title: Tamoxifen inhibits migration of estrogen receptor-negative hepatocellular carcinoma cells by blocking the swelling-activated chloride current.
abstract: Tamoxifen is a triphenylethylene non-steroidal antiestrogen anticancer agent. It also shows inhibitory effects on metastasis of estrogen receptor (EsR)-independent tumors, but the underlying mechanism is unclear. It was demonstrated in this study that, in EsR-negative and highly metastatic human hepatocellular carcinoma MHCC97H cells, tamoxifen-inhibited cell migration, volume-activated Cl(-) currents (I(Cl,vol)) and regulatory volume decrease (RVD) in a concentration-dependent manner with a similar IC(50). Analysis of the relationships between migration, I(Cl,vol) and RVD showed that cell migration was positively correlated with I(Cl,vol) and RVD. Knockdown of the expression of ClC-3 Cl(-) channel proteins by ClC-3 shRNA or siRNA inhibited I(Cl,vol), and cell migration, and these inhibitory effects could not be increased further by addition of tamoxifen in the medium. The results suggest that knockdown of ClC-3 expression may deplete the effects of tamoxifen; tamoxifen may inhibit cell migration by modulating I(Cl,vol) and cell volume. Moreover, tamoxifen decreased the activity of protein kinase C (PKC) and the effects were reversed by the PKC activator PMA. Activation of PKC by PMA could competitively downregulate the inhibitory effects of tamoxifen on I(Cl,vol). PMA promoted cell migration, and knockdown of ClC-3 expression by ClC-3 siRNA abolished the PMA effect on cell migration. The results suggest that tamoxifen may inhibit I(Cl,vol) by suppressing PKC activation; I(Cl,vol) may be an EsR-independent target for tamoxifen in the anti-metastatic action on cancers, especially on EsR-negative cancers. The finding may have an implication in the clinical use of tamoxifen in the treatments of both EsR-positive and EsR-negative cancers.
authors.affiliation: Department of Pharmacology and Department of Physiology, Medical College, Jinan University, Guangzhou, China.
authors.forename: Jianwen
authors.initials: J
authors.lastname: Mao
authors.forename: Jian
authors.initials: J
authors.lastname: Yuan
authors.forename: Liwei
authors.initials: L
authors.lastname: Wang
authors.forename: Haifeng
authors.initials: H
authors.lastname: Zhang
authors.forename: Xiaobao
authors.initials: X
authors.lastname: Jin
authors.forename: Jiayong
authors.initials: J
authors.lastname: Zhu
authors.forename: Hongzhi
authors.initials: H
authors.lastname: Li
authors.forename: Bin
authors.initials: B
authors.lastname: Xu
authors.forename: Lixin
authors.initials: L
authors.lastname: Chen
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology; D006528:Carcinoma, Hepatocellular / Q000188:drug therapy / Q000378:metabolism*; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000187:drug effects*; D048429:Cell Size / Q000187:drug effects; D018118:Chloride Channels / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D008113:Liver Neoplasms / Q000188:drug therapy / Q000378:metabolism*; D009362:Neoplasm Metastasis; D034741:RNA, Small Interfering; D011960:Receptors, Estrogen / Q000378:metabolism; D013629:Tamoxifen / Q000494:pharmacology*; D013755:Tetradecanoylphorbol Acetate / Q000031:analogs & derivatives / Q000494:pharmacology
chemical_list: D000970:Antineoplastic Agents; D018118:Chloride Channels; C115376:ClC-3 channel; D034741:RNA, Small Interfering; D011960:Receptors, Estrogen; D013629:Tamoxifen; C016658:phorbolol myristate acetate; D013755:Tetradecanoylphorbol Acetate