title: Impact of MUC1 mucin downregulation in the phenotypic characteristics of MKN45 gastric carcinoma cell line.
abstract: BACKGROUND
  Gastric carcinoma is the second leading cause of cancer-associated death worldwide. The high mortality associated with this disease is in part due to limited knowledge about gastric carcinogenesis and a lack of available therapeutic and prevention strategies. MUC1 is a high molecular weight transmembrane mucin protein expressed at the apical surface of most glandular epithelial cells and a major component of the mucus layer above gastric mucosa. Overexpression of MUC1 is found in approximately 95% of human adenocarcinomas, where it is associated with oncogenic activity. The role of MUC1 in gastric cancer progression remains to be clarified.
  
  
  METHODS
  We downregulated MUC1 expression in a gastric carcinoma cell line by RNA interference and studied the effects on cellular proliferation (MTT assay), apoptosis (TUNEL assay), migration (migration assay), invasion (invasion assay) and aggregation (aggregation assay). Global gene expression was evaluated by microarray analysis to identify alterations that are regulated by MUC1 expression. In vivo assays were also performed in mice, in order to study the tumorigenicity of cells with and without MUC1 downregulation in MKN45 gastric carcinoma cell line.
  
  
  RESULTS
  Downregulation of MUC1 expression increased proliferation and apoptosis as compared to controls, whereas cell-cell aggregation was decreased. No significant differences were found in terms of migration and invasion between the downregulated clones and the controls. Expression of TCN1, KLK6, ADAM29, LGAL4, TSPAN8 and SHPS-1 was found to be significantly different between MUC1 downregulated clones and the control cells. In vivo assays have shown that mice injected with MUC1 downregulated cells develop smaller tumours when compared to mice injected with the control cells.
  
  
  CONCLUSIONS
  These results indicate that MUC1 downregulation alters the phenotype and tumorigenicity of MKN45 gastric carcinoma cells and also the expression of several molecules that can be involved in tumorigenic events. Therefore, MUC1 should be further studied to better clarify its potential as a novel therapeutic target for gastric cancer.
authors.affiliation: Institute of Molecular Pathology and Immunology of the University of Porto, Porto, Portugal.
authors.forename: Natália R
authors.initials: NR
authors.lastname: Costa
authors.forename: Paula
authors.initials: P
authors.lastname: Paulo
authors.forename: Thomas
authors.initials: T
authors.lastname: Caffrey
authors.forename: Michael A
authors.initials: MA
authors.lastname: Hollingsworth
authors.forename: Filipe
authors.initials: F
authors.lastname: Santos-Silva
mesh_terms: D000818:Animals; D001483:Base Sequence; D015153:Blotting, Western; D045744:Cell Line, Tumor; D017931:DNA Primers; D015536:Down-Regulation; D005260:Female; D005455:Fluorescent Antibody Technique; D006801:Humans; D020287:In Situ Nick-End Labeling; D051379:Mice; D008819:Mice, Nude; D018396:Mucin-1 / Q000378:metabolism*; D010641:Phenotype; D060888:Real-Time Polymerase Chain Reaction; D013274:Stomach Neoplasms / Q000473:pathology*
chemical_list: D017931:DNA Primers; C060192:MUC1 protein, human; D018396:Mucin-1
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