Decreased SIRT4 protein levels in endometrioid adenocarcinoma tissues are associated with advanced AJCC stage

Glutamine and amino acid metabolism as a prognostic signature and therapeutic target in endometrial cancer

INTRODUCTION

Endometrial cancer (EC) is the most common female reproductive system cancer in developed countries with growing incidence and associated mortality, which may be due to the growing prevalence of obesity. Metabolism reprogramming including glucose, amino acid, and lipid remodeling is a hallmark of tumors. Glutamine metabolism has been reported to participate in tumor proliferation and development. This study aimed to develop a glutamine metabolism-related prognostic model for EC and explore potential targets for cancer treatment.

METHOD

Transcriptomic data and survival outcome of EC were retrieved from The Cancer Genome Atlas (TCGA). Differentially expressed genes related to glutamine metabolism were recognized and utilized to build a prognostic model by univariate and multivariate Cox regressions. The model was confirmed in the training, testing, and the entire cohort. A nomogram combing prognostic model and clinicopathologic features was established and tested. Moreover, we explored the effect of a key metabolic enzyme, PHGDH, on the biological behavior of EC cell lines and xenograft model.

RESULTS

Five glutamine metabolism-related genes, including PHGDH, OTC, ASRGL1, ASNS, and NR1H4, were involved in prognostic model construction. Kaplan-Meier curve suggested that patients recognized as high risk underwent inferior outcomes. The receiver operating characteristic (ROC) curve showed the model was sufficient to predict survival. Enrichment analysis recognized DNA replication and repair dysfunction in high-risk patients whereas immune relevance analysis revealed low immune scores in the high-risk group. Finally, a nomogram integrating the prognostic model and clinical factors was created and verified. Further, knockdown of PHGDH showed cell growth inhibition, increasing apoptosis, and reduced migration. Promisingly, NCT-503, a PHGDH inhibitor, significantly repressed tumor growth in vivo (p = 0.0002).

CONCLUSION

Our work established and validated a glutamine metabolism-related prognostic model that favorably evaluates the prognosis of EC patients. DNA replication and repair may be the crucial point that linked glutamine metabolism, amino acid metabolism, and EC progression. High-risk patients stratified by the model may not be sufficient for immune therapy. PHGDH might be a crucial target that links serine metabolism, glutamine metabolism as well as EC progression.

The role of protein acetylation in carcinogenesis and targeted drug discovery

Protein acetylation is a reversible post-translational modification, and is involved in many biological processes in cells, such as transcriptional regulation, DNA damage repair, and energy metabolism, which is an important molecular event and is associated with a wide range of diseases such as cancers. Protein acetylation is dynamically regulated by histone acetyltransferases (HATs) and histone deacetylases (HDACs) in homeostasis. The abnormal acetylation level might lead to the occurrence and deterioration of a cancer, and is closely related to various pathophysiological characteristics of a cancer, such as malignant phenotypes, and promotes cancer cells to adapt to tumor microenvironment. Therapeutic modalities targeting protein acetylation are a potential therapeutic strategy. This article discussed the roles of protein acetylation in tumor pathology and therapeutic drugs targeting protein acetylation, which offers the contributions of protein acetylation in clarification of carcinogenesis, and discovery of therapeutic drugs for cancers, and lays the foundation for precision medicine in oncology.

Mammalian SIRT4 is a tumor suppressor of clear cell renal cell carcinoma by inhibiting cancer proliferation, migration and invasion

OBJECTIVE

Sirtuins family are defined as class III histone deacetylases (HDACs). Recently, mammalian silent information regulator two 4 (SIRT4) has been reported to be a tumor suppressor gene in multiple cancers. The objective of the present study was to explore the potential role of SIRT4 in clear cell renal cell carcinoma (ccRCC).

METHODS

We estimated SIRT4 expression levels in ccRCC and its adjacent non-neoplastic tissue by Western blotting (WB), quantitative real-time polymerase chain reaction (qRT-PCR) and bioinformatics data, the clinical and survival data were also collected and analyzed. In vitro study, ccRCC cell lines were transfected with SIRT4-siRNA or lentivirus to downregulate or overexpress the expression level of SIRT4. Then, the proliferation capacity of tumor cell was assessed by 5-Ethynyl-2'-deoxyuridine (EDU) assay, cell migration and invasion capacity were assessed by Transwell assays.

RESULTS

Our results indicated that the expression level of SIRT4 in ccRCC was significantly lower than the corresponding normal tissues (P< 0.001). Meanwhile, bioinformatics data and the result of WB showed that low SIRT4 expression level was obviously involved with poor overall survival and advanced tumor stage in ccRCC patients. Biological experiments demonstrated that overexpression of SIRT4 significantly reduced the proliferation, migration and invasion ability of ccRCC cells. Conversely, downregulation of SIRT4 enhanced the proliferation, migration and invasion ability of ccRCC cells.

CONCLUSIONS

These findings support that SIRT4 acts as a tumor suppressor in ccRCC and might be a novel biomarker and new therapeutic target for ccRCC.

Mitochondrial sirtuins in stem cells and cancer

The mammalian sirtuin family consists of seven proteins, three of which (SIRT3, SIRT4, and SIRT5) localise specifically within mitochondria and preserve mitochondrial function and homeostasis. Mitochondrial sirtuins are involved in diverse functions such as deacetylation, ADP-ribosylation, demalonylation and desuccinylation, thus affecting various aspects of cell fate. Intriguingly, mitochondrial sirtuins are able to manage these delicate processes with accuracy mediated by crosstalk between the nucleus and mitochondria. Previous studies have provided ample information about their substrates and targets, whereas less is known about their role in cancer and stem cells. Here, we review and discuss recent advances in our understanding of the structural and functional properties of mitochondrial sirtuins, including their targets in cancer and stem cells. These advances could help to improve the understanding of their interplay with signalling cascades and pathways, leading to new avenues for developing novel drugs for sirtuin-related disease treatments. We also highlight the complex network of mitochondrial sirtuins in cancer and stem cells, which may be important in deciphering the molecular mechanism for their activation and inhibition.

Sirtuins-The New Important Players in Women's Gynecological Health

The participation of sirtuins in the regulation of oxidative stress and inflammation lies at the basis of their possible modes of action and is related to their expression in various cell structures; their location in the mitochondria and blood plasma has been indicated as of primary importance. Despite many existing studies, research on sirtuins continues to present an opportunity to discover new functions and dependencies, especially when it comes to women's gynecological health. Sirtuins have a significant role in both the formation and the course of many gynecological diseases. Their role is particularly important and well documented in the course of the development of cancer within the female reproductive organs; however, disturbances observed in the ovary and oocyte as well as in follicular fluid are also widely investigated. Additionally, sirtuins take part in some gynecological disturbances as regulative factors in pathways associated with insulin resistance, glucose and lipids metabolism disorders. In this review, we would like to summarize the existing knowledge about sirtuins in the manner outlined above.

Research Progress of Sirtuin4 in Cancer

Sirtuins (SIRTs) are members of the silent information regulator-2 family. They are a conserved family of nicotinamide adenine dinucleotide-dependent protein lysine deacylases. SIRTS are involved in intricate cellular processes. There are seven subtypes of SIRTs (1–7) in mammals. SIRT4 is located mainly in mitochondria and has various catalytic activities. These enzyme activities give it a diverse range of important biologic functions, such as energy metabolism, oxidative stress, and aging. Cancer is characterized as reprogramming of energy metabolism and redox imbalance, and SIRT4 can affect tumorigenesis. Here, we review the structure, localization, and enzyme activity of SIRT4 and its role in various neoplasms.

Functions of mammalian SIRT4 in cellular metabolism and research progress in human cancer

Sirtuins are mammalian homologs of yeast silent information regulator two (SIRT) and are a highly conserved family of proteins, which act as nicotinamide adenine dinucleotide (NAD⁺)-dependent histone deacetylases. The seven sirtuins (SIRT1-7) share a conserved catalytic core domain; however, they have different enzyme activities, biological functions, and subcellular localizations. Among them, mitochondrial SIRT4 possesses ADP-ribosyltransferase, NAD⁺-dependent deacetylase, lipoamidase, and long-chain deacylase activities and can modulate the function of substrate proteins via ADP-ribosylation, delipoylation, deacetylation and long-chain deacylation. SIRT4 has been shown to play a crucial role in insulin secretion, fatty acid oxidation, amino acid metabolism, ATP homeostasis, apoptosis, neurodegeneration, and cardiovascular diseases. In addition, recent studies have demonstrated that SIRT4 acts as a tumor suppressor. Here, the present review summarizes the enzymatic activities and biological functions of SIRT4, as well as its roles in cellular metabolism and human cancer, which are described in the current literature.

Gene expression and prognosis of sirtuin family members in ovarian cancer

Sirtuins (SIRTs), a class of nicotinamide-adenine dinucleotide (NAD)+-dependent deacetylases, involve in modulating carcinogenesis and progression of various malignancies through their regulation of the cancer metabolism. However, the expression profiles and prognostic roles of SIRTs in ovarian cancer (OC) remain unclear. We underscore the transcriptional expression and prognostic significance of SIRTs in OC patients using online databases. Gene Expression Profiling Interactive analysis (GEPIA) was applied to analyze mRNA expression, and Kaplan-Meier plotter was used to evaluate prognostic value. In patients with OC, SIRT1/2/3 were significantly down-regulated, while rest of SIRTs were not significantly changed. High SIRT2/5/6/7 expression was correlated with favorable overall survival (OS), while high SIRT1/4 expression was correlated with poor OS. Additionally, aberrant SIRTs mRNA levels were related to the prognosis of OC patients with different clinicopathological characteristics. This is the first study to integrate bioinformatics approaches intended to identify the expression profiles and prognostic value of SIRTs in OC. These results suggest that SIRTs is related to the prognosis of OC and may be the potential therapeutic interventions in OC.

Sirt4: A Multifaceted Enzyme at the Crossroads of Mitochondrial Metabolism and Cancer

Sirtuins are NAD⁺-dependent deacylases that play crucial roles in the regulation of cellular metabolism, and as a result, are implicated in several diseases. The mitochondrial sirtuin Sirt4, for a long time considered as mainly a mono-ADP-ribosyltransferase, recently has shown a robust deacylase activity in addition to the already accepted substrate-dependent lipoamidase and deacetylase properties. Through these and likely other enzymatic and non-enzymatic activities, Sirt4 closely controls various metabolic events, and its dysregulation is linked to various aging-related disorders, including type 2 diabetes, cardiac hypertrophy, non-alcoholic fatty liver disease, obesity, and cancer. For its capability to inhibit glutamine catabolism and for the modulation of genome stability in cancer cells in response to different DNA-damaging conditions, Sirt4 is proposed as either a mitochondrial tumor suppressor or a tumor-promoting protein in a context-dependent manner. In addition to what is already known about the roles of Sirt4 in different biological settings, further studies are certainly still needed in order to validate this enzyme as a new potential target for various aging diseases.

Epigenetic Dysregulation at the Crossroad of Women's Cancer

An increasingly number of women of all age groups are affected by cancer, despite substantial progress in our understanding of cancer pathobiology, the underlying genomic alterations and signaling cascades, and cellular-environmental interactions. Though our understanding of women’s cancer is far more complete than ever before, there is no comprehensive model to explain the reasons behind the increased incidents of certain reproductive cancer among older as well as younger women. It is generally suspected that environmental and life-style factors affecting hormonal and growth control pathways might help account for the rise of women’s cancers in younger age, as well, via epigenetic mechanisms. Epigenetic regulators play an important role in orchestrating an orderly coordination of cellular signals in gene activity in response to upstream signaling and/or epigenetic modifiers present in a dynamic extracellular milieu. Here we will discuss the broad principles of epigenetic regulation of DNA methylation and demethylation, histone acetylation and deacetylation, and RNA methylation in women’s cancers in the context of gene expression, hormonal action, and the EGFR family of cell surface receptor tyrosine kinases. We anticipate that a better understanding of the epigenetics of women’s cancers may provide new regulatory leads and further fuel the development of new epigenetic biomarkers and therapeutic approaches.

Mitochondrial Function, Metabolic Regulation, and Human Disease Viewed through the Prism of Sirtuin 4 (SIRT4) Functions

As cellular metabolic hubs, mitochondria are the main energy producers for the cell. These organelles host essential energy producing biochemical processes, including the TCA cycle, fatty acid oxidation, and oxidative phosphorylation. An accumulating body of literature has demonstrated that a majority of mitochondrial proteins are decorated with diverse posttranslational modifications (PTMs). Given the critical roles of these proteins in cellular metabolic pathways and response to environmental stress or pathogens, understanding the role of PTMs in regulating their functions has become an area of intense investigation. A major family of enzymes that regulate PTMs within the mitochondria are sirtuins (SIRTs). Albeit until recently the least understood sirtuin, SIRT4 has emerged as an enzyme capable of removing diverse PTMs from its substrates, thereby modulating their functions. SIRT4 was shown to have ADP-ribosyltransferase, deacetylase, lipoamidase, and deacylase enzymatic activities. As metabolic dysfunction is linked to human disease, SIRT4 levels and activities have been implicated in modulating susceptibility to hyperinsulinemia and diabetes, liver disease, cancer, neurodegeneration, heart disease, aging, and pathogenic infections. Therefore, SIRT4 has emerged as a possible candidate for targeted therapeutics. Here, we discuss the diverse enzymatic activities and substrates of SIRT4 and its roles in human health and disease.

Sirtuin-4 (SIRT4), a therapeutic target with oncogenic and tumor-suppressive activity in cancer

Several members of the sirtuin (SIRT) family, a highly conserved family of NAD⁺-dependent enzymes, have been shown to play a critical role in both promoting and/or suppressing tumorigenesis. In this study, recent progress in the field concerning SIRT4 and cancer was reviewed, and the relationship between SIRT4 and tumors was investigated. Subsequently, we evaluated the role of SIRT4 with oncogenic or tumor-suppressive activity in cancer, which may provide insight in identifying the underlying mechanism of action of SIRT4 in cancer. Finally, we explored the potential of SIRT4 as a therapeutic target in cancer therapy.

Knockout of SIRT4 decreases chemosensitivity to 5-FU in colorectal cancer cells

Previous studies demonstrated that sirtuin (SIRT) 4 is aberrantly expressed in human malignant tumors and is associated with poor prognosis in patients with colorectal cancer. However, the role of SIRT4 in the progression of human colorectal cancer (CRC) and in chemotherapy remains unclear. In the present study, the expression of SIRT4 in CRC tissues and the effect of SIRT4 on colorectal cancer proliferation, migration and invasion was investigated. Additionally, the effects of SIRT4 on the chemosensitivity in colorectal cancer cells and the underlying molecular mechanisms were also explored. The results demonstrated that SIRT4 expression is significantly downregulated in CRC tissues and cell lines. Downregulation of SIRT4 significantly increased tumor proliferation, migration and invasion. Additionally, downregulation of SIRT4 decreased the chemosensitivity of CRC cells by inhibiting cell apoptosis. Thus, these results suggest that SIRT4 may be a promising therapeutic target in CRC.