Abstract | 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.
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Authors | David J A Bridewell, Andrew C G Porter, Graeme J Finlay, Bruce C Baguley |
Journal | Cancer chemotherapy and pharmacology
(Cancer Chemother Pharmacol)
Vol. 62
Issue 5
Pg. 753-62
(Oct 2008)
ISSN: 0344-5704 [Print] Germany |
PMID | 18175117
(Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
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Chemical References |
- Antineoplastic Agents
- N-(2-(dimethylamino)ethyl)-2,6-dimethyl-1-oxo-1,2-dihydroxybenzo(b)-1,6-naphthyridine-4-carboxamide
- Naphthyridines
- Protein Synthesis Inhibitors
- RNA, Neoplasm
- Luciferases
- DNA Topoisomerases, Type I
- DNA Topoisomerases, Type II
- Tetracycline
- Uridine
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Topics |
- Antineoplastic Agents
(pharmacology)
- Blotting, Western
- Cell Line, Tumor
- Cell Survival
(drug effects)
- DNA Topoisomerases, Type I
(metabolism, physiology)
- DNA Topoisomerases, Type II
(metabolism)
- Gene Expression
(drug effects)
- Genes, Reporter
(genetics)
- Humans
- Luciferases
(genetics)
- Naphthyridines
(pharmacology)
- Protein Synthesis Inhibitors
(pharmacology)
- RNA Interference
- RNA, Neoplasm
(biosynthesis, genetics)
- Reverse Transcriptase Polymerase Chain Reaction
- Tetracycline
(pharmacology)
- Transcription, Genetic
(physiology)
- Uridine
(metabolism)
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