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C H Nguyen

Publications and source records attributed to C H Nguyen.

At least 37 records · Page 2Linked to original sources
PubMed1996

Ligand-induced formation of hoogsteen-paired parallel DNA.

INTRODUCTION: Based on molecular modeling studies, a model has been proposed for intercalation of triple-helix-specific ligands (benzopyridoindole (BPI) derivatives) into triple helices, in which the intercalating compounds interact mainly with the Hoogsteen-paired strands of the triple helix. We set out to test this model experimentally using DNA duplexes capable of forming parallel Hoogsteen base-paired structures. RESULTS: We have investigated the possible formation of a parallel DNA structure involving Hoogsteen hydrogen bonds by thermal denaturation, FTIR spectroscopy and gel-shift experiments. We show that BPI derivatives bind to Hoogsteen base-paired duplexes and stabilize them. The compounds induce a reorganization from a non-perfectly matched antiparallel Watson- Crick duplex into a perfectly matched parallel Hoogsteen-paired duplex. CONCLUSIONS: These results suggest that preferential intercalation of BPI derivatives in triple helices is due to their ability to interact specifically with the Hoogsteen-paired bases. The results are consistent with a model proposed on the basis of molecular modeling studies using energy minimization, and they open a new field of investigations regarding the biological relevance of Hoogsteen base-pairing.

DNA↗
PubMed1995

A new series of pyridinone derivatives as potent non-nucleoside human immunodeficiency virus type 1 specific reverse transcriptase inhibitors.

4-(Arylthio)-pyridin-2(1H)-ones variously substituted in their 3-, 5-, and 6-positions have been synthesized as a new series of 1-[(2-hydroxyethoxy)methyl]-6-(phenylthio)thymine (HEPT)-pyridinone hybrid molecules. Biological studies revealed that some of them show potent HIV-1 specific reverse transcriptase inhibitory properties. Compounds 16 and 7c, the most active ones, inhibit the replication of HIV-1 at 3 and 6 nM, respectively.

Antiviral Agents↗
PubMed1995

Synthesis and biological evaluation of amino-substituted benzo[f]pyrido[4,3-b] and pyrido[3,4-b]quinoxalines: a new class of antineoplastic agents.

In order to study the structure-activity relationships in the series of new intercalating polycyclic agents, 1-amino-substituted pyrido[3,4-b]quinoxalines, benzo[f]pyrido[4,3-b]quinoxaline derivatives bearing a dibasic side chain and their benzo[f]pyrido[3,4-b] isomers have been synthesized. Biological evaluation was carried out for topoisomerase I and II inhibition, and for in vitro and in vivo antitumor properties in several models. Results demonstrate that appropriately substituted benzo[f]pyrido[4,3-b]quinoxaline derivatives are inhibitors of topoisomerase I and II, and have significant antitumor properties in various experimental models. In addition, the most active compounds appear to be minimally recognized by tumor cells expressing the multidrug resistance phenotype.

Animals↗
PubMed1994

Molecular interactions of DNA-topoisomerase I and II inhibitor with DNA and topoisomerases and in ternary complexes: binding modes and biological effects for intoplicine derivatives.

Molecular interactions of intoplicine, dual DNA-topoisomerases (Topo) I and II inhibitor, with topoisomerases, plasmid DNA, in ternary cleavable complexes with enzymes and plasmid DNA, and in the reversed cleavable complexes were examined by means of surface-enhanced Raman scattering (SERS) and CD spectroscopy and by biochemical techniques. Detailed spectral analysis of intoplicine derivatives allowed us to assign SERS vibrational modes of chromophores and to propose the models for these complexes. Intoplicine was found to be able to interact specifically with the Topo II alone, but with Topo I only when in the presence of DNA. It shows at least two modes of binding to the DNA: the first was found to be dominant for its derivative 1c (most potent Topo I inhibitor), and the second was dominant for derivative 2a (most potent Topo II inhibitor). The possibility of forming these two types of complexes simultaneously is suggested to be one of the main factors enabling the drug to be a dual Topo I and Topo II inhibitor. The "deep intercalation mode" of the drug from the DNA minor groove with the long axis of the chromophore oriented roughly parallel to the dyad axis has been suggested to be responsible for induction of distortions of the DNA structure by the intercalating drug. Being involved in the formation of Topo I-mediated cleavable ternary complex, the molecules participating in the deep intercalation mode within the DNA do not change their molecular interactions as compared with their complex with the DNA alone. The stabilization of the Topo I-mediated cleavable complex was shown to be followed by the local denaturation of DNA in the AT-rich regions of the helix. When the ternary cleavable complex was reversed, the drug was shown to be in the complex with the plasmid. The "outside binding mode" from the DNA major groove via the hydroxyl group of the A-ring of the chromophore has been suggested to be responsible for Topo II inhibition. These molecules did not induce significant distortions of the DNA structure. Being involved in the formation of Topo II-mediated cleavable ternary complex, the drug changed its molecular interactions as compared with the complex with DNA alone.(ABSTRACT TRUNCATED AT 400 WORDS)

Binding Sites↗
PubMed1993

Intoplicine (RP 60475) and its derivatives, a new class of antitumor agents inhibiting both topoisomerase I and II activities.

Intoplicine (RP 60475, NSC 645008) is an antitumor derivative in the 7H-benzo[e]pyrido[4,3-b]indole series which is now being tested in clinical trials. Intoplicine strongly binds DNA (KA = 2 x 10(5) M-1) and thereby increases the length of linear DNA. These properties are consistent with DNA unwinding by intoplicine. Intoplicine was found to be a dual topoisomerase I and II inhibitor, with DNA sites of enzyme inhibition being different for these two enzymes. In this study, 22 analogues of intoplicine were evaluated for their effects on topoisomerase I- and II-mediated DNA cleavage reactions by using enzymes purified from calf thymus. Site-specific DNA cleavage mediated by topoisomerase I was observed with 7H-benzo[e]pyrido[4,3-b]indole derivatives but not with 11H-benzo[g]-pyrido[4,3-b]indole derivatives. Site-specific DNA cleavage mediated by topoisomerase II occurred with derivatives having hydroxyl groups at the 3-position on the 7H-benzo[e]pyrido[4,3-b]indole ring or at the 4-position on the 11H-benzo[g]pyrido[4,3-b]indole ring. Study of the relationships between the in vivo antitumor activity on P388 leukemia and the topoisomerase I- and/or II-mediated DNA cleavage activity revealed that the most highly active antitumor compounds possessed both topoisomerase I-and II-inhibitory properties. Compounds selectively inhibiting either topoisomerase I or II were less active. These results suggest that dual topoisomerase I and II inhibition is critical for the antitumor activity of this new series of antitumor compounds.

Animals↗
PubMed1993

Changes in the glycoforms of rat alpha-1-acid glycoprotein during experimental polyarthritis.

We analyzed the carbohydrate moiety of purified alpha-1-acid glycoprotein (AGP) from Lewis adult male rats that were healthy (AGPh) or had experimental polyarthritis (AGPi). Sodium dodecyl sulfate polyacrylamide gel electrophoresis before and after N-glycanase treatment showed that AGPi had a slightly lower molecular mass (43 kDa vs. 45 kDa for AGPh) due to a lesser carbohydrate content. Carbohydrate analysis of purified AGP showed a slight decrease in the sialyl and galactosyl molar ratio in polyarthritis. However, the same difference in AGPh and AGPi (i.e. 0.6 residue) between the sialyl and galactosyl molar ratio indicated more than one sialyl residue per complex-type branch. Affinity for concanavalin A (ConA) of the whole glycoprotein and released oligosaccharides showed a progression during polyarthritis towards more reactive glycoforms or more ConA-bound oligosaccharides. Anion-exchange HPLC of the ConA-fractionated oligosaccharides corroborated the decreased sialylation in polyarthritis. Taken together, these results suggest a fall in branched and sialylated oligosaccharides during experimental polyarthritis. These structural changes might be related to an increase in Gal beta 1-4GlcNAc alpha 2-6 sialyltransferase activity described elsewhere in inflammatory states.

Animals↗
PubMed1993

Characterization of a triple helix-specific ligand. BePI (3-methoxy-7H-8-methyl-11- [(3'-amino)propylamino]-benzo[e]pyrido[4,3-b]indole) intercalates into both double-helical and triple-helical DNA.

A benzo[e]pyridoindole derivative, 3-methoxy-7H-8-methyl-11-[(3'-amino)propylamino] -benzo[e]pyrido[4,3-b]indole (BePI), and its interactions with double and triple-helical DNA have been investigated by a variety of fluorescence, spectrophotometric, hydrodynamic and molecular modeling techniques. Binding to DNA stabilizes the doubly charged (+2) form of BePI, increasing the apparent pKa of the 10-NH proton by approximately 1 pH unit. Binding to DNA also quenches the fluorescence of BePI, with a greater extent of quenching upon binding triplex relative to duplex DNA. BePI preferentially binds (and stabilizes) triple-helical relative to double-helical DNA. This preferential binding is not restricted to triplexes containing solely T x A.T base triplets. In addition, BePI preferentially stabilizes the poly(dA).poly(dT) relative to the poly[d(A-T)].poly[d(A-T)] duplex. Viscosity studies demonstrate that, upon binding, BePI induces the unwinding of negative supercoils in the pBR322 plasmid, and increases the relative contour lengths of double and triple-helical polydeoxynucleotides. Fluorescence studies reveal that energy transfer occurs from polynucleotide bases to bound BePI molecules in both BePI/duplex and BePI/triplex complexes. In a BePI/triplex complex, an average of 4.8 bases appear to transfer excitation energy totally to a bound BePI molecule, while in various BePI/duplex complexes an average of only 2.5 bases appear to do so, indicating that energy transfer is more efficient in the former complex. Measurements of fluorescence quenching indicate that BePI is protected from quenching by acrylamide when bound to either double or triple-helical polynucleotides. The viscosity and fluorescence behavior of BePI are fully consistent with the conclusion that BePI intercalates into both double and triple-helical DNA. Molecular modeling studies suggest that stronger stacking interactions between intercalated BePI and adjacent bases in BePI/triplex relative to BePI/duplex complexes may account for the enhanced thermal stability of the former complex.

Base Sequence↗
PubMed1993

Antitumor activity of intoplicine (RP 60475, NSC 645008), a new benzo-pyrido-indole: evaluation against solid tumors and leukemias in mice.

Intoplicine (RP 60475, NSC 645008) is a new 7H-benzo[e]pyrido [4,3-b] indole derivative which interacts with DNA and inhibits both topoisomerases I and II. In vitro it was found cytotoxic against various cell types with greater cytotoxicity towards solid tumor cells. We report here the anticancer activity of RP 60475 against a variety of transplantable tumors of mice, and also its cross-resistance profile in leukemias. The end points used were % T/C (median tumor weight of the Treated over the Control x 100) and logCK (log10 cell kill total). RP 60475 administered i.v. was found schedule-independent with a peak plasma level problem. It had a good therapeutic index and host recovery usually occurred 7.5 days post last treatment. RP 60475 was found to be highly active against early stage colon 38 (T/C = 0%, 2.9 logCK) and could induce 5/5 complete regressions of advanced stage tumor. It was found active against colon adenocarcinoma 51 (T/C = 3.6%, 1.9 logCK) and colon carcinoma 26 (T/C = 11.7%, 1.2 logCK). Most of the mammary adenocarcinomas were found very responsive, MA16/C (T/C = 0%, 2.8 logCK), MA14/A (T/C = 0%, 1.4 logCK), MA13/C (T/C = 0%, 3.1 log CK) and MA44 (T/C = 34%). Excellent activity was also observed against early stage pancreatic ductal adenocarcinoma 03 (T/C = 0%) and RP 60475 could achieve 5/5 complete regressions of upstaged tumor. Activity was also obtained on Glasgow osteogenic sarcoma (T/C = 0%, 3.3 logCK), on B16 melanoma (T/C = 14%, 1.3 logCK) and to a lesser extent on Lewis lung carcinoma (T/C = 33.2%). Evaluation of RP 60475 against leukemia sublines with acquired resistance, revealed that L1210/cisplatin and L1210/BCNU were not cross-resistant to RP 60475 whereas P388/vincristine was partially cross-resistant to RP 60475 and P388/doxorubicin was cross-resistant to RP 60475. Based on RP 60475 broad activity against transplantable tumors of mice, its effectiveness against some resistant sublines, its original mechanism of action and its acceptable toxicological profile, this compound was selected for clinical trials.

Animals↗
PubMed1992

Triple helix-specific ligands.

A triple helix is formed upon binding of an oligodeoxynucleotide to the major groove of duplex DNA. A benzo[e]pyridoindole derivative (BePI) strongly stabilized this structure and showed preferential binding to a triplex rather than to a duplex. Energy transfer experiments suggest that BePI intercalates within the triple helix. Sequence-specific inhibition of transcription initiation of a specific gene by Escherichia coli RNA polymerase by a triplex-forming oligodeoxynucleotide is strongly enhanced when the triplex is stabilized by BePI. Upon irradiation with ultraviolet light, BePI induces covalent modifications of the target within the triple helix structure.

Base Sequence↗
PubMed1992

Further SAR in the new antitumor 1-amino-substituted gamma-carbolines and 5H-benzo[e]pyrido[4,3-b]indoles series.

Using previously described techniques, various new 1-amino-substituted 5H-pyrido[4,3-b]indoles (gamma-carbolines, gamma-C) and 5H-benzo[e]pyrido[4,3-b]indoles (BPI) have been synthesized and evaluated. For known compounds containing a 1-[(dimethylamino)propyl] group, 1a and 1b in the gamma-C series and 2 in the BPI series are the most active. Studies with newly synthesized derivatives show that: (i) in the gamma-C series, the 4-unsubstituted-8-hydroxy-compound was inactive, whereas the 4-unsubstituted-9-hydroxy-5H-benzo[e]pyrido[4,3-b]indole is active; (ii) the 4-ethyl-8-hydroxy-5H-pyrido[4,3-b]indole derivative retains antitumor properties, but the 1-amino-substituted 4-ethyl-9-hydroxy-5H-benzo[e]pyrido[4,3-b]indole analog is devoid of biological activity; (iii) in the 5H-benzo[e]pyrido[4,3-b]indole series, the displacement of a hydroxyl group from the 9- to 10-position leads to inactive compounds. Based on the structural analogies, these results were unexpected because the same substituents on the 4-position lead to different biological properties in the two series.

Animals↗
PubMed1992

Synthesis and antitumor properties of new 4-methyl-substituted- pyrido[4,3-b]indoles (gamma-carbolines).

A new class of antineoplastic agents, 4-methyl-pyrido[4,3-b]indoles (5) and the related 4-hydroxymethyl derivatives (7), has been synthesized by a new pathway. Key transformations include regiospecific chlorination at the C(4)-position of 3-nitro-4-hydroxy-5-methyl-pyridin-2-(1H)-one (11) and photochemical cyclization of the intermediate triazolopyridones (15). This new synthesis was developed since an attempt to prepare 4-hydrazino-5-ethoxymethyl-pyridin-2-(1H)-one (10b) by the method previously used to obtain 4-hydrazino-5-methyl-pyridin-2-(1H)-one (10a) failed. The biological results obtained in different in vitro and in vivo models indicate that the substitution of the 4-CH3 by a 4-CH2OH group leads to a decrease of the antitumor properties.

Animals↗
PubMed1990

Stimulation by gamma-carboline derivatives (simplified analogues of antitumor ellipticines) of site specific DNA cleavage by calf DNA topoisomerase II.

gamma-Carbolines are tricyclic aromatic compounds which intercalate into DNA base pairs and exhibit significant cytotoxic and antitumor activities. These compounds which are structurally related to ellipticine by deletion of an aromatic ring, induce DNA breaks in cultured L1210 cells. Since the mechanism of cytotoxic activity of ellipticines involves DNA topoisomerase II, this enzyme might also be a target for gamma-Carbolines. We have tested this hypothesis using an in vitro system containing purified enzyme and pBR322 DNA. The ability of nine derivatives to stabilize the DNA-enzyme covalent complex was studied and compared to their cytotoxicity. The four less cytotoxic compounds do not induce cleavable complex to a significant extent. In contrast, the two most cytotoxic gamma-Carbolines are the most efficient stabilizers of the cleavable complex. The last three compounds exhibit an intermediate cytotoxicity and cleavage activity. In the presence of gamma-Carbolines, cleavage occurs predominantly at a single site in pBR322 which is one of the cleavage sites observed with ellipticines. The cleavage position was determined at the nucleotide level. The increased DNA cleavage specificity observed with gamma-Carbolines suggests that a tricyclic system is as efficient as ellipticines for DNA topoisomerase II cleavage at DNA sequences involved specifically in cytotoxic response. The data presented support the hypothesis that DNA topoisomerase II is a target involved in the mechanisms of action of antitumor gamma-Carbolines.

Amsacrine↗
PubMed1990

Synthesis and antitumor activity of 1-[[(dialkylamino)alkyl]amino]-4-methyl-5H-pyrido[4,3-b]benzo[e]- and -benzo[g])indoles. A new class of antineoplastic agents.

The thermal Fischer indolization of hydrazones resulting from 4-hydrazino-5-methyl-1H-pyridin-2-one and various beta- and alpha-tetralones led to 4-methyl-6,7-dihydro-2H,5H-pyrido[4,3- b]benzo[e]indol-1-ones and 4-methyl-11-dihydro-2H,5H-pyrido[4,3- b]benzo[g]indol-1-ones, respectively. After aromatization, these compounds were transformed by phosphorus oxychloride, giving 1-chloro-4-methyl-5H-pyrido[4,3- b]benzo[e]- and -benzo[g]indoles which were substituted by [(dialkylamino)alkyl]amines. The resulting 1-[[(dialkylamino)alkyl]amino]-4-methyl-5H-pyrido- [4,3-b]benzo[e]- and -benzo[g]indoles, as well as hydroxy derivatives obtained by demethylation of methoxylated compounds with hydrobromic acid, were tested for antitumor activity in vitro (leukemic and solid tumor cells) and in vivo on various experimental tumor models using the standard NCI protocols. 1-[[3-(Dialkylamino)propyl]-amino]-4-methyl-9-hydroxy-5H-pyrido[4,3- b]benzo[e]indoles appeared as a promising new class of antineoplastic agents.

Animals↗
PubMed1989

Interrelationship between affinity for DNA, cytotoxicity and induction of DNA-breaks in cultured L1210 cells for two series of tricyclic intercalators. Simplified analogues of ellipticine derivatives.

The interrelationship between affinity for DNA, cytotoxicity and induction of single-strand DNA breaks in cultured L1210 cells was studied for 21 compounds belonging to two series of tricyclic intercalators: 1-amino-substituted 4-methyl-5H-pyrido[4,3-b]indoles (gamma CARB) and 1-amino-substituted 4-methyl-5H-pyrido[3',4':4,5]pyrrolo[2,3-c]pyridines (PPP), which are simplified analogues of Ellipticine derivatives obtained by deletion of one cycle. Adriamycin, m-AMSA (4'-(9-acridinylamino) methanesulfon-m-anisidide), PZE (10-[diethylaminopropyl amino]-6-methyl-5H-pyrido[3',4':4,5]-pyrrolo[2,3-g] isoquinoline and RTE [( 1-(3-diethylaminopropylamino)-9-methoxy ellipticine, bimaleate) are used as reference compounds. The intercalation of these compounds into DNA was strongly suggested by three experimental observations: (i) the competitive inhibition of ethidium bromide intercalation, (ii) bathochromic and hypochromic effects on absorption spectra induced by DNA, and (iii) drug-induced increase of the DNA length, measured by viscosimetry. PPP derivatives are generally less cytotoxic and induce DNA breaks less efficiently than the gamma CARB ones, both in terms of maximum breakage frequencies and required drug concentrations. The most active compounds induced SSB in the DNA of L1210 cells, in a bell-shaped manner: the SSB frequency increased, rose to a maximum and then decreased as the drug concentrations increased. The maximum SSB frequencies induced by the most active compounds are of the same order as those of reference compounds Adriamycin and PZE. The structurally important requirements are essentially the same for both DNA breakage activity and cytotoxicity: (i) a N-CH3 in the 5-position, (ii) a CH3 in the 4-position, (iii) a hydroxy in the 8-position and (iv) the presence of an (aminoalkyl)amino side chain with preferentially a 3 carbon unit. There is no direct relationship between DNA affinity in vitro and induction of DNA breaks in cells, although a relatively high affinity seemed to be a necessary condition, since the most active compounds have the highest affinities and compounds having a very low affinity are totally inactive. The close correlation between cytotoxicity and extent of induction of DNA breaks suggests that these breaks may be in fact the lethal lesions responsible for cell death and thereby for the antitumor properties of these tricyclic intercalators.

Alkaloids↗
PubMed1988

1-Amino-substituted 4-methyl-5H-pyrido[4,3-b]indoles (gamma-carbolines) as tricyclic analogues of ellipticines: a new class of antineoplastic agents.

A series of 1-amino-substituted 4-methyl-5H-pyrido[4,3-b]indoles that are structurally related to ellipticines by deletion of a ring have been synthesized in order to evaluate their DNA affinity, their in vitro cytotoxicity on L1210 cultured cells, and their in vivo antitumor activity. Among 24 derivatives that have been prepared and studied for the structure-activity relationship in this new class of antineoplastic agents, those that have a NH(CH2)3N(R)2 side chain (R = CH3 or C2H5) at their 1-position, a 4-methyl group, and an 8-OH substituent, either with a 5-NH or with a 5-NCH3 group, show the most potent cytotoxicities on L1210 cultured cells and in vivo antitumor properties in P388 and L1210 leukemia systems. In vivo antineoplastic activity of the most potent products was confirmed in P388 and L1210 leukemia systems. In vivo antineoplastic activity of the most potent products was confirmed on other mouse experimental tumors from the standard NCI screening:B16 melanoma and C38 adenocarcinoma.

Alkaloids↗
PubMed1987

1-Amino-substituted 4-methyl-5H-pyrido[3',4':4,5]pyrrolo[3,2-c]pyridines: a new class of antineoplastic agents.

In an attempt to find new anticancer agents, a series of pyrido[3',4':4,5]pyrrolo[3,2-c]pyridines were synthesized and evaluated in the standard NCI screening. Among these new compounds, which are structurally related to 9-azaellipticines but differ by deletion of a cycle, those that have a 4-methyl group and a NHCH2CH2CH2NR2 side chain at the 1-position show significant cytotoxicity on L1210 cultured cells and antitumor properties in the in vivo P388 leukemia system. The in vivo antineoplastic activity of the most potent compounds were confirmed on the L1210 leukemia model.

Animals↗
PubMed1985

Erythrocyte malondialdehyde release in vitro: a functional measure of vitamin E status.

The definition for a sufficient vitamin E level has often been based on population studies that established the normal range of values for fasting plasma or serum vitamin E and more recently for vitamin E to total lipid ratios. These endpoints for vitamin E replacement strategies may not be readily achievable, particularly in the cholestatic patient for whom it is often impossible to reach and sustain normal levels even with massive doses of vitamin E. Vitamin E is believed to function as an antioxidant in vivo protecting membranes from lipid peroxidation. Malondialdehyde (MDA), a product of polyunsaturated fat peroxidation, was measured as the thiobarbiturate derivative in the supernatant following incubation of erythrocytes in hydrogen peroxide. The two different incubation conditions described here and the subsequent measurement of MDA appear to provide a sensitive functional assessment of vitamin E status. The clinical utility of this assay, which requires just 1.5 to 2.0 ml of whole blood, was demonstrated by comparing the percent of total MDA released from individuals regarded as vitamin E sufficient by conventional methods with vitamin E deficient subjects. The release of MDA from erythrocytes from vitamin E deficient subjects was clearly greater (44.1 +/- 18.8% vs 2.0 +/- 1.8%) than for control subjects (p less than 0.001).

Adolescent↗