title: Microsatellite instability in gastric cancer and pre-cancerous lesions.
abstract: OBJECTIVE
  To investigate the microsatellite instability (MSI) in cancer and pre-cancerous lesions of the stomach and its mechanisms underlying the development of gastric cancer.
  
  
  METHODS
  Thirty-six gastric cancer samples were obtained from patients undergoing surgery. Forty-one gastric mucosa samples with dysplasia and 51 with intestinal metaplasia (IM) were obtained from patients with chronic gastritis undergoing gastro-endoscopy. Genomic DNA was extracted from the samples. Silver staining single strand conformation polymorphis-polymerize chain reaction (SSCP-PCR) was used to screen MSI markers at 5 loci (Bat-25, Bat-26, D5S346, D17S250, and D2S123) in fresh tissues and formalin-fixed, paraffin-embedded samples and their corresponding normal gastric mucosa.
  
  
  RESULTS
  The abnormal shifting of the single-strand DNA (MSI) was identified in 21 out of 36 (58.3%) gastric cancers. Seven cases showed high-level MSI (two or more loci altered) and 14 showed low-level MSI (one locus altered). Gastric cancer with MSI had a tendency to be located in the distal stomach. MSI was also detected in 11 out of 41 (26.8%) dysplasia samples and in 9 of 51 (17.6%) IM samples respectively. Three cases of dysplasia and one case of IM showed high-level MSI. Eight cases of dysplasia and 8 cases of IM displayed low-level MSI. MIS in IM was found only in moderate or severe-grade IM. No association was detected between MSI and dysplasia grade.
  
  
  CONCLUSIONS
  Accumulation of MSI in dysplasia and intestinal metaplasia of gastric mucosa may be an early molecular event during gastric carcinogenesis and may contribute to the acquisition of transformed cell phenotype and the development of gastric cancer.
authors.affiliation: Department of Oncology, the First Affiliated Hospital of Nanjing Medical University, 300 Guangshou Road, Nanjing 210029, Jiangsu Province, China. liupinga@yahoo.com
authors.forename: Ping
authors.initials: P
authors.lastname: Liu
authors.forename: Xiao-Yong
authors.initials: XY
authors.lastname: Zhang
authors.forename: Yun
authors.initials: Y
authors.lastname: Shao
authors.forename: Dao-Fu
authors.initials: DF
authors.lastname: Zhang
mesh_terms: D017931:DNA Primers; D005260:Female; D005753:Gastric Mucosa / Q000473:pathology; D005819:Genetic Markers; D006801:Humans; D007413:Intestinal Mucosa / Q000473:pathology; D008297:Male; D008679:Metaplasia; D018895:Microsatellite Repeats / Q000235:genetics*; D008875:Middle Aged; D016133:Polymerase Chain Reaction; D011230:Precancerous Conditions / Q000235:genetics*; D013274:Stomach Neoplasms / Q000235:genetics*
chemical_list: D017931:DNA Primers; D005819:Genetic Markers