Biomedical subjects

D Braguer

Publications and source records attributed to D Braguer.

At least 19 recordsLinked to original sources

PubMed2005

Temozolomide in combination with BCNU before and after radiotherapy in patients with inoperable newly diagnosed glioblastoma multiforme.

BACKGROUND: The aim of this study was to evaluate the efficacy and safety of carmustine (BCNU) in combination with temozolomide as first-line chemotherapy before and after radiotherapy (RT) in patients with inoperable, newly diagnosed glioblastoma multiforme (GBM). PATIENTS AND METHODS: Forty patients were treated with BCNU (150 mg/m2) on day 1 and temozolomide (110 mg/m2/day) on days 1 through 5 of each 42-day cycle for up to four cycles prior to conventional RT (2 Gy fractions to a total of 60 Gy). After RT, BCNU + temozolomide was administered for four additional cycles or until progression. The primary end point was response rate; secondary end points included progression-free survival (PFS); overall survival (OS) and safety. RESULTS: Sixty per cent of patients completed four cycles of neo-adjuvant BCNU + temozolomide. Objective response rate (intention-to-treat) was 42.5% (95% confidence interval 27% to 58%), including two (5%) complete and 15 (37.5%) partial responses. In the eligible population (n=37) the objective response rate was 46%. Nine (24%) patients had stable disease and 14 (35%) had progressive disease. Median PFS and OS were 7.4 and 12.7 months, respectively. Age was the only significant prognostic factor and tumor location (lobar versus multifocal versus corpus callosum) showed a trend. Grade 3-4 toxicities included thrombocytopenia (n=11) and neutropenia (n=7) for both pre- and post-RT chemotherapy. Four patients required platelet transfusions. No patient discontinued treatment because of toxicity. CONCLUSIONS: The combination of BCNU plus temozolomide as neo-adjuvant therapy in inoperable GBM exhibited promising activity with a good safety profile and warrants further evaluation.

Adult↗

PubMed2005

Understanding microtubule dynamics for improved cancer therapy.

Microtubules (MTs), key components of the cytoskeleton, are dynamic polymers of tubulin that form a well-organized network of polarized tube filaments. MT dynamics are highly regulated both spacially and temporally by several MT-related proteins, themselves regulated by several kinases and phosphatases via signaling cascades, and also by coordinated interactions with actin cytoskeleton and adhesion sites. Regulation of MT dynamics is crucial for mitosis, cell migration, cell signaling and trafficking. MT-targeted drugs (MTDs), which constitute a major anticancer drug family with antimitotic and antiangiogenic properties, inhibit tumor progression mainly by altering MT dynamics in both cancer and endothelial cells. Identification of proteins regulating the MT network will lead to a better understanding of tumor progression regulators and will be helpful in improving cancer therapy.

Animals↗

PubMed2005

Seventy-two-hour stability of Taxol in 5% dextrose or 0.9% sodium chloride in Viaflo, Freeflex, Ecoflac and Macoflex N non-PVC bags.

BACKGROUND AND OBJECTIVES: Taxol (paclitaxel), is an antimicrotubule agent widely prescribed for the treatment of many tumoral diseases. Taxol must be used in non-polyvinyl chloride bags, diluted to concentrations of 0.3-1.2 mg/mL in 5% dextrose or in 0.9% sodium chloride. Under these conditions, Taxol is chemically and physically stable for 27 h at 25 degrees C. The aim of the study was to evaluate the 72-h stability of Taxol under common clinical use conditions. METHODS: Taxol was diluted with 5% dextrose and 0.9% sodium chloride to final concentrations of 0.3 and 1.2 mg/mL in four polyolefin bags (Viaflo, Freeflex, Ecoflac and Macoflex N). Taxol-stability, was assessed by turbidimetry and by high-performance liquid chromatography using solutions stored in the dark, over 72 h at +4 degrees C. RESULTS: No haze, turbidity, or precipitate was observed. Paclitaxel concentration remained above 95% of the initial value whatever the solvent or container used. CONCLUSION: Paclitaxel at 0.3 and 1.2 mg/mL in 5% dextrose and in 0.9% sodium chloride is stable in Viaflo, Freeflex, Ecoflac and Macoflex N non-PVC bags for 72 h in the dark at +4 degrees C. The longer stability should make the use of Taxol in clinical practice easier.

Antineoplastic Agents, Phytogenic↗

PubMed2004

Phase II study of temozolomide without radiotherapy in newly diagnosed glioblastoma multiforme in an elderly populations.

BACKGROUND: Currently, the survival of patients age > 70 years with glioblastoma multiforme (GBM) ranges from 4 months to 6 months, although radiotherapy and/or chemotherapy may prolong survival in certain subgroups. Temozolomide is an oral chemotherapeutic agent with efficacy against malignant gliomas and a favorable safety profile. This open-label, single-center, Phase II study was designed to evaluate the efficacy and safety of temozolomide as first-line chemotherapy and exclusive treatment in elderly patients with newly diagnosed GBM. METHODS: Chemotherapy-naïve patients (age > 70 years) were treated with temozolomide at a dose of 150-200 mg/m(2) per day for 5 consecutive days of a 28-day cycle until they developed disease progression. No radiation therapy was administered. The primary endpoint was median overall survival (OS); secondary endpoints included progression-free survival (PFS) and toxicity. RESULTS: Thirty-two patients (median age, 75 years; median Karnofsky performance status, 70) experienced a median OS of 6.4 months and a median PFS of 5.0 months. Of 29 patients who were assessed for response, 9 patients (31%) achieved a partial response, 12 patients (41%) maintained stable disease, and 8 patients (28%) developed progressive disease. Adverse events primarily were mild, with NCI CTC Grade 3-4 thrombocytopenia and neutropenia reported to occur in 6% and 9% of patients, respectively. No neurotoxicity was observed. Treatment delays and dose reductions occurred in 13% and 14% of cycles, respectively. CONCLUSIONS: Temozolomide represents a safe, easily administered, and effective therapeutic approach for elderly patients with newly diagnosed GBM.

Aged↗

PubMed2001

Resistance to Taxol in lung cancer cells associated with increased microtubule dynamics.

Microtubule dynamics are crucial for mitotic spindle assembly and chromosome movement. Suppression of dynamics by Taxol appears responsible for the drug's potent ability to inhibit mitosis and cell proliferation. Although Taxol is an important chemotherapeutic agent, development of resistance limits its efficacy. To examine the role of microtubule dynamics in Taxol resistance, we measured the dynamic instability of individual rhodamine-labeled microtubules in Taxol-sensitive and -resistant living human cancer cells. Taxol-resistant A549-T12 and -T24 cell lines were selected from a human lung carcinoma cell line, A549. They are, respectively, 9- and 17-fold resistant to Taxol and require low concentrations of Taxol for proliferation. We found that microtubule dynamic instability was significantly increased in the Taxol-resistant cells. For example, with A549-T12 cells in the absence of added Taxol, microtubule dynamicity increased 57% as compared with A549 cells. The length and rate of shortening excursions increased 75 and 59%, respectively. These parameters were further increased in A549-T24 cells, with overall dynamicity increasing by 167% compared with parental cells. Thus, the decreased Taxol-sensitivity of these cells can be explained by their increased microtubule dynamics. When grown without Taxol, A549-T12 cells were blocked at the metaphase/anaphase transition and displayed abnormal mitotic spindles with uncongressed chromosomes. In the presence of 2-12 nM Taxol, the cells grew normally, suggesting that mitotic block resulted from excessive microtubule dynamics. These results indicate that microtubule dynamics play an important role in Taxol resistance, and that both excessively rapid dynamics and suppressed dynamics impair mitotic spindle function and inhibit proliferation.

Antineoplastic Agents, Phytogenic↗

PubMed2001

Safety and efficacy of temozolomide in patients with recurrent anaplastic oligodendrogliomas after standard radiotherapy and chemotherapy.

PURPOSE: Most primary oligodendrogliomas and mixed gliomas (oligoastrocytoma) respond to treatment with procarbazine, lomustine, and vincristine (PCV), with response rates of approximately 80%. However, limited data on second-line treatments are available in patients with recurrent tumors. A novel second-generation alkylating agent, temozolomide, has recently demonstrated efficacy and safety in patients with recurrent glioblastoma multiforme and anaplastic astrocytoma. This study describes the effects of temozolomide in patients with recurrent anaplastic oligodendroglioma (AO) and anaplastic mixed oligoastrocytoma (AOA). PATIENTS AND METHODS: Forty-eight patients with histologically confirmed AO or AOA who had received previous PCV chemotherapy were treated with temozolomide (150 to 200 mg/m2/d for 5 days per 28-day cycle). The primary end point was objective response. Secondary end points included progression-free survival (PFS), time to progression, overall survival (OS), safety, and tolerability. RESULTS: Eight patients (16.7%) experienced a complete response, 13 patients (27.1%) experienced a partial response (objective response rate, 43.8%), and 19 patients (39.6%) experienced stable disease. For the entire treatment group, median PFS was 6.7 months and median OS was 10 months. For objective responders, median PFS was 13.1 months and median OS was 16 months. For complete responders, PFS was more than 11. 8 months and OS was more than 26 months. Response correlated with improved survival. Temozolomide was safe and well tolerated. Twelve patients developed grade 1/2 thrombocytopenia and three patients developed grade 3/4 thrombocytopenia. CONCLUSION: Temozolomide is safe and effective in the treatment of recurrent AO and AOA.

Adult↗

PubMed2001

Hyperphosphorylation of tau is mediated by ERK activation during anticancer drug-induced apoptosis in neuroblastoma cells.

Phosphorylated tau protein is the major component of paired helical filaments in Alzheimer disease (AD). We have previously shown that abnormal tau phosphorylation was induced in neuroblastoma SK-N-SH cells by the anticancer drug, paclitaxel, during apoptosis [Guise et al., 1999: Apoptosis 4:47-58]. In the present study, we first demonstrated a shift from fetal tau to hyperphosphorylated tau after incubation with paclitaxel, that showed some similarities with the hyperphosphorylated tau in AD, by using several tau antibodies, N-Term, Tau-1 and AT-8. Tau phosphorylation occurred independently of caspase-3 activation. We next showed that a sustained activation of ERK (extracellular signal-regulated kinase) induced both tau phosphorylation and apoptosis during paclitaxel treatment (1 microM). The inhibition of ERK activation by using the pharmacological MEK1/2 inhibitor, PD98059 (50 microM), or an antisense strategy, reduced tau phosphorylation and neuronal apoptosis (P < 0.001), indicating a link between ERK activation, tau phosphorylation and apoptosis. Doxorubicin (0.2 microM), an anticancer drug whose mechanism of action is independent of microtubules, also induced ERK activation, tau phosphorylation and apoptosis. Moreover, doxorubicin induced some morphological features of neurodegeneration such as loss of neurites and disorganization of the cytoskeleton in apoptotic neuroblastoma cells. Altogether, our results suggest that tau phosphorylation plays a significant role in apoptosis enhancing disruption of microtubules that in turn leads to formation of apoptotic bodies, suggesting that neurodegeneration and apoptosis are related.

Alzheimer Disease↗

PubMed2001

Involvement of nuclear factor kappaB in c-Myc induction by tubulin polymerization inhibitors.

We showed previously that microtubule disassembly by vinblastine induces the proto-oncogene c-myc in epithelial mammary HBL100 cells. In this study, we demonstrate that vinblastine treatment in these cells, in contrast to what was observed with the colon adenocarcinoma cell line HT29-D4, activated the transcription factor NFkappaB, which has been involved in c-myc regulation. The microtubule disassembly also induced IkappaB degradation. Using transient transfection analysis, we show that the trans-activation of c-myc by vinblastine was decreased when NFkappaB binding sites on c-myc promoter were mutated. Additionally, we demonstrate that microtubule dissolution trans-activated a thymidine kinase-CAT construct containing an NFkappaB binding site at -1180 to -1080 bp relative to the P1 promoter. Thus, vinblastine up-regulates the enhancer activity of the NFkappaB binding site. These results suggest that microtubule disassembly induced by vinblastine can trans-activate the c-myc oncogene through NFkappaB. Taking into consideration the paradoxical roles of both c-myc and NFkappaB in proliferation or apoptosis, this data reveals the complex action mechanism of this microtubule interfering agent.

Antineoplastic Agents, Phytogenic↗

PubMed2000

Caspase-8 activation independent of CD95/CD95-L interaction during paclitaxel-induced apoptosis in human colon cancer cells (HT29-D4).

Antimicrotubule agent-induced apoptosis was examined in the proliferating human colon cancer cell line HT29-D4. G2/M arrest and subsequent apoptosis were dose-dependent, both observed with 100 nM paclitaxel or docetaxel and 10 nM vinorelbine. Bcl-x(L) phosphorylation was observed simultaneously with mitotic block, then caspase-3 cleavage and poly(ADP-ribose) polymerase degradation were detected 48 hr later. By using both enzymatic assay and immunoblot detection of cleaved fragments, we showed that caspase-8, a central component of the CD95-induced apoptotic pathway, was significantly activated during paclitaxel exposure, contemporary to apoptosis occurrence. Caspase-8 activation and apoptosis were independent of CD95 ligation and evidenced only for concentrations inducing Bcl-x(L) phosphorylation and a decrease in mitochondria permeability. Similar results were obtained with docetaxel and vinca alkaloids. Thus, antimitotic drugs may induce apoptosis via caspase-8 activation independently of CD95/CD95-L. Caspase-8 may be a common mediator of anticancer drug-induced apoptosis that could represent a promising target for future therapies.

Antineoplastic Agents, Phytogenic↗

PubMed2000

Paclitaxel induces release of cytochrome c from mitochondria isolated from human neuroblastoma cells'.

Paclitaxel is an antimicrotubule agent that induces mitotic block and apoptosis. We show for the first time that paclitaxel acts directly or mitochondria isolated from human cancer cells. In isolated yeast mito chondria, paclitaxel (15 microM) induced an 18% increase in the respiration rate, with no concomitant release of cytochrome c. In isolated neuroblas toma mitochondria, paclitaxel (10-100 microM) induced a 27-72% release o cytochrome c. Release was prevented by cyclosporin A, suggesting the involvement of the permeability transition pore. Doxorubicin did no induce cytochrome c release, whereas vinorelbine, another antimicrotu bule agent, did. Thus, antimicrotubule agents can directly affect mito chondria to induce apoptosis.

Antibiotics, Antineoplastic↗

PubMed2000

Ribavirin-induced resistance to heat shock, inhibition of the Ras-Raf-1 pathway and arrest in G(1).

Ribavirin [1-(beta-D-ribofuranosyl)1,2,4-triazole-3-carboxamide (virazole)], a specific inhibitor of inositide 5'-monophosphate dehydrogenase (IMPDH), induces a strong depletion of GTP pools in IGR39 cells. After a 3-day treatment, the cell cycle was reversibly arrested in G(0)/G(1), suggesting the involvement of GTP in the cell cycle process. The reduction of the GTP cell content modified the appearance of the microtubule network, as examined using immunofluorescence. However, the dynamics of repolymerisation were not altered. When arrested in G(0)/G(1), cells displayed a surprising resistance to a 3-h period of heat shock at 45 degrees C. Considering the lack of coimmunoprecipitation of p21ras with Raf-1, the reduction of the level of GTP-associated p21ras and the decrease of the activation of the extracellular signal-regulated protein kinases (ERK), also known as mitogen-activated protein (MAP) kinase, in ribavirin-treated cells, we suggest a possible relationship between the expression of heat-shock proteins and the change, in GTP-depleted cells, of the regulation of Raf kinase by ras protein.

Antimetabolites↗

PubMed2000

Opposite effects of antimicrotubule agents on c-myc oncogene expression depending on the cell lines used.

We investigated the expression of c-myc in HT29-D4, HBL100 and Caco-2 cells treated with microtubule stabilising (paclitaxel) or depolymerising agents (vinblastine, nocodazole). After induction by epidermal growth factor (EGF), c-myc expression decreased in HT29-D4 cells treated with all the antimicrotubule agents. In HBL100 and Caco-2, when microtubules were stabilised with paclitaxel, c-myc expression also decreased. In contrast, its expression increased after treatment with depolymerising agents. In both cell lines, we also observed that depolymerising agents alone induced c-myc expression whilst paclitaxel had no effect. This mRNA induction was confirmed at the protein level. In HT29-D4, no variation of c-myc expression was observed. Then, we showed that the increase of mRNA level was due to activation of gene transcription. These results indicate that modulation of c-myc expression varied depending on the cell lines used and the type of antimicrotubule agents. This work provides a potential link between the microtubular network and c-myc gene expression.

Adenocarcinoma↗

PubMed1999

Tau protein is involved in the apoptotic process induced by anti-microtubule agents on neuroblastoma cells.

Paclitaxel and docetaxel are potent anti-microtubule and antimitotic agents that induce apoptosis in bone marrow-derived cells and epithelial cells. This study examined apoptosis induced by anti-microtubule agents in the neuroblastoma SK-N-SH cell line with a special focus on tau protein which is one of the main Microtubule-Associated- Proteins (MAPs) in neuronal cells. In time, treatment with 1 microM paclitaxel successively induced formation of bundles, then pseudo-asters concomitantly with mitotic block and phosphorylation of bcl-2 (48 h), then phosphorylation of tau and externalization of phosphatidylserine at the early phase of apoptosis (72 h) and finally DNA fragmentation (96 h). Similar results were obtained with 0.5 microM vinorelbine. Paclitaxel induced a lower increase in tau phosphorylation in differentiated SK-N-SH/RA+ cells which are less sensitive to apoptosis. Moreover, doxorubicin whose mechanism of action is independent of microtubules also induced immunostaining of tau at 72 h treatment. In conclusion, our results on neuroblastoma cells show that overexpression of hyperphosphorylated tau is involved in the apoptotic process induced by anti-microtubule agents and may be extended to others cytostatic drugs. Thus, tau protein may play a role in the cellular events observed in neuroblastoma cells undergoing apoptosis.

Journal Article↗

PubMed1999

Differentiation of human colon cancer cells changes the expression of beta-tubulin isotypes and MAPs.

The human colon adenocarcinoma HT29-D4 cell line is an interesting model for studies on epithelial cell differentiation. Undifferentiated cells are malignant proliferating cells, whereas differentiated cells act like epithelial polarized cells. In the present study, we first characterized the action of taxoids on the microtubular network of HT29-D4 cells according to the state of differentiation. Microtubular bundles were found in undifferentiated cells but not in differentiated cells, even with 500-fold higher taxoid concentrations for 96 h. This finding led us to study changes in microtubules according to the polarity status of the cell. E-MAP-115 was expressed only in differentiated cells; expression of beta-tubulin isotypes was altered in them relative to undifferentiated cells. Classes I, II, III, IVa and IVb isotypes were expressed in both phenotypes; however, differentiated epithelial cells displayed a specific increase in class III beta-tubulin. Thus, the increase in expression of this beta-tubulin isotype in differentiated cells is not restricted to neuronal cells. Moreover, these expression changes may reflect a higher stability of microtubular network in differentiated cells, which may explain the lower activity of anti-microtubule agents, independently of the mitotic process. These results indicate that the composition of microtubules should be considered as one of the criteria involved in the response of tumour cells to chemotherapy with anti-microtubule agents.

Antineoplastic Agents, Phytogenic↗

PubMed1998

Effect of microtubule disruption on cell adhesion and spreading.

Microtubules have been involved in a variety of cellular processes. In this study, we examined the role of the microtubular system in the adhesion and spreading of the adenocarcinoma cell line HT29-D4. Disruption of microtubules by nocodazole or navelbine resulted in an increase in cell adhesion to purified ECM proteins. This enhanced cell adhesion is mediated by integrins, but is not attributable to quantitative changes in the number of integrin receptors at the cell surface, as determined by flow cytometric analysis. In contrast to attachment, spreading of HT29-D4 cells was reduced by nocodazole treatment in a dose-dependent manner. Thus, microtubule depolymerization appears to increase initial attachment of cells to extracellular matrix, while impeding subsequent cell spreading.

Adenocarcinoma↗

PubMed1998

The effect of combining antitubulin agents on differentiated and undifferentiated human colon cancer cells.

The cytotoxicity of sequential combinations of a taxoid [paclitaxel (TAX) or docetaxel (TXT)] with a vinca alkaloid [vinorelbine (NVB)] was compared in differentiated and undifferentiated HT29-D4 cells. Agents were titrated from low doses inducing no modification of microtubule network to high doses corresponding to the clinically relevant concentrations that block mitosis. For undifferentiated cells, the sequential combination NVB/TAX was more efficient than TAX/NVB (22% cell survival versus 37% for 5 nM TAX and NVB). Surprisingly, we successively obtained synergism for low doses of both compounds [NVB (1-5 nM) and TAX (1-15 nM)], then additivity and finally antagonism when one of the compounds was at the concentration inducing mitotic block. The three patterns of results were also obtained with NVB/TXT combinations. For the synergistic combinations at the lowest concentrations, cytotoxicity occurred by apoptosis following mitosis. For differentiated cells, the most cytotoxic combinations were 1 microM TAX or TXT for 3 days followed by 1 microM NVB for 3 days, and 0.75 nM TAX or TXT for 9 days followed by 1 microM NVB for 3 days, the latter producing synergistic effects. Cytotoxicity occurred by apoptosis for the two states of differentiation. Major differences depending on cell phenotype were demonstrated: low sensitivity of differentiated cells to antitubulin agents and the difference in apoptotic pathways since mitosis is not involved in differentiated cells.

Antineoplastic Agents, Phytogenic↗

PubMed1997

Pretreatment by tubulin agents decreases C-MYC induction in human colon carcinoma cell line HT29-D4.

For HT29-D4 cell line, we confirmed the interaction between c-Myc protein and microtubules by immunoprecipitation. We then studied the effect of antimitotic agents, nocodazole and the taxoids [paclitaxel (taxol) and docetaxel (taxotere)] on c-myc oncogene expression. The expression was analyzed by RT-PCR and Western blot. Taxol (1 microM), taxotere (1 microM) and nocodazole (3 microM) inhibited by 30-50% the c-myc induction produced by growth factors in culture medium. According to the flow cytometry analysis, the inhibition is not linked to the mitotic block. These results observed for both stabilizing and depolymerizing agents suggest that microtubular system is involved in c-myc expression more through its dynamic properties which influence signal transduction and intracellular transports than through its direct interaction with c-Myc protein.

Antineoplastic Agents, Phytogenic↗

PubMed1997

[Clinical pilot study on repeated use of heparin, vancomycin, colimycine locked flush solution for central intravenous implanted catheter in oncology].

With an anti-infectious and an antithrombotic prophylaxis aims, a locked flush solution including heparin and vancomycin, was used systematically for implantable venous access system for each patient, from january to april 1995. Since the 6th of april 1995, in order to widen the antibiotic spectrum on Gram negative bacteriae, we added colimycin at the flush solution. In 1995, 342 hospitalised patients held this type of venous access and received chemotherapy and/or radiochemotherapy for cancer. Two thousand six hundred thirty three manipulations were done, 575 with the first flush solution, 2058 with the second. During the year, 15 implantable access system (4.4%) were considered as infected, only 3 (0.9%) were removed, in the first period. THe infectious rate seemed to be stable, but the bacterial assessment to be modified between the two periods. The Gram negative bacterial infections seemed to decrease with colimycin addition (33% versus 50%). These results must be confirmed by a long term and/or randomized study.

Anti-Bacterial Agents↗