A phase 1 trial of 8-chloro-adenosine in relapsed/refractory acute myeloid leukemia: An evaluation of safety and pharmacokinetics.

BACKGROUND: This study evaluated the safety, pharmacokinetics (PK), and pharmacodynamics (PD) of 8-chloro-adenosine (8-Cl-Ado) in patients with relapsed/refractory acute myeloid leukemia (AML). METHODS: 8-Cl-Ado was administered daily for 5 days; the starting dose was 100 mg/m2 , the highest dose tested was 800 mg/m2 . The end points were toxicity, disease response, and PK/PD measurements. RESULTS: The predominant nonhematologic toxicity was cardiac with grade ≥3 toxicity. Plasma PK in all patients suggested heterogeneity among patients, yet, some dose-dependency for the accumulation of 8-Cl-Ado. Two 8-Cl-Ado metabolites accumulated at similar levels to 8-Cl-Ado. Cellular PK in eight patients indicated accumulation of 8-Cl-ATP, which was associated with AML blast cytoreduction in peripheral blood. The authors determined the RP2D of 8-Cl-Ado to be 400 mg/m2 . CONCLUSIONS: Given the cardiac adverse events observed, patients require monitoring for arrhythmias and QT interval during infusion. Although peripheral blood cytoreduction was observed, responses were transient, suggesting combination strategies will be required.

Enhanced Vulnerability of LKB1-Deficient NSCLC to Disruption of ATP Pools and Redox Homeostasis by 8-Cl-Ado.

Loss-of-function somatic mutations of STK11, a tumor suppressor gene encoding LKB1 that contributes to the altered metabolic phenotype of cancer cells, is the second most common event in lung adenocarcinomas and often co-occurs with activating KRAS mutations. Tumor cells lacking LKB1 display an aggressive phenotype, with uncontrolled cell growth and higher energetic and redox stress due to its failure to balance ATP and NADPH levels in response to cellular stimulus. The identification of effective therapeutic regimens for patients with LKB1-deficient non-small cell lung cancer (NSCLC) remains a major clinical need. Here, we report that LKB1-deficient NSCLC tumor cells displayed reduced basal levels of ATP and to a lesser extent other nucleotides, and markedly enhanced sensitivity to 8-Cl-adenosine (8-Cl-Ado), an energy-depleting nucleoside analog. Treatment with 8-Cl-Ado depleted intracellular ATP levels, raised redox stress, and induced cell death leading to a compensatory suppression of mTOR signaling in LKB1-intact, but not LKB1-deficient, cells. Proteomic analysis revealed that the MAPK/MEK/ERK and PI3K/AKT pathways were activated in response to 8-Cl-Ado treatment and targeting these pathways enhanced the antitumor efficacy of 8-Cl-Ado. IMPLICATIONS: Together, our findings demonstrate that LKB1-deficient tumor cells are selectively sensitive to 8-Cl-Ado and suggest that therapeutic approaches targeting vulnerable energy stores combined with signaling pathway inhibitors merit further investigation for this patient population.

Targeting the metabolic vulnerability of acute myeloid leukemia blasts with a combination of venetoclax and 8-chloro-adenosine.

BACKGROUND: BCL-2 inhibition through venetoclax (VEN) targets acute myeloid leukemia (AML) blast cells and leukemic stem cells (LSCs). Although VEN-containing regimens yield 60-70% clinical response rates, the vast majority of patients inevitably suffer disease relapse, likely because of the persistence of drug-resistant LSCs. We previously reported preclinical activity of the ribonucleoside analog 8-chloro-adenosine (8-Cl-Ado) against AML blast cells and LSCs. Moreover, our ongoing phase I clinical trial of 8-Cl-Ado in patients with refractory/relapsed AML demonstrates encouraging clinical benefit. Of note, LSCs uniquely depend on amino acid-driven and/or fatty acid oxidation (FAO)-driven oxidative phosphorylation (OXPHOS) for survival. VEN inhibits OXPHOS in LSCs, which eventually may escape the antileukemic activity of this drug. FAO is activated in LSCs isolated from patients with relapsed AML. METHODS: Using AML cell lines and LSC-enriched blast cells from pre-treatment AML patients, we evaluated the effects of 8-Cl-Ado, VEN and the 8-Cl-Ado/VEN combination on fatty acid metabolism, glycolysis and OXPHOS using liquid scintillation counting, a Seahorse XF Analyzer and gene set enrichment analysis (GSEA). Western blotting was used to validate results from GSEA. HPLC was used to measure intracellular accumulation of 8-Cl-ATP, the cytotoxic metabolite of 8-Cl-Ado. To quantify drug synergy, we created combination index plots using CompuSyn software. The log-rank Kaplan-Meier survival test was used to compare the survival distributions of the different treatment groups in a xenograft mouse model of AML. RESULTS: We here report that VEN and 8-Cl-Ado synergistically inhibited in vitro growth of AML cells. Furthermore, immunodeficient mice engrafted with MV4-11-Luc AML cells and treated with the combination of VEN plus 8-Cl-Ado had a significantly longer survival than mice treated with either drugs alone (p ≤ 0.006). We show here that 8-Cl-Ado in the LSC-enriched population suppressed FAO by downregulating gene expression of proteins involved in this pathway and significantly inhibited the oxygen consumption rate (OCR), an indicator of OXPHOS. By combining 8-Cl-Ado with VEN, we observed complete inhibition of OCR, suggesting this drug combination cooperates in targeting OXPHOS and the metabolic homeostasis of AML cells. CONCLUSION: Taken together, the results suggest that 8-Cl-Ado enhances the antileukemic activity of VEN and that this combination represents a promising therapeutic regimen for treatment of AML.

Myasthenia gravis, an autoimmune manifestation of lymphoma and lymphoproliferative disorders: case reports and review of literature.

Myasthenia gravis (MG) is an autoimmune disease mediated by antibodies to acetylcholine receptors (AChRs) or muscle specific tyrosine kinase (MuSK). While the frequent association of MG with thymoma in patients aged 40-60 years is well recognized, its occurrence in patients with lymphoma has not been well studied. We review the literature on the association of MG and lymphoid malignancies and report two new patients. MG can occur in a synchronous or non-synchronous fashion with lymphoma. The pathogenesis of MG in lymphoid malignancies is probably heterogeneous and likely relates to perturbations in the immune mechanisms that normally prevent the emergence of autoimmunity. These perturbations could be the result of the lymphoid malignancy per se, or its treatment.

Hairy cell leukemia: evaluation of the long-term outcome in 121 patients.

BACKGROUND: Historically, the first treatment choices for hairy cell leukemia (HCL) were splenectomy and alpha-interferon. Recently, purine analogues (pentostatin and cladribine) changed radically the treatment modality, inducing complete and durable responses in the majority of patients. METHODS: The authors analyzed the outcome of different lines of therapy in 121 HCL patients followed in their institute from 1986 to 2008, with a median follow-up of 105 months. Patients were divided into subgroups according to the number of treatments; Group A included 121 patients who underwent a front-line therapy, Group B patients (n =53) were treated with 2 lines, Group C patients (n = 34) with 3 lines, Group D patients (n = 17) with 4 lines, and Group E patients (n = 8) with 5 lines. RESULTS: In Group A, 92 (77%) patients obtained a complete response (CR), 23 (18%) a partial response, and the remaining 6 (5%) a minor or no response; median duration of response was 2.7 years. In Group B, 53 relapsed patients achieved a second CR rate of 73.5%; median duration of response was 2.5 years. Group C contained 34 patients in a second relapse, with a CR rate after the third line of treatment of 70.5% (median duration of response, 2.2 years). In Group D, 11 (64.7%) patients obtained a CR (median duration of response, 1.6 years), and in Group E 4 (50%) of 8 patients achieved a CR (median duration of response, 1.3 years). CONCLUSIONS: This study confirms the high risk (>40% of all patients) of retreatment of HCL patients and the need to maximize primary response.

2-Chloroadenosine (2-CADO) treatment modulates the pro-inflammatory immune response to prevent acute lung inflammation in BALB/c mice suffering from Klebsiella pneumoniae B5055-induced pneumonia.

Acute lung inflammation (ALI) is a life-threatening pathology and can develop during the course of several clinical conditions such as pneumonia, acid aspiration or sepsis. Adenosine plays a significant role in controlling acute inflammation via binding to A(2A) receptors on inflammatory cells, i.e. neutrophils or macrophages. The present study was designed to evaluate the anti-inflammatory and immunomodulatory effects of 2-chloroadenosine (2-CADO), alone or in combination with amoxicillin/clavulanic acid (AMC), in Klebsiella pneumoniae B5055-induced acute lung infection in mice. Acute lung infection in mice was induced by directly instilling the selected dose (10(4) colony-forming units/mL) of bacteria intranasally. Histopathological examination of the lungs was performed to reveal neutrophil infiltration into the lung alveoli. In addition to the major pro-inflammatory cytokines tumour necrosis factor-alpha (TNFalpha) and interleukin (IL)-1alpha, levels of the anti-inflammatory cytokine IL-10 were also determined. Intranasal instillation of bacteria caused profound neutrophil infiltration into the lung alveoli as well as a significant increase in the levels of pro-inflammatory mediators (i.e. TNFalpha and IL-1alpha). However, intravenous administration of 2-CADO 10 microg/kg/day, alone or in combination with an antibiotic (i.e. AMC), significantly decreased neutrophil infiltration into the lung alveoli. A significant decrease in TNFalpha and IL-1alpha along with elevation of IL-10 levels in the lung homogenate of mice with acute lung infection was observed upon treatment with 2-CADO alone, with no significant decrease in bacterial counts. Moreover, in combination with AMC, 2-CADO exhibited its immunomodulatory action in acute lung infection and prevented ALI, whilst an antibacterial action was exhibited by AMC.

2'-Chlorodeoxyadenosine (2-CdA) as salvage therapy for Langerhans cell histiocytosis (LCH). results of the LCH-S-98 protocol of the Histiocyte Society.

BACKGROUND: A prospective phase II Histiocyte Society study, LCH-S-98, evaluated the efficacy of 2-chlorodeoxyadenosine (2-CdA) monotherapy as salvage therapy in Langerhans cell histiocytosis (LCH). PROCEDURES: Patients with poor and intermediate risk LCH not responsive to initial therapy and patients with low-risk chronic recurrent LCH were evaluated for response and survival after treatment with 2-6 courses of 2-CdA. RESULTS: Forty-six patients (55%) had involvement of risk organs; lung, liver, spleen, or hematopoetic system (RO+), 37 (45%) were RO-. Twenty-two percent of RO+ patients had a good response while 44% progressed, 62% RO- patients responded, and 11% progressed. Two-year predicted survival is 48% for RO+, 97% for RO- patients, 100% for RO+ patients reactivating in non-risk organs, 67% for RO- patients reactivating in risk organs. Two-year pSU for the entire group is 68%. Seventy-three percent of patients with a poor response to 2-CdA died. Sixty-five percent patients >2 years old and 30% <2 years old survived. There was a median of 26 months from diagnosis to 2-CdA for responders compared to a median of 5 months for non-responders. Twenty-one percent of patients treated <12 months and 57% treated >12 months from diagnosis responded. CONCLUSION: 2-CdA is active in LCH. It produces a higher response rate in patients with low-risk multisystem or multifocal bone disease than those with risk organ involvement. "Risk" patients who fail to respond to 2-CdA have a high mortality. Patient age at 2-CdA therapy and length of time from diagnosis to 2-CdA significantly affect response and survival.

Extranodal multifocal Rosai-Dorfman disease: response to 2-chlorodeoxyadenosine treatment.

Rosai-Dorfman disease (RDD) or "sinus histiocytosis with massive lymphadenopathy" is a rare lymphoproliferative disorder of unknown etiology. The disease usually presents with painless lymphadenopathy with occasional extranodal involvement in various organs. We report a case of a 36-year-old man with a history of non-Hodgkin lymphoma (NHL), who recently presented with inguinal lymphadenopathy. Following the diagnosis of RDD on lymph node biopsy, he developed symptoms of spinal cord compression due to a mass lesion discovered at T6-7 vertebral level. 18F-Fluorodeoxyglucose (18FDG) positron emission tomography (PET-CT) revealed extensive disease with lung, renal and bone involvement. The patient received a short course of steroid therapy for cord compression findings and 2-chlorodeoxyadenosine (2-CdA) treatment was initiated for long-term disease control. He had a dramatic sustained response to treatment with six courses of 2-CdA. These results suggest that 2-CdA can be an effective treatment of choice and positron emission tomography with 18FDG can be used for determining the extent of disease and for follow-up in RDD.

2-Chloroadenosine and human prostate cancer cells.

Cladribine, i.e.2-deoxy-Chloroadenosine is currently in use as chemotherapeutic agent in chronic lymphoid malignancies and pediatric acute myelogenous leukemia whereas the structurally related counterpart, 2-Chloroadenosine, has been less studied. Nevertheless, 2-Chloroadenosine has been shown to be capable of inducing apoptosis in several cell lines by acting either via adenosine receptors or via uptake that is followed by metabolic transformations leading to nucleotide analogues, i.e. antimetabolites effective in the treatment of a variety of malignancies. Triphosphate nucleoside analogues show specificity for cell in S-phase, inhibit DNA synthesis and kill the cells by mechanisms still largely unknown. 2-Chloroadenosine, at low micromolar concentration, acts as a metabolic precursor of an S-phase specific nucleoside analogue in human prostate cancer PC3 cells and inhibits DNA synthesis thereby leading to accumulation of cells in the S-phase. However, although responsible for the acquisition of resistance, the adenosine derivative is capable of sensitising the cells to the action of other antineoplastic agents and the ability of nucleoside analogues to trigger cell cycle arrest can be exploited to maximize cytotoxicity in combination with cell cycle checkpoint disregulators. 2-Chloroadenosine, in combination with Docetaxel, known to improve the survival of hormone-refractory prostate cancer patients, further decreases in vitro PC3 cell proliferation and invasiveness. Moreover, 2-Chloroadenosine is capable of modulating PAR-1 and IL-23 gene expression suggesting a modulation of cancer metastasis and immune system activity. The present review summarizes research performed in our laboratory to propose a novel role for 2-Chloroadenosine as an anticancer agent.

Mechanisms of cell death induced by 2-chloroadenosine in leukemic B-cells.

2-chloroadenosine (2-CAdo) is an adenosine deaminase-resistant analogue of adenosine, widely used as an adenosine receptor agonist. This compound has been shown to induce apoptosis in several cell types either via activation of adenosine receptors or via intracellular metabolism. However, the molecular mechanisms of 2-CAdo-induced apoptosis are unclear. Here, we analyzed the effects of 2-CAdo in the leukemia cell line EHEB. 2-CAdo was found to induce apoptosis in EHEB cells, as shown by caspase-3 activation, DNA fragmentation, poly(ADP-ribose) polymerase (PARP) cleavage and phosphatidylserine exposure. Cytotoxicity of 2-CAdo was completely suppressed by 5-iodotubercidin, an adenosine kinase inhibitor, indicating that apoptosis induced by 2-CAdo was the result of its intracellular metabolism. Accordingly, we found that 2-CAdo was efficiently converted into 2-chloroATP. In parallel, a decrease of intracellular ATP concentration as well as a general inhibition of macromolecular synthesis, involving DNA, RNA and protein synthesis, was observed. Moreover, 2-CAdo induced cytochrome c release into the cytosol, indicating activation of the intrinsic pathway of apoptosis. This was found associated with a decline in Mcl-1 protein level and p53-independent. Inhibition of AMP deaminase by coformycin markedly prevented ATP depletion, and also significantly reduced 2-CAdo cytotoxicity and caspase-3 activation. In conclusion, our data show that intracellular metabolism of 2-CAdo can lead to activation of the intrinsic pathway of apoptosis and that ATP depletion, in addition to the accumulation of the triphosphate analogue, contributes to 2-CAdo-induced apoptosis.

Activity and toxicity of 2-CDA in Langerhans cell histiocytosis: a single institutional experience.

BACKGROUND: Langerhans cell histiocytosis (LCH) is a rare disorder characterized by clonal proliferation of immature and abnormal bone marrow derived langerhans cells. Treatment is usually multimodal. Potent anti-monocyte as well as immunomodulatory activity of 2-CDA and its proven efficacy in many lymphoproliferative disorders has made 2-CDA a rational choice in treatment of LCH. AIM: To evaluate the efficacy and toxicity profile of 2-CDA in children with relapsed or refractory LCH. SETTING AND DESIGN: This is a pilot study and we present the initial data of the first seven patients treated at our institution. MATERIALS AND METHODS: Seven patients of relapsed and refractory LCH were enrolled from July 2000 to June 2004. The cohort of seven patients included six males and one female with a median age at initiation of cladribine was 2.25 years (range, 1.67 to 7.0 years). Three patients had received one prior chemotherapy regimen while the rest were heavily pretreated. Cladribine was administered over two hours IV daily for five days and repeated every four weeks. RESULTS: After a median of six courses of cladribine (range, 2 to 9), two (33%) patients achieved PR and two (33%) patients have SD on imaging but are clinically better. None experienced grade 3 or 4 hematologic toxicity. At a median follow-up of 19 months (range, 8 to 52 months), five patients remain alive and one patient has died. CONCLUSION: Our study shows that single agent 2-CDA is active and well-tolerated in children with relapsed or refractory LCH.

Long-term stimulation of adenosine A2b receptors begun after myocardial infarction prevents cardiac remodeling in rats.

BACKGROUND: Adenosine inhibits proliferation of cardiac fibroblasts and hypertrophy of cardiomyocytes, both of which may play crucial roles in cardiac remodeling. In the present study, we investigated whether chronic stimulation of adenosine receptors begun after myocardial infarction (MI) prevents cardiac remodeling. METHODS AND RESULTS: MI was produced in Wistar rats by permanent ligation of the left anterior descending coronary artery. One week after the onset of MI, animals were randomized into 8 groups: vehicle, dipyridamole (DIP; the adenosine uptake inhibitor, 50 mg/kg), 2-chroloadenosine (CADO; the stable analogue of adenosine, 2 mg/kg), and CADO in the presence of the nonselective adenosine receptor antagonist 8-sulfophenyltheophylline (8-SPT) or the selective antagonist for adenosine A1, A2a, A2b, or A3 receptor. Three weeks after treatment, hemodynamic and echocardiographic parameters in the DIP and CADO groups were significantly improved compared with the vehicle group. These hemodynamic and echocardiographic improvements were blunted by either 8-SPT or the selective adenosine A2b antagonist MRS1754 but not by the selective antagonists for other subtypes of adenosine receptors. The collagen volume fraction was smaller, and gene expression of the molecules associated with cardiac remodeling such as matrix metalloproteinase in noninfarcted areas was reduced in the DIP and CADO groups compared with the vehicle group, both of which were attenuated by either 8-SPT or MRS1754. CONCLUSIONS: Long-term stimulation of adenosine A2b receptors begun after MI attenuates cardiac fibrosis in the noninfarcted myocardium and improves cardiac function. Drugs that stimulate adenosine A2b receptors or increase adenosine levels are new candidates for preventing cardiac remodeling after MI.

Suppression of generalized seizures activity by intrathalamic 2-chloroadenosine application.

In the present study, we investigated the effects of micro-injecting 2-chloroadenosine (2-CADO; an adenosine receptor agonist) into the thalamus alone and with theophylline (a nonspecific adenosine receptor antagonist) pretreatment on pentylenetetrazol (PTZ)-induced tonic-clonic seizures in male Wistar albino rats. Following intrathalamic 2-CADO injection alone or theophylline pretreatment, 50 mg kg(-1) PTZ was given ip after 1 and 24 hrs. The duration of epileptic seizure activity was recorded by cortical electroencephalogram (EEG), and seizure severity was behaviorally scored. Intrathalamic 2-CADO administration induced significant decreases in both seizure duration and seizure severity scores at 1 and 24 hrs, but the effects were more abundant on the seizures induced after 24 hrs. On the other hand, pretreatment with theophylline prevented the inhibitor effect of 2-CADO on seizure activity and increased both seizure duration and seizure scores. Present results suggest that the activation of adenosine receptors in the thalamus may represent another anticonvulsant/modulatory site of adenosine action during the course of the PTZ-induced generalized tonic-clonic seizures and provide additional data for the involvement of the adenosinergic system in the generalized seizures model.

Activation of adenosine A1 receptor attenuates cardiac hypertrophy and prevents heart failure in murine left ventricular pressure-overload model.

Sympathomimetic stimulation, angiotensin II, or endothelin-1 is considered to be an essential stimulus mediating ventricular hypertrophy. Adenosine is known to protect the heart from excessive catecholamine exposure, reduce production of endothelin-1, and attenuate the activation of the renin-angiotensin system. These findings suggest that adenosine may also attenuate myocardial hypertrophy. To verify this hypothesis, we examined whether activation of adenosine receptors can attenuate cardiac hypertrophy and reduce the risk of heart failure. Our in vitro study of neonatal rat cardiomyocytes showed that 2-chloroadenosine (CADO), a stable adenosine analogue, inhibits protein synthesis of cardiomyocytes induced by phenylephrine, endothelin-1, angiotensin II, or isoproterenol, which were mimicked by the stimulation of adenosine A1 receptors. For our in vivo study, cardiac hypertrophy was induced by transverse aortic constriction (TAC) in C57BL/6 male mice. Four weeks after TAC, both heart to body weight ratio (6.80+/-0.18 versus 8.34+/-0.33 mg/g, P<0.0001) as well as lung to body weight ratio (6.23+/-0.27 versus 10.03+/-0.85 mg/g, P<0.0001) became significantly lower in CADO-treated mice than in the TAC group. Left ventricular fractional shortening and left ventricular dP/dtmax were improved significantly by CADO treatment. Similar results were obtained using the selective adenosine A1 agonist N6-cyclopentyladenosine (CPA). A nonselective adenosine antagonist, 8-(p-sulfophenyl)-theophylline, and a selective adenosine A1 antagonist, 8-cyclopentyl-1,3-dipropylxanthine, eliminated the antihypertrophic effect of CADO and CPA, respectively. The plasma norepinephrine level was decreased and myocardial expression of regulator of G protein signaling 4 was upregulated in CADO-treated mice. These results indicate that the stimulation of adenosine receptors attenuates both the cardiac hypertrophy and myocardial dysfunction via adenosine A1 receptor-mediated mechanisms.

Low dose 2-CdA schedule activity in splenic marginal zone lymphomas.

Splenic Marginal Zone Lymphoma (SMZL) is a rare clinicopathological entity among marginal zone lymphomas. SMZL is an indolent lymphoma usually treated by splenectomy. A subset of patients is characterized by a more aggressive clinical course and poor prognosis. Treatment of these cases and second-line therapy for relapsed patients have not been yet identified. We report 10 cases treated with cladribrine (5 mg/m(2)/week) for six courses. Six patients (60%) achieved partial response, two patients (20%) achieved a complete response and the two remaining patients did not respond and died as a result of progression of the disease. The treatment was well tolerated. A total of 60% of the patients had an overall survival rate of 48 months and 24 months progression-free-survival was achieved by 37% with a median time of progression-free-survival of 17 months. Interestingly, in addition to a relevant percentage of hematological remission, some patients also experienced a molecular remission. We conclude that this treatment is safe and well tolerated and is able to induce a substantial number of responses. Our results suggest that this schedule is well tolerated and could be an useful alternative to splenectomy.

Administration of adenosine receptor agonists or antagonists after controlled cortical impact in mice: effects on function and histopathology.

Adenosine is an endogenous neuroprotectant via anti-excitotoxic effects at A(1) receptors, and blood flow promoting and anti-inflammatory effects at A(2a) receptors. Previous studies showed improved motor function after fluid percussion injury (FPI) in rats treated with the broad-spectrum adenosine receptor agonist 2-chloroadenosine (2-CA). We studied the effects of 2-CA, a specific A(1) agonist (2-chloro-N(6)-cyclopentyladenosine, CCPA), and a specific A(1) antagonist (8-cyclopentyl-1,3-dipropylxanthine, DPCPX) on motor task and Morris water maze (MWM) performance, and histopathology (contusion volume, hippocampal cell counts) after controlled cortical impact (CCI) in mice. Each agent (12 nmol), or respective vehicle (saline or DMSO) was injected into dorsal hippocampus beneath the contusion immediately after CCI or craniotomy (sham). 2-CA treatment attenuated wire grip deficits after CCI (P<0.05 versus other treatments). DPCPX treatment exacerbated deficits on beam balance (P<0.05 versus sham). No treatment effect was seen on MWM performance, although there was a deleterious effect of the DMSO vehicle used for DPCPX. Contusion volume tended to be attenuated by 2-CA (P=0.08 versus saline) and increased after either DMSO or DPCPX (P<0.05 versus all groups). CA1 and CA3 counts were decreased in all groups versus sham. However, treatment with the selective A(1) agonist CCPA attenuated the CA3 cell loss (P<0.05 versus other treatment). We suggest that the beneficial effect of the broad spectrum adenosine receptor agonist 2-CA on motor function after CCI is not mediated solely by effects at the A(1) receptor.

Aggressive growth of epithelial carcinomas following treatment with nucleoside analogues.

Two patients, one with B-cell chronic lymphocytic leukemia (CLL) and one with hairy-cell leukemia (HCL), were treated with immunosuppressive chemotherapy. The patient with CLL was a 54-year-old female, who had had a squamous cell carcinoma (SCC) excised from her forehead 5 months before receiving the first course of fludarabine. During the fludarabine treatment, the patient developed a local SCC relapse and metastases in the neck. The carcinoma was treated by excision and radiotherapy, and further fludarabine treatment was withheld. Nevertheless, the SCC metastasized aggressively and the patient died 3 months after the start of fludarabine treatment, primarily due to respiratory failure. The autopsy revealed heavy SCC infiltrations involving the lungs, pleura, mediastinum, pericardium, and liver. The patient with HCL was a 69-year-old male. At the time of diagnosis of HCL, the patient had two solid tumors in the liver containing poorly differentiated epithelial carcinoma cells of unknown origin. During treatment with 2-chlorodeoxyadenosine (2CdA), the tumors in the liver rapidly spread in multiple intrahepatic metastases, followed by liver failure and death within 1 month. Fludarabine and 2CdA cause a substantial suppression of all lymphocyte subsets, in particular the T-cell line. T-lymphocytes are believed to be responsible for the usually slow growth and the low metastatic rate of the SCC skin lesions. It is therefore assumed that fludarabine and 2CdA in these two cases triggered an exacerbation of both tumors due to the T-cell depletion.

2-Chloroadenosine, a preferential agonist of adenosine A1 receptors, enhances the anticonvulsant activity of carbamazepine and clonazepam in mice.

2-Chloroadenosine (0.25-1 mg/kg) significantly raised the threshold for electroconvulsions in mice. This preferential adenosine A(1) receptor agonist (at 0.125 mg/kg) significantly potentiated the protective activity of carbamazepine against maximal electroshock-induced seizures in mice. 2-Chloroadenosine (1 mg/kg) showed also anticonvulsive efficacy against pentylenetetrazol-evoked seizures, raising the CD(50) value for pentylenetetrazol from 77.2 to 93.7 mg/kg. The drug (at 0.5 mg/kg) significantly enhanced the protective action of clonazepam in this test, decreasing its ED(50) value from 0.033 to 0.011 mg/kg. Moreover, aminophylline, a non-selective adenosine receptor antagonist (5 mg/kg), and 8-cyclopentyl-1,3-dimethylxanthine (8-CPX), a selective A(1) adenosine receptor antagonist (5 mg/kg) reversed the 2-chloroadenosine (0.125 mg/kg)-induced enhancement of the protective activity of carbamazepine and clonazepam. 2-Chloroadenosine administered alone or combined with antiepileptic drugs, caused neither motor nor long-term memory impairment. Finally, the adenosine A(1) agonist did not change the free plasma concentration of antiepileptics, so a pharmacokinetic factor is not probable. Summing up, 2-chloroadenosine potentiated the protective activity of both carbamazepine and clonazepam, which seems to be associated with the enhancement of purinergic transmission mediated through adenosine A(1) receptors.