Induction of endonuclease G-mediated apopotosis in human oral squamous cell carcinoma cells by protein kinase C inhibitor safingol.
PKC inhibitor safingol suppressed the growth of human oral squamous cell carcinoma (SCC) cells significantly at concentrations that inhibit PKC isoforms. Safingol inhibited the translocation of PKC following treatment with 12-o-tetradecanoylphorbol 13-acetate (TPA) in PKC alpha-EGFP-transfected cells, but not in PKC beta-EGFP- transfected cells, indicating selective inhibition for PKC alpha in oral SCC cells. Flow cytometric analysis and DNA analysis by agarose gel electrophoresis revealed an increase in the proportion of sub-G(1) cells and DNA fragmentation in safingol-treated cells. Mitochondrial membrane potential was decreased, and cytochrome c was released from mitochondria. However, the safingol-induced cell death was not accompanied by activation of caspase 3 and cleavage of poly (ADP-ribose) polymerase (PARP). The broad-spectrum caspase inhibitor BD-fmk failed to prevent safingol-induced cell death. Another apoptogenic factor endonuclease G, but not apoptosis-inducing factor (AIF), was also released from mitochondria and translocated to the nucleus. These results suggest that PKC alpha inhibitor safingol induces an endonuclease G- mediated apoptosis in a caspase-independent manner.
Hamada
M
M
Department of Oral and Maxillofacial Surgery II, Osaka University Graduate School of Dentistry, Osaka, Japan.
Sumi
T
T
Iwai
S
S
Nakazawa
M
M
Yura
Y
Y
D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D051033:Apoptosis Inducing Factor / Q000378:metabolism; D001693:Biological Transport, Active / Q000187:drug effects; D002294:Carcinoma, Squamous Cell / Q000188:drug therapy* / Q000201:enzymology / Q000473:pathology; D020169:Caspases / Q000378:metabolism; D002453:Cell Cycle / Q000187:drug effects; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D004706:Endodeoxyribonucleases / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D009062:Mouth Neoplasms / Q000188:drug therapy* / Q000201:enzymology / Q000473:pathology; D000071137:Poly (ADP-Ribose) Polymerase-1; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000494:pharmacology; D014162:Transfection
C494829:AIFM1 protein, human; D051033:Apoptosis Inducing Factor; D004791:Enzyme Inhibitors; D011994:Recombinant Proteins; C485184:enhanced green fluorescent protein; D049452:Green Fluorescent Proteins; C499320:PARP1 protein, human; D000071137:Poly (ADP-Ribose) Polymerase-1; D011065:Poly(ADP-ribose) Polymerases; D011493:Protein Kinase C; D004706:Endodeoxyribonucleases; C052391:endonuclease G; D020169:Caspases; D013110:Sphingosine; C005682:safingol