Glyceraldehyde-3-phosphate dehydrogenase (GAPDH, E.C. 1.2.1.12.) gene expression in two malignant human mammary epithelial cell lines: BT-20 and MCF-7. Regulation of gene expression by 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3).

Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is a key enzyme in the control of glycolysis. Its gene expression was analyzed in two breast cancer cell lines of human origin, BT-20 and MCF-7. We used a cDNA probe of 1.3 kb for Northern blot hybridization. It is found that GAPDH mRNA is overexpressed only in the poorly differentiated BT-20 cell line and that treatment of these cells by 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3) stimulates GAPDH mRNA expression in a dose-and time-dependent manner. The present investigation on the BT-20 cells indicates that the expression of GAPDH is sensitive to 1,25-(OH)2D3 and up-regulated by low doses of this steroid.     

High-performance liquid chromatographic determination of vinorelbine in human plasma and blood: application to a pharmacokinetic study

A sensitive and specific high-performance liquid chromatographic method with fluorescence detection (excitation wavelength: 280 nm; emission wavelength: 360 nm) was developed and validated for the determination of vinorelbine in plasma and blood samples. The sample pretreatment procedure involved two liquid-liquid extraction steps. Vinblastine served as the internal standard. The system uses a Spherisorb cyano analytical column (250x4.6 mm I.D.) packed with 5 microm diameter particles as the stationary phase and a mobile phase of acetonitrile-80 mM ammonium acetate (50:50, v/v) adjusted to pH 2.5 with hydrochloric acid. The assay showed linearity from 1 to 100 ng/ml in plasma and from 2.5 to 100 ng/ml in blood. The limits of quantitation were 1 ng/ml and 2.5 ng/ml, respectively. Precision expressed as RSD was in the range 3.9 to 20% (limit of quantitation). Accuracy ranged from 92 to 120%. Extraction recoveries from plasma and blood averaged 101 and 75%, respectively. This method was used to follow the time course of the concentration of vinorelbine in human plasma and blood samples after a 10-min infusion period of 20 mg/m2 of this drug in patients with metastatic cancer.     

Sensitive HPLC-fluorescence method for irinotecan and four major metabolites in human plasma and saliva: application to pharmacokinetic studies

BACKGROUND: We developed gradient HPLC methods for quantification of the antimitotic drug irinotecan (CPT-11) and its four metabolites, SN-38, SN-38 G, 7-ethyl-10-[4-N-(5-aminopentanoic acid)-1-piperidino]-carbonyloxycamptothecin (APC), and 7-ethyl-10-[4amino-1-piperidino]-carbonyloxycamptothecin (NPC), as the sum of the lactone and carboxylate forms, in human plasma and saliva. Camptothecin was used as internal standard. METHODS: The sample pretreatment involved protein precipitation with methanol-acetonitrile (50:50 by volume) followed by acidification with hydrochloric acid to convert the lactone ring-opened form into its lactone form, quantitatively. HPLC separation was performed on a Xterra RP18 column. The excitation wavelength was 370 nm, and the emission wavelength was set at 470 nm for the first 24 min and then at 534 nm for the next 4 min. The stabilities of irinotecan and its four metabolites in plasma, saliva, and acidic extracts were also investigated under various conditions. RESULTS: Assays were linear in the tested range of 0.5-1000 micro g/L. For the five analytes, limits of quantification were 0.5 micro g/L in both matrices. The interassay imprecision (as relative standard deviation) was 3.2-14% in plasma and 2.6-5.6% in saliva. Assay recoveries ranged from 92.8% to 111.2% for plasma and 100.1% to 104.1% for saliva. Mean extraction recovery from plasma or saliva was 90%. CONCLUSION: The developed assay can be used to determine pharmacokinetic parameters for CPT-11, SN-38, SN-38 G, APC, and NPC in plasma and saliva from patients with metastatic colorectal cancer.     

Ultrastructural analysis of megakaryocytes in GPV knockout mice

Lesions in the genes for GPIb alpha, GPIb beta or GPIX result in a bleeding diathesis, the Bernard-Soulier syndrome (BSS), which associates a platelet adhesion defect with thrombocytopenia, giant platelets and abnormal megakaryocytes (MK). The role of GPV, also absent in BSS, was recently addressed by gene targeting in mice. While a negative modulator function for GPV on thrombin-induced platelet responses was found in one model, the absence of GP V had no effect on GPIb-IX expression or platelet adhesion. Our study extends previous results and reports that electron microscopy of bone marrow from the GPV knockout mice revealed a normal MK ultrastructure and development of the demarcation membrane system (DMS). There was a usual presence of MK fragments in the bone marrow vascular sinus. Immunogold labelling of MK from the knockout mice showed a normal distribution of GPIb-IX in the DMS and on the cell surface. The distribution of fibrinogen, vWF and P-selectin was unchanged with, interestingly, P-selectin also localised within the DMS in both situations. Thus GPV is not crucial to MK development and platelet production, consistent with the fact that no mutation in the GPV gene has as yet been described in BSS.     

Inter- and intraindividual variabilities in pharmacokinetics of fentanyl after repeated 72-hour transdermal applications in cancer pain patients

Perception of pain by the patient is frequently one of the early signs preceding a diagnosis of cancer and, later, a sinister sign of disease progression. Among opioid drugs, transdermal fentanyl has been evaluated in the treatment of moderate to severe cancer pain. The objective of this study was to investigate the intra- and interindividual variabilities in pharmacokinetics after fentanyl drug delivery by the transdermal fentanyl patch delivery system in patients with cancer pain. As a first step, a liquid chromatography-mass spectrometry method was developed for the determination of the analgesic fentanyl in human plasma. This method was validated over the concentration range 0.15-100 ng/mL. The study group consisted of 29 inpatients (18 men and 11 women; age range 29-80 years). The initial transdermal fentanyl delivery rate was chosen depending on the patient's analgesic requirements. For 20 patients, the initial TTS fentanyl delivery rate was 25 or 50 microg/h. For 6 patients, the initial delivery rate was 75-150 microg/h. Two patients received up to 300 microg/h fentanyl delivery rate, and 3 patients received up to 350 microg/h fentanyl delivery rate. Fifteen of the 29 patients received rescue doses of subcutaneous or oral morphine, and 26 patients received paracetamol with codeine (30 mg per os). Blood samples were collected at the following intervals: 2-5, 22-26, or 45-47 hours following fentanyl patch application. The severity of pain experienced by the patient was assessed thrice daily using a visual analogue scale. The study period was 46 days. Large patient-to-patient variations in pharmacokinetic parameters occurred, although intraindividual variability was limited. A mean bioavailability of 78% was estimated; the total clearance averaged 41 L/h. From 25 to 100 mug/h fentanyl delivery rate, the pharmacokinetics was linear. At the 2 highest doses, an increase of total clearance was observed (>60 L/h). For the whole group, transdermal fentanyl treatment provided good to excellent pain relief in the majority of patients.     

Population pharmacokinetics of melphalan,infused over a 24-hour period,in patients with advanced malignancies

Purpose The objective of the present study was to characterize the population pharmacokinetics of melphalan infused over a 24-h period in patients with advanced malignancies.Methods Enrolled in the study were 64 patients (144 courses). The population pharmacokinetic analysis was performed using NONMEM through the graphical interface Visual-NM. Population characteristics were computed from an initial group of 43 patients (99 courses), and 21 additional patients (45 courses) were used for model validation. With the use of a one-compartment model, the influence of demographic and biological characteristics was examined. The basic parameters were total clearance (CL) and volume of distribution (V). The interoccasion variability was taken into account in the model. The drug exposure was estimated for each patient and correlated with markers of efficacy and toxicity.Results Data analysis was performed using a three-step approach. In step 2, a close relationship was found between creatinine clearance, gender and melphalan CL. The inclusion of this second stage model significantly improved the fit. Melphalan CL was higher in male patients (14.3±4.5 l/h per m²) than in female patients (12.3±4.5 l/h per m²). CL was also reduced somewhat in patients with decreased creatinine clearance. Large interindividual variability in pharmacokinetic parameters occurred (CL varied from 4.4 to 30.6 l/h per m²). The percentage intrapatient variability in clearance between courses was 25.4%. For determining melphalan AUC in clinical routine from one sample drawn at steady state, Bayesian methodology allowed a more accurate estimation of CL than the classical formula. Neutropenia and thrombocytopenia were the main haematological toxicities encountered; grade 4 was observed in 34 and 22 courses over a total of 144 courses, respectively. No significant relationship between AUC and haematological toxicity was found. In patients with prostatic cancer a weak relationship was observed between the decrease in PSA levels and AUC (P=0.0457), while in patients with ovarian cancer no relationship was found between AUC and CA125 levels.Conclusion The population pharmacokinetic approach developed in this study should allow dosage to be individualized in order to decrease toxicity while maintaining good efficacy.     

Modeling plasma and saliva topotecan concentration time course using a population approach

The purpose of this study was to develop a pharmacokinetic model simultaneously accounting for topotecan concentrations in plasma and saliva. Thirteen patients with metastatic epithelial ovarian cancer received topotecan. During the first and the second courses of treatment, each patient underwent pharmacokinetic evaluation. Data were analyzed using the nonlinear mixed-effect model program. The saliva concentrations were associated to a peripheral compartment while the central compartment described the plasma concentration time course. Thus, a three-compartment model was used; the basic parameters were: total clearance (CL), initial volume of distribution (V1), transfer rate constants (k12/k21 and k13/k31). The interoccasion variability was taken into account in the model. Data analysis was performed using a three-step approach; in step 2, a close relationship was found between creatinine CL and topotecan CL. The inclusion of this second stage model significantly improved the fit. Large interindividual variability in pharmacokinetic parameters occurred (CL varied from 10.4 to 23 L/h) while interoccasion variability was limited (6%). Seven additional courses were used for model validation. A limited sampling strategy using Bayesian estimation based on two sampling times (saliva at 25 min and plasma plus saliva at 8.5 h after the start of infusion) was developed. This study shows that salivary concentrations can be effectively used for drug monitoring.