Biomedical subjects

L P Wakelin

Publications and source records attributed to L P Wakelin.

At least 19 recordsLinked to original sources

PubMed1992

cis-bis(pyridine)platinum(II) organoamides with unexpected growth inhibition properties and antitumor activity.

The platinum(II) organoamides [Pt(NRCH2)2L2] (L = pyridine (py), R = p-HC6F4, C6F5,p-IC6F4,p-CIC6F4,p-C6F5C6F4; L = 4-methylpyridine, R = p-HC6F4) and [Pt(NRCH2CH2NR')(py)2] (R = p-HC6F4, R' = C6F5, p-BrC6F4, or p-MeC6F4) inhibit the growth of murine L1210 leukemia cells in culture with ID50 values for continuous exposure in the range 0.6-2.7 microM. Representative complexes are also active against L1210 cells in 2-h pulse exposures, as well as against the cisplatin-resistant variant L1210/DDP and human colonic carcinoma cell lines HT 29 and BE. Three complexes [Pt(NRCH2)2L2] (R = p-HC6F4, C6F5, or p-IC6F4) have good activity (T/C greater than or equal to 180%) against P388 leukemia in mice, and all other compounds tested are active except when R = p-C6F5C6F4, L = py. Although the molecular basis of the biological activity of these complexes is not known, the observation of good activity for amineplatinum(II) compounds with no hydrogen substituents on the nitrogen donor atoms introduces a new factor in the anticancer behavior of platinum(II) complexes.

Animals↗

PubMed1992

DNA-directed alkylating agents. 5. Acridinecarboxamide derivatives of (1,2-diaminoethane)dichloroplatinum(II).

A series of acridine-2- and -4-carboxamide-linked analogues of PtenCl2 has been prepared and evaluated for biological activity against several tumor cell lines in vitro and in vivo. The platinum complexes were generally more cytotoxic than the corresponding ligands against wild-type P388 leukemia cells in vitro, with acridine-4-carboxamide complexes being the more effective. In contrast to cisplatin and PtenCl2, the complexes were equally active in vitro against both wild-type and cisplatin-resistant P388 lines. The 4-carboxamide complexes showed high levels of in vivo activity (ILS greater than 100%) against wild-type P388 using a single-dose protocol, and one compound was also significantly active in vivo in a cisplatin-resistant line, against which cisplatin and PtenCl2 are inactive.

Acridines↗

PubMed1992

Sequence specificity of the binding of 9-aminoacridine- and amsacrine-4-carboxamides to DNA studied by DNase I footprinting.

DNase I footprinting has been used to probe the sequence selectivity of binding of a series of intercalating amsacrine-4-carboxamides and a related 9-aminoacridine-4-carboxamide to three DNA restriction fragments. These ligands have good experimental antileukemic activity, and for those members of the series that gave evaluable footprints, our principal finding is that they bind preferentially to GC-rich regions in agreement with the conclusion of equilibrium and kinetic measurements. The highest affinity sites generally occur in clusters of GC base pairs with runs of AT pairs being excluded from binding. It is important to appreciate that the 9-aminoacridine- and amsacrine-4-carboxamides exhibit a very high degree of selectivity for GC sites which, to our knowledge, has not been previously matched by acridine derivatives in footprinting experiments. The principal determinant of specificity appears to be the 4-carboxamide group itself since neither variations in the terminal funtionality of the 4-carboxamide sidechain nor the presence of the 9-anilino substituent modifies sequence preferences. The molecular origins of selectivity may be discerned in terms of potential hydrogen bonding interactions between the 4-carboxamide moiety and carbonyl oxygen and amino groups of GC base pairs in the DNA minor groove at CG dinucleotide sites. The related therapeutic agent amsacrine failed to inhibit cleavage by DNase I, so no conclusion can be drawn concerning its binding selectivity, save to note that amsacrine does not possess the 4-carboxamide group which appears to be the crucial determinant of GC specificity. Whether selectivity for binding to GC-rich sequences is an important element in the antitumor activity of both the 9-aminoacridine- and amsacrine-4-carboxamides remains to be determined.

Aminacrine↗

PubMed1992

Synthesis, DNA binding interactions and biological activity of bis platinum (II) complexes of N,N,N',N'-tetrakis(2-aminoethyl)diamines.

A series of dimers of the monofunctional platinum species [Pt(dien)Cl]+, linked by a variety of flexible (polymethylene) and more rigid chains, was prepared and evaluated for DNA interactions and cytotoxic activity. The polymethylene-linked dimers were prepared by acylation of N(1),N(3)-bistrityldiethylenetriamine with alpha, omega-dicarboxylic acid chlorides, followed by reduction with diborane. Platination of these ligands was achieved with K2PtI4 prepared in situ, followed by anion exchange. Solutions of the bis(Pt(dien)Cl)2+ complexes were stable, and shown to be pure by 195Pt NMR, but solid products could not be isolated. All of the bis(Pt(dien)Cl)2+ complexes unwound closed circular supercoiled DNA more efficiently than the monomer, and were more efficient than the difunctional platinum complex cisplatin at cross-linking linearized plasmid DNA, as measured on non-denaturing agarose gels. None of the bis(Pt(dien)Cl)2+ complexes were as cytotoxic as cisplatin in both the wild-type and platinum-resistant P388 murine leukaemia cell lines. The more rigid analogues were equitoxic in both sensitive and cisplatin-resistant cells, but none showed in vitro activity against the P388 tumour.

Cell Line↗

PubMed1991

Anthracycline antibiotic arugomycin binds in both grooves of the DNA helix simultaneously: an NMR and molecular modelling study.

Perturbations to the 1H and 31P chemical shifts of DNA resonances together with twenty-four intermolecular nuclear Overhauser effects show that the anthracycline antibiotic arugomycin intercalates between the basepairs of the hexamer duplex d(5'-GCATGC)2 at the 5'-CpA and 5'-TpG binding sites. In the complex two drug molecules are bound per duplex with full retention of the dyad symmetry. Arugomycin adopts a threaded binding orientation with chains of sugars positioned in both the major and minor groove of the helix simultaneously. The complex is stabilized by hydrogen bonding, electrostatic and van der Waals interactions principally in the major groove and involving substituents on the rigidly oriented bicycloamino-glucose sugar of the antibiotic. A specific hydrogen bond is identified between the C2'-hydroxyl and the guanine N7 at the intercalation site. Together, interactions in the major groove appear to account for the intercalation specificity of arugomycin that requires both a guanine and thymine at the intercalation site. We are unable to identify any sequence specific interactions between the minor groove and the arugarose sugar (S1) which binds only weakly, through van der Walls contacts, over the d(GCA).d(TGC) trinucleotide sequence. The data indicate that the sugar chains of arugomycin are flexible and play little part in the interaction of the antibiotic with DNA. The intensity of sequential internucleotide NOEs identifies the intercalation site as being assymmetric. A family of conformers computed using restrained energy minimisation and molecular dynamics indicate that basepair buckling is a feature of the anthracycline intercalation site that may serve to maximise intermolecular van der Waals interactions by wrapping the basepairs around the antibiotic chromophore.

Anthracyclines↗

PubMed1991

DNA-binding properties and antitumour activity of monofunctional alkylating groups attached to the DNA-intercalating chromophore phenanthridine: n-bromoalkylphenanthridinium bromides.

We have synthesised an homologous series of n-bromoalkylphenanthridinium bromides and studied their DNA-binding and antitumour properties. Each of these compounds has the capacity both to intercalate and alkylate DNA. Dialysis measurements reveal a relatively high affinity for calf thymus DNA, being about 10(5) M-1 at ionic strength 0.01. Incubating calf thymus DNA-ligand complexes having a ligand-to-basepair ratio of 0.4 at 37 degrees C for 18 h leads to maximum alkylation levels of about one ligand molecule bound irreversibly per 40 basepairs. The reactivity of these compounds towards DNA is chain-length dependent, the n-decyl compound, for example, requiring about 10-times the ligand-to-basepair input ratio of the n-hexyl derivative to reach the same level of alkylation. The limited degree of alkylation is a consequence of conversion of the alkylbromides to the less reactive alkylchlorides in the buffer medium. The results of DNA sequencing experiments indicate that the n-hexyl derivative alkylates at guanines occurring in 5'-GT-3' sequences and in runs of guanines [(Gp)n]. The corresponding n-decyl compound, on the other hand, is highly selective for guanines in 5'-GT-3' sequences only and also reacts weakly with some adenines. None of the phenanthridinium compounds showed significant antitumour activity in the P388 murine leukaemia test system.

Alkylating Agents↗

PubMed1991

Synthesis and evaluation of DNA-targeted spatially separated bis(aniline mustards) as potential alkylating agents with enhanced DNA cross-linking capability.

DNA-targeted separated bis-mustards were synthesized by attaching aniline mono-mustards at the 4- and 9-positions of the DNA-intercalating ligand 9-aminoacridine-4-carboxamide, with the intention of improving the low cross-link to monoadduct ratio found with most alkylating agents. The geometry of these compounds requires that, when the acridine binds to DNA by intercalation, one alkylating moiety is delivered to each DNA groove. Gel electrophoretic studies show that only one arm of these compounds (probably that attached to the 9-position) alkylates DNA, such alkylation occurring specifically in the major groove at the N7 of guanines. Cell-line studies confirm that the mode of cytotoxicity of these compounds (unlike that of untargeted aniline bis-mustards of comparable reactivity) is due to bulky DNA monoadduct formation. It is concluded that more information is required about the exact orientation of the initial monoadducts before ligands with specific DNA cross-linking ability can be designed.

Alkylating Agents↗

PubMed1991

Synthesis and anti-tumour activity of the spatially-separated mustard bis-N,N'-[3-(N-(2-chloroethyl)-N-ethyl)amino-5-[N,N-dimethylamino)methy l)-aminophenyl]-1,4-benzenedicarboxamide, which alkylates DNA exclusively at adenines in the minor groove.

The mustard derivative, bis-N,N'-[3-(N-(2-chloroethyl)-N-ethyl)amino-5- [N,N-dimethylamino)methyl)aminophenyl]-1,4-benzenedicarboxamide has been synthesized from 3-acetamido-5-nitrobenzoic acid in a 6-step procedure. This compound alkylates exclusively in the minor groove of DNA, at the N3 site of adenines occurring in sequences of runs of adenines and (to a small extent) at 5'-TA and 5'-AT sites. Gel electrophoresis studies and in vitro cytotoxicity assays against repair-deficient AA8 mutant cell lines show it has a high degree of DNA interstrand cross-linking ability.

Alkylating Agents↗

PubMed1990

DNA-directed alkylating ligands as potential antitumor agents: sequence specificity of alkylation by intercalating aniline mustards.

The sequence preferences for alkylation of a series of novel parasubstituted aniline mustards linked to the DNA-intercalating chromophore 9-aminoacridine by an alkyl chain of variable length were studied by using procedures analogous to Maxam-Gilbert reactions. The compounds alkylate DNA at both guanine and adenine sites. For mustards linked to the acridine by a short alkyl chain through a para O- or S-link group, 5'-GT sequences are the most preferred sites at which N7-guanine alkylation occurs. For analogues with longer chain lengths, the preference of 5'-GT sequences diminishes in favor of N7-adenine alkylation at the complementary 5'-AC sequence. Magnesium ions are shown to selectively inhibit alkylation at the N7 of adenine (in the major groove) by these compounds but not the alkylation at the N3 of adenine (in the minor groove) by the antitumor antibiotic CC-1065. Effects of chromophore variation were also studied by using aniline mustards linked to quinazoline and sterically hindered tert-butyl-9-aminoacridine chromophores. The results demonstrate that in this series of DNA-directed mustards the noncovalent interactions of the carrier chromophores with DNA significantly modify the sequence selectivity of alkylation by the mustard. Relationships between the DNA alkylation patterns of these compounds and their biological activities are discussed.

Alkylating Agents↗

PubMed1990

Conformation and dynamics of the deoxyribose rings of a (nogalamycin)2-d (5'-GCATGC)2 complex studied in solution by 1H-n.m.r. spectroscopy.

The conformation and dynamics of the deoxyribose rings of a (nogalamycin)2-d(5'-GCATGC)2 complex have been determined from an analysis of 1H-1H vicinal coupling constants and sums of coupling constants (J1'-2',J1'-2",epsilon 1', epsilon 2' and epsilon 2") measured from one-dimensional n.m.r. spectra and from H-1'-H-2' and H-1'-H-2" cross-peaks in high-resolution phase-sensitive two-dimensional correlation spectroscopy (COSY) and double-quantum-filtered correlation spectroscopy (DQF-COSY) experiments. The value of J3'-4' has also been estimated from the magnitude of H-3'-H-4' cross-peaks in DQF-COSY spectra and H-1'-H-4' coherence transfer cross-peaks in two-dimensional homonuclear Hartman-Hahn spectroscopy (HOHAHA) spectra. The data were analysed, in terms of a dynamic equilibrium between North (C-3'-endo) and South (C-2'-endo) conformers, by using the graphical-analysis methods described by Rinkel & Altona [(1987) J. Biomol. Struct. Dyn. 4,621-649]. The data reveal that the sugars of the 2C-5G and 3A-4T base-pairs, which form the drug-intercalation site, have strikingly different properties. The deoxyribose rings of the 2C-5G base-pair are best described in terms of an equilibrium heavily weighted in favour of the C-2'-endo geometry (greater than 95% 'S'), with a phase angle, P, lying in the range 170-175 degrees and amplitude of pucker between 35 and 40 degrees, as typically found for B-DNA. For the deoxyribose rings of the 3A-4T base-pair, however, the analysis shows that, for 3A, the C-2'-endo and C3'-endo conformers are equally populated, whereas a more limited data set for the 4T nucleotide restricts the equilibrium to within 65-75% C-2'-endo. The deoxyribose rings of the 1G-6C base-pair have populations of 70-80% C-2'-endo, typical of nucleotides at the ends of a duplex. Although drug-base-pair stacking interactions are an important determinant of the enhanced duplex stability of the complex [Searle, Hall, Denny, & Wakelin (1988) Biochemistry 27, 4340-4349], the current findings make it clear that the same interactions can be associated with considerable variations in the degree of local structural dynamics at the level of the sugar puckers.

Base Sequence↗

PubMed1990

Sequence specific conformation of a DNA decamer containing an adenine tract studied in solution by H-NMR spectroscopy.

The decanucleotide duplex d(AAAACGTTTT)2 and a variety of phase-sensitive two-dimensional (2D) NMR experiments have been used to investigate the solution conformation of an adenine-tract and its junction with another DNA sequence. 2D nuclear Overhauser effect data confirm that the oligonucleotide has a general B-type DNA morphology but an array of unusual correlations implies that the adenine tract and the 5'-ApC junction have conformations more compatible with the modified X-ray structures recently reported for DNAs of similar sequence (Nelson, H.C.M., Finch, J.T., Luisi, B.F. and Klug, A. (1987) Nature 330, 221-226). The pattern and magnitude of interstrand NOEs from the adenine H2s to the sugar H1's of the complementary base to the 5'-neighbouring residue indicate that the A-T basepairs are highly propeller twisted and that the minor groove is narrowed, showing its greatest compression at the 3'-end of the tract at the 5'-ApC step. Quantifying spin-coupling interactions within the deoxyribose rings by analysing both 1D and high-resolution 2D DQF-COSY data reveals that the conformation of the purines is predominantly C2'-endo, with the pseudorotation phase angle P lying in the range 140-180 degrees. For the pyrimidines, however, there are distortions away from this standard B-type geometry with the data being best described by P values lying in the range 90-130 degrees (i.e., O4'-endo, C1'-exo). The sugar puckers of A1, T9 and T10 are dynamically distorted no doubt as a consequence of their positions at, or close to, the ends of the duplex. Thus the conformation of the adenine and thymine sugars within the oligo(dA) and oligo(dT) strands are different with an abrupt change in sugar puckering occurring at the 5'-ApC (5'-GpT) step. Peculiar chemical shifts values for A4H2, T7CH3 and sugar C5 H1', H2' and H2", together with a number of interresidue NOEs with unusual intensities, imply that there are also substantial modifications to basepair stacking interactions at this step. Taken as a whole, our data are consistent with the view that the conformational dislocation at the 5'-ApC dinucleotide results from a combination of slide and roll manoeuvres and that the junction between the AAAA and CG sequences is a potential nucleation site for DNA bending.

Adenine↗

PubMed1990

The interaction of substituted and rigidly linked diquinolines with DNA.

Viscometric measurements with circular and sonicated rodlike DNA fragments were used to explore whether ring substituents or conformationally restricted linkers promote bifunctional intercalation amongst a series of binuclear 4-aminoquinolines bridged via their 4-amino group. We find that ligands comprising unsubstituted quinolines and piperazine or pyrazole linkages bisintercalate. Quinoline-substituted alkyl-linked dimers intercalate in either a mixed monofunctional-bifunctional mode or bind with only one of their chromophores intercalated depending on the nature of the substituents. Equilibrium dialysis measurements show that the binding affinity for calf thymus DNA of the compounds studied ranges from (1.2-12) . 10(4) M-1 in buffer of ionic strength 0.1. Both co-operative and antico-operative binding isotherms were obtained and there is evidence for a second binding mode for the piperazine-linked diquinoline at saturating binding levels. For this compound the high-affinity association constant decreases with increasing ionic strength, 3.4 cations being released per bound ligand molecule. Partition dialysis measurements with DNAs of differing base composition indicate that the compounds studied are either AT selective or sequence neutral depending on ligand structure. For example, the pyrazole linker imparts a marked specificity for binding to AT-rich DNA, whereas the piperazine linker does not. Kinetic measurements using the surfactant-sequestration method reveal that DNA-diquinoline complexes dissociate very rapidly by complex mechanisms with rate constants greater than 100 s-1 in buffer of ionic strength 0.1.

Chemical Phenomena↗

PubMed1990

Differences in sequence selectivity of DNA alkylation by isomeric intercalating aniline mustards.

Two DNA-targeted mustard derivatives, N,N-bis(2-chloroethyl)-4-(5-[9-acridinylamino]-pentamido)aniline and 4-(9-[acridinylamino]butyl 4-(N,N-bis[2-chloroethyl]-aminobenzamide, which are isomeric compounds where the mustard is linked to the DNA-binding 9-aminoacridine moiety by either a -CONH- or a -NHCO- group, show significant differences in the sequence selectivity of their alkylation of DNA. The CONH isomer is a more efficient alxylating agent than the NHCO compound by an order of magnitude, consistent with the larger electron release of the CONH group to the aniline ring. However, the pattern of alkylation by the two compounds is also very different, with the CONH isomer preferring alkylation of guanines adjacent to 3'- or 5'-adenines and cytosines (for example those in sequences 5'-CGC, 5'-AGC, 5'-CGG and 5'-AGA) while the isomeric NHCO compound shows preference for guanines in runs of Gs. In addition, both isomers alkylate 3'-adenines in runs of adenines. Both compounds also show completely different patterns of alkylation to their untargeted mustard counterparts, since 4-MeCONH-aniline mustard alkylates all guanines and adenines in runs of adenines, while 4-Me2NCO-aniline mustard fails to alkylate DNA at all. These differences in alkylation patterns between the CONH- and its isomeric NHCO- compounds and their relationships between the alkylation patterns of the isomers and their biological activities are discussed.

Alkylation↗

PubMed1990

DNA-directed alkylating agents. 1. Structure-activity relationships for acridine-linked aniline mustards: consequences of varying the reactivity of the mustard.

A series of DNA-targeted aniline mustards have been prepared, and their chemical reactivity and in vitro and in vivo cytotoxicity have been evaluated and compared with that of the corresponding simple aniline mustards. The alkylating groups were anchored to the DNA-intercalating 9-aminoacridine chromophore by an alkyl chain of fixed length attached at the mustard 4-position through a link group X, while the corresponding simple mustards possessed an electronically identical small group at this position. The link group was varied to provide a series of compounds of similar geometry but widely differing mustard reactivity. Variation in biological activity should then largely be a consequence of this varying reactivity. Rates of mustard hydrolysis in the two series related only to the electronic properties of the link group, with attachment of the intercalating chromophore having no effect. The cytotoxicities of the simple mustards correlated well with group electronic properties (with a 200-300-fold range in IC50S). The corresponding DNA-targeted mustards were much more potent (up to 100-fold), but their IC50 values varied much less with linker group electronic properties. Most of the DNA-targeted mustards showed in vivo antitumor activity, being both more active and more dose-potent than either the corresponding untargeted mustards and chlorambucil. These results show that targeting alkylating agents to DNA by attachment to DNA-affinic units may be a useful strategy.

Alkylating Agents↗

PubMed1990

Kinetic and equilibrium binding studies of amsacrine-4-carboxamides: a class of asymmetrical DNA-intercalating agents which bind by threading through the DNA helix.

Detailed equilibrium and kinetic studies of the DNA interaction of the amsacrine-4-carboxamide class of compounds suggest that they bind by intercalating the acridine chromophore at near-maximal overlap with the base pairs, locating their two dissimilar side chains in specific grooves of the double helix. The first step is a fast bimolecular association to form an outside-bound complex (probably in the major groove). Insertion of the less bulky carboxamide side chain then occurs in a process governed largely by the rate of transient opening of the double helix by natural "breathing" motions and is followed by further monomolecular rearrangements to allow the carboxamide side chain to find its highest affinity binding sites in the minor groove. Dissociation of the complexes are much more ligand structure dependent, but also involve opening of the double helix to allow disengagement. Compounds of this type, which locate their two distinguishable side chains one in each DNA groove, form a unique class of DNA-binding ligand, with considerable potential for regiospecific delivery of reactive functionality to DNA. Although natural products which also have such specific binding modes are known (e.g. nogalamycin), the amsacrine-4-carboxamides discussed here are the first class of readily modified synthetic compounds with this property.

Amides↗

PubMed1990

DNA-directed alkylating agents. 2. Synthesis and biological activity of platinum complexes linked to 9-anilinoacridine.

Two different classes of cis-diaminedichloroplatinum(II) complexes linked to the DNA-intercalating chromophore 9-anilinoacridine have been synthesized and evaluated as DNA-targeted antitumor agents. Two different Pt chelating ligands were investigated (based on 1,2-ethanediamine and 1,3-propanediamine), designed to deliver the Pt in an orientation likely to respectively enhance either intrastrand or interstrand cross-linking. Although both sets of ligands were somewhat unstable under neutral or basic conditions with respect to disproportionation, the corresponding Pt complexes, once prepared, appeared to be quite stable. All the Pt complexes were monitored for purity by TLC, HPLC, and FAB mass spectra, and the mode of Pt coordination was established by 195Pt NMR spectroscopy. The complexes appeared to cause simultaneous platination and intercalative unwinding of plasmid DNA. In vitro studies were carried out with both wild-type and cisplatin-resistant P388 cell lines. Whereas cisplatin itself and the ethylenediamine and 1,3-propanediamine complexes used as standards were about 10-fold less active against the resistant line, the ethylenediamine-linked Pt complexes showed no differential toxicity between the two lines and the propanediamine-linked complexes showed significant differentials (up to 8-fold) in favor of the cisplatin-resistant line. However, these were no greater than those shown by the unplatinated ligands themselves. The majority of the acridine complexes were inactive in vivo against the wild-type P388 leukemia. They were very insoluble, and although a suitable formulation was found, this may have been a factor. It is also possible that these compounds bind in such a way as to direct the Pt away from the major groove.

Alkylating Agents↗

PubMed1990

DNA-directed alkylating agents. 3. Structure-activity relationships for acridine-linked aniline mustards: consequences of varying the length of the linker chain.

Four series of acridine-linked aniline mustards have been prepared and evaluated for in vitro cytotoxicity, in vivo antitumor activity, and DNA cross-linking ability. The anilines were attached to the DNA-intercalating acridine chromophores by link groups (-O-, -CH2-, -S-, and -SO2-) of widely varying electronic properties, providing four series of widely differing mustard reactivity where the alkyl chain linking the acridine and mustard moieties was varied from two to five carbons. Relationships were sought between chain length and biological properties. Within each series, increasing the chain length did not alter the reactivity of the alkylating moiety but did appear to position it differently on the DNA, since cross-linking ability (measured by agarose gel assay) altered with chain length, being maximal with the C4 analogue. The in vivo antitumor activities of the compounds depended to some extent on the reactivity of the mustard, with the least reactive SO2 compounds being inactive. However, DNA-targeting did appear to allow the use of less reactive mustards, since the S-linked acridine mustards showed significant activity whereas the parent S-mustard did not. Within each active series, the most active compound was the C4 homologue, suggesting some relationship between activity and extent of DNA alkylation.

Acridines↗

PubMed1990

Kinetics of the binding of mitoxantrone, ametantrone and analogues to DNA: relationship with binding mode and anti-tumour activity.

The kinetics of association and dissociation of DNA complexes of the anti-tumour agents mitoxantrone, ametantrone and related 1,4-bis(alkylamino)anthraquinones have been determined by stopped-flow spectrophotometry, in order to study relationships between structure, kinetic parameters and biological activity. Variations in the structure of the side chains of ametantrone analogues had little effect on the kinetic stability of the complexes, but the mitoxantrone complexes dissociated about an order of magnitude more slowly, suggesting an important role for the two hydroxyl groups on the chromophore of the latter compound. The results are consistent with other n.m.r. and molecular mechanics data, which suggest a binding model where the chromophore intercalates perpendicularly to the DNA base pair axis. Dissociation studies with DNA homopolymers of varying base composition suggest the kinetic mechanism is a mixed parallel/sequential one, with the slowest dissociation processes being from GC-rich sites in both homopolymers and natural DNA. The results suggest guidelines for the design of more tumour-active analogues of the class.

Animals↗