Enhancement of susceptibility to Fas-mediated apoptosis in HL-60 cells through down-regulation of cellular FLICE-inhibitory protein by phosphatidylinositol 3-kinase inhibitors.
Promyelocytic leukemia HL-60 cells are resistant to Fas-mediated apoptosis. The signaling pathway for Fas-mediated apoptosis in various cells, including HL-60 cells, is currently unknown. Here, we studied the role of survival/apoptosis associated phosphatidylinositol 3-kinase (PI 3-K)/Akt in this process. We found that both PI 3-K inhibitors, wortmannin and LY294002, markedly suppressed phosphorylation of Akt and Bad in HL-60 cells. PI 3-K inhibitors significantly accelerated not only spontaneous apoptosis, but also Fas-induced apoptosis in HL-60 cells. The pro-apoptotic effect of PI 3-K inhibitors favored Fas-mediated apoptosis rather than spontaneous apoptosis in HL-60 cells. The caspase-3 or -8 inhibitor reduced the pro-apoptotic effect of the PI 3-K inhibitors for Fas-mediated apoptosis in HL-60 cells, but the caspase-9 inhibitor did not. Although PI 3-K inhibitors did not affect Fas expression in HL-60 cells, cellular FLICE-inhibitory protein (c-FLIP) levels were markedly reduced by PI 3-K inhibitor treatment. Furthermore, antisense oligonucleotide of c-FLIP confirmed that down-regulation of c-FLIP enhanced sensitization to Fas-mediated apoptosis in HL-60 cells. These results suggest that the PI 3-K/Akt signaling pathway may, in part, regulate Fas-mediated apoptosis in HL-60 cells through c-FLIP expression.
Kondo
Gen
G
Department of Oral and Maxillofacial Surgery, Showa University School of Dentistry, 2-1-1 Kitasenzoku, Ota-ku, Tokyo 145-8515, Japan.
Iwase
Masayasu
M
Watanabe
Hitoshi
H
Uchida
Makiko
M
Takaoka
Sayaka
S
Ohashi
Masaru
M
Ito
Daisuke
D
Nagumo
Masao
M
D017209:Apoptosis / Q000235:genetics* / Q000502:physiology; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; D061945:Caspase Inhibitors; D002470:Cell Survival; D015536:Down-Regulation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D018922:HL-60 Cells; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics* / Q000502:physiology*; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D017346:Protein Serine-Threonine Kinases / Q000502:physiology; D011518:Proto-Oncogene Proteins / Q000502:physiology; D051057:Proto-Oncogene Proteins c-akt; D015398:Signal Transduction; D019014:fas Receptor / Q000502:physiology
D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; D061945:Caspase Inhibitors; D004791:Enzyme Inhibitors; D047908:Intracellular Signaling Peptides and Proteins; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D019014:fas Receptor; C506386:CFLAR protein, human; C494918:AKT1 protein, human