title: Effect of thapsigargin on Ca²+ fluxes and viability in human prostate cancer cells.
abstract: Effect of the carcinogen thapsigargin on human prostate cancer cells is unclear. This study examined if thapsigargin altered basal [Ca²⁺](i) levels in suspended PC3 human prostate cancer cells by using fura-2 as a Ca²⁺-sensitive fluorescent probe. Thapsigargin at concentrations between 10 nM and 10 µM increased [Ca²⁺](i) in a concentration-dependent fashion. The Ca²⁺ signal was reduced partly by removing extracellular Ca²⁺ indicating that Ca²⁺ entry and release both contributed to the [Ca²⁺](i) rise. This Ca²⁺ influx was inhibited by suppression of phospholipase A2, but not by inhibition of store-operated Ca²⁺ channels or by modulation of protein kinase C activity. In Ca²⁺-free medium, pretreatment with the endoplasmic reticulum Ca²⁺ pump inhibitor 2,5-di-(t-butyl)-1,4-hydroquinone (BHQ) nearly abolished thapsigargin-induced Ca²⁺ release. Conversely, pretreatment with thapsigargin greatly reduced BHQ-induced [Ca²⁺](i) rise, suggesting that thapsigargin released Ca²⁺ from the endoplasmic reticulum. Inhibition of phospholipase C did not change thapsigargin-induced [Ca²⁺](i) rise. At concentrations of 1-10 µM, thapsigargin induced cell death that was partly reversed by chelation of Ca²⁺ with BAPTA/AM. Annexin V/propidium iodide staining data suggest that apoptosis was partly responsible for thapsigargin-induced cell death. Together, in PC3 human prostate cancer cells, thapsigargin induced [Ca²⁺](i) rises by causing phospholipase C-independent Ca²⁺ release from the endoplasmic reticulum and Ca²⁺ influx via phospholipase A2-sensitive Ca²⁺ channels. Thapsigargin also induced cell death via Ca²⁺-dependent pathways and Ca²⁺-independent apoptotic pathways.
authors.affiliation: Department of Surgery, Kaohsiung Veterans General Hospital, Kaohsiung, Taiwan 813.
authors.forename: Jong-Khing
authors.initials: JK
authors.lastname: Huang
authors.forename: Chiang-Ting
authors.initials: CT
authors.lastname: Chou
authors.forename: Hong-Tai
authors.initials: HT
authors.lastname: Chang
authors.forename: Su-Shung
authors.initials: SS
authors.lastname: Shu
authors.forename: Chun-Chi
authors.initials: CC
authors.lastname: Kuo
authors.forename: Jeng-Yu
authors.initials: JY
authors.lastname: Tsai
authors.forename: Wei-Chuan
authors.initials: WC
authors.lastname: Liao
authors.forename: Jue-Long
authors.initials: JL
authors.lastname: Wang
authors.forename: Ko-Long
authors.initials: KL
authors.lastname: Lin
authors.forename: Yi-Chau
authors.initials: YC
authors.lastname: Lu
authors.forename: I-Shu
authors.initials: IS
authors.lastname: Chen
authors.forename: Shuih-Inn
authors.initials: SI
authors.lastname: Liu
authors.forename: Chin-Man
authors.initials: CM
authors.lastname: Ho
authors.forename: Chung-Ren
authors.initials: CR
authors.lastname: Jan
mesh_terms: D017209:Apoptosis / Q000187:drug effects; D034341:Aristolochic Acids / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects*; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D004963:Estrenes / Q000494:pharmacology; D005453:Fluorescence; D016257:Fura-2 / Q000378:metabolism; D006801:Humans; D042541:Intracellular Space / Q000187:drug effects / Q000378:metabolism; D008297:Male; D008345:Manganese / Q000378:metabolism; D011471:Prostatic Neoplasms / Q000201:enzymology / Q000378:metabolism* / Q000473:pathology*; D011760:Pyrrolidinones / Q000494:pharmacology; D019284:Thapsigargin / Q000494:pharmacology*; D010738:Type C Phospholipases / Q000378:metabolism
chemical_list: D034341:Aristolochic Acids; D004963:Estrenes; D011760:Pyrrolidinones; C060229:1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione; D008345:Manganese; D019284:Thapsigargin; C000228:aristolochic acid I; D010738:Type C Phospholipases; D002118:Calcium; D016257:Fura-2