RESUMEN
BACKGROUND: In the current study, the authors sought to determine the maximum tolerated dose (MTD) of the novel class 1 selective histone deacetylase inhibitor CXD101 in a dose escalation study in patients with advanced solid tumors or recurrent/refractory lymphoma. METHODS: The authors escalated the dose of CXD101 from 1 mg twice daily orally for 5 days in a 21-day cycle (3+3 design). RESULTS: A total of 39 patients were enrolled, 36 of whom received CXD101. Of the 30 patients in the escalation cohort, 29 were evaluable for determination of the dose-limiting toxicity (DLT). DLTs were noted at doses of 16 mg twice daily (1 of 6 patients), 20 mg twice daily (1 of 6 patients), and 24/25 mg twice daily (2 of 5 patients, both of whom developed neutropenic fever). The MTD was 20 mg twice daily, which achieved maximal plasma concentrations (±standard deviation) of 231±76 nM to 342±126 nM, which was within the biologically active range. Six patients received 20 mg twice daily in an expansion cohort. The most frequent adverse events were fatigue, nausea, and reversible cytopenia. Key grade 3 to 4 adverse events (according to Common Terminology Criteria for Adverse Events criteria [version 4.03]) included thrombocytopenia (11%), neutropenia (17%), and neutropenic fever (2%) across the 133 CXD101 cycles given. The toxicity profile was similar to that of licensing studies with other histone deacetylase inhibitors. In 22 evaluable patients receiving a dose of ≥16 mg twice daily (17 of whom had lymphoma and 5 of whom had solid tumors), 3 partial responses (2 in patients with classic Hodgkin lymphoma after allogenic stem cell transplantation and 1 in a patient with angioimmunoblastic T-cell lymphoma) and 1 complete response (in a patient with follicular lymphoma) were noted (overall response rate of 18%) in addition to 9 patients who achieved durable stable disease. Responses were noted predominantly among patients with lymphoma (tumor reduction noted in 63% of patients on standard computed tomography). CONCLUSIONS: The MTD in the current study was found to be 20 mg twice daily. Encouraging and durable activity was observed in patients with Hodgkin lymphoma, T-cell lymphoma, and follicular lymphoma.
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Inhibidores de Histona Desacetilasas/administración & dosificación , Linfoma Cutáneo de Células T/tratamiento farmacológico , Linfoma de Células T Periférico/tratamiento farmacológico , Neoplasias Cutáneas/tratamiento farmacológico , Adulto , Anciano , Enzimas Reparadoras del ADN/metabolismo , Proteínas de Unión al ADN/metabolismo , Esquema de Medicación , Femenino , Inhibidores de Histona Desacetilasas/efectos adversos , Humanos , Linfoma Cutáneo de Células T/metabolismo , Linfoma de Células T Periférico/metabolismo , Masculino , Dosis Máxima Tolerada , Persona de Mediana Edad , Neoplasias Cutáneas/metabolismo , Análisis de Supervivencia , Resultado del Tratamiento , Adulto JovenRESUMEN
BACKGROUND: Src is involved in cancer invasion and metastasis. AZD0424, an oral inhibitor of Src and ABL1, has shown evidence of anti-tumour activity in pre-clinical studies. METHODS: A phase Ia, dose escalation study was performed to assess the safety of continuous oral dosing with AZD0424 in advanced solid tumours. Secondary objectives included investigation of AZD0424 pharmacokinetics, effect on Src activity using markers of bone turnover, and anti-tumour activity. RESULTS: 41 patients were treated; 34 received AZD0424 once-daily at doses ranging from 5 mg to 150 mg, and 7 received 40 mg bi-daily 41.5% of patients experienced at least one AZD0424-related adverse event that was Grade 3-5 in severity, with patients treated at doses above 60 mg per day experiencing multiple treatment-related toxicities. The most commonly observed AZD0424-related adverse events were nausea, fatigue, anorexia and alopecia. Cmax and AUC increased linearly with dose and the mean±standard deviation t1/2 was 8.4±2.8 h. Clear evidence of Src target inhibition was seen at doses ⩾20 mg per day. No responses were observed and 7 patients (17.1%) achieved stable disease lasting 6 weeks or more. CONCLUSIONS: AZD0424 displayed no evidence of efficacy as monotherapy despite a clear pharmacodynamic effect. Further evaluation of AZD0424 monotherapy in patients with solid tumours is not recommended.
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Antineoplásicos/efectos adversos , Neoplasias/tratamiento farmacológico , Inhibidores de Proteínas Quinasas/efectos adversos , Administración Oral , Adulto , Anciano , Antineoplásicos/administración & dosificación , Relación Dosis-Respuesta a Droga , Femenino , Humanos , Masculino , Dosis Máxima Tolerada , Persona de Mediana Edad , Neoplasias/enzimología , Inhibidores de Proteínas Quinasas/administración & dosificación , Proteínas Proto-Oncogénicas c-abl/antagonistas & inhibidores , Familia-src Quinasas/antagonistas & inhibidoresRESUMEN
Oxidation of 4-methylcatechol previously exposed to aqueous calcium chloride was shown by ion chromatography to be associated with release of calcium ions. The catechol was oxidised to the corresponding orthoquinone by the use of tyrosinase from Agaricus bisporus. The oxidative release of calcium from the catechol is ascribed to the diminution of the available hydroxyl functions able to act as chelating groups. Our results suggest that the redox status of melanin may regulate calcium binding and influence calcium levels in pigmented cells.
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Calcio/metabolismo , Catecoles/metabolismo , Agaricus/enzimología , Calcio/química , Catecoles/química , Monofenol Monooxigenasa/metabolismo , Oxidación-Reducción , Quinonas/química , Quinonas/metabolismoRESUMEN
The inactivation of tyrosinase by resorcinol (1,3-dihydroxybenzene) and seventeen simple derivatives has been investigated using combined spectrophotometry and oximetry together with hplc/ms examination of the oxidation products. The results are consistent with a Quintox mechanism, analogous to that proposed for catechol inactivation of tyrosinase, in which the resorcinol substrate is oxidised via the monooxygenase route leading to a hydroxy intermediate that undergoes deprotonation and results in irreversible elimination of Cu(0) from the active site. Hplc/ms evidence for formation of the resorcinol monooxygenase product (3-hydroxy-ortho-quinone) is presented and the relationship between the ring position of simple resorcinol substituents (H, Me, F, Cl) and tyrosinase inactivation is rationalised.
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Monofenol Monooxigenasa/metabolismo , Resorcinoles/metabolismo , Dominio Catalítico , Catecoles/química , Catecoles/metabolismo , Cobre/química , Cobre/metabolismo , Cinética , Monofenol Monooxigenasa/antagonistas & inhibidores , Oxidación-Reducción , Oximetría , Unión Proteica , Resorcinoles/química , EspectrofotometríaRESUMEN
In vitro studies, using combined spectrophotometry and oximetry together with hplc/ms examination of the products of tyrosinase action demonstrate that hydroquinone is not a primary substrate for the enzyme but is vicariously oxidised by a redox exchange mechanism in the presence of either catechol, L-3,4-dihydroxyphenylalanine or 4-ethylphenol. Secondary addition products formed in the presence of hydroquinone are shown to stimulate, rather than inhibit, the kinetics of substrate oxidation.
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Hidroquinonas/metabolismo , Monofenol Monooxigenasa/metabolismo , Catecoles/química , Catecoles/metabolismo , Cromatografía Líquida de Alta Presión , Dihidroxifenilalanina/química , Dihidroxifenilalanina/metabolismo , Hidroquinonas/química , Cinética , Espectrometría de Masas , Oxidación-Reducción , Oximetría , Fenoles/química , Fenoles/metabolismo , EspectrofotometríaRESUMEN
4-Fluoro-1,2-benzoquinone, generated by tyrosinase oxidation of 4-fluorocatechol in aqueous buffer, rapidly undergoes substitution by O-nucleophiles (water or catechols) with release of fluoride. 4-Chloro- and 4-bromocatechol behave similarly. The reactions, which have toxicological implications, have been monitored by spectrophotometry and HPLC/MS, and intermediate and final products, including dibenzodioxins, identified.
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Catecoles/metabolismo , Dioxinas/química , Halógenos/química , Monofenol Monooxigenasa/metabolismo , Benzoquinonas/química , Biocatálisis , Catecoles/química , Cromatografía Líquida de Alta Presión , Espectrometría de Masas , Oxidación-ReducciónRESUMEN
3,6-Difluorocatechol, which cannot act as a monooxygenase tyrosinase substrate, is an oxidase substrate, and, in contrast to other catechols, oxidation does not lead to suicide-inactivation, providing experimental evidence for an inactivation mechanism involving reductive elimination of Cu(0) from the active site.
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Catecoles/química , Monofenol Monooxigenasa/metabolismo , Catálisis , Dominio Catalítico , Catecol Oxidasa/metabolismo , Catecoles/metabolismo , Cobre/metabolismo , Genes Transgénicos Suicidas , Cinética , Estructura Molecular , Oxidación-Reducción , Relación Estructura-Actividad , Especificidad por SustratoRESUMEN
A method is described to enhance the sensitivity of fluorescence detection of cis-combretastatins using a short post-column photolysis coil with a mercury lamp, by inducing the rapid conversion to the trans isomer. Although all the compounds studied showed enhanced fluorescence after photolysis, there were large differences in the absolute level, with the inherent response of the catechol CA1 being much lower than the corresponding phenolic CA4. Brief exposure to the deuterium lamp in a photodiode array detector also resulted in significant enhancement.
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Bibencilos/análisis , Estilbenos/análisis , Cromatografía Líquida de Alta Presión , Fotólisis , Espectrometría de FluorescenciaRESUMEN
Tyrosinase is a mono-oxygenase with a dinuclear copper catalytic center which is able to catalyze both the ortho-hydroxylation of monophenols (cresolase activity) and the oxidation of catechols (catecholase activity) yielding ortho-quinone products. Tyrosinases appear to have arisen early in evolution and are widespread in living organisms where they are involved in several processes, including antibiosis, adhesion of molluscs, the hardening of the exoskeleton of insects, and pigmentation. Tyrosinase is the principal enzyme of melanin formation in vertebrates and is of clinical interest because of the possible utilization of its activity for targeted treatment of malignant melanoma. Tyrosinase is characterised by an irreversible inactivation that occurs during the oxidation of catechols. In a recent publication we proposed a mechanism to account for this feature based on the ortho-hydroxylation of catecholic substrates, during which process Cu(II) is reduced to Cu(0) which no longer binds to the enzyme and is eliminated (reductive elimination). Since this process is dependent on cresolase activity of tyrosinase, a strong prediction of the proposed inactivation mechanism is that it will not be exhibited by enzymes lacking cresolase activity. We show that the catechol oxidase readily extracted from bananas (Musa cavendishii) is devoid of cresolase activity and that the kinetics of catechol oxidation do not exhibit inactivation. We also show that a species with the molecular mass of the putative cresolase oxidation product is formed during tyrosinase oxidation of 4-methylcatechol. The results presented are entirely consistent with our proposed mechanism to account for suicide-inactivation of tyrosinase.
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Agaricus/enzimología , Monofenol Monooxigenasa/metabolismo , Musa/enzimología , Catálisis , Catecoles/química , Catecoles/metabolismo , Activación Enzimática , Cinética , Oxidación-Reducción , Oxígeno/metabolismo , Resorcinoles/metabolismoRESUMEN
As the population ages, more elderly patients require radiotherapy-based treatment for their pelvic malignancies, including muscle-invasive bladder cancer, as they are unfit for major surgery. Therefore, there is an urgent need to find radiosensitizing agents minimally toxic to normal tissues, including bowel and bladder, for such patients. We developed methods to determine normal tissue toxicity severity in intestine and bladder in vivo, using novel radiotherapy techniques on a small animal radiation research platform (SARRP). The effects of panobinostat on in vivo tumor growth delay were evaluated using subcutaneous xenografts in athymic nude mice. Panobinostat concentration levels in xenografts, plasma, and normal tissues were measured in CD1-nude mice. CD1-nude mice were treated with drug/irradiation combinations to assess acute normal tissue effects in small intestine using the intestinal crypt assay, and later effects in small and large intestine at 11 weeks by stool assessment and at 12 weeks by histologic examination. In vitro effects of panobinostat were assessed by qPCR and of panobinostat, TMP195, and mocetinostat by clonogenic assay, and Western blot analysis. Panobinostat resulted in growth delay in RT112 bladder cancer xenografts but did not significantly increase acute (3.75 days) or 12 weeks' normal tissue radiation toxicity. Radiosensitization by panobinostat was effective in hypoxic bladder cancer cells and associated with class I HDAC inhibition, and protein downregulation of HDAC2 and MRE11. Pan-HDAC inhibition is a promising strategy for radiosensitization, but more selective agents may be more useful radiosensitizers clinically, resulting in fewer systemic side effects. Mol Cancer Ther; 17(2); 381-92. ©2017 AACRSee all articles in this MCT Focus section, "Developmental Therapeutics in Radiation Oncology."
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Inhibidores de Histona Desacetilasas/uso terapéutico , Fármacos Sensibilizantes a Radiaciones/uso terapéutico , Neoplasias de la Vejiga Urinaria/radioterapia , Animales , Modelos Animales de Enfermedad , Inhibidores de Histona Desacetilasas/farmacología , Humanos , Ratones , Ratones Desnudos , Fármacos Sensibilizantes a Radiaciones/farmacología , TransfecciónRESUMEN
Nitrothienylprop-2-yl ether formation on the 3'-phenolic position of combretastatin A-4 (1) abolishes the cytotoxicity and tubulin polymerization-inhibitory effects of the drug. 5-Nitrothiophene derivatives of 1 were synthesized following model kinetic studies with analogous coumarin derivatives, and of these, compound 13 represents a promising new lead in bioreductively targeted cytotoxic anticancer therapies. In this compound, optimized gem-dimethyl alpha-carbon substitution enhances both the aerobic metabolic stability and the efficiency of hypoxia-mediated drug release. Only the gem-substituted derivative 13 released 1 under anoxia in either in vitro whole-cell experiments or supersomal suspensions. The rate of release of 1 from the radical anions of these prodrugs is enhanced by greater methyl substitution on the alpha-carbon. Cellular and supersomal studies showed that this alpha-substitution pattern controls the useful range of oxygen concentrations over which 1 can be effectively released by the prodrug.
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Antineoplásicos Fitogénicos/síntesis química , Antineoplásicos Fitogénicos/metabolismo , Profármacos/síntesis química , Profármacos/metabolismo , Estilbenos/química , Estilbenos/metabolismo , Tiofenos/síntesis química , Animales , Antineoplásicos Fitogénicos/química , Relación Dosis-Respuesta a Droga , Humanos , Hígado/efectos de los fármacos , Hígado/metabolismo , Ratones , Nitrocompuestos/química , Profármacos/química , Tiofenos/química , Factores de Tiempo , Tubulina (Proteína)/efectos de los fármacos , Tubulina (Proteína)/metabolismo , Células Tumorales CultivadasRESUMEN
Physiological differences between tumor and normal vasculature provide a target for drug discovery. In particular, the immature nature of tumor vasculature may render it intrinsically sensitive to disruption by agents affecting the endothelial cell cytoskeleton, including tubulin-binding agents. In this article, we report the synthesis of a water-soluble phosphate prodrug, ZD6126, of the tubulin-binding agent N-acetylcolchinol. In vitro studies demonstrate the comparative tubulin-binding properties of the prodrug and active drug, and show the induction of pronounced, reversible changes in endothelial cell morphology at subcytotoxic doses. Neither ZD6126 nor N-acetylcolchinol showed effects on the growth of human umbilical vein endothelial cells at concentrations below 100 micro M. In contrast, changes in endothelial cell morphology were seen at much lower, noncytotoxic concentrations (0.1 micro M) of ZD6126 and more pronounced effects were seen in proliferating versus confluent endothelial cell cultures. In vivo studies were carried out using a murine tumor model (CaNT) with single administration of a dose well below the maximum tolerated dose. These studies showed a large reduction in vascular volume, induction of extensive necrosis in tumors, and a reduced tumor cell yield in a clonal excision assay, consistent with vascular rather than cytotoxic effects. A viable rim of tumor remained after single-dose administration and minimal growth delay was observed. However, well-tolerated, multiple administration regimens led to pronounced tumor-growth delay. In the human xenograft FaDu, the growth delay given by a single dose of paclitaxel was enhanced by combination with a single dose of ZD6126, and the growth delay given by the combination was greater than the sum of the growth delays from the individual treatments. These findings show that ZD6126 is a promising antivascular agent for the treatment of solid tumors.
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Inhibidores de la Angiogénesis/síntesis química , Inhibidores de la Angiogénesis/farmacología , Colchicina/análogos & derivados , Endotelio Vascular/efectos de los fármacos , Neoplasias Experimentales/irrigación sanguínea , Compuestos Organofosforados/síntesis química , Compuestos Organofosforados/farmacología , Profármacos/síntesis química , Profármacos/farmacología , Adenocarcinoma/irrigación sanguínea , Adenocarcinoma/tratamiento farmacológico , Adenocarcinoma/patología , Inhibidores de la Angiogénesis/farmacocinética , Animales , Carcinoma de Células Escamosas/irrigación sanguínea , Carcinoma de Células Escamosas/tratamiento farmacológico , Carcinoma de Células Escamosas/patología , Bovinos , Supervivencia Celular/efectos de los fármacos , Colchicina/farmacología , Relación Dosis-Respuesta a Droga , Endotelio Vascular/citología , Femenino , Humanos , Neoplasias Mamarias Experimentales/irrigación sanguínea , Neoplasias Mamarias Experimentales/tratamiento farmacológico , Neoplasias Mamarias Experimentales/patología , Ratones , Ratones Endogámicos CBA , Ratones SCID , Necrosis , Neoplasias Experimentales/tratamiento farmacológico , Neoplasias Experimentales/patología , Neovascularización Patológica/tratamiento farmacológico , Compuestos Organofosforados/farmacocinética , Neoplasias Faríngeas/irrigación sanguínea , Neoplasias Faríngeas/tratamiento farmacológico , Neoplasias Faríngeas/patología , Profármacos/farmacocinética , Unión Proteica , Tubulina (Proteína)/metabolismo , Ensayos Antitumor por Modelo de XenoinjertoRESUMEN
Regions of insufficient oxygen supply-hypoxia-occur in diverse contexts across biology in both healthy and diseased organisms. The difference in the chemical environment between a hypoxic biological system and one with normal oxygen levels provides an opportunity for targeting compound delivery to hypoxic regions by using bioreductive prodrugs. Here we detail a protocol for the efficient synthesis of (1-methyl-2-nitro-1H-imidazol-5-yl)methanol, which is a key intermediate that can be converted into a range of 1-methyl-2-nitro-1H-imidazole-based precursors of bioreductive prodrugs. We outline methods for attaching the bioreductive group to a range of functionalities, and we discuss the strategy for positioning of the group on the biologically active parent compound. We have used two parent checkpoint kinase 1 (Chk1) inhibitors to exemplify the protocol. The PROCEDURE also describes a suite of reduction assays, of increasing biological relevance, to validate the bioreductive prodrug. These assays are applied to an exemplar compound, CH-01, which is a bioreductive Chk1 inhibitor. This protocol has broad applications to the development of hypoxia-targeted compounds.
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Antineoplásicos/síntesis química , Inhibidores Enzimáticos/síntesis química , Hipoxia , Metronidazol/análogos & derivados , Profármacos/síntesis química , Proteínas Quinasas/metabolismo , Antineoplásicos/farmacología , Línea Celular Tumoral , Quinasa 1 Reguladora del Ciclo Celular (Checkpoint 1) , Inhibidores Enzimáticos/farmacología , Humanos , Metronidazol/síntesis química , Metronidazol/farmacología , Profármacos/farmacología , Tecnología Farmacéutica/métodosRESUMEN
BACKGROUND: Allergen-induced late airway response offers important pharmacodynamic targets, including T helper 2 (TH2) biomarkers. However, detection of inflammatory markers has been limited in dithiothreitol-processed sputum. OBJECTIVES: To test whether allergen-induced TH2 inflammatory markers can be reproducibly quantified by sensitive detection techniques in ultracentrifuged sputum and the effect of fluticasone (FP) on these endpoints. METHODS: Thirteen allergic asthmatics with dual allergen-induced airway responses, documented during a single-blind placebo run-in period, participated in a double-blind, two-period crossover study. Each period consisted of three consecutive days, separated by ≥3 weeks. Following randomization, subjects inhaled FP (500 µg bid, five doses total) or placebo. On Day 2 in each study period, allergen challenge was performed and airway response measured by forced expiratory volume in 1 sec (FEV1) until 7 h post-challenge. Sputum was induced 24 h pre-allergen and 7 and 24 h post-allergen. Sputum samples were split into two portions: TH2 biomarkers were quantified by Meso Scale multiplex platform following ultracentrifugation, and cell differentials were counted on Giemsa-May-Grünwald-stained cytospins. Allergen-induced changes in inflammatory endpoints were compared between FP and placebo using a mixed model ANCOVA. RESULTS: Inhaled allergen induced dual airway responses in all subjects during both placebo periods with reproducible late asthmatic response (LAR) and increased sputum inflammatory biomarkers (IL-2, IL-4, IL-13, and eotaxin-1) and eosinophil counts. FP effectively blunted both the LAR and the inflammatory biomarkers. CONCLUSIONS: Combining novel, sensitive quantification methods with ultracentrifugation allows reproducible quantification of sputum biomarkers following allergen challenge, reversed by FP. This approach allows non-invasive identification of pharmacodynamic targets for anti-asthma therapies.
RESUMEN
Increasing chemotherapy delivery to tumors, while enhancing drug uptake and reducing side effects, is a primary goal of cancer research. In mouse and human cancer models in vivo, we show that coadministration of low-dose Cilengitide and Verapamil increases tumor angiogenesis, leakiness, blood flow, and Gemcitabine delivery. This approach reduces tumor growth, metastasis, and minimizes side effects while extending survival. At a molecular level, this strategy alters Gemcitabine transporter and metabolizing enzyme expression levels, enhancing the potency of Gemcitabine within tumor cells in vivo and in vitro. Thus, the dual action of low-dose Cilengitide, in vessels and tumor cells, improves chemotherapy efficacy. Overall, our data demonstrate that vascular promotion therapy is a means to improve cancer treatment.
Asunto(s)
Antimetabolitos Antineoplásicos/administración & dosificación , Carcinoma Pulmonar de Lewis/tratamiento farmacológico , Carcinoma Pulmonar de Lewis/patología , Desoxicitidina/análogos & derivados , Neoplasias Pancreáticas/tratamiento farmacológico , Venenos de Serpiente/administración & dosificación , Verapamilo/administración & dosificación , Animales , Antimetabolitos Antineoplásicos/uso terapéutico , Protocolos de Quimioterapia Combinada Antineoplásica , Línea Celular Tumoral , Desoxicitidina/administración & dosificación , Desoxicitidina/uso terapéutico , Sinergismo Farmacológico , Humanos , Pulmón/irrigación sanguínea , Pulmón/patología , Ratones , Ratones Endogámicos C57BL , Trasplante de Neoplasias , Neovascularización Patológica/tratamiento farmacológico , Páncreas/irrigación sanguínea , Páncreas/patología , Neoplasias Pancreáticas/patología , Venenos de Serpiente/uso terapéutico , Verapamilo/uso terapéutico , GemcitabinaRESUMEN
One-electron oxidation of (6R)-5,6,7,8-tetrahydrobiopterin (H(4)B) by the azide radical generates the radical cation (H(4)B(*)(+)) which rapidly deprotonates at physiological pH to give the neutral trihydrobiopterin radical (H(3)B(*)); pK(a) (H(4)B(*)(+) <==> H(3)B(*) + H(+)) = (5.2 +/- 0.1). In the absence of ascorbate both the H(4)B(*)(+) and H(3)B(*) radicals undergo disproportionation to form quinonoid dihydrobiopterin (qH(2)B) and the parent H(4)B with rate constants k(H(4)B(*)(+) + H(4)B(*)(+)) = 6.5 x 10(3) M(-1) s(-1) and k(H(3)B(*) + H(3)B(*)) = 9.3 x 10(4) M(-1) s(-1), respectively. The H(3)B(*) radical is scavenged by ascorbate (AscH(-)) with an estimated rate constant of k(H(3)B(*) + AscH(-)) similar 1.7 x 10(5) M(-1) s(-1). At physiological pH the pterin rapidly scavenges a range of biological oxidants often associated with cellular oxidative stress and nitric oxide synthase (NOS) dysfunction including hydroxyl ((*)OH), nitrogen dioxide (NO(2)(*)), glutathione thiyl (GS(*)), and carbonate (CO(3)(*-)) radicals. Without exception these radicals react appreciably faster with H(4)B than with AscH(-) with k(*OH + H(4)B) = 8.8 x 10(9) M(-1) s(-1), k(NO(2)(*) + H(4)B) = 9.4 x 10(8) M(-1) s(-1), k(CO(3)(*-) + H(4)B) = 4.6 x 10(9) M(-1) s(-1), and k(GS(*) + H(4)B) = 1.1 x 10(9) M(-1) s(-1), respectively. The glutathione disulfide radical anion (GSSG(*-)) rapidly reduces the pterin to the tetrahydrobiopterin radical anion (H(4)B(*-)) with a rate constant of k(GSSG(*-) + H(4)B) similar 4.5 x 10(8) M(-1) s(-1). The results are discussed in the context of the general antioxidant properties of the pterin and the redox role played by H(4)B in NOS catalysis.
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Ácido Ascórbico/metabolismo , Biopterinas/análogos & derivados , Biopterinas/metabolismo , Depuradores de Radicales Libres/metabolismo , Radicales Libres/metabolismo , Carbonatos/metabolismo , Cromatografía Líquida de Alta Presión , Disulfuro de Glutatión/metabolismo , Concentración de Iones de Hidrógeno , Radical Hidroxilo/metabolismo , Cinética , Óxido Nítrico Sintasa/metabolismo , Dióxido de Nitrógeno/metabolismo , Oxidación-Reducción , Radiólisis de Impulso , Factores de TiempoRESUMEN
Many isoprenylated proteins are known to participate in signal transduction, but not all have been identified. Using an in vitro prenylation screen, two human cDNAs (PTP(CAAXI) and PTP(CAAX2)) homologous to the rat PRL-1 and human OV-1 protein tyrosine phosphatase genes were identified. PTP(CAAXI) and PTP(CAAX2) were farnesylated in vitro by mammalian farnesyl:protein transferase, and epitope-tagged PTP(CAAX2) was prenylated in epithelial cells. Overexpression of PTP(CAAXI) and PTP(CAAX2) in epithelial cells caused a transformed phenotype in culture and tumor growth in nude mice. Thus, PTP(CAAXI) and PTP(CAAX2) represent a novel class of isoprenylated, oncogenic protein tyrosine phosphatases.
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Transferasas Alquil y Aril , Prenilación de Proteína , Proteínas Tirosina Fosfatasas/metabolismo , Transferasas/metabolismo , Secuencia de Aminoácidos , Animales , Secuencia de Bases , Proteínas de Ciclo Celular , Transformación Celular Neoplásica , Cricetinae , Humanos , Proteínas Inmediatas-Precoces/genética , Proteínas Inmediatas-Precoces/metabolismo , Proteínas de la Membrana , Ratones , Datos de Secuencia Molecular , Proteínas de Neoplasias , Fenotipo , Proteínas Tirosina Fosfatasas/genética , Células Tumorales CultivadasRESUMEN
BACKGROUND AND PURPOSE: Treatment of head and neck tumors by the ARCON regimen has yielded high local control rates. As a result of this treatment intensification there was some increase in mainly acute toxicity of radiotherapy, but nicotinamide by itself has specific side effects such as nausea and vomiting. Due to these side effects and with the initial dose of 80 mg/kg, 31% of the patients discontinued nicotinamide intake. The aim of the study was to investigate the effect of a dose reduction to 60 mg/kg, and the addition of domperidone on the side effects of nicotinamide and its pharmacokinetic profile. PATIENTS AND METHODS: In 22 patients blood plasma nicotinamide levels were determined after intake of 60 mg/kg nicotinamide. A next group of 87 patients received 60 mg/kg nicotinamide in combination with domperidone. In ten of these patients blood plasma nicotinamide levels were also determined. A full pharmacokinetic profile was constructed over the first 24 h after intake of the first drug dose. Furthermore, daily plasma levels at 1 h after nicotinamide intake was determined in the first and last weeks of radiotherapy. All patients were treated according to the ARCON schedule. RESULTS AND DISCUSSION: The mean maximum plasma nicotinamide concentration was 793 nmol/ml without domperidone and 776 nmol/ml with domperidone. The median time at which the maximum concentration occurred was not significantly different for 60 mg/kg nicotinamide without or with domperidone (0.46 versus 0.54 h). The side effects were drastically reduced if nicotinamide was accompanied by domperidone. The percentage of patients that stopped nicotinamide intake was reduced from 32% without domperidone to 14% with domperidone. No correlation was found between the plasma peak concentrations of nicotinamide and the severity of side effects. CONCLUSION: The currently used dose of 60 mg/kg nicotinamide results in a 30% reduction in peak plasma concentrations compared with 80 mg/kg nicotinamide. If nicotinamide was given in combination with domperidone, 86% of the patients continued the nicotinamide medication until the end of the treatment period.
Asunto(s)
Carcinoma/radioterapia , Domperidona/farmacología , Niacinamida/farmacocinética , Neoplasias Orofaríngeas/radioterapia , Adulto , Anciano , Anciano de 80 o más Años , Dióxido de Carbono/administración & dosificación , Carcinoma/metabolismo , Domperidona/uso terapéutico , Fraccionamiento de la Dosis de Radiación , Femenino , Humanos , Masculino , Persona de Mediana Edad , Náusea/inducido químicamente , Niacinamida/efectos adversos , Niacinamida/sangre , Neoplasias Orofaríngeas/metabolismo , Oxígeno/administración & dosificación , Fármacos Sensibilizantes a Radiaciones/administración & dosificación , Vómitos/inducido químicamenteRESUMEN
Indole-3-acetic acid and some derivatives are oxidized by horseradish peroxidase, forming a radical-cation that rapidly fragments (eliminating CO(2)) to form cytotoxic products. No toxicity is seen when either indole-3-acetic acid or horseradish peroxidase is incubated alone at concentrations that together form potent cytotoxins. Unexpectedly, 5-fluoroindole-3-acetic acid, which is oxidized by horseradish peroxidase compound I 10-fold more slowly than indole-3-acetic acid, is much more cytotoxic towards V79 hamster fibroblasts in the presence of peroxidase than the unsubstituted indole. The fluorinated prodrug/peroxidase combination also shows potent cytotoxic activity in human and rodent tumor cell lines. Cytotoxicity is thought to arise in part from the formation of 3-methylene-2-oxindole (or analogues) that can conjugate with thiols and probably DNA or other biological nucleophiles. Levels of the fluorinated prodrug in the murine carcinoma NT after intraperitoneal administration of 50 mg/kg were about 200 microM. Although these were 4-5-fold lower than plasma levels (which reached 1mM), the integrated area under the concentration/time curve in tumors over 2 hr was approximately 20 mM min, almost double the exposure needed to achieve approximately 90-99% cell kill in human MCF7 breast or HT29 colon tumor cell lines and CaNT murine cells in vitro, although the human bladder T24 carcinoma cell line was more resistant. The high cytotoxicity of 5-fluoroindole-3-acetic acid after oxidative activation suggests its further evaluation as a prodrug for targeted cancer therapy involving antibody-, polymer-, or gene-directed delivery of horseradish peroxidase or similar activating enzymes.
Asunto(s)
Antineoplásicos/farmacología , Ácidos Indolacéticos/farmacología , Peroxidasas/metabolismo , Profármacos/farmacología , Animales , Antineoplásicos/metabolismo , Antineoplásicos/farmacocinética , Supervivencia Celular/efectos de los fármacos , Modelos Animales de Enfermedad , Sistemas de Liberación de Medicamentos , Femenino , Flúor/metabolismo , Glutatión/metabolismo , Células HT29 , Humanos , Ácidos Indolacéticos/metabolismo , Ácidos Indolacéticos/farmacocinética , Ratones , Ratones Endogámicos CBA , Neoplasias Experimentales/metabolismo , Oxidación-Reducción , Profármacos/metabolismo , Profármacos/farmacocinéticaRESUMEN
3-(4-Methylcoumarin-7-yloxy)methylindole-4,7-diones were synthesised as model prodrugs in order to investigate the correlation between rates of reductive elimination from the (indolyl-3-yl)methyl position with reductive metabolism by hypoxic tumor cells and NADPH: cytochrome P450. Rates of elimination of the chromophore/fluorophore (7-hydroxy-4-methylcoumarin) following one-electron reduction of indolequinones to their semiquinone radicals (Q*-) was measured by pulse radiolysis utilising spectrophotometric and fluorometric detection. Incorporation of a thienyl or methyl substituent at the (indol-3-yl)CHR-position (where R=thienyl or methyl adjacent to the phenolic ether linking bond) significantly shortened the half-life of reductive elimination from 87 to 6 and 2 ms, respectively. Elimination from the methyl substituted analogue can thus compete effectively with the reaction of the semiquinone radical with oxygen at levels typically present in tumours (half-life approximately 1.8 ms at 0.5% O2). Chemical kinetic predictions were confirmed by metabolism in breast tumour MCF-7 cells between 0-2.1% O2. Rates of reductive release of the fluorophore from the non-fluorescent parent indolequinones (R=H, Me, thienyl) were similar under anoxia ( approximately 1.7 nmol coumarinmin(-1)mg protein(-1)) reflecting the similarity in one-electron reduction potential. Whereas coumarin release from the indolequinone (R=H) was completely inhibited above 0.5% O2, the enhanced rate of reductive elimination when R=thienyl or Me increased the metabolic rate of release to approximately 0.35 and 0.7 nmol coumarinmin(-1)mg protein(-1), respectively at 0.5% O2; complete inhibition occurring by 2.1% O2. Similar 'oxygen profiles' of release were observed with NADPH: cytochrome P450 reductase. In conclusion, it is possible to modify rates of reductive elimination from indolequinones to control the release of drugs over a range of tumour hypoxia.