title: miR-221 Mediates Chemoresistance of Esophageal Adenocarcinoma by Direct Targeting of DKK2 Expression.
abstract: BACKGROUND
  Chemoresistance is a main obstacle to effective esophageal cancer (EC) therapy. We hypothesize that altered expression of microRNAs (miRNAs) play a role in EC cancer progression and resistance to 5-fluorouracil (5-FU) based chemotherapeutic strategies.
  
  
  METHODS
  Four pairs of esophageal adenocarcinoma (EAC) cell lines and corresponding 5-FU resistant variants were established. The expression levels of miRNAs previously shown to be involved in the general regulation of stem cell pathways were analyzed by qRT-PCR. The effects of selected miRNAs on proliferation, apoptosis, and chemosensitivity were evaluated both in vitro and in vivo. We identified a particular miRNA and analyzed its putative target genes in 14 pairs of human EC tumor specimens with surrounding normal tissue by qRT-PCR as well as Wnt pathway associated genes by immunohistochemistry in another 45 EAC tumor samples.
  
  
  RESULTS
  MiR-221 was overexpressed in 5-FU resistant EC cell lines as well as in human EAC tissue. DKK2 was identified as a target gene for miR-221. Knockdown of miR-221 in 5-FU resistant cells resulted in reduced cell proliferation, increased apoptosis, restored chemosensitivity, and led to inactivation of the Wnt/β-catenin pathway mediated by alteration in DKK2 expression. Moreover, miR-221 reduction resulted in alteration of EMT-associated genes such as E-cadherin and vimentin as well as significantly slower xenograft tumor growth in nude mice. RT profiler analysis identified a substantial dysregulation of 4 Wnt/β-catenin signaling and chemoresistance target genes as a result of miR-221 modulation: CDH1, CD44, MYC, and ABCG2.
  
  
  CONCLUSIONS
  MiR-221 controls 5-FU resistance of EC partly via modulation of Wnt/β-catenin-EMT pathways by direct targeting of DKK2 expression. MiR-221 may serve as a prognostic marker and therapeutic target for patients with 5-FU resistant EAC.
authors: *Department of Surgery, University of Munich, Munich, Germany†Department of Surgery, Otto-von-Guericke University, Magdeburg, Germany‡Department of Medicine II, University of Munich, Munich, Germany§Department of Pathology, Otto-von-Guericke University, Magdeburg, Germany¶Department of Emergency, Guangdong Frontier Corps Hospital, Shenzhen, China||Clinical Biochemistry Group, Medizinische Klinik und Poliklinik IV, University of Munich, Munich, Germany**General, Visceral and Cancer Surgery, University Hospital of Cologne, Kerpener Straße 62, Cologne, Germany.
authors: Yan
authors: Y
authors: Wang
authors: Yue
authors: Y
authors: Zhao
authors: Andreas
authors: A
authors: Herbst
authors: Thomas
authors: T
authors: Kalinski
authors: Jiwei
authors: J
authors: Qin
authors: Xiaoyan
authors: X
authors: Wang
authors: Zhenzhong
authors: Z
authors: Jiang
authors: Frank
authors: F
authors: Benedix
authors: Sabine
authors: S
authors: Franke
authors: Thomas
authors: T
authors: Wartman
authors: Peter
authors: P
authors: Camaj
authors: Walter
authors: W
authors: Halangk
authors: Frank T
authors: FT
authors: Kolligs
authors: Karl W
authors: KW
authors: Jauch
authors: Peter J
authors: PJ
authors: Nelson
authors: Christiane J
authors: CJ
authors: Bruns
mesh_terms: D000230:Adenocarcinoma / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology; D000818:Animals; D000964:Antimetabolites, Antineoplastic / Q000627:therapeutic use*; D018929:Cell Culture Techniques; D004195:Disease Models, Animal; D019008:Drug Resistance, Neoplasm; D004938:Esophageal Neoplasms / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology; D005472:Fluorouracil / Q000627:therapeutic use*; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000502:physiology*; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D035683:MicroRNAs / Q000378:metabolism*
chemical_list: D000964:Antimetabolites, Antineoplastic; D005472:Fluorouracil; D036341:Intercellular Signaling Peptides and Proteins; D035683:MicroRNAs; C498622:DKK2 protein, human; C525709:MIR221, human