title: Tumor microsatellite instability in early onset gastric cancer.
abstract: Gastric cancer (GC) remains a leading cause of cancer mortality worldwide. Genetic factors are implicated, including DNA mismatch repair (MMR) deficiency manifested as tumor microsatellite instability (MSI). However, a standardized panel of markers and a definition of low-versus-high level MSI in GC are lacking. We examined a population-based cohort of early onset (<or=50 yrs) gastric cancer. We identified 211 cases of early onset gastric cancer in Central-East Ontario from 1989 to 1993, with archival material available for 139 cases. Testing included a six-mononucleotide marker panel and a three-MMR immunohistochemical panel. Overall, 30% (41 of 139) of GC were MSI+, with allelic shifts at one to eight markers. An unexpected discordance between the BAT-25, BAT-26, and BAT-40 markers was observed in the MSI+ cases. Six cases showing multiple loci instability (>or=3 markers MSI+/MSI-high) demonstrated MMR protein deficiency. Three novel hMLH1 mutations (two germline frameshift and one somatic nonsense) were also found. The only significant clinicopathological associations were increased tumor size in MSI+ cases (P=0.04) and Lauren histotype (P=0.006) and tumor grade (P=0.007) in MSI-high cases. Tumor size, location, depth, nodal status, and Ming subtype were significant prognostic variables. Therefore, we propose a new definition of high-level MSI based on unifying characteristics of instability of more than or equal to three of six mononucleotide markers and loss of MMR protein expression.
authors.affiliation: Center for Cancer gEnetics-Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto, Ontario, Canada M5G 1X5.
authors.forename: Julinor
authors.initials: J
authors.lastname: Bacani
authors.forename: Rhonda
authors.initials: R
authors.lastname: Zwingerman
authors.forename: Nando
authors.initials: N
authors.lastname: Di Nicola
authors.forename: Samantha
authors.initials: S
authors.lastname: Spencer
authors.forename: Trish
authors.initials: T
authors.lastname: Wegrynowski
authors.forename: Kyle
authors.initials: K
authors.lastname: Mitchell
authors.forename: Kazuko
authors.initials: K
authors.lastname: Hay
authors.forename: Mark
authors.initials: M
authors.lastname: Redston
authors.forename: Eric
authors.initials: E
authors.lastname: Holowaty
authors.forename: David
authors.initials: D
authors.lastname: Huntsman
authors.forename: Aaron
authors.initials: A
authors.lastname: Pollett
authors.forename: Robert
authors.initials: R
authors.lastname: Riddell
authors.forename: Steven
authors.initials: S
authors.lastname: Gallinger
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000328:Adult; D017668:Age of Onset; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D005260:Female; D005656:Fungal Proteins / Q000378:metabolism; D015972:Gene Expression Regulation, Neoplastic; D005820:Genetic Testing; D042822:Genomic Instability / Q000235:genetics*; D005838:Genotype; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D018895:Microsatellite Repeats / Q000235:genetics*; D000070957:MutL Protein Homolog 1; D051718:MutS Homolog 2 Protein / Q000378:metabolism; D009154:Mutation / Q000235:genetics; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D010641:Phenotype; D013274:Stomach Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D013997:Time Factors
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; C094443:G-T mismatch-binding protein; C501486:MLH1 protein, human; D009687:Nuclear Proteins; D000070957:MutL Protein Homolog 1; D051718:MutS Homolog 2 Protein