Cellular pharmacology of azatoxins (topoisomerase-II and tubulin inhibitors) in P-glycoprotein-positive and -negative cell lines

Béatrice Eymin 1 Eric Solary 2 Sylvie Chevillard 3 Laurence Dubrez 4 François Goldwasser 5 Olivier Duchamp 6 Philippe Genne 7 François Leteurtre 8 Yves Pommier 9
1 EA2021 - Groupe de Recherche sur le Cancer du Poumon
2 Hématopoïèse normale et pathologique
3 CEA DSV - Commissariat à l’énergie atomique et aux énergies alternatives [Fontenay-aux-Roses]
4 LNC - Lipides - Nutrition - Cancer [Dijon - U1231]
5 CHU Cochin [AP-HP]
6 Oncodesign
7 OncoDesign
8 IBITECS - Institut de Biologie et de Technologies de Saclay
9 Laboratory of Molecular Pharmacology
Abstract : Azatoxin (NSC 640737), a synthetic molecule, was rationally designed as a topoisomerase-II inhibitor and was shown to be a potent cytotoxic agent that inhibits both tubulin and topoisomerase II. A structure-activity relationship study allowed to select 3 derivatives that inhibit either tubulin (methylazatoxin) only or topoisomerase II (fluoroanilinoazatoxin and nitroanilino-azatoxin) in MTT assays performed on K562 and K562/ADM cells; the latter, expressing P-glycoprotein, indicated cross-resistance of K562/ADM cells to all 4 compounds. DNA double-strand breaks induced by the 3 azatoxins that inhibit topoisomerase II in vitro were decreased in K562/ADM as compared with K562 cells. Nitroanilino-azatoxin was the only compound for which resistance and reduced DNA damage observed in K562/ADM cells was partially reversed by verapamil, suggesting that nitroanilinoazatoxin was a substrate for P-glycoprotein. These results were confirmed by testing the cytotoxic activity of azatoxins on P-glycoprotein-expressing rat colon-carcinoma DHDK12/TRb cells in the absence and the presence of verapamil. Cell-cycle and mitotic-index studies indicated that azatoxin- and methyl-azatoxin-induced M-phase arrest was less in K562/ADM than in K562 cells. The G2 block induced by fluoro- and nitroanilinoazatoxins was delayed in K562/ADM cells. Verapamil increased cell-cycle inhibition induced by nitroanilinoazatoxin in K562/ADM cells without modifying cell-cycle effects of fluoroanilinoazatoxin. These results (i) are consistent with the specific inhibition of topoisomerase II or tubulin by azatoxin derivatives in cells; (ii) indicate that the nitro group of nitroanilinoazatoxin allows recognition and efflux by the P-glycoprotein; and (iii) suggest that cross-resistance of K562/ADM cells to other azatoxin derivatives is not mediated by P-glycoprotein.
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Journal articles
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https://www.hal.inserm.fr/inserm-02345528
Contributor : Beatrice Eymin <>
Submitted on : Monday, November 4, 2019 - 3:28:21 PM
Last modification on : Monday, February 10, 2020 - 6:12:53 PM

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UNIV-BOURGOGNE | CEA | FNCLCC | LNC-UMR866 | CEA-DRF | IGR

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Béatrice Eymin, Eric Solary, Sylvie Chevillard, Laurence Dubrez, François Goldwasser, et al.. Cellular pharmacology of azatoxins (topoisomerase-II and tubulin inhibitors) in P-glycoprotein-positive and -negative cell lines. International Journal of Cancer, Wiley, 1995, 63 (2), pp.268-275. ⟨10.1002/ijc.2910630221⟩. ⟨inserm-02345528⟩

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