Epigenetic alterations of gastrokine 1 gene expression in gastric cancer

Filomena Altieri,Maurizio De Palma,Giuseppina Miselli,Chiara Stella Di Stadio,Antonella Federico,Paolo Arcari,Emilia Rippa

doi:10.18632/oncotarget.14817

Filomena Altieri, Maurizio De Palma + Show 5 more

Open Access

https://doi.org/10.18632/oncotarget.14817

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Abstract

The gastrokine 1 (GKN1) protein is important for maintaining the physiological function of the gastric mucosa. GKN1 is down-regulated in gastric tumor tissues and derived cell lines and its over-expression in gastric cancer cells induces apoptosis, suggesting a possible role for the protein as a tumor suppressor. However, the mechanism by which GKN1 is inactivated in gastric cancer remains unknown. Here, we investigated the causes of GKN1 silencing to determine if epigenetic mechanisms such as histonic modification could contribute to its down-regulation. To this end, chromatin immunoprecipitation assays for the trimethylation of histone 3 at lysine 9 (H3K9triMe) and its specific histone-lysine N-methyltransferase (SUV39H1) were performed on biopsies of normal and cancerous human gastric tissues. GKN1 down-regulation in gastric cancer tissues was shown to be associated with high levels of H3K9triMe and with the recruitment of SUV39H1 to the GKN1 promoter, suggesting the presence of an epigenetic transcriptional complex that negatively regulates GKN1 expression in gastric tumors. The inhibition of histone deacetylases with trichostatin A was also shown to increase GKN1 mRNA levels. Collectively, our results indicate that complex epigenetic machinery regulates GKN1 expression at the transcriptional level, and likely at the translational level.

Highlights

Gastrokine 1 (GKN1) is a tissue-specific 18 kDa protein that is highly expressed in the gastric mucosa of many mammalian species [1, 2]
Treatment of AGS-Epstein–Barr virus (EBV) and AGS-Epstein– Barr nuclear antigen 1 (EBNA1) cell lines with 5’ azacytidine showed that gastrokine 1 (GKN1) and GKN2 were transcriptionally silenced by DNA methylation, and that latent EBV infection further reduced GKN1 and GKN2 expression in AGS cells
We investigated the relationship between the expression of GKN1 and that of Histone-lysine N-methyltransferase (SUV39H1), histone deacetylase 1 (HDAC1), and H3K9triMe

Summary

Introduction

Gastrokine 1 (GKN1) is a tissue-specific 18 kDa protein that is highly expressed in the gastric mucosa of many mammalian species [1, 2]. Treatment of tumor cells with recombinant human GKN1 reduced the proliferation of AGS cells compared with human embryonic kidney cells (HEK 293) and non-gastric cancer cells (H1355) [11]. These data suggest that GKN1 functions as a tumor suppressor and a modulator of apoptotic signals in GC. The ectopic expression of EBNA1 slightly increased GKN1 and GKN2 basal mRNA levels, but reduced their responsiveness to demethylating agents These findings indicated that EBNA1 contributes to the transcriptional complex and epigenetic deregulation of GKN1 and GKN2 tumor suppressor genes in EBV-positive GC.

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