title: Licochalcone A induces apoptosis through endoplasmic reticulum stress via a phospholipase Cγ1-, Ca(2+)-, and reactive oxygen species-dependent pathway in HepG2 human hepatocellular carcinoma cells.
abstract: Licochalcone A (LicA), an estrogenic flavonoid, induces apoptosis in multiple types of cancer cells. In this study, the molecular mechanisms underlying the anti-cancer effects of LicA were investigated in HepG2 human hepatocellular carcinoma cells. LicA induced apoptotic cell death, activation of caspase-4, -9, and -3, and expression of endoplasmic reticulum (ER) stress-associated proteins, including C/EBP homologous protein (CHOP). Inhibition of ER stress by CHOP knockdown or treatment with the ER stress inhibitors, salubrinal and 4-phenylbutyric acid, reduced LicA-induced cell death. LicA also induced reactive oxygen species (ROS) accumulation and the anti-oxidant N-acetylcysteine reduced LicA-induced cell death and CHOP expression. In addition, LicA increased the levels of cytosolic Ca(2+), which was blocked by 2-aminoethoxydiphenyl borate (an antagonist of inositol 1,4,5-trisphosphate receptor) and BAPTA-AM (an intracellular Ca(2+) chelator). 2-Aminoethoxydiphenyl borate and BAPTA-AM inhibited LicA-induced cell death. Interestingly, LicA induced phosphorylation of phospholipase Cγ1 (PLCγ1) and inhibition of PLCγ1 reduced cell death and ER stress. Moreover, the multi-targeted receptor tyrosine kinase inhibitors, sorafenib and sunitinib, reduced LicA-induced cell death, ER stress, and cytosolic Ca(2+) and ROS accumulation. Finally, LicA induced phosphorylation of vascular endothelial growth factor receptor 2 (VEGFR2) and c-Met receptor and inhibition of both receptors by co-transfection with VEGFR2 and c-Met siRNAs reversed LicA-induced cell death, Ca(2+) increase, and CHOP expression. Taken together, these findings suggest that induction of ER stress via a PLCγ1-, Ca(2+)-, and ROS-dependent pathway may be an important mechanism by which LicA induces apoptosis in HepG2 hepatocellular carcinoma cells.
authors: Department of Biochemistry and Molecular Biology, School of Medicine, Medical Research Center for Bioreaction to Reactive Oxygen Species, Biomedical Science Institute, Kyung Hee University, Seoul, 130-701, Republic of Korea.
authors: A-Young
authors: AY
authors: Choi
authors: Ji Hyun
authors: JH
authors: Choi
authors: Keun-Young
authors: KY
authors: Hwang
authors: Yeon Ju
authors: YJ
authors: Jeong
authors: Wonchae
authors: W
authors: Choe
authors: Kyung-Sik
authors: KS
authors: Yoon
authors: Joohun
authors: J
authors: Ha
authors: Sung Soo
authors: SS
authors: Kim
authors: Jang Hyun
authors: JH
authors: Youn
authors: Eui-Ju
authors: EJ
authors: Yeo
authors: Insug
authors: I
authors: Kang
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D002118:Calcium / Q000378:metabolism*; D020169:Caspases / Q000378:metabolism; D002460:Cell Line; D047188:Chalcones / Q000494:pharmacology*; D059865:Endoplasmic Reticulum Stress / Q000187:drug effects*; D006360:Heat-Shock Proteins / Q000378:metabolism; D056945:Hep G2 Cells; D006801:Humans; D051966:Phospholipase C gamma / Q000378:metabolism*; D017382:Reactive Oxygen Species / Q000378:metabolism*; D020794:Receptor Protein-Tyrosine Kinases / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects*; D040301:Vascular Endothelial Growth Factor Receptor-2
chemical_list: D000970:Antineoplastic Agents; D047188:Chalcones; D006360:Heat-Shock Proteins; D017382:Reactive Oxygen Species; C000588866:KDR protein, human; C080835:RON protein; D020794:Receptor Protein-Tyrosine Kinases; D040301:Vascular Endothelial Growth Factor Receptor-2; D051966:Phospholipase C gamma; D020169:Caspases; C070840:licochalcone A; D002118:Calcium