Mechanism of action of the dual topoisomerase-I and -II inhibitor TAS-103 and activity against (multi)drug resistant cells

Fine-Tuning the Activation Mode of an 1,3-Indandione-Based Ruthenium(II)-Cymene Half-Sandwich Complex by Variation of Its Leaving Group

Fine-tuning of the properties of a recently reported 1,3-indandione-based organoruthenium complex is attempted to optimize the stability under physiological conditions. Previous work has shown its capacity of inhibiting topoisomerase IIα; however, fast aquation leads to undesired reactions and ligand cleavage in the blood stream before the tumor tissue is reached. Exchange of the chlorido ligand for six different N-donor ligands resulted in new analogs that were stable at pH 7.4 and 8.5. Only a lowered pH level, as encountered in the extracellular space of the tumor tissue, was capable of aquating the complexes. The 50% inhibitory concentration (IC₅₀) values in three human cancer cell lines differed only slightly, and their dependence on the utilized leaving group was smaller than what would be expected from their differences in cellular accumulation, but in accordance with the very minor variation revealed in measurements of the complexes’ lipophilicity.

A small organic compound enhances the religation reaction of human topoisomerase I and identifies crucial elements for the religation mechanism

The different steps of the human Top1 (topoisomerase I) catalytic cycle have been analysed in the presence of a pentacyclic-diquinoid synthetic compound. The experiments indicate that it efficiently inhibits the cleavage step of the enzyme reaction, fitting well into the catalytic site. Surprisingly the compound, when incubated with the binary topoisomerase-DNA cleaved complex, helps the enzyme to remove itself from the cleaved DNA and close the DNA gap, increasing the religation rate. The compound also induces the religation of the stalled enzyme-CPT (camptothecin)-DNA ternary complex. Analysis of the molecule docked over the binary complex, together with its chemical properties, suggests that the religation enhancement is due to the presence on the compound of two oxygen atoms that act as hydrogen acceptors. This property facilitates the deprotonation of the 5' DNA end, suggesting that this is the limiting step in the topoisomerase religation mechanism.

Mode of action of the novel phenazine anticancer agents XR11576 and XR5944

The substituted phenazines XR11576 and XR5944 were originally described as dual topoisomerase-I/II poisons. Subsequent reports, however, indicated that the association of their cytotoxicity with cellular topoisomerases was not clear. We set out to study this further using human tumour cell lines, PEO1 ovarian cancer, MDA-MB-231 breast cancer and variants with acquired resistance to VP-16 and XR11576: PEO1VPR, MB-231VPR, MB-231-11576R and camptothecin: PEO1CamR. Cytotoxicity testing [3-(4,5-dimethylthiazol-2yl)-2,5-diphenyl tetrazolium bromide assay], DNA-protein crosslink formation, cell cycle analysis (flow cytometry) for DNA content, apoptosis (flow cytometry) for Annexin V and Western blotting for apoptotic factors. Cytotoxicity testing showed potent cytotoxicity with no cross-resistance to XR11576 or XR5944 in VP-16 or camptothecin-resistant lines. Importantly, we have shown for the first time that the activities of XR5944 and XR11576 are similar as MB-231-11576R cells were resistant to both agents and to a similar extent. XR5944 showed the greatest, albeit slower, interaction with DNA with high levels of DNA-protein crosslinks. Levels of apoptosis in XR5944-treated cells were significantly less than those in VP-16 or XR11576 treatments, suggestive of a more cytostatic rather than cytotoxic mode of action. Interestingly, XR5944 failed to give rise to a G2/M blockade, in contrast to VP-16 or XR11576. XR5944 and XR11576, in line with a dual topoisomerase-I/II-directed mechanism of action, retain potent activity in tumour cells with acquired resistance to VP-16 and camptothecin. Although these agents appear to behave differently from each other according to experimental conditions, this study suggests a substantial overlap in their mechanism(s) of action.

N, N' (4,5-dihydro-1h-imidazol-2-yl)3-aza-1,10-decane-diamine and N, N'(4,5-dihydro-1H-imidazol-2-yl)3-aza-1, 10-dodecane-diamine antagonize cell proliferation as selective ligands towards topoisomerase II

New alkyl imidazoline derivatives have been synthesized as potential anti-cancer agents. The anti-proliferative activity of these compounds, evaluated against representative human haematological and solid neoplastic cell lines, showed that N, N'-di (4,5-dihydro-1H-imidazol-2-yl)3-aza-1,10-decane-diamine (8) and N, N'-di (4,5-dihydro-1H-imidazol-2-yl)3-aza-1,10-dodecane-diamine (9) were the most active compounds; in fact, they inhibited the cell proliferation at submicromolar concentrations. In enzyme assays, compound 9 turned out to be an inhibitor of topoisomerase II at concentrations comparable with those of the reference topoisomerase II inhibitor, etoposide.

Synthesis, photochemical synthesis, DNA binding and antitumor evaluation of novel cyano- and amidino-substituted derivatives of naphtho-furans, naphtho-thiophenes, thieno-benzofurans, benzo-dithiophenes and their acyclic precursors

As a part of the research on the improvement of an alternative to conventional photodynamic therapy by light-induced formation of intercalators, we synthesized a series of novel heterocyclic compounds and their acyclic precursors. We now report details about their synthesis/characterization in respect to their potential of photoinduced cyclization, interactions with DNA and inhibition of the tumor cell growth in vitro. Among studied compounds only amidino-furyl-substituted phenyl acrylates were efficiently converted to the corresponding naphthofuranes, while their thiophene analogues, all non-charged derivatives and amidino-phenyl-substituted analogues didn't show acceptable photoconversion. The significantly stronger antiproliferative activity of cyclic analogues could be correlated to the property of these molecules to intercalate into DNA. The acyclic molecules did not show any interaction with DNA, correlating with the inferior biological activity, except for one cyano-bearing molecule.

A review of selected anti-tumour therapeutic agents and reasons for multidrug resistance occurrence

It is assumed that proteins from the ABC family (i.e., glycoprotein P (Pgp)) and a multidrug resistance associated protein (MRP) play a main role in the occurrence of multidrug resistance (MDR) in tumour cells. Other factors that influence the rise of MDR are mechanisms connected with change in the effectiveness of the glutathione cycle and with decrease in expression of topoisomerases I and II. The aim of this review is to characterize drugs applied in anti-tumour therapy and to describe the present state of knowledge concerning the mechanisms of MDR occurrence, as well as the pharmacological agents applied in reducing this phenomenon.

Synthesis andin vitro cytotoxicity of 1,3-dioxoindan-2-carboxylic acid arylamides

A series of 1,3-dioxoindan-2-carboxylic acid arylamides were synthesized and evaluated for in vitro cytotoxicity against four human cancer cell lines (HOP62, SK-OV-3, MD-MB-468 and T-47D). The most active was compound 3e (1.2 microM against SK-OV-3 cell line) bearing a 4-methyl substituent.

Synthesis and antiproliferative activity of basic thioanalogues of merbarone

Three series of 5-substituted 1,3-diphenyl-6-(omega-dialkyl- and omega-cyclo-aminoalkyl)thio-2-thiobarbiturates (11-13) were synthesized as polysubstituted thioanalogues of merbarone, a topoisomerase II inhibitor acting on the catalytic site. To better understand pharmacophore requirements, a forth series of conformationally constrained analogues 14 was also prepared. Derivatives 11b,e, 14b,e,h,i,j were active in the low micromolar concentration range (IC(50): 3.3-4.3 microM), whereas compounds 11a,c,d,f,h,j and 13a,b,d,g,j and 14a,d,f showed IC(50) values between 10 and 15.5 microM. In contrast, compounds 12a-c,g-j, 13e,f,h and 14k were inactive. Cytotoxicity data provided from N.C.I. on selected compounds provided evidence that 11b,d, 13d,g and 14b,d,f,h,i,j were endowed with potent antiproliferative activity against leukemia and prostate cell lines (GI(50) up to 0.01 microM). In general, bicyclic derivatives 14 were up to 10-fold more potent than monocyclic counterparts against solid tumor-derived cell lines. SAR studies indicated that, in general, a certain tolerability in length of the alkyl side chains and in shape of distal amines is allowed in the four series, but in the monocyclic derivatives (11-13) antiproliferative activity was strongly affected by the nature of the 5-substituents (COOC(2)H(5)>COCH(3)>>C(6)H(5)). Compounds 11b and 14b were also evaluated against KB cell subclones expressing altered levels of topoisomerases or the multidrug resistance phenotype (MDR). In both cases the above compounds showed a decrease in potency. In enzyme assays, 11b and 14b turned out to be inhibitors of topoisonerase II as merbaron.

Cancer chemotherapy by liposomal 6-[12-(dimethylamino)ethyl]aminol-3-hydroxy-7H-indeno[2,1-clquinolin-7-one dihydrochloride (TAS-103), a novel anti-cancer agent

A novel anti-tumor agent, 6-[[2-(dimethylamino)ethyl]amino]-3-hydroxy-7H-indeno[2,1-c]quinolin-7-one dihydrochloride (TAS-103), effectively inhibits both topoisomerase I and II activities. To enhance anti-tumor efficacy and to reduce the side effects of the agent, liposomalization of TAS-103 was performed. TAS-103 was effectively entrapped in liposomes by a remote-loading method, and was stable at 4 degrees C and in the presence of 50% serum. To evaluate the anti-tumor efficacy of liposomal TAS-103, the growth inhibition against Lewis lung carcinoma cells in vitro and the therapeutic efficacy against solid tumor-bearing mice in vivo were examined. Liposomal TAS-103 showed strong cytotoxic effect against Lewis lung carcinoma cells in a dose dependent manner and effectively suppressed solid tumor growth accompanying longer survival time of tumor-bearing mice in comparison with the mice treated with free TAS-103. These results suggest that liposomal TAS-103 is useful for cancer therapy.

Synthesis and in vitro cytotoxicity of 4-alkyl- or 4-arylaminosubstituted cyclopenta[c]quinoline derivatives

Twelve 4-substituted cyclopenta[c]quinoline derivatives were synthesized and evaluated in vitro cytotoxicity against four human cancer cell lines (HOP62, SK-OV-3, MD-MB-468 and T-47D). The compounds 6c and 6e bearing p-anisidine and pyrrolidine side chain were more active than the others.

Synthesis, cytotoxicity, DNA interaction and topoisomerase II inhibition properties of tetrahydropyrrolo[3,4-a]carbazole-1,3-dione and tetrahydropyrido-[3,2-b]pyrrolo[3,4-g]indole-1,3-dione derivatives

Three tetrahydropyrrolo[3,4-a]carbazole-1,3-diones (6--8) and two tetrahydropyrido[3,2-b]pyrrolo[3,4-g]indole-1,3-diones (11--12) have been synthesized. Their interaction with DNA was probed by absorption and thermal melting studies. Compounds 8 and 12 both equipped with a hydroxyethyl-aminoethyl side-chain demonstrated higher affinities for poly(dA-dT)(2) than compounds 6, 7 and 11 bearing a dimethylaminoethyl side-chain. Circular and electric linear dichroism measurements showed that all five drugs behave as typical DNA intercalating agents. A plasmid cleavage assay was used to evaluate the capacity of the drugs to inhibit human topoisomerase II. Compounds 8 and 12 which bind strongly to DNA were found to stabilize DNA-topoisomerase II covalent complexes but their topoisomerase II inhibitory properties do not correlate with their cytotoxic potential. Compounds 6 and 7 are essentially inactive whereas compounds 8, 11 and 12 exhibit a high toxicity to P388 murine leukemia cells and provoke a marked accumulation in the G2/M phase of the cell cycle. These compounds form a new class of DNA-targeted antitumor agents.

Phase I clinical and pharmacogenetic study of weekly TAS-103 in patients with advanced cancer

PURPOSE

TAS-103 is an inhibitor of both topoisomerase I and II enzymes with broad antitumor activity. It is metabolized to TAS-103-glucuronide (TAS-103-G) predominantly by uridine diphosphate glucuronosyltransferase isoform 1A1 (UGT1A1). We conducted a phase I study to determine the maximum-tolerated dose (MTD) and dose-limiting toxicity (DLT) of TAS-103 when administered on a weekly schedule to patients with advanced cancer. In addition, we evaluated the influence of UGT1A1 genotype on the pharmacokinetics and toxicity of TAS-103.

PATIENTS AND METHODS

Thirty-two patients were treated with escalating doses (50 to 200 mg/m(2)) of TAS-103, administered intravenously over 1 hour each week for 3 weeks. Pharmacokinetic analysis was performed at the 130-, 160-, and 200-mg/m(2) dose levels. UGT1A1 genotypes were determined using reverse-transcription polymerase chain reaction techniques.

RESULTS

DLT (grade 3 neutropenia) was observed in 5 of 12 patients at 160 mg/m(2) and in 3 of 6 patients at 200 mg/m(2). At 160 mg/m(2), there was a significant correlation between areas under the curve (AUCs) for TAS-103 and TAS-103-G (r = 0.76, P <.05) and an apparent relationship between TAS-103 AUC and D 15 absolute neutrophil count (r = -0.63, P <.05, n = 11, one outlier excluded). UGT1A1 genotype did not influence clearance of TAS-103.

CONCLUSION

We recommend a dose of 130 to 160 mg/m(2), or 250 to 300 mg administered using the above weekly schedule for phase II studies. Further studies to characterize the pharmacodynamics and pharmacogenetics of TAS-103 are warranted.

Synthesis and in vitro cytotoxicity of 2-alkylaminosubstituted quinoline derivatives

Eight 2-alkylaminosubstituted 5,8-dimethoxy-4-methylquinolines and nine 2-alkylaminosubstituted or 2,6-disubstituted 4-methylquinoline-5,8-diones were synthesized and evaluated in vitro cytotoxicity against four human cancer cell lines (HOP62, SK-OV-3, HCT15 and SF295).