Inhibition of 12-lipoxygenase reduces proliferation and induces apoptosis of hepatocellular carcinoma cells in vitro and in vivo

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 diethylnitrosamine-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.