Introduction Gastro-oesophageal reflux disease is the main risk factor for Barrett’s oesophagus (BE), the precursor lesion to oesophageal adenocarcinoma. In BE, GORD leads to chronic inflammation and to NF-κB pathway activation.
SIRT2 is a histone deacetylase involved in deacetylation of key players in the cell, including p65, one subunit of the NF-κB transcription complex. SIRT2 is part of our previously published gene signatures in which loss of SIRT2 confers a poor prognosis and over-expression a good prognosis in keeping with its known role as a tumour suppressor.
We hypothesised that exerts its protective effect through recruitment of inflammatory cells to the tumour site via the NF-κB pathway The aim of this study was to assess the inflammatory infiltrate in positive tumoursto assess the relationship betweenthe NF-κB pathway.
Methods 76 surgical resection specimen of oesophageal adenocarcinoma were immunostained for SIRT2. An in-depth analysis of the nature of inflammatory cells localised to high SIRT2 areas was done in 5 cases using immune cell markers (CD3, CD4, CD8, CD20, CD56 and CD68). NF- κB and SIRT2 luciferase reporter assays were used with SIRT2 overexpression and TNFα stimulation to study the interplay between the NF- κB pathway and SIRT2. A panel of SIRT2 promoter mutants with mutations of one or two or both NF-κB putative binding sites, identified through an in silico analysis, were also used.
Results 32% of the cases were strongly positive for SIRT2 (+3 and +2 on a scale from 0 to +3 where 0 is negative). A higher number of inflammatory cells were identified in SIRT2-positive cases compared to SIRT2 negative cases. In particular, SIRT2 positive cases showed strong staining for CD68 indicating an enrichment in the number of macrophages. SIRT2 overexpression significantly down-regulated NF-κB activity (p = 0.0011). Immunoblotting suggests that this downregulation is probably conferred by the deacetylation of Lysine 310 at the p65 subunit of NF- κB. Luciferase assays with the full-length SIRT2-promoter reporter revealed that the SIRT2 promoter was induced by TNFα stimulation (activates NF- κB pathway). This stimulation resulted in decreased luciferase activity when the NF- κB binding sites mutants were used, suggesting a direct action of NF- κB on SIRT2.
Conclusion In oesophageal adenocarcinoma, SIRT2 expression is linked with an increased inflammatory infiltrate, especially macrophages. Luciferase reporter assays suggest that SIRT2 and NF-κB regulate each other. Taken together, downregulation of NF- κB by SIRT2 could be an explanation for the protective effect of SIRT2 overexpression in oesophageal adenocarcinoma. Further work is required to confirm these findings.
Disclosure of Interest None Declared
Statistics from Altmetric.com
If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.