title: Lack of microRNA-101 causes E-cadherin functional deregulation through EZH2 up-regulation in intestinal gastric cancer.
abstract: E-cadherin expression disruption is commonly observed in metastatic epithelial cancers and is a crucial step in gastric cancer (GC) initiation and progression. As aberrant expression of microRNAs often perturb the normal expression/function of pivotal cancer-related genes, we characterized and dissected a pathway that causes E-cadherin dysfunction via loss of microRNA-101 and up-regulation of EZH2 expression in GC. MicroRNA microarray expression profiling and array-CGH were used to reinforce miR-101 involvement in GC. By using quantitative real-time PCR and quantitative SNaPshot genomic PCR, we confirmed that miR-101 was significantly down-regulated in GC (p < 0.0089) in comparison with normal gastric mucosas and, at least in 65% of the GC cases analysed, this down-regulation was caused by deletions and/or microdeletions at miR-101 genomic loci. Moreover, around 40% of cases showing miR-101 down-regulation displayed concomitant EZH2 over-expression (at the RNA and protein levels), which, in turn, was associated with loss/aberrant expression of E-cadherin. Interestingly, this occurred preferentially in intestinal-type GCs, retaining allele(s) untargeted by classical CDH1-inactivating mechanisms. We also demonstrated that miR-101 gain of function or direct inhibition of EZH2 in Kato III GC cells led to a strong depletion of endogenous EZH2 and consequent rescue of E-cadherin membranous localization, mimicking results obtained in clinical GC samples. In conclusion, we show that deletions and/or microdeletions at both miR-101 genomic loci cause mature miR-101 down-regulation, subsequent EZH2 over-expression and E-cadherin dysfunction, specifically in intestinal-type GC.
authors.affiliation: Institute of Molecular Pathology and Immunology, University of Porto (IPATIMUP), Portugal; Faculty of Medicine, University of Porto, Portugal.
authors.forename: Joana
authors.initials: J
authors.lastname: Carvalho
authors.forename: Nicole C
authors.initials: NC
authors.lastname: van Grieken
authors.forename: Patricia M
authors.initials: PM
authors.lastname: Pereira
authors.forename: Sónia
authors.initials: S
authors.lastname: Sousa
authors.forename: Marianne
authors.initials: M
authors.lastname: Tijssen
authors.forename: Tineke E
authors.initials: TE
authors.lastname: Buffart
authors.forename: Begoña
authors.initials: B
authors.lastname: Diosdado
authors.forename: Heike
authors.initials: H
authors.lastname: Grabsch
authors.forename: Manuel A S
authors.initials: MA
authors.lastname: Santos
authors.forename: Gerrit
authors.initials: G
authors.lastname: Meijer
authors.forename: Raquel
authors.initials: R
authors.lastname: Seruca
authors.forename: Beatriz
authors.initials: B
authors.lastname: Carvalho
authors.forename: Carla
authors.initials: C
authors.lastname: Oliveira
mesh_terms: D015703:Antigens, CD; D015820:Cadherins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D004268:DNA-Binding Proteins / Q000235:genetics*; D015536:Down-Regulation; D000071221:Enhancer of Zeste Homolog 2 Protein; D020869:Gene Expression Profiling; D015972:Gene Expression Regulation, Neoplastic / Q000502:physiology*; D006801:Humans; D035683:MicroRNAs / Q000502:physiology*; D020411:Oligonucleotide Array Sequence Analysis; D063151:Polycomb Repressive Complex 2; D060888:Real-Time Polymerase Chain Reaction; D013274:Stomach Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D014157:Transcription Factors / Q000235:genetics*; D015854:Up-Regulation
chemical_list: D015703:Antigens, CD; C513384:CDH1 protein, human; D015820:Cadherins; D004268:DNA-Binding Proteins; C534072:MIRN101 microRNA, human; D035683:MicroRNAs; D014157:Transcription Factors; C498409:EZH2 protein, human; D000071221:Enhancer of Zeste Homolog 2 Protein; D063151:Polycomb Repressive Complex 2