Essential role of mitochondria in apoptosis of cancer cells induced by the marine alkaloid Lamellarin D.
Lamellarin D, a potent cytotoxic marine alkaloid, exerts its antitumor action through two complementary pathways: a nuclear route via topoisomerase I inhibition and a mitochondrial targeting. The present study was designed to investigate the contribution of these two pathways for apoptosis in cancer cells. Lamellarin D promoted nuclear apoptosis in leukemia cells without prominent cell cycle arrest. Signals transmitted by lamellarin D initiated apoptosis via the intrinsic apoptotic pathway. The drug induced conformational activation of Bax and decreased the expression levels of antiapoptotic proteins Bcl-2 and cIAP2 in association with activation of caspase-9 and caspase-3. Upon lamellarin D exposure, Fas and Fas-L expression was not modified in leukemia cells. Moreover, leukemia cells deficient in caspase-8 or Fas-associated protein with death domain underwent apoptosis through the typical mitochondrial apoptotic cascade, indicating that cell death induced by lamellarin D was independent of the extrinsic apoptotic pathway. Lamellarin D also exerted a topoisomerase I-mediated DNA damage response resulting in H2AX phosphorylation, and the upregulation of the DNA repair protein Rad51 and of p53, as well as the phosphorylation of p53 at serine 15. However, lamellarin D killed efficiently mutated p53 or p53 null cancer cells, and sensitivity to lamellarin D was abrogated neither by cycloheximide nor in enucleated cells. Lamellarin D-induced cytochrome c release occurs independently of nuclear factors in a cell-free system. These results suggest that lamellarin D exerts its cytotoxic effects primarily by inducing mitochondrial apoptosis independently of nuclear signaling. Thus, lamellarin D constitutes a new proapoptotic agent that may bypass certain forms of apoptosis resistance that occur in tumor cells.
Ballot
Caroline
C
INSERM U 837 Faculté de médecine, 1, place Verdun F- 59045 Lille Cedex France.
Kluza
Jérome
J
Martoriati
Alain
A
Nyman
Ulrika
U
Formstecher
Pierre
P
Joseph
Bertrand
B
Bailly
Christian
C
Marchetti
Philippe
P
D000818:Animals; D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D000075747:Baculoviral IAP Repeat-Containing 3 Protein; D053148:Caspase 3 / Q000378:metabolism; D053453:Caspase 9 / Q000378:metabolism; D002453:Cell Cycle / Q000187:drug effects; D045744:Cell Line, Tumor; D003374:Coumarins / Q000494:pharmacology*; D004249:DNA Damage; D004264:DNA Topoisomerases, Type I / Q000378:metabolism; D005434:Flow Cytometry; D045325:HCT116 Cells; D006576:Heterocyclic Compounds, 4 or More Rings / Q000494:pharmacology*; D006657:Histones / Q000378:metabolism; D006801:Humans; D015151:Immunoblotting; D051034:Inhibitor of Apoptosis Proteins / Q000378:metabolism; D007546:Isoquinolines / Q000494:pharmacology*; D019169:Jurkat Cells; D008856:Microscopy, Fluorescence; D008928:Mitochondria / Q000378:metabolism*; D009154:Mutation; D009369:Neoplasms / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology; D010766:Phosphorylation / Q000187:drug effects; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases; D051028:bcl-2-Associated X Protein / Q000378:metabolism
D003374:Coumarins; C468783:H2AX protein, human; D006576:Heterocyclic Compounds, 4 or More Rings; D006657:Histones; D051034:Inhibitor of Apoptosis Proteins; D007546:Isoquinolines; D019253:Proto-Oncogene Proteins c-bcl-2; D016159:Tumor Suppressor Protein p53; D051028:bcl-2-Associated X Protein; C455554:lamellarin D; C494832:BIRC3 protein, human; D000075747:Baculoviral IAP Repeat-Containing 3 Protein; D044767:Ubiquitin-Protein Ligases; D053148:Caspase 3; D053453:Caspase 9; D004264:DNA Topoisomerases, Type I