Comparison of the interaction of antineoplastic aminoanthraquinone analogs with DNA using competitive fluorescence polarization

1,4-dihydroxy-5, 8-bis{{2-{(2-hydroxyethyl)amino}ethyl}amino} -9,10-anthracenedione (NSC 287836) and 1,4-bis{{2-{(2-hydroxyethyl) amino}ethyl}amino}-9, 10-anthracenedione diacetate (NSC 287513) have shown activity against solid tumors and are now in Phase I clinical trials. Fluorescence polarization was used to determine the extent of inhibition of the binding of acridine orange to DNA (Richardson, Roboz, Holland, Res. Comm. Chem. Pathol. Pharmac. $\text{27}$, 497, 1980). Displacement of 50% of acridine orange from calf thymus DNA was obtained with 0.18 uM of NSC 287836 while 0.52 uM of NSC 287513 was needed to displace an equivalent amount of acridine orange. NSC 287513 showed preference for polynucleotides of high adenine+thymine content while NSC 287836 did not. Analogs lacking both hydroxyethylaminoethyl-amino side chains did not displace acridine orange.     

Luminescence absorption properties of the olivomycin molecule and its complex with DNA

Olivomycin (I) is a fluorescent probe which is highly specific with respect to DNA. Its luminescence-absorption properties were studied at various pH values, in different solvents and in the presence of Mg2+ and DNA in the solutions. The presence of 2 tautomeric forms of I was suggested on the basis of the study (forms A and B having different characteristics with respect to the absorption spectra and fluorescence). Transition between forms A and B occurred in both the basic and the excited states. The quantitative ratio of the forms depended on the character of the environment. The presence of the 2 forms of I should be considered in analysis of the drug pharmacokinetics and pharmacodynamics.     

Structure of the antineoplastic antibiotic variamycin]

The results of the structural study of antitumor antibiotic variamycin and its peracetyl derivative by 1H-and 13C-NMR spectroscopy are reported. Structures of carbohydrate chains of the antibiotics molecule are revised. Variamycin is shown to be 2-[beta-cymmarosyl(1-3)-beta-oliosyl (1-3)-beta-olivosyl]-6-[beta-olivosyl (1-3)-beta-olivosyl] chromomycinone.     

Use of the antibiotic, olivomycin, for the cytochemical study of chromatin]

The possibility to use the antibiotic olivomycin for fluorescence cytochemistry of chromatin properties has been shown. It is found that the binding of olivomycin to nuclei reveals the functional state of chromatin and changes in the course of its activation. The essential condition for the application of the method described is the use of ethanol-aceton fixative. When other fixatives are used, in particular 70% ethanol, olivomycin binding reflects differences in nuclear DNA amount, rather than those in chromatin properties. The advantages of the method described, in comparison with the commonly used technique, are associated with the high affinity of olivomycin to DNA, absence of olivomycin binding with RNA, simplicity of the staining procedures , and with rather a high stability of complexes formed between olivomycin and DNA.     

Cytogenetic effect of the antineoplastic anthracycline antibiotic 4'-epidoxorubicin

Cytogenetic action of 4'-epidoxorubicin (farmorubicin), an antitumor antibiotic was studied with using rat bone marrow cells. It was shown that after intraperitoneal administration the antibiotic increased the number of the aberrant metaphases when the dose was not lower than that equivalent to 1/30 of the LD50. The number of the aberrant metaphases increased with increasing of the antibiotic dose. The maximum number of the cells with impaired chromosomal apparatus was observed 6 hours after the antibiotic administration. In 72 hours it decreased to the level of spontaneous mutations in myelocariocytes. Cytogenetic activity of 4'-epidoxorubicin was comparable to that of doxorubicin (adriablastin) widely used in medical practice.     

Results of the clinical study of the antineoplastic antibiotic bleomycetin

Bleomycetin was applied to the treatment of 68 patients with common forms of malignant tumors. The objective therapeutic effect was observed in 21 patients (31 per cent). The frequency of the favourable therapeutic effects was the most significant in the group of patients with generalized forms of lymphogranulomatosis: objective remissions for 1 to 4 months and stabilization of the tumor process were attained in 12 (41 per cent) and 8 out of 29 patients, respectively, in 9 patients (31 per cent) treated with bleomycetin progression of the underlying disease was recorded. A less pronounced therapeutic effect (33 per cent of the remissions) was recorded in the patients with nonlymphogranulomatous lymphomas. The use of bleomycetin in 48 out of 68 patients was complicated by certain adverse reactions. Intravenous infusions of bleomycetin in a dose of 10-15 mg twice a week (the total dose up to 125 mg) may be recommended as the initial therapeutic regimen in the oncological practice. The trials have showed that bleomycetin made in the USSR has a sufficiently pronounced activity against lymphogranulomatosis and nonlymphogranulomatous lymphomas. In this respect it is not inferior to the bleomycin analog made in Japan.     

Thermodynamics and kinetics of the interaction of copper (II) ions with native DNA.

Based on equilibrium binding studies, as well as on kinetic investigations, two types of interactions of Cu²⁺ ions with native DNA at low ionic strength could be characterized, namely, a nondenaturing and a denaturing complex formation. During a fast nondenaturing complex formation at low relative ligand concentrations and at low temperatures, different binding sites at the DNA bases become occupied by the metal ions. This type of interaction includes chelate formation of Cu²⁺ ions with atoms N₍₇₎ of purine bases and the oxygens of the corresponding phosphate groups, chelation between atoms N₍₇₎ and O of C₍₆₎ of the guanine bases, as well as the formation of specific intestrand crosslink complexes at adjacent G°C pairs of the sequence dGpC. CD spectra of the resulting nondenatured complex (DNA–Cu²⁺)_nat may be interpreted in terms of a conformational change of DNA from the B-form to a C-like form on ligand binding. A slow cooperative denaturing complex formation occurs at increased copper concentrations and/or at increased temperatures. The uv absorption and CD spectra of the resulting complex, (DNA–Cu²⁺)_denat, indicate DNA denaturation during this type of interaction. Such a conclusion is confirmed by microcalorimetric measurements, which show that the reaction consumes nearly the same amount of heat as acid denaturation of DNA. From these and the kinetic results, the following mechanism for the denaturing action of the ligands is suggested: binding of Cu²⁺ ions to atoms N₍₃₎ of the cytosine bases takes place when the cytosines come to the outside of the double helix as a result of statistical fluctuations. After the completion of the binding process, the bases cannot return to their initial positions, and thus local denaturation at the G·C pairs is brought about. The probability of the necessary fluctuations occurring is increased by chelation of Cu²⁺ ions between atoms N₍₇₎ and O of C₍₆₎ of the guanine bases during nondenaturing complex formation, which loosens one of the hydrogen bonds within the G·C pairs, as well as by raising the temperature. The implications of the new binding model, which comprises both the sequence-specific interstand crosslinks and the described mechanism of denaturing complex formation, are discussed and some predictions are made. The model is also used to explain the different renaturation properties of the denatured complexes of Cu²⁺, Cd²⁺, and Zn²⁺ ions with DNA. In temperature-jump experiments with the nondenatured complex (DNA–Cu²⁺)_nat, a specific kinetic effect is observed, namely, the appearance of a lag in the response to the perturbation. The resulting sigmoidal shape of the kinetic curves is considered to be a consequence of the necessity of disrupting a certain number of the crosslinks existing in the nondenatured complex before the local unwinding of the binding regions (a main step of denaturing complex formation) may proceed.