in age-matched haematologically normal subjects. Findings are considered in relation to risk factors associated with the development of secondary myelodysplastic syndrome (MDS) or acute myeloid leukaemia (AML). Overall aberration frequencies were not significantly increased in patients compared with normal subjects. However, there were differences in aberration type. The frequency of exchanges was significantly higher among patients (P less than 0.01) and the frequency of gaps lower (P less than 0.0005). The mean frequency of exchanges was also greater in patients receiving multiple compared to single courses of therapy (P less than 0.0005) and in patients receiving radiotherapy or combined modality therapy compared to chemotherapy alone (P less than 0.005 and P less than 0.0005). Four patients had aberration frequencies greater than 2 SD above the patient mean. One of these was also found to have a mutation of the ras oncogene. None of the patients has yet developed secondary MDS/AML.

Replacing 99Tcm-DMSA for renal imaging?

We have tried to evaluate the usefulness of an early 99Tcm-MAG3 image, obtained during the second minute after injection of the tracer, in predicting the renal alterations seen on a 99Tcm-DMSA scintigraph, in children clinically suspected of pyelonephritis. It appears that the accuracy of the MAG3 image is population dependent: when, in most of the patients of a study group, DMSA scintigraphy is either normal or very abnormal, the MAG3 image will correctly reflect the DMSA scintigraph. However, when the DMSA alterations are less pronounced, the early MAG3 image will miss the lesions in about 50% of the cases.

Clonal lymphocytes are detectable in only some cases of MDS

Clonal analysis of lymphocytes from patients with myelodysplastic syndrome (MDS) has been carried out using X-chromosome inactivation patterns detected by the probe M27 beta, and by polymerase chain reaction amplification of the immunoglobulin heavy chain gene hypervariable region, CDR3. Of 32 female patients heterozygous for M27 beta only seven (22%) demonstrate monoclonality of peripheral blood lymphocytes. 12 (37%) give unequivocal polyclonal results and the remaining cases give patterns of X-inactivation which cannot be interpreted either way. A study of 68 MDS patients showed five (7%) with a population of B-cells with a monoclonal rearrangement of CDR3 compared with none out of 60 normal individuals, none out of 15 with B-non Hodgkin lymphoma (B-NHL) in remission and 19 out of 25 (75%) of cases of B-chronic lymphocytic leukaemia (B-CLL). Monoclonal lymphocytes were found by both techniques in only two females with MDS. We conclude that the presence of polyclonal lymphocytes is a common finding in patients with MDS.

Intraoperative radioactive localization of small bone tumours

A sodium-iodide scintillation probe and a portable scaler rate-metre were used to localize small bone tumours at operation, after the preoperative injection of technetium-99m methylene diphosphonate. This technique allows complete removal of the tumour nidus of an osteoid osteoma or the active part of other lesions without undue sacrifice of the surrounding bone. The method has been used for successful relief of pain in thirteen patients.

Peripheral blood chromosome aberrations in MDS

The frequency of non-clonal structural and numerical chromosome aberrations in peripheral blood lymphocytes of 51 patients with MDS and 37 age-matched hematologically normal subjects is assessed. The frequency of aneuploid cells (p less than 0.001) and of structural aberrations (p less than 0.005) was significantly higher in MDS patients than in normal subjects, but showed no relationship with FAB type or with the presence of clonal karyotype abnormalities in the bone marrow. Exchange configurations were only observed in MDS patients (27.5%). The data also suggest that there may be an association between high peripheral blood aberration levels and rapidly progressive disease. This may indicate increased mutagen sensitivity and have implications for treatment.

A randomized phase-I/II multicenter study of recombinant human granulocyte-macrophage colony-stimulating factor (GM-CSF) therapy for patients with myelodysplastic syndromes and a relatively low risk of acute leukemia. EORTC Leukemia Cooperative Group

To assess the effects of GM-CSF in patients with myelodysplasia, a total of 101 patients with refractory anemia (RA), RA with ringed sideroblasts (RARS), and RA with an excess of blasts provided that the percentage of blasts in the bone marrow did not exceed 10% (RAEB) were enrolled in the EORTC Leukemia Cooperative Group study 06885. They were randomized to receive two daily subcutaneous injections of rhGM-CSF (mammalian, glycosylated, Sandoz/Schering-Plough) at a daily dose of either 108 micrograms glycoprotein (group I) or 216 micrograms glycoprotein (group II) for 8 weeks. Response was defined as an increase in Hb (greater than 2.5 g%), neutrophil count (more than 100%), or platelet count (more than 100%) without progression of the disease. After exclusion of 19 patients who did not meet the entry criteria, 82 were evaluated. Fifty-four patients (66%) responded (27 of 42 patients in group I and 27 of 40 in group II). Progressive disease was seen in two patients of group I and in four of group II. Two of the latter developed leukemia. All responses were reflected in the granulocytic series. In two patients platelet numbers also increased. Cytogenetic analysis, successfully performed in 43 cases, showed that 14 of 16 patients with normal karyotypes responded, compared with 14 of 27 patients with abnormal karyotypes (p = 0.008). In some cases GM-CSF was reduced in dose or discontinued prematurely due to side effects so that only 35% of all evaluable patients finished 8 weeks of treatment without a change of dose.

Treatment of myelodysplastic syndromes (MDS) and high leukaemic risk with low-dose cytosine arabinoside (LD-AraC) plus granulocyte-macrophage colony-stimulating factor (rh GM-CSF). The EORTC Leukaemia Group

Symptomatic patients with myelodysplastic syndromes (MDS) and 10-30% blasts in the bone marrow were treated with low-dose AraC (2 x 10 mg/m2 subcutaneously (sc) days 1-14) and GM-CSF (fully glycosylated, Sandoz/Schering-Plough, 2 x 150 micrograms protein/day sc) given either subsequently (days 15-21) or simultaneously (days 8-14 and one week rest). Evaluations were carried out after three courses (nine weeks); responding patients could be continued for two further cycles. Eighty-two patients with refractory anaemia and excess of blasts (RAEB), with (RAEBt) or without transformation, were evaluable: 45 RAEB and 37 RAEBt, mean age 64 years (range 17-80 years). A complete remission was achieved in 14 cases (17%), 11 had a good response (13%), and 12 a partial response (15%). Stable disease was found in 21 cases (26%). There were 12 cases of toxic death (15%), progression was noted in eight patients (10%), and death due to disease in three (4%). No difference existed between the two treatment arms with respect to response. Major adverse events during treatment were haemorrhage (25%), infections (23%), and fever with GM-CSF (21%). GM-CSF did not induce leukaemia nor contribute to haemorrhage induced by AraC, but gave rise to an overall response rate of 46% which is high and relatively durable as compared to other treatments in this disease.

Gene mutations in myelodysplasia

The myelodysplastic syndrome is a paradigm of human preleukaemia. Normal haemopoiesis is progressively displaced by an abnormal clone derived from a mutated stem cell. The initial mutation is unknown but its occurrence may be related to the overall load of random mutations which are a consequence of both intrinsic DNA defects and external mutagens. Evolution of the pathological population is marked by an increasing load of genetic lesions at the molecular and cytogenetic levels. Ras mutations can be detected in the blood of about 50% of MDS patients. Fms mutations are less common but these lesions can be found both in patients and in haematologically normal subjects who have previously received cytotoxic therapy suggesting that they can occur early in the preleukaemic process. Clonal haemopoiesis in the absence of either ras or fms mutations can occur in these subjects. The data suggest the inability of mutant ras or fms genes alone to produce observable preleukaemic changes but that subjects with these mutations may be predisposed to future MDS. Ras mutations are a common accompaniment of a wide variety of malignancies and experimental transfection of the mutant gene can induce a malignant phenotype in cultured cells. There are many possible mechanisms for this transformation which may be relevant in a clinical context. Experimentally observed effects include a direct influence on the cell cycle, the induction of drug resistance and the stimulation of autocrine growth factor production. It may eventually be possible to define which gene mutations are important in conferring a malignant state, which determine phenotype and which are of incidental significance.

Isochromosome (6p) in Waldenstrom's macroglobulinemia

Cytogenetic data on two cases of previously treated Waldenstrom's macroglobulinemia (WM) are presented. An i(6p) was identified in 60 and 56% of bone marrow (BM) metaphases from each patient, respectively. In both cases, i(6p) occurred as part of a complex karyotype but was also observed as the sole abnormality in a proportion of metaphases. The literature on the cytogenetics of WM and the relevance of i(6p) is discussed.

Transcriptional interference in transgenic plants

When a promoterless marker gene is transformed into the plant genome using the Agrobacterium vector system, on average 30% of the T-DNA inserts produce gene fusions. This suggests that the T-DNA is preferentially integrated into transcribed regions. Here, we proposed that this transcriptional activity is responsible for some of the variation in expression frequently observed among independent transformants. Using hybrid gene constructions, we show that transcriptional readthrough into a downstream gene with opposite orientation substantially reduces expression of this gene both in transient expression and in transgenic plants. Furthermore, a poly(A) signal/terminator can block readthrough and restore the expression of the gene. Finally, enzymatic analysis of calli suggests that less variation in neomycin phosphotransferase II synthesis is observed when the gene is separated from plant DNA by promoter and terminator elements.

Increased drug accumulation ex vivo with cyclosporin in chronic lymphatic leukemia and its relationship to epitope masking of P-glycoprotein

The ability of cyclosporin to modify drug accumulation in vitro, measured by the cellular accumulation of daunorubicin, was examined. In 42 patients with chronic lymphatic leukaemia this correlates well with the levels of P-glycoprotein (Pgp) measured by immunofluorescent labelling of Pgp after treatment of the cells with neuraminidase to unmask the epitope recognized by the monoclonal antibody MRK 16. It is shown that flow cytometric analysis using MRK 16 to detect Pgp expression levels together with drug accumulation studies can rapidly assess the multidrug-resistant phenotype of patients' cells, and enable selection of those suitable for therapy with agents known to circumvent mdr-1 mediated drug resistance.

Heterotropic interactions in aspartate transcarbamoylase: turning allosteric ATP activation into inhibition as a consequence of a single tyrosine to phenylalanine mutation

Aspartate transcarbamoylase (EC 2.1.3.2) is extensively studied as a model for cooperativity and allostery. This enzyme shows cooperativity between the catalytic sites, and its activity is feedback inhibited by CTP and activated by ATP. These regulatory processes involve several interfaces between catalytic and regulatory chains as well as between domains within these two types of chains. As far as the regulatory chain is concerned, its two domains are in contact through a hydrophobic interface, in which a tyrosine residue is inserted in a pocket involving two leucine residues of the allosteric domain and a valine and a leucine residue of the zinc domain. To probe the possible implication of this hydrophobic core in the CTP and ATP regulatory effect, the tyrosine was replaced by a phenylalanine through oligonucleotide-directed mutagenesis. Interestingly, the resulting mutant shows a complete inversion of the ATP effect; it is now inhibited by ATP instead of being activated by this nucleotide triphosphate. This mutant remains normally sensitive to the feedback inhibitor CTP. This result shows that the hydrophobic interface between the two domains of the regulatory chain plays an important role in the discrimination between the regulatory signals promoted by the two allosteric effectors.

The clearance of a single i.v. bolus of recombinant human erythropoietin from the serum of patients with myelodysplastic syndromes and its effects on erythropoiesis

The serum erythropoietin (EPO) concentration in patients with myelodysplasia (MDS) varies widely at similar hemoglobin concentrations, although the reasons for this variation are unclear. We have studied the pharmacokinetics of an i.v. bolus of recombinant human EPO in ten subjects with myelodysplasia. Basal serum EPO concentration varied from 210 to 5984 mU/ml. Plasma half-time clearance (t1/2) varied from 3.9 to 20.0 h. A significant positive correlation was found between t1/2 and basal EPO concentration. An increase in immature peripheral blood reticulocytes was found on days 1 and 2 after EPO treatment; this may represent either an effect on hemopoiesis or on reticulocyte release from the bone marrow.

Growth response to cytokines of circulating myeloid progenitors from myelodysplastic patients at diagnosis and more than 600 days after diagnosis

Myeloid colony growth from the peripheral blood of myelodysplastic (MDS) patients was assessed for abnormal in vitro response to haemopoietic growth factors (granulocyte colony-stimulating factor (G-CSF), macrophage colony-stimulating factor (M-CSF), granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin-1 (IL-1), interleukin-3 (IL-3)). Abnormal colony growth, increased or reduced, was observed with each of the factors. No specific growth pattern was related to any of the French-American-British classification (FAB) types of disease. MDS patients who had survived greater than 600 days after diagnosis (n = 34) showed significantly fewer abnormalities than patients assayed at the time of diagnosis (n = 37), the major difference being less frequent stimulation of colony growth. These findings indicate that the time of sampling relative to diagnosis needs to be considered when interpreting the in vitro response to growth factors of myeloid colonies from MDS patients.

Detection of two-component mixtures of lognormal distributions in grouped, doubly truncated data: analysis of red blood cell volume distributions

We have examined the statistical requirements for the detection of mixtures of two lognormal distributions in doubly truncated data when the sample size is large. The expectation-maximization algorithm was used for parameter estimation. A bootstrap approach was used to test for a mixture of distributions using the likelihood ratio statistic. Analysis of computer simulated mixtures showed that as the ratio of the difference between the means to the minimum standard deviation increases, the power for detection also increases and the accuracy of parameter estimates improves. These procedures were used to examine the distribution of red blood cell volume in blood samples. Each distribution was doubly truncated to eliminate artifactual frequency counts and tested for best fit to a single lognormal distribution or a mixture of two lognormal distributions. A single population was found in samples obtained from 60 healthy individuals. Two subpopulations of cells were detected in 25 of 27 mixtures of blood prepared in vitro. Analyses of mixtures of blood from 40 patients treated for iron-deficiency anemia showed that subpopulations could be detected in all by 6 weeks after onset of treatment. To determine if two-component mixtures could be detected, distributions were examined from untransfused patients with refractory anemia. In two patients with inherited sideroblastic anemia a mixture of microcytic and normocytic cells was found, while in the third patient a single population of microcytic cells was identified. In two family members previously identified as carriers of inherited sideroblastic anemia, mixtures of microcytic and normocytic subpopulations were found. Twenty-five patients with acquired myelodysplastic anemia were examined. A good fit to a mixture of subpopulations containing abnormal microcytic or macrocytic cells was found in two. We have demonstrated that with large sample sizes, mixtures of distributions can be detected even when distributions appear to be unimodal. These statistical techniques provide a means to characterize and quantify alterations in erythrocyte subpopulations in anemia but could also be applied to any set of grouped, doubly truncated data to test for the presence of a mixture of two lognormal distributions.