title: The Mechanism of Ca(2+) Movement in the Involvement of Baicalein-Induced Cytotoxicity in ZR-75-1 Human Breast Cancer Cells.
abstract: Baicalein (5,6,7-trihydroxyflavone) (1) has been found to be active against a wide variety of cancer cells. However, the molecular mechanism underlying the effects of 1 on the induction of Ca(2+) movement and cytotoxicity in human breast cancer cells is unknown. This study examined the relationship between 1-induced Ca(2+) signaling and cytotoxicity in ZR-75-1 human breast cancer cells. The in vitro investigations reported herein produced the following results: (i) Compound 1 increased intracellular Ca(2+) concentration ([Ca(2+)]i) in a concentration-dependent manner. The signal was decreased by approximately 50% by removal of extracellular Ca(2+). (ii) Compound 1-triggered [Ca(2+)]i increases were significantly suppressed by store-operated Ca(2+) channel blockers 2-aminoethoxydiphenyl borate (2-APB) and the PKC inhibitor GF109203X. (iii) In Ca(2+)-free medium, compound 1-induced [Ca(2+)]i increases were also inhibited by GF109203X. Furthermore, pretreatment with the endoplasmic reticulum Ca(2+) pump inhibitor thapsigargin (TG) or 2,5-ditert-butylhydroquinone (BHQ) abolished 1-induced [Ca(2+)]i increases. Inhibition of phospholipase C (PLC) with U73122 abolished 1-induced [Ca(2+)]i increases. (iv) Compound 1 (20-40 μM) caused cytotoxicity, increased reactive oxygen species (ROS) production, and activated caspase-9/caspase-3. Furthermore, compound 1-induced apoptosis was significantly inhibited by prechelating cytosolic Ca(2+) with BAPTA-AM (1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid acetoxymethyl ester) or by decreasing ROS with the antioxidant NAC (N-acetylcysteine). Together, baicalein (1) induced a [Ca(2+)]i increase by inducing PLC-dependent Ca(2+) release from the endoplasmic reticulum and Ca(2+) entry via PKC-dependent, 2-APB-sensitive store-operated Ca(2+) channels. Moreover, baicalein (1) induced Ca(2+)-associated apoptosis involved ROS production in ZR-75-1 cells.
authors.affiliation: †Department of Surgery, Kaohsiung Veterans General Hospital, Kaohsiung 813, Taiwan, Republic of China.
authors.forename: Hong-Tai
authors.initials: HT
authors.lastname: Chang
authors.affiliation: ‡Department of Nursing, Division of Basic Medical Sciences, Chang Gung University of Science and Technology, Chia-Yi 613, Taiwan, Republic of China.|§Chronic Diseases and Health Promotion Research Center, Chang Gung University of Science and Technology, Chia-Yi 613, Taiwan, Republic of China.
authors.forename: Chiang-Ting
authors.initials: CT
authors.lastname: Chou
authors.affiliation: ⊥Department of Pharmacy, Tajen University, Pingtung 907, Taiwan, Republic of China.
authors.forename: Daih-Huang
authors.initials: DH
authors.lastname: Kuo
authors.affiliation: ⊥Department of Pharmacy, Tajen University, Pingtung 907, Taiwan, Republic of China.
authors.forename: Pochuen
authors.initials: P
authors.lastname: Shieh
authors.affiliation: ∥Department of Medical Education and Research, Kaohsiung Veterans General Hospital, 386 Ta-Chung 1st Road, Kaohsiung 813, Taiwan, Republic of China.
authors.forename: Chung-Ren
authors.initials: CR
authors.lastname: Jan
authors.affiliation: ∥Department of Medical Education and Research, Kaohsiung Veterans General Hospital, 386 Ta-Chung 1st Road, Kaohsiung 813, Taiwan, Republic of China.
authors.forename: Wei-Zhe
authors.initials: WZ
authors.lastname: Liang
mesh_terms: D000111:Acetylcysteine / Q000494:pharmacology; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D001896:Boron Compounds; D001943:Breast Neoplasms; D002118:Calcium / Q000378:metabolism*; D053148:Caspase 3 / Q000378:metabolism; D053453:Caspase 9; D003600:Cytosol / Q000378:metabolism; D004533:Egtazic Acid / Q000031:analogs & derivatives; D004721:Endoplasmic Reticulum / Q000187:drug effects; D005260:Female; D044950:Flavanones / Q000494:pharmacology*; D006801:Humans; D007211:Indoles; D008301:Maleimides; D015394:Molecular Structure; D017382:Reactive Oxygen Species / Q000494:pharmacology; D019284:Thapsigargin / Q000494:pharmacology; D010738:Type C Phospholipases
chemical_list: D001896:Boron Compounds; D044950:Flavanones; D007211:Indoles; D008301:Maleimides; D017382:Reactive Oxygen Species; C070379:1,2-bis(2-aminophenoxy)ethane N,N,N',N'-tetraacetic acid acetoxymethyl ester; C006680:baicalein; D004533:Egtazic Acid; D019284:Thapsigargin; C109986:2-aminoethoxydiphenyl borate; D010738:Type C Phospholipases; D053148:Caspase 3; D053453:Caspase 9; C025603:1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid; C070515:bisindolylmaleimide I; D002118:Calcium; D000111:Acetylcysteine