Unanticipated differences between alpha- and gamma-diaminobutyric acid-linked hairpin polyamide-alkylator conjugates

Hairpin polyamide-chlorambucil conjugates containing an alpha-diaminobutyric acid (alpha-DABA) turn moiety are compared to their constitutional isomers containing the well-characterized gamma-DABA turn. Although the DNA-binding properties of unconjugated polyamides are similar, the alpha-DABA conjugates display increased alkylation specificity and decreased rate of reaction. Treatment of a human colon carcinoma cell line with alpha-DABA versus gamma-DABA hairpin conjugates shows only slight differences in toxicities while producing similar effects on cell morphology and G2/M stage cell cycle arrest. However, striking differences in animal toxicity between the two classes are observed. Although mice treated with an alpha-DABA hairpin polyamide do not differ significantly from control mice, the analogous gamma-DABA hairpin is lethal. This dramatic difference from a subtle structural change would not have been predicted.

PNA-nitrogen mustard conjugates are effective suppressors of HER-2/neu and biological tools for recognition of PNA/DNA interactions

Peptide nucleic acids (PNAs) are promising tools for gene regulation. One of the challenges of using PNAs as gene regulators is the need to optimize the efficiency of interaction with critical sequences of DNA. To improve the efficiency of binding between PNAs and the HER-2/neu promoter, mono- and bis-pyrimidine-rich PNAs were conjugated to a nitrogen mustard at either the amino or carboxy terminus. Gel shift analysis demonstrated that conjugation to an alkylating agent slowed PNA binding and favored PNA:DNA:DNA triplex helix formation while preserving a high binding affinity. Sites of DNA alkylation were visualized by piperidine cleavage and showed PNA binding first by Hoogsteen bond formation with the target duplex to form a stable PNA:DNA:DNA triplex structure which is later converted to a PNA:DNA:PNA triple helix by strand invasion and Watson-Crick base pairing by a second PNA molecule. In this way, PNA-directed DNA alkylation was used to deduce the mode of PNA binding. Transient transfection experiments demonstrated that the PNA-nitrogen mustard conjugates suppressed HER-2/neu expression by up to 80%. In comparison with an unmodified mono-PNA or a bis-PNA, these results indicate that the covalent adducts stabilized PNA binding in cells and suggest that the conjugation of PNAs to nitrogen mustards is a robust strategy for developing antigene PNA oligonucleotides to prevent transcription.

Structure???anti-leukemic activity relationship study of B- and D-ring modified and non-modified steroidal esters of chlorambucil

In order to study the role of the steroidal moiety on the expression of anti-leukemic activity, we synthesized six derivatives of chlorambucil (CHL), and tested them on leukemias P388 and L1210 in vivo and in normal human lymphocytes in vitro. Five of the six tested compounds produced submultiple toxicity, while the measured anti-leukemic potency was significantly increased. The lactamization of the B-steroidal ring rendered the molecules more potent, but the corresponding 7-oxidized derivatives proved better in both leukemias tested. The lactamization of the D-steroidal ring afforded potent compounds, regardless of the configuration of the B-ring. The best among all derivatives contains both chemical modifications and is intended as a promising key molecule that must be further studied. We speculate that in leukemic cells a tumor-specific protein is overexpressed, the steroid has the ability to bind and block this protein from carrying out its normal function, and the drug-protein complex prevents the repair of the adducts. The synthesis, physicochemical and spectroscopic data of these compounds and a modified route for the synthesis of CHL are also reported.

Structure???anti-leukemic activity relationship study of B- and D-ring modified and non-modified steroidal esters of chlorambucil??s active metabolite

We have studied the effect of modification of the B-steroidal ring to lactamic on the anti-leukemic potency of D-modified and D-non-modified steroidal esters of chlorambucil's active metabolite. The compounds synthesized were studied against leukemias P388 and L1210 after the subsequent estimation of their toxicity in vivo, and for their ability to induce sister chromatid exchanges (SCEs) and to inhibit cell proliferation in normal human lymphocytes in vitro. The in vitro results correlated well, on a molar basis, with the results obtained from the study of the anti-leukemic potency. In a comparative study, the B-lactamic steroidal derivatives proved less active than the 7-oxidized ones against both leukemias. The presence of the -NHCO- group in the B-steroidal ring did not have the same positive effect on the biological action of chlorambucil's active metabolite esters as in the D-lactamic ring. However, this new modification of the B-ring rendered the final esteric derivatives much more toxic, compared with to the corresponding esters with a simple B-ring. This loss of the anti-leukemic specificity, which occurs from the modification of the B-ring, is additional evidence for the role of the steroidal part on the mechanism of action of these promising compounds. This provides support for the notion that the steroidal part of these molecules is not just a simple biological carrier, as has been speculated for many years.

Aromatic oligopeptides with chlorambucil moiety--synthesis and biological evaluation

New aromatic oligopeptides with chlorambucil moiety have been synthesized. They showed antiproliferative and cytotoxic effect in the standard cell line of the mammalian tumor MCF-7.

Arresting Cancer Proliferation by Small-Molecule Gene Regulation

A small library of pyrrole-imidazole polyamide-DNA alkylator (chlorambucil) conjugates was screened for effects on morphology and growth characteristics of a human colon carcinoma cell line, and a compound was identified that causes cells to arrest in the G2/M stage of the cell cycle. Microarray analysis indicates that the histone H4c gene is significantly downregulated by this polyamide. RT-PCR and Western blotting experiments confirm this result, and siRNA to H4c mRNA yields the same cellular response. Strikingly, reduction of H4 protein by >50% does not lead to widespread changes in global gene expression. Sequence-specific alkylation within the coding region of the H4c gene in cell culture was confirmed by LM-PCR. The compound is active in a wide range of cancer cell lines, and treated cells do not form tumors in nude mice. The compound is also active in vivo, blocking tumor growth in mice, without obvious animal toxicity.

Design and Synthesis of a Nitrogen Mustard Derivative Stabilized by Apo-neocarzinostatin

Neocarzinostatin (NCS) is an antitumor antibiotic comprising a 1:1 protein-chromophore complex and exhibits cytotoxic action through DNA cleavage via H-abstraction. Cytotoxic activity resides with the chromophore 1 alone, while the protein (apoNCS) protects and transports labile 1. The naphthoate portion (2) of NCS chromophore (1) is important for binding to apoNCS and DNA intercalation. In this paper we describe our attempts to use apoNCS to improve the hydrolytic stability of novel bifunctional DNA alkylating agents. The nitrogen mustards, melphalan and chlorambucil, were both conjugated to 2, and the biological activities of these conjugates were assessed. Chlorambucil did not benefit from conjugation. The melphalan conjugate (6) formed covalent DNA adducts at guanine bases and exhibited greater in vitro cytotoxic activity than unmodified melphalan. Fluorescence and NMR spectroscopy showed that 6 binds to apoNCS. Binding to apoNCS-protected 6 reduced the extent of hydrolysis of the conjugate. This novel approach demonstrates for the first time that an enediyne apo-protein can be used to improve the stability of substances that are of potential interest in cancer chemotherapy.

Reactions of N,N-Bis(2-chloroethyl)-p-aminophenylbutyric Acid (Chlorambucil) with 2‘-Deoxycytidine, 2‘-Deoxy-5-methylcytidine, and Thymidine

N,N-Bis(2-chloroethyl)-p-aminophenylbutyric acid (chlorambucil, 1; 2.5 mM) was allowed to react with 2'-deoxycytidine, 2'-deoxy-5-methylcytidine, and thymidine (16.1 mM) at physiological pH (cacodylic acid, 50% base), and the reactions were followed by HPLC and HPLC-MS technique. Although the predominant reaction observed was chlorambucil hydrolysis, 1 reacted with various heteroatoms of the nucleosides. The principal site of alkylation with all pyrimidine nucleosides was N3, as judged by 1H NMR and HPLC-MS analyses. Also, several other adducts were detected, which could be tentatively characterized by means of HPLC-MS and MS/MS. As expected, thymidine was the least reactive pyrimidine nucleoside studied, and in addition of the N3 derivative, it reacted only at the carbohydrate moiety. Overall reactivity of cytosine nucleosides with 1 was considerably higher. The N3 adducts of dCyd and 5-Me-dCyd partially deaminated under the reaction conditions employed, but the reaction was not catalyzed by the participation of the omega-hydroxy function of the alkyl substituent but presumably by the nitrogen atom of the chlorambucil moiety. In the case of cytosine nucleosides, the O2 derivatives were the second most abundant species. 5-Me-dCyd reacted more readily at O2 than dCyd. These O2 adducts were labile under acidic, neutral, and basic conditions. No N4 derivatives or cross-links were detected, but dCyd reacted also at C5, although the yield of this derivative was very low. The role of chlorambucil-pyrimidine 2'-deoxyribonucleoside adducts on the cytotoxicity and mutagenity of 1 is also discussed.

Relationship between activation of microsomal glutathione S-transferase and metabolism behavior of chlorambucil

Chlorambucil (4-[p-[bis [2-chloroethyl] amino] phenyl]-butanoic acid; CMB) is a bifunctional alkylating agent that exhibits acquired drug resistance upon repeated dosing in human. This compound reacts with glutathione (gamma-glutamylcysteinylglycine, GSH) both non-enzymatically and enzymatically in the presence of glutathione S-transferases (GSTs) to produce several GSH conjugates. The formation of GSH conjugates of this class of alkylating agents may play a role in the development of acquired drug resistance. In this study, the effect of CMB on microsomal GST (mGST) activity and the catalytic effect of mGST on the formation of GSH conjugates of CMB were investigated. mGST was activated by CMB in a concentration- and time-dependent manner. NEM failed to reactivate the CMB pretreated mGST. This suggests that mGST could be activated by CMB, possibly via reacting with the single cysteine (Cys49) in mGST. The resulting conjugates of GSH and CMB were characterized by a combination of lipid chromatography/electrospray ionization mass spectrometry (LC/ESI/MS). mGST presented a strong catalytic effect on the reaction as determined by the increase of the diglutathionyl derivative, 4-[p-[bis[2-S-glutathionylethyl] amino]phenyl]-butanoic acid (CMBSG2), monoglutathionyl derivatives, 4-[p-[N-2-chloroethyl, N-2-S-glutathionylethyl] amino]phenyl]-butanoic acid (CMBSG) and 4-[p-[N-2-S-glutathionylethyl, N-2-hydroxyethyl] amino]phenyl]-butanoic acid (CMBSGOH) and the decrease of CMB. mGST which was stimulated approximately 2.5-fold with CMB had a stronger catalytic effect. These results suggest the potential role of the activation of mGST in the CMB inactivation and in the development of acquired drug resistance.

Synthesis of poly(ethylene glycol) with sulfadiazine and chlorambucil end groups and investigation of its antitumor activity

alpha-Amino-omega-hydroxyl-poly(ethylene glycol) (PEG) with different molecular weight (M(r)=2100, 4400, 7200) were synthesized and used as carrier for the combination of sulfadiazine and chlorambucil. In vivo, all these polymer drugs with sulfadiazine and chlorambucil at each end are water soluble and showed the higher antitumor activity against Lewis lung cancer than the same polymers but without the sulfadiazine. The best one is the sample with molecular weight of 2100. In vitro, however, for the samples with same molecular weights, the polymer drugs with and without sulfadiazine showed the similar results against C6 human breast cancer cells. No obvious difference was found.

Structure-activity studies of novel amidine analogues of chlorambucil: correlation of cytotoxic activity with DNA-binding affinity and topoisomerase II inhibition

A series of amidine analogues of chlorambucil (9-12), where 5-[4-(N-alkylamidino)phenyl]-2-furancarboxamide and the chlorambucil moiety are linked by a NH(CH(2))(2)NH chain, was synthesized and their cytotoxicity has been tested against the growth of human breast cancer MCF-7 cells. Evaluation of the cytotoxicity of compounds 9-12 employing a MTT assay and inhibition of [(3)H]thymidine incorporation into DNA demonstrated that these conjugates were more active than chlorambucil. Data from the ethidium displacement assay indicated that these compounds bind in the minor groove of DNA and show moderate specificity for AT base pairs. Compounds 9-12 were potent topoisomerase II inhibitors, with 50% inhibitory concentrations (IC(50))ranging from 10 to 40 microM. The cytotoxicity of the compounds 9-12 correlates with their DNA-binding affinities and their relative potency as topoisomerase II inhibitors. Altogether, these data suggest (i) that the cytotoxic activity of compounds 9-12 may be due to the combined effects of alkylation, DNA-minor groove binding, and (ii) that N-(2-aminoethyl)-5-(4-N-alkylamidinophenyl)-2-furancarboxamides (5-8) ligands are suitable linkers that favors DNA targeting by chlorambucil derivatives.

Enhanced hydrolytic stability and water solubility of an aromatic nitrogen mustard by conjugation with molecular umbrellas

Chlorambucil, an aromatic nitrogen mustard, has been conjugated to putrescine- and spermidine-based scaffolds bearing one, two, and four persulfated cholic acid units. Those conjugates bearing two or four sterols show improved hydrolytic stability and water solubility relative to chlorambucil. A similar conjugate that contained only one sterol unit shows negligible improvement in hydrolytic stability but a significant increase in water solubility. Qualitatively, the hydrolytic stability within this series of conjugates parallels the shielding effects that have previously been found for related conjugates bearing a pendant, hydrophobic fluorescent probe. In vitro studies indicate that these conjugates possess modest to moderate activity against certain human lymphoblastic leukemia and human colon carcinoma cells.

Enabling ScFvs as multi-drug carriers: a dendritic approach

To enable scFvs as multi-drug carriers, we designed and synthesized dendritic linker molecules bearing up to nine chlorambucil residues at the branch ends. A maleimide group was used at the focal point of the dendron for easy linkage to the scFv. Originally designed molecules showed poor water solubility. To address this problem, a lysine residue with an unprotected carboxylic acid group was inserted into the dendron branches. The new molecules showed excellent water solubility and are now suitable for conjugation. Such dendritic molecules will allow studies to understand the relationship between the drug/antibody ratio and the potency of the immunoconjugates. The dendritic approach could also be applied to drugs other than chlorambucil and carriers other than scFvs to greatly increase the drug/carrier ratio.

Reactions of N,N-bis(2-chloroethyl)-p-aminophenylbutyric acid (chlorambucil) with 2'-deoxyadenosine

N,N-bis(2-chloroethyl)-p-aminophenylbutyric acid (chlorambucil, 1; 0.6 mM) was allowed to react with 2'-deoxyadenosine (16.1 mM) at physiological pH (cacodylic acid, 50% base), and the reactions were followed by HPLC-MS and HPLC-MS/MS techniques. Although the predominant reaction observed was chlorambucil hydrolysis, ca. 7% of 1 reacted with various heteroatoms of the nucleoside. The principal site of alkylation was N1. Several other adducts were also detected. The N1, N6, N3, and N7 derivatives were characterized by means of MS/MS, UV, and (1)H NMR. The N6 adduct is derived directly from alkylation of N6 of 2'-dAdo. Dimroth rearrangement of the N1 adduct to the N6 adduct was very slow under the reaction conditions employed. Minor adducts such as a carbohydrate derivative were tentatively characterized by MS/MS. No cross-links were detected. The role of chlorambucil-2'-deoxyadenosine adducts in the cytotoxicity and mutagenicity of 1 is also discussed.

DNA crosslinking and biological activity of a hairpin polyamide-chlorambucil conjugate

A prototype of a novel class of DNA alkylating agents, which combines the DNA crosslinking moiety chlorambucil (Chl) with a sequence-selective hairpin pyrrole-imidazole polyamide ImPy-beta-ImPy-gamma-ImPy-beta-Dp (polyamide 1), was evaluated for its ability to damage DNA and induce biological responses. Polyamide 1-Chl conjugate (1-Chl) alkylates and interstrand crosslinks DNA in cell-free systems. The alkylation occurs predominantly at 5'-AGCTGCA-3' sequence, which represents the polyamide binding site. Conjugate-induced lesions were first detected on DNA treated for 1 h with 0.1 micro M 1-Chl, indicating that the conjugate is at least 100-fold more potent than Chl. Prolonged incubation allowed for DNA damage detection even at 0.01 micro M concentration. Treatment with 1-Chl decreased DNA template activity in simian virus 40 (SV40) in vitro replication assays. 1-Chl inhibited mammalian cell growth, genomic DNA replication and cell cycle progression, and arrested cells in the G2/M phase. Moreover, cellular effects were observed at 1-Chl concentrations similar to those needed for DNA damage in cell-free systems. Neither of the parent compounds, unconjugated Chl or polyamide 1, demonstrated any cellular activity in the same concentration range. The conjugate molecule 1-Chl possesses the sequence-selectivity of a polyamide and the enhanced DNA reactivity of Chl.

Syntheses of dendritic linkers containing chlorambucil residues for the preparation of antibody-multidrug immunoconjugates

A novel dendritic molecule with nine chlorambucil (CBL) residues on the surface and a maleimide moiety at the core terminus was synthesized using a convergent synthetic methodology. This molecule is ready for attachment to single-chain Fv antibodies (scFvs) to form antibody-multidrug immunoconjugates in an effort to study the relevance of drug/antibody molar ratio and the potency of these drug-antibody immunoconjugates. A monomer and a trimer with a similar structural motif were also prepared for comparative purposes.

Metabolism and mechanisms of action of bendamustine: rationales for combination therapies

Bendamustine hydrochloride is the active ingredient of Ribomustin (Ribosepharm GmbH, Munich, Germany). It was first synthesized in 1963 in the German Democratic Republic. Bendamustine is chemically related to the alkylating agent chlorambucil, with the benzene ring in the chlorambucil molecule replaced by a 1-methyl-benzimidazole moiety. The mechanisms of action of bendamustine have been under investigation since the early 1960s, and its first use was as a treatment for multiple myeloma in 1969. Bendamustine has three active moieties: an alkylating group, in common with the nitrogen mustard family; a benzimidazole ring, which may act as a purine analog; and a butyric acid side-chain. Bendamustine undergoes extensive first-pass metabolism. However, unmetabolized bendamustine accounts for about 45% of the total drug recovered in urine. The main transformation product is a cytotoxic hydroxy metabolite (beta-hydroxybendamustine). Bendamustine was originally synthesized with the intention of producing an antineoplastic agent with low toxicity and both alkylating and antimetabolic properties. However, it has been shown that, at least at high concentrations, it acts primarily as an alkylating agent. Based on the multiple actions and cell cycle effects of this agent, mechanism-based combination strategies have been suggested. The rationales behind bendamustine combination regimens and the importance of the sequence of administration of different drugs are explored.

Synthesis and in vitro evaluation of quaternary ammonium derivatives of chlorambucil and melphalan, anticancer drugs designed for the chemotherapy of chondrosarcoma

To enhance affinity for malignant cartilaginous tumors (chondrosarcomas), quaternary ammonium (QA) conjugates of chlorambucil and melphalan were prepared by linking the QA moiety to nitrogen mustards via an amide bond. They exhibited closely similar and sometimes more favorable values than their parent compounds. In the cell lines tested, the two QA conjugates displayed appreciable cytotoxicity, the QA conjugate of chlorambucil even showing an enhanced efficiency against chondrosarcoma compared with chlorambucil.

Sequence-specific DNA cleavage by dipeptides disubstituted with chlorambucil and 2,6-dimethoxyhydroquinone-3-mercaptoacetic acid

Two dipeptides, each containing a lysyl residue, were disubstituted with chlorambucil (CLB) and 2,6-dimethoxyhydroquinone-3-mercaptoacetic acid (DMQ-MA): DMQ-MA-Lys(CLB)-Gly-NH2 (DM-KCG) and DMQ-MA-beta-Ala-Lys(CLB)-NH2 (DM-BKC). These peptide-drug conjugates were designed to investigate sequence-specificity of DNA cleavage directed by the proximity effect of the DNA cleavage chromophore (DMQ-MA) situated close to the alkylating agent (CLB) inside a dipeptide moiety. Agarose electrophoresis studies showed that DM-KCG and DM-BKC possess significant DNA nicking activity toward supercoiled DNA whereas CLB and its dipeptide conjugate Boc-Lys(CLB)-Gly-NH2 display little DNA nicking activity. ESR studies of DMQ-MA and DM-KCG both showed five hyperfine signals centered at g = 2.0052 and are assigned to four radical forms at equilibrium, which may give rise to a semiquinone radical responsible for DNA cleavage. Thermal cleavage studies at 90 degrees C on a 265-mer test DNA fragment showed that besides alkylation and cleavage at G residues, reactions with DM-KCG and DM-BKC show a preference for A residues with the sequence pattern: 5'-G-(A)n-Pur-3' > 5'-Pyr-(A)n-Pyr-3' (where n = 2-4). By contrast, DNA alkylation and cleavage by CLB occurs at most G and A residues with less sequence selectivity than seen with DM-KCG and DM-BKC. Thermal cleavage studies using N7-deazaG and N7-deazaA-substituted DNA showed that strong alkylation and cleavage at A residues by DM-KCG and DM-BKC is usually flanked on the 3' side by a G residue whereas strong cleavage at G residues is flanked by at least one purine residue on either the 5' or 3' side. At 65 degrees C, it is notable that the preferred DNA cleavage by DM-KCG and DM-BKC at A residues is significantly more marked than for G residues in the 265-mer DNA; the strongest sites of A-specific reaction occur within the sequences 5'-Pyr-(A)n-Pyr-3'; 5'-Pur-(A)n-G-3' and 5'-Pyr-(A)n-G-3'. In pG4 DNA, cleavage by DM-KCG and DM-BKC is much greater than that by CLB at room temperature and at 65 degrees C. It was also observed that DM-KCG and DM-BKC cleaved at certain pyrimidine residues: C40, T66, C32, T34, and C36. These cleavages were also sequence selective since the susceptible pyrimidine residues were flanked by two purine residues on both the 5' and 3' sides or by a guanine residue on the 5' side. These findings strongly support the proposal that once the drug molecule is positioned so as to permit alkylation by the CLB moiety, the DMQ-MA moiety is held close to the alkylation site, resulting in markedly enhanced sequence-specific cleavage.

2-[N1-2-pyrimidyl-aminobenzenesulfonamido] ethyl 4-bis(2-chloroethyl) aminophenyl butyrate: a potent antitumor agent

2-[N'-2-Pyrimidyl-aminobenzenesulfonamido] ethyl 4-bis(2-chloroethyl) aminophenyl butyrate has been prepared by reaction of chlorambucil with sulfadiazine derivative. Schiffs base has been used as the protective group of the aromatic amine in the synthesis. It can be completely removed by the irradiation of 365 nm UV light at room temperature. The title compound exhibits a high antitumor activity with a therapeutic index (TI) of 47.55 which is twice that of chlorambucil's (TI: 22.84).

Reactions of N,N-bis(2-chloroethyl)-p-aminophenylbutyric acid (chlorambucil) with 2'-deoxyguanosine

N,N-Bis(2-chloroethyl)-p-aminophenylbutyric acid (chlorambucil, 1) was allowed to react in the presence of 2'-deoxyguanosine (16 mM) at physiological pH (cacodylic acid, 50% base), and the reactions were followed by HPLC/MS/MS techniques. Although the predominant reaction observed was chlorambucil hydrolysis, ca. 24% of 1 reacted with different heteroatoms of the nucleoside. As expected, the principal site of 2'-deoxyguanosine alkylation was N7. Alkylation of N7 caused spontaneous depurination, and N-(7-guaninylethyl)-N-hydroxyethyl-p-aminophenylbutyric acid (5) and the corresponding N7,N7-bis-adduct (6) were the major stable dGuo derivatives. Also several other adducts were detected and tentatively identified by means of MS/MS and UV. From them, the O(6-), N1-, N(2-), and O5'-derivatives can be biologically significant. Our results shed new light on DNA modifications caused by chlorambucil, which is an important chemotherapeutic drug and a known carcinogen.

The cell transmembrane pH gradient in tumors enhances cytotoxicity of specific weak acid chemotherapeutics

The extracellular pH is lower in tumor than in normal tissue, whereas their intracellular pH is similar. In this study, we show that the tumor-specific pH gradient may be exploited for the treatment of cancer by weak acid chemotherapeutics. i.v.-injected glucose substantially decreased the electrode estimated extracellular pH in a xenografted human tumor while its intracellular pH, evaluated by (31)P magnetic resonance spectroscopy, remained virtually unchanged. The resulting increase in the average cell pH gradient caused a parallel increase in tumor growth delay by the weak acid chlorambucil (CHL). Regardless of glucose administration, the effect of CHL was significantly greater in tumors preirradiated with a large dose of ionizing radiation. This suggests that CHL was especially pronounced in radioresistant hypoxic cells possessing a larger transmembrane pH gradient. These results indicate that the naturally occurring cell pH gradient difference between tumor and normal tissue is a major and exploitable determinant of the uptake of weak acids in the complex tumor microenvironment. The use of such drugs may be especially effective in combination with radiation.

Synthesis, molecular modelling, and antiproliferative and cytotoxic effects of carbocyclic derivatives of distamycin with chlorambucil moiety

New carbocylic analogues of distamycin and netropsin with chlorambucil moieties 5-8 have been synthesised. Data from the ethidium displacement assay showed that these compounds bind in the minor groove of DNA. The observed reduced affinity to AT pairs and increased affinity towards GC sequences of the carbocyclic lexitropsins with chlorambucil moiety 5-8 in comparison with netropsin and distamycin was observed and rationalised by means of molecular modelling techniques. All of the compounds 5-8 showed antiproliferative and cytotoxic effects in the standard cell line of the mammalian tumour MCF-7.

Esters of chlorambucil with 2-substituted 1,4-dihydroxy-9,10-anthraquinones as multifunctional anticancer agents

Novel twelve esters of chlorambucil with 2-(1-hydroxyalkyl)-1,4-dihydroxy-9,10-anthraquinone were synthesized and tested for their antitumor activity in mice bearing S-180 ascitic cells as well as cytotoxic activity against L1210 cells. Eight of them were highly cytotoxic on L1210 cells (ED(50), <6 microg mL(-1)) and derivatives 1 and 12 (T/C, 200 and 205%) appeared more active in vivo than chlorambucil (T/C, 168%).