RESUMEN
Following the demonstration that addition of a 2-cyano group to aziridines prevented DNA alkylation and thus reduced toxicity, many novel 2-cyanoaziridines were synthesized and evaluated as immunomodulating and antitumor agents. They typically reacted with thiols such as cysteine, depleting them and allowing the accumulation of reactive oxygen species. Two of these compounds, azimexon and ciamexon, showed activity against tumors in clinical trials. Imexon was produced by cyclization of 2-cyanoaziridine-1- carboxamide in the presence of hydroxide ions. The two enantiomers were prepared by a process involving chiral chromatography. They were equipotent against cultured tumor cells. Imexon also reacts with thiols and it is especially potent against multiple myeloma in cell cultures. An efficient chemical synthesis and a lyophilization formulation of imexon as a water soluble, injectible drug, were developed. In Phase I and I/II clinical trials imexon showed hints of activity against a variety of tumors, but a randomized double-blind Phase II trial of imexon plus gemcitabine versus gemcitabine alone in pancreatic cancer showed no enhancement of activity above that of gemcitabine alone. This result was disappointing because in cell culture and mice the two compounds were synergistic. Based on a complete response in a Phase I trial, a new Phase II clinical trial of imexon is underway in non-Hodgkins lymphoma.
Asunto(s)
Antineoplásicos/química , Antineoplásicos/uso terapéutico , Aziridinas/química , Aziridinas/uso terapéutico , Hexanonas/química , Hexanonas/uso terapéutico , Animales , Antineoplásicos/farmacología , Aziridinas/farmacología , Ensayos Clínicos como Asunto , Hexanonas/farmacología , Humanos , Inmunomodulación/efectos de los fármacos , Ratones , Neoplasias/tratamiento farmacológicoRESUMEN
Three new types of amonafide and azonafide analogues were synthesized and screened in a panel of human solid tumor cells and murine L1210 leukemia cells. The structural types included tetrahydroazonafides, which have the naphthalene chromophore of amonafide within the anthracene nucleus of azonafide; phenanthrene analogues, in which the linear anthracene nucleus is replaced by the bent phenanthrene nucleus; and azaphenanthrenes. The tetrahydroazonafides were generally intermediate in potencies between amonafide and azonafide against the tumor cells, but some of them had high potencies against the L1210 cells and were more potent against the MDR strain than the sensitive strain. The phenanthrene and azaphenanthrene analogues showed no improvement on the potencies of the anthracenes.
Asunto(s)
Antineoplásicos/síntesis química , Imidas/síntesis química , Isoquinolinas/síntesis química , Fenantrenos/síntesis química , Adenina , Animales , Antineoplásicos/química , Antineoplásicos/farmacología , Ensayos de Selección de Medicamentos Antitumorales , Humanos , Imidas/química , Imidas/farmacología , Isoquinolinas/química , Isoquinolinas/farmacología , Ratones , Naftalimidas , Organofosfonatos , Fenantrenos/química , Fenantrenos/farmacología , Relación Estructura-Actividad , Células Tumorales CultivadasRESUMEN
The intracellular localization of 14 structurally unique azonafide analogs was studied to determine if intracellular drug distribution is the limiting factor in azonafide cytotoxicity. Using scanning laser confocal microscopy, cytotoxicity of the azonafide analogs studies was observed in Chinese hamster ovary cells immediately after a 1 h exposure. The intracellular drug distribution patterns varied significantly for different analogs. Eight analogs showed primarily nuclear localization, five analogs showed primarily cytoplasmic localization and two analogs displayed perinuclear localization. In general, the type of chemical substitution on the anthracene nucleus determined the distribution pattern. For example, for each analog seven of eight nuclear-localizing analogs were amine-substituted agents, while four of five cytoplasmic-localized agents were ethoxy-substituted analogs. The individual exception within these groups was the 6-[(dimethylamino)ethoxy] agent that was nuclear localized. The two perinuclear-localized agents included the unsubstituted parent, azonafide, and its 6-methyl azonafide analog. Comparison of the cytotoxicity of the azonafides, based on intracellular localization, revealed that none of the localization patterns were associated with increased cytotoxicity. These results show that minor structural changes in the azonafide class of antitumor agents involving substitution along an anthracene chromophore result in substantially different intracellular drug distribution patterns. However, these distribution differences do not determine relative cytotoxic potency in vitro.
Asunto(s)
Antineoplásicos/metabolismo , Antineoplásicos/toxicidad , Isoquinolinas/análisis , Isoquinolinas/metabolismo , Isoquinolinas/toxicidad , Análisis de Varianza , Animales , Antracenos/química , Antineoplásicos/química , Células CHO/efectos de los fármacos , Células CHO/metabolismo , Cricetinae , Citoplasma/metabolismo , Concentración 50 Inhibidora , Isoquinolinas/química , Isoquinolinas/farmacocinética , Microscopía Confocal , Naftalimidas , Relación Estructura-Actividad , Distribución TisularRESUMEN
A set of 20 2-cyanoaziridine-1-carboxamides was synthesized from 2-cyanoaziridine and appropriate isocyanates. These compounds were active against a variety of solid and hematological tumor cells in culture, including strains resistant to doxorubicin and mitoxantrone. Their potencies in these assays correlated with the lipophilicity of substituents. The N-phenyl derivative was more potent and equally effective to imexon, a cyclized 2-cyanoaziridine-1-carboxamide of clinical interest, against cloned fresh human tumors.
Asunto(s)
Antineoplásicos/farmacología , Aziridinas/farmacología , Antineoplásicos/química , Aziridinas/química , Ensayos de Selección de Medicamentos Antitumorales , Humanos , Relación Estructura-Actividad , Células Tumorales CultivadasRESUMEN
Azonafide (2-[2'-(dimethylamino)ethyl]-1,2-dihydro-3H-dibenz[de, h]isoquinoline-1,3-dione) is the parent of a new series of anthracene-containing antitumor agents. Its structure is based on amonafide but lacks a primary amine and has an anthracene chromophore rather than a naphthalene chromophore. Using a rat liver cytosol incubation and HPLC/MS detection, we have identified four metabolites resulting from in vitro metabolism of azonafide. These alkyl-modified derivatives include a mono- and a di-N'-desmethyl metabolite, an N'-oxide metabolite, and a carboxylic acid metabolite. Purified samples of these metabolites were analyzed for cytotoxic activity using a 3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyl-2H-tetrazolium vital dye (mitochondrial reductase) assay and for inhibition of topoisomerase II (TOPO II) using a cell-free enzymatic system. Each metabolite had decreased cytotoxicity relative to azonafide with the following relative potencies in descending order: the mono-N'-desmethyl metabolite, di-N'-desmethyl metabolite, the N-oxide metabolite, and the carboxylic acid metabolite. Similarly, the N'-desmethyl metabolites retained TOPO II inhibitory activity but with lower potency than azonafide. The N-oxide and carboxylic acid metabolites did not inhibit TOPO II at 0. 05 and 0.5 microg/ml, respectively. Thus, metabolism of azonafide by rat liver cytosol represents a detoxification pathway rather than a bioactivation scheme for this DNA intercalator.
Asunto(s)
Inactivación Metabólica/fisiología , Isoquinolinas/metabolismo , Hígado/enzimología , Animales , Antineoplásicos/metabolismo , Antineoplásicos/toxicidad , Células CHO , Cromatografía Líquida de Alta Presión , Cricetinae , Citosol/enzimología , ADN-Topoisomerasas de Tipo II/metabolismo , ADN Superhelicoidal/metabolismo , Sustancias Intercalantes/metabolismo , Sustancias Intercalantes/toxicidad , Isoquinolinas/toxicidad , Hígado/metabolismo , Espectrometría de Masas , Estructura Molecular , Naftalimidas , Ratas , Sales de Tetrazolio/metabolismo , Tiazoles/metabolismoRESUMEN
Three different types of 1,4-disubstituted anthracenes were synthesized, and their cytotoxicity in a panel of tumor cells was compared with that of the corresponding 9,10-disubstituted anthracenes. The panel contained human myeloma, melanoma, colon, and lung cancer cells and sensitive and multidrug-resistant murine L1210 leukemia cells. These compounds had [[(dimethylamino)ethyl]amino]methyl, N-[(dimethylamino)ethyl]carbamoyl, and carboxaldehyde (4,5-dihydro-1H-imidazol-2-yl)hydrazone side chains. The 1,4-diamide was more potent across the tumor panel than the corresponding 9,10-isomer, but the 1,4-diamine and the 1,4-hydrazone were less potent than their 9,10-isomers. Although the 1,4-hydrazone was active against P388 leukemia in mice, it was inactive against L1210 leukemia. Within each pair of compounds, the one with greater average potency against tumor cells gave a greater increase in the transition melt temperature of DNA.
Asunto(s)
Antracenos/síntesis química , Antracenos/farmacología , Antineoplásicos/síntesis química , Antineoplásicos/farmacología , Animales , Resistencia a Antineoplásicos , Ensayos de Selección de Medicamentos Antitumorales , Humanos , Ratones , Relación Estructura-Actividad , Células Tumorales Cultivadas/efectos de los fármacosRESUMEN
New 2-[2'-(dimethylamino)ethyl]-1,2-dihydro-3H-dibenz[de,h]isoquinoline-1,3- diones with substituents at the 4, 8, 9, 10, and 11 positions were synthesized. Diazonium salts prepared from aminoazonafides were key intermediates for many of the analogues. Six of the new compounds were more potent than azonafide in a panel of tumor cells including human melanoma and ovarian carcinoma and murine L1210 leukemias. Three of these compounds, the 10-OCH3, 10-OC2H5, and 10-F analogues, had better ratios of cardiotoxicity to tumor-cell toxicity than azonafide. Eight compounds were not cross-resistant with MDR L1210 leukemia, and the 10-CN analogue was more potent against solid tumor cells than leukemia cells. The 9-OH, 10-CN, and 10-F analogues had high potency against both sensitive and resistant cell lines of MFX 7 breast carcinoma and WiDr colon carcinoma and sensitivity A599 lung carcinoma. Advantages of the 10-Cl, 10-NH2, and 10-CN analogues over azonafide were apparent in P388 leukemia in mice, and the 10-CN analogue was more effective than doxorubicin in this assay. Quantitative structure-activity relationship studies revealed statistically significant correlations between DNA binding strength of 8- and 10-substituted azonafides, as measured by deltaTm, and toxicity to tumor cells. There also were correlations between substituent size, as measured by MR, and cytotoxicity for 9- and 10-substituted azonafides and between MR and deltaTm for 4- and 11-substituted azonafides. Lipophilicity of substituents (pi) correlated with cytotoxicity for 9-, 10-, and 11-substituted azonafides. These results lend support to a model in which DNA binding strength influences cytotoxic potency, and lipophilicity increases DNA binding whereas large substituents decrease it.
Asunto(s)
Antineoplásicos/síntesis química , Isoquinolinas/síntesis química , Animales , Antineoplásicos/química , Antineoplásicos/farmacología , Humanos , Isoquinolinas/química , Isoquinolinas/farmacología , Espectroscopía de Resonancia Magnética , Ratones , Relación Estructura-Actividad , Células Tumorales CultivadasRESUMEN
New 2-[2'-(dimethylamino)ethyl]-3H-dibenz[de,h]isoquinoline-1,3-diones with substituents at the 6- and 7-positions were prepared. Nucleophilic aromatic displacement was a key reaction in the syntheses. Ten of the new compounds were more potent than the unsubstituted compound, azonafide, in a panel of tumor cells including human melanoma and ovarian cancer and murine sensitive and MDR L1210 leukemia. They also were less cardiotoxic in cell culture. Four of these compounds were not cross-resistant with the MDR leukemia, and one of them, 6-ethoxyazonafide, was nearly as potent against solid tumor cells as leukemia cells. These compounds also had good potency against human breast, colon, and lung cancer cells, including doxorubicin and mitoxantrone resistant cell lines. Advantages of the new analogues over azonafide were less in vivo, but 6-ethoxyazonafide was more effective against L1210 leukemia and subcutaneous B16 melanoma in mice. Although correlations of antitumor potency in cells and physicochemical properties of substituents were not found, there were statistically significant correlations of DNA melt transition temperature (delta Tm) with potency in solid tumor cells and sensitive and MDR resistant L1210 leukemia cells for 6-substituted azonafides and with solid tumors for 7-substituted azonafides.
Asunto(s)
Antineoplásicos/síntesis química , Isoquinolinas/síntesis química , Animales , Antineoplásicos/farmacología , Humanos , Masculino , Ratones , Ratones Endogámicos DBA , Relación Estructura-Actividad , Células Tumorales CultivadasRESUMEN
Intercalative binding of the antitumor drugs amonafide and azonafide to the oligonucleotide duplex d(GGCCGGCCGG).d(CCGGCCGGCC) was compared using molecular dynamics in vacuum with the AMBER force field. A number of reasonable possible binding conformations were obtained, with the azonafide complexes favored over the amonafide complexes in net binding enthalpy. In comparison with amonafide, the larger chromophore of azonafide permits greater DNA distortion and wider side-chain swings, without falling out of the intercalation site. The best model obtained was used for further dynamics on amonafide and azonafide with solvent and counterions present, and again the azonafide complex had a more favorable enthalpy. Furthermore, the enthalpy change on going from solvent into the intercalation site was less unfavorable for azonafide. These results are consistent with the stronger DNA binding of azonafide compared to amonafide, as observed in relative melting transition temperature increases and tumor inhibition in cell cultures.
Asunto(s)
ADN/química , Imidas/química , Sustancias Intercalantes/química , Isoquinolinas/química , Oligodesoxirribonucleótidos/química , Adenina , Secuencia de Bases , Sitios de Unión , Calorimetría , Simulación por Computador , ADN/metabolismo , Enlace de Hidrógeno , Conformación Molecular , Datos de Secuencia Molecular , Estructura Molecular , Naftalimidas , Conformación de Ácido Nucleico , OrganofosfonatosRESUMEN
Sets of 2-[2-(dimethylamino)ethyl]-1,2-dihydro-3H- dibenz[de,h]isoquinoline-1,3-diones with amino and actylamino groups at each of the eight positions on the anthracene nucleus were synthesized from appropriately substituted anthracenes. Their evaluation in in vitro antitumor and cardiotoxicity assays revealed a very strong dependence of potency on the position of substitution. Certain compounds, including the 4-, 5-, 7-, and 9-amino derivatives, showed significantly higher potency than the unsubstituted parent compound, azonafide. Among them, 7-aminoazonafide had low cardiotoxicity relative to cytotoxicity. In general, the acetylamino analogues were less potent than the amino derivatives against tumor cells and neonatal rat heart myocytes; however, 5-(acetylamino)azonafide was highly cardiotoxic. 9-Aminoazonafide was more efficacious than azonafide or amonafide against P388 leukemia in mice. Statistically significant correlations were made between the ability of amino analogues to increase the transition melt temperature (delta Tm) of DNA and their potency against solid tumors, leukemia cells, or cardiac myocytes.
Asunto(s)
Antineoplásicos/síntesis química , Antineoplásicos/farmacología , Isoquinolinas/síntesis química , Isoquinolinas/farmacología , Adenina , Animales , Antineoplásicos/toxicidad , Bovinos , Neoplasias del Colon/tratamiento farmacológico , ADN/metabolismo , Doxorrubicina/farmacología , Doxorrubicina/toxicidad , Cardiopatías/inducido químicamente , Humanos , Imidas/farmacología , Imidas/toxicidad , Isoquinolinas/toxicidad , Leucemia P388/tratamiento farmacológico , Masculino , Ratones , Ratones Endogámicos DBA , Mitoxantrona/farmacología , Mitoxantrona/toxicidad , Naftalimidas , Organofosfonatos , Relación Estructura-Actividad , Células Tumorales CultivadasRESUMEN
A new class of antitumor agents, having structural analogy to amonafide, but differing by the addition of a fourth ring in the nucleus, was synthesized conveniently from anthracene. Compounds with a variety of substituents, containing a basic nitrogen atom and located on the imide nitrogen, were prepared. Thirteen of 19 new compounds had greater growth inhibitory potency than amonafide in a panel of cultured murine and human tumor cells using the sulforhodamine B and MTT dye assays. The most active agents were similarly more toxic than amonafide to normal neonatal rat myocytes in vitro, but they had better chemotherapeutic indexes. From these compounds, the one with a 2-(dimethylamino)ethyl side chain (named azonafide) was chosen for further study. It showed high potency against a panel of cultured human colon cancer cells and it was active against ip P388 leukemia and subcutaneous B16 melanoma in mice. Preliminary structure-activity correlations suggest that the basicity of the side-chain nitrogen and the length of side chain are important determinants of antitumor potency in vitro. Steric hindrance and rigidity of the side chains might be other determinants.
Asunto(s)
Antineoplásicos/síntesis química , Isoquinolinas/síntesis química , Animales , Antineoplásicos/química , Antineoplásicos/uso terapéutico , Femenino , Humanos , Isoquinolinas/química , Isoquinolinas/uso terapéutico , Leucemia L1210/tratamiento farmacológico , Leucemia P388/tratamiento farmacológico , Masculino , Melanoma Experimental/tratamiento farmacológico , Ratones , Ratones Endogámicos DBA , Neoplasias Ováricas/tratamiento farmacológico , Relación Estructura-Actividad , Células Tumorales Cultivadas/efectos de los fármacosRESUMEN
The alkylating antitumor agents mitomycin A (MMA), mitomycin C (MMC), and seven N7 analogs were compared in terms of their cardiotoxic and antitumor activity in vitro. Neonatal rat-heart myocytes were sensitive to five of the compounds studied, including MMA, 7-dimethylamidinomitosane (BMY-25282), 7-(N-methyl-piperazinyl)-mitosane (RR-194), N7-(4-iodophenyl)-MMC (RR-208), and N7-(4-hydroxyphenyl)-MMC (M-83) in order of descending molar potency. MMA and RR-208 possessed the greatest cytotoxic potency against 8226 human myeloma tumor cells in vitro. Two of the nine mitomycins studied, BMY-25282 and M-83, showed greater cytotoxic potency for heart cells. For these two agents, the ratio of the 50% inhibitory concentration in heart cells to that in 8226 myeloma cells was 50 and 32, respectively. For the other analogs, the tumor-cell cytotoxic potency was much higher (ranging from 200 to 7,000). For the nine mitomycin compounds, a correlation was found between heart-cell toxicity and low reduction potentials (E1/2 values) ranging from -0.16 to -0.37 V. Thus, as the reduction potential decreased (easier reducibility), the cardiotoxic potency in vitro increased (r = 0.81). In contrast, mitomycins with reduction potentials of higher than -0.37 V were much less potent cardiotoxins. Thus, mitomycin C (E1/2 = -0.45 V) was noncardiotoxic even when tested at concentrations 100-fold above those pharmacologically achievable in humans. Mitomycin C also failed to enhance doxorubicin (Adriamycin) cardiotoxicity in vitro. Importantly, no correlation was found between the reduction potential and the antitumor activity of the nine analogs (n = 0.51), in this small series.
Asunto(s)
Cardiopatías/inducido químicamente , Corazón/efectos de los fármacos , Mitomicina/toxicidad , Mitomicinas/toxicidad , Adenosina Trifosfato/metabolismo , Animales , Protocolos de Quimioterapia Combinada Antineoplásica/toxicidad , Depresión Química , Doxorrubicina/toxicidad , Femenino , Corazón/fisiología , Masculino , Mieloma Múltiple/tratamiento farmacológico , Contracción Miocárdica/efectos de los fármacos , Miocardio/citología , Proteínas/metabolismo , Ratas , Ratas Sprague-Dawley , Células Tumorales Cultivadas/efectos de los fármacosRESUMEN
We present molecular mechanics simulations on covalent complexes between d(GCGCGCGCGC).d(GCGCGCGCGC) in the left-handed double helical forms (B and Z) and potent antitumor antibiotics mitomycin C and three of its analogues using the all atom force field in the framework of the program AMBER(UCSF). The energy-refined models of the complexes show interesting networks of hydrogen-bonding interactions between the drugs and DNA groups in the minor groove of the left-handed helices. The energy-refined models suggest that mitomycins could bind strongly to left-handed helices. This result might be relevant to the interpretation of earlier experiments which suggested that DNA bound by mitomycin C underwent a transition to a non-Z left-handed structure.
Asunto(s)
ADN/metabolismo , Mitomicina/metabolismo , Mitomicinas , Secuencia de Bases , ADN/química , Modelos Moleculares , Datos de Secuencia Molecular , Conformación de Ácido Nucleico , TermodinámicaRESUMEN
Cytidine 5'-monophosphate and 5'-ara-CMP conjugates of 2,7-diaminomitosene, with the phosphate groups linked to C-1, were prepared by treating mitomycin C with the appropriate nucleotides. 5'-UMP conjugates were prepared from mitomycin A, 7 (M-83), and 8 (BMY-25282) by similar procedures. A conjugate could not be prepared from mitomycin C and 6-MPRP, but a sulfur-linked derivative was made with 6-MP ribonucleoside. The corresponding 1-hydroxy-2-aminomitosenes were prepared from the parent mitomycin analogues for structure-activity comparisons. All compounds were tested against L1210 murine leukemia in the MTT tetrazolium dye assay. In general, the conjugates were less potent than the parent mitomycins; however 5'-ara-CMP conjugate 14 derived from mitomycin C was more potent than the parent compound or any mitomycin tested except mitomycin A. It also was more potent than ara-C. This result establishes the value of this approach to prodrugs, at least in cell culture. Against a multi-drug-resistant L1210 cell line, all of the conjugates derived from mitomycin C were more potent than the parent compound. 6-Mercaptopurine ribonucleoside conjugate 15 was more active against the resistant cells than it was against the parental cell line.
Asunto(s)
Antineoplásicos/síntesis química , Mitomicinas/síntesis química , Nucleótidos/síntesis química , Animales , Antineoplásicos/uso terapéutico , Línea Celular , Fenómenos Químicos , Química , Leucemia L1210/tratamiento farmacológico , Ratones , Mitomicina , Mitomicinas/uso terapéutico , Nucleótidos/uso terapéuticoRESUMEN
A set of 30 mitomycin C and mitomycin A analogues, including five new compounds, was screened against three different solid human tumor cell lines using the MTT tetrazolium dye assay. A statistically significant correlation among antitumor activity, quinone reduction potential (E1/2), and the logarithm of the partition coefficient (log P) was obtained, with the most easily reduced and the most lipophilic compounds being the most potent. When these analogues were separated into mitomycin C and mitomycin A subsets, the former gave a correlation only with E1/2, whereas the latter (which differ little in their E1/2 values) gave a correlation only with log P. These correlations are in contrast to those made in the P388 leukemia assay in mice wherein the most active mitomycin C and mitomycin A analogues were the most hydrophilic ones. When the same compounds were tested against P388 leukemia cells in the MTT assay, the results were the same as those of the solid tumor assays. Thus, the substantial differences in relative potencies of mitomycins are related not to the kind of tumor cell, but to the type of assay performed, cell culture versus whole animal. No correlation was found between antitumor potency in the cell culture systems and calculated relative DNA binding strengths, probably because the limiting factors in antitumor potency of mitomycins appear to be tumor cell uptake (log P) and/or bioreductive activation (E1/2).
Asunto(s)
Mitomicinas/síntesis química , Animales , Neoplasias de la Mama/tratamiento farmacológico , Fenómenos Químicos , Química , Neoplasias del Colon/tratamiento farmacológico , Femenino , Humanos , Leucemia P388/tratamiento farmacológico , Ratones , Mitomicina , Mitomicinas/uso terapéutico , Modelos Moleculares , Neoplasias Ováricas/tratamiento farmacológico , Relación Estructura-Actividad , Células Tumorales CultivadasRESUMEN
The binding of Saframycin A to the octanucleotide duplex d(GATGCATC)2 was investigated using molecular dynamics. For covalent binding at N2 of the central guanine, only the R configuration at the alkylating carbon (C7) was permitted for B DNA and the 3' direction in the minor groove was preferred by 50.6 kcal/mol. The dihydroquinone form of saframycin A gave stronger binding than the quinone, in agreement with the literature. Addition of solvent and counterions made no significant change in the geometry model. The proposed mechanism of DNA alkylation, involving iminium ion intermediates from the dihydroquinone or quinone, was investigated by modeling these species. They gave models with good net binding enthalpies, and C7 was in close proximity to N2 of guanine. The noncovalent binding of saframycin A and its dihydroquinone in the vicinity of guanine also was favorable in the 3' direction.
Asunto(s)
Antibióticos Antineoplásicos/metabolismo , Simulación por Computador , Isoquinolinas/metabolismo , Modelos Moleculares , Oligonucleótidos/metabolismo , Polirribonucleótidos/metabolismo , Secuencia de Bases , Conformación Molecular , Datos de Secuencia Molecular , Estereoisomerismo , Relación Estructura-ActividadRESUMEN
Cyanocycline A was found to have a pKa of 6.6. Protonation of N14 was established by 1H NMR spectroscopy. In strongly acidic solution the oxazolidine ring opened irreversibly. A model was derived for the binding of naphthyridinomycin and cyanocycline A to the hexanucleotide duplex d(ATGCAT)2, by using the molecular mechanics and dynamics modules of AMBER 3.0. It involved protonation on the oxazolidine-ring nitrogen, reduction of the quinone ring to a hydroquinone, formation of an iminium ion with loss of the C7 substituent, noncovalent binding in the minor groove with the hydroquinone ring in the 3'-direction from guanine, and covalent binding to the 2-amino group of this guanine with C7 adopting the R configuration. This model is consistent with the experimental evidence on the DNA binding of these drugs. An alternative binding mode based on opening of the oxazolidine ring and alkylation at C3a also was feasible according to molecular mechanics calculations. The geometry of naphthyridinomycin does not permit interstrand cross-linking involving both C3a and C7, but formation of a cross-link to protein appears possible. When the covalent naphthyridinomycin-d(ATGCAT)2 models were refined in the presence of water and counterions, the models with the most favorable net binding enthalpies were the same as those produced by simulation in vacuum. Qualitative estimates of the relative entropy changes resulting from adduct formation were based on the number of ordered (hydrogen bonded) water molecules released from d(ATGCAT)2 and from the drug. In all cases but one, d(ATGCAT)2 loses five water molecules. It loses six in the C3a covalent model with 5',S geometry. Naphthyridinomycin hydroquinone loses up to two water molecules, depending on the particular adduct. The 3',R model was again favored for the C7 covalent adduct. Among the C3a covalent models, the one with 5',R geometry lost the second most water molecules, but it had the best binding enthalpy.
Asunto(s)
Antibacterianos/metabolismo , Simulación por Computador , ADN/metabolismo , Modelos Moleculares , Oligorribonucleótidos/metabolismo , Alquilación , Secuencia de Bases , Unión Competitiva , Fenómenos Químicos , Química , Espectroscopía de Resonancia Magnética , Datos de Secuencia Molecular , Naftiridinas/metabolismo , Estereoisomerismo , Relación Estructura-ActividadRESUMEN
The interaction of tomaymycin and 8-O-methyltomaymycin with calf thymus DNA was studied by steady-state fluorescence techniques. The 8-phenolic proton of tomaymycin has a pK = 8.0, and the phenolate anion is essentially nonfluorescent. However, the fluorescence of the DNA adduct does not decrease until pH greater than 10.5, when the DNA double helix denatures. Acrylamide quenches the fluorescence of the free antibiotic with a quenching rate constant kq = 7 x 10(9) M-1 s-1. In DNA adducts, the quenching rate constant is reduced about 50-fold, indicating that the aromatic ring of the drug is shielded from the solvent. The four possible binding modes of the antibiotics were modeled on a 6-mer duplex by molecular mechanics calculations in the absence and presence of water and counterions. The modeling studies show that the antibiotic is buried in the minor groove in all binding modes, with the 8-substituent pointing away from the DNA core. Three or five waters are displaced from the minor groove, depending on the orientation of the drug on the DNA.
Asunto(s)
ADN/química , Animales , Secuencia de Bases , Benzodiazepinonas/química , Benzodiazepinonas/metabolismo , Sitios de Unión , Bovinos , ADN/metabolismo , Enlace de Hidrógeno , Concentración de Iones de Hidrógeno , Modelos Moleculares , Conformación de Ácido Nucleico , Desnaturalización de Ácido Nucleico , Conformación Proteica , Termodinámica , Timo/química , Agua/químicaRESUMEN
To date, random anticancer drug screening has proven to be relatively inefficient and non-specific with respect to selecting active compounds for most tumor types (except for leukemia/lymphoma). Although large numbers of compounds from diverse sources were evaluated for many years in the P388 mouse leukemia model, only a few clinically useful drugs have been identified by this in vivo screening method. Thus, there is intense interest in the development of more effective in vitro screening models for new anticancer drugs. In the present paper we have compared the discriminating power for fresh human tumors from patients, human tumor cell lines developed from 11 patients and murine P388 leukemia in tumor colony forming assays as indicators of cytotoxicity for a series of anthracene antitumor agents. Two of a series of 21 novel bisantrene analogs, R6 (N,N1-bis[2-(dimethylamino)ethyl]-9,10-anthracene-bis(methylamine)) and R26 (N,N1-bis(1-ethyl-3-piperidinyl)-9,10-anthracene-bis(methylamine] produced significant cytotoxicity against the 11 human tumor cell lines and were therefore selected for additional in vitro and in vivo studies. R26 was specifically selected for further testing since it had similar in vitro potency as mitoxantrone, but showed no cross-resistance against mitoxantrone-resistant WiDr colon or doxorubicin-resistant 8226 myeloma cell lines. In contrast to the cell line data, only of the 22 fresh human tumors showed significant in vitro sensitivity (i.e. less than 50% survival of tumor colony forming units) to either R6 or R26 tested at high concentrations.(ABSTRACT TRUNCATED AT 250 WORDS)
Asunto(s)
Antracenos/farmacología , Antineoplásicos/farmacología , Leucemia P388/tratamiento farmacológico , Neoplasias/tratamiento farmacológico , Animales , Ensayos de Selección de Medicamentos Antitumorales , Humanos , Leucemia P388/patología , Ratones , Neoplasias/patología , Neoplasias Experimentales/tratamiento farmacológico , Neoplasias Experimentales/patología , Células Tumorales Cultivadas/efectos de los fármacosRESUMEN
The relative DNA binding strengths of bisantrene and nine new analogues were measured by spectrophotometric titration and melt transition temperature (Tm) techniques. Data from the spectrophotometric titrations could not be fit by simple Scatchard plots. However, they were fit by a McGhee-von Hippel equation over part of the binding range. The entire range of data was fit by a smoothing cubic spline function. The first derivative of this function gave, for each compound, a curve whose intercept provided a measure of relative binding strength. The delta Tm values agreed qualitatively with the spectrophotometric titration results, although there was not a precise linear relationship. Determinations of macroscopic pKas revealed that most of the compounds were dications at pH 7.0, but a few were mixtures of monocations and dications. No correlation was found between these binding studies and antitumor potencies in a clonogenic assay, which suggests that factors other than DNA binding can determine cytotoxicity for some of the analogues.