Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.3.1.21 (CPT)
 4,580 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

5H-8,9-dimethoxy-5-(2-N,N-dimethylaminoethyl)-2,3-methylenedioxydibenzo[c,h][1,6]naphthyridin-6-one (ARC-111) has potent TOP1-targeting activity and pronounced antitumor activity. Several analogues of ARC-111 were synthesized with NH2, N-alkyl, N,N-dialkyl, pyrrolidinyl, piperidinyl, and piperazinyl substituents at the 2-position of the 5-ethyl group. The relative TOP1-targeting activity and cytotoxicity of these structural analogues were assessed in RPMI8402 and P388 tumor cells and their camptothecin-resistant variants CPT-K5 and P388/CPT45, respectively. Potent TOP1-targeting activity was retained within a series of mono N-alkyl analogues that included NHCH2CH3, NHCH(CH3)2, and NHC(CH3)3. TOP1-targeting activity was diminished by the presence of a N-benzyl moiety. In a comparison of a series of N-alkyl-N-isopropyl analogues, activity decreased in the order CH3 > CH2CH3 > CH(CH3)2. Cytotoxicity in RPMI8402 and P388 did correlate with TOP1-targeting activity. Cytotoxic activity was also determined in KB3-1 cells and its variants KB/V-1 and KBH5.0. As KB/V-1 cells overexpress MDR1 and KBH5.0 cells overexpress BCRP, decreased cytotoxicity in these cell lines relative to the parent cell line is indicative of compounds that are substrates for these efflux transporters. In view of their diminished cytotoxicity in KB/V-1 cells, it appears that the likely demethylated metabolites of ARC-111, i.e., where NH2 or NHCH3 replaces the N(CH3)2 at the 2-position of the 5-ethyl substituent, are substrates for MDR1. In contrast, no significant difference in cytotoxicity among these three cell lines was observed with other N-alkyl analogues, including NHC2H5, NHCH(CH3)2, NHC(CH3)3, N(CH3)2, N(CH2CH3)2, NCH3(CH(CH3)2), and either the pyrrolidinyl or the piperidinyl analogues. The 2-(piperazinyl) analogues were associated with diminished cytotoxicity in KB/V-1 cells, suggesting that the second basic amino substituent is associated with their recognition as substrates by MDR1. Comparative studies on the antitumor activity of ARC-111 and its N-demethylated derivatives (the NHCH3 and NH2 analogues) against SJ-BT45 medulloblastoma xenografts in scid mice revealed that the secondary amine metabolite is at least as active as ARC-111 in vivo, although the primary amine derivative was significantly less potent.
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PMID:5-(2-aminoethyl)dibenzo[c,h][1,6]naphthyridin-6-ones: variation of n-alkyl substituents modulates sensitivity to efflux transporters associated with multidrug resistance. 1568 63

Human Topors has originally been identified as binding partner of p53 and DNA topoisomerase I (TOP1). It can function as both an ubiquitin and SUMO-1 E3 ligase for p53. Here we demonstrate that Topors enhances the formation of high-molecular weight SUMO-1 conjugates of TOP1 in a reconstituted in vitro system and also in human osteosarcoma cells, similar to treatment with CPT. In contrast to the situation observed with p53, overall sumoylation levels were rather unaffected. Experiments with TOP1 point mutants strongly suggest that the high-molecular weight conjugates represent SUMO-1 chains formed on a limited number of SUMO-1 acceptor sites.
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PMID:The E3 ligase Topors induces the accumulation of polysumoylated forms of DNA topoisomerase I in vitro and in vivo. 1797 81

A series of 6-arylamino-7-chloro-quinazoline-5,8-diones have been evaluated as novel human topoisomerase I (TOP1) inhibitors based on the antitumor activity of 1,4-naphthoquinone. Besides their in vitro cytotoxicity, their ability to inhibit human TOP1-DNA in vitro was tested with human TOP1 and a supercoiled (Form I) plasmid substrate DNA (Park et al., 2004). Using the flexible docking program, QXP, we have developed ternary complex models by docking camptothecin and ten 6-arylamino-7-chloro-quinazoline-5,8-dione analogs into the X-ray crystal structure of the human TOP1-DNA binary complex. The compound binding modes substantiated their potential inhibitory activities against TOP1 in the relaxation assay. Compounds whose templates the 6-arylamino-7-chloro-quinazoline-5,8-dione moiety intercalated between the -1 and +1 base pairs of the scissile strand showed good inhibitory activities. The template of compounds with poor inhibitory activities intercalated between the DNA base pairs of the nonscissile strand. The interaction of the compounds and the human TOP1-DNA binary complex were stabilized by an array of hydrogen bonds and hydrophobic interactions with the TOP1 residues, DNA bases, and water molecules. Docking results from the QXP program suggested potential binding modes of each non-CPT type compound in the human TOP1-DNA cleavable complex, which could provide a rational basis for future TOP1 inhibitor development.
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PMID:Binding mode analysis of topoisomerase inhibitors, 6-arylamino-7-chloro-quinazoline-5,8-diones, within the cleavable complex of human topoisomerase I and DNA. 1825 39

Tumor cells are known to exhibit highly varied sensitivity to camptothecins (CPT; e.g., irinotecan and topotecan). However, the factors that determine CPT sensitivity/resistance are largely unknown. Recent studies have shown that the ubiquitin-like protein, IFN-stimulated gene 15 (ISG15), which is highly elevated in many human cancers and tumor cell lines, antagonizes the ubiquitin/proteasome pathway. In the present study, we show that ISG15 is a determinant for CPT sensitivity/resistance possibly through its effect on proteasome-mediated repair of topoisomerase I (TOP1)-DNA covalent complexes. First, short hairpin RNA-mediated knockdown of either ISG15 or UbcH8 (major E2 for ISG15) in breast cancer ZR-75-1 cells decreased CPT sensitivity, suggesting that ISG15 overexpression in tumors could be a factor affecting intrinsic CPT sensitivity in tumor cells. Second, the level of ISG15 was found to be significantly reduced in several tumor cells selected for resistance to CPT, suggesting that altered ISG15 regulation could be a significant determinant for acquired CPT resistance. Parallel to reduced CPT sensitivity, short hairpin RNA-mediated knockdown of either ISG15 or UbcH8 in ZR-75-1 cells resulted in increased proteasomal degradation of CPT-induced TOP1-DNA covalent complexes. Taken together, these results suggest that ISG15, which interferes with proteasome-mediated repair of TOP1-DNA covalent complexes, is a potential tumor biomarker for CPT sensitivity.
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PMID:ISG15 as a novel tumor biomarker for drug sensitivity. 1856 15

Several decades of research have identified Mcm10 hanging around the replisome making several critical contacts with a number of proteins but with no real disclosed function. Recently, the O'Donnell laboratory has been better able to map the interactions of Mcm10 with a larger Cdc45/GINS/MCM (CMG) unwinding complex placing it at the front of the replication fork. They have shown biochemically that Mcm10 has the impressive ability to strip off single-strand binding protein (RPA) and reanneal complementary DNA strands. This has major implications in controlling DNA unwinding speed as well as responding to various situations where fork reversal is needed. This work opens up a number of additional facets discussed here revolving around accessing the DNA junction for different molecular purposes within a crowded replisome. Abbreviations: alt-NHEJ: Alternative Nonhomologous End-Joining; CC: Coli-Coil motif; CMG: Cdc45/GINS/MCM2-7; CMGM: Cdc45/GINS/Mcm2-7/Mcm10; CPT: Camptothecin; CSB: Cockayne Syndrome Group B protein; CTD: C-Terminal Domain; DSB: Double-Strand Break; DSBR: Double-Strand Break Repair; dsDNA: Double-Stranded DNA; GINS: go-ichi-ni-san, Sld5-Psf1-Psf2-Psf3; HJ Dis: Holliday Junction dissolution; HJ Res: Holliday Junction resolution; HR: Homologous Recombination; ICL: Interstrand Cross-Link; ID: Internal Domain; MCM: Minichromosomal Maintenance; ND: Not Determined; NTD: N-Terminal Domain; PCNA: Proliferating Cell Nuclear Antigen; RPA: Replication Protein A; SA: Strand Annealing; SE: Strand Exchange; SEW: Steric Exclusion and Wrapping; ssDNA: Single-Stranded DNA; TCR: Transcription-Coupled Repair; TOP1: Topoisomerase.
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PMID:Fine-tuning of the replisome: Mcm10 regulates fork progression and regression. 3101 74