Clinical and biologic activity of the farnesyltransferase inhibitor R115777 in adults with refractory and relapsed acute leukemias: a phase 1 clinical-laboratory correlative trial.

R115777 is a nonpeptidomimetic enzyme-specific inhibitor of farnesyl protein transferase (FT) that was developed as a potential inhibitor of Ras protein signaling, with antitumor activity in preclinical models. This study was a phase 1 trial of orally administered R115777 in 35 adults with poor-risk acute leukemias. Cohorts of patients received R115777 at doses ranging from 100 mg twice daily (bid) to 1200 mg bid for up to 21 days. Dose-limiting toxicity occurred at 1200 mg bid, with central neurotoxicity evidenced by ataxia, confusion, and dysarthria. Non-dose-limiting toxicities included reversible nausea, renal insufficiency, polydipsia, paresthesias, and myelosuppression. R115777 inhibited FT activity at 300 mg bid and farnesylation of FT substrates lamin A and HDJ-2 at 600 mg bid. Extracellular signal-regulated kinase (ERK), an effector enzyme of Ras-mediated signaling, was detected in its phosphorylated (activated) form in 8 (36.4%) of 22 pretreatment marrows and became undetectable in 4 of those 8 after one cycle of treatment. Pharmacokinetics revealed a linear relationship between dose and maximum plasma concentration or area under the curve over 12 hours at all dose levels. Weekly marrow samples demonstrated that R115777 accumulated in bone marrow in a dose-dependent fashion, with large increases in marrow drug levels beginning at 600 mg bid and with sustained levels throughout drug administration. Clinical responses occurred in 10 (29%) of the 34 evaluable patients, including 2 complete remissions. Genomic analyses failed to detect N-ras gene mutations in any of the 35 leukemias. The results of this first clinical trial of a signal transduction inhibitor in patients with acute leukemias suggest that inhibitors of FT may have important clinical antileukemic activity. (Blood. 2001;97:3361-3369)

A phase I and pharmacokinetic study of subcutaneously-administered recombinant human interleukin-4 (rhuIL-4) in patients with advanced cancer.

PURPOSE: To investigate the pharmacokinetics and tolerability of recombinant human interleukin-4 (rhuIL-4), administered by daily subcutaneous injection, in patients with advanced cancer. PATIENTS AND METHODS: Fourteen patients with advanced cancer treated with rhuIL-4 at escalating dose levels of 0.25, 1.0 and 5.0 microg/kg/day, on days 1, 8-17, and 28-57. The primary endpoints of the study were toxicity of rhuIL-4 and the determination of the pharmacokinetics of rhuIL-4 when given by subcutaneous injection. Secondary endpoints included effects on blood counts, hematopoietic cell precursors, and various immunologic parameters. RESULTS: rhuIL-4 was well tolerated at all three dose levels. Detectable serum levels of IL-4 were found in patients at the 1.0 and 5.0 microg/kg/day dose levels. Peak serum IL-4 levels were achieved about 2 h after injection and IL-4 was still detectable 8 h after injection. No grade 4 toxicities were observed and grade 3 toxicities were confined to fever, headache and raised hepatic alkaline phosphatase. No consistent hematological or immunologic effects were observed. Although therapeutic efficacy was not an endpoint, one complete response (Hodgkin's disease) was observed. One patient with chronic lymphocytic leukemia progressed on therapy. CONCLUSION: rhuIL-4 up to 5.0 microg/kg/day is well tolerated when given by subcutaneous injection. Biologically relevant serum IL-4 levels can be achieved and sustained for at least 8 h after a single injection.

A phase II study of recombinant human interleukin-4 for advanced or recurrent non-small cell lung cancer.

PURPOSE: Recombinant human interleukin-4 is a pleiotropic cytokine that has shown antitumor activity in preclinical models and activity in phase I clinical trials. PATIENTS AND METHODS: This was a randomized phase II study testing two doses of recombinant human interleukin-4 (0.25 microgram/kg and 1.0 microgram/kg) administered subcutaneously three times per week in advanced non-small cell lung cancer. RESULTS: Sixty-three patients were enrolled (22 receiving 0.25 microgram/kg and 41 taking 1.0 microgram/kg); the median age was 61 years. Tumor histology included adenocarcinoma (41 patients), squamous cell carcinoma (12 patients), and other types (10 patients). The initial stage of disease was IIIb in 11 patients and IV in 52. Forty-four patients had received prior combination chemotherapy, predominantly cisplatin based. Recombinant human interleukin-4 was well tolerated, with no myelosuppression or elevations of liver enzymes, bilirubin, or blood glucose. The most frequent symptoms (any grade) in the 0.25-microgram dose were fatigue (13/22) and fever (8/22). Severe vomiting and dyspnea were observed in one patient each. In the 1.0-microgram dose group, a similar toxicity pattern (any grade) was seen, with fatigue (18/41), fever (14/41), and anorexia (12/41). One patient each had severe hypotension and chest pain. One patient was withdrawn from the study because of a perforated duodenal ulcer. Fifty-five patients were evaluable for response. In the 1.0-microgram group, there was one partial response of > 5.5 years' duration, and eight patients had stable disease of 106 to 350 days' duration. All patients had stage IV disease, and 24 patients had progressed during previous chemotherapy. In the 0.25-microgram group, one patient had stable disease. DISCUSSION: Recombinant human interleukin-4 can be administered safely and may have antitumor activity in non-small cell lung cancer. The higher dose (1.0 microgram/kg) may be associated with a higher incidence of stable disease. In view of the low toxicity seen at both dose levels, a phase II study investigating higher recombinant human interleukin-4 doses is ongoing. Recombinant human interleukin-4 should be explored further, alone or in combination with other cytokines, chemotherapy, or radiotherapy.

Safety evaluation of recombinant human interleukin-4. II. Clinical studies.

The safety and tolerability of Escherichia coli-derived recombinant human interleukin-4 (rhuIL-4) have been evaluated in phase I and phase II studies in human patients with a variety of malignancies. Clinical trials have demonstrated that subcutaneous administration of rhuIL-4 is safe and well tolerated at doses as high as 5 micrograms/kg/day and as high as 10 micrograms/kg when administered 3 times/week. Although preclinical safety studies in cynomolgus monkeys demonstrated a number of adverse effects following repeated daily dosing with rhuIL-4, similar effects have generally not been observed in human patients.

A phase II study of subcutaneous recombinant human interleukin-4 in metastatic renal cell carcinoma.

BACKGROUND: A study was conducted to assess the response rate for and toxicity of recombinant human interleukin-4 (IL-4) administered subcutaneously to outpatients with metastatic renal cell cancer. METHODS: Human recombinant IL-4 provided by Schering-Plough Research Corporation was administered subcutaneously to 19 patients at a dose of 1 microgram/kg three times per week. Eligibility included Cancer and Leukemia Group B performance status of 2 or better, adequate hematologic (leukocyte count < or = 2500/microliters platelets < or = 75,000/microliters), renal (creatinine < or = 2.0 mg/dl), and hepatic (serum glutamic oxaloacetic transaminase, serum glutamic pyruvic transaminase, and alkaline phosphatase < or = 3 times the upper limit of normal) function. Exclusion criteria included prior immunotherapy, clinically significant diabetes, pulmonary disease, and history of congestive heart failure or an ejection fraction of less than 40%. Soluble CD23 was measured in prospectively collected serum via an enzyme-linked immunosorbent assay technique. RESULTS: There was one minor response among 18 evaluable patients and median survival was only 35 weeks. Toxicities included fever, fatigue, myalgias, arthralgias, nausea, and anorexia. One patient each experienced a 14% asymptomatic decrease in the cardiac ejection fraction, a gastrointestinal bleed, and oral angioedema. Ten patients noted increased pain in tumor bearing areas, especially in areas of bony disease. Two patients with pre-existing vertebral disease experienced symptoms of cord compression. In 12 patients for whom complete data were available there was a mean increase in soluble CD23 of 2.6 ng/ml (P = 0.002) 1-2 weeks after therapy initiation. CONCLUSIONS: At this modest dose and schedule, IL-4 was tolerated in most patients. There was minimal biologic and clinical activity. Further development of IL-4 as a therapeutic agent in metastatic renal cell cancer at this dose and schedule is not supported by this study.

Potentiation of antitumor immunotoxins by liposomal monensin.

BACKGROUND: The cytotoxicity of specific ricin A-chain immunotoxins is greatly enhanced in vitro by the carboxylic ionophore monensin. However, the highly lipophilic nature of monensin, which is reflected in its poor solubility and short half-life, has restricted its use in in vivo animal studies. PURPOSE: The purpose of this study was to assess the ability of monensin incorporated in unilamellar vesicles (liposomes) to potentiate antitumor immunotoxins in vitro and in vivo. METHODS: Monensin was incorporated into liposomes and used in combination with specific immunotoxins against human tumor cell lines in vitro and in vivo. Inhibition of [3H]leucine incorporation was used to evaluate the cytotoxic action of immunotoxin with or without monensin in vitro on the following human tumor cell lines: H-MESO-1 malignant mesothelioma, LS174T colorectal carcinoma, and U373, U87, and MG-1 glioblastomas. For the in vivo studies of immunotoxins and liposomal monensin, BALB/c nu/nu mice were inoculated intraperitoneally with H-MESO-1 cells. RESULTS: Liposomal monensin potentiated the cytotoxic action of cell-specific anti-human transferrin receptor immunotoxin on H-MESO-1 target cells at a molar concentration of monensin that was 160-fold lower than the concentration of monensin in buffer that produced the same effect (0.3 nM versus 0.05 microM). Moreover, immunotoxin plus 0.1 microM liposomal monensin was fivefold more toxic for H-MESO-1 cells and 1000-fold and 2200-fold more toxic for human glioblastoma U373 and U87 cells, respectively, than immunotoxin plus 0.1 microM free monensin in buffer. Liposomal monensin produced similar effects when it was combined with different specific immunotoxins and other target cell lines (i.e., LS174T, U87, and CEM). Immunotoxin specificity was preserved with liposomal monensin, as shown by the absence of effect with non-cell-binding immunotoxins or on antigen-negative cell lines. In mice, liposomal monensin in combination with specific immunotoxin substantially prolonged survival, and three (21%) of 14 mice bearing H-MESO-1 xenografts treated with the liposomes showed no evidence of tumor at day 160 after treatment. Treatment with control immunotoxin plus liposomal monensin was ineffective. CONCLUSION: These findings suggest that encapsulation of monensin into liposomes increased the capacity of monensin to enhance the potency of cell-specific immunotoxin in vitro and in vivo.

Phase II trial of etoposide and cisplatin in patients with refractory and relapsed non-Hodgkin's lymphoma: Cancer and Leukemia Group B study 8351.

A phase-II study was conducted by the Cancer and Leukemia Group B (CALGB) in patients with refractory and relapsed non-Hodgkin's lymphoma (NHL) to assess the activity of the combination of etoposide and cisplatin. Sixty-five patients were entered on study, and 51 patients were evaluated for this report. The treatment regimen consisted of etoposide, 80 mg/m2 IV daily times 5 and cisplatin 20 mg/m2 IV daily times 5, repeated every 21 days. All patients had failed 1-3 prior chemotherapeutic regimens, had measurable disease, and had a performance status of 0-2. In the 51 evaluable patients, there were 4 complete responses (8%) and 12 partial responses (23%), for an overall response rate of 31% (95% Cl: 19%, 46%). In addition, 15 patients (29%) had some improvement in disease and 6 (12%) had stable disease. Failure-free survival for the 51 eligible patients was 40% at 3 months, 23% at 6 months, and 15% at 1 year. Significant toxicity was observed with this regimen. Severe neutropenia occurred in 20 patients (39%), severe anemia in 8 patients (16%), and severe thrombocytopenia in 18 patients (35%). One patient died of infection. Severe neurotoxicity (1) and hemorrhage (3) were also seen. The etoposide, cisplatin combination is active in NHL; however, in this dose and schedule their combined activity is only minimally better than published reports of etoposide alone. Further studies of related combinations are under evaluation by the CALGB.

A liposome based platelet substitute, the plateletsome, with hemostatic efficacy.

The complexity of platelet mediated hemostasis has hindered development of a platelet substitute for transfusion therapy. In the current study, the hemostatic efficacy of a liposome based modality, the plateletsome, is demonstrated. A deoxycholate extract of a platelet membrane fraction, with a minimum of 15 proteins including GPIb, GPIIb-IIIa and GPIV/III, was incorporated into sphingomyelin: phosphatidylcholine: monosialylganglioside or egg phosphatide small unilamellar vesicles by reverse-phase/sonication and French press extrusion. These plateletsomes decreased bleeding by 67% in the tail bleeding time in rats made thrombocytopenic (platelets < 30,000/microliters) with external irradiation (7-9Gy) by Cesium source. Efficacy was also demonstrated in the thrombocytopathic, Fawn-Hooded rat, but to a lesser extent than in the thrombocytopenic animals. Direct plateletsome infusion to the tail wound was more effective than systemic administration for all effective preparations. On post-mortem examination, no pathologic thrombi were detected by gross and histopathologic examination of the lungs, livers, kidneys, or spleens of thrombocytopenic or normal animals after plateletsome infusion. No evidence of intravascular coagulation, monitored by levels of circulating fibrinogen and platelet counts, was observed when plateletsomes were administered intravenously to rabbits. No deleterious effect, either inhibition or hyperaggregability, on platelet aggregation studies in vitro was observed. While further refinements are clearly required, this study indicates that liposomes bearing specific platelet proteins may provide a basis for a clinically applicable platelet substitute.

Effect of calcium channel blockers on platelet GPIIb-IIIa as a calcium channel in liposomes: comparison with effects on the intact platelet.

The platelet membrane glycoprotein IIb-IIIa complex is essential for platelet aggregation and functions as a fibrinogen receptor on the activated platelet. When incorporated into phospholipid vesicles, this glycoprotein complex can function as an apparent calcium channel which facilitates the transit of calcium across a phospholipid barrier. In order to further evaluate this calcium channel, the effect of calcium channel blockers of the dihydropyridine (nifedipine and nicardipine), arylalkylamine (verapamil) and benzothiazepine (diltiazem) classes were evaluated on GPIIb-IIIa liposomes with encapsulated fura-2 (a fluorescent calcium indicator). Nicardipine, verapamil, and nifedipine significantly inhibited calcium influx into GPIIb-IIIa liposomes; however, this required 190 microM, 400 microM, and 140 microM drug, respectively. These concentrations are 10-1,000 fold greater than those clinically obtainable. In contrast, diltiazem at concentrations greater than 220 microM and amiloride at concentrations greater than 800 microM showed no inhibitory effects. When aspirinized platelets were activated with 30 micrograms/ml bovine fibrillar collagen, both nicardipine and diltiazem produced a decrease in both the initial rise and maximum cytoplasmic calcium concentration. Parallel experiments were performed to assess the effects of verapamil, nicardipine, and diltiazem on platelet aggregation in platelet rich plasma. Nicardipine, 190-380 microM, induced a prolongation of the lag phase, but no effect on the final degree of platelet aggregation to collagen. Similar inhibition of platelet aggregation was seen with diltiazem and verapamil although the effect of diltiazem was less pronounced particularly at higher concentrations of collagen. No effect was seen on aggregation with 32 microM ADP which is release independent, or on the primary wave of low dose ADP induced platelet aggregation.(ABSTRACT TRUNCATED AT 250 WORDS)

Eosinophilia-myalgia syndrome associated with L-tryptophan ingestion. Analysis of four patients and implications for differential diagnosis and pathogenesis.

Four patients fulfilling the case definition for eosinophilia-myalgia syndrome are described, including one whose disease began in 1986. Each displayed a variety of symptoms: one suffered principally from myalgia and recovered spontaneously on discontinuation of L-tryptophan therapy; one exhibited progressive sclerodermiform skin changes, neuropathy, and myopathy; a third had prominent neuromuscular disease and sclerodermiform skin changes; and the fourth experienced profound weight loss, an axonal polyneuropathy, and perivascular lymphoid infiltrates simulating a lymphoma. Evidence of T-cell activation was present in peripheral blood and affected tissues during the clinically active progressive phase of disease. Among other manifestations pleural effusion, cutaneous vasculitis, joint contractures, and bloody diarrhea were observed. A history of L-tryptophan ingestion should be sought in patients with myalgia, fatigue, or the above outlined symptoms.

Interferon therapy of relapsed and refractory Hodgkin's disease: Cancer and Leukemia Group B Study 8652.

A phase II trial of alpha 2b-interferon in patients with relapsed or refractory Hodgkin's disease was conducted by the Cancer and Leukemia Group B. Nineteen patients were eligible for study. These patients had received at least two (median of four) previous chemotherapeutic programs and 79% had received prior radiation therapy. Three patients had undergone intensive chemotherapy and autologous bone marrow transplantation. The treatment regimen consisted of interferon-alpha 2b 10 X 10(6) IU/m2 subcutaneously three times per week. Only limited antineoplastic activity was seen in this heavily pretreated group of patients. There was one partial response and four patients had reduction in measurable disease not meeting the criteria for partial response. The drug was well tolerated. Toxicity was predominantly myelosuppression. Thrombocytopenia was particularly severe in patients with bone marrow involvement. The observed antineoplastic activity, albeit limited, in this heavily pretreated group of patients suggests a potential role for this agent in combination regimens in patients with earlier disease.

Phase II trial of etoposide and cis-diaminodichloro-platinum in patients with refractory and relapsed Hodgkin's disease: Cancer and Leukemia Group B (CALGB) Study 8353.

A phase II study was conducted by the Cancer and Leukemia Group B (CALGB) in patients with refractory and relapsed Hodgkin's disease (HD) to assess the activity of the combination of etoposide and cis-platin. Twenty-seven patients were entered; 22 were evaluated for this report. Treatment consisted of etoposide (VP-16), 80 mg/m2 IV over 1 hour and cis-platin, 20 mg/m2 IV over 1/2-1 hour; both agents were given daily for 5 days and repeated every 21 days. All patients had received at least 2 prior chemotherapy regimens, had measurable disease, and most (86%) had a performance status of 0-1. In the 22 evaluable patients, there were 4 complete responses (18%) and 4 partial responses, for an overall response rate of 36% (95% Cl: 17.2%, 59.3%). Response duration was from 2.1 to 31 months. Significant toxicity was observed with this regimen. Ten patients (45%) had leukopenia less than 1,000/microliters, and 11 patients (50%) had thrombocytopenia less than 25,000/microliters. Serum creatinine levels reached greater than 2.0 in 14% of patients. Seven patients (32%) had severe nausea and vomiting. VP-16, cis-platin appears to be an active combination in HD; however, their combined activity is only marginally better than reported single-agent activity for VP-16 in the doses and schedule used. Further studies of related combinations in HD are currently under evaluation by the CALGB.

Ligand inhibition of the platelet glycoprotein IIb-IIIa complex function as a calcium channel in liposomes.

Platelet glycoproteins IIb and IIIa function as a fibrinogen receptor on the activated platelet. We have shown that these glycoproteins can be incorporated onto the surface of phosphatidylcholine vesicles with retention of fibrinogen and antibody binding properties and can permit Ca2+ transit across the phospholipid bilayer. In the current study we demonstrate that this apparent Ca2+ channel function is specifically inhibited by the synthetic analogue of the fibrinogen gamma COOH-terminal peptide, His-His-Leu-Gly-Gly-Ala-Lys-Gln-Ala-Gly-Asp-Val (His-12-Val), but not by the adhesive protein sequence Arg-Gly-Asp-Ser (RGDS). Prior incubation of IIb-IIIa liposomes with RGDS prevented Ca2+ transit inhibition by 25 microM His-12-Val, analogous to RGDS inhibition of His-12-Val binding to platelets. His-12-Val inhibited a minor component of transmembrane Ca2+ influx into ADP and thrombin-activated human platelets but had no effect on steady-state platelet 45Ca flux. These data indicate that ligand binding may exert a regulatory influence on transmembrane Ca2+ influx into activated platelets. The difference in inhibitory potency of the peptides studied may be related to differences in conformational changes in the glycoprotein IIb-IIIa complex induced by His-12-Val and RGDS, steric considerations, or differences in interactions with glycoprotein IIb Ca2+ binding domains.

Histologic changes induced in skin by extravasation of doxorubicin (adriamycin).

Extravasation of doxorubicin in skin and soft tissue causes necrosis and ulceration. These ulcers form slowly and heal with great difficulty. The cause of ulceration is not known. Histologic changes in two patients suggest that an exaggeration of interface dermatitis like epidermal changes may be responsible for epidermal necrosis. This process may be enhanced or complicated by ischemic changes caused by thrombosis of the venous tributaries at the site of the intravenous infusions. Squamous syringometaplasia seen in both cases can be confused with squamous cell carcinoma. Dermal changes mimic those seen in radiation injury.

Interaction of platelet factor four with cultured vascular endothelial cells.

Platelets secrete a low-molecular-weight protein, platelet factor four (PF-4), which binds to and neutralizes heparin and related sulfated glycosaminoglycans (GAGs). To examine the interactions of PF-4 with the GAGs present on endothelial cell surfaces, we incubated 125I-PF-4 with cell suspensions derived from confluent monolayers of cultured bovine aortic endothelium. Binding of 125I-PF-4 was inhibited by a 100-fold excess of nonradioactive PF-4 and varied with duration and temperature of incubation. At 4 degrees C, binding reached equilibrium at 20 minutes with kd = 2.87 mumol/L and Bmax of 63.83 pmol/10(5) cells. Binding capacity was reduced 83.4% by brief incubation of endothelial cells with trypsin and 46.67% by incubation with Flavobacterium heparinase, but was unchanged by chondroitin-ABCase treatment. At 37 degrees C, PF-4 was internalized by confluent monolayer of bovine aortic endothelial cells primarily through low-affinity adsorptive endocytosis. The internalized PF-4 was degraded to amino acids and small peptides with 50% conversion after 18-hour incubation. These studies demonstrate that a secreted platelet protein can bind to and enter endothelial cells. Binding may explain the rapid clearance of released PF-4 from plasma and could have important local effects on endothelial structure and function.

Platelet glycoproteins IIb and IIIa as a calcium channel in liposomes.

Human platelet membrane glycoproteins IIb and IIIa (GPIIb and IIIa) were incorporated into phospholipid vesicles by the reverse-phase technique to assess the ability of GPIIb and IIIa to function as a Ca2+ channel. Movement of Ca2+ across the lipid bilayer was quantitated by injection of proteoliposomes with encapsulated Fura-2 into Ca2+ buffers and measurement of Fura-2 fluorescence as an indicator of Ca2+ influx. Reciprocally, to assess the function of proteins in an inside-out orientation, Ca2+-loaded vesicles were injected into Ca2+-free buffer and Ca2+ efflux monitored by a calcium electrode. Incorporation of the IIb-IIIa complex produced significant facilitation of Ca2+ movement across the lipid bilayer. No net transmembrane Ca2+ movement was seen with dissociated IIb and IIIa. Movement of Ca2+ was proportional to the transmembrane Ca2+ gradient. Ca2+ movement into the vesicles was inversely proportional to extravesicular NaCl from 25 to 150 mmol/L, analogous to several studies in the intact platelet. Adenosine triphosphate had no effect on Ca2+ movement into or out of the vesicles. Specific inhibition of a Ca2+ shift into the vesicles was seen with M148, a monoclonal antibody to IIb/IIIa, while no inhibition was observed with a panel of other anti-IIb/IIIa monoclonal antibodies. This suggests that a specific site on the complex or orientation of the complex is essential for calcium channel function. These data demonstrate that the GPIIb/IIIa complex can serve as a passive Ca2+ channel across a phospholipid bilayer and has the potential to play a role in Ca2+ flux across the platelet plasma membrane.

Biological characterization of cloned permanent stromal cell lines from anemic Sl/Sld mice and +/+ littermates.

Permanent cloned bone marrow stromal cell lines, designated Sld1, Sld2, Sld3, were derived from long-term bone marrow cultures (LTBMC) of Sl/Sld mice and littermate WCB6F1 mice (designated +/+1, +/+2, +/+1.10, and +/+2.4). Production of extracellular matrix proteins by these cell lines was detected using specific antibodies. Fibronectin, laminin, and collagen type IV were detected in all clonal cell lines tested. Each cloned stromal cell line or parent stromal cell culture was also tested in vitro for support of engrafted hemopoietic stem cells. Engrafted hemopoietic stem cells from C57BL/6J LTBMCs forming CFU-GEMM and BFUe colonies were supported at 76% and 44% efficiency by lines +/+2.4 and +/+1.10, respectively, compared to the number recovered from parent uncloned C57BL/6J stromal cell cultures. In contrast, cell lines Sld1 and Sld3 were significantly less supportive of CFU-GEMM progenitor cells (14% and 18% efficiency, respectively) and erythroid progenitors (6% and less than 0.1% efficiency, respectively). Some Sld lines also showed reduced support compared to +/+ cell lines of a clonal multipotential erythroid cell line B6SUtA. These permanent stromal cell lines should be useful in elucidation of the specific microenvironmental factors required for support of multilineage and erythroid progenitor cells.

Effect of L-asparaginase administration on coagulation and platelet function in children with leukemia.

The use of L-asparaginase during remission induction in patients with leukemia is associated with coagulation abnormalities, which may present either as thrombosis or hemorrhage. However, because of the multiple pharmacologic and hematologic variables present in these patients, the exact contribution of L-asparaginase to these coagulation abnormalities is unclear. We studied platelet function and plasma coagulation parameters in 12 pediatric patients with acute lymphoblastic leukemia (ALL) receiving daily L-asparaginase as a single agent when in complete remission. Changes in the prothrombin time (PT), partial thromboplastin time (PTT), and fibrinogen, while statistically significant, remained within or close to the normal range during the study. Platelet function also remained normal during the study. In contrast, levels of protein C antigen decreased to a mean of 42%, a significant change from pretreatment values. Levels of antithrombin III (AT III) were likewise depressed to 15 mg/dL (34% of pretreatment value). Despite these changes in the levels of physiologic inhibitors of coagulation, this schedule of L-asparaginase administration was associated with only rare clinical thrombosis, and this study suggests that the development of this complication may be dependent on the presence of additional factors.