12-lipoxygenase induces apoptosis of human gastric cancer AGS cells via the ERK1/2 signal pathway.
12-Lipoxygenase (12-LOX) is over-expressed in a variety of human tumors, but its exact effect on the tumorogenesis of gastric cancer remains largely obscure. To investigate the effect of 12-LOX and its inhibitor baicalein on proliferation and apoptosis of human gastric cancer, AGS cells were separately treated with 12-hydroxyeicosatetraenoic acid (12-HETE, a metabolite of 12-LOX) and baicalein. MTT assay revealed that the absorbance of the 12-HETE-treated group was significantly (P < 0.01) higher than that of control group and that the absorbance of baicalein-treated group was significantly (P < 0.01) less than that of the control group, and that 48 h after treatment the apoptosis index of the baicalein-treated group was significantly (P < 0.01) higher than that of the untreated group and was significantly (P < 0.01) lower in the 12-HETE-treated group. Western blotting analysis was used to investigate the mechanism of these effects. The results revealed that the concentration of phosphorylated ERK in cells treated with 100 nmol L(-1) 12-HETE was significantly (P < 0.05) higher than in the untreated group and that the concentration of phosphorylated ERK1/2 in cells treated with 40 micromol L(-1) baicalein was significantly (P < 0.05) lower than in the untreated group. The expression level of bcl-2 was up-regulated and down-regulated after separate treatment with 12-HETE and baicalein, respectively, and both of these effects could be blocked by PD98059. Protein kinase C (PKC) activity was increased by treatment with 12-HETE and reduced by treatment with baicalein (P < 0.05). The PKC inhibitor BIM (bisindolymaleimide-I) blocked the phosphorylation of ERK1/2 and activation of PKC induced by 12-LOX. When pretreated with BIM, the concentration of phospho-ERK1/2 or bcl-2 in the BIM + 12-HETE-treated group was significantly (P < 0.05) lower than in that treated with 12-HETE only, and the concentration in the BIM + baicalein-treated group was significantly (P < 0.05) higher than in that treated with baicalein only. On the basis of these data we conclude that, via its metabolite 12-HETE, 12-LOX abolishes proliferation of AGS cells and protect cells from apoptosis by activating the ERK1/2 pathway and, eventually, enhances expression of bcl-2. Because PKC is also involved in the activation of ERK1/2 induced by 12-LOX, 12-LOX inhibitors would be potentially powerful anticancer agents for prevention and cure of human gastric cancer.
Chen
Feng-Lin
FL
Department of Gastroenterology, Renmin Hospital of Wuhan University, Wuhan, Hubei Province, PR China. drchenfl@163.com
Wang
Xiao-Zhong
XZ
Li
Jian-Ying
JY
Yu
Jie-Ping
JP
Huang
Cai-Yun
CY
Chen
Zhi-Xin
ZX
D019377:12-Hydroxy-5,8,10,14-eicosatetraenoic Acid / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D001092:Arachidonate 12-Lipoxygenase / Q000096:biosynthesis*; D014408:Biomarkers, Tumor; D015153:Blotting, Western; D049109:Cell Proliferation / Q000187:drug effects; D004250:DNA Topoisomerases, Type II; D004587:Electrophoresis, Agar Gel; D004791:Enzyme Inhibitors / Q000494:pharmacology; D044950:Flavanones / Q000494:pharmacology; D006801:Humans; D016859:Lipoxygenase Inhibitors; D048052:Mitogen-Activated Protein Kinase 3 / Q000037:antagonists & inhibitors / Q000096:biosynthesis*; D010766:Phosphorylation; D015398:Signal Transduction / Q000502:physiology*; D013274:Stomach Neoplasms / Q000188:drug therapy / Q000201:enzymology* / Q000473:pathology; D014407:Tumor Cells, Cultured
D014408:Biomarkers, Tumor; D004791:Enzyme Inhibitors; D044950:Flavanones; D016859:Lipoxygenase Inhibitors; C006680:baicalein; D019377:12-Hydroxy-5,8,10,14-eicosatetraenoic Acid; D001092:Arachidonate 12-Lipoxygenase; D048052:Mitogen-Activated Protein Kinase 3; D004250:DNA Topoisomerases, Type II