Calcium is a key signaling molecule in beta-lapachone-mediated cell death.
beta-Lapachone (beta-Lap) triggers apoptosis in a number of human breast and prostate cancer cell lines through a unique apoptotic pathway that is dependent upon NQO1, a two-electron reductase. Downstream signaling pathway(s) that initiate apoptosis following treatment with beta-Lap have not been elucidated. Since calpain activation was suspected in beta-Lap-mediated apoptosis, we examined alterations in Ca(2+) homeostasis using NQO1-expressing MCF-7 cells. beta-Lap-exposed MCF-7 cells exhibited an early increase in intracellular cytosolic Ca(2+), from endoplasmic reticulum Ca(2+) stores, comparable to thapsigargin exposures. 1,2-Bis-(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid-acetoxymethyl ester, an intracellular Ca(2+) chelator, blocked early increases in Ca(2+) levels and inhibited beta-Lap-mediated mitochondrial membrane depolarization, intracellular ATP depletion, specific and unique substrate proteolysis, and apoptosis. The extracellular Ca(2+) chelator, EGTA, inhibited later apoptotic end points (observed >8 h, e.g. substrate proteolysis and DNA fragmentation), suggesting that later execution events were triggered by Ca(2+) influxes from the extracellular milieu. Collectively, these data suggest a critical, but not sole, role for Ca(2+) in the NQO1-dependent cell death pathway initiated by beta-Lap. Use of beta-Lap to trigger an apparently novel, calpain-like-mediated apoptotic cell death could be useful for breast and prostate cancer therapy.
Departments of Radiation Oncology and Pharmacology, Department of Anatomy, Case Western Reserve University, Cleveland, Ohio 44106-4942, USA.
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C
Tagliarino
J J
JJ
Pink
G R
GR
Dubyak
A L
AL
Nieminen
D A
DA
Boothman
D015112:4-Nitroquinoline-1-oxide / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000378:metabolism; D017209:Apoptosis; D015153:Blotting, Western; D001943:Breast Neoplasms / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D016923:Cell Death; D002455:Cell Division; D002614:Chelating Agents / Q000494:pharmacology; D003600:Cytosol / Q000378:metabolism; D053938:DNA Fragmentation; D004305:Dose-Response Relationship, Drug; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D004721:Endoplasmic Reticulum / Q000378:metabolism; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D020287:In Situ Nick-End Labeling; D008297:Male; D008564:Membrane Potentials; D018613:Microscopy, Confocal; D008928:Mitochondria / Q000378:metabolism; D008954:Models, Biological; D009285:Naphthoquinones / Q000378:metabolism* / Q000494:pharmacology; D011471:Prostatic Neoplasms / Q000378:metabolism; D015363:Quinolones / Q000494:pharmacology; D015398:Signal Transduction; D013997:Time Factors; D014407:Tumor Cells, Cultured
C120195:4-nitroquinolone-1-oxide; D002614:Chelating Agents; D009285:Naphthoquinones; D015363:Quinolones; C070379:1,2-bis(2-aminophenoxy)ethane N,N,N',N'-tetraacetic acid acetoxymethyl ester; D004533:Egtazic Acid; D015112:4-Nitroquinoline-1-oxide; C014638:beta-lapachone; D000255:Adenosine Triphosphate; D002118:Calcium