Caspase-8 preferentially senses the apoptosis-inducing action of NG-18, a Gambogic acid derivative, in human leukemia HL-60 cells.
Gambogic acid (GA) is the major active ingredient of gamboge secreted from a Chinese traditional medicine Garcinia hanburryi possessing potent anti-tumor activity. N-(2-ethoxyethyl)gambogamide (NG-18), a derivative of GA, also efficiently inhibits proliferation of cultured human tumor cells. The inhibition effect of NG-18 is associated with its ability to induce apoptosis. In the present study, NG-18 markedly induced leukemia HL-60 cells apoptosis, and the extrinsic and intrinsic apoptosis pathways were activated almost at the same time. NG-18-induced tumor cell apoptosis was associated with up-regulation of pro-apoptotic Bcl-2 family member Bax, and downregulation of anti-apoptotic protein Bcl-2. The NG-18-induced apoptosis was blocked completely by a pan-caspase inhibitor Z-VAD-FMK, indicating that caspases were functionally and actively involved in this process. The specific inhibition of caspase-8 activity using Z-IETD-FMK significantly blocked NG-18-induced apoptosis. In contrast, inhibition of other initiator caspases, caspase-2 or -9, using Z-VDVAD-FMK or Z-LEHD-FMK respectively had no effect on NG-18-induced apoptosis. Altogether, our data demonstrated that NG-18-induced apoptosis was dependent on caspases and caspase-8 acted as a key executor in the event.
Tao
Zhijian
Z
College of Chemistry and Life, Zhejiang Normal University, Jinhua Zhejiang, PR China.
Zhou
Yunlong
Y
Lu
Jinjian
J
Duan
Wenhu
W
Qin
Yuxin
Y
He
Xinxia
X
Lin
Liping
L
Ding
Jian
J
D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D015153:Blotting, Western; D053181:Caspase 8 / Q000378:metabolism*; D049109:Cell Proliferation / Q000187:drug effects*; D045304:Cytochromes c / Q000378:metabolism; D004365:Drugs, Chinese Herbal / Q000494:pharmacology*; D005434:Flow Cytometry; D029760:Garcinia / Q000737:chemistry*; D018922:HL-60 Cells / Q000187:drug effects / Q000201:enzymology / Q000473:pathology; D006801:Humans; D015394:Molecular Structure; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D044004:Xanthones / Q000737:chemistry / Q000494:pharmacology*; D051020:bcl-X Protein / Q000378:metabolism
D000970:Antineoplastic Agents; D004365:Drugs, Chinese Herbal; C526872:N-(2-ethoxyethyl)gambogamide; D019253:Proto-Oncogene Proteins c-bcl-2; D044004:Xanthones; D051020:bcl-X Protein; D045304:Cytochromes c; D011065:Poly(ADP-ribose) Polymerases; D053181:Caspase 8