A phase I/II study of continuous infusion suramin in patients with hormone-refractory prostate cancer : toxicity and response

 Introduction: Suramin is a synthetic polysulfonated naphthylurea which has been used for the treatment of African trypanosomiasis and onchocerciasis, but since the mid-1980s has received attention as a possible antiretroviral and antineoplastic agent. Objective: This clinical trial of suramin was undertaken as a phase I/II study in patients with hormone-refractory prostate cancer, with the hypothesis that the intensity of therapy with suramin could be increased significantly if measures were undertaken to maintain the plasma concentrations of the drug under 300 μg/ml. Methods: We report the clinical results of this trial, wherein patients were treated at three different targeted plasma suramin concentrations (275, 215 and 175 μg/ml) for varying periods of time (2, 4 or 8 weeks), with delivery of the drug by continuous intravenous infusion. Results: The major toxicity observed in this trial was neurologic, consisting of a motor and sensory peripheral neuropathy that resulted in both paresis and paralysis of the limbs. Nearly all of this severe (CTEP grade III, IV) neurologic toxicity was observed in the patients treated at a plasma suramin concentration of 275 μg/ml for 4 or more weeks. A single patient treated at 215 μg/ml for 8 weeks developed moderate (CTEP grade III) proximal lower extremity weakness, and no patient treated at 175 μg/ml developed this toxicity. The second most common toxicity observed was infection of the central venous catheter. The overall response rate for all of the evaluable patients was 17% (13 of 75 patients). In addition, prostate-specific antigen (PSA)-defined responses were observed in six patients receiving therapy at 175 μg/ml, but these responses were confounded by cessation of therapy with flutamide during suramin treatment. Conclusions: In summary, although plasma suramin concentrations were maintained below 300 μg/ml, neurologic toxicity nonetheless occurred with high frequency in patients treated at 275 μg/ml for 4 or more weeks. Therapy at 215 and 175 μg/ml was in general well tolerated, but central venous catheter-related infection, as well as the inconvenience and expense of continuous infusional therapy, make this method of drug delivery impractical. Only moderate antitumor activity was observed during this trial, but it is possible that both continuation of flutamide and flutamide withdrawal during suramin therapy confounded the assessment of suramin’s activity in hormone-refractory prostate cancer. Received: 9 June 1995/Accepted: 18 March 1996     

Effects of adenosine 5’-triphosphate, uridine 5’-triphosphate, adenosine 5’-tetraphosphate and diadenosine polyphosphates in guinea-pig taenia caeci and rat colon muscularis mucosae

The functional effects of adenosine 5’-triphosphate (ATP), uridine 5’-triphosphate (UTP), adenosine 5’-tetraphosphate (AP₄) and the diadenosine polyphosphates P₁,P₃-diadenosine triphosphate (Ap₃A), P₁,P₄-diadenosine tetraphosphate (Ap₄A) and P₁,P₅-diadenosine pentaphosphate (Ap₅A) were studied in two isolated smooth muscle preparations thought to contain P_2Y (P2Y₁) receptors, the guinea-pig taenia caeci (which relaxes to ATP) and the rat colon muscularis mucosae (which contracts to ATP). In addition, the breakdown of these compounds by the rat colon muscularis mucosae was investigated by high pressure liquid chromatography. In the guinea-pig taenia caeci all the purine nucleotides caused relaxation with a potency order of Ap₃A=Ap₄A> ATP>AP₄=Ap₅A, and these relaxations were antagonised by suramin with apparent pA₂ values in the region of 5, consistent with activation of a P2Y₁ receptor. In the rat colon muscularis mucosae the nucleotides caused contraction with a potency order of Ap₃A = Ap₄A>ATP=AP₄ =Ap₅A >UTP. However, while suramin (100 μM) inhibited responses to ATP and UTP at all concentrations of agonist, it only inhibited contractions induced by the higher concentrations of AP₄, Ap₃A and Ap₄A and had little effect on contractions induced by Ap₅A. A higher concentration of suramin (1 mM) enhanced contractions induced by ATP but greatly inhibited those induced by UTP and had no effect on responses to the other agonists. The A₁ adenosine receptor antagonist 1,3-dipropyl-8-cyclopentylxanthine (DPCPX; 10 nM) had no effect on responses to ATP or UTP but inhibited responses to Ap₃A, Ap₄A, Ap₅A and AP₄. A combination of suramin (1 mM) and DPCPX (10 nM) almost abolished responses to all the agonists. ATP and UTP were rapidly degraded by the rat colon muscularis mucosae while AP₄, Ap₃A, Ap₄A and Ap₅A were degraded more slowly, and the major product detected after breakdown of the purine nucleotides was inosine rather than adenosine. The breakdown of all the nucleotides was inhibited by suramin (1 mM), although this inhibition did not achieve statistical significance in the case of ATP. These results show that while the diadenosine polyphosphates appear to act as P2 agonists in the taenia caeci, in the rat colon muscularis mucosae their major action is via adenosine A₁ receptors rather than via P2 receptors. In addition, although they are more stable than ATP or UTP, their action in this tissue is clearly affected by their degradation which complicates the effects of suramin. Received: 23 March 1998 / Accepted: 29 June 1998     

Acidic ATP activates lymphocyte outwardly rectifying chloride channels via a novel pathway

Using whole-cell patch-clamp techniques we found that ATP activated an outwardly rectifying current in Daudi human B lymphoma cells under acidic conditions. The substitution of Cl^– for gluconate^– shifted the reversal potential, while Cl^– channel blockers, 4,4-diisothiocyanostibene-2,2-disulfonic acid (DIDS) and 9-anthracene carboxylic acid (9-AC), blocked the current, indicating that ATP induces this current by activating the outwardly rectifying chloride channel (ORCC). The effect of ATP on ORCC was mimicked by ADP, but not by other P2 receptor agonists such as ATPS (a poorly hydrolyzable analog of ATP), 2,3-O-benzoyl-4-benzoyl-ATP (BzATP), and UTP. The ATP-induced ORCC current was completely blocked by 100 M suramin (a P2 receptor antagonist), and was partially blocked by 100 M pyridoxal-phosphate-6-azophenyl-2,4-disulfonic acid tetrasodium (PPADS), which is another P2 receptor antagonist. Neither inactivation of G proteins nor elimination of extracellular Ca²⁺ affected the ATP-induced current, indicating that G protein-coupled P2Y receptors and Ca²⁺-permeable P2X receptors are not involved. Based on the pharmacological profile and the fact that acidic conditions are required for ATP to activate the ORCC, we suggest that acidic ATP activates the lymphocyte ORCC via a novel pathway, which is not associated with any previously described purinergic receptors.     

Cultured chick sympathetic neurons: ATP-induced noradrenaline release and its blockade by nicotinic receptor antagonists

The ATP-induced increase in tritium outflow from cultured chick sympathetic neurons prelabelled with [³H]-noradrenaline was investigated.Seven days-old dissociated cell cultures of embryonic paravertebral ganglia, loaded with [³H]-noradrenaline (0.05 M), were superfused in the presence of (+)-oxaprotiline and exposed to ATP, ATP-analogues, or 1,1-dimethyl-4-piperazinium (DMPP) for 2 min. ATP (3 LM-3 mM), 2-methylthio-ATP (3–100 M), as well as DMPP (10 and 100 M) induced a significant overflow of tritium. The EC₅₀-value of ATP was 20 M. Both the ATP-induced and the DMPP-induced tritium overflow was Ca²⁺-dependent and sensitive to tetrodotoxin (0.3 M) and -conotoxin (0.1 M); in addition, it was inhibited by the ₂-adrenoceptor agonist 5-bromo-6-(2-imidazoline-2-ylamino)-quinoxaline (UK-14,304; 1 M). The effects of ATP and DMPP were not additive. The ATP-induced as well as the DMPP-induced overflow of tritium was diminished by the P₂-purinoceptor antagonists suramin (300 M) and reactive blue 2 (3 M); in all 4 cases, the inhibition amouted to approximately 40%. The tritium overflow induced by ATP or DMPP was almost abolished by the nicotinic receptor antagonist mecamylamine (10 M) and markedly inhibited by hexamethonium (100 M). Neither ATP nor electrical stimulation caused an overflow of tritium from cultures loaded with [³H]-choline.The results suggest that ATP at molar concentrations induces noradrenaline release from cultured chick sympathetic neurons via an action on a subclass of the nicotinic cholinoceptor.     

Concomitant blockade of P2X-receptors and ecto-nucleotidases by P2-receptor antagonists: functional consequences in rat vas deferens

In order to assess the consequences of a concomitant blockade of P2X-receptors and ecto-nucleotidases, effects of 13 P2-receptor antagonists were investigated on contractions of the rat vas deferens elicited by α,β-methylene ATP (α,β-MeATP) and ATP and on the removal of ATP from the incubation medium by vas deferens tissue. Increasing concentrations of all antagonists reduced and finally abolished contractions elicited by α,β-MeATP (3 μM), with IC₅₀-values ranging from 1.1 to 100 μM. Pyridoxalphosphate-6-azophenyl-2’,4’-disulphonate (PPADS), 6-azophenyl-4-amino-5-hydroxy-naphthalene-1,3-disulphonate (NH02), 4,4’-diisothiocyanatostilbene-2,2’-disulphonate (DIDS) and uniblue A also progressively reduced and finally abolished contractions elicited by ATP (1 mM). 8,8’-[Carbonylbis(imino-3,1-phenylenecarbonyl-imino)]-bis-(1,3,5-naphthalenetrisulphonate) (NF023), sura- min, pyridoxalphosphate-6-azophenyl-2’,5’-disulphonate (iso-PPADS), trypan blue and reactive blue 19, in contrast, caused only partial blockade, by 34–43% maximally; reactive blue 2 and reactive red 2 had no effect; and 6,6’-(1,1’-biphenyl-4,4’-diylbisazo)-bis-4-amino-5-hydroxy-naphtha-lene-1,3-disulphonate (NH01) and Evans blue even enhan- ced the response to ATP. For antagonists causing full or partial inhibition, the IC₅₀-values against ATP were close to those against α,β-MeATP. All antagonists attenuated the removal of ATP, with IC_25%-values ranging from 0.8 μM to >320 μM. The results confirm the frequent combination, in one antagonist molecule, of P2-receptor blockade and blockade of ecto-nucleotidases. This dual action underlies the effect of such compounds on contractions of the vas deferens elicited by ATP which, for certain substances (e.g., suramin, reactive blue 2), can be explained by a simple model in which the antagonist simultaneously blocks the degradation of ATP and a single contraction-mediating receptor (P2X₁). Several observations, however, do not conform with this model, and the existence of multiple contraction-mediating receptors for ATP or multiple, pharmacologically distinct ecto-nucleotidases has to be considered. Received: 23 October 1998 / Accepted: 11 January 1999     

苏拉明联合阿霉素对肺腺癌小鼠移植瘤组织中HIF-1α和VEGF表达的调控及意义

目的研究苏拉明联合阿霉素对肺腺癌小鼠移植瘤组织中缺氧诱导因子-1α(H IF-1α)和血管内皮细胞生长因子(VEGF)表达的调控及对移植瘤增殖的影响。方法复制肺腺癌LA795细胞的T739小鼠异体移植瘤模型。40只实验小鼠皮下移植处均成瘤,接种后4d随机分为4组,10只/组。对照组:生理盐水0.2 m l/只,于接种后第4天开始腹腔注射,1次/d,共16次;阿霉素组:阿霉素(2 mg.kg-1.d-1)溶于0.2 m l生理盐水中,于接种后第4,11,18天各腹腔注射1次;苏拉明组:苏拉明(10 mg.kg-1.d-1)溶于0.2 m l生理盐水中,余同对照组;联合组(阿霉素 苏拉明):按阿霉素组和苏拉明组用药。肿瘤接种后24 d,测量小鼠皮下肿瘤最大长径(a)和横径(b),计算肿瘤体积;处死后剥离皮下肿瘤称湿重,收集肿瘤标本固定,用免疫组化和图像分析系统定量检测肿瘤组织H IF-1α、VEGF、微血管密度(MVD)和增殖细胞核抗原(PCNA)的表达。结果各治疗组肿瘤体积和湿重均低于对照组,其中以联合组最低,差异有统计学意义。苏拉明组和联合组:肿瘤组织中H IF-1α和VEGF的灰度值均高于对照组,MVD的灰度值和PCNA增殖指数均低于对照组;H IF-1α和VEGF的灰度值以联合组最高,MVD和PCNA增殖指数以联合组最低,差异有统计学意义。阿霉素组:H IF-1α和VEGF的灰度值均高于对照组,但差异无统计学意义;低于联合组,差异有统计学意义;MVD低于对照组,但差异无统计学意义;高于联合组,差异有统计学意义;而PCNA增殖指数低于对照组,高于联合组,差异有统计学意义;各组间H IF-1α和VEGF的灰度值与MVD和PCNA增殖指数呈反向变化,直线相关分析显示均呈负相关。结论阿霉素可能协同苏拉明通过抑制H IF-1α和VEGF的表达,从而抑制肿瘤组织新生血管形成和肿瘤细胞增殖。     

Chemotherapy-induced peripheral neuropathy

The induction of peripheral neuropathy is a common factor in limiting therapy with chemotherapeutic drugs. Little is known about the mechanisms responsible for the development of neuropathy. Depending on the substance used, a pure sensory and painful neuropathy (with cisplatin, oxaliplatin, carboplatin) or a mixed sensorimotor neuropathy with or without involvement of the autonomic nervous system (with vincristine, taxol, suramin) can ensue. Neurotoxicity depends on the total cumulative dose and the type of drug used. In individual cases neuropathy can evolve even after a single drug application. A general predisposition for developing a chemotherapy-induced neuropathy has been observed in nerves previously damaged by diabetes mellitus, alcohol or inherited neuropathy. The recovery from symptoms is often incomplete and a long period of regeneration is required to restore function. Up to now, no drug is available to reliably prevent or cure chemotherapy-induced neuropathy. Received: 15 November 2000, Received in revised form: 12 April 2001, Accepted: 19 April 2001     

Efficacy of suramin against human prostate carcinoma DU145 xenografts in nude mice

Purpose: Toward developing a model to study the mechanism of action of suramin against prostate cancer, we identified the effect of suramin on the growth of xenografts of the androgen-independent human prostate carcinoma DU145 cell line and our subline of suramin-resistant (SR) DU145 cells which are less responsive to suramin in vitro. Methods: Athymic nude mice bearing DU145 or SR DU145 xenografts were treated intraperitoneally (IP) once weekly with normal saline (vehicle control) or suramin in normal saline. For data analysis mice were grouped as follows: 0 mg/kg (controls), <210 mg/kg, 210 to 260 mg/kg, or gt;260 mg/kg suramin. Results: The growth of DU145 xenografts was slowed by treatment with 210 to 260 mg/kg suramin IP once weekly: differences in tumor volume for the 210 to 260 mg/kg group compared with the control group on days 29 and 57 showed growth inhibited by 43% and 55%, respectively. At the same time, growth of SR DU145 xenografts generally was not slowed by suramin treatment at any dose, but appeared to be enhanced to some degree by all doses of suramin during the typical slower initial growth phase of xenografts of this cell line: differences in tumor volume compared with control on day 29 showed growth enhanced by 100% to 342%. Mice treated with 210 to 260 mg/kg maintained nadir suramin plasma levels near our clinically relevant target of 1 × 10⁻⁴ M. Conclusions: Suramin, without concomitant corticosteroid therapy, was effective in slowing the growth of DU145 xenografts in nude mice at clinically relevant plasma suramin levels. The data showing efficacy for DU145 xenografts was supported by the lack of efficacy at the same time for xenografts of cells known to be less responsive to suramin in vitro, i.e. the SR DU145 cells, at similar doses and nadir plasma suramin levels. In discussions on the utility of suramin our data should be considered as support for continuing the study of suramin in the treatment of advanced, androgen-independent prostate cancer. Received: 9 March 1998 / Accepted: 29 June 1998     

Inhibitory effect of suramin in rat models of angiogenesis in vitro and in vivo

The aim of the present study was to test the ability of the chemotherapeutic agent suramin to inhibit angiogenesis in experimental models in vitro and in vivo. In the culture of rat aortic rings on fibronectin, suramin dose-dependently inhibited vascular cell growth, achieving the maximal effect (mean − 88% versus controls, P < 0.05) at 400 μg/ml. Image analysis showed that suramin could inhibit microvessel sprouting in fibrin from rat aortic rings as evaluated by the ratio between the cellular area and the mean gray value of the sample (sprouting index); suramin at 50 μg/ml significantly reduced the sprouting index from the control value of 0.35 ± 0.04 to 0.14 ± 0.02 mm²/gray level (P < 0.05). Likewise, the area occupied by cells was 19.2 ± 1.8 mm² as compared with 41.8 ± 4.2 mm² in controls (P < 0.05). In the rat model of neovascularization induced in the cornea by chemical injury, suramin at 1.6 mg/eye per day reduced the length of blood vessels (0.7 ± 0.1 mm as compared with 1.5 ± 0.1 mm in controls, P < 0.05). In the same model the ratio between the area of blood vessels and the total area of the cornea (area fraction score) was decreased by suramin from 0.19 ± 0.02 in controls to 0.03 ± 0.003 (P < 0.05). Suramin given i.p. at 30 mg/kg per day markedly inhibited the neovascularization induced in the rat mesentery by compound 48/80 or conditioned medium from cells secreting the angiogenic protein fibroblast growth factor-3 (FGF-3). The area fraction score in control rats treated with compound 48/80 was 0.31 ± 0.03, and this was reduced to 0.07 ± 0.01 by suramin (P < 0.05). After i.p. administration of FGF-3 the area fraction score was reduced by suramin from 0.29 ± 0.03 to 0.05 ± 0.01 (P < 0.05). These results provide evidence that suramin exerts inhibitory effects on angiogenesis in both in vitro and in vivo models. Received: 9 January 1998 / Accepted: 29 June 1998     

苏拉明在肝纤维化大鼠肝星状细胞增殖和凋亡中的作用(英文)

本研究旨在探究苏拉明在肝星状细胞（HSCs）增殖、凋亡中的作用。将HSCs株分别在不同浓度的苏拉明和无苏拉明的培养基中体外培养。应用MTT法检测细胞增殖率,流式细胞术测定细胞周期和增殖指数;TUNEL法检测细胞凋亡率;显微镜下观察细胞形态学变化。结果显示苏拉明干预后,与对照组比较HSCs增殖率均显著减低;苏拉明(1.4×10^-5mol/L)干预72小时,HSCs增殖率降低最明显,且呈时间和剂量依赖性;苏拉明(1.4×10^-5mol/L)干预24小时,G₁期HSCs百分比显著升高,增殖指数显著降低,而HSCs凋亡率无显著变化。苏拉明对HSCs形态无显著影响。我们认为在实验剂量范围内,苏拉明可抑制HSCs增殖,而对HSCs凋亡无影响。