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J Robert

Publications and source records attributed to J Robert.

At least 163 records · Page 9Linked to original sources
PubMed1997

Multicentric evaluation of the MDR phenotype in leukemia. French Network of the Drug Resistance Intergroup, and Drug Resistance Network of Assistance Publique-Hôpitaux de Paris.

The wide discrepancies in the frequency of 'positive' samples for multidrug resistance (MDR) phenotype within the same type of tumor observed in the literature justified the need for the definition of consensus recommendations. To define standard techniques of MDR phenotype measurement, we ran a large multicentric evaluation of the different methods available. Thirty-six French centers participated in the study, and 742 samples of 2-10 x 10(6) viable cells were sent by overnight express mail between December 1993 and February 1996. The same batches of MRK16, 4E3 and UIC2 were used. Nineteen samples of leukemia (12 AML, 1 ALL, 6 lymphoproliferative syndromes) and six leukemic cell lines with different levels of MDR expression were tested. Five meetings reached agreement concerning the guidelines for each technique, except immunocytochemistry. The 19 fresh samples were tested by each center using one to four techniques among cytofluorometry, immunocytochemistry, functional tests and RT-PCR. Five samples were diagnosed as 'negative' according to local criteria, with few discordant results (0 to 16% of 'positive' results). For all the 14 remaining samples, large discrepancies were observed from center to center, and from one technique to another. No correlations could be found between techniques. Flow cytometric analysis of cells already exposed to MRK16 or control IgG2A, fixed in paraformaldehyde and sent to centers did not reduce the discrepancies between centers in two of the four samples with moderate expression, emphasizing the role of histogram interpretation. The use of alternative monoclonal antibodies (4E3 and UIC2) did not reduce the discrepancies observed. In a second step, the K562 parental cell line, a low resistant subline (K562/HHT100, x7 resistance index to DNR) and a high resistant subline (K562/HHT300, x125 resistance index to DNR) were sent blindly three times, with an increasing level of recommendations for flow cytometry. Dramatic improvements were observed in cytometric results when the result was expressed as the ratio of arithmetic mean of fluorescence of antibody (10 microg of MRK16)/arithmetic mean of fluorescence of control (10 microg IgG2A): the proportion of expected results increased from 61 to 100% for K562, and from 37 to 85% for K562/HHT100. For uptake and drug efflux measurements, the use of 1 h uptake of 0.1 microM of rhodamine, followed by 1 h efflux +/-10 microM of verapamil, permitted an increased reproducibility of the technique from 71 to 100% for K562 and K562/HHT100. Whatever the technique used, concordant results were obtained for K562/HHT300. The immunocytochemistry, using several antibodies (MRK16, JSB1 and C219) gave many non-interpretable results (44%), due to a frequent high background and discordant results between antibodies in the same centers, and discordant conclusions between centers. The group does not recommend this technique for circulating tumoral cells.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1997

French multicentric evaluation of mdr1 gene expression by RT-PCR in leukemia and solid tumours. Standardization of RT-PCR and preliminary comparisons between RT-PCR and immunohistochemistry in solid tumours. French Network of the Drug Resistance Intergroup, and Drug Resistance Network of Assistance Publique-Hôpitaux de Paris.

Since there is no consensus on the techniques for multidrug resistance (MDR) phenotype evaluation, many discrepancies concerning the importance and frequency of mdr1 gene expression in leukemias and solid tumors are observed in the literature. In order to establish an inter-laboratory consensus in France, a multicenter study was carried out to propose further guidelines for MDR phenotype evaluation. The techniques used by the 38 laboratories participating in the trial were: immunodetection (immunohisto and/or cytochemistry, flow cytometry), functional tests, reverse transcription-polymerase chain reaction (RT-PCR) or Northern blot. We present the results obtained by 19 laboratories concerning the measurement of mdr1 gene expression assessed by RT-PCR or Northern blot in: (1)19 samples of tumor cells obtained from leukemic patients; (2) six solid tumor samples obtained at surgery; (3) eight cell lines exhibiting variable levels of resistance, and; (4)10 preparations of RNA and of cDNA obtained from solid tumors. Standardization of the RT-PCR technique and preliminary results comparing RT-PCR with immunohistochemistry in solid tumors are also reported.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1997

Pacemaker endocarditis due to Candida albicans: case report and review.

We describe a case of pacemaker endocarditis due to Candida albicans in a patient who responded favorably to combined surgical and antifungal therapy. Only five cases of candidal pacemaker endocarditis have been reported previously. We review these five cases and discuss the clinical presentation and therapy for this disease in comparison with candidal prosthetic valve endocarditis.

Candida albicans↗
PubMed1997

Cellular pharmacology of lipophilic anthracyclines in human tumor cells in culture selected for resistance to doxorubicin.

We have studied the cytotoxicity and intracellular accumulation of two lipophilic anthracyclines, pirarubicin and idarubicin, as compared to doxorubicin, in two human tumor cell lines, MCF7 and K562, and in their doxorubicin-resistant counterparts, presenting the multidrug-resistant (MDR) phenotype. The new lipophilic anthracyclines were found to present a higher cytotoxicity and accumulation than the reference anthracycline, doxorubicin, and there was a significant inverse correlation between drug accumulation and IC50 in both cell types. With the aim of identifying the reasons for the higher cytotoxicity and accumulation of lipophilic anthracyclines, we used and compared the efficiency of three MDR modulators, verapamil, quinine and S-9788. We showed that all three were able to sensitize the resistant cells to the three anthracyclines, but with different efficiencies, S-9788 being the most active reverter and quinine the least active at equimolar doses. We also observed that there was no correlation between the abilities of a modulator to reverse resistance and to restore drug accumulation. In view of the sustained activity of the modulators to increase pirarubicin and idarubicin cytotoxicity and accumulation, as they do for doxorubicin, we conclude that the better efficiency of lipophilic anthracyclines is likely to be due to their high uptake rate rather than to a decreased activity of P-glycoprotein on these drug substrates.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1997

Glucuronidation of SN-38, the active metabolite of irinotecan, by human hepatic microsomes.

We have investigated the glucuronidation in vitro of SN-38, the active metabolite of irinotecan, a semi-synthetic anticancer drug derived from 20(S)camptothecin. Preparations of human hepatic microsomes (final concentration : 1 mg prot./ml), were incubated for 1 hr in 0.1 M Tris buffer, pH 7.4, containing 10 mM MgCl2, in the presence of UDP-glucuronic acid (4 mM), saccharolactone (4 mM), and a detergent. Microsomes from five livers were studied individually or as a pooled preparation. SN-38, either in its lactone or its carboxylate form, was added at a range of concentrations. The SN-38 beta-glucuronide formed was measured by HPLC with fluorometric detection. The glucuronidation reaction appeared linear over 1 hr in these conditions and Brij 35 at 0.5 mg/mg prot. was the best activator. The apparent parameters of the reaction were independent of the molecular form of the substrate. The half-saturation constant was 17-20 microM and Vmax was 60-75 pmol/min./mg prot. The interindividual variation of SN-38 glucuronidation was relatively low (ratio of 1.8 between extreme values). In addition, the effect of twelve drugs currently associated with irinotecan in clinics was evaluated in this system (drug concentration: 100 microM; SN-38 concentration: 5 microM). These produced little if any interference with SN-38 glucuronidation. Therefore, major interferences of this transformation by comedications are unlikely to occur in vivo.

Antineoplastic Agents, Phytogenic↗
PubMed1997

Measuring multidrug resistance expression in human malignancies: elaboration of consensus recommendations.

Before the prognostic significance of P-glycoprotein (P-gp) expression can be properly evaluated in prospective clinical trials of P-gp modulators, standard techniques for the measurement of P-gp must be widely accepted. Several multicenter trials have demonstrated large discrepancies in the observed levels of P-gp expression in the same clinical samples evaluated at different centers. The greatest discrepancies occurred with samples that expressed low levels of P-gp. Although standardized procedures have dramatically increased the interlaboratory reproducibility of flow cytometry and polymerase chain reaction assays, data from immunocytochemistry remain difficult to interpret. Consensus recommendations are presented for improving data reproducibility. These recommendations emphasize the importance of using calibrated batches of antibodies and two different antibodies for immunocytochemistry, the need for an internal standard for reverse transcriptase-polymerase chain reaction (RT-PCR) assays, the need for the presentation of data as a continuous variable, and the need for setting standard parameters for flow cytometry. It is also extremely important for the success of clinical trials that multiple techniques be employed to insure accurate measurement of P-gp expression.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1997

[The bacteriology of tuberculosis and non-tuberculosis mycobacterial infections].

Changing incidence and nature of mycobacterial infections subsequent to the historical regression of tuberculosis and the acquired human immunodeficiency syndrome (AIDS) epidemic, as well as the development of new technical tools for molecular biology, have profoundly modified the methods used for the bacteriological diagnosis of mycobacteria infections. Although microscopic search for acid-fast bacilli, culture and antibiotic resistance tests on Löwenstein-Jensen medium remain the reference methods, more rapid and sophisticated methods are now available. Culture on radiolabeled media using the Bactec system has shortened the delay for positive culture and interpretable antibiotic sensitivity tests. Molecular techniques allow: 1) rapid identification of the most frequently isolated mycobacteria strains, including the most frequent laboratory contaminant M. gordonae, with genome probes; 2) genome typing of M. tuberculosis strains to trace interhuman transmission, detect recurrence or exogenous reinfection or demonstrate laboratory contamination; 3) rapid detection of rifampicin resistance; and 4) direct detection of M. tuberculosis and M. avium in pathological specimens. The role of mycobacteria in the environment causing opportunistic infections, atypical mycobacteria or non-tuberculosis mycobacteria (NTM), particularly the aviaire complex, has grown considerably. Isolation and identification relies on methods used to detect bacilli as well as blood cultures and analysis of fecal matter. NTM are naturally resistant to most of the antituberculosis antibiotics but are sometimes sensitive to aminoglycosides, fluoroquinolones or new macrolides.

AIDS-Related Opportunistic Infections↗
PubMed1997

[Surgical resection of primary lung cancer. A 13-year experience in Geneva].

This retrospective study concerns 683 consecutive patients operated for primary non-small cell lung cancer between 1977 and 1989 (581 men and 102 women with a mean age of 60.3 years). Histology was as follows: squamous in 422 (62%), adenocarcinoma in 207 (30%), broncho-alveolar in 24 (4%) and large-cell in 30 (4%). According to the TNM classification, 304 tumors were graded as stage I (45%), 130 as stage II (19%), 157 as stage IIIA (23%), 62 as stage IIIB (9%) and 19 as stage IV (3%). Surgery consisted of lobectomies in 337 (49%), pneumonectomies in 210 (31%), segmentectomies and wedge resections in 42 (6%), bilobectomies in 41 (6%) and exploratory thoracotomies in 53 (8%). It was curative in 513 cases (75%) and palliative in 170 (25%). 49 patients died within 2 months of the operation (7.2%), while 209 suffered postoperative complications (31%). Mediastinal lymph node dissection was not routinely performed to in this series. However global outcome (30% 5 years survival and 18% at 10 years), compared favorably with that reported by centres that perform mediastinal lymphadenectomy systematically.

Actuarial Analysis↗
PubMed1997

[Protection of intrathoracic anastomosis by pleural tent methods after Ivor-Lewis esophagectomy].

PURPOSE OF THE STUDY: Description of a technical procedure to diminish the risk of spillage into the mediastinum in case of leakage from an intrathoracic anastomosis after partial esophagectomy. METHOD: In Ivor-Lewis procedures for cancer of the middle or lower third of the esophagus, the esogastric anastomosis is slipped under ther upper mediastinal pleura which is kept intact. From 1989 to 1997, this technique has been used in 43 consecutive patients (squamous carcinoma in 22, adenocarcinoma in 21). Three patients died postoperatively (7%) and complications (in 38%) were mostly pulmonary and cardiac. No anastomotic leak was detected on routine Gastrografin swallow performed on the 7th postoperative day. Three patients required dilation for stenosis. DISCUSSION AND CONCLUSION: Subpleural blanketing of intrathoracic anastomoses after esophagectomy is safe and easy to do, and should help diminish the consequences of possible anastomotic leakage.

Adult↗
PubMed1997

Cumulative pharmacokinetic study of oxaliplatin, administered every three weeks, combined with 5-fluorouracil in colorectal cancer patients.

The cumulative pharmacokinetic pattern of oxaliplatin, a new diamminecyclohexane platinum derivative, was studied in patients with metastatic colorectal cancer. Oxaliplatin was administered by i. v. infusion (130 mg/m2) over 2 h every 3 weeks, and 5-fluorouracil and leucovorin were administered weekly. A very sensitive method, inductively coupled plasma-mass spectrometry, allowed for the determination of total plasma and ultracentrifugable (UC) and RBC platinum levels on day 1, at 0, 2, and 5 h, and on days 8, 15, and 22. Sixteen patients underwent three or more courses, and six of them underwent six or more courses. The platinum concentration curves were quite similar from one course to another, with a high peak value 2 h after administration (day 1, Cmax = 3201 +/- 609 microgram/liter) and a rapid decrease (day 8, 443 +/- 99 microgram/liter). Cmax of both total and UC platinum levels in plasma remained unchanged throughout the treatment. The mean total platinum half-life in plasma was 9 days. We found residual levels of total platinum on day 22 (161 +/- 45 microgram/liter), but we observed no significant accumulation for the four first cycles (P = 0.57). In contrast, platinum accumulated significantly in RBCs after three courses (+91% at day 22 of the third cycle versus day 22 of the first cycle, P = 0.000018), and its half-life there was equivalent to that of RBCs. The patterns of UC and total platinum concentration curves were very similar and correlated significantly (P < 10(-6)) at all sampling times. The mean UC:total platinum ratio was 15% at day 1 and 5% at days 8, 15, and 22 in the 3-week treatment course. Unlike cisplatin, which rapidly accumulates in plasma as both free and bound platinum, oxaliplatin does not accumulate in plasma, but it does accumulate in RBCs, after repeated cycles at the currently recommended dose (130 mg/m2) and schedule of administration (every 3 weeks).

Adult↗
PubMed1997

Pharmacokinetic interrelationships of irinotecan (CPT-11) and its three major plasma metabolites in patients enrolled in phase I/II trials.

Irinotecan (CPT-11) is an analogue of 20(S)-camptothecin with promising activity against several tumor types. In patients, CPT-11 is metabolized to 7-ethyl-10-hydroxycamptothecin (SN-38) and to the beta-glucuronide of SN-38. Recently, we identified an additional metabolite of CPT-11, 7-ethyl-10-[4-N-(5-aminopentanoic acid)-1-piperidino] carbonyloxycamptothecin (APC; L. P. Rivory et al. , Cancer Res., 56: 3689-3694, 1996). The aim of this study was to investigate the interrelationships of all four compounds to identify factors that might be responsible for the large interpatient variability in CPT-11 and SN-38 kinetics. The plasma kinetics of CPT-11, SN-38, the beta-glucuronide of SN-38, and APC were studied in 19 patients for a total of 33 cycles (115-600 mg/m2). Although the area under the concentration curves (AUCs) of all compounds studied increased with dose, there was considerable variability. Ratios of the AUCs of the appropriate compounds were used as estimates of the major routes of metabolism (conversion of CPT-11 to SN-38, metabolism of CPT-11 to APC, and glucuronidation of SN-38). Each ratio varied more than 10-fold across the patient population, and the apparent extent of conversion of CPT-11 to SN-38 was highest at the 115 mg/m2 dose level. Interestingly, AUCSN-38 was greater in patients with both high AUCCPT-11 and AUCAPC. We conclude that the variability of the pharmacokinetics of CPT-11 and SN-38 is likely to be due to extensive interpatient differences in the pathways implicated in the metabolism of CPT-11.

Antineoplastic Agents, Phytogenic↗
PubMed1996

Relationship between the inhibition of azidopine binding to P-glycoprotein by MDR modulators and their efficiency in restoring doxorubicin intracellular accumulation.

Using three different cell lines exhibiting the MDR phenotype, we have studied the ability of eight different modulators to restore doxorubicin intracellular accumulation and to inhibit azidopine binding to membrane extracts. One cell line was of human origin (KB VI) and two of murine origin, overexpressing two different isoforms of the mdrl gene (C6 IV and C6 0.5). The modulators were distributed in different drug classes: cyclosporine A and PSC-833, quinine and quinidine, nifedipine and nicardipine, and verapamil and S-9788. We observed that there was no strict parallelism between restoration of doxorubicin intracellular accumulation and inhibition of azidopine binding. However, when considering separately each group of drugs, it appeared that the most potent drug in inhibiting azidopine labelling of P-glycoprotein (P-gp) was also the most potent in restoring doxorubicin accumulation. This indicates that azidopine binding cannot be used as a general screening test for the identification of new modulators, but rather at the level of the selection of potent analogues within a chemical family. The three cell lines behaved similarly, indicating that the structural diversity of P-pgs did not influence the efficiency and binding of modulators.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1996

Conversion of irinotecan (CPT-11) to its active metabolite, 7-ethyl-10-hydroxycamptothecin (SN-38), by human liver carboxylesterase.

We have investigated the conversion of the novel anti-topoisomerase I agent CPT-11 (irinotecan; 7-ethyl-10[4-(1-piperidino)-1-piperidno]carbonyloxycamptothecin ) to its active metabolite, SN-38 (7-ethyl-10-hydroxycamptothecin), by human liver carboxylesterase (HLC). Production of SN-38 was relatively inefficient and was enzyme deacylation rate-limited with a steady-state phase occurring after 15-20 min of incubation. This later phase followed Michaelis-Menten kinetics with an apparent Km of 52.9 +/- 5.9 microM and a specific activity of 200 +/- 10 mumol/sec/mol. However, the total enzyme concentration estimated from the intercept concentrations of SN-38 was much lower than that estimated directly from the titration of active sites with paraoxon (0.65 vs. 2.0 microM, respectively). Because deacylation rate-limiting kinetics result in the accumulation of inactive acyl-enzyme complex, we postulated that incubation of CPT-11 with HLC would result in an inhibition of the HLC-catalysed hydrolysis of p-nitrophenylacetate (p-NPA), an excellent substrate for this enzyme. Indeed, this was found to be the case although complete inhibition could not be attained. Analysis of possible kinetic schemes revealed that the most likely explanation for the disparity in estimated enzyme concentrations and the incomplete inhibition of p-NPA hydrolysis is that CPT-11 also interacts at a modulator site on the enzyme, which profoundly reduces substrate hydrolysis. Furthermore, loperamide, a drug often used for the treatment of CPT-11-associated diarrhea, was found to inhibit both CPT-11 and p-NPA HLC-catalysed hydrolysis, most likely by a similar interaction. These observations have direct implications for the clinical use of CPT-11.

Antineoplastic Agents, Phytogenic↗
PubMed1996

Identification and properties of a major plasma metabolite of irinotecan (CPT-11) isolated from the plasma of patients.

Irinotecan [7-ethyl-10-[4-(1-piperidino)-1-piperidino]carbonyloxycamptothecin (CPT-11)] is a promising water-soluble analogue of camptothecin [S. Sawada et al., Chem. & Pharm. Bull. (Tokyo), 39: 1446-1454, 1991]. We have reported previously the presence of an important polar metabolite, in addition to 7-ethyl-10-hydroxycamptothecin (SN-38) beta-glucuronide, in samples of plasma taken from patients undergoing treatment with CPT-11 (L.P. Rivory and J. Robert, Cancer Chemother. Pharmacol. 36: 176-179, 1995; L. P. Rivory and J. Robert, J. Cromatogr., 661: 133-141, 1994). Plasma samples (0.5 ml) containing comparatively large amounts of this metabolite were extracted by solid-phase columns and subjected to high-performance liquid chromatography and mass spectrometry in parallel to fluorometric detection. The metabolite yielded [M + 1] ions with a m/z of 619, representing the addition of 32 atomic mass units to CPT-11. Purified fractions were subjected to proton nuclear magnetic resonance, and the structure determined, 7-ethyl-10-[4-N-(5-aminopentanoic acid)-1-piperidino]carbonyloxycampothecin (APC), was further validated following synthesis. Like CPT-11, APC was found to be only a weak inhibitor of the cell growth of KB cells in culture (IC50, 2.1 versus 5.5 micrograms/ml for CPT-11 and 0.01 microgram/ml for SN-38, the active metabolite of CPT-11) and was a poor inducer of topoisomerase I DNA-cleavable complexes (100-fold less potent than SN-38). In contrast to CPT-11, APC was not hydrolyzed to SN-38 by human liver microsomes or purified human liver carboxylesterase. Furthermore, APC did not inhibit the hydrolysis of CPT-11 in these preparations. Interestingly, APC was only a weak inhibitor of acetylcholinesterase in comparison to CPT-11 and neostigmine. It appears likely, therefore, that APC does not contribute directly to the activity and toxicity profile of CPT-11 in vivo.

Antineoplastic Agents, Phytogenic↗
PubMed1996

Crystalline Ropes of Metallic Carbon Nanotubes

Fullerene single-wall nanotubes (SWNTs) were produced in yields of more than 70 percent by condensation of a laser-vaporized carbon-nickel-cobalt mixture at 1200degreesC. X-ray diffraction and electron microscopy showed that these SWNTs are nearly uniform in diameter and that they self-organize into "ropes," which consist of 100 to 500 SWNTs in a two-dimensional triangular lattice with a lattice constant of 17 angstroms. The x-ray form factor is consistent with that of uniformly charged cylinders 13.8 +/- 0.2 angstroms in diameter. The ropes were metallic, with a single-rope resistivity of <10(-4) ohm-centimeters at 300 kelvin. The uniformity of SWNT diameter is attributed to the efficient annealing of an initial fullerene tubelet kept open by a few metal atoms; the optimum diameter is determined by competition between the strain energy of curvature of the graphene sheet and the dangling-bond energy of the open edge, where growth occurs. These factors strongly favor the metallic (10,10) tube with C5v symmetry and an open edge stabilized by triple bonds.

Journal Article↗