DNA-intercalating Antitumor Agents Research Articles

Design, synthesis, biological evaluation and multi spectroscopic studies of novel 2-styrylquinoline-carboxamide derivatives as potential DNA intercalating anticancer agents.

In this study, novel 2-styrylquinoline derivatives possessing a planar aromatic system and a flexible side chain with an amino substituent were designed and synthesized as DNA-intercalating antitumor agents. The cytotoxic activity of the synthesized compounds was evaluated against four cancer cell lines including MCF-7 (breast cancer cells), A549 (lung epithelial cancer cells), HCT116 (colon cancer cells) and normal cell line L929 (mouse fibroblast cell line). The results displayed that the anti-cancer activity of the target quinolines is sensitive to the lipophilic nature of the C-6 and C-7 quinoline substituents. The anticancer activity of most of the target quinolines against MCF-7 and A549 cells was more than those of HCT116. Compound 3h possessing two methyl groups at the C-6 and C-7 of quinoline ring displayed the most cytotoxicity with IC50 value of 5.7µM against A549 cancer cells. Interaction of compound 3h with calf thymus DNA (ctDNA) was investigated by means of UV absorption spectrophotometry, fluorescence spectroscopy, circular dichroism (CD), Resonance light scattering (RLS), viscos metric techniques and also by docking and molecular dynamic studies. RLS intensity, fluorescence quenching of ctDNA and fluorescence quenching EtBr-ctDNA and AO-ctDNA complexes augmented with increasing of compound 3h concentration, significant increasing in viscosity and melting point of ctDNA in the presence of compound 3h, absorbance increasing of ctDNA-compound 3h complex by increasing of NaCl and KI concentrations, higher Ksv value for dsctDNA (3.03×104 M-1) compared to ssctDNA (1.31×104 M-1), circular dichroism (CD) studies, docking and molecular dynamic studies revealed that compound 3h can interact with ctDNA through intercalation into DNA.

Design, synthesis and biological evaluation of novel benzo- and tetrahydrobenzo-[h]quinoline derivatives as potential DNA-intercalating antitumor agents

A new series of benzo- and tetrahydro benzo-[h]quinoline bearing a flexible (dimethylamino)ethylcarboxamide side chain was designed and synthesized as DNA-intercalating antitumor agents. The cytotoxic activity of the synthesized compounds was evaluated against four human cancer cell lines including MCF-7, A2780, C26 and A549. In general, saturated quinolines (tetrahydrobenzo[h]quinolines) exhibited more cytotoxicity compared to their corresponding unsaturated quinolines (benzo[h]quinolines). Compound 6e showed significant cytotoxicity against all four human cancer cell lines with IC50 values ranging from 1.86 to 3.91 μM. The interaction of the selected compounds showed significant cytotoxicity (6b, 6e, 6i and 6j) with calf thymus DNA (CT-DNA) was studied by UV and florescent spectroscopy. In general, benzo[h]quinolines showed higher interacting effect with DNA than their corresponding saturated tetrahydrobenzo[h]quinolines. Compound 6i exhibited the most DNA intercalating effects among the series. The apoptotic induction potential of the most cytotoxic compounds (6e, 6b and 6i) in A549 cells was studied using Annexin V-FITC/Propidium iodide staining assay. Compound 6e which showed the most cytotoxic effect against A549 cancer cells also exhibited stronger apoptotic induction activity in comparison with 6b and 6i.The docking was performed in order to study the DNA interaction properties of these compounds. According to the computational data, these compounds can interact with DNA as DNA-intercalating agents.

3,6-Bis(3-alkylguanidino)acridines as DNA-intercalating antitumor agents

A series of 3,6-bis(3-alkylguanidino) acridines was prepared and the interaction of these novel compounds with calf thymus DNA was investigated with UV–vis, fluorescence and circular dichroism spectroscopy, in addition to DNA melting techniques. The binding constants K were estimated to range from 1.25 to 5.26 × 105 M−1, and the percentage of hypochromism was found to be 17–42% (from spectral titration). UV–vis, fluorescence and circular dichroism measurements indicated that the compounds act as effective DNA-intercalating agents. Electrophoretic separation proved that ligands 6a–e relaxed topoisomerase I at a concentration of 60 μM, although only those with longer alkyl chains were able to penetrate cell membranes and suppress cell proliferation effectively. The biological activity of novel compounds was assessed using different techniques (cell cycle distribution, phosphatidylserine externalization, caspase-3 activation, changes in mitochondrial membrane potential) and demonstrated mostly transient cytostatic action of the ethyl 6c and pentyl 6d derivatives. The hexyl derivative 6e proved to be the most cytotoxic. Different patterns of cell penetration were also observed for individual derivatives. Principles of molecular dynamics were applied to explore DNA–ligand interactions at the molecular level.

Isoxazolidinyl polycyclic aromatic hydrocarbons as DNA-intercalating antitumor agents

The second generation and an isosteric series of isoxazolidinyl polycyclic aromatic hydrocarbons, as DNA-intercalator agents designed to act on remotely implanted tumors, have been synthesized in good yields according to the 1,3-dipolar cycloaddition methodology. The structure of the obtained cycloadducts has been determined by NOE experiments and supported by computational studies at PM3 level. The utility of this new template in the synthesis of structures designed to capitalize on its intercalative properties has been examined. All the obtained compounds have been tested for their in vitro cytotoxic activity and the most potent of them showed an IC50 of 9 μM upon the human lung cancer (A-549) cell and a binding constant, for the intercalation with calf thymus DNA, of 9.6 × 104 M−1. Biological and docking studies showed that these compounds complex exclusively by intercalation between base pairs, approaching the DNA from its minor groove, with a neat selectivity for the AT or GC nucleobases.

Cellular uptake and interaction with purified membranes of rebeccamycin derivatives

Rebeccamycin is an antitumor antibiotic possessing a DNA-intercalating indolocarbazole chromophore linked to a glycosyl residue. The carbohydrate moiety of rebeccamycin and related synthetic analogues, such as the potent antitumor drug NB-506 (6- N-formylamino-12,13-dihydro-1,11-dihydroxy-13-(β- d-glucopyranosyl)-5 H-indolo[2,3- a]pyrrolo-[3,4- c]carbazole-5,7-(6 H)-dione), is a key element for both DNA-binding and inhibition of DNA topoisomerase I. In this study, we have investigated the cellular uptake of rebeccamycin derivatives and their interaction with purified membranes. The transport of radiolabeled [ 3H]dechlorinated rebeccamycin was studied using the human leukemia HL60 and melanoma B16 cell lines as well as two murine leukemia cell lines sensitive (P388) or resistant (P388CPT5) to camptothecin. In all cases, the uptake is rapid but limited to about 6% of the drug molecules. In HL60 cells, the uptake entered a steady-state phase of intracellular accumulation of about 0.26±0.05 pmol/10 6 cells, which persisted to at least 90 min. The efflux of exchangeable radiolabeled molecules was relatively weak. Fluorescence studies were performed to compare the interaction of a rebeccamycin derivative and its aglycone with membranes purified from HL60 cells. The glycosylated drug molecules bound to the cell membranes can be extracted upon washing with buffer or by adding an excess of DNA. In contrast, the indolocarbazole drug lacking the carbohydrate domain remains tightly bound to the membranes with very little or no exchange upon the addition of DNA. The membrane transport and binding properties of indolocarbazole drugs related to rebeccamycin are reminiscent to those of other DNA-intercalating antitumor agents. The uptake most likely occurs via a passive diffusion through the plasma membranes and the glycosyl residue of the drug plays an essential role for the translocation of the drug from the membranes to the internal cell components, such as DNA.

Potential antitumor agents. 64. Synthesis and antitumor evaluation of dibenzo[1,4]dioxin-1-carboxamides: a new class of weakly binding DNA-intercalating agents.

A series of substituted dibenzo[1,4]dioxin-1-carboxamides has been synthesized and evaluated for in vitro and in vivo antitumor activity. The required substituted dibenzo[1,4]dioxin-1-carboxylic acids were prepared by a variety of methods. No regiospecific syntheses were available for many of these, and separation of the mixtures of regioisomers obtained was sometimes difficult. The dibenzo[1,4]dioxin-1-carboxamides are active against wild-type P388 leukemia in vitro and in vivo, with structure-activity relationships resembling those for both the acridine-4-carboxamide and phenazine-1-carboxamide series of DNA-intercalating antitumor agents. In all three series, substituents placed peri to the carboxamide sidechain (the 5-position in the acridines, and the 9-position in the phenazines and dibenzo[1,4]dioxins) enhance activity and potency. The 9-chlorodibenzodioxin-1-carboxamide was also curative against the remotely sited Lewis lung carcinoma. Several of the compounds showed much lower levels of cross-resistance to the P388/AMSA line than classical DNA-intercalating agents, which suggests that their primary mechanism of action may not be via interference with topoisomerase II alpha. This is of interest with regard to the development of drugs to combat resistance mechanisms which arise by the expression of the topo II beta isozyme.

Potential antitumor agents. 57. 2-Phenylquinoline-8-carboxamides as "minimal" DNA-intercalating antitumor agents with in vivo solid tumor activity.

A series of phenyl-substituted derivatives of the "minimal" DNA-intercalating agent N-[2-(dimethylamino)-ethyl]-2-phenylquinoline-8-carboxamide (1) have been synthesized and evaluated for in vivo antitumor activity, in a continuing search for active compounds of this class with the lowest possible DNA association constants. Substitution on the 2'-position of the phenyl ring gave compounds of lower DNA binding ability that did not intercalate DNA, indicating that it is necessary for the phenyl ring to be essentially coplanar with the quinoline for intercalative binding. An extensive series of 4'-substituted derivatives was evaluated, but there was no overall relationship between biological activity and substituent lipophilic or electronic properties. However, several compounds showed good solid tumor activity, with the 4'-aza derivative 18 being clearly superior to the parent compound, effecting about 50% cures in both leukemia and solid tumor models.

Potential antitumor agents. 55. 6-Phenylphenanthridine-4-carboxamides: a new class of DNA-intercalating antitumor agents.

Derivatives of the DNA-intercalating agent N-[2-(dimethylamino)ethyl]phenanthridine-4-carboxamide have been prepared and shown to have moderate in vivo antitumor activity against both the P388 leukemia and Lewis lung carcinoma. This demonstrates that the effective pharmacophore in the broad class of tricyclic carboxamides is not limited to linear tricyclic chromophores. Both 7 and the 6-phenyl derivative 10 have identical DNA binding properties, suggesting that the phenyl ring of 10 is not involved in the DNA intercalation site. A series of phenyl-substituted derivatives of 10 was evaluated. Aza substituents led to compounds with the highest in vivo cytotoxicity and in vivo P388 activity, but the in vivo solid tumor activity of the substituted 6-phenylphenanthridine-4-carboxamides was in general low.

Potential antitumor agents. 53. Synthesis, DNA binding properties, and biological activity of perimidines designed as "minimal" DNA-intercalating agents.

A series of compounds based on perimidine have been synthesized and evaluated for their DNA-binding properties and antitumor activity. The fused tricyclic permidine chromophore appears to be the minimal structural requirement for intercalative binding to DNA since the mode of binding could be dictated by the position of attachment of the side chain. The intercalating compounds have DNA association constants (log K = 5.8-6.5) and cytotoxic potencies (IC50 = 500-1500 nM) comparable to those shown by other classes of linear, tricyclic DNA-intercalating antitumor agents (acridinecarboxamides, phenazinecarboxamides), but none of the compounds showed in vivo activity.