Daunorubicin and doxorubicin, anthracycline antibiotics, a physicochemical and biological review.

The interaction specificity of salmon sperm DNA with various derivatives of daunorubicin has been studied. The results of binding, viscometric, 1H nuclear magnetic resonance (NMR), flow dichroism, DNA template inhibition, rates of dissociation, and circular dichroism studies are found to be consistent with an intercalation mode of binding of the anthracycline ring as has been shown by other investigators. Moreover, it is observed that (i) strength of binding, (ii) the ease of dissociation of DNA-anthracycline complexes, and (iii) the degree of inhibition of the DNA-dependent RNA polymerase are dependent on the presence of the amino sugar moiety of daunoseamine. The results are consistent with specific H bonding of the amino group of the sugar moiety with DNA as has been suggested earlier by Pigram et al. (Pigram, W.J., Fuller, W., and Hamilton, L.D. (1972), Nature (London), New Biol. 235, 17). Peptide derivatives substituted at the amino sugar function of daunorubicin lower the affinity of the drug to DNA and presumably interfere with the "full insertion" of the anthracycline drugs between base pairs of DNA. The significance of these findings in relation to the biological efficacy of daunorubicin and related derivatives as antileukemic agents is discussed.

Interaction specificity of the anthracyclines with deoxyribonucleic acid.

A family of compounds which appear to bind reversibly to double stranded DNA without intercalation between DNA base pairs has been defined. Methods are described by which this non-intercalative binding can be characterised using ultraviolet spectrometry, fluorimetry with ethidium as a probe, viscometry and other hydrodynamic techniques, circular dichroism and nuclear magnetic resonance spectrometry. Antibiotics which fall into this family include the antibiotics distamycin A, netropsin, mithramycin, chromomycin and olivomycin. Synthetic antitumour agents include diarylamidines such as berenil, phthalanilides, aromatic bisguanylhydrazones and bisquaternary ammonium heterocycles. A survey has been made of the general requirements of this family of compounds for DNA binding and biological activity. Binding of drugs to the minor groove of the DNA double helix appears to be the most likely mechanism for the antitumour action of these compounds.

Nonintercalative DNA-binding antitumour compounds.

Publisher Summary This chapter focuses on drugs that interact via various types of non-bonded forces. Many of these have been the subject of intensive and increasing study over the past few decades for two principal reasons; firstly, they have proved to be powerful probes of nucleic acid structure and function, and secondly, a number of them have clinically useful chemotherapeutic properties, of which anti-cancer activity is most prominent. The social and economic impetus for developing effective agents with this property in particular has without doubt been a dominant factor in both funding research in this area and influencing its course of direction. The drugs considered in this chapter exhibit a wide spectrum of biological activity, ranging from the bacteriostatic properties of the acridines such as proflavine and the trypanocidal properties of ethidium bromide to the anti-leukemic action of daunomycin.

The molecular basis for the action of some DNA-binding drugs.

The interaction of native calf thymus DNA with clodinafop-propargyl (CP), in 10 mM HEPES aqueous solutions at neutral pH 7.2, has been investigated by spectrophotometric, circular dichroism (CD), spectrofluorometric, melting temperature (Tm), and viscosimetric techniques. It was found that CP molecules could intercalate between base pairs of DNA as evidenced by hyperchromism in UV absorption band of DNA, an increase in melting temperature, a sharp increase in specific viscosity of DNA, induced CD spectral changes, and increase in the fluorescence of methylene blue (MB)-DNA solutions in the presence of increasing amounts of CP, which indicates that it is able to release the intercalated MB completely. All results suggest that the CP interacts with calf thymus DNA by an intercalative mode of binding.

In vitro study of DNA interaction with clodinafop-propargyl herbicide.

The circular dichroism spectra of complexes of the antibiotics daunomycin, nogalamycin, chromomycin, and mithramycin with calf thymus DNA have been measured over a range of drug/DNA ratios. The similarity of the CD spectra of bound chromomycin and mithramycin suggests that they have very similar binding sites, which produce strong effects on the CD spectra of the bound drugs, and remove the differences arising from local stereochemistry in the free drugs. It was found that it was not possible to predict whether the antibiotics intercalated, from studies of the CD spectra alone, even when comparisons were made with the CD spectra of aminoacridine–DNA complexes with intercalating or nonintercalating ligands.

D. G. Dalgleish

Papers

Circular dichroism studies of complexes of the antibiotics daunomycin, nogalamycin, chromomycin, and mithramycin with DNA