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V Favaudon

Publications and source records attributed to V Favaudon.

At least 19 recordsLinked to original sources
PubMed2004

Additive interaction of gefitinib ('Iressa', ZD1839) and ionising radiation in human tumour cells in vitro.

Cultures of human carcinoma A-431, A-549 and HeLa cells were challenged with gamma-rays without or with concomitant exposure to gefitinib, a potent inhibitor of the tyrosine kinase activity of epidermal growth factor receptor (EGFR). The outcome of treatment was determined from cell and colony count, cell cycle progression and DNA double-strand break formation and rejoining. Apoptosis was measured in parallel from hypodiploid DNA and using an annexin V assay. Gefitinib developed a cytostatic effect in all cell lines, with drug sensitivity correlating the level of EGFR expression. A weak cytotoxicity of gefitinib was observed in HeLa cells only, although the drug was unable to induce significant cell cycle redistribution in this cell line. In contrast, substantial G1 block and S-phase depletion was observed in A-431 and A-549 cells exposed to gefitinib. The drug brought about additive to subadditive interaction with radiation with regard to growth inhibition, clonogenic death and induction of apoptosis. Consistently, gefitinib did not hinder the rejoining of radiation-induced DNA double-strand breaks in any cell line. The results demonstrate that gefitinib may elicit cytotoxicity at high concentration, but does not act as a radiosensitiser in vitro in concomitant association with radiation.

Antineoplastic Agents↗
PubMed2004

[Targeted drugs in radiation therapy].

New drugs aiming at the development of targeted therapies have been assayed in combination with ionizing radiation over the past few years. The rationale of this concept comes from the fact that the cytotoxic potential of targeted drugs is limited, thus requiring concomitant association with a cytotoxic agent for the eradication of tumor cells. Conversely a low level of cumulative toxicity is expected from targeted drugs. Most targeted drugs act through inhibition of post-translational modifications of proteins, such as dimerization of growth factor receptors, prenylation reactions, or phosphorylation of tyrosine or serine-threonine residues. Many systems involving the proteasome, neoangiogenesis promoters, TGF-beta, cyclooxygenase or the transcription factor NF-kappaB, are currently under investigation in hopes they will allow a control of cell proliferation, apoptosis, cell cycle progression, tumor angiogenesis and inflammation. A few drugs have demonstrated an antitumor potential in particular phenotypes. In most instances, however, radiation-drug interactions proved to be strictly additive in terms of cell growth inhibition or induced cell death. Strong potentiation of the response to radiotherapy is expected to require interaction with DNA repair mechanisms.

Animals↗
PubMed2002

Biological basis for chemo-radiotherapy interactions.

For over 10 years, chemo-radiotherapeutic combinations have been used to treat locally advanced epithelial tumours. The rationale for these combinations relies on spatial cooperation or interaction between modalities. Interactions may take place (i) at the molecular level, with altered DNA repair or modification of the lesions induced by drugs or radiation, (ii) at the cellular level, notably through cytokinetic cooperation arising from differential sensitivity of the various compartments of the cell cycle to the drug or radiation, and (iii) at the tissue level, including reoxygenation, increased drug uptake or inhibition of repopulation or angiogenesis. Some mechanisms underlying interaction of radiation with cis-diammino-platinum (II) (cis-Pt), 5-fluoro-2'-deoxyuridine (5-FU), taxanes and gemcitabine are described. It is shown how various mechanisms including cell synchronisation and reoxygenation concur to paclitaxel-induced radiosensitisation. In the future, specific targeting of tumours, for example, with the epidermal growth factor receptor (EGFR) or angiogenesis inhibitors, should be achieved in order to increase the therapeutic index.

Antineoplastic Agents↗
PubMed2000

Radiation-induced arrest of cells in G2 phase elicits hypersensitivity to DNA double-strand break inducers and an altered pattern of DNA cleavage upon re-irradiation.

PURPOSE: To determine how radiation-induced arrest in G2 affects the response of mammalian cells to a challenging dose of radiation or to antitumour drugs producing DNA double-strand breaks. MATERIALS AND METHODS: V79 fibroblast survival to 5 Gy gamma-rays followed at intervals by 3 Gy irradiation or by contact with an equitoxic dose of neocarzinostatin or etoposide, was measured by clonogenic assays. The pattern of radiation-induced DNA double-strand breaks was determined by filter elution and CFGE (continuous field gel electrophoresis) or PFGE (pulsed-field gel electrophoresis) in G2-arrested cells as well as in nonpre-irradiated asynchronous or synchronized cells. The cell-cycle phase specificity of drug susceptibility was determined in synchronized HeLa cells. RESULTS: Cell kill by radiation-drug combined treatment varied markedly with the time elapsed after priming irradiation. Pre-irradiated, G2-arrested V79 fibroblasts demonstrated excess double-stranded DNA cleavage upon re-irradiation and hypersensitivity to drugs and radiation, although maximum resistance to both neocarzinostatin and etoposide in synchronized HeLa cells was in G2. This effect occurred in the megabase range only, with a peak around 4 Mbp; no change in the electrophoretic migration profile of DNA was observed below 1 Mbp. Moreover, the DNA migration profile and the yield of DNA cleavage in G2-arrested cells were close to those expected from S-phase cells. CONCLUSION: The available data suggest that mechanisms operating within the radiation-induced G2 block promote susceptibility to DNA double-strand break inducers at this stage. It is also proposed that the conformation of DNA in cells accumulated in G2 following irradiation bears resemblance to that for cells in S phase, due either to active repair mechanisms or to inhibition of chromosome disentanglement at the S-G2 transition.

Animals↗
PubMed2000

Hyperfast, early cell response to ionizing radiation.

PURPOSE: To determine whether the oscillatory changes of radio-sensitivity which occur within fractions of a second to a few minutes following flash irradiation correlate with an altered incidence of apoptosis, DNA strand breaks or lipid-coupled signalling. MATERIALS AND METHODS: Human tumor cells (SQ-20B, LoVo) or Chinese hamster V79 fibroblasts were exposed to split-dose, pulse irradiation with 3.5 MeV electrons at high dose-rate (12 or 120 Gy x s(-1)) and the effects assessed by clonogenic assays, analysis of DNA cleavage and microscopic observation. RESULTS: The processes underlying oscillatory radiation response were saturable, but did not correlate with an increased incidence of DNA single- or double-strand breaks or apoptosis. N-acetylcysteine and inhibitors of lipid-derived signalling also failed to alter oscillatory response. However, this response did correlate with phenotypic alterations evoking mitotic or delayed cell death. Furthermore, high dose-rate irradiation provided a lower level of instability than protracted gamma-ray irradiation. CONCLUSIONS: It is proposed that the early steps of DNA damage recognition and repair following priming radiation exposure bring about rapid, synchronous remodeling of chromatin, evoking enhanced chromosome damage upon re-irradiation.

Animals↗
PubMed2000

Poly(ADP-ribose) polymerase, a major determinant of early cell response to ionizing radiation.

PURPOSE: To determine whether DNA-dependent protein kinase (DNA-PK) and poly(ADP-ribose) polymerase (PARP-1) are involved in eliciting the rapid fluctuations of radiosensitivity that have been observed when cells are exposed to short pulses of ionizing radiation. MATERIALS AND METHODS: The effect of DNA-PK and PARP-1 inhibitors on the survival of cells to split-dose irradiation was investigated using Chinese hamster V79 fibroblasts and human carcinoma SQ-20B cells. The responses of PARP-1 proficient and PARP-1 knockout mouse 3T3 fibroblasts were compared in a similar split-dose assay. RESULTS: Inactivation of DNA-PK by wortmannin potentiated radiation-induced cell kill but it did not alter the oscillatory, W-shaped pattern of early radiation response. In contrast, oscillatory radiation response was abolished by 3-aminobenzamide, a reversible inhibitor of enzymes containing a PARP catalytic domain. The oscillatory response was also lacking in PARP-1 knockout mouse 3T3 fibroblasts. CONCLUSION: The results show that PARP-1 plays a key role in the earliest steps of cell response to ionizing radiation with clonogenic ability or growth as endpoint. It is hypothesized that rapid poly(ADP-ribosylation) of target proteins, or recruitment of repair proteins by activated PARP-1 at the sites of DNA damage, bring about rapid chromatin remodelling that may affect the incidence of chromosomal damage upon re-irradiation.

3T3 Cells↗
PubMed1999

Synthesis and in vitro evaluation of novel 2,6,9-trisubstituted purines acting as cyclin-dependent kinase inhibitors.

Novel C-2, C-6, N-9 trisubstituted purines derived from the olomoucine/roscovitine lead structure were synthesized and evaluated for their ability to inhibit starfish oocyte CDK1/cyclin B, neuronal CDK5/p35 and erk1 kinases in purified extracts. Structure activity relationship studies showed that increased steric bulk at N-9 reduces the inhibitory potential whereas substitution of the aminoethanol C-2 side chain by various groups of different size (methyl, propyl, butyl, phenyl, benzyl) only slightly decreases the activity when compared to (R)-roscovitine. Optimal inhibitory activity against CDK5, CDK1 and CDK2, with IC50 values of 0.16, 0.45 and 0.65 microM, respectively, was obtained with compound 21 containing a (2R)-pyrrolidin-2-yl-methanol substituent at the C-2 and a 3-iodobenzylamino group at the C-6 of the purine. Compound 21 proved cytotoxic against human tumor HeLa cells (LD50-6.7 microM versus 42.7 microM for olomoucine, 24-h contact). Furthermore, unlike olomoucine, compound 21 was effective upon short exposure (LD50= 25.3 microM, 2-h contact). The available data suggest that the affinity for CDKs and the cytotoxic potential of the drugs are inter-related. However, no straightforward cell cycle phase specificity of the cytotoxic response to 21 was observed in synchronized HeLa cells. With the noticeable exception of pronounced lengthening of the S-phase transit by 21 applied during early-S in synchronized HeLa cells, and in striking contrast with earlier reports on studies using plant or echinoderm cells. olomoucilnc and compound 21 were unable to reversibly arrest cell cycle progression in asynchronous growing HeLa cells. Some irreversible hlock in GI and G2 phase occurred at high olomoucine concentration, correlated with induced cell death. Moreover, chmronic exposure to lethal doses of compound 21 resulted in massive nuclear fragmentation, evocative of mitotic catastrophe with minour amounts of apoptosis only. It was also found that olomoucine and compound 21 reversibly block the intracellular uptake of nuicleosides with high efficiency.

CDC2 Protein Kinase↗
PubMed1997

One-electron photo-oxidation of reduced Desulfovibrio vulgaris flavodoxin on laser excitation at 355 nm.

Electron ejection from the reduced flavin in flavodoxin from Desulfovibrio vulgaris was obtained on exposure of the protein to the third harmonic radiation (354.7 nm) generated from a pulsed Nd/YAG laser. The results indicate that the reaction is due to stepwise two-photon excitation of the reduced flavin via the excited singlet state. The absorption spectrum of the neutral flavosemiquinone radical formed in this process was obtained. This spectrum remains stable over the time of study (0.2 ms) in the pH range studied, except for a slight evolution during the first microseconds, attributed to conformational readjustments of the active site. This two-photon excitation method provides a convenient means of generating the flavosemiquinone for ultrafast kinetic studies.

Binding Sites↗
PubMed1997

[Early cell response to radiation].

The early steps of cellular radiation response have been investigated using a linear electron accelerator operated in a split-dose mode, in such a way that the time intervals between pulse exposures to relativistic electrons ranged from fractions of a second to a few minutes. The initial dose brought about large, synchronous changes in radiation sensitivity and generated a tetraphasic, W-shaped time-dependent profile of cell survival upon the second radiation exposure. While this time-related process was observed in most cell lines investigated, its kinetic parameters varied significantly from one cell line to the other. The number of DNA strand breaks (neutral and alkaline DNA filter elution) and the level of apoptosis (gel electrophoresis and flow cytometry) induced at the different phases of the time-dependent profile showed no relationship with the W-effect. It is presently hypothesized that mechanisms involved in molecular recognition of radio-induced lesions and initiation of genomic instability play a major role in this effect. Whatever the mechanism involved, the split-dose irradiation in the range of seconds enables dissecting the early steps of radiation response. The relevance of the W-effect to radiation therapy and technical drawbacks are discussed.

Cell Cycle↗
PubMed1997

Pulse treatment of interphasic HeLa cells with nanomolar doses of docetaxel affects centrosome organization and leads to catastrophic exit of mitosis.

In order to investigate the role of centrosome duplication in mitotic spindle morphogenesis, we designed a 1 hour pulse treatment protocol on synchronized HeLa cells with nanomolar doses of taxoids that might impair centrosome biogenesis but would allow the recovery of normal microtubule (Mt) dynamics before mitosis. We were prompted to use this approach as docetaxel (DOC; taxotereTM), a taxoid known to promote Mt polymerization, was shown to be more cytotoxic when applied during S phase. We show that pulse drug exposure is most efficient in late S and in G2 and results in a marked disorganization of the centrosome in G2, the pericentriolar material (PCM) being dissociated from centrioles. Separation of centrosomes at the G2-M transition is also impaired and mitotic spindle morphogenesis is grossly abnormal: although in most spindles chromosomes align in a metaphase plate, the two centrosomes stay most often unseparated at one pole and most of the NuMA protein accumulates at the other. Interestingly, we find that the centrosomes' ability to duplicate is not abolished as they are still able to trigger parthenogenetic development of frog eggs. Despite spindle asymmetry, the progression through mitosis is not blocked. This results in a catastrophic exit from mitosis, each mitotic cell generating several micronucleated cells linked together by multiple midbodies. Lack of mitotic block appears therefore as the prime cause of cell lethality. These experiments suggest that NuMA redistribution at the onset of mitosis depends upon the correct redistribution of PCM between centriole pairs. They also indicate that the presence of aberrant spindle poles does not alert the surveillance mechanism controlling the exit of mitosis.

Animals↗
PubMed1996

Interaction of ionizing radiation with paclitaxel (Taxol) and docetaxel (Taxotere) in HeLa and SQ20B cells.

Altered gamma-ray response by brief (1 h), concomitant exposure to paclitaxel (Taxol) or docetaxel (Taxotere) was investigated in growing HeLa and SQ20B human tumor cells in vitro. For both cell lines, both taxoids were able to reduce or enhance radiation cell killing, depending on the drug concentration. Large reduction of radiosensitivity (up to 3.3-fold reduction relative to radiation alone) was observed in HeLa cells over a wide range of drug concentrations, extending to 1.5- (paclitaxel) or 3.3- fold (docetaxel) the IC50s determined for drug alone. This antagonistic effect was also observed with SQ20B cells. It disappeared for drug concentrations exceeding 0.9 (SQ20B), 1.6 (HeLa; paclitaxel), and 3.4 (HeLa; docetaxel) IC50 equivalents, above which a drug dose-dependent, supra-additive radiation-drug interaction was observed. Reduction of radiation susceptibility in the low-drug dose range also held for mid-G1 synchronized HeLa cells, i.e., in the cell cycle compartment characterized as the most resistant one to docetaxel (C. Hennequin et al., Br. J. Cancer, 71: 1194-1198, 1995). In the case of SQ20B cells, the cytotoxicity of either drug or radiation alone was primarily dependent on the state of growth, with quiescent (G(0)) cells showing increased radiosensitivity and reduced drug toxicity compared to the growing fraction. The effect of taxoids (1-h contact) was finally investigated in sequential treatment as a function of the time elapsed between radiation and exposure to drugs. In HeLa cells, the postirradiation time-dependence of the response to combined treatment was biphasic. The radioprotecting potential of either taxoid disappeared in approximately 1.5 h following radiation. At longer postirradiation delays, radiation-induced redistribution in the cell cycle appeared to be the major determinant of HeLa cell survival, in relation to the differential cell cycle phase specificity of each drug. Pronounced paclitaxel recovery versus increased sensitivity to docetaxel occurred over 8 h after irradiation. SQ20B cells showed monophasic radiation recovery with both drugs over the same time range.

Antineoplastic Agents, Phytogenic↗
PubMed1996

Pulse exposure to ionizing radiation elicits rapid changes in cellular radiosensitivity.

A linear electron accelerator, operated in a recurrent chopped mode, was used for time-resolved investigation of split-dose radiation recovery in 3 mammalian cell lines in vitro. The time intervals separating the sequential radiation exposures in this study ranged from fractions of a second to a few minutes. The primary pulse brought about rapid, synchronous oscillations of cellular radiosensitivity giving rise to a tetraphasic, W-shaped time-dependent profile whose first phase was accomplished by a large decrease of cell survival. Only the last phase correlated with sub-lethal damage repair determined by gamma-ray irradiation. The same profile was observed for the 3 cell lines investigated. However, the kinetics of the whole process varied extensively from one cell line to another. The first phase lasted 1 s only for Chinese hamster V79 fibroblasts, 6 s for human squamous carcinoma SQ20B cells, and as much as 25 s for human colon adenocarcinoma LoVo cells. The relative amplitude of this first phase grew with both the first and second radiation doses in the range explored. It is hypothesized that rapid oscillation of the cytotoxic potential of radiation may result from various mechanisms such as molecular recognition of radio-induced lesions, changes in chromatin structure, or differential activation of phospholipid-dependent transduction pathways.

Adenocarcinoma↗
PubMed1995

Internal motions of apo-neocarzinostatin as studied by 13C NMR methine relaxation at natural abundance.

Dynamics of the backbone and some side chains of apo-neocarzinostatin, a 10.7 kDa carrier protein, have been studied from 13C relaxation rates R1, R2 and steady-state 13C-(1H) NOEs, measured at natural abundance. Relaxation data were obtained for 79 nonoverlapping C alpha resonances and for 11 threonine C beta single resonances. Except for three C alpha relaxation rates, all data were analysed from a simple two-parameter spectral density function using the model-free approach of Lipari and Szabo. The corresponding C-H fragments exhibit fast (tau e < 40 ps) restricted libration motions (S2 = 0.73 to 0.95). Global examination of the microdynamical parameters S2 and tau e along the amino acid sequence gives no immediate correlation with structural elements. However, different trends for the three loops involved in the binding site are revealed. The beta-ribbon comprising residues 37 to 47 is spatially restricted, with relatively large tau e values in its hairpin region. The other beta-ribbon (residues 72 to 87) and the large disordered loop ranging between residues 97-107 experience small-amplitude motions on a much faster (picosecond) time scale. The two N-terminal residues, Ala1 and Ala2, and the C-terminal residue Asn113, exhibit an additional slow motion on a subnanosecond time scale (400-500 ps). Similarly, the relaxation data for eight threonine side-chain C beta must be interpreted in terms of a three-parameter spectral density function. They exhibit slower motions, on the nanosecond time scale (500-3000 ps). Three threonine (Thr65, Thr68, Thr81) side chains do not display a slow component, but an exchange contribution to the observed transverse relaxation rate R2 could no be excluded at these sites. The microdynamical parameter (S2, tau e and R2ex) or (S(slow)2, S(fast)2 and tauslow) were obtained from a straightforward solution of the equations describing the relaxation data. They were calculated assuming an overall isotropic rotational correlation time tau c for the protein of 5.7 ns, determined using standard procedures from R2/R1 ratios. However, it is shown that the product (1-S2) x tau e is nearly independent of tau c for residues not exhibiting slow motions on the nanosecond time scale. In addition, this parameter very closely follows the heteronuclear NOEs, which therefore could be good indices for local fast motions on the picosecond time scale.

Apoproteins↗
PubMed1995

S-phase specificity of cell killing by docetaxel (Taxotere) in synchronised HeLa cells.

Cell viability following short (1 h) contact with paclitaxel or docetaxel was assayed using synchronised HeLa cells. Docetaxel proved almost totally lethal against S-phase cells. Its toxicity was only partial against cells in mitosis, and declined to a minimum with progression to G1. For paclitaxel, cytotoxicity increased with progression through S and G2, peaked at the time of mitosis, and decreased thereafter. Maximum resistance to paclitaxel was in early S. Although lethal, brief exposure to docetaxel in S-phase did not delay progression through S and G2. Gross damage was detectable immediately after mitosis, with dysfunction in cytokinesis and accumulation of multinucleated, non-viable cells. Arrest of cells at prometaphase required continuous contact with lethal amounts of docetaxel or reintroduction of drug shortly before mitosis following pulse-chase treatment in mid-S-phase. Paclitaxel at moderate doses presumably acts mostly via damage to the mitotic spindle. In contrast, the available data suggest that docetaxel primarily targets centrosome organisation, leading to abortive mitosis and cell death.

Antineoplastic Agents, Phytogenic↗
PubMed1994

[The effect of radiation on malignant cells].

Mechanisms of death following irradiation of malignant cells are incompletely understood. Radiation-induced lesions and their consequences on the cancer cell are described. Factors conditioning malignant cell response to radiation are discussed, as well as the mechanisms of radiation-induced carcinogenesis. Finally, the recent molecular biology contributions to gene regulation during cell growth are presented.

Cell Cycle↗
PubMed1994

Interaction of ionizing radiation with the topoisomerase I poison camptothecin in growing V-79 and HeLa cells.

Interaction between gamma-rays and camptothecin (CPT) was investigated in vitro, using log phase HeLa-S3 cells and Chinese hamster V-79 fibroblasts. A plateau of toxicity was rapidly reached for both cell lines upon exposure to CPT alone, consistent with S-phase specificity of CPT. With synchronized HeLa cells, however, CPT proved cytotoxic after the middle of G1 phase. This effect was abolished by cotreatment with the DNA polymerase alpha inhibitor aphidicolin. CPT enhanced the initial slope of the radiation survival curves for asynchronous cells by a factor of 1.1 (HeLa) to 2.3 (V-79). This apparent radiation sensitization correlated with the intrinsic radiosensitivities of the drug-surviving fractions within the different compartments of the cell cycle. There was no evidence of mutual potentiation of CPT and radiation in terms of survival as well as with regard to the formation and rejoining of DNA double-strand breaks. V-79 cells exhibited pronounced postirradiation recovery. In contrast, the response of HeLa cells to drug did not vary appreciably for over 8-h following radiation. This difference proceeded from differential cell cycle redistribution. In both cell lines, acute irradiation produced depletion of the G1 compartment, accumulation at the S-G2 junction, and G2 arrest in proportion to the gamma-ray dose. However, while radiation brought about rapid depletion of the S-phase compartment in V-79 cells, it induced accumulation of HeLa cells into S phase. As a result, the CPT-sensitive HeLa cell population, consisting of the early-S, mid-S, and late G1 fractions, did not vary very much after irradiation. Exposure to CPT under conditions of low dose rate irradiation (1 Gy/h) selectively reversed the radiation effect on S-phase progression in V-79 cells; i.e., it induced accumulation of cells in S phase in the same way as found with HeLa cells. Isobolic analysis of survival data consistently showed supraadditivity of cell killing in both cell lines upon concomitant exposure to CPT and low dose rate irradiation. Cytokinetic cooperation appears to be the major determinant of cell survival in treatments associating CPT and radiation in growing cells. Attempts to predict the outcome of such a combined modality thus should take into consideration the response of the growing fraction of each cell line in terms of cell cycle-regulatory processes and redistribution.

Animals↗
PubMed1994

[Radio-chemotherapy combinations: from biology to clinics].

Combination of radiotherapy and chemotherapy (CRC) is actually one important way of research in oncology. Theoretical advantages are: 1) Spatial cooperation; 2) Additivity, which is only obtained if the toxicity of each modality are different; 3) Supra-additivity, which needs a rigorous in vitro definition; the only way to prove it is to make an isobologram analysis. This model has however, some limitations: qualitative variable could not be used, results could be different, depending on the cell line and isoeffect chosen... In fact, a supra-additivity was only demonstrated for cisplatinum and etoposide. Interactions mechanisms were: 1) at the molecular level, creation of new lesions or inhibition of radiation lesions repair; 2) At the cellular level, either cytokinetic cooperation with S-phase dependent drugs, or synchronisation for the drugs which blocked the cells in M-phase; 3) At the tissular level, reoxygenation, cycle redistribution... In clinical practice, three mains schedules have been described: sequential, alternating and concomitant. Only the latter try to use the supra-additivity phenomena. Aims of CRC could be: improvement or in survival or in local control, preservation of an functional organ... Depending on the tumor site and aim of the CRC, some schedules had to be preferred. For head and neck cancers, alternating or concomitant schedules offer a better local control. In bronchial carcinomas, sequential administration of the two modalities reduce the metastatic rate, but not the local control. Concomitant schedule improve the local control rate only. In some conservative protocol of bladder cancers, sequential and concomitant administration were used. In conclusion, CRC begins to be the usual clinical practice. The present schedules could be improved with the help of laboratory findings, which are now more and more precise.

Antineoplastic Agents↗