RESUMEN
Action of protein kinases and phosphatases contributes to myocardial hypertrophy. PRL-3, a protein tyrosine phosphatase, was identified in a cDNA library from an explanted human heart obtained from a patient with idiopathic cardiomyopathy. PRL-3 is expressed in heart and skeletal muscle, exhibiting approximately 76% identity to the ubiquitous tyrosine phosphatase PRL-1, which was reported to increase cell proliferation. PRL-3 was cloned into E. coli and purified using affinity chromatography. PRL-3 activity was determined using the substrate 6,8-difluoro-4-methylumbelliferyl phosphate, and was inhibited by vanadate and analogs. HEK293 cells expressing PRL-3 demonstrated increased growth rates versus nontransfected cells or cells transfected with the catalytically inactive C104S PRL-3 mutant. The tyrosine phosphatase inhibitor, potassium bisperoxo (bipyridine) oxovanadate V, normalizes the growth rate of PRL-3 expressing cells to that of parental HEK293 cells in a concentration-dependent manner. Using FLIPR analysis, parental HEK293 cells mobilize calcium when stimulated with angiotensin-II (AngII). However, calcium mobilization is inhibited in cells expressing wild-type PRL-3 when stimulated with AngII, while cells expressing the inactive mutant of PRL-3 mobilize calcium to the same extent as parental HEK293 cells. Western blots comparing PRL-3 transfected cells to parental HEK293 cells showed dephosphorylation of p130(cas) in response to AngII. These data suggest a role for PRL-3 in the modulation of intracellular calcium transients induced by AngII.
Asunto(s)
Angiotensina II/farmacología , Señalización del Calcio/fisiología , Calcio/metabolismo , Proteínas Inmediatas-Precoces/genética , Proteínas Inmediatas-Precoces/metabolismo , Músculo Esquelético/enzimología , Proteínas Tirosina Fosfatasas/genética , Proteínas Tirosina Fosfatasas/metabolismo , Transducción de Señal/fisiología , Sustitución de Aminoácidos , Señalización del Calcio/efectos de los fármacos , Cardiomiopatías/enzimología , Cardiomiopatías/genética , División Celular/efectos de los fármacos , Línea Celular , Cromatografía de Afinidad , Clonación Molecular , Citosol/metabolismo , Inhibidores Enzimáticos/farmacología , Escherichia coli , Biblioteca de Genes , Humanos , Proteínas Inmediatas-Precoces/aislamiento & purificación , Mutagénesis Sitio-Dirigida , Miocardio/enzimología , Proteínas de Neoplasias , Técnicas de Cultivo de Órganos , Compuestos Organometálicos/farmacología , Fenantrolinas/farmacología , Proteínas Tirosina Fosfatasas/aislamiento & purificación , Proteínas Recombinantes/química , Proteínas Recombinantes/aislamiento & purificación , Proteínas Recombinantes/metabolismo , Transfección , Vanadatos/farmacologíaRESUMEN
PURPOSE: A phase II trial of paclitaxel infused over 96 hours in patients with metastatic breast cancer with demonstrated disease progression (PD) during short-infusion taxane treatment was performed to evaluate schedule-dependent activity with prolonged drug exposure. The tolerability of this strategy and its pharmacokinetic profile and pharmacodynamic correlates were also investigated. PATIENTS AND METHODS: Paclitaxel was administered to 26 patients with metastatic breast cancer at 120 to 140 mg/m2 intravenously over 96 hours. Twenty-three patients had demonstrated PD while receiving prior 3-hour paclitaxel, two during 1-hour docetaxel, and one during infusions of docetaxel and then paclitaxel. Twenty-one patients (81%) had no prior response to the short taxane infusion (primary resistance) and five (19%) had prior partial responses (PRs) of brief duration before PD (secondary resistance). Plasma paclitaxel concentrations were assessed at 24, 48, 72, and 96 hours. RESULTS: After delivery of 195 cycles, seven of 26 assessable patients (26.9%; 95% confidence interval, 11.6% to 47.8%) had major objective responses, with a median response duration of 6 months (range, 1 to 13). The predominant toxicities were neutropenia (76% grade > or = 3) and stomatitis (15% grade > or = 3). Despite omission of premedications, no significant hypersensitivity reactions occurred. The median steady-state paclitaxel concentration (Css) in 23 assessable patients was 0.047 mumol/L (range, .023 to .176). Patients who experienced grade 4 neutropenia had significantly decreased paclitaxel clearance and higher Css than those with grade 1 to 3 neutropenia (P < .05). Pretreatment elevation of hepatic transaminases was associated with delayed clearance (P < .01) and increased myelo-suppression and mucosal toxicity. CONCLUSION: Paclitaxel demonstrates activity against metastatic breast cancer when administered over 96 hours to patients with disease that recently had progressed during short taxane exposure. Delayed paclitaxel clearance and consequent increased toxicity occurred in patients with hepatic dysfunction. The activity observed supports preclinical data that suggest variability in efficacy and resistance patterns to paclitaxel based on duration of exposure.
Asunto(s)
Antineoplásicos Fitogénicos/administración & dosificación , Neoplasias de la Mama/patología , Paclitaxel/análogos & derivados , Paclitaxel/administración & dosificación , Taxoides , Adulto , Anciano , Antineoplásicos Fitogénicos/efectos adversos , Antineoplásicos Fitogénicos/farmacocinética , Hidrocarburos Aromáticos con Puentes/administración & dosificación , Docetaxel , Femenino , Humanos , Infusiones Intravenosas , Persona de Mediana Edad , Paclitaxel/efectos adversos , Paclitaxel/farmacocinética , Paclitaxel/farmacologíaRESUMEN
The effect of the coronary vasocilator agents dipyridamole and nifedapine on ischemia-induced changes in cardiac performance and coronary flow was studied in extra-corporeal-circulation supported, open-chest dogs during cardio-pulmonary bypass. Coronary flow and isovolumic cardiac performance were measured prior to clamping the aorta to induce global ischemic for 60 min and again after 30 min of reperfusion. Both agents given prior to ischemia significantly enhanced the coronary flow measured 30 min after reperfusion. Almost complete complete return of pre-ischemic left ventricular dp/dt and diastolic compliance was seen if dipyridamole was administered prior to the onset of ischemia. Dipridamole administered at the end of the ischemic period and prior to reperfusion also prevented the ischemia-induced fall in dp/dt but not the decrease in compliance. Myocardial high energy phosphate compounds decreased markedly during global ischemia and dipyridamole administration had no effect on the rate or extent of their depletion. Nifedapine administration led to even greater post-ischemic coronary vasodilation; however, the ischemia-induced decline in myocardial performance was not prevented.