a b s t r a c tSilent mating type information regulation 1 (SIRT1) is implicated in tumorigenesis through its effect on autophagy. In gastric cancer (GC), SIRT1 is a marker for prognosis and is involved in cell invasion, proliferation, epithelial-mesenchymal transition (EMT) and drug resistance. Autophagy can function as a cell-survival mechanism or lead to cell death during the genesis and treatment of GC. This functionality is determined by factors including the stage of the tumor, cellular context and stress levels. Interestingly, SIRT1 can regulate autophagy through the deacetylation of autophagy-related genes (ATGs) and mediators of autophagy. Taken together, these findings support the need for continued research efforts to understand the mechanisms mediating the development of gastric cancer and unveil new strategies to eradicate this disease.

Aim. Sirtuin 1 (SIRT1) can induce autophagy through deacetylation of Beclin-1 and other autophagy mediators. However, the relationship between SIRT1 and autophagy in GC has not been defined. Therefore, the aim of this study was to confirm the prognostic value of SIRT1 and Beclin-1 and their relationship in GC patients. Methods. Transmission electron microscopy (TEM) was performed to examine the autophagy in GC patients. Immunohistochemistry was used to examine the expression of SIRT1, Beclin-1 in GC, and adjacent nonneoplastic mucosa. Results. In 7 out of 8 GC patients' samples examined by TEM, more autophagic vesicles were observed in GC tissues compared to adjacent nonneoplastic mucosa tissue. A positive correlation between SIRT1 and Beclin-1 expression was observed. Furthermore, Beclin-1 or SIRT1 expression alone or their combined expression were significantly correlated with advanced clinicopathological parameters. High Beclin-1 and SIRT1 expression alone and their combined high expression predicted shorter overall survival and relapse-free survival. Both high Beclin-1 and SIRT1 expressions were independent prognostic factors for poor survival of GC. Conclusions. Based on our results we can conclude that SIRT1 and Beclin-1 expression alone or in combination can be used as prognostic indicator and may represent new therapeutic targets in GC.

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