title: Inhibition of Orai1-mediated Ca2+entry enhances chemosensitivity of HepG2 hepatocarcinoma cells to 5-fluorouracil.
abstract: Increasing evidence supports that activation of store-operated Ca2+entry (SOCE) is implicated in the chemoresistance of cancer cells subjected to chemotherapy. However, the molecular mechanisms underlying chemoresistance are not well understood. In this study, we aim to investigate whether 5-FU induces hepatocarcinoma cell death through regulating Ca2+-dependent autophagy. [Ca2+]iwas measured using fura2/AM dye. Protein expression was determined by Western blotting and immunohistochemistry. We found that 5-fluorouracil (5-FU) induced autophagic cell death in HepG2 hepatocarcinoma cells by inhibiting PI3K/AKT/mTOR pathway. Orai1 expression was obviously elevated in hepatocarcinoma tissues. 5-FU treatment decreased SOCE and Orai1 expressions, but had no effects on Stim1 and TRPC1 expressions. Knockdown of Orai1 or pharmacological inhibition of SOCE enhanced 5-FU-induced inhibition of PI3K/AKT/mTOR pathway and potentiated 5-FU-activated autophagic cell death. On the contrary, ectopic overexpression of Orai1 antagonizes 5-FU-induced autophagy and cell death. Our findings provide convincing evidence to show that Orai1 expression is increased in hepatocarcinoma tissues. 5-FU can induce autophagic cell death in HepG2 hepatocarcinoma cells through inhibition of SOCE via decreasing Orai1 expression. These findings suggest that Orai1 expression is a predictor of 5-FU sensitivity for hepatocarcinoma treatment and blockade of Orai1-mediated Ca2+entry may be a promising strategy to sensitize hepatocarcinoma cells to 5-FU treatment.
authors.affiliation: Department of Gastroenterology, The First Affiliated Hospital, Sun Yat-Sen University, Guangzhou, China.
authors.forename: Bao-Dong
authors.initials: BD
authors.lastname: Tang
authors.affiliation: Department of Thoracic Surgery, The First Affiliated Hospital, Sun Yat-Sen University, Guangzhou, China.
authors.forename: Xin
authors.initials: X
authors.lastname: Xia
authors.affiliation: Department of Pharmacology, Cardiac and Cerebrovascular Research Center, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, China.
authors.forename: Xiao-Fei
authors.initials: XF
authors.lastname: Lv
authors.affiliation: Department of Pharmacology, Cardiac and Cerebrovascular Research Center, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, China.
authors.forename: Bei-Xin
authors.initials: BX
authors.lastname: Yu
authors.affiliation: Department of Pharmacology, Cardiac and Cerebrovascular Research Center, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, China.
authors.forename: Jia-Ni
authors.initials: JN
authors.lastname: Yuan
authors.affiliation: Department of Pharmacology, Cardiac and Cerebrovascular Research Center, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, China.
authors.forename: Xiao-Yi
authors.initials: XY
authors.lastname: Mai
authors.affiliation: Department of Pharmacology, Cardiac and Cerebrovascular Research Center, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, China.
authors.forename: Jin-Yan
authors.initials: JY
authors.lastname: Shang
authors.affiliation: Department of Pharmacology, Cardiac and Cerebrovascular Research Center, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, China.|Guangdong Province Key Laboratory of Brain Function and Disease, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, China.
authors.forename: Jia-Guo
authors.initials: JG
authors.lastname: Zhou
authors.affiliation: Department of Pharmacology, Cardiac and Cerebrovascular Research Center, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, China.
authors.forename: Si-Jia
authors.initials: SJ
authors.lastname: Liang
authors.affiliation: Guangdong Province Key Laboratory of Brain Function and Disease, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, China.|Department of Physiology, Pain Research Center, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, China.
authors.forename: Rui-Ping
authors.initials: RP
authors.lastname: Pang
mesh_terms: D000071182:Autophagosomes / Q000187:drug effects / Q000378:metabolism; D001343:Autophagy / Q000187:drug effects; D002118:Calcium / Q000378:metabolism*; D006528:Carcinoma, Hepatocellular / Q000378:metabolism* / Q000473:pathology; D015536:Down-Regulation / Q000187:drug effects; D005472:Fluorouracil / Q000494:pharmacology*; D056945:Hep G2 Cells; D006801:Humans; D008113:Liver Neoplasms / Q000378:metabolism* / Q000473:pathology; D000071740:ORAI1 Protein / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism
chemical_list: D002118:Calcium; D005472:Fluorouracil; D000071740:ORAI1 Protein; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; D058570:TOR Serine-Threonine Kinases; C510746:ORAI1 protein, human
keywords: 5-fluorouracil; Orai1; autophagy; chemosensitivity; store-operated Ca2+ entry