Biomedical subjects

Bertrand Pourroy

Publications and source records attributed to Bertrand Pourroy.

10 recordsLinked to original sources

PubMed2006

Antiangiogenic concentrations of vinflunine increase the interphase microtubule dynamics and decrease the motility of endothelial cells.

Angiogenesis is a key event in tumor progression and metastasis. This complex process, which constitutes a potent target for cancer therapy, is inhibited by very low concentrations of microtubule-targeting drugs (MTD). However, the intimate mechanisms of the antiangiogenic activity of MTDs remain unclear. Recently, we have shown that low antiangiogenic and noncytotoxic concentrations of paclitaxel induced an unexpected increase in microtubule dynamics in endothelial cells. In this study, we showed that vinflunine, the newest Vinca alkaloid, increased microtubule dynamic instability in human endothelial cells after 4-hour incubation at low concentrations (29% and 54% at 0.1 and 2 nmol/L). The growth and shortening rates were increased, and the percentage of time spent in pause and the mean duration of pauses were decreased, as previously observed with paclitaxel. As opposed to paclitaxel, the transition frequencies were not significantly disturbed by vinflunine. Moreover, low concentrations of vinflunine did not affect mitotic index and anaphase/metaphase ratio. Interestingly, these low vinflunine concentrations that increased microtubule dynamics exhibited an antiangiogenic effect through the inhibition of both morphogenesis and random motility. Capillary tube formation on Matrigel was decreased up to 44%. The cell speed and the random motility coefficient were decreased (13% and 19% and 13% and 33% at 0.1 and 2 nmol/L, respectively) and the persistent time was statistically increased. Altogether, our results confirm that the increase in microtubule dynamics is involved in MTD antiangiogenic activity and highlight the crucial role of interphase microtubule dynamics in angiogenesis.

Angiogenesis Inhibitors↗

PubMed2006

Decrease in c-Myc activity enhances cancer cell sensitivity to vinblastine.

The c-myc oncogene encodes for a transcriptional factor involved in many cellular processes such as proliferation, differentiation and apoptosis. According to these different functions, the role of c-Myc protein in cellular sensitivity to anti-cancer drugs is controversial. We defined the role of c-Myc in cancer cell sensitivity to vinblastine (VLB) using human colon cancer cells: LoVo wild-type or transfected with a plasmid containing the human c-myc gene in antisense orientation (LoVo-mycANS). Analysis of VLB cytotoxicity demonstrated a 3-fold increase in VLB sensitivity in LoVo-mycANS cells. Comparison between cells revealed different apoptosis kinetics: accumulation of cells in sub-G1 phase and poly(ADP-ribose) polymerase cleavage occurred earlier in LoVo-mycANS. Then, we demonstrated a mitochondrial membrane potential disruption followed by cytochrome c release that indicates the involvement of mitochondria in this apoptotic signaling pathway. This earlier apoptosis was accompanied by a Bcl-2 decrease and a p53 increase. In conclusion, the decrease in c-Myc expression enhanced the VLB sensitivity, triggering earlier apoptosis through induction of the intrinsic pathway. Thus, c-myc induction is a resistance factor and our findings suggest that tumors carrying low levels of c-Myc protein could be more responsive to vinca alkaloids treatment. Moreover, the downregulation of c-myc oncogene by an antisense strategy might represent a useful goal for improving the efficacy of this anti-neoplastic drug family.

Adenocarcinoma↗

PubMed2006

Therapeutic drug monitoring for dose individualization of Cisplatin in testicular cancer patients based upon total platinum measurement in plasma.

Cisplatin (CDDP) is an anticancer agent widely used in testicular cancer, for which pharmacokinetic (PK)/pharmacodynamic relationships have usually been based upon measurement of its unbound fraction in plasma. Because it has been shown that free CDDP clearance can be related to patient's body surface area (BSA), dosage is mostly adjusted a priori using only this single parameter, with mixed results for accurately predicting CDDP exposure and reducing toxicities. In contrast, the authors present here an original, 5-day continuous infusion schedule, coupled to a daily Bayesian adaptive dosing with feedback strategy, based upon the rapid assay of total, rather than free, CDDP in plasma. Nineteen patients (66 therapeutic courses) were treated with platinum-based combinational therapy. Plasma samples were analyzed to allow real-time Bayesian estimation of individual PK parameters with subsequent prospective dose adjustment in order to reach a target Cmax (Cend) of 1.95 mg/L of total platinum. Performance of the Bayesian dosing method was evaluated by comparing target Cmax with achieved Cmax. The mean+/-SD Cmax achieved was 1.93+/-0.16 mg/L. No statistically significant difference was observed between experimental and target values (P>0.05, t test), and Cend achievement was done with an overall 6.6% precision, a performance to be compared with the initial 54% interpatient variability observed in CDDP clearance. A nonlinear mixed effect model population PK analysis was subsequently performed to identify retrospectively the covariates associated with PK parameters of total CDDP. It showed a good correlation (r=0.84, P=0.004) between total platinum clearance and therapeutic course number. A weaker correlation (r=0.59) was found between BSA and total CDDP clearance and, importantly, no additional relationship was established with BSA when successive therapeutic courses, and not only the first one, were considered. This highlights the critical importance of total drug accumulation on CDDP pharmacokinetics when several infusions are to be administered in a row and, therefore, the need for real-time dose individualization that takes into account the course number, rather than BSA. Finally, doses of CDDP administered during each course were significantly higher (+20%, P<0.01) than the ones classically normalized with BSA, thus leading to an overall greater drug exposure in the patients. It is noteworthy that despite these markedly higher doses, little severe toxicity was reported, and all of the patients presented in this study were still alive and disease free after a follow-up of up to 15 years.

Adult↗

PubMed2006

Efficacy of a combination of pemetrexed and multiple redo-surgery in an 11-year-old girl with a recurrent multifocal abdominal mesothelioma.

We report the case of an 11-year-old girl with a recurrent progressive locally advanced abdominal mesothelioma. First, there was an incomplete surgical resection without any complementary chemotherapy, followed by a slow progression of the disease. Three years later, after two macroscopically complete surgical resections of peritoneal and ovarian tumors, she failed to respond to treatment with gemcitabin-carboplatin and gemcitabin-cisplatin, and developed splenic tumors and large multicystic hepatic tumors. She was then treated with pemetrexed. The schedule of chemotherapy was pemetrexed 400 mg intravenously plus cisplatin 60 mg once every 3 weeks associated with folic acid and vitamin B12. The tumor reduction was evaluated with positron emission tomography scan and tomodensitometry every three courses. Chemotherapy tolerance was good apart from a grade III neutropenia at the second course, a fever of unknown origin at the fifth course and a grade III thrombocytopenia at the sixth course. As tolerance and clinical responses were good, pemetrexed posology was increased up to 10%. After six courses, hepatic and splenic lesion tumors were initially diminished and then stablilized. Thus, a surgical resection was attempted: a first surgery followed by a second one 3 days later allowed completion of a difficult left hepatectomy, and resection of the hilum and splenic tumors. Fourteen months after the surgery, the girl remained in partial remission with stable disease. So far, pemetrexed associated with cisplatin revealed a good tolerance and promising results regarding its antitumoral efficacy in a progressive metastatic abdominal mesothelioma in childhood.

Abdominal Neoplasms↗

PubMed2006

Dose individualization of carboplatin after a 120-hour infusion schedule: higher dose intensity but fewer toxicities.

Carboplatin (CBDCA) is a widely used anticancer agent for which dose-effect and dose-toxicity relationships have been demonstrated, thus stressing the need for a controlled exposure to this drug. So far, carboplatin administration could only be individualized a priori following 2 classic methods, which are based on the evaluation of renal clearance: Calvert's and Chatelut's formulas. This study was designed to develop and evaluate the performance of an alternative CBDCA 120-hour schedule coupled to a Bayesian adaptive dosing with feedback strategy. Precision of the dosing method was assessed in 84 patients (256 courses performed during a 10-year period), by comparing CBDCA plasma concentrations observed at the end of the infusion with initial target values. A comprehensive monitoring of treatment-related toxicities also was performed. Finally, the authors compared doses actually delivered following the dose-tailoring method with the theoretical, standard, ones calculated retrospectively with Calvert's and Chatelut's formulas. No significant differences were found between experimental and theoretical concentrations. According to the target exposure chosen (3 levels), the mean doses administered to our patients were 517, 719, and 902 mg of CBDCA compared with 550, 509, and 538 or 657, 604, and 644 mg, which would have been given following Calvert or Chatelut formulas, respectively. These results showed that our Bayesian method led to the administration of up to 60% higher doses of carboplatin compared with those based only on the evaluation of renal clearance. Despite the markedly higher doses administered, no severe toxicities were reported in the patients treated following this new schedule. It is noteworthy that neither hematologic growth factors nor stem cells, usually associated with high-dose regimen, were used as support in this study. These data strongly suggest that it is possible to deliver higher dose- intensities of carboplatin, even in elderly, unselected patients, without increasing toxicities and with no growth factor support, provided that a therapeutic drug monitoring strategy with real-time tailored dosing is performed.

Aged↗

PubMed2005

Antiangiogenic concentrations of paclitaxel induce an increase in microtubule dynamics in endothelial cells but not in cancer cells.

Microtubule-targeted drugs such as paclitaxel exhibit potent antiangiogenic activity at very low concentrations, but the mechanism underlying such an effect remains unknown. To understand the involvement of microtubules in angiogenesis, we analyzed the dynamic instability behavior of microtubules in living endothelial cells [human microvascular endothelial cells (HMEC-1) and human umbilical vascular endothelial cells (HUVEC)] following 4 hours of paclitaxel treatment. Unexpectedly, antiangiogenic concentrations of paclitaxel (0.1-5 nmol/L) strongly increased microtubule overall dynamicity in both HMEC-1 (86-193%) and HUVEC (54-83%). This increase was associated with increased microtubule growth and shortening rates and extents and decreased mean duration of pauses. The enhancement of microtubule dynamics by paclitaxel seemed to be specific to antiangiogenic concentrations and to endothelial cells. Indeed, cytotoxic concentration (100 nmol/L) of paclitaxel suppressed microtubule dynamics by 40% and 54% in HMEC-1 and HUVECs, respectively, as observed for all tested concentrations in A549 tumor cells. After 4 hours of drug incubation, antiangiogenic concentrations of paclitaxel that inhibited endothelial cell proliferation without apoptosis (1-5 nmol/L) induced a slight decrease in anaphase/metaphase ratio, which was more pronounced and associated with increased mitotic index after 24 hours of incubation. Interestingly, the in vitro antiangiogenic effect also occurred at 0.1 nmol/L paclitaxel, a concentration that did not alter mitotic progression and endothelial cell proliferation but was sufficient to increase interphase microtubule dynamics. Altogether, our results show that paclitaxel mediates antiangiogenesis by an increase in microtubule dynamics in living endothelial cells and suggest that the impairment of interphase microtubule functions is responsible for the inhibition of angiogenesis.

Angiogenesis Inhibitors↗

PubMed2005

[Oxaliplatin neurotoxicity: a report of three cases with post-operative exacerbation].

Liver metastases of colorectal cancer are rarely rapidly resectable. The efficacy of new chemotherapy regimen, in particular the combination of 5FU and oxaliplatin make further surgical resection possible in the case of an objective response in some patients. Three patients with metastatic colorectal cancer received oxaliplatin-based chemotherapy; only minimal and transient neurosensory toxicity occurred. After a partial response to treatment, surgical resection of metastases was performed. Patients reported major exacerbation of oxaliplatin-induced neurosensory toxicity following surgery (between day 7 and day 15). One patient experienced sensory loss of the extremities with functional impairment (grade 3 on Levi's scale). The symptoms persisted for 812 months after surgery in the three patients. Only seven similar cases have been reported. Toxicity could be associated with the concentration of oxaliplatin in the red blood cells: oxaliplatin binds irreversibly to erythrocytes. This exacerbation could be the consequence of peroperative hemolysis with a redistribution of the pool of intra-erythrocytic oxaliplatin biotransformation products into the plasma. We did not find any relationship with anesthesic or per-operative medications. Studies are necessary to define the precise mechanism and the frequency of this reaction.

Aged↗

PubMed2004

Agonist-induced internalization of leukotriene B(4) receptor 1 requires G-protein-coupled receptor kinase 2 but not arrestins.

The leukotriene B(4) (LTB(4)) receptor (BLT1) becomes desensitized upon repeated agonist stimulation. Little is known, however, about BLT1 internalization, which follows desensitization in most G-protein-coupled receptors (GPCR). In the current study, transiently expressed BLT1 readily internalized, after LTB(4) stimulation, in RBL-2H3 cells that express high levels of endogenous GPCR kinase 2 (GRK2) but did not in COS-7 or human embryonic kidney (HEK) 293 cells, which do not overexpress GRK. The internalization of BLT1 could be blocked in RBL-2H3 cells by coexpressing dominant-negative (DN) GRK2 K220R and could be promoted in HEK293 cells by coexpressing wild-type (WT) GRK2. Coexpression of WT or DN nonvisual arrestins had no effect on BLT1 internalization. Moreover, upon stimulation with LTB(4), BLT1 did not induce arrestin-green fluorescence protein redistribution in either cell type, even in the presence of overexpressed GRK2. Coimmunoprecipitation experiments confirmed that BLT1 could associate with GRK2 but not with arrestins. A C-tail-truncated mutant of BLT1 lost the capacity to internalize and associate with GRK2 upon exposure to LTB(4), suggesting that the C-tail was required for receptor internalization and association with GRK2. Taken together, our results indicate that the C terminus of BLT1 plays a pivotal role in receptor internalization and GRK2 association. Moreover, ligand-induced BLT1 internalization is dependent on GRK2 but independent of arrestins. This may allow differential, cell-type-specific signaling in response to LTB(4), depending on GRK expression levels.

Animals↗

PubMed2004

Antiangiogenic activity of paclitaxel is associated with its cytostatic effect, mediated by the initiation but not completion of a mitochondrial apoptotic signaling pathway.

Angiogenesis is a critical event in tumor growth and metastasis, which can be inhibited by conventional anticancer drugs such as the microtubule-damaging agent paclitaxel (Taxol). In this study, we investigate the mechanism of action of paclitaxel on human endothelial cells. We characterize two distinct effects of paclitaxel on human umbilical vein endothelial cell and human microvascular endothelial cell-1 proliferation according to drug concentration: a cytostatic effect at low concentrations and a cytotoxic effect at concentrations > or =10 nmol/L. The cytotoxic effect involves signaling pathways similar to those described in tumor cells (i.e., microtubule network disturbance, G(2)-M arrest, increase in Bax/Bcl-2 ratio, and mitochondria permeabilization) that result in apoptosis. In sharp contrast, the cytostatic effect involves an inhibition of endothelial cell proliferation without apoptosis induction and without any structural modification of the microtubule network. This cytostatic effect is due to a slowing of the cell cycle rather than to an arrest in a specific phase of the cell cycle. In addition, paclitaxel, at cytostatic concentrations, early initiates an apoptotic signaling pathway associated with increases in the mitochondrial reducing potential, mitochondrial membrane potential, p53 expression, and Bax/Bcl-2 ratio. However, this apoptotic pathway is stopped upstream of mitochondria permeabilization and it does not lead to endothelial cell death. Finally, we found that paclitaxel inhibits endothelial cell morphogenesis on Matrigel at all tested concentrations. In conclusion, we describe the mechanism of action of low concentrations of paclitaxel related to the antiangiogenic properties of this drug.

Angiogenesis Inhibitors↗

PubMed2002

Paclitaxel targets mitochondria upstream of caspase activation in intact human neuroblastoma cells.

We previously reported that paclitaxel acted directly on mitochondria isolated from human neuroblastoma SK-N-SH cells. Here, we demonstrate that the direct mitochondrial effect of paclitaxel observed in vitro is relevant in intact SK-N-SH cells. After a 2 h incubation with 1 microM paclitaxel, the mitochondria were less condensed. Paclitaxel (1 microM, 1-4 h) also induced a 20% increase in respiration rate and a caspase-independent production of reactive oxygen species by mitochondria. The paclitaxel-induced release of cytochrome c was detected only after 24 h of incubation, was caspase-independent and permeability transition pore-dependent. Thus, paclitaxel targets mitochondria upstream of caspase activation, early during the apoptotic process in intact human neuroblastoma cells.

Antineoplastic Agents, Phytogenic↗