Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In order to study the mechanism of etoposide (VP-16) resistance in human tumor cells and to assess the role of P-170 glycoprotein in VP-16 accumulation, we have examined the uptake and efflux of VP-16 in both sensitive and multidrug-resistant MCF-7 human breast and HL60 human promyelocytic leukemia cells. The drug-resistant cells, MCF-7/ADR and HL60/ADR, were selected for resistance to adriamycin and were 200- to 250-fold resistant to VP-16. Whereas MCF-7/ADR cells overexpress the P-170 glycoprotein and show the multidrug-resistant phenotype, HL60/ADR cells do not overexpress the P-170 glycoprotein. Although there was a 2-fold decrease in accumulation of VP-16 in MCF-7/ADR cells, this decrease did not correlate with a 250-fold resistance to the drug. VP-16 efflux was rapid and almost complete from MCF-7 cell lines and it was decreased at 4 degrees. Further, there was a significant increase in VP-16 accumulation in the MCF-7/ADR cells in the presence of glucose-free medium supplemented with sodium azide. However, no change in the pattern of VP-16 efflux was observed. Under these conditions, addition of glucose caused release of VP-16 from MCF-7/ADR cells, suggesting energy-dependent modifications in the drug binding. Coincubation of vincristine with VP-16 also increased the drug accumulation and decreased the rate of efflux of VP-16 in both sensitive and resistant MCF-7 cells, suggesting that vincristine and VP-16 may compete for similar binding and efflux mechanisms in these cell lines. In contrast, daunorubicin increased VP-16 accumulation only in the sensitive MCF-7 cell line, whereas the efflux rate of VP-16 was not significantly changed in either cell line. HL60 sensitive cells accumulated 4- to 5-fold more VP-16 than the resistant subline. Both sensitive and resistant cells showed an important noneffluxable pool of the drug, 3-fold larger for sensitive cells (79 +/- 12 versus 25 +/- 2 pmol of VP-16/mg of protein, for sensitive and resistant cells, respectively). The efflux of VP-16 was temperature dependent only in sensitive cells. VP-16 accumulation in HL60/ADR cells was increased in glucose-free medium supplemented with sodium azide; however, the noneffluxable pool of VP-16 was not significantly changed. In contrast, although these conditions had no effect on the drug accumulation in the parental line, they caused a decrease in the noneffluxable pool of VP-16, suggesting an energy-dependent binding and retention of VP-16.(ABSTRACT TRUNCATED AT 400 WORDS)
Mol Pharmacol 1989 Mar
PMID:Role of differential drug uptake, efflux, and binding of etoposide in sensitive and resistant human tumor cell lines: implications for the mechanisms of drug resistance. 256 28

Doxorubicin (DXR) conjugated to murine monoclonal antibodies (MoAb) raised against human breast tumor cells demonstrated a MoAb-specific, molar ratio-dependent in vitro cytotoxicity. These conjugates were prepared on a scale sufficient to allow for subsequent clinical trials (1 to 3 g of MoAb per conjugation reaction). The conjugation reaction proceeded via an N-hydroxysuccinimide (NHS) active ester intermediate of cis-aconityl-DXR (CA-DXR), resulting in a cis-aconitate acid-sensitive linker between the DXR and MoAb. Molar ratios of DXR to MoAb ranged from 40 to 45. The immunoreactivity of conjugated MoAb was only slightly decreased from naked MoAb. When immunoconjugates were incubated with MoAb-reactive tumor cells for 3 hours, specific cell-killing was observed. If the exposure time was lengthened to 18 hours, however, nonspecific killing resulted. Incubation of the immunoconjugate with the nonspecific adsorbant Amberlite XAD-2 caused an average 30% decrease in the DXR-to-MoAb molar ratio, suggesting a population of drug that is tightly but noncovalently associated with MoAb.
Mol Biother 1989
PMID:Immunoconjugates of doxorubicin and murine antihuman breast carcinoma monoclonal antibodies prepared via an N-hydroxysuccinimide active ester intermediate of cis-aconityl-doxorubicin: preparation and in vitro cytotoxicity. 260 16

Doxorubicin, an anthracycline glycoside antibiotic which has been widely used for treatment of several types of cancer (Goormaghtigh and Ruysschaer, 1984), displays a clinically important cardiac toxicity (Young et al., 1981) that can be dissociated from the antitumor activity. Although the main sites of toxicity have been postulated to be on the muscle membranes (Goormaghtigh and Ruysschaer, 1984; Harris and Doroshow, 1985), no information is available for a direct doxorubicin effect on the Ca2+ fluxes in cardiac sarcoplasmic reticulum (SR). Previous studies have shown that micromolar doxorubicin triggers Ca2+ release from skeletal SR vesicles (Zorzato et al., 1985). The objective of this study was to examine the effect of doxorubicin or caffeine on Ca2+ fluxes in cardiac SR in the presence of various Ca2+ release inhibitors. Addition of either doxorubicin (C1/2 = 5 microM), or caffeine (C1/2 = 0.8 mM) triggered Ca2+ release from canine cardiac SR loaded with 45Ca2+ in the presence of 2 mM ATP. The maximal amount of Ca2+ release triggered by doxorubicin (38% of the total loaded Ca2+) was significantly higher than that released by caffeine (25%). Plots of the amount of Ca2+ release triggered by 20 microM doxorubicin or 2 mM caffeine vs. free Ca2+ concentration were a bell-shaped, with maximal Ca2+ release at 0.2 microM Ca2+. Ca2+ release triggered by either 20 microM doxorubicin or 2 mM caffeine was inhibited by ruthenium red (0.1 to 2 microM), ryanodine (1 to 100 microM) or tetracaine (0.1 to 1 mM), whereas 2 mM caffeine did not further activate Ca2+ release triggered by 50 microM doxorubicin, suggesting that the drugs may share the same Ca2+ release channel.
J Mol Cell Cardiol 1989 May
PMID:Doxorubicin-induced calcium release from cardiac sarcoplasmic reticulum vesicles. 277 2

Doxorubicin (Adriamycin) and daunomycin analogs have been examined for their ability to chelate iron and catalyze the oxidative cleavage of DNA. The results show that the C-11-hydroxyl group is essential for iron binding and DNA damage. Thus, the iron complexes of doxorubicin, daunomycin, carminomycin, and 4-demethoxydaunomycin are potent redox catalysts capable of reducing molecular oxygen in the presence of physiologic concentrations of glutathione. They are also effective catalysts of hydroxyl radical formation from hydrogen peroxide. With the exception of daunomycin, generation of hydroxyl radical from hydrogen peroxide is stimulated by greater than 200% by DNA addition. Analogs that lack the C-11-hydroxyl group are relatively inefficient at oxygen reduction, hydroxyl radical formation, and DNA cleavage. The potencies of the anthracycline analogs tested in the H2O2-dependent DNA cleavage reaction correlated well with their relative cardiac toxicities.
Mol Pharmacol 1985 Mar
PMID:Thiol-dependent DNA damage produced by anthracycline-iron complexes. The structure-activity relationships and molecular mechanisms. 298 84

Doxorubicin is an important anticancer drug that undergoes redox cycling leading to the production of oxygen radicals; however, its clinical use is limited by toxicity. Redox cycling due to doxorubicin was assessed in the perfused rat liver from increases in O2 uptake by the organ, and toxicity was determined from lactate dehydrogenase release and trypan blue uptake. Doxorubicin increased O2 uptake in a concentration-related manner with half-maximal increases at about 100 microM drug. Within 5 min after addition of 300 microM doxorubicin, lactate dehydrogenase was detected in the effluent perfusate. Enzyme release increased steadily and reached values of 600 units/liter after 60 min. Rates of O2 uptake due to redox cycling of doxorubicin (300 microM) increased by 57 mumol/g/hr in oxygen-rich (mean [O2] = 473 microM) periportal regions of the liver lobule, but did not change in pericentral regions where O2 tension was lower [( O2] = 247 microM). Concomitantly, fluorescence of NAD(P)H measured from the liver surface decreased in periportal but not pericentral regions. The zone-specific decrease in NADPH was attributed to redox cycling of doxorubicin. Trypan blue was taken up exclusively by cells in periportal regions of the liver lobule after perfusion with doxorubicin. When the average O2 tension was lowered from 550 to 200 microM, O2 uptake due to redox cycling of doxorubicin in periportal regions was reduced 3-fold and toxicity was abolished, indicating that toxicity due to doxorubicin is oxygen-dependent. Redox cycling of doxorubicin was minimal in regions of the perfused liver where the O2 concentration was below 400 microM. In contrast, isolated microsomes displayed maximal changes in O2 uptake due to redox cycling of doxorubicin at O2 tensions of about 10 microM. Thus, oxygen per se is not rate-limiting for redox cycling of doxorubicin in the intact organ. Since NADPH is also required for redox cycling of doxorubicin, the effect of oxygen on the ability of mitochondria and the pentose cycle to supply reducing equivalents for redox cycling of doxorubicin was examined. NADPH supply from the pentose cycle was reduced by fasting while that from mitochondria was inhibited by cyanide. The increase in O2 uptake due to redox cycling of doxorubicin was around 60 mumol/g/hr in livers from fed or fasted rats. In the presence of potassium cyanide, stimulation of O2 uptake by doxorubicin was reduced by about one-half in livers from fed rats (29 mumol/g/hr) yet was abolished nearly completely in livers from fasted rats (7 mumol/g/hr).(ABSTRACT TRUNCATED AT 400 WORDS)
Mol Pharmacol 1988 Nov
PMID:Oxygen-dependent hepatotoxicity due to doxorubicin: role of reducing equivalent supply in perfused rat liver. 319 59

Doxorubicin (Adriamycin), one of the most potent antibiotics used in tumor chemotherapy, shows many undesirable side effects. We studied the effect of different drug concentrations on the biochemistry of cell motility and, in particular, on potassium-induced actin polymerization. It is well known, in fact, that the actin aggregational status could dramatically influence many cell motility manifestations. Our results clearly show that stoichiometric and substoichiometric amounts of doxorubicin negatively influence actin polymerization by inhibiting both the filament growth and the polymer amount at steady-state; the balance between the two different effects seems to be in relation to the drug concentration. The obtained results could explain some of the doxorubicin effects previously observed in vivo.
Exp Mol Pathol 1988 Dec
PMID:Dose-dependence of doxorubicin effect on actin assembly in vitro. 319 12

Doxorubicin (Adriamycin, ADR) is an anthracycline antineoplastic with the serious side effect of dose-related cardiomyopathy. A model of ADR cardiotoxicity was created to examine some subcellular toxic effects of ADR with cultured cardiac myocytes (CMCs) exposed to 1 x 10(-7) to 1 x 10(-5) M ADR for 24 to 48 hr. Lactate dehydrogenase (LDH) activity was monitored in the CMC medium to monitor CMC damage as a function of ADR concentration. A four- to eightfold elevation of LDH activity in medium of CMCs exposed to 1 x 10(-6) to 1 x 10(-5) M ADR was found. No change in LDH activity was detected in medium of CMCs exposed to 1 x 10(-7) M ADR or in control CMCs after 24 or 48 h ADR exposure. Data suggest a dose-dependent effect of ADR on LDH activity in CMC medium. Serial monitoring of LDH in media of ADR-exposed CMCs may correlate with other evidence of ADR cardiotoxicity in vitro.
Exp Mol Pathol 1988 Jun
PMID:Lactate dehydrogenase activity in cultured neonatal rat heart cells exposed to doxorubicin. 337 55

Doxorubicin is metabolically activated by microsomal NADPH-dependent cytochrome P450 reductase as well as by intact nuclei forming semiquinone free radicals, which reoxidize to doxorubicin in the presence of oxygen. Nuclear activated doxorubicin became bound to DNA in a time-dependent fashion. The addition of microsomal protein to intact nuclei increased the amount of doxorubicin bound to DNA under aerobic conditions. In contrast, inclusion of microsomes virtually abolished DNA binding under anaerobic conditions. Disruption of the nuclear membrane by sonification increased the amount of drug bound to DNA, indicating that the nuclear envelope serves as a partial barrier to the diffusion of microsomal DNA-directed intermediates. The data indicate that under aerobic conditions metabolites produced by microsomes either traverse the nuclear membrane and bind to DNA or act indirectly by disrupting the nuclear membrane. In contrast, inhibition of DNA binding by doxorubicin under anaerobic conditions suggests either that the microsomal metabolites do not diffuse across the nuclear membrane or that the metabolites are not capable of binding to DNA. The decreased diffusibility of the anaerobic metabolites may represent either the generation of metabolites having lower diffusion constants or the formation of highly reactive intermediates which preferentially bind in the immediate vicinity to the site of generation on the microsomal surface. In conclusion, it appears that, under aerobic conditions, metabolic activation of doxorubicin on the surface of the endoplasmic reticulum can contribute to the amount of the drug which becomes closely associated with nuclear DNA. Consequently, the microsomal drug-metabolizing system may be important in affecting the therapeutic or cytotoxic properties of the drug.
Mol Pharmacol 1987 Mar
PMID:Oxygen-dependent effect of microsomes on the binding of doxorubicin to rat hepatic nuclear DNA. 356 86

Purified bovine cardiac G-actin was interacted with doxorubicin (Adriamycin, ADR), in absence of potassium or magnesium to study ADR's effects on actin polymerization. Actin with ADR (10(-6) M) was incubated with polylysine-coated polystyrene beads and filaments formed were visualized by negative staining electron microscopy (NSEM). ADR-induced actin polymerization was assessed biochemically by ultracentrifugation and analysis of protein content of the supernatant solution. Kinetic assays of turbidity of actin were performed which showed that ADR induced formation of stubby actin polymers which bound to the beads and differed ultrastructurally from the longer actin filaments induced by KCl + MgCl2. Actin content in the supernatant solution decreased after centrifugation (0.8 mg/ml in G-actin to 0.45 mg/ml in actin incubated with 10(-4) M ADR). ADR (10(-4) M) caused increased turbidity of actin of similar magnitude to that induced by actin + KCl + MgCl2. Data support the hypothesis that ADR induces polymerization of cardiac actin in vitro but this polymerization has characteristics which are different from actin polymerization induced by salts.
Exp Mol Pathol 1986 Feb
PMID:Cardiac actin interactions with doxorubicin in vitro. 394 80

Doxorubicin (adriamycin) forms molecular associations with other aromatic and planar molecules (hetero-association) and with other doxorubicin molecules (self-association) in aqueous solution. The ability of doxorubicin to form complexes was demonstrated in a nonbiological system by measuring the doxorubicin partition coefficient. A decreased apparent doxorubicin activity coefficient in the presence of complex formation was also demonstrated in a biological system by measuring the transmembranous doxorubicin transport and the doxorubicin distribution at equilibrium in human red blood cells and their suspending medium. Doxorubicin formed complexes in aqueous solution at 37 degrees (pH 7.3) with (a) DNA-derived bases, nucleosides, and nucleotides; (b) amino acids such as tryptophan; (c) proteins such as human serum albumin and hemoglobin; and (d) a broad range of biologically active compounds such as NAD, propanthelline, caffeine, chloroquine, imipramine, and propranolol. The apparent thermodynamic quantities of the complex formation with adenosine 5'-triphosphate were delta H0, -9.5 kcal . mole-1; delta S0, -19 eu . mole-1; and delta G0 (310 degrees K), -3.6 kcal . mole-1. The binding forces of the molecular associations were probably hydrophobic (short-range force), sometimes supported by electrostatic interaction (long-range force).
Mol Pharmacol 1982 Jul
PMID:Molecular association between doxorubicin (adriamycin) and DNA-derived bases, nucleosides, nucleotides, other aromatic compounds, and proteins in aqueous solution. 712 47


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