Cytotoxic and DNA-damaging properties of N-[2-(dimethylamino)ethyl]acridine-4-carboxamide (DACA) and its analogues

Different positions of amide side chains on the benzimidazo[1,2-a]quinoline skeleton strongly influence biological activity

Benzimidazo[1,2-a]quinolines substituted with amide chains have been evaluated for their antiproliferative, antibacterial and antiviral activity in vitro.

Glyfoline induces mitotic catastrophe and apoptosis in cancer cells

Glyfoline exhibits cytotoxic activity in vitro and antitumor activity in mice bearing murine or human solid tumors, but the underlying mechanisms are unknown. In our study, we found that glyfoline inhibited cell growth and induced accumulation of mitotic cells in human cancer cell lines. Glyfoline induced the appearance of spindle abnormalities, chromosome mis-segregation, multipolar cell division and multiple nuclei, all of which are indicative of mitotic catastrophe. However, glyfoline did not bind to DNA and did not inhibit or stabilize tubulin polymerization, but slightly increased the resistance of mitotic spindles to nocodazole-induced disassembly. In addition, microtubule aster formation was significantly enhanced in the extract prepared from glyfoline-arrested mitotic cells compared to that from synchronized mitotic cells. When Eg5, a mitotic kinesin that plays an essential role in establishing mitotic spindle bipolarity, was inhibited using S-trityl-cysteine in glyfoline-treated cells, formation of spindle multipolarity, multipolar cell division, and multinuclei was significantly reduced. After glyfoline-mediated arrest of cells at mitosis, considerable poly(ADP-ribose) polymerase degradation was induced and the number of annexin V-positive cells significantly increased, indicating that glyfoline ultimately induces apoptosis. Small interfering RNA-mediated silencing of the spindle checkpoint proteins BUBR1 and MAD2 markedly reduced induction of mitotic cell accumulation, but did not affect glyfoline-induced mitotic catastrophe and apoptosis. Thus, glyfoline induces mitotic catastrophe probably by enhancing microtubule aster formation and subsequent apoptosis in cancer cells independently of spindle checkpoint function.

Bioelectronome. Integrated Approach to Receptor Chemistry, Radicals, Electrochemistry, Cell Signaling, and Physiological Effects Based on Electron Transfer

Bioelectronome refers to the host of electron transfer (ET) reactions that occur in living systems. This review presents an integrated approach to receptor chemistry based on electron transfer, radicals, electrochemistry, cell signaling, and end result. First, receptor activity is addressed from the unifying standpoint of redox transformations in which various receptors are discussed. After a listing of receptor-binding modes, receptor chemistry is treated with focus on generation of reactive oxygen species (ROS), activation by ROS, and subsequent cell signaling involving ROS. A general electrostatic mechanism is proposed for receptor-ligand action with supporting evidence. Cell-signaling processes appear to entail electron transfer, ROS, redox chains, and relays. The widespread involvement of phosphate from phosphorylation may be rationalized electrostatically by analogy with DNA phosphate. Extensive evidence supports important participation of ET functionalities in the mechanism of drugs and toxins. The integrated approach is applied to the main ET classes, namely, quinones, metal complexes, iminium species, and aromatic nitro compounds.

Effect of phenazine compounds XR11576 and XR5944 on DNA topoisomerases

PURPOSE

Previous in vitro cleavage data showed that XR11576 and XR5944 stabilised topoisomerase I and topoisomerase II complexes on DNA in a dose-dependent fashion. However, some studies indicated a possible topoisomerase-independent mechanism of action for these drugs.

METHODS

Three methods, the TARDIS assay, immunoband depletion and the K(+)/SDS assay have been used to assess topoisomerase complex formation induced by XR11576 or XR5944 in human leukaemic K562 cells.

RESULTS

TARDIS and immunoband depletion assays demonstrated that XR11576 and XR5944 induced complex formation for both topoisomerase I and topoisomerase II (alpha and beta) in a dose- and time-dependent manner, following exposure times of 24 and 48 h at concentrations of 1 or 10 microM. The K(+)/SDS assay showed the formation of protein/DNA complexes after a 1 h exposure to 1 or 10 muM XR11576.

CONCLUSION

Our data confirm that XR11576 or XR5944 can form topoisomerase complexes, after long periods of exposure.

The role of topoisomerases and RNA transcription in the action of the antitumour benzonaphthyridine derivative SN 28049

PURPOSE

SN 28049 (N-[2-(dimethylamino)ethyl]-2,6-dimethyl-1-oxo-1,2-dihydrobenzo[b]-1,6-naphthyridine-4-carboxamide) is a DNA intercalating drug that binds selectively to GC-rich DNA and shows curative activity against the Colon 38 adenocarcinoma in mice. We wished to investigate the roles of topoisomerase (topo) I, topo II and RNA transcription in the action of SN 28049.

METHODS

We used clonogenic assays to study the cytotoxicity of SN 28049; RNA interference and enzyme assays to examine the role of topo I in SN 28049 action; 3H uridine incorporation and reporter assays to study its effects on transcription; and RT-PCR to examine its ability to reduce endogenous h-TERT expression.

RESULTS

In clonogenic assays, SN 28049 showed a biphasic cytotoxic dose response curve in H460 cells typical of acridine derivatives such as N-[2-(dimethylamino)ethyl]acridine-4-carboxamide (DACA) although it was approximately 16-fold more potent. Down-regulation of topo IIalpha in HTETOP cells reduced the cytotoxicity of SN 28049, establishing its action as a topo IIalpha poison. Surprisingly, down-regulation of topo I in H460 cells by RNA interference sensitised them to the actions of SN 28049 and other topo II poisons. SN 28049 also inhibited topo I-mediated relaxation of supercoiled plasmid DNA. SN 28049 was also an inhibitor of transcription in HEK293 cells and was more potent at reducing luciferase expression from a GC-rich SP-1 binding promoter than from a non-GC-rich AP-1 binding promoter. The drug also reduced luciferase reporter gene expression driven by the SP-1-binding survivin promoter as well as reducing endogenous h-TERT expression in HEK293 cells whose promoter also contains SP-1 binding sites.

CONCLUSION

We conclude that SN 28049 has a complex action that may involve poisoning of topo IIalpha, suppression of topo I and inhibition of gene transcription from promoters with SP-1 sites. These actions may contribute to the promising experimental solid tumour anticancer activity of SN 28049.

Anthracyclines potentiate activity against murine leukemias L1210 and P388 in vivo and in vitro

The interactions of 2-chlorodeoxyadenosine (2-CdA, cladribine) and three anthracyclines: doxorubicin (DOX), idarubicin (IDA) and mitoxantrone (MIT) were evaluated on murine leukemias P388 and L1210. Prolongation of survival time of animals receiving drugs in combination compared to mice treated with drugs in monotherapy was tested. We have also evaluated interactions of the cytostatics on murine leukemias in vitro by measuring their inhibitory effects on P388 and L1210 cell proliferation. We have observed a synergistic effect of MIT and IDA in combination with 2-CdA on P388 leukemia resulting in an increase of life span (ILS)=226% in case of MIT+2-CdA and ILS=126% in the case of IDA+2-CdA, whereas 2-CdA used as a sole drug resulted in an ILS=47%. The survival time of animals inoculated with P388 leukemic cells and treated with DOX+ 2-CdA was similar to ILS gained by DOX monotherapy (178% and 200% respectively). The mice bearing L1210 leukemia receiving combined chemotherapy lived significantly longer than the animals on single agent regimens. The animals treated with schedule 2-CdA+MIT lived significantly longer (P=0.004) as compared to the groups receiving drugs in monotherapy (ILS of 2-CdA+MIT group=60%, ILS of MIT group 33%, and 2-CdA group 33%). Finally, combination of DOX or IDA with 2-CdA resulted in ILS =73% (2-CdA+DOX regimen), and ILS=60% in case of 2-CdA+IDA regimen, which is significantly higher than ILS gained on monotherapy schedules. In vitro tests revealed that all tested anthracyclines enhance the antiproliferative activity of 2-CdA against L1210 and P388 leukemic cells (P<0.05). Our study has shown that all anthracyclines potentiate 2-CdA antileukemic activity, both in vivo and in vitro. It failed however to point the best one to be combined with cladribine. We suggests that further clinical trials with such combinations are needed.