Sirtuin 2 (Sirt2) Expression Predicts Lymph Node Metastasis and Poor Overall Survival of Patients with Esophageal Squamous Cell Carcinoma

Selective inhibition of SIRT2: A disputable therapeutic approach in cancer therapy

Sirtuin 2 (SIRT2) is involved in a wide range of processes, from transcription to metabolism to genome stability. Dysregulation of SIRT2 has been associated with the pathogenesis and progression of different diseases, such as cancer and neurodegenerative disorders. In this context, targeting SIRT2 activity by small molecule inhibitors is a promising therapeutic strategy for treating related conditions, particularly cancer. This review summarizes the regulatory roles and molecular mechanisms of SIRT2 in cancer and the attempts to evaluate potential antitumor activities of SIRT2-selective inhibitors by in vitro and in vivo testing, which are expected to deepen our understanding of the role of SIRT2 in tumorigenesis and progression and may offer important clues or inspiration ideas for developing SIRT2 inhibitors with excellent affinity and selectivity.

Role of sirtuins in esophageal cancer: Current status and future prospects

Esophageal cancer (EC) is a malignant cancer that still has a poor prognosis, although its prognosis has been improving with the development of multidisciplinary treatment modalities such as surgery, chemotherapy and radiotherapy. Therefore, identifying specific molecular markers that can be served as biomarkers for the prognosis and treatment response of EC is highly desirable to aid in the personalization and improvement of the precision of medical treatment. Sirtuins are a family of nicotinamide adenine dinucleotide (NAD+)-dependent proteins consisting of seven members (SIRT1-7). These proteins have been reported to be involved in the regulation of a variety of biological functions including apoptosis, metabolism, stress response, senescence, differentiation and cell cycle progression. Given the variety of functions of sirtuins, they are speculated to be associated in some manner with cancer progression. However, while the role of sirtuins in cancer progression has been investigated over the past few years, their precise role remains difficult to characterize, as they have both cancer-promoting and cancer-suppressing properties, depending on the type of cancer. These conflicting characteristics make research into the nature of sirtuins all the more fascinating. However, the role of sirtuins in EC remains unclear due to the limited number of reports concerning sirtuins in EC. We herein review the current findings and future prospects of sirtuins in EC.

Sirtuin2 correlates with lymph node metastasis, increased FIGO stage, worse overall survival, and reduced chemosensitivity to cisplatin and paclitaxel in endometrial cancer

BACKGROUND

This study aimed to investigate the correlation of sirtuin2 (SIRT2) with clinical characteristics, prognosis in endometrial cancer (EC) patients, and its effect on chemosensitivity in EC cell lines.

METHODS

A total of 137 EC patients who underwent surgical resection were retrospectively enrolled. SIRT2 expression in tumor tissues (n = 137) and adjacent tissues (n = 61) was detected by immunohistochemistry (IHC) staining and evaluated by a semiquantitative scoring method. EC patients' clinical characteristics and survival data were collected. Besides, SIRT2 was modulated by plasmid transfection in EC cells, then their chemosensitivity to cisplatin and paclitaxel was evaluated.

RESULTS

SIRT2 was increased in tumor tissues compared with adjacent tissues (reflected by both IHC score and high-expression ratio, both P < 0.001). Meanwhile, tumor SIRT2 was positively correlated with lymph node metastasis (P = 0.037) and the International Federation of Gynecology and Obstetrics (FIGO) stage (P = 0.044), but not other clinical characteristics. Moreover, tumor SIRT2 high expression was correlated with worse overall survival (OS) (P = 0.023), while it could not independently predict OS (P = 0.090, hazard ratio = 2.782). Besides, both mRNA and protein levels of SIRT2 were increased in Ishikawa (P = 0.035) and KLE (P < 0.001) cells compared with human endometrial epithelial cells. SIRT2 overexpression decreased chemosensitivity to cisplatin and paclitaxel in Ishikawa cells, while SIRT2 knockdown increased chemosensitivity to cisplatin and paclitaxel in KLE cells (all P < 0.05).

CONCLUSION

SIRT2 correlates with lymph node metastasis, increased FIGO stage, worse OS, and reduced chemosensitivity to cisplatin and paclitaxel in EC.

Sirtuins' control of autophagy and mitophagy in cancer

Mammalian cells use a specialized and complex machinery for the removal of altered proteins or dysfunctional organelles. Such machinery is part of a mechanism called autophagy. Moreover, when autophagy is specifically employed for the removal of dysfunctional mitochondria, it is called mitophagy. Autophagy and mitophagy have important physiological implications and roles associated with cellular differentiation, resistance to stresses such as starvation, metabolic control and adaptation to the changing microenvironment. Unfortunately, transformed cancer cells often exploit autophagy and mitophagy for sustaining their metabolic reprogramming and growth to a point that autophagy and mitophagy are recognized as promising targets for ongoing and future antitumoral therapies. Sirtuins are NAD+ dependent deacylases with a fundamental role in sensing and modulating cellular response to external stresses such as nutrients availability and therefore involved in aging, oxidative stress control, inflammation, differentiation and cancer. It is clear, therefore, that autophagy, mitophagy and sirtuins share many common aspects to a point that, recently, sirtuins have been linked to the control of autophagy and mitophagy. In the context of cancer, such a control is obtained by modulating transcription of autophagy and mitophagy genes, by post translational modification of proteins belonging to the autophagy and mitophagy machinery, by controlling ROS production or major metabolic pathways such as Krebs cycle or glutamine metabolism. The present review details current knowledge on the role of sirtuins, autophagy and mitophagy in cancer to then proceed to discuss how sirtuins can control autophagy and mitophagy in cancer cells. Finally, we discuss sirtuins role in the context of tumor progression and metastasis indicating glutamine metabolism as an example of how a concerted activation and/or inhibition of sirtuins in cancer cells can control autophagy and mitophagy by impinging on the metabolism of this fundamental amino acid.

SIRT2 expression exhibits potential to serve as a biomarker for disease surveillance and prognosis in the management of cervical cancer patients

This study aimed to compare the sirtuin 2 (SIRT2) expression between tumor tissue and adjacent tissue, and to investigate the association of tumor SIRT2 expression with clinical characteristics and survival profiles in cervical cancer patients.One hundred ninety-one cervical cancer patients were reviewed in this retrospective study. All patients underwent surgical resection and had well-preserved tumor tissue and adjacent tissue, which were obtained for SIRT2 expression detection by immunohistochemistry (IHC). Clinical parameters were obtained. Disease free survival (DFS) and overall survival (OS) were calculated.Both SIRT2 expression by IHC score (P < .001) and the percentage of SIRT2 high expression (defined as IHC score >3) (P < .001) were declined in tumor tissue compared with paired adjacent tissue. In addition, SIRT2 expression in tumor tissue was negatively correlated with tumor size (P = .047), lymph node metastasis (P = .009) and FIGO stage (P = .001). And the DFS (P = .007) as well as OS (P = .008) were better in patients with SIRT2 high expression compared with patents with SIRT2 low expression. Univariate Cox's proportional hazards regression model analyses revealed that high SIRT2 expression in tumor tissue was a predictive factor for more prolonged DFS (P = .009) and OS (P = .011), while multivariate Cox's proportional hazards regression model analysis disclosed that it lacks independent predictive value for DFS (P = .084) or OS (P = .132).SIRT2 expression exhibits potential to serve as a biomarker for disease surveillance and prognosis in the management of cervical cancer patients.

The Roles of Sirtuin Family Proteins in Cancer Progression

Sirtuin family members are characterized by either mono-ADP-ribosyltransferase or deacylase activity and are linked to various cancer-related biological pathways as regulators of transcriptional progression. Sirtuins play fundamental roles in carcinogenesis and maintenance of the malignant phenotype, mainly participating in cancer cell viability, apoptosis, metastasis, and tumorigenesis. Although sirtuin family members have a high degree of homology, they may play different roles in various kinds of cancer. This review highlights their fundamental roles in tumorigenesis and cancer development and provides a critical discussion of their dual roles in cancer, namely, as tumor promoters or tumor suppressors.