title: Nonsense-mediated mRNA decay impacts MSI-driven carcinogenesis and anti-tumor immunity in colorectal cancers.
abstract: Nonsense-mediated mRNA Decay (NMD) degrades mutant mRNAs containing premature termination codon (PTC-mRNAs). Here we evaluate the consequence of NMD activity in colorectal cancers (CRCs) showing microsatellite instability (MSI) whose progression is associated with the accumulation of PTC-mRNAs encoding immunogenic proteins due to frameshift mutations in coding repeat sequences. Inhibition of UPF1, one of the major NMD factors, was achieved by siRNA in the HCT116 MSI CRC cell line and the resulting changes in gene expression were studied using expression microarrays. The impact of NMD activity was also investigated in primary MSI CRCs by quantifying the expression of several mRNAs relative to their mutational status and to endogenous UPF1 and UPF2 expression. Host immunity developed against MSI cancer cells was appreciated by quantifying the number of CD3epsilon-positive tumor-infiltrating lymphocytes (TILs). UPF1 silencing led to the up-regulation of 1251 genes in HCT116, among which a proportion of them (i.e. 38%) significantly higher than expected by chance contained a coding microsatellite (P<2x10(-16)). In MSI primary CRCs, UPF1 was significantly over-expressed compared to normal adjacent mucosa (P<0.002). Our data provided evidence for differential decay of PTC-mRNAs compared to wild-type that was positively correlated to UPF1 endogenous expression level (P = 0.02). A negative effect of UPF1 and UPF2 expression on the host's anti-tumor response was observed (P<0.01). Overall, our results show that NMD deeply influences MSI-driven tumorigenesis at the molecular level and indicate a functional negative impact of this system on anti-tumor immunity whose intensity has been recurrently shown to be an independent factor of favorable outcome in CRCs.
authors.affiliation: INSERM, UMR S893, Team 13 Microsatellite Instability and Cancers, Paris, France.
authors.forename: Jamila
authors.initials: J
authors.lastname: El-Bchiri
authors.forename: Agathe
authors.initials: A
authors.lastname: Guilloux
authors.forename: Peggy
authors.initials: P
authors.lastname: Dartigues
authors.forename: Etienne
authors.initials: E
authors.lastname: Loire
authors.forename: Dominique
authors.initials: D
authors.lastname: Mercier
authors.forename: Olivier
authors.initials: O
authors.lastname: Buhard
authors.forename: Iradj
authors.initials: I
authors.lastname: Sobhani
authors.forename: Pierre
authors.initials: P
authors.lastname: de la Grange
authors.forename: Didier
authors.initials: D
authors.lastname: Auboeuf
authors.forename: Françoise
authors.initials: F
authors.lastname: Praz
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Fléjou
authors.forename: Alex
authors.initials: A
authors.lastname: Duval
mesh_terms: D018389:Codon, Nonsense; D015179:Colorectal Neoplasms / Q000235:genetics* / Q000276:immunology* / Q000378:metabolism; D016368:Frameshift Mutation; D020869:Gene Expression Profiling; D020868:Gene Silencing; D045325:HCT116 Cells; D006801:Humans; D053842:Microsatellite Instability; D020365:RNA Helicases; D020871:RNA Stability; D012333:RNA, Messenger / Q000378:metabolism*; D016601:RNA-Binding Proteins; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D014407:Tumor Cells, Cultured
chemical_list: D018389:Codon, Nonsense; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D015534:Trans-Activators; D014157:Transcription Factors; C468286:UPF2 protein, human; D020365:RNA Helicases; C101828:UPF1 protein, human