Mechanism of activation of caspase cascade during beta-carotene-induced apoptosis in human tumor cells.
In this study, we examined possible mechanisms of caspase activation during carotenoid-induced apoptosis in tumor cells. We found that beta-Carotene induces apoptosis by the activation of caspase-3 in human leukemia (HL-60), colon adenocarcinoma (HT-29) as well as melanoma (SK-MEL-2) cell lines. This activation is dose dependent and follows that of caspase-8 and caspase-9. Although caspase-8 cleavage is an early event, reaching its maximum activation at 3 h, caspase-9 reaches its maximum activation only at 6 h. The addition of IETD-CHO, a caspase-8-specific inhibitor, completely prevents beta-Carotene-induced apoptosis, whereas only a partial prevention was observed in the presence of LEHD-CHO, a caspase-9-specific inhibitor. beta-Carotene activates caspase-9 via cytochrome c release from mitochondria and loss of mitochondrial membrane potential (Dym). Concomitantly, a dose-dependent decrease in the antiapoptotic protein Bcl-2 and a dose-dependent increase in the cleaved form of BID (t-BID) are observed. Moreover, NF-kB activation is involved in beta-Carotene-induced caspase cascade. These results support a pharmacological role for beta-Carotene as a candidate antitumor agent and show a possible sequence of molecular events by which this molecule may induce apoptosis in tumor cells.
Palozza
Paola
P
Institute of General Pathology, Catholic University, Largo F. Vito 1, 00168 Rome, Italy. p.palozza@rm.unicatt.it
Serini
Simona
S
Torsello
Angela
A
Di Nicuolo
Fiorella
F
Maggiano
Nicola
N
Ranelletti
Franco O
FO
Wolf
Federica I
FI
Calviello
Gabriella
G
D000230:Adenocarcinoma / Q000473:pathology; D017209:Apoptosis / Q000187:drug effects*; D051023:BH3 Interacting Domain Death Agonist Protein; D002352:Carrier Proteins / Q000032:analysis; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases / Q000378:metabolism*; D003110:Colonic Neoplasms / Q000473:pathology; D045304:Cytochromes c / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D018922:HL-60 Cells / Q000473:pathology; D006801:Humans; D008545:Melanoma / Q000473:pathology; D008564:Membrane Potentials; D008928:Mitochondria / Q000378:metabolism / Q000648:ultrastructure; D016328:NF-kappa B / Q000502:physiology; D009369:Neoplasms / Q000473:pathology*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000032:analysis; D014407:Tumor Cells, Cultured; D019207:beta Carotene / Q000494:pharmacology*
D051023:BH3 Interacting Domain Death Agonist Protein; C494814:BID protein, human; D002352:Carrier Proteins; D004791:Enzyme Inhibitors; D016328:NF-kappa B; D019253:Proto-Oncogene Proteins c-bcl-2; D019207:beta Carotene; D045304:Cytochromes c; C505407:CASP3 protein, human; C505530:CASP8 protein, human; C506433:CASP9 protein, human; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases