Aberrant expression of SIRT3 is conversely correlated with the progression and prognosis of human gastric cancer

https://doi.org/10.1016/j.bbrc.2013.11.068Get rights and content

Highlights

  • SIRT3 is decreased or completely absent in human GC.

  • SIRT3 is negatively correlated with tumor infiltration, differentiation and stage.

  • SIRT3 is conversely correlated with survival of GC patients.

  • Knockdown of SIRT3 in MGC-803 cells results in increased expression of HIF-1α.

Abstract

SIRT3 is a NAD+-dependent histone deacetylaseand and plays a critical role in various human carcinomas. However, its precise role in the pathogenesis of gastric cancer (GC) is still unclear. Western blot and Real-Time PCR were used to detect the protein and mRNA level of SIRT3 in freshly collected samples from GC patients. Immunohistochemistry staining was adopted to determine the expression of SIRT3 in 65 formalin-fixed, paraffin-embedded samples from GC patients. In addition, western blot was used to detect the protein levels of SIRT3 and HIF-1α in gastric cancer cells MGC-803 transfected with SIRT3 or control siRNA. Western blot analysis of 25 samples from GC patients showed that 64% (16/25) of patients exhibited decreased expression of SIRT3, whereas 4.0% (1/25) of patients displayed complete loss. In addition, Real-Time PCR analysis showed that GC patients had decreased expression of SIRT3 mRNA. Furthermore, immunohistochemistry analysis of 65 formalin-fixed, paraffin-embedded samples from GC patients showed that 67.7% (44/65) had decreased SIRT3 staining in the cancer tissues. Notably, the expression level of SIRT3 was inversely correlated with clinicopathological variable, including tumor infiltration, tumor differentiation and tumor stage and 5-year survival of these patients. In vitro experiment showed that knockdown of SIRT3 in MGC-803 gastric cancer cells significantly increased the expression of HIF-1α. Our results provide the first evidence showing that an aberrantly decreased expression of SIRT3 occurred in GC patients, suggesting that SIRT3 might function as a mitochondrial tumor suppressor in GC. Furthermore, the possible mechanism by which SIRT3 affect the progress of GC is its direct control of HIF-1α.

Introduction

Gastric cancer (GC) ranks the second mortality of cancer in the worldwide [1]. Both exogenous and endogenous factors contribute to its development and progression. It has been recognized that multiple genetic and epigenetic alteration or abnormality occurs in the development of GC [2]. In this regard, loss or altered function of tumor suppressor genes plays a critical role in GC etiology.

Sirtuins are NAD+-dependent histone deacetylases (HDAC) and widely expressed in normal tissues in mammary animals. Seven members have been identified in human, including Sirt1–7, and play essential roles in cellular physiology, including cell metabolism, cell cycle, cell division and transcriptional regulation. Furthermore, they are also involved in the pathogenesis of series of diseases such as metabolic diseases [3], neurodegenerative diseases [4], cardiovascular diseases [5] and aging [6].

Human SIRT3 is a full-length 44-kD protein and localized mainly in cell mitochondrial. It has the capacity to activate fat oxidation, amino-acid metabolism and electron transport via interaction with various substrates [7], [8], [9].

Recently, it has been demonstrated that various types of clinical carcinomas, including hepatocellular carcinoma [10], [11], breast carcinoma [12], lung NSC [12], [13], medulloblastoma [12], neck carcinoma and prostate carcinoma [13], [14] displayed decreased levels or deletion of SIRT3 and SIRT3−/− mice were more susceptible to develop mammary tumors compared with the wide type cohorts, suggesting that SIRT3 may function as a mitochondrial tumor suppressor [15], [16], [17]. However, its role in the pathogenesis of gastric cancer is still unclear.

In this study, we investigated the expression of SIRT3 and its correlation with the disease progress and prognosis of gastric cancer. Our data showed that there was significantly decreased expression of SIRT3 protein and mRNA levels in the tissues of 64.0% GC patients. Notably, the expression level of SIRT3 was closely correlated with the tumor infiltration, tumor differentiation and tumor stage. Furthermore, our retrospective analysis of 65 GC patients showed that patients with high SIRT3 expression survived much longer than those with low SIRT3 expression. Taken together, our data demonstrate a critical role for SIRT3 in the progress and prognosis of clinical GC.

Section snippets

Patients and tissue samples

All the patients were diagnosed according to the 6th edition of AJCC cancer staging manual. The matched fresh tissue samples of primary gastric cancer and adjacent normal tissues from the same patient used for western blot and Real-Time PCR were collected from 25 GC patients, including 18 male and 7 female with a mean age of 61.8 ± 12.5 years, undergoing surgical resection at Longgang District Central Hospital of Shenzhen and Shenzhen People’s Hospital (Shenzhen, China) from 2011 to 2012. All

Expression of SIRT3 is decreased or completely absent in human GC tissues

It was previously shown that SIRT3 could function as either oncogene or tumor suppressor gene. To assess if SIRT3 was involved in the pathogenesis of gastric cancer, we firstly detected the expression of SIRT3 in 25 GC patients using western blot assay. All the GC patients were newly diagnosed and did not receive any treatment before surgical resection. Interestingly, western blot revealed that 64.0% of patients with GC (16/25) had significant reduction of SIRT3 compared with the adjacent

Discussion

SIRT3 has been reported to be correlated with a panel of human tumors, such as hepatocellular carcinoma, breast carcinoma, medulloblastoma, lung NSCO and varian carcinoma, where SIRT3 was obviously deleted [18].

These data have indicated that SIRT3 might function as a mitochondrial tumor suppressor. However, SIRT3 seems to also function as an oncogene in several tumors (e.g. oral carcinoma). SIRT3 was overexpressed in oral squamous cell carcinoma (OSCC) cell lines and down-regulation of SIRT3

Acknowledgments

We thank Dr. Hui Che (The University of Hong Kong) for her technical support. This work was supported by Grants provided from the Scientific Foundation of Shenzhen (No. 201102116).

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    These authors contribute equally to this work.

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