Novel conformationally extended naphthalene-based inhibitors of farnesyltransferase.
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2-Naphthylamine↗
Biomedical subjects
A Commerçon
Publications and source records attributed to A Commerçon.
[3H](azidophenyl)ureido taxoid photolabels peptide amino acids 281-304 of alpha-tubulin.
The taxoid binding site on porcine brain tubulin was covalently labeled, in the presence or absence of Taxotere, with the photoaffinity reagent [3H]-p-(azidophenyl)ureido taxoid derivative [3H]TaxAPU [Combeau, C., Commercon, A., Mioskowski, C., Rousseau, B., Aubert, F., & Goeldner, M. (1994) Biochemistry 33, 6676-6683]. After disulfide reduction and carboxymethylation, the alkylated tubulin samples were treated with trypsin and the mixtures of peptides were first fractionated by gel filtration over Sephadex G50. Anion exchange chromatography of the radioactive areas showed, for one area, three major radioactive signals which were further analyzed by reversed phase C18 HPLC, leading to well-resolved radioactive peaks. Microsequencing of these different peaks gave a complete sequence of a tryptic fragment on alpha-tubulin (alpha-281-304) and two partial peptide sequences of a tryptic fragment on beta-tubulin (beta-217-229) in addition to sequences of mixture of peptides. The radioactive signals were lost while concentrating the samples for microsequencing, preventing the identification of the modified amino acids. These results identify the first peptide on alpha-tubulin which binds to the taxoids and confirm the involvement of both alpha- and beta-tubulin in the taxoid binding site.
Affinity Labels↗
Identification and properties of a major plasma metabolite of irinotecan (CPT-11) isolated from the plasma of patients.
Irinotecan [7-ethyl-10-[4-(1-piperidino)-1-piperidino]carbonyloxycamptothecin (CPT-11)] is a promising water-soluble analogue of camptothecin [S. Sawada et al., Chem. & Pharm. Bull. (Tokyo), 39: 1446-1454, 1991]. We have reported previously the presence of an important polar metabolite, in addition to 7-ethyl-10-hydroxycamptothecin (SN-38) beta-glucuronide, in samples of plasma taken from patients undergoing treatment with CPT-11 (L.P. Rivory and J. Robert, Cancer Chemother. Pharmacol. 36: 176-179, 1995; L. P. Rivory and J. Robert, J. Cromatogr., 661: 133-141, 1994). Plasma samples (0.5 ml) containing comparatively large amounts of this metabolite were extracted by solid-phase columns and subjected to high-performance liquid chromatography and mass spectrometry in parallel to fluorometric detection. The metabolite yielded [M + 1] ions with a m/z of 619, representing the addition of 32 atomic mass units to CPT-11. Purified fractions were subjected to proton nuclear magnetic resonance, and the structure determined, 7-ethyl-10-[4-N-(5-aminopentanoic acid)-1-piperidino]carbonyloxycampothecin (APC), was further validated following synthesis. Like CPT-11, APC was found to be only a weak inhibitor of the cell growth of KB cells in culture (IC50, 2.1 versus 5.5 micrograms/ml for CPT-11 and 0.01 microgram/ml for SN-38, the active metabolite of CPT-11) and was a poor inducer of topoisomerase I DNA-cleavable complexes (100-fold less potent than SN-38). In contrast to CPT-11, APC was not hydrolyzed to SN-38 by human liver microsomes or purified human liver carboxylesterase. Furthermore, APC did not inhibit the hydrolysis of CPT-11 in these preparations. Interestingly, APC was only a weak inhibitor of acetylcholinesterase in comparison to CPT-11 and neostigmine. It appears likely, therefore, that APC does not contribute directly to the activity and toxicity profile of CPT-11 in vivo.
Antineoplastic Agents, Phytogenic↗
Synthesis and biological evaluation of a new series of phenylhydroquinone derivatives as inhibitors of EGF-R-associated PTK activity.
In order to design new potent inhibitors of the epidermal growth factor receptor (EGF-R) associated protein tyrosine kinase (PTK) activity as antitumor agents, several families of phenylhydroquinone derivatives were synthesized. Some of these compounds were shown to block PTK activity in vitro, but also efficiently to inhibit EGF-stimulated DNA synthesis in ER 22 cells (CCL 39 hamster fibroblasts transfected with EGF-R) with IC50 values in the range 1-10 microM. In some cases, a correlation between the two sets of data was observed, allowing structure-activity relationships to be established. However, inhibitors which had in vitro specificity with regard to other kinases were not specific in the cellular test. Similar effects on DNA synthesis were observed after stimulation by various activating agents, suggesting that our compounds may also act against other cellular targets involved in the EGF-dependent pathways leading to cell proliferation.
Amino Acid Sequence↗
[Taxoids: structural and experimental properties].
Paclitaxel (Taxol) and docetaxel (Taxotere) are the first representatives of a new class of antitumor compounds. These two taxoids are clinically active against breast, ovarian and lung cancers. Taxoids are highly complex diterpenoids form natural origin. Preclinical and clinical developments have been made possible after a long and sustained chemical effort: paclitaxel is extracted from the barks of the Pacific yew tree Taxus brevifolia whereas docetaxel is prepared by hemisynthesis starting from 10-deacetyl-baccatin III, an inactive precursor found in the needles of the European yew tree Taxus baccata. These two drugs are active in various in vitro and in vivo preclinical models (cell lines, cloning of human tumor stem cells, murine grafted tumors, human xenografts). Taxoids constitute a new class of antimitotic agents different from vinca-alkaloids: on the one hand, paclitaxel and docetaxel can be considered as inhibitors of the reaction of depolymerization of microtubules into tubulin; on the other hand, vinca-alkaloids inhibit reaction of polymerization of tubulin into microtubules. An active program of medicine chemistry is done in various pharmaceutical and academic Institutions with two objectives: knowledge of structure-activity relationships and selection of new candidates for clinical trials.
Antineoplastic Agents, Phytogenic↗
Predominant labeling of beta- over alpha-tubulin from porcine brain by a photoactivatable taxoid derivative.
An [(azidophenyl)ureido]taxoid (TaxAPU) was synthesized in a radiolabeled form by coupling an aminotaxoid to tritiated N-methyl-N-(chloroformyl)-p-azidoaniline. TaxAPU was used to photolabel polymerized porcine brain tubulin. This newly synthesized probe possesses taxoid properties as demonstrated by its effect, in the absence of light, on the kinetics of tubulin assembly and microtubule disassembly and on the critical concentration of tubulin. TaxAPU apparently competes with Taxol for the same binding site with an equilibrium dissociation constant of 6 microM. The photoactivation of 266 nm of the radiolabeled probe in the presence of microtubules led to a covalent incorporation of radioactivity. Analysis of the radiolabeled polypeptides by electrophoresis under denaturing conditions revealed a specific incorporation of tritium in both the alpha-and beta-subunits of tubulin. A dependence on probe concentration was observed for the irreversible radioactivity incorporated into both subunits and maintained essentially a ratio of 2.5:1 between beta/alpha. Therefore, TaxAPU constitutes a true photoaffinity probe for the taxoid binding site on microtubules. Our results complement those reported by Rao et al. (1992) of photo-cross-linking experiments with unmodified Taxol.
Affinity Labels↗
Structure-activity relationships in a series of 5-[(2,5-dihydroxybenzyl)amino]salicylate inhibitors of EGF-receptor-associated tyrosine kinase: importance of additional hydrophobic aromatic interactions.
Potent inhibitors of EGF-dependent protein tyrosine kinase (PTK) activity were synthesized in a series of 5-[(2,5-dihydroxybenzyl)amino]salicylates. Several of these compounds inhibited EGF-dependent DNA synthesis in ER 22 cells with IC50 < 1 microM. In this series of PTK inhibitors, the role of the salicylate moiety as a potential divalent ion chelator was tested and found to be nonessential in all cases. The length and ramification of the substituting carboxyl group were investigated to improve cellular bioavailability, and this analysis provided compounds with increased inhibitory effect on EGF-induced DNA synthesis. Salicylates esterified with long hydrophobic chains were shown to be noncompetitive inhibitors of ATP, in contrast to the free acid and methyl salicylate. Moreover, all the tested inhibitors were shown to be noncompetitive inhibitors of the peptide substrate. Structure-activity relationships allowed us to suspect a hydrophobic pocket in the tyrosine kinase domain, preferentially interacting with aromatic rings. Finally, the selectivity of the best inhibitors was tested against other kinases, and they were found to be selective for tyrosine kinase. They were also shown to be good inhibitors of EGF-receptor autophosphorylation.
Animals↗
Selective inhibition of tyrosine protein kinase by a synthetic multisubstrate analog.
Synthetic compounds were designed in an attempt to mimic the possible transition state of tyrosine protein kinases. One representative compound (RP 53801) inhibited the enzyme purified from RSV-transformed cells. A serine/threonine kinase (kinase C) was 45 fold less sensitive. The inhibition was competitive with respect to ATP and noncompetitive with respect to the phosphate acceptor poly glu4-tyr1. The degree of inhibition (IC50 = 22 microM) was however lower than that expected from a transition state analog. The compound was capable of reducing tyrosine protein kinase activity in intact cells with some selectivity at 100 microM.
Adenosine Monophosphate↗