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Quinolin-6-Yloxyacetamides Are Microtubule Destabilizing Agents That Bind to the Colchicine Site of Tubulin.

ABSTRACT: Quinolin-6-yloxyacetamides (QAs) are a chemical class of tubulin polymerization inhibitors that were initially identified as fungicides. Here, we report that QAs are potent anti-proliferative agents against human cancer cells including ones that are drug-resistant. QAs act by disrupting the microtubule cytoskeleton and by causing severe mitotic defects. We further demonstrate that QAs inhibit tubulin polymerization in vitro. The high resolution crystal structure of the tubulin-QA complex revealed that QAs bind to the colchicine site on tubulin, which is targeted by microtubule-destabilizing agents such as colchicine and nocodazole. Together, our data establish QAs as colchicine-site ligands and explain the molecular mechanism of microtubule destabilization by this class of compounds. They further extend our structural knowledge on antitubulin agents and thus should aid in the development of new strategies for the rational design of ligands against multidrug-resistant cancer cells.

SUBMITTER: Sharma A

PROVIDER: S-EPMC5535829 | biostudies-literature | 2017 Jun

REPOSITORIES: biostudies-literature

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Quinolin-6-Yloxyacetamides Are Microtubule Destabilizing Agents That Bind to the Colchicine Site of Tubulin.

Sharma Ashwani A Sáez-Calvo Gonzalo G Olieric Natacha N de Asís Balaguer Francisco F Barasoain Isabel I Lamberth Clemens C Díaz J Fernando JF Steinmetz Michel O MO

International journal of molecular sciences 20170622 7

Quinolin-6-yloxyacetamides (QAs) are a chemical class of tubulin polymerization inhibitors that were initially identified as fungicides. Here, we report that QAs are potent anti-proliferative agents against human cancer cells including ones that are drug-resistant. QAs act by disrupting the microtubule cytoskeleton and by causing severe mitotic defects. We further demonstrate that QAs inhibit tubulin polymerization in vitro. The high resolution crystal structure of the tubulin-QA complex reveale ...[more]

PMID: 28640209

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Project description:IntroductionOne of the main reasons for disease recurrence in the curative breast cancer treatment setting is the development of drug resistance. Microtubule targeted agents (MTAs) are among the most commonly used drugs for the treatment of breaset cancer and therefore overcoming taxane resistance is of primary clinical importance. Our group has previously demonstrated that the microtubule dynamics of docetaxel-resistant MCF-7TXT cells are insensitivity to docetaxel due to the distinct expression profiles of ?-tubulin isotypes in addition to the high expression of p-glycoprotein (ABCB1). In the present investigation we examined whether taxane-resistant breast cancer cells are more sensitive to microtubule destabilizing agents including vinca alkaloids and colchicine-site binding agents (CSBAs) than the non-resistant cells.MethodsTwo isogenic MCF-7 breast cancer cell lines were selected for resistance to docetaxel (MCF-7TXT) and the wild type parental cell line (MCF-7CC) to examine if taxane-resistant breast cancer cells are sensitive to microtubule-destabilizing agents including vinca alkaloids and CSBAs. Cytotoxicity assays, immunoblotting, indirect immunofluorescence and live imaging were used to study drug resistance, apoptosis, mitotic arrest, microtubule formation, and microtubule dynamics.ResultsMCF-7TXT cells were demonstrated to be cross resistant to vinca alkaloids, but were more sensitive to treatment with colchicine compared to parental non-resistant MCF-7CC cells. Cytotoxicity assays indicated that the IC50 of MCF-7TXT cell to vinorelbine and vinblastine was more than 6 and 3 times higher, respectively, than that of MCF-7CC cells. By contrast, the IC50 of MCF-7TXT cell for colchincine was 4 times lower than that of MCF-7CC cells. Indirect immunofluorescence showed that all MTAs induced the disorganization of microtubules and the chromatin morphology and interestingly each with a unique pattern. In terms of microtubule and chromain morphology, MCF-7TXT cells were more resistant to vinorelbine and vinblastine, but more sensitive to colchicine compared to MCF-7CC cells. PARP cleavage assay further demonstrated that all of the MTAs induced apoptosis of the MCF-7 cells. However, again, MCF-7TXT cells were more resistant to vinorelbine and vinblastine, and more sensitive to colchicine compared to MCF-7CC cells. Live imaging demonstrated that the microtubule dynamics of MCF-7TXT cells were less sensitive to vinca alkaloids, and more sensitive to colchicine. MCF-7TXT cells were also noted to be more sensitive to other CSBAs including 2MeOE2, ABT-751 and phosphorylated combretastatin A-4 (CA-4P).ConclusionDocetaxel-resistant MCF-7TXT cells have demonstrated cross-resistance to vinca alkaloids, but appear to be more sensitive to CSBAs (colchicine, 2MeOE2, ABT-751 and CA-4P) compared to non-resistant MCF-7CC cells. Taken together these results suggest that CSBAs should be evaluated further in the treatment of taxane resistant breast cancer.

Project description:Background:Drug resistance and chemotherapy-induced peripheral neuropathy continue to be significant problems in the successful treatment of acute lymphoblastic leukemia (ALL). 5,7-Dibromo-N-alkylisatins, a class of potent microtubule destabilizers, are a promising alternative to traditionally used antimitotics with previous demonstrated efficacy against solid tumours in vivo and ability to overcome P-glycoprotein (P-gp) mediated drug resistance in lymphoma and sarcoma cell lines in vitro. In this study, three di-brominated N-alkylisatins were assessed for their ability to retain potency in vincristine (VCR) and 2-methoxyestradiol (2ME2) resistant ALL cell lines. For the first time, in vitro neurotoxicity was also investigated in order to establish their suitability as candidate drugs for future use in ALL treatment. Methods:Vincristine resistant (CEM-VCR R) and 2-methoxyestradiol resistant (CEM/2ME2-28.8R) ALL cell lines were used to investigate the ability of N-alkylisatins to overcome chemoresistance. Interaction of N-alkylisatins with tubulin at the the colchicine-binding site was studied by competitive assay using the fluorescent colchicine analogue MTC. Human neuroblastoma SH-SY5Y cells differentiated into a morphological and functional dopaminergic-like neurotransmitter phenotype were used for neurotoxicity and neurofunctional assays. Two-way ANOVA followed by a Tukey's post hoc test or a two-tailed paired t test was used to determine statistical significance. Results:CEM-VCR R and CEM/2ME2-28.8R cells displayed resistance indices of?>?100 to VCR and 2-ME2, respectively. CEM-VCR R cells additionally displayed a multi-drug resistant phenotype with significant cross resistance to vinblastine, 2ME2, colchicine and paclitaxel consistent with P-gp overexpression. Despite differences in resistance mechanisms observed between the two cell lines, the N-alkylisatins displayed bioequivalent dose-dependent cytotoxicity to that of the parental control cell line. The N-alkylisatins proved to be significantly less neurotoxic towards differentiated SH-SY5Y cells than VCR and vinblastine, evidenced by increased neurite length and number of neurite branch points. Neuronal cells treated with 5,7-dibromo-N-(p-hydroxymethylbenzyl)isatin showed significantly higher voltage-gated sodium channel function than those treated with Vinca alkaloids, strongly supportive of continued action potential firing. Conclusions:The N-alkylisatins are able to retain cytotoxicity towards ALL cell lines with functionally distinct drug resistance mechanisms and show potential for reduced neurotoxicity. As such they pose as promising candidates for future implementation into anticancer regimes for ALL. Further in vivo studies are therefore warranted.

Dataset Information

Quinolin-6-Yloxyacetamides Are Microtubule Destabilizing Agents That Bind to the Colchicine Site of Tubulin.

Publications

Quinolin-6-Yloxyacetamides Are Microtubule Destabilizing Agents That Bind to the Colchicine Site of Tubulin.

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