title: [Effects of stable up-regulation of tight junction protein claudin-6 upon biological phenotypes of breast cancer cell MCF-7].
abstract: OBJECTIVE
  To explore the effect of over-expression of tight junction protein claudin-6 upon the biological characters of breast cancer cell line MCF-7.
  
  
  METHODS
  The MCF-7 subline expressing a high level of claudin-6 was established by transfection with a pcDNA3.1-claudin-6 expression vector. The expression of claudin-6 in mRNA and its protein level were confirmed by RT-PCR, Western blot and immunofluorescent assays. Then the effect of claudin-6 upon cell proliferation was examined by MTT assay. Colony-forming assays were used to examine 2-D and 3-D colony-forming capacities. Invasive and migratory traits of claudin-6 expressing cells were determined by Boyden chamber invasion assay and monolayer wound-healing assay. The structure and function of tight junctions in both parental and claudin-6 expression MCF-7 cells were evaluated by measuring transepithelial electrical resistance.
  
  
  RESULTS
  Immunofluorescent assays showed that transfected cells expressed claudin-6 on their membrane. Cells with a high level expression of claudin-6 grew slowly than control cells. Anchorage-independent growth, invasive and migratory traits also decreased substantially in cells with claudin-6 expression; whereas the transepithelial electrical resistance increased in the claudin-6 transfected cells.
  
  
  CONCLUSIONS
  The up-regulation of claudin-6 expression in MCF-7 breast cancer cells suppresses their malignant phenotypes with a correlation with the restoration of tight junction integrity. Claudin-6 may function as a cancer suppressor whose down-regulation contributes to the malignant progression of certain types of breast cancers.
authors.affiliation: Key laboratory of Pathobiology, Ministry of Education, Jilin University, Changchun 130021, China.
authors.forename: Qiong
authors.initials: Q
authors.lastname: Wu
authors.forename: Ya-fang
authors.initials: YF
authors.lastname: Liu
authors.forename: Yue
authors.initials: Y
authors.lastname: Ren
authors.forename: Xiao-ming
authors.initials: XM
authors.lastname: Xu
authors.forename: Li-na
authors.initials: LN
authors.lastname: Yu
authors.forename: Yu-lin
authors.initials: YL
authors.lastname: Li
authors.forename: Cheng-shi
authors.initials: CS
authors.lastname: Quan
mesh_terms: D001943:Breast Neoplasms / Q000378:metabolism* / Q000473:pathology; D045744:Cell Line, Tumor; D057167:Claudins; D015536:Down-Regulation; D005260:Female; D006801:Humans; D008565:Membrane Proteins / Q000378:metabolism*; D009361:Neoplasm Invasiveness; D019108:Tight Junctions / Q000378:metabolism* / Q000473:pathology; D014162:Transfection
chemical_list: D057167:Claudins; D008565:Membrane Proteins; C122101:claudin 6