title: Brush border myosin Ia inactivation in gastric but not endometrial tumors.
abstract: Brush border Myosin Ia (MYO1A) has been shown to be frequently mutated in colorectal tumors with microsatellite instability (MSI) and to have tumor suppressor activity in intestinal tumors. Here, we investigated the frequency of frameshift mutations in the A8 microsatellite in exon 28 of MYO1A in MSI gastric and endometrial tumors and found a high mutation rate in gastric (22/47; 46.8%) but not endometrial (3/48; 6.2%) tumors. Using a regression model, we show that MYO1A mutations are likely to confer a growth advantage to gastric, but not endometrial tumors. The mutant MYO1A(7A)  protein was shown to lose its membrane localization in gastric cancer cells and a cycloheximide-chase assay demonstrated that the mutant MYO1A(7A)  protein has reduced stability compared to the wild type MYO1A. Frequent MYO1A promoter hypermethylation was also found in gastric tumors. Promoter methylation negatively correlates with MYO1A mRNA expression in a series of 58 non-MSI gastric primary tumors (Pearson's r = -0.46; p = 0.0003) but not in a cohort of 54 non-MSI endometrial tumors and treatment of gastric cancer cells showing high MYO1A promoter methylation with the demethylating agent 5-aza-2'-deoxycytidine, resulted in a significant increase of MYO1A mRNA levels. We found that normal gastric epithelial cells, but not normal endometrial cells, express high levels of MYO1A. Therefore, when considered together, our findings suggest that MYO1A has tumor suppressor activity in the normal gastric epithelium but not in the normal endometrium and inactivation of MYO1A either genetically or epigenetically may confer gastric epithelial cells a growth advantage.
authors.affiliation: Group of Molecular Oncology, CIBBIM-Nanomedicine, Vall d'Hebron University Hospital Research Institute, Universitat Autònoma de Barcelona, Passeig Vall d'Hebron 119-129, Barcelona, Spain.
authors.forename: Rocco
authors.initials: R
authors.lastname: Mazzolini
authors.forename: Paulo
authors.initials: P
authors.lastname: Rodrigues
authors.forename: Sarah
authors.initials: S
authors.lastname: Bazzocco
authors.forename: Higinio
authors.initials: H
authors.lastname: Dopeso
authors.forename: Ana M
authors.initials: AM
authors.lastname: Ferreira
authors.forename: Silvia
authors.initials: S
authors.lastname: Mateo-Lozano
authors.forename: Elena
authors.initials: E
authors.lastname: Andretta
authors.forename: Stefan M
authors.initials: SM
authors.lastname: Woerner
authors.forename: Hafid
authors.initials: H
authors.lastname: Alazzouzi
authors.forename: Stefania
authors.initials: S
authors.lastname: Landolfi
authors.forename: Javier
authors.initials: J
authors.lastname: Hernandez-Losa
authors.forename: Irati
authors.initials: I
authors.lastname: Macaya
authors.forename: Hiromu
authors.initials: H
authors.lastname: Suzuki
authors.forename: Santiago
authors.initials: S
authors.lastname: Ramón y Cajal
authors.forename: Mark S
authors.initials: MS
authors.lastname: Mooseker
authors.forename: John M
authors.initials: JM
authors.lastname: Mariadason
authors.forename: Johannes
authors.initials: J
authors.lastname: Gebert
authors.forename: Robert M W
authors.initials: RM
authors.lastname: Hofstra
authors.forename: Jaume
authors.initials: J
authors.lastname: Reventós
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Yamamoto
authors.forename: Simo
authors.initials: S
authors.lastname: Schwartz
authors.forename: Diego
authors.initials: D
authors.lastname: Arango
mesh_terms: D001374:Azacitidine / Q000031:analogs & derivatives / Q000494:pharmacology; D001483:Base Sequence; D015153:Blotting, Western; D019175:DNA Methylation; D017931:DNA Primers; D000077209:Decitabine; D016889:Endometrial Neoplasms / Q000235:genetics* / Q000473:pathology; D005260:Female; D006801:Humans; D018613:Microscopy, Confocal; D008871:Microvilli / Q000378:metabolism*; D009154:Mutation; D018995:Myosin Heavy Chains / Q000235:genetics*; D024461:Myosin Type I / Q000235:genetics*; D011401:Promoter Regions, Genetic; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013274:Stomach Neoplasms / Q000235:genetics* / Q000473:pathology
chemical_list: D017931:DNA Primers; C062291:MYO1A protein, human; D000077209:Decitabine; D024461:Myosin Type I; D018995:Myosin Heavy Chains; D001374:Azacitidine