Comparison of oral iron chelator L1 and desferrioxamine in iron-loaded patients

The efficacy of the oral iron chelator 1,2-dimethyl-3-hydroxypyrid-4-one (L1) was compared with that of subcutaneous desferrioxamine in 26 patients with transfusional iron overload. Immediately after red-cell transfusion, 20 patients were randomised to receive either desferrioxamine (50 mg/kg daily as a 12 h subcutaneous infusion), or L1 (50 mg/kg daily by mouth). Patients were evaluated during treatment with the other drug after transfusion the next month. Mean (SD) daily urinary iron excretion was lower during L1 than during desferrioxamine (12.3 [6.7] vs 18.2 [15.3] mg/day). In 5 patients the dose of L1 was raised from 50 to 75 mg/kg daily; mean urinary iron excretion rose from 13.8 (7.0) mg/day to 26.7 (17.8) mg/day, comparable with that during desferrioxamine (24.9 [24.3] mg/day). Faecal iron excretion rose slightly over baseline in 6 patients studied during L1 administration (from 8.5 [0.9] mg/day to 12.2 [0.9] mg/day). Pharmacokinetic studies showed an elimination half-life for L1 of 117-237 min. Studies in dogs and in volunteers showed no absorption of the L1-iron complex, excluding a contribution of absorption of intraluminal complexes of L1 and food iron to urinary iron excretion. Further animal toxicity testing is needed before L1 can be studied in a broader group of patients.

Effect of age at the start of iron chelation therapy on gonadal function in beta-thalassemia major

BACKGROUND

Patients with transfusion-dependent thalassemia major tend to have abnormal growth and sexual maturation at puberty, presumably as a result of pituitary iron overload. This study was designed to determine whether chelation therapy with deferoxamine before the age of puberty would ameliorate this problem.

METHODS

We examined 40 patients over 14 years of age with transfusion-dependent thalassemia major. The 19 patients in group A (mean [+/- SD] age at study, 17.0 +/- 1.5 years) had begun nightly treatment with subcutaneous deferoxamine before the age of 10 (mean age at start of treatment, 7.5 +/- 1.8 years). The 21 patients in group B (mean age, 24.1 +/- 3.8 years) had begun treatment after the age of 10 (mean age at start of treatment, 14.4 +/- 4.7 years).

RESULTS

The abnormal findings were essentially confined to sexual development. The final height did not differ between groups or from the mean parental height in each group. Ninety percent of the patients in group A had normal sexual development, as compared with 38 percent of those in group B (P = 0.001). Outcomes were correlated with indexes of iron overload; the patients in group A had lower serum ferritin levels before chelation treatment (P = 0.01) and lower average serum ferritin levels during treatment (P = 0.005).

CONCLUSIONS

Beginning chelation treatment with deferoxamine before the age of puberty can help children with transfusion-dependent thalassemia major to attain normal sexual maturation.

The expression of c-fos, c-jun, and c-myc genes is regulated by heat shock in human lymphoid cells

The effect of heat shock on the expression of the nuclear protooncogenes c-fos, c-jun, and c-myc was studied in human lymphoid cells. Heat shock caused an increase in c-fos and c-jun mRNA levels and a decrease in c-myc mRNA levels in pre-B (Hyon) and T (DND-41) cell lines as well as in freshly isolated normal human thymocytes. The changes in the mRNA levels of these protooncogenes in Hyon cells were most pronounced at 42 and 43 degrees C; kinetic analysis demonstrated that the changes could be detected within 30 min of heat shock. Altered transcription of c-fos and c-myc genes was the primary effect of heat shock. Secondarily, heat shock of Hyon cells stabilized the c-myc mRNA level by increasing its half-life from 24 to 45 min. The overall effect of heat shock on c-myc mRNA level, however, was a marked inhibition of its transcription. These results demonstrate that the transcription of nuclear protooncogenes is regulated by heat shock indicating a role for nuclear protooncogenes in the stress response of lymphoid cells.

The expression of c-fos, c-jun, and c-myc genes is regulated by heat shock in human lymphoid cells

The effect of heat shock on the expression of the nuclear protooncogenes c-fos, c-jun, and c-myc was studied in human lymphoid cells. Heat shock caused an increase in c-fos and c-jun mRNA levels and a decrease in c-myc mRNA levels in pre-B (Hyon) and T (DND-41) cell lines as well as in freshly isolated normal human thymocytes. The changes in the mRNA levels of these protooncogenes in Hyon cells were most pronounced at 42 and 43 degrees C; kinetic analysis demonstrated that the changes could be detected within 30 min of heat shock. Altered transcription of c-fos and c-myc genes was the primary effect of heat shock. Secondarily, heat shock of Hyon cells stabilized the c-myc mRNA level by increasing its half-life from 24 to 45 min. The overall effect of heat shock on c-myc mRNA level, however, was a marked inhibition of its transcription. These results demonstrate that the transcription of nuclear protooncogenes is regulated by heat shock indicating a role for nuclear protooncogenes in the stress response of lymphoid cells.

Pulmonary syndrome in patients with thalassemia major receiving intravenous deferoxamine infusions

Eight patients with transfusion-dependent thalassemia major were given continuous intravenous infusions of the chelator, deferoxamine mesylate, to reduce iron overload. Within 5 to 9 days of starting the infusions, four patients developed a pulmonary syndrome of moderate to life-threatening severity characterized by tachypnea, hypoxemia, and a diffuse interstitial pattern on chest roentgenogram. Pulmonary function studies showed restrictive dysfunction. Lung biopsy showed diffuse abnormalities with alveolar damage, interstitial fibrosis, and inflammation. The inflammatory infiltrate comprised lymphocytes, eosinophils, and mast cells. Exposure of the biopsy specimen to fluorescein-conjugated anti-IgE antibody showed fixation of IgE to the mast cell surface, suggesting a hypersensitivity reaction. Detailed studies failed to identify an infectious agent. The temporal relationship between drug administration and lung disease, and the clinical similarities in the four affected patients, strongly suggested a cause and effect relationship. We recommend that therapy with continuous intravenous infusions of deferoxamine be monitored carefully with respect to pulmonary status.

Comparison of deferoxamine pharmacokinetics between asymptomatic thalassemic children and those exhibiting severe neurotoxicity

The use of deferoxamine for iron chelation in transfusion-dependent thalassemia major is limited by serious neurotoxicity (hearing and vision loss). We assessed whether interpatient variability in handling deferoxamine and resultant accumulation of the drug may account for the neurotoxicity. We studied steady-state deferoxamine pharmacokinetics during intravenous infusion in two groups of patients--one group exhibited severe manifestations of auditory and visual loss and one group was asymptomatic. The groups were matched for age, sex distribution, weight, treatment period, ferritin levels, and hemoglobin levels. Similarly, doses of deferoxamine at the time of the study were not different. Clearance rates were not different between the symptomatic and asymptomatic patients (39.83 +/- 4.54 versus 30.66 +/- 4.39 ml/min.kg). However, patients who exhibited toxicity received significantly higher daily doses of subcutaneous deferoxamine at the time of diagnosis of neurotoxicity (9.03 +/- 0.96 and 5.58 +/- 0.61 mg/kg.hr, respectively; p less than 0.005). These data suggest that deferoxamine induced neurotoxicity is dose-dependent and cannot be attributed to accumulation of the drug caused by slower clearance rates.

Expression of glycolipid receptors to Shiga-like toxin on human B lymphocytes: a mechanism for the failure of long-lived antibody response to dysenteric disease

Fresh and transformed human B lineage cells were found to be sensitive to the cytotoxic action of Shiga-like toxin (SLT), a bacterial cytotoxin. The toxin was specifically bound by the glycolipids globotriosylceramide and galabiosylceramide expressed on the surface of sensitive cells. Mutant Daudi cells selected for resistance to SLT cytotoxicity (SLTR20) were deficient in SLT-binding glycolipids and failed to bind SLT to their surface, suggesting a role for these glycolipids in the mediation of SLT cytotoxicity. Of a number of normal and transformed lymphoid and myeloid cells screened for SLT sensitivity, only B lymphoid cells were susceptible to SLT action. Moreover, B lymphoid cells were the only cells expressing the SLT binding glycolipids. In vitro B cell activation studies with Epstein-Barr virus and pokeweed mitogen both indicated that the vast majority of SLT-sensitive B cells belong to the IgG and IgA committed subset, whereas most IgM and IgM/D producing cells were resistant to SLT toxicity. The selective elimination of IgG and IgA committed cells may explain the production of only IgM class anti-SLT antibodies in Shigella-infected humans leading to the failure of long-term immunity to dysenteric disease.

Juvenile chronic myelogenous leukemia: differentiation from infantile cytomegalovirus infection

Differentiation between cytomegalovirus (CMV)-associated disease and juvenile chronic myelogenous leukemia (JCML) in infants excreting CMV may be difficult. It is important to make a prompt, definitive diagnosis since the management differs. A 3-month-old infant presented with clinical findings that mimicked both disorders and a plan was developed to make the correct diagnosis. Clonogenic assays and liquid cultures of patients' peripheral blood and bone marrow showed findings that are recognized as the hallmark of JCML, namely, impaired growth of normal hematopoietic progenitors, and excessive, autonomous proliferation of monocyte/macrophage elements. The urine was positive for CMV, and there was a significant rise in the anti-CMV antibody titer over 4 weeks, indicating a postnatal CMV infection. Despite this, freshly obtained and cultured marrow cells as well as a liver biopsy were negative for CMV by immunoassay, by anti-CMV monoclonal antibody testing, and by electron microscopy. Because of these results, the diagnosis of CMV infection was established but could not account for all of the abnormal clinical and hematological findings. Thus, the diagnosis of JCML was also substantiated and antileukemic therapy was initiated with confidence.

A model of human acute lymphoblastic leukemia in immune-deficient SCID mice

A human acute lymphoblastic leukemia (ALL) cell line that was transplanted into immune-deficient SCID mice proliferated in the hematopoietic tissues, invaded various organs, and led to the death of the mice. The distribution of leukemic cells in SCID mice was similar to the course of the disease in children. A-1 cells marked with a retrovirus vector showed clonal evolution after the transplant. SCID mice that were injected with bone marrow from three patients with non-T ALL had leukemic cells in their bone marrow and spleen. This in vivo model of human leukemia is an approach to understanding leukemic growth and progression and is a novel system for testing new treatment strategies.

Acute changes in renal function associated with deferoxamine therapy

In three patients who received intravenous deferoxamine there was a twofold to eightfold increase in plasma creatinine level and a parallel decrease in creatinine clearance that resolved when treatment with the drug was discontinued. In two thalassemic patients, diuresis was evident by urine output exceeding fluid intake. The mechanism was studied in dogs that exhibited an acute and significant decrease in inulin and para-aminohippuric acid clearances induced by intravenous deferoxamine. Saline diuresis could prevent the decrease in the glomerular filtration rate but not the decrease in renal blood flow caused by deferoxamine. Deferoxamine induced an acute increase in the fractional excretion of sodium, potassium, chloride, phosphate, and urate, which may explain the relative diuresis observed in two of the patients. In a subsequent experiment, ferrioxamine induced an increase in the fractional excretion of sodium and chloride but did not affect the glomerular filtration rate and renal blood flow. Our studies suggest that adequate hydration may be needed to preserve renal hemodynamics during intravenous deferoxamine therapy. Repeated measurements of renal function should accompany treatment with this agent.

Diamond-Blackfan anemia: promotion of marrow erythropoiesis in vitro by recombinant interleukin-3

To clarify the defective erythropoiesis in eight patients with Diamond-Blackfan anemia, we studied their bone marrow response in vitro to recombinant human interleukin-3 (IL-3) and recombinant granulocyte-macrophage colony-stimulating factor (GM-CSF). In an erythropoietin-containing assay system, specimens from six of the eight patients yielded low numbers of erythroid colonies compared to control values, and in five of these no erythropoietin dose-response could be elicited. Addition of IL-3, GM-CSF or both to cultures from the six patients had no effect on CFU-E-derived colonies. In contrast, IL-3 but not GM-CSF induced a marked increase in the number (183%) and size of the BFU-E-derived colonies in five of the six cases and partially corrected the impaired dose-response to erythropoietin in four. Bone marrow from the other two patients yielded numbers of CFU-E and BFU-E colonies comparable to controls and manifested similar increments in colonies with increasing concentrations of erythropoietin. When IL-3 was added to these cultures, further increments were observed in the number and size of BFU-E colonies. We conclude that IL-3 enhanced the marrow erythropoiesis in most of the patients and exerted a corrective effect on the aberrant colony formation in the presence of erythropoietin. The data raise the possibility of IL-3 as a therapeutic agent in Diamond-Blackfan anemia.

A variant form of Bernard-Soulier syndrome: mild haemostatic defect associated with partial platelet GPIb deficiency

Platelets from patients with Bernard-Soulier syndrome (BSS) are larger than normal and demonstrate characteristic aggregation abnormalities. A molecular defect involving platelet membrane glycoproteins has been established as the primary abnormality, and the major defect is described as an absence of GPIb, the receptor for von Willebrand factor, which prevents the adhesion of BSS platelets to damaged endothelium. Associated deficiencies of GPV and GPIX are also recognized. The overall clinical effect is a haemorrhagic tendency which, although variable, is severe at times in all patients. We report a child who presented with the typical morphological and aggregation abnormalities associated with BSS, but who had negligible bleeding problems. Further investigation revealed a significant but incomplete deficiency of GPIb and of GPV and GPIX. This case suggests that BSS may be a heterogeneous disorder with clinical consequences dependent on the extent and complexity of the platelet membrane glycoprotein deficiency.

Growth requirements for human acute lymphoblastic leukemia cells: refinement of a clonogenic assay

Since freshly obtained acute lymphoblastic leukemia (ALL) cells rarely replicate spontaneously in vitro in a sustained way, development of a useful clonogenic assay for ALL blast progenitors is dependent on identifying the cellular growth requirements. Thus, marrows from 25 ALL cases were cultured in methylcellulose to determine the optimal conditions for cell growth. Blast colonies were confirmed as leukemic by morphology, cytochemistry, surface markers, and cytogenetics. Irradiated (7000 rads) normal peripheral blood feeder cells were an absolute requirement and produced number-dependent increases in ALL colonies; added growth factors enhanced the feeder cell effect. ALL cell-feeder cell contact was essential since their physical separation in a two-layer culture system drastically interfered with colony growth. Feeder cells from various donors, including new and relapsed cases of ALL, yielded colony numbers that differed widely when tested on the same marrow with and without added growth factor; thus, identification of a "good" feeder cell donor was key to an optimal assay. Neither recombinant interleukin-2 nor recombinant GM-CSF had ALL growth-promoting properties when tested alone or in combination but in the presence of feeder cells they moderately enhanced the feeder cell effect. The most effective growth factors were derived from cells exposed to phytohemagglutinin (PHA) for 72 h. In order of magnitude for colony growth-promoting activity, PHA-T cell conditioned medium (CM) was more stimulatory than PHA-blast cell CM followed by PHA-leukocyte CM; removal of PHA from CM by affinity chromotography did not alter the results. The most potent PHA-TCM was prepared from T-cells from a phlebotomized hemochromatosis patient; PHA-TCM from transfused thalassemia patients and normal donors were less active. Concanavalin-A blast cell CM had modest colony promoting properties whereas CM prepared with other B-cell mitogens and supernatants from ALL blasts in liquid culture had none. Our studies illustrate the complex and fastidious growth needs of ALL cells. The data have allowed us to refine a clonogenic blast progenitor assay that should facilitate study of proliferative properties of B and T lineage leukemias. The assay could be adapted further for detection of residual leukemia cells in marrow samples used for autologous transplantation, and in patients during complete hematological "remission."

Modulation of human marrow haematopoiesis by leucotrienes in vitro

The influence of products derived from the arachidonic acid 5-lipoxygenase (5-LO) pathway on normal human marrow haematopoiesis was studied using clonogenic assays. The leucotrienes (LT) B4 and C4 caused a reduction in granulocyte-macrophage (CFU-GM) as well as erythroid (CFU-E and BFU-E) colony numbers in a dose-dependent manner. Conversely, nordihydroguaiaretic acid (NDGA), a LT synthesis inhibitor, promoted proliferation of these colonies. The inhibitory effect of LTC4 but not that of LTB4 was abolished by FPL-55712, a LT antagonist; the enhanced colony growth induced by NDGA was reversed by both LTB4 and LTC4. LTD4 had no significant effect on colony growth despite its structural similarity to LTC4, which implies that the haematopoietic suppression by LTB4 and LTC4 is specific for these compounds. Depletion of marrow T-cells or removal of adherent cells, or both, did not alter the response to LTB4 and LTC4, suggesting that LT action is exerted directly on progenitor cells and probably is not mediated by other cell populations. Our studies show that the 5-LO pathway is functional in these culture systems and yields products with inhibitory properties. The 5-LO pathway may have an important regulatory function in normal marrow haematopoiesis.

Neurotoxicity associated with deferoxamine therapy

We have documented visual and auditory neurotoxicity in 42 of 89 patients with transfusion-dependent anemia who were receiving iron chelation therapy with subcutaneous deferoxamine (DFO). Of the affected groups, 13 presented with visual loss or deafness or both, and ophthalmologic, audiologic, and visual evoked potential studies (VEPs) uncovered abnormalities in 29 more. Four patients with visual loss had optic neuropathy with a marked decrease in acuity and loss of color vision. These 4, and 16 other asymptomatic patients, had abnormal VEPs. When DFO was stopped, 3 of 4 with visual problems regained normal visual function but VEPs remained abnormal. Of the other 16 with abnormal VEPs, 9 became normal or improved and 7 did not change; on restarting DFO, the 9 became abnormal again. There were 22 abnormal audiograms that showed a high-frequency sensorineural deficit; 13 patients were symptomatic and 4 needed hearing aids. On stopping DFO, 9 became asymptomatic but 15 audiograms remained abnormal and 2 deteriorated further on restarting the drug. An analysis of the clinical data showed that members of the affected group were younger, had lower serum ferritin values, and were self-administering higher doses of DFO/kg body weight. Significantly lower doses of DFO were being taken by patients without abnormalities than by those with visual symptoms, abnormal audiograms, or prolonged VEPs (P less than 0.001, less than 0.006, and less than 0.04, respectively). The data implicate high-dose DFO as a central factor in the pathogenesis of the neurotoxicity. Our serial studies provide the basis for effective yet safe DFO administration for patients who require the agent.

Juvenile chronic myelogenous leukemia

Juvenile chronic myelogenous leukemia (JCML) is a malignant hematopoietic disorder of monocyte-histiocyte lineage that affects children less than 4 years of age. Since the disease represents only 2% of all childhood leukemias, experience with it has been limited even in large centers. This review summarizes our 10 year institutional study of JCML as well as a comprehensive literature survey. The goal of the article is to underscore the cardinal features of juvenile chronic myelogenous leukemia that are useful for diagnosis, and to highlight recent advances in the understanding of the biology and treatment of the disease.

Synergistic antiproliferative effects on HL-60 cells: deferoxamine enhances cytosine arabinoside, methotrexate, and daunorubicin cytotoxicity

Deferoxamine (DFO), a widely used therapeutic iron chelator, was found to inhibit proliferation of the promyelocytic leukemia cell line HL-60 in a dose-dependent fashion when tested in a clonogenic assay at concentrations ranging from 1.0 to 10.0 microM. Cytosine arabinoside, methotrexate, and daunorubicin also produced dose-dependent inhibition of HL-60 colony growth when tested singly in vitro. When DFO, 1.0 microM, was included with each agent in dose-response studies, a synergistic enhancement of the antiproliferative effects was observed. This synergism probably results from a DFO-induced decrease in intracellular levels of deoxyribonucleoside triphosphates and an inhibition of the cells at the early S-phase of cell cycle. Our data suggest that DFO has potential as an adjunctive antileukemic agent.

Serial studies of auditory neurotoxicity in patients receiving deferoxamine therapy

Visual and auditory neurotoxicity was previously documented in 42 of 89 patients with transfusion-dependent anemia who were receiving iron chelation therapy with daily subcutaneous deferoxamine. Twenty-two patients in the affected group had abnormal audiograms with deficits mostly in the high frequency range of 4,000 to 8,000 Hz and in the hearing threshold levels of 30 to 100 decibels. When deferoxamine therapy was discontinued and serial studies were performed, audiograms in seven cases reverted to normal or near normal within two to three weeks, and nine of 13 patients with symptoms became asymptomatic. Audiograms from 15 patients remained abnormal and four patients required hearing aids because of permanent disability. Since 18 of the 22 patients were initially receiving deferoxamine doses in excess of the commonly recommended 50 mg/kg per dose, therapy was restarted with lower doses, usually 50 mg/kg per dose or less depending on the degree of auditory abnormality, and with the exception of two cases no further toxicity was demonstrated. Auditory deterioration and improvement, demonstrated serially in individual patients receiving and not receiving deferoxamine, respectively, provided convincing evidence for a cause-and-effect relation between deferoxamine administration and ototoxicity. Based on these data, a plan of management was developed that allows effective yet safe administration of deferoxamine. A dose of 50 mg/kg is recommended in those without audiogram abnormalities. With mild toxicity, a reduction to 30 or 40 mg/kg per dose should result in a reversal of the abnormal results to normal within four weeks. Moderate abnormalities require a reduction of deferoxamine to 25 mg/kg per dose with careful monitoring. In those with symptoms of hearing loss, the drug should be stopped for four weeks, and when the audiogram is stable or improved, therapy should be restarted at 10 to 25 mg/kg per dose. Serial audiograms should be performed every six months in those without problems and more frequently in young patients with normal serum ferritin values and in those with auditory dysfunction.