title: Inhibition of 12-lipoxygenase reduces proliferation and induces apoptosis of hepatocellular carcinoma cells in vitro and in vivo.
abstract: BACKGROUND
  12-lipoxygenase (12-LOX) has been reported to be an important gene in cancer cell proliferation and survival, and tumor metastasis. However, its role in hepatocellular carcinoma (HCC) cells remains unknown.
  
  
  METHODS
  Expression of 12-LOX was assessed in a diethyl-nitrosamine-induced rat HCC model, and in SMMC-7721, HepG2 and L-02 cells using immunohistochemical staining and reverse transcriptase-polymerase chain reaction (RT-PCR). GST-π and Ki-67 were determined in vivo by immunohistochemical staining. Apoptosis was evaluated by TUNEL assay. Cell viability and apoptosis were determined by MTT assay and flow cytometry, respectively. Apoptosis-related proteins in SMMC-7721 and HepG2 cells were detected by Western blotting.
  
  
  RESULTS
  Immunohistochemical staining and RT-PCR showed that 12-LOX was over-expressed in rat HCC and two HCC cell lines, while the expression was inhibited by baicalein, a specific inhibitor of 12-LOX. Baicalein inhibited cell proliferation and induced apoptosis in rat HCC and both cell lines in a dose- and time-dependent manner. Our in vivo study demonstrated that baicalein also reduced neoplastic nodules. Mechanistically, baicalein reduced Bcl-2 protein expression coupled with a slight increase of the expression of Bax and activation of caspase-3. Furthermore, baicalein inhibited the activation of ERK-1/2 (phosphorylated). Interestingly, the effects of baicalein were reversed by 12(S)-HETE, a metabolite of 12-LOX.
  
  
  CONCLUSIONS
  Inhibition of 12-LOX leads to reduced numbers of HCC cells, partially caused by increased apoptosis. 12-LOX may be a potential molecular target for HCC prevention and treatment.
authors.affiliation: Cancer Center, Renmin Hospital of Wuhan University, Wuhan 430060, China. whuxxm@yahoo.com
authors.forename: Xi-Ming
authors.initials: XM
authors.lastname: Xu
authors.forename: Guang-Jin
authors.initials: GJ
authors.lastname: Yuan
authors.forename: Jun-Jian
authors.initials: JJ
authors.lastname: Deng
authors.forename: Hong-Ting
authors.initials: HT
authors.lastname: Guo
authors.forename: Miao
authors.initials: M
authors.lastname: Xiang
authors.forename: Fang
authors.initials: F
authors.lastname: Yang
authors.forename: Wei
authors.initials: W
authors.lastname: Ge
authors.forename: Shi-You
authors.initials: SY
authors.lastname: Chen
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D001092:Arachidonate 12-Lipoxygenase / Q000187:drug effects* / Q000378:metabolism; D006528:Carcinoma, Hepatocellular / Q000378:metabolism / Q000473:pathology*; D053148:Caspase 3 / Q000378:metabolism; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects*; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D044950:Flavanones / Q000494:pharmacology*; D006801:Humans; D066298:In Vitro Techniques; D016859:Lipoxygenase Inhibitors / Q000494:pharmacology*; D008113:Liver Neoplasms / Q000378:metabolism / Q000473:pathology*; D008297:Male; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors; D051028:bcl-2-Associated X Protein / Q000378:metabolism
chemical_list: D044950:Flavanones; D016859:Lipoxygenase Inhibitors; D019253:Proto-Oncogene Proteins c-bcl-2; D051028:bcl-2-Associated X Protein; C006680:baicalein; D001092:Arachidonate 12-Lipoxygenase; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D053148:Caspase 3