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Biomedical subjects

C Bailly

Publications and source records attributed to C Bailly.

At least 91 records · Page 5Linked to original sources
PubMed2000

[Kidney cancers with supra-diaphragmatic invasion. Surgical treatment using extracorporal circulation with heart arrest].

STUDY AIM: The study aim was to report results of nephrectomy with resection of cavo atrial thrombus in 6 patients with a renal carcinoma and supra-diaphragmatic vena cava extension and to discuss limits of the surgical indications. PATIENTS AND METHOD: Six patients, five adults (mean age: 57 +/- 10 years) and a four-year old girl, were operated on for a renal cell carcinoma with supra-diaphragmatic vena cava extension. The venous extension was detected in all cases by abdominal ultrasonography. The superior extent of the thrombus was effectively visualized by CT scan in three cases, and by ultrasonography and magnetic resonance imaging in all cases. All the patients were operated on, using cardio-pulmonary bypass, without circulatory arrest, four in normothermia, two in moderate hypothermia at 28 degrees C. RESULTS: Hospital mortality was 0%. Average intensive care unit stay was 3.8 days. During the following period, all the patients developed metastatic disease. Mean survival rate of the five adult patients who had loco-regional invasion was 9.4 months (range: 6 to 19). The young girl underwent a wedge excision of two pulmonary metastases one year later and was still alive 7 years later. CONCLUSIONS: With cardio-pulmonary bypass, surgical resection of cavo-atrial thrombi may be performed with a low mortality and morbidity rate but late results were disappointing. Surgery should be limited to patients without loco-regional invasion or distant metastatic disease, and therefore accurate preoperative staging is mandatory.

Adult↗
PubMed2000

Abnormal expression of the ATM and TP53 genes in sporadic breast carcinomas.

The ataxia telangiectasia gene (ATM) has been implicated as a risk factor in the development of sporadic breast carcinomas. ATM protein expression was analyzed by immunohistochemistry in 17 breast carcinomas with two monoclonal antibodies whose immunohistochemical use was first validated by comparing the immunoreactivity observed in spleen samples from ataxia telangiectasia and trauma patients. In normal breast ducts, ATM showed nuclear expression in the epithelial but not in the myoepithelial cells. In contrast, this nuclear expression was absent or low in the epithelial cancer cells in 10 of 17 (59%) of the tumors studied. Allelic imbalance in the ATM gene was found in three of seven tumors examined. Two of these showed reduced ATM protein expression, but this did not correlate with the presence of ATM mutations in the tumor DNA detected by restriction endonuclease fingerprinting screening. These results suggest that the reduced ATM protein expression could be attributable, in certain tumors, to deletions or rearrangements within or close to the ATM gene. Positive p53 immunostaining was found in 10 tumors, with TP53 mutations detected in 8. Three tumors had both low ATM expression and mutated TP53. Our results indicate that in the majority (15 of 17) of the sporadic breast carcinomas examined, not only is the functionality of the ATM-p53-mediated DNA damage response compromised, but also other signaling pathways activated by these two multifunctional proteins are likely to be impaired, which could be a contributing factor to tumor development and progression.

Allelic Imbalance↗
PubMed2000

DNA intercalation, topoisomerase II inhibition and cytotoxic activity of the plant alkaloid neocryptolepine.

Cryptolepine and neocryptolepine are two indoloquinoline alkaloids isolated from the roots of the African plant Cryptolepis sanguinolenta. Both drugs have revealed antibacterial and antiparasitic activities and are strongly cytotoxic to tumour cells. We have recently shown that cryptolepine can intercalate into DNA and stimulates DNA cleavage by human topoisomerase II. In this study, we have investigated the mechanism of action and cytotoxicity of neocryptolepine, which differs from the parent isomer only by the orientation of the indole unit with respect to the quinoline moiety. The biochemical and physicochemical results presented here indicate that neocryptolepine also intercalates into DNA, preferentially at GC-rich sequences, but exhibits a reduced affinity for DNA compared with cryptolepine. The two alkaloids interfere with the catalytic activity of human topoisomerase II but the poisoning activity is slightly more pronounced with cryptolepine than with its isomer. The data provide a molecular basis to account for the reduced cytotoxicity of neocryptolepine compared with the parent drug.

Alkaloids↗
PubMed2000

Design of two etoposide-amsacrine conjugates: topoisomerase II and tubuline polymerization inhibition and relation to cytotoxicity.

Topoisomerase II represents the main target for the antitumour drugs etoposide and amsacrine, which are both used clinically. Previous studies have shown that the glycoside moiety of etoposide is not necessary for cytotoxicity or DNA topoisomerase II inhibition. For this reason, we designed two epipodophyllotoxin derivatives for which the dispensable sugar moiety of etoposide has been replaced by a m-methoxy-methane-sulfonamide-anilino group analogous to the topoisomerase II-targeted domain of amsacrine. We report the synthesis of the hybrid molecules that have the epipodophyllotoxin and anilino groups directly linked (ICP-114) or connected by an ethylene spacer (ICP-147). Plasmid DNA relaxation and kinetoplast DNA decatenation assays were used to evaluate the effects of the drug on the catalytic activity of human topoisomerase II. We found that the hybrid ICP-147 was significantly more potent than both etoposide and amsacrine at stimulating DNA cleavage by the enzyme, whereas the hybrid ICP-114 lacking the linker chain was less potent. ICP-147 produces approximately 3 times more double-stranded breaks than ICP-114, suggesting that an ethylene spacer between the epipodophyllotoxin and amsacrine moieties is highly effective at inhibiting topoisomerase II. Sequencing data also supported the idea that the two moieties of ICP-147 participate to the interaction with topoisomerase II-DNA covalent complexes. Both hybrid compounds are more cytotoxic than etoposide but much less toxic than amsacrine toward L1210 leukemia cells. In addition to its effect on topoisomerase II, ICP-114 can inhibit tubulin polymerization, whereas ICP-147 is almost totally inactive in this assay. The unexpected capacity of ICP-114 to interfere with the polymerization of tubulin suggests that this compound can target tubulin dimers, as it is the case with certain antitumor sulfonamides. The design of etoposide-amsacrine hybrids may thus represent an opportunity for the discovery of dual inhibitors that target both topoisomerase II and tubulin.

Amsacrine↗
PubMed1999

The influence of the exocyclic pyrimidine 5-methyl group on DNAse I cleavage and sequence recognition by drugs.

Incorporation of modified nucleotides into DNA, using the PCR, has allowed us to probe the influence that the exocyclic 5-methyl group of pyrimidines has on DNAse I cleavage and sequence recognition by drugs. The results show that removal of the methyl group from the major groove, made possible by substituting uridine for thymidine, allows DNAse I to cleave more readily at AT-rich regions compared to normal DNA. By contrast, addition of an extra methyl group, contrived by substituting 5-methylcytidine for normal cytidine, allows DNAse I to cleave more readily at GC-rich regions compared to normal DNA. In the cutting pattern of DNA containing both uridine and 5-methyl cytosine, we find the cleavage characteristics of both the single-substituted DNA species combined. Thus, the presence or absence of the exocyclic 5-methyl group in the major groove has a strong influence on the relative intensity of cleavage of phosphodiester bonds by DNAse I. These nucleotide substitutions can also influence the sequence-selective binding of drugs to DNA. Whereas removal of the methyl group (replacement of T with U) generally has little effect on sequence recognition by a variety of drugs, addition of a methyl group (replacement of C with M) generates new binding sites for some intercalators, namely daunomycin, DACA and SN16713.

Autoradiography↗
PubMed1999

Homocamptothecin, an E-ring-modified camptothecin analogue, generates new topoisomerase I-mediated DNA breaks.

Homocamptothecin (hCPT) contains a seven-membered beta-hydroxylactone in place of the conventional six-membered alpha-hydroxylactone ring found in camptothecin and its tumor active analogues, including topotecan and irinotecan. The homologation of the lactone E-ring reinforces the stability of the lactone, thus reducing considerably its conversion into a carboxylate form which is inactive. We have recently shown that hCPT is much more active than the parent compound against a variety of tumor cells in vitro and in xenograft models, suggesting that a highly reactive lactone is not essential for topoisomerase I-mediated anticancer activity [Lesueur-Ginot et al. (1999) Cancer Res. 59, 2939-2943]. In the present study, we provide further evidence that hCPT has superior topoisomerase I inhibition capacities to CPT. In particular, we show that replacement of the camptothecin lactone E-ring with a homologous seven-membered lactone ring changes the sequence-specificity of the drug-induced DNA cleavage by topoisomerase I. Both CPT and hCPT stimulate the cleavage by topoisomerase I at T( downward arrow)G sites, but in addition, hCPT stabilizes cleavage at specific sites containing the sequence AAC( downward arrow)G. At low drug concentrations, the cleavage at the T( downward arrow)G sites and at the hCPT-specific C( downward arrow)G sites is more pronounced and more stable with hCPT than with CPT. The in vitro data were confirmed in cells. Higher levels of protein-DNA complexes were detected in P388 leukemia cells treated with hCPT than those treated with CPT. Immunoblotting experiments revealed that endogenous topoisomerase I was efficiently trapped onto DNA by hCPT in cells. Finally, the use of a leukemia cell line resistant to CPT provided evidence that topoisomerase I is involved in the cytotoxicity of hCPT. Altogether, the results show that the beta-hydroxylactone ring of hCPT plays an important and positive role in the poisoning of topoisomerase I. An explanation is proposed to account for such remarkable changes in the sequence specificity of topoisomerase I cleavage consequent to the modification of the lactone. The study sheds new light on the importance of the lactone ring of camptothecins for the stabilization of topoisomerase I-DNA complexes.

Animals↗
PubMed1999

DNA cleavage by hydroxy-salicylidene-ethylendiamine-iron complexes.

Bis(hydroxy)salen.Fe complexes were designed as self-activated chemical nucleases. The presence of a hy-droxyl group on the two salicylidene moieties serve to form a hydroquinone system cooperating with the iron redox system to facilitate spontaneous formation of free radicals. We compared the DNA binding and cleaving properties of the ortho -, meta- and para -(bishydroxy) salen.Fe complexes with that of the corresponding chelate lacking the hydroxyl groups. DNA melting temperature studies indicated that the para complex exhibits the highest affinity for DNA. In addition, this para compound was considerably more potent at cleaving supercoiled plasmid DNA than the regio-isomeric ortho - and meta -hydroxy-salen.Fe complexes, even in the absence of a reducing agent, such as dithiothreitol used to activate the metal complex. The DNA cleaving activity of the para isomer is both time and concentration dependent and the complexed iron atom is absolutely essential for the sequence uniform cleavage of DNA. From a mechanistic point of view, electron spin resonance measurements suggest that DNA contributes positively to the activation of the semi-quinone system and the production of ligand radical species responsible for subsequent strand scission in the absence of a reducing agent. The para -hydroxy-salen.Fe complex has been used for detecting sequence-specific drug-DNA interactions. Specific binding of Hoechst 33258 to AT sequences and chromomycin to GC sequences were shown. The para -bis(hydroxy)salen.Fe derivative complements the tool box of footprinting reagents which can be utilised to produce efficient cleavage of DNA.

Animals↗
PubMed1999

Stimulation of topoisomerase II-mediated DNA cleavage by an indazole analogue of lucanthone.

Lucanthone is an antitumour drug used as an adjuvant in radiation therapy. The drug intercalates into DNA and inhibits topoisomerase II. An indazole analogue of lucanthone (IA-5) was examined for its ability to modulate topoisomerase II-DNA cleavable complex formation in vitro. The drug contains a methylbenzothiopyranoindazole chromophore instead of the methyl-thioxanthenone nucleus of lucanthone. Using a radiolabelled linear plasmid DNA as a substrate, both lucanthone and the indazole analogue were shown to promote the cleavage of DNA by human topoisomerase II. Sequencing experiments with different restriction fragments indicated that the indazole drug promoted DNA cleavage primarily at sites having a C on the 3' side of the cleaved bond (-1 position). By contrast, in the same sequencing methodology lucanthone exerted a much weaker effect on topoisomerase II. The sequence selectivity of IA-5 is reminiscent of that of the anticancer drug mitoxantrone and its anthrapyrazole analogue losoxantrone, which is structurally close to IA-5. Binding to DNA and topoisomerase II inhibition are two distinct processes contributing separately to the cytotoxic activity of the indazole drug.

DNA↗
PubMed1999

Synthesis and antiviral activity of ethidium-arginine conjugates directed against the TAR RNA of HIV-1.

The regulatory protein Tat is essential for viral gene expression and replication of the human immunodeficiency virus type 1 (HIV-1). Tat transactivates the HIV-1 long terminal repeat (LTR) via its binding to the transactivation responsive element (TAR) and increases the viral transcription. Studies have shown that the binding of arginine and arginine derivatives induces a conformational change of the TAR RNA at the Tat-binding site. The unpaired A17 residue delimits a small cavity which constitutes a receptor site for small molecules, especially for ethidium bromide. These binding characteristics have prompted us to design a series of ethidium-arginine conjugates capable of interacting with the TAR RNA. Here we report the synthesis of six ethidium derivatives equipped with arginine side chains. These molecules were biologically evaluated, and two compounds (17 and 20) exhibited in vitro anti-HIV-1 activity at micromolar concentration, without toxicity (up to 100 microM concentration). Melting temperature studies indicated that the most active molecule (20) bound strongly to TAR in vitro. RNase protection experiments agreed with the molecular modeling studies which suggested that the ethidium moiety of 20 was inserted next to the A17 residue while the arginine side chain occupied the pyrimidine bulge.

Anti-HIV Agents↗
PubMed1999

[Intravascular leiomyomatosis of uterine origin. a case of pseudo-metastatic cavo-cardial thrombus].

BACKGROUND: Leiomyomatosis is a benign smooth muscle tumor which can provoke serious complications in case of intracaval or intracardiac extension. CASE REPORT: A 61-year-old woman had undergone hysterectomy at the age of 45 years for a hemorrhagic fibroma. She underwent surgery for infiltrative breast cancer 3 months before hospitalization and was taking tamoxifen 30 mg/day. In the cancer context, the diagnosis of cavo-cardiac metastatic thrombus was proposed but not confirmed at pathology. The diagnosis of uterine tissue intravascular leiomyomatosis was established on the basis of pathology findings and immunohistochemistry results. DISCUSSION: Five other cases of leiomyomatosis after hysterectomy have been reported in the literature.

Breast Neoplasms↗
PubMed1999

Demethylation of thymine residues affects DNA cleavage by endonucleases but not sequence recognition by drugs.

The 5-methyl group of thymidine residues protrudes into the major groove of double helical DNA. The structural influence of this exocyclic substituent has been examined using a PCR-made 160 bp fragment in which thymidine residues were replaced with uridine residues. We show that the dT-->dU substitution and the consequent deletion of the methyl group affects the cleavage of DNA by deoxyribonuclease I and micrococcal nuclease. Analysis of the DNase I cleavage sites, in terms of di and trinucleotides, indicates that homopolymeric tracts of d(AT) become significantly more susceptible to DNase I cleavage when uridine is substituted for thymidine residues. The results indicate that removal of the thymidine methyl groups from the major groove at AT tracts induces structural perturbations that transmit into the opposite minor groove, where they can be detected by endonuclease probing. In contrast, DNase I footprinting experiments with different mono and bis-intercalating drugs reveal that dT-->dU substitution does not markedly affect sequence-specific drug-DNA recognition in the minor or major groove of the double helix. The consequences of demethylation of thymidine residues are discussed in terms of changes in the minor groove width connected to variations in the flexibility of DNA and the intrinsic curvature associated with AT tracts. The study identifies the methyl group of thymine as an important molecular determinant controlling the width of the minor groove and/or the flexibility of the DNA.

Base Sequence↗
PubMed1999

Substitution at the F-ring N-imide of the indolocarbazole antitumor drug NB-506 increases the cytotoxicity, DNA binding, and topoisomerase I inhibition activities.

The antitumor drug NB-506, which is currently undergoing phase I/II clinical trials, contains a DNA-intercalating indolocarbazole chromophore substituted with a glucose residue. In addition to interacting with DNA, the drug stabilizes the topoisomerase I-DNA covalent complex. To reinforce the DNA binding and anti-topoisomerase I activities of NB-506, an analogue containing a new substituent on the naphthalimide ring F was synthesized. The N-formylamino group of NB-506 has been replaced with a more hydrophilic group, N-bis(hydroxymethyl)methylamino. In this study we show that the incorporation of a longer substituent on the N6 position effectively reinforces both the interaction with DNA and the capacity of the drug to maintain the integrity of the topoisomerase I-DNA covalent complexes. The strength and the mode of binding of the drugs to DNA were studied by complementary biophysical techniques including absorption, fluorescence, and circular and linear dichroism. Various biochemical procedures were applied to investigate the effects on human topoisomerase I using plasmid DNA as well as restriction fragments. The drug binding sites and the positions of the topoisomerase I-mediated cleavage sites were mapped with nucleotide resolution using footprinting and sequencing techniques. Cytotoxicity measurements performed with various human cancer cell lines (HCT-116, DLD-1, MKN-45) indicate that the newly designed drug is 3 to 4 times more toxic to colon and gastric cancer cells than NB-506. Therefore, the results suggest that the antitumor activity of indolocarbazole-based drugs can be enhanced by incorporating DNA and/or topoisomerase I reactive groups. They also support the hypothesis that the substituent on the imide nitrogen on the F ring of NB-506 has direct interaction with the molecular target. The study helps to define the structure-activity relationships in the indolocarbazole series of antitumor agents targeting topoisomerase I.

Animals↗
PubMed1999

The camptothecin-resistant topoisomerase I mutant F361S is cross-resistant to antitumor rebeccamycin derivatives. A model for topoisomerase I inhibition by indolocarbazoles.

DNA topoisomerase I is a major cellular target for antitumor indolocarbazole derivatives (IND) such as the antibiotic rebeccamycin and the synthetic analogue NB-506 which is undergoing phase I clinical trials. We have investigated the mechanism of topoisomerase I inhibition by a rebeccamycin analogue, R-3, using the wild-type human topoisomerase I and a well-characterized recombinant enzyme, F361S. The catalytic activity of this mutant remains fully intact, but the enzyme is resistant to inhibition by camptothecin (CPT). Here we show that the mutated enzyme is cross-resistant to the rebeccamycin analogue. Despite their profound structural differences, CPT and R-3 interfere similarly with the activity of the wild-type and mutant topoisomerase I enzymes, and the drug-induced cleavable complexes are equally sensitive to the NaCl concentration. CPT and IND likely recognize identical structural elements of the topoisomerase I-DNA covalent complex; however, differences do exist in terms of sequence-specificity of topoisomerase I-mediated DNA cleavage. For the first time, a molecular model showing that CPT and IND share common steric and electronic features is proposed. The model helps to identify a specific pharmacophore for topoisomerase I inhibitors.

Amino Acid Substitution↗
PubMed1999

Stimulation of topoisomerase II-mediated DNA cleavage by three DNA-intercalating plant alkaloids: cryptolepine, matadine, and serpentine.

Cryptolepine, matadine, and serpentine are three indoloquinoline alkaloids isolated from the roots of African plants: Cryptolepis sanguinolenta, Strychnos gossweileri, and Rauwolfia serpentina, respectively. For a long time, these alkaloids have been used in African folk medicine in the form of plant extracts for the treatment of multiple diseases, in particular as antimalarial drugs. To date, the molecular basis for their diverse biological effects remains poorly understood. To elucidate their mechanism of action, we studied their interaction with DNA and their effects on topoisomerase II. The strength and mode of binding to DNA of the three alkaloids were investigated by spectroscopy. The alkaloids bind tightly to DNA and behave as typical intercalating agents. All three compounds stabilize the topoisomerase II-DNA covalent complex and stimulate the cutting of DNA by topoisomerase II. The poisoning effect is more pronounced with cryptolepine than with matadine and serpentine, but none of the drugs exhibit a preference for cutting at a specific base. Cryptolepine which binds 10-fold more tightly to DNA than the two related alkaloids proves to be much more cytotoxic toward B16 melanoma cells than matadine and serpentine. The cellular consequences of the inhibition of topoisomerase II by cryptolepine were investigated using the HL60 leukemia cell line. The flow cytometry analysis shows that the drug alters the cell cycle distribution, but no sign of drug-induced apoptosis was detected when evaluating the internucleosomal fragmentation of DNA in cells. Cryptolepine-treated cells probably die via necrosis rather than via apoptosis. The results provide evidence that DNA and topoisomerase II are the primary targets of cryptolepine, matadine, and serpentine.

Alkaloids↗
PubMed1999

Intercalation into DNA is not required for inhibition of topoisomerase I by indolocarbazole antitumor agents.

The DNA-intercalating antitumor drug NB-506 is a potent topoisomerase poison currently undergoing phase I/II clinical trials. It contains a planar indolocarbazole chromophore substituted with a glucose residue. Up until now, it was thought that intercalation of the drug into DNA was essential for the stabilization of topoisomerase I-DNA covalent complexes. But, in the present study, we show that a regio-isomeric form of NB-506 has lost its capacity to intercalate into DNA, but remains an extremely potent topoisomerase I poison. The new analogue contains two hydroxyl groups at positions 2,10 instead of positions 1,11 in NB-506. The relocation of the two OH groups reduces considerably the strength of binding to DNA and prevents the drug from intercalating into the DNA double helix. However, the topoisomerase I inhibition capacity of the new analogue remains very high. The two drug isomers are equally potent at maintaining the integrity of the topoisomerase I-DNA covalent complexes, but stimulate cleavage at different sites on DNA. NB-506 stabilizes topoisomerase I preferentially at sites having a pyrimidine (T or C) and a G on the 5' and 3' sides of the cleaved bond, respectively. The 2,10-isomer induces topoisomerase I-mediated cleavage only at TG sites and, thus, behaves exactly as the reference topoisomerase I poison camptothecin. Finally, cytotoxicity measurements performed with a panel of murine and human cancer cell lines reveal that the newly designed drug is considerably (up to 100-fold) more toxic to tumor cells than the parent drug NB-506. We conclude that the DNA-binding and topoisomerase I poisoning activities of NB-506 can be viewed as two separate mechanisms.

Animals↗