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Inhibition of 12-lipoxygenase reduces proliferation and induces apoptosis of hepatocellular carcinoma cells in vitro and in vivo |
Xi-Ming Xu, Guang-Jin Yuan, Jun-Jian Deng, Hong-Ting Guo, Miao Xiang, Fang Yang, Wei Ge and Shi-You Chen |
Wuhan, China
Author Affiliations: Cancer Center, Renmin Hospital of Wuhan University, Wuhan 430060, China (Xu XM, Deng JJ, Guo HT, Xiang M and Ge W); Cancer Center, the 82nd Hospital of the Chinese PLA, Huai an 223001, China (Yuan GJ); Department of Physiology, Medical College of Wuhan University, Wuhan 430071, China (Yang F); Department of Physiology & Pharmacology, University of Georgia, Athens, GA 30602, USA (Chen SY)
Corresponding Author: Xi-Ming Xu, MD, PhD, Cancer Center, Renmin Hospital of Wuhan University, Wuhan 430060, China (Tel: 86-27-88041911; Fax: 86-27-88042292; Email: whuxxm@yahoo.com) |
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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.
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