Deoxycoformycin Research Articles

Puromycin aminonucleoside induces apoptosis and increases HNE in cultured glomerular epithelial cells

Puromycin aminonucleoside induces apoptosis and increases 4-hydroxy-2-nonenal (HNE) in cultured glomerular epithelial cells. We have previously reported the detachment of cultured glomerular epithelial cells (GECs) from their substrata by puromycin aminonucleoside (PAN) treatment. In this study we explored whether or not apoptosis was involved in the mechanisms of the detachment. DNA fragmentation on gel electrophoresis was clearly shown by 10 −3 M PAN treatment of GECs. Nuclear staining by Hoechst 33342 indicated the greatest number of apoptotic cells at 10 −3 M PAN for 48 h treatment. Similarly, TUNEL methods revealed maximal apoptotic cells at 10 −3 M PAN for 48 h treatment. Caspase-3 (like) protease activity increased at 10 −3 M PAN, and decreased at 2 × 10 −3 M PAN for 48 h treatment as well as at 10 −3 M PAN for 60 h treatment. Pretreatment with 2′-deoxycoformycin (DCF), inhibitor of adenosine deaminase, abolished these effects of PAN on cultured GECs. PAN treatment increased HNE, a lipid peroxide adduct, modified protein in cultured GECs, which was also prevented by pretreatment by DCF. These results for the first time indicate that the PAN-induced detachment of GECs from culture substrata is mediated at least in part through apoptosis via oxidative stresses by adenosine deaminase activity.

Progress in the treatment of non-Hodgkin's lymphomas

The authors analyze the progress achieved in the treatment of low-grade as well as of high-grade non-Hodgkin's lymphomas. The challenging task in the treatment of low-grade or indolent lymphomas still is to decide whether watchful waiting is sufficient or whether chemotherapy is necessary and how aggressive this treatment should be. Among the new chemotherapeutic agents the role of purine analogues should be emphasized, fludarabin is especially important in the treatment of chronic lymphocytic leukemia and follicular lymphoma, while pentostatin and cladribine have revolutionized the treatment of hairy cell leukemia. Treatment with monoclonal antibodies, radioimmunoconjugates as well as autologous or allogeneic stem cell transplantation are potential new therapeutic options in the treatment of low-grade non-Hodgkin's lymphomas. In the case of aggressive non-Hodgkin's lymphomas risk-adapted strategies help the choice between standard or more intensive treatment options. In patients with relapsed high-grade lymphomas stem cell transplantation is indicated. In patients with marginal zone lymphoma the combination of hyperCVAD protocol + stem cell transplantation greatly improves prognosis.

Effect of adenosine kinase, adenosine deaminase and transport inhibitors on striatal dopamine and stereotypy after methamphetamine administration

The effect of adenosine kinase (AKA), adenosine deaminase (ADA) and transport inhibitors on the release of dopamine (DA) induced by methamphetamine (MTH) in rat striatum was assessed using in vivo microdialysis in freely moving rats. MTH injected in a dose of 3×5 mg/kg i.p. at 2-hour intervals produced a massive release of DA. This excessive release of DA was inhibited by the ADA inhibitor 2′-deoxycoformycin (DCF), the AKA inhibitor 5′-iodotubercidin (IOT) and the adenosine uptake inhibitor dilazep (DIL), each of them given locally to the striatum via a microdialysis probe at a concentration of 100 μM. Perfusion with the same concentrations of erythro-9-(2-hydroxy-3-nonyl)adenine (EHNA) and 5′-amino-5′-deoxyadenosine (NH 2dAD), ADA and AKA inhibitors, respectively, induced a considerably weaker effect on DA release. The non-selective antagonist of adenosine A 1/A 2A receptor caffeine (75 μM) significantly prevented the inhibitory effect of DCF, IOT and DIL on the MTH-induced DA release. Intrastriatal administration of DCF, IOT and DIL (5 nmol/μl before each injection of MTH) inhibited the stereotypy induced by MTH. The striatal content of DA and its metabolites 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA), decreased by MTH administration and measured 5 days after treatment with the toxin, was reversed by all the inhibitors at the order of potency as follows: IOT>DCF>DIL. Direct agonists of adenosine A 1 and A 1/A 2A receptors, N 6-cyclopentyladenosine (CPA) and 5′- N-ethylcarboxamidoadenosine (NECA), respectively, given intrastriatally (5 nmol/μl) completely abolished the MTH-induced stereotypy and the fall in the striatal content of DA, DOPAC and HVA. The above results show that augmentation of endogenous adenosine in rat striatum by inhibition of its metabolism or uptake—despite the differences in the efficacy of various inhibitors—may provide neuroprotection against a toxic action of MTH.

Second malignancies as a consequence of nucleoside analog therapy for chronic lymphoid leukemias.

The nucleoside analogs fludarabine, 2'-deoxycoformycin (DCF), and 2-chlorodeoxyadenosine (CdA), commonly used in the treatment of patients with indolent lymphoid malignancies such as chronic lymphocytic leukemia (CLL) and hairy cell leukemia (HCL), are associated with myelosuppression and profound and prolonged immunosuppression. These complications raise the possibility of an increase in secondary malignancies in patients whose disease already places them at greater risk. The purpose of the present study was to assess the frequency of second tumors in patients with CLL who are treated with fludarabine and in patients with HCL who are treated with DCF and CdA. We reviewed the long-term follow-up data for 2,014 patients treated on National Cancer Institute Group C protocols with fludarabine for relapsed and refractory CLL and with DCF and CdA for HCL using a Second Cancer Report. The numbers of observed and expected secondary tumors were compared. Median follow-up periods for the DCF (n = 409), fludarabine (n = 724), and CdA (n = 979) studies were 6.9, 7.4, and 5.1 years, respectively. The 111 malignancies were most commonly lymphoma (25 patients), prostate (19), lung (15), colorectal (nine), bladder (six), and breast (six), but also CNS, stomach, ovary, head and neck, melanoma, sarcoma, testicular, and myeloid leukemias. Compared with age-adjusted 1994 Surveillance and Epidemiology End-Results rates for the general population, the observed/expected frequencies for DCF, fludarabine, and CdA were 1.43 (95% confidence interval [CI], 0.93 to 2.10), 1.65 (95% CI, 1.04 to 2.47), and 1.50 (95% CI, 1.14 to 1.93), respectively, indicating a significant (at P =.05) increase in risk for patients treated on the latter two protocols compared with a normal population. However, these values are consistent with the increase already associated with these diseases. Despite their immunosuppression, nucleoside analogs can be safely administered to patients with CLL or HCL without a significantly increased risk of secondary malignancies.

The beneficial effect of 2'-deoxycoformycin in renal ischemia-reperfusion is mediated both by preservation of tissue ATP and inhibition of lipid peroxidation.

Renal ischemia injures the renal tubular cell by disrupting the vital cellular metabolic machinery. Further cell damage is caused when the blood flow is restored by oxygen free radicals that are generated from xanthine oxidase. Oxygen radicals cause lipid peroxidation of cell and organelle membranes, disrupting the structural integrity and capacity for cell transport and energy metabolism. In the present study, the possible therapeutic usefulness of the adenosine deaminase inhibitor, 2'-deoxycoformycin (DCF), during renal ischemia and reperfusion injury was investigated. The effects of DCF on renal malondialdehyde (MDA) and ATP levels were studied after 45 min ischemia and 15 min subsequent reperfusion in rat kidneys. MDA levels remained unchanged during ischemia, but increased after the subsequent reperfusion. DCF pretreatment (2.0 mg/kg i.m.) decreased MDA and increased ATP levels during the ischemia-reperfusion period. DCF exerts a dual protective action by facilitating purine salvage for ATP synthesis and inhibiting oxygen radical-induced lipid peroxidation. These results suggest that DCF therapy could be beneficial in the treatment of ischemia-reperfusion renal injuries.

Absorption and Intestinal Metabolism of Purine Dideoxynucleosides and an Adenosine Deaminase-Activated Prodrug of 2′,3′-Dideoxyinosine in the Mesenteric Vein Cannulated Rat Ileum

□ This study investigates the mechanisms of absorption and the role of intestinally localized purine salvage pathway enzymes on the ileal availabilities of 2′,3′-dideoxyinosine (ddI), a substrate for purine nucleoside phosphorylase (PNP); 2′-fluoro-2′,3′-dideoxyinosine (F-ddI), a non-PNP substrate; and 6-chloro-2′,3′-dideoxypurine (6-Cl- ddP), an adenosine deaminase (ADA) activated prodrug of ddI. The potential for increasing the intestinal availability of 6-Cl-ddP through the use of ADA inhibitors, namely, 2'-deoxycoformycin (DCF) and erythro-9-(2-hydroxy-3-nonyl)adenine (EHNA), is also explored. Drug permeability coefficients across the intestinal epithelium were determined in in situ perfusions in the mesenteric vein cannulated rat ileum based on both drug appearance in blood (Pblood) and disappearance from the lumen (Plumen) and their paracellular and transcellular components were estimated by comparison to the permeabilities of two paracellular markers, mannitol and urea. Values of Pblood for ddI were determined to be (1.1±0.3) × 10-6 cm/s, in close agreement with the value of (1.0±0.3) × 10-6 cm/s obtained for F-ddI, a PNP resistant analogue of ddI having virtually the same molecular size and lipophilicity as ddI. This indicates that PNP may not play an important role in the low intestinal absorption of ddI. The Pblood for 6-Cl-ddP, (19±2) × 10-6 cm/s, was 4.5-fold lower than Plumen, (84±12) × 10-6 cm/s, which means that 77±6% of 6-Cl-ddP was metabolized during its intestinal transport, thus qualitatively accounting for the low oral bioavailability (7%) of 6-Cl-ddP observed in vivo in rats. Extensive intracellular metabolism of 6-Cl-ddP by ADA was confirmed by the high concentrations of ddI found both in the intestinal lumen and blood during 6-Cl-ddP perfusions and by a rate of ddI appearance in blood which was ≈10-fold higher than ddI controls. Co-perfusion of the potent, hydrophilic ADA inhibitor DCF (K=0.0010.05 nM) with 6-Cl-ddP led to only partial inhibition of intestinal ADA, while complete inhibition was obtained using the less potent but more lipophilic inhibitor EHNA (Ki=1-20 nM). Hence, EHNA may be used to improve intestinal absorption of 6-Cl-ddP in vivo.

The significance of minimal residual disease in hairy cell leukaemia treated with deoxycoformycin: a long-term follow-up study.

We investigated the clinical significance and long-term follow-up of detecting minimal residual disease (MRD) in hairy cell leukaemia (HCL) in complete remission (CR) after treatment with deoxycoformycin (DCF). MRD was assessed in 23 patients by immunophenotyping peripheral blood and bone marrow frozen sections using a panel of antibodies, CD11c, CD25, CD103 and HC2, which detect hairy cells. 31 cases with active HCL were used as controls. 10/23 patients (43%) had MRD in bone marrow (seven), blood (one) or both sites (two) which was not detected on haematoxylin-eosin bone marrow sections nor by immunohistochemistry on paraffin sections in six cases tested. Sequential studies in four cases did not show changes in the amount of MRD. At a median follow-up of 72 months (range 15-108), 5/23 (22%) patients have relapsed with a median time of 59 months (range 15-105). MRD was detected in three of the five patients who relapsed. In the two patients with negative MRD, one relapsed with an abdominal mass and the other was a late relapse at 84 months. MRD was also documented in 7/18 patients who continued in clinical CR for a median of 80 months (range 63-98). There were no statistical differences in disease-free survival between MRD+ and MRD- patients (P = 0.8). Our findings indicate that relapse after long-term remission achieved with DCF cannot be predicted when MRD is detected by sensitive methods. A search for other parameters such as proliferative rate of the residual cells or chest and abdominal CT scan might identify patients with a higher probability of disease recurrence.

Weekly Administration of 2-Chlorodeoxyadenosine in Patients With Hairy-Cell Leukemia: A New Treatment Schedule Effective and Safer in Preventing Infectious Complications

To the Editor: The treatment options for hairy-cell leukemia (HCL) have increased rapidly in the last 10 to 15 years. HCL patients currently can benefit from several agents such as α-interferon (α-IFN), deoxycoformycin (DCF), and 2-chlorodeoxyadenosine (2-CdA). Despite complete remission (CR)

Response duration and recovery of CD4+ lymphocytes following deoxycoformycin in interferon-alpha-resistant hairy cell leukemia: 7-year follow-up.

The long-term outcome of patients with hairy cell leukemia resistant to interferon-alpha (IFN-alpha) following treatment with deoxycoformycin (DCF) was examined, and the kinetics of recovery of lymphocyte subsets and factors influencing the rate of recovery investigated. Between May 1986 and May 1989, 15 patients with histologically confirmed hairy cell leukemia resistant to IFN-alpha received DCF 4 mg/m2 every 2 weeks with 12 cycles planned. All 15 patients were evaluable for response and have been followed for a median of 88 months (range, 72 to 106 months) from the start of therapy. Fourteen patients responded to DCF, all attaining complete remission (CR) (response rate 93%; 95% confidence interval, 69% to 100%). Seven patients have developed recurrent disease after 45 to 74 months. Using the method of Kaplan and Meier, the median remission duration is 74 months and, at 8 years, 46% (95% confidence interval, 33% to 59%) of patients are projected to be in ongoing CR. The seven relapsing patients have responded to treatment with 2-chlorodeoxyadenosine (2-CdA) and all 15 patients remain alive. After DCF, nadir CD4+ and CD8+ lymphocyte counts were significantly lower than prior to therapy (P < 0.0001 and P = 0.05, respectively), but returned to baseline levels during follow-up. Median times to attainment of the lower limit of the normal range of CD4+ and CD8+ lymphocytes were 54 and 36 months, respectively. Those patients who had previously undergone splenectomy (n=7) had higher baseline CD4+ (P= 0.073) and CD8+ (P= 0.043) lymphocyte counts and more rapid recovery of both CD4+ (P= 0.027) and CD8+ lymphocyte counts (P = 0.016) than non-splenectomized patients. One elderly patient (age, 78 years) was diagnosed with subsequent malignancy. No late opportunistic infections were observed. Resistance to IFN-alpha does not impair subsequent responsiveness of patients with hairy cell leukemia to treatment with DCF. Responses are durable and without evidence of long-term sequelae. CD4+ and CD8+ lymphocyte subsets recover slowly without clinical manifestations of immunodeficiency. Splenectomized patients appear to have higher baseline lymphocyte counts and more rapid lymphocyte recovery following treatment with DCF.

An Adenosine Deaminase Inhibitor Prevents Puromycin Aminonucleoside Nephrotoxicity

Puromycin aminonucleoside (PAN) toxicity was totally inhibited in the rat in vivo and in cultured glomerular epithelial cells (GECs) in vitro using the adenosine deaminase (ADA) inhibitor, 2′-deoxycoformycin (DCF). DCF completely inhibited ADA activity in glomeruli and protected against the development of PAN nephrosis; the 24-h urinary protein excretion of treated rats compared with controls (PAN rats) 9 days after PAN injection was 16 ± 2 mg and 524 ± 55 mg, respectively (p < .01). Morphological examination also demonstrated that the glomerular epithelial cells were protected against PAN-induced damage. Furthermore, when DCF was added to the first passage of GECs simultaneously with PAN, the adenosine triphosphate contents of remnant GECs on culture substrata increased in a dose-dependent manner, and PA toxicity was completely inhibited by 10−4 M DCF. The order of ADA activity in glomeruli from various species was as follows: rat > monkey > guinea pig > dog > rabbit > mouse. High activity of ADA in the glomerulus was limited to species in which PAN induced nephrosis. Additionally, DCF increased glomerular cyclic AMP contents, resulting from enhanced adenosine accumulation in the pericellular space. These results indicate that the pathogenesis of PAN toxicity is closely related to adenosine metabolism and that ADA plays a key role in this model. Furthermore, we speculate that DCF contributes to the inhibition of reactive oxygen metabolites by decreasing the substrate of xanthine oxidase and/or increasing pericellular adenosine accumulation.Copyright © 1997 Elsevier Science Inc.

Role of brain tissue localized purine metabolizing enzymes in the central nervous system delivery of anti-HIV agents 2'-beta-fluoro-2',3'-dideoxyinosine and 2'-beta-fluoro-2',3'-dideoxyadenosine in rats.

This study examines the central nervous system (CNS) delivery of 2'-beta-fluoro-2',3'-dideoxyadenosine (F-ddA) and 2'-beta-fluoro-2',3'-dideoxyinosine (F-ddI), acid stable analogues of dideoxyadenosine (ddA) and dideoxyinosine (ddI) having reduced susceptibility to purine salvage pathway enzymes important in the metabolism of ddA and ddI, adenosine deaminase (ADA) and purine nucleoside phosphorylase (PNP), respectively. Their CNS delivery compared to that for ddI provides insight into the role of brain tissue ADA and PNP in these processes. Brain and cerebrospinal fluid (CSF) concentration-time profiles were obtained for F-ddI during and after intravenous infusions of F-ddI, and for both F-ddA and F-ddI after F-ddA infusions in normal rats or rats pre-treated with the ADA inhibitor 2'-deoxycoformycin (DCF). Rate constants for CNS entry, efflux and metabolism were estimated by computer fits using plasma concentration-time profiles as the driving force functions. The CNS delivery of F-ddI did not differ significantly from that for ddI. F-ddA, which is more lipophilic than F-ddI, provided higher brain (approximately 8x) and CSF (approximately 11x) concentrations of total dideoxynucleoside (F-ddA and F-ddI) compared to F-ddI. Deamination by brain tissue ADA to form F-ddI reduced CNS levels of intact F-ddA but provided higher brain parenchyma (5x) and CSF/plasma (3x) ratios of F-ddI relative to F-ddI controls. Thus, F-ddA functions in part as a CNS-activated prodrug of F-ddI. DCF pre-treatment inhibited brain tissue ADA, abolishing the prodrug effect, and enhancing F-ddA concentrations in both brain parenchyma (5x) and CSF (6x). PNP metabolism does not appear to play a role in the low CNS delivery of ddI. On the other hand, deamination of F-ddA by brain tissue ADA is an important process, such that F-ddA functions in part as a CNS-activated prodrug of F-ddI. Enhanced CNS uptake of intact F-ddA can be achieved with ADA inhibition.

Purine nucleoside analogues: fludarabine, pentostatin, and cladribine

Purpose. The primary objective of this article is to continue the discussion of the pharmacology, phar macokinetics, clinical use, and adverse effects of the currently approved adenosine analogues, focusing on pentostatin. This is part two of a three part series. Data Sources. We reviewed the literature through a MEDLINE search from 1986 to 1996. Rele vant articles cited in the literature obtained by MED LINE searching also were considered. We searched the following terms: fludarabine, cladribine, pentosta tin, apoptosis, and adenosine analogues. The search was restricted to the English language. Data Extraction. We have reviewed the current literature in regard to the chemistry, mechanisms of action and pharmacology, pharmacokinetics, clinical use, adverse effects, drug interactions, indications, formulation, dosage, administration, and pharmaceu tical issues of the currently approved adenosoine analogues, focusing on pentostatin. Data Synthesis. The adenosine analogues are structurally similar agents used in the management of hematological malignancies. Pentostatin and cladrib ine are both active agents in the treatment of hairy cell leukemia. There are no comparative clinical trials between the agents, and we have provided compari sons based on pharmacology, clinical experience, adverse effects, and cost.

2'-deoxyadenosine induces apoptosis in rat chromaffin cells.

We show here that 2'-deoxyadenosine (2'-dAdo) but not adenosine was toxic to chromaffin cells of 3-4-week-old rat adrenal glands. More than 75% of the cells plated in culture gradually died over a 3-day period in the presence of 100 microM 2'-dAdo plus 3 microM deoxycoformycin (DCF). Morphological observations together with bisbenzimide staining and terminal deoxynucleotidyl transferase-mediated nick and labeling showed membrane blebbing, shrinkage of cell bodies, chromatin condensation, and DNA fragmentation, suggesting apoptosis-like cell death by 2'-dAdo. Lethal effects of 2'-dAdo were potentiated by DCF, a drug that inhibits adenosine deaminase. 2'-dAdo-prompted cell death was not prevented by inhibitors of nucleoside transporter (3 microM dilazep or 1 microM nitrobenzylthioinosine), precursors of pyrimidine nucleotide biosynthesis (300 microM uridine or 100 microM 2'-deoxycytidine), or 5 mM nicotinamide. Cells incubated with 2'-dAdo (100 and 300 microM) showed a three- and ninefold, respectively, increase in content of dATP, a product known to be an inhibitor of ribonucleotide reductase, an enzyme essential for DNA synthesis. Formation of dATP was completely prevented by iodotubercidin (ITu), a drug that inhibits phosphorylation of 2'-dAdo to dATP by nucleoside kinase. It is interesting that nanomolar concentrations of ITu also completely protected chromaffin cells from 2'-dAdo lethality. Our study demonstrates for the first time that mammalian adrenal chromaffin cells undergo apoptotic cell death by a natural nucleoside and suggests that this model could be used to study apoptosis and cell function.

Modulation of adenosine release from rat spinal cord by adenosine deaminase and adenosine kinase inhibitors

Adenosine, a modulator of pain processing in the spinal cord, is metabolized by adenosine kinase and adenosine deaminase. In this study we determined which of these mechanisms is more important for the regulation of endogenous adenosine levels in the rat spinal cord. The effects of the adenosine kinase inhibitors, 5′-deoxyadenosine (NH 2dAD) and iodotubercidin (IOT), and the adenosine deaminase inhibitor, 2′-deoxycoformycin (DCF), on adenosine release in a spinal cord superfusion model were studied. DCF markedly increased basal adenosine levels detected in perfusates and was more potent than NH 2dAD and IOT in this regard. Coadministration of DCF with NH 2dAD produced an enhanced effect compared to the inhibitors alone. NH 2dAD, but not DCF, potentiated morphine-evoked adenosine release. These results suggest that adenosine deaminase may be the predominant pathway for adenosine metabolism in this experimental model.

Treatment of Hairy Cell Leukemia in the Nineties

It is now more than a decade since the door was thrown open to medical treatment of hairy cell leukemia (HCL). Five out of 6 patients with the disease had responded to leukocyte interferon (α-IFN_leu). And throughout the years following, all new drugs developed for low-grade non-Hodgkin’s lymphomas (NHL) triggered excellent activity in this rare leukemia. The review describes the potential, dosage, and handling of the 3 new antileukemic drugs in HCL that emerged after the detection of the efficiency of the human natural α-IFN]_eu with its limited supply: the technically producible recombinant IFNs alpha-2a-c (rhIFN), deoxycoformycin (DCF), and 2-chlordeoxyadenosine (2-CdA). It then proceeds to familiarize the physician with the therapeutic use of the new nucleoside analogues and to recall the efficacy of IFN. The main sources of information are the reports which described the results of studies and investigations before approval in the USA and several nationwide trials from Europe. All in all, the antileukemic potential of the 3 drugs in treatment of HCL is nearly identical, extinguishing all other known prognostic factors. However, some patients still need individual approaches to problems which have evoled throughout the course of the disease. It then touches on the use of the growth factors, colony stimulating factors (CSF), in patients with severe neutropenia or active infections. Finally it reminds the reader that although the antileukemic effect of all 3 drugs seems practically guaranteed, he has a physician may be able to improve their benefit by a strictly problemoriented approach. Some patients ought to have preparative support, selected medication, a sequence or a combination of drugs.

Apoptosis induction with three nucleoside analogs on freshly isolated B-chronic lymphocytic leukemia cells.

The cytotoxic effects and the induction of programmed cell death (apoptosis) by Fludarabine (FLU), 2-chlorodeoxyadenosine (2-CdA), and deoxycoformycin (DCF) with/without alpha-interferon (alpha-IFN) were evaluated in vitro against freshly isolated B-chronic lymphocytic leukemia (B-CLL) cells. Cytotoxicity was evaluated according to the soluble tetrazolium/formazan assay. Regarding the cytotoxicity, FLU, 2-CdA, and DCF showed a mean antitumor activity of 45% +/- 3.39 (mean +/- S.D.), 55% +/- 4.72, and 20% +/- 3.16, respectively. alpha-IFN alone showed a mean cytotoxic activity of 10% +/- 2.72. The cytotoxicity of these purine analogues in combination with alpha-IFN was 52% +/- 2.97, 75% +/- 3.41, and 26% +/- 7.09, respectively. We observed a statistically significant increase of cytotoxicity compared to controls in FLU alone (P < 0.05), 2-CdA (P < 0.05), and their combination with alpha-IFN (P < 0.05). Apoptosis was evaluated by electrophoresis gel of DNA oligonucleosomal fragments and by a cytofluorimetric method. Only FLU and 2-CdA activated the apoptosis and DCF showed a minor apoptotic pathway amount. These apoptosis data were confirmed by both gel electrophoresis of DNA and by propidium iodide cytofluorimetric method. FLU and 2-CdA show activity in B-CLL cells by direct cytotoxic action and the induction of cell death by apoptosis; in the future, it would be interesting to utilize these in vitro assays in monitoring chemosensitivity and predicting response for the clinical use.

Adenosine deaminase inhibition is not cardioprotective in the rat

Adenosine receptor activation has been assumed to play a role in the cardioprotective effect of ischemic preconditioning. The actions of adenosine are terminated by the naturally occurring substance adenosine deaminase. We determined whether 2′-deoxycoformycin (DCF), a potent inhibitor of adenosine deaminase, could mimic the effect of preconditioning in nonpreconditioned rats and potentiate the salutary effect of preconditioning in preconditioned rats. We assessed the effect of DCF on myocardial infarct size and the incidence of ventricular arrhythmias in four groups of anesthetized rats: control (nonpreconditioned) + vehicle, control + DCF, preconditioned + vehicle, and preconditioned + DCF. All rats underwent 90 minutes of coronary artery occlusion followed by 4 hours of reperfusion, while preconditioned rats received three cycles of 3-minute episodes of ischemia and 5 minutes of reperfusion before the 90-minute occlusion. Following 4 hours of reperfusion, area at risk was determined by intravenous injection of blue dye during a brief coronary occlusion, and area of necrosis was determined by incubation of heart slices in triphenyltetrazolium chloride. In the nonpreconditioned control rats receiving vehicle, myocardial infarct size expressed as a percentage of the area at risk averaged 44.8 ± 7.6%. Pretreatment with DCF had no effect on infarct size (49.4 ± 4.9%) in the nonpreconditioned control rats. Both the preconditioned + vehicle (19.2 ± 7.8%) and the preconditioned + DCF (17.9 ± 5.1%) groups had a significant reduction in infarct size ( p < 0.05 versus control + vehicle and control + DCF), with no significant difference in infarct size between the two preconditioned groups. The incidence of ventricular tachycardia (VT) during the 90 minutes of ischemia was significantly attenuated in both preconditioned groups ( p < 0.05 versus controls). However, DCF caused no difference in the incidence of VT in either control animals or in preconditioned rats compared with vehicle. The incidence of ventricular fibrillation (VF) during ischemia was significantly higher in the control + DCF group (85.7%) versus the other three groups in which no VF occurred. Thus DCF, an inhibitor of adenosine deaminase, was not cardioprotective in this rat model of ischemia and reperfusion.

Complete Remissions in Hairy Cell Leukemia with 2-Chlorodeoxyadenosine after Failure with 2-Deoxycoformycin

To determine whether clinical cross-resistance and intolerance exists between the nucleosides 2'-deoxycoformycin (DCF) and 2-chlorodeoxyadenosine (2-CdA) in the treatment of patients with hairy cell leukemia despite similar structures and mechanisms of action. Phase II clinical study. Referral cancer center. Five patients with hairy cell leukemia who had been previously treated with DCF. Single course of 2-CdA at 0.1 mg/kg body weight per day for 7 days by continuous intravenous infusion. Of five patients, three were resistant to and two were intolerant of (having had life-threatening toxic reactions) DCF therapy. Four patients obtained a complete response with a median follow-up period of more than 11 months. The other patient in whom splenectomy, interferon, and DCF treatments were unsuccessful had a partial response lasting 2 months and subsequently died of Streptococcus pneumoniae bacteremia. Three of the four patients with complete responses remain in unmaintained remission, whereas the fourth has progressive splenic enlargement with stable hematologic parameters. The median leukocyte count increased from 2.0 x 10(9)/L to 3.8 x 10(9)/L, the median absolute neutrophil count increased from 0.56 x 10(9)/L to 2.73 x 10(9)/L, the median hemoglobin level increased from 112 g/L to 140 g/L, and the median platelet count increased from 55 x 10(9)/L to 123 x 10(9)/L. Two patients had culture-negative neutropenic fever associated with treatment. 2-Chlorodeoxyadenosine induced complete responses in patients with hairy cell leukemia resistant to DCF, suggesting a lack of cross-resistance. Also, 2-CdA is not prohibitively toxic in patients intolerant of DCF.

UK the second market for pentostatin

UK the second market for pentostatin

Failure of 2″-deoxycoformycin to protect against transient forebrain ischemia in rat

We determined whether 2′-deoxycoformycin (DCF), a potent highly specific inhibitor of adenosine deaminase (ADA), protected against transient forebrain ischemic neuronal injury in rat. Anesthetized male Sprague-Dawley rats received i.p. injections of either saline, 0.5 mg/kg or 5 mg/kg DCF 2 h before undergoing a 10-min forebrain ischemic insult induced by bilateral carotid artery occlusion with concomitant hypotension. Rat brain sections taken 7 days post-ischemia showed damage mostly in the CA1 region of the hippocampus. Quantification of neuronal injury showed no significant differences between saline- or DCF-treated rats. These results indicate that, contrary to previous reports, DCF does not protect against the neuronal damage that follows forebrain ischemia in rat.