Histological Subtype of Ovarian Cancer as a Determinant of Sensitivity to Formamidine Derivatives of Doxorubicin - in Vitro Comparative Studies with SKOV-3 and ES-2 Cancer Cell Lines.

BACKGROUND: Development of new apoptosis-inducing drugs is a promising trend in anticancer therapy. For this purpose several formamidinoderivatives of doxorubicin were synthesized. The aim of our study was to investigate effects of the five formamidinodoxorubicins in the ES-2 human ovarian clear cell carcinoma line, for comparison with data obtained previously for SKOV-3 human ovarian adenocarcinoma cells, to answer the question of whether and to what extent the histological cell type is a possible determinant of sensitivity to tested anthracyclines. MATERIALS AND METHODS: In our experimental work the following methods were used: spectrophotometric assays with MTT; fluorimetric assays - double staining with Hoechst 33258 and propidium iodide (PI), measurement of caspase-3, -8, -9 activity, intracellular accumulation of DOX and analogues, estimation of drug uptake, mitochondrial transmembrane potential; flow cytometry - phosphatidylserine (PS) externalization with annexin V-FITC and PI fluorochromes. RESULTS: Effects of the derivatives of doxorubicin were partially linked with the specific type of cancer cell although intracellular accumulation and cellular uptake of DOX and derivatives were similar in both. All of the investigated derivatives were considerably more cytotoxic than DOX. Formamidinodoxorubicins were able to induce caspase-dependent apoptotic cell death in both cell types. CONCLUSIONS: All new formamidine derivatives of DOX were able to induce caspase - dependent apoptosis in human ovarian cancer cell lines SKOV-3 and ES-2. Obtained results suggested that formamidine derivatives of DOX may be promising candidates for the prospective chemotherapeutic agents for the two different histological subtypes of ovarian cancer.

Increased proapoptotic activity of electron beam irradiated doxorubicin and epirubicin in multidrug-resistant human leukemic cells.

This study evaluated the effect of electron beam irradiation on the cytotoxic activity of anthracycline antibiotics such as doxorubicin (DOX), epirubicin (EPI), and dunorubicin (DAU) in human acute lymphoblastic leukemia cell line CCRF-CEM and its multidrug-resistant variant CCRF-VCR1000 cell line characterized by the overexpression of ABCB1 gene. Drugs were irradiated at doses of 10 and 25 kGy. Data from EPR studies proved that the highest concentration of free radicals was found in DOX and that the number of stable free radicals is always greater after irradiation. In in vitro studies, a higher cytotoxic activity of irradiated DOX and EPI in multidrug-resistant CCRF-VCR1000 cells was observed. This tendency was maintained during the storage at 4 °C for 90 days. Changes in CCRF-CEM cells' viability were not dependent on the irradiation status and its dose and were only drug-concentration dependent in all measurement time points. It was proved that increased potency of 25 kGy e-beam irradiated drugs results from their enhanced proapoptotic activity. Apoptotic cell death observed in CCRF-VCR1000 cells treated with irradiated drugs was caspase-8, -9, and -3 dependent and related to the increased Bax/Bcl-2 ratio. No significant differences in the effects of irradiated and non-irradiated drugs on p53 and NFκB transcription factor level and their translocation to the nucleus were noted. Increased activity of the irradiated drugs was not dependent on ABCB1 level.

Nuclear accumulation of anthracyclines in the endothelium studied by bimodal imaging: fluorescence and Raman microscopy.

Anthracycline antibiotics display genotoxic activity towards cancer cells but their clinical utility is limited by their cardiac and vascular toxicity. The aim of this study was to develop a Raman-based methodology to study the nuclear accumulation of anthracyclines in the endothelium. For this purpose bimodal confocal Raman and fluorescence imaging was used to monitor cellular composition changes as a result of anthracycline exposure on endothelial cells (EA.hy926), and nuclear drug accumulation, respectively. Simultaneously effects of anthracyclines on endothelium viability were investigated by caspases-3 and -7 and MTT assays. We demonstrated that nuclear accumulation of DOX and EDOX was similar; however, EDNR accumulated in endothelial nuclei at concentrations 10 times higher than DNR. In turn, epimers of DOX or DNR were both consistently less toxic on the endothelium as compared to their congeners as evidenced by MTT and caspase assays. In summary, bimodal Raman and fluorescence-based nucleus profiling proves to be a valuable tool to study structure-activity relationship of nuclear accumulation and toxicity of anthracyclines in endothelium.

Radiation sterilization of anthracycline antibiotics in solid state.

The impact of ionizing radiation generated by a beam of electrons of 25-400 kGy on the stability of such analogs of anthracycline antibiotics as daunorubicin (DAU), doxorubicin (DOX), and epidoxorubicin (EPI) was studied. Based on EPR results, it was established that unstable free radicals decay exponentially with the half-time of 4 days in DAU and DOX and 7 days in EPI after irradiation. Radiation-induced structural changes were analyzed with the use of spectrophotometric methods (UV-Vis and IR) and electron microscope imaging (SEM). A chromatographic method (HPLC-DAD) was applied to assess changes in the contents of the analogs in the presence of their impurities. The study showed that the structures of the analogs did not demonstrate any significant alterations at the end of the period necessary for the elimination of unstable free radicals. The separation of main substances and related substances (impurities and potential degradation products) allowed determining that no statistically significant changes in the content of particular active substances occurred and that their conversion due to the presence of free radicals resulting from exposure to an irradiation of 25 kGy (prescribed to ensure sterility) was not observed.

A comparison of the stability of doxorubicin and daunorubicin in solid state.

The degradation of doxorubicin and daunorubcin in the solid state was studied using an HPLC method with UV detection (LiChrospher RP-18, 5 microm, 250 mm x 4 mm; mobile phase: acetonitrile-solution A 1:1, v/v (solution A: 2.88 g of laurisulfate sodium and 1.6 ml of phosphoric acid(V) in 1000 ml); flow rate - 1.4 ml min(-1); UV detection - 254 nm). The degradation of doxorubicin was a first-order reaction depending on the substrate concentration and daunorubicin degraded according to the kinetic model of autocatalysis. The dependence lnk(i)=f(1/T) was described by the equations lnk(DOX)=40.0+/-15.6-(19804+/-5682) (1/T) and lnk(DAU)=35.9+/-11.3-(16581+/-3972) (1/T) at 76.4% RH. The dependence lnk(i)=f(RH%) was described by the equations lnk(DOX)=(8.80+/-3.60) x10(-2) (RH%)-(21.50+/-2.57) and lnk(DAU)=(6.63+/-1.22)x10(-2) (RH%)-(13.35+/-1.68). The thermodynamic parameters (E(a,) DeltaH(not = a), DeltaS(not = a)) of the degradation of doxorubicin and daunorubicin were calculated. Although the degradation of doxorubicin was slower at increased temperature (353-373 K) and relative air humidity (50.9-90.0%), the differences between the influence of temperature and relative air humidity on the stability doxorubicin and of daunorubicin were not significant.

Cytotoxicity, cellular uptake and DNA damage by daunorubicin and its new analogues with modified daunosamine moiety.

Daunorubicin (DRB) and its two analogues containing a trisubstituted amidino group at the C-3' position of the daunosamine moiety have been compared regarding their cytotoxic activity, cellular uptake, subcellular localization and DNA damaging properties. An analogue containing in the amidino group a morpholine moiety (DRBM) as well as an analogue with a hexamethyleneimine moiety (DRBH), tested against cultured L1210 cells, exhibited lower cytotoxicity then DRB. The decrease of cytotoxic activity was not related to cellular uptake and subcellular localization of drugs. Although all tested drugs were active in the induction of DNA breaks and DNA-protein crosslinks, they differed in the mechanism of induction of DNA lesions. DRB produced DNA breaks mediated solely by topoisomerase II, whereas DRBM and DRBH induced two types of DNA breaks by two separate processes. The first is related to the inhibition of topoisomerase II and the second presumably reflects a covalent binding of drug metabolites to DNA. It is hypothesized that the replacement of the primary amino group (-NH(2)) at the C-3' position of the daunosamine moiety by a trisubstituted amidino group (-N=CH-NRR) may be a route to the synthesis of anthracycline derivatives with enhanced ability to form covalent adducts to DNA.

The method of daunorubicin purification.

The economical method of daunorubicin purification was evaulated.

Inhibition of RNA synthesis in vitro and cell growth by anthracycline antibiotics.

New derivatives of doxorubicin and daunorubicin with amidine group bonded to daunosamine at C-3' atom and bearing the morpholine ring attached to the amidine group have been recently synthesized. Their cytotoxic activities and effects on RNA synthesis in vitro were assayed. The drug concentrations inhibiting mouse leukaemia L1210 cell growth to 50% were about two- and three fold higher for the derivatives compared to doxorubicin and daunorubicin respectively. Inhibition of phage T7 RNA polymerase by the non-covalently interacting derivatives was also slightly lower than that by the parent compounds. As doxorubicin and daunorubicin, their amidine derivatives in the presence of dithiothreitol and Fe(III) ions are activated and covalently bind to DNA. The adducts formed affect RNA polymerase activity. Several bands corresponding to prematurely terminated RNA chains are observed by means of polyacrylamide gel electrophoresis. The patterns of bands are virtually identical for all the anthracyclines studied here and are similar to the terminations induced by actinomycin D. This observation is consistent with a notion that the adducts are formed at guanine in GpC sequences which are also binding sites of actinomycin D. A substantial difference between daunorubicin and its amidine derivative is shown by means of high performance liquid chromatography. The derivative undergoes rapid rearrangements in the presence of dithiothreitol and Fe(III) ions, while daunorubicin is stable for several hours under these conditions. The results presented here indicate that the amidine derivatives despite bulky morpholine substitution exhibit biological activity in the systems used here.

The ability of new formamidine sugar-modified derivatives of daunorubicin to stimulate free radical formation in three enzymatic systems: NADH dehydrogenase, NADPH cytochrome P450 reductase and xanthine oxidase.

Some sterically hindered N-substituted derivatives of daunorubicin are known to be poor substrates for NADH dehydrogenase, NADPH cytochrome P450 reductase and xanthine oxidase. In consequence, poor oxygen radical generation by these compounds is observed. In this study we examined a new family of sugar-N-substituted derivatives of daunorubicin bearing a bulky substituent introduced on the nitrogen atom through the amidine spacer. These compounds were found to be very active in radical formation catalyzed by all three studied enzymes. Thus, the introduction of a heterocyclic ring, even if it is bulky but flexible, on the nitrogen atom of daunosamine moiety through the one-atom spacer (amidine group), does not induce the steric hindrance effect on the interaction of daunorubicin derivatives with these flavoprotein enzymes.

Esters of cephalosporins. Part VI. Properties of the beta-form of 1-acetoxyethyl ester of cefuroxime.

Properties of a new crystalline beta-from of 1-acetoxyethyl ester of cefuroxime have been investigated and compared with known alpha-from and the amorphous form of this ester. Differences between these forms are discussed.

The bioavailability of injectable, amorphous form of aztreonam.

Amorphos injectable form of aztreonam (BIOKTAM) was prepared. It was shown that after intramuscular or intravenous administration there are not any considerable differences in the bioavailability of aztreonam from BIOKTAM and of the drug from AZACTAM.

Esters of cephalosporins. Part III. Separation and properties of the R and S isomers of the 1-acetoxyethyl ester of cefuroxime.

Two separation methods for the R and S isomers of the 1-acetoxyethyl ester of cefuroxime [I] were evaluated. Physico-chemical and biological properties of these isomers were studied. It was found that the R isomer after oral administration to rats is absorbed better and faster than the isomer S.

Esters of cephalosporins. Part IV. Hydrolysis of 1-acetoxyethyl ester of cefuroxime in vitro and in vivo.

Hydrolysis of 1-acetoxyethyl ester of cefuroxime [I] in blood was studied in vitro and in vivo. In vitro [I] hydrolyzes to biological active cefuroxime [II] and at the same time it undergoes isomerization to isomer delta 2 of 1-acetoxyethyl ester of cefuroxime [IV] and next hydrolyzes to biological inactive isomer delta 2 of cefuroxime [V]. As a result of hydrolysis [I] in vivo only [II] is formed.

Esters of cephalosporins. Part II. Differences in the properties of various forms of the 1-acetoxyethyl ester of cefuroxime.

Physico-chemical and microbiological properties of three different forms (crystalline and two amorphous ones) of the 1-acetoxyethyl ester of cefuroxime and bioavailability after oral administration to rats have been investigated. Relation between physico-chemical properties of these forms and their bioavailability is observed. It is shown, that for oral administration the most appropriate is an amorphous form obtained by rapid evaporation of a solvent from solution of the ester.

Esters of cephalosporins. Part I. Permeability of cefuroxime liberated from its 1-acetoxyethyl ester through biological membranes; influence of the form and size of the ester particles.

Concentrations of cefuroxime [II] in blood of rats were measured 30 and 60 min. after administration of amorphous form possessing various particles size (ranging from 0.09 to 0.4 nm) and crystal form of 1-acethoxyethyl ester of cefuroxime [I]. In vitro the concentrations of [II] were measured 15 and 45 min. after application of [I]. HPLC method was used for cefuroxime estimation. Close correlation between the particles size of the amorphous [I] and the concentrations of [II] in vivo as well as in vitro was found, the particles with lover size possessed higher bioavailability. The cefuroxime front the crystal form of ester is poorly absorbed and the concentrations of [II] after its application were similar to those observed after of the bigest particles of amorphous form both in vivo and in vitro.

The X-ray structural investigation of 6-(n,n-1,6-hexyleneformamidine)-penicillanic acid (mecillinam).

A new type of 6-formamidinepenicillanic acid in which the omega-nitrogen atom is involved in the azaheptane ring (mecillinam) having a strong selective activity against Gram-negative bacteria strains has been investigated by the X-ray single-crystal diffraction methods using crystals in the solvated state. The conformation of penam part as well as of the amidine group is discussed. Two independent molecules of mecillinam found in the asymmetric unit of the crystal cell differ from each other in their detailed conformations. The problem of the stability of the compound has been discussed also.