Cancer Research 66, 3177-3187, March 15, 2006]
© 2006
Experimental Therapeutics, Molecular Targets, and Chemical Biology
Cancer Cell Mitochondria Are Direct Proapoptotic Targets for the Marine Antitumor Drug Lamellarin D
Jérôme Kluza1, Miguel-Angel Gallego2, Anne Loyens3, Jean-Claude Beauvillain3, José-Maria Fernandez Sousa-Faro4, Carmen Cuevas4, Philippe Marchetti2 and Christian Bailly1
1 Institut National de la Santé et de la Reserche Médicale U-524 and Institut de Recherche sur le Cancer de Lille; 2 Institut National de la Santé et de la Reserche Médicale U-459; 3 Institut National de la Santé et de la Reserche Médicale U-422 and Service d'Imagerie de l'Université de Lille II, Lille, France and 4 PharmaMar, Madrid, Spain
Requests for reprints: Philippe Marchetti, Institut National de la Santé et de la Reserche Médicale U-459, 1 Place de Verdun, 59045 Lille, France. E-mail: philippe.marchetti@lille.inserm.fr type=text/javascript>
Lamellarin D is a marine alkaloid with a pronounced cytotoxicity against a large panel of cancer cell lines and is a potent inhibitor of topoisomerase I. However, lamellarin D maintains a marked cytotoxicity toward cell lines resistant to the reference topoisomerase I poison camptothecin. We therefore hypothesized that topoisomerase I is not the only cellular target for the drug. Using complementary cell-based assays, we provide evidence that lamellarin D acts on cancer cell mitochondria to induce apoptosis. Lamellarin D, unlike camptothecin, induces early disruption of the inner mitochondrial transmembrane potential in the P388 leukemia cell line. The functional alterations are largely prevented by cyclosporin A, an inhibitor of the mitochondrial permeability transition (MPT), but not by the inhibitor of caspases, benzyloxycarbonyl-Val-Ala-Asp(Ome)-fluoromethylketone. disruption is associated with mitochondrial swelling and cytochrome c leakage. Using a reliable real-time flow cytometric monitoring of and swelling of mitochondria isolated from leukemia cells, we show that lamellarin D has a direct MPT-inducing effect. Furthermore, mitochondria are required in a cell-free system to mediate lamellarin D–induced nuclear apoptosis. The direct mitochondrial effect of lamellarin D accounts for the sensitivity of topoisomerase I–mutated P388CPT5 cells resistant to camptothecin. Interestingly, a tumor-active analogue of lamellarin D, designated PM031379, also exerts a direct proapoptotic action on mitochondria, with a more pronounced activity toward mitochondria of tumor cell lines compared with nontumor cell lines. Altogether, this work reinforces the pharmacologic interest of the lamellarins and defines lamellarin D as a lead in the search for treatments against chemoresistant cancer cells. (Cancer Res 2006; 66(6): 3177-87)