MDM2-dependent Sirt1 degradation is a prerequisite for Sirt6-mediated cell death in head and neck cancers

Targeting histone deacetylases in head and neck squamous cell carcinoma: molecular mechanisms and therapeutic targets

The onerous health and economic burden associated with head and neck squamous cell carcinoma (HNSCC) is a global predicament. Despite the advent of novel surgical techniques and therapeutic protocols, there is an incessant need for efficacious diagnostic and therapeutic targets to monitor the invasion, metastasis and recurrence of HNSCC due to its substantial morbidity and mortality. The differential expression patterns of histone deacetylases (HDACs), a group of enzymes responsible for modifying histones and regulating gene expression, have been demonstrated in neoplastic tissues. However, there is limited knowledge regarding the role of HDACs in HNSCC. Consequently, this review aims to summarize the existing research findings and explore the potential association between HDACs and HNSCC, offering fresh perspectives on therapeutic approaches targeting HDACs that could potentially enhance the efficacy of HNSCC treatment. Additionally, the Cancer Genome Atlas (TCGA) dataset, CPTAC, HPA, OmicShare, GeneMANIA and STRING databases are utilized to provide supplementary evidence on the differential expression of HDACs, their prognostic significance and predicting functions in HNSCC patients.

Sirt6-Mediated Cell Death Associated with Sirt1 Suppression in Gastric Cancer

BACKGROUND

Gastric cancer, one of the leading causes of cancer-related death, is strongly associated with H. pylori infection, although other risk factors have been identified. The sirtuin (Sirt) family is involved in the tumorigenesis of gastric cancer, and sirtuins can have pro- or anti-tumorigenic effects.

METHODS

After determining the overall survival rate of gastric cancer patients with or without Sirt6 expression, the effect of Sirt6 upregulation was also tested using a xenograft mouse model. The regulation of Sirt6 and Sirt1, leading to the induction of mouse double minute 2 homolog (MDM2) and reactive oxygen species (ROS), was mainly analyzed using Western blotting and immunofluorescence staining, and gastric cancer cell (SNU-638) death associated with these proteins was measured using flow cytometric analysis.

RESULTS

Sirt6 overexpression led to Sirt1 suppression in gastric cancer cells, resulting in a higher level of gastric cancer cell death in vitro and a reduced tumor volume. ROS and MDM2 expression levels were upregulated by Sirt6 overexpression and/or Sirt1 suppression according to Western blot analysis. The upregulated ROS ultimately led to gastric cancer cell death as determined via Western blot and flow cytometric analysis.

CONCLUSION

We found that the upregulation of Sirt6 suppressed Sirt1, and Sirt6- and Sirt1-induced gastric cancer cell death was mediated by ROS production. These findings highlight the potential of Sirt6 and Sirt1 as therapeutic targets for treating gastric cancer.

Immunoexpression of SIRT1, 6, and 7 in oral leukoplakia and oral squamous cell carcinoma

Sirtuins (SIRTs) are a family of proteins involved in the metabolic process responsible for extending the lifespan. The role of SIRT1, 6, and 7 in oral squamous cell carcinoma (OSCC) and oral leukoplakia (OLP), one of its precursors, is still elusive. In this study, 82 OLP and 77 OSCC were immunohistochemically examined for SIRT1, 6, and 7. Stained sections were thoroughly scanned and evaluated using a digital image analysis program. The SIRT1, 6, and 7 expressions were detected in the nuclei of epithelial and carcinoma cells in various degrees. Afterward, any correlations among SIRTs, including associations with clinicopathological features and the Kaplan-Meier curves were analyzed. OSCC demonstrated significantly higher SIRT1 expression than OLP, while non-dysplastic lesions showed significantly higher SIRT6 expression than other lesions. A strong correlation was observed between SIRT6 and 7 in OLP, SIRT1 and 6 in in OSCC and in SIRT6 and 7 when all lesion types were considered. There were no significant differences between SIRTs reactivity and the clinical features in OLP. For OSCC, SIRT1 and 6 was found to be directly associated with site of the lesion, while SIRT7 showed a direct relationship between gender, stromal lymphocytic infiltration, and depth of the invasion. OSCC with high SIRT7 expression revealed a slightly lower survival probability, although not statistically significant (p = 0.1019). Our findings suggest that SIRT1, 6, and 7 may play correlated and diverse roles in the development and advancement of OSCC.

SIRT6 in Aging, Metabolism, Inflammation and Cardiovascular Diseases

As an important NAD⁺-dependent enzyme, SIRT6 has received significant attention since its discovery. In view of observations that SIRT6-deficient animals exhibit genomic instability and metabolic disorders and undergo early death, SIRT6 has long been considered a protein of longevity. Recently, growing evidence has demonstrated that SIRT6 functions as a deacetylase, mono-ADP-ribosyltransferase and long fatty deacylase and participates in a variety of cellular signaling pathways from DNA damage repair in the early stage to disease progression. In this review, we elaborate on the specific substrates and molecular mechanisms of SIRT6 in various physiological and pathological processes in detail, emphasizing its links to aging (genomic damage, telomere integrity, DNA repair), metabolism (glycolysis, gluconeogenesis, insulin secretion and lipid synthesis, lipolysis, thermogenesis), inflammation and cardiovascular diseases (atherosclerosis, cardiac hypertrophy, heart failure, ischemia-reperfusion injury). In addition, the most recent advances regarding SIRT6 modulators (agonists and inhibitors) as potential therapeutic agents for SIRT6-mediated diseases are reviewed.

Reactive Oxygen Species Enlightened Therapeutic Strategy for Oral and Maxillofacial Diseases-Art of Destruction and Reconstruction

Reactive oxygen species (ROS) are byproducts of cell metabolism produced by living cells and signal mediators in biological processes. As unstable and highly reactive oxygen-derived molecules, excessive ROS production and defective oxidant clearance, or both, are associated with the pathogenesis of several conditions. Among them, ROS are widely involved in oral and maxillofacial diseases, such as periodontitis, as well as other infectious diseases or chronic inflammation, temporomandibular joint disorders, oral mucosal lesions, trigeminal neuralgia, muscle fatigue, and oral cancer. The purpose of this paper is to outline how ROS contribute to the pathophysiology of oral and maxillofacial regions, with an emphasis on oral infectious diseases represented by periodontitis and mucosal diseases represented by oral ulcers and how to effectively utilize and eliminate ROS in these pathological processes, as well as to review recent research on the potential targets and interventions of cutting-edge antioxidant materials. The PubMed, Web of Science, and Embase databases were searched using the MesH terms "oral and maxillofacial diseases", "reactive oxygen species", and "antioxidant materials". Irrelevant, obsolete, imprecise, and repetitive articles were excluded through screening of titles, abstracts, and eventually full content. The full-text data of the selected articles are, therefore, summarized using selection criteria. While there are various emerging biomaterials used as drugs themselves or delivery systems, more attention was paid to antioxidant drugs with broad application prospects and rigorous prophase animal experimental results.

SIRT6 promotes ferroptosis and attenuates glycolysis in pancreatic cancer through regulation of the NF‑κB pathway

Pancreatic cancer (PC) is a malignant tumor with high mortality worldwide. SIRT6 plays versatile roles in human cancers. However, SIRT6 has rarely been studied in PC. The purpose of the present study was to explore the function and potential mechanism of SIRT6 in PC. The expression of SIRT6 in PC tissues and cells was detected by reverse transcription-quantitative PCR and western blotting. The overall survival time was analyzed through the Kaplan Meier method. Cell viability was measured by the Cell Counting Kit-8 assay. The Fe²⁺ content, glucose uptake, lactic acid and ATP production were detected through the corresponding kits. ROS was evaluated using the DCFH-DA detection kit. Protein expression was assessed by immunohistochemistry or western blot analysis. In the present study, SIRT6 was lowly expressed in PC tissues and cells compared with normal tissues and cells. Moreover, the low expression of SIRT6 was associated with a poor prognosis in patients with PC. Upregulation of SIRT6 significantly promoted the ferroptosis and inhibited the glycolysis in PC cells. However, knockdown of SIRT6 resisted ferroptosis and increased glycolysis in PC cells. Further studies found that the activation of NF-κB could reverse the effect of SIRT6 on PC cells. In addition, overexpression of SIRT6 restrained the growth of xenografted tumors and suppressed the nuclear transcription of NF-κB in vivo. Collectively, the present study indicated that SIRT6 promoted ferroptosis and inhibited glycolysis through inactivating the NF-κB signaling pathway in PC. These findings suggested that SIRT6 may become a therapeutic target for PC.