Overexpression of SIRT4 inhibits the proliferation of gastric cancer cells through cell cycle arrest

Targeting sirtuins for cancer therapy: epigenetics modifications and beyond

Sirtuins (SIRTs) are well-known as nicotinic adenine dinucleotide+(NAD+)-dependent histone deacetylases, which are important epigenetic enzymes consisting of seven family members (SIRT1-7). Of note, SIRT1 and SIRT2 are distributed in the nucleus and cytoplasm, while SIRT3, SIRT4 and SIRT5 are localized in the mitochondria. SIRT6 and SIRT7 are distributed in the nucleus. SIRTs catalyze the deacetylation of various substrate proteins, thereby modulating numerous biological processes, including transcription, DNA repair and genome stability, metabolism, and signal transduction. Notably, accumulating evidence has recently underscored the multi-faceted roles of SIRTs in both the suppression and progression of various types of human cancers. Crucially, SIRTs have been emerging as promising therapeutic targets for cancer therapy. Thus, in this review, we not only present an overview of the molecular structure and function of SIRTs, but elucidate their intricate associations with oncogenesis. Additionally, we discuss the current landscape of small-molecule activators and inhibitors targeting SIRTs in the contexts of cancer and further elaborate their combination therapies, especially highlighting their prospective utility for future cancer drug development.

Sirtuin insights: bridging the gap between cellular processes and therapeutic applications

The greatest challenges that organisms face today are effective responses or detection of life-threatening environmental changes due to an obvious semblance of stress and metabolic fluctuations. These are associated with different pathological conditions among which cancer is most important. Sirtuins (SIRTs; NAD+-dependent enzymes) are versatile enzymes with diverse substrate preferences, cellular locations, crucial for cellular processes and pathological conditions. This article describes in detail the distinct roles of SIRT isoforms, unveiling their potential as either cancer promoters or suppressors and also explores how both natural and synthetic compounds influence the SIRT function, indicating promise for therapeutic applications. We also discussed the inhibitors/activators tailored to specific SIRTs, holding potential for diseases lacking effective treatments. It may uncover the lesser-studied SIRT isoforms (e.g., SIRT6, SIRT7) and their unique functions. This article also offers a comprehensive overview of SIRTs, linking them to a spectrum of diseases and highlighting their potential for targeted therapies, combination approaches, disease management, and personalized medicine. We aim to contribute to a transformative era in healthcare and innovative treatments by unraveling the intricate functions of SIRTs.

SIRT4 as a novel interactor and candidate suppressor of C-RAF kinase in MAPK signaling

Cellular responses leading to development, proliferation, and differentiation depend on RAF/MEK/ERK signaling, which integrates and amplifies signals from various stimuli for downstream cellular responses. C-RAF activation has been reported in many types of tumor cell proliferation and developmental disorders, necessitating the discovery of potential C-RAF protein regulators. Here, we identify a novel and specific protein interaction between C-RAF among the RAF kinase paralogs, and SIRT4 among the mitochondrial sirtuin family members SIRT3, SIRT4, and SIRT5. Structurally, C-RAF binds to SIRT4 through the N-terminal cysteine-rich domain, whereas SIRT4 predominantly requires the C-terminus for full interaction with C-RAF. Interestingly, SIRT4 specifically interacts with C-RAF in a pre-signaling inactive (serine 259-phosphorylated) state. Consistent with this finding, the expression of SIRT4 in HEK293 cells results in an up-regulation of pS259-C-RAF levels and a concomitant reduction in MAPK signaling as evidenced by strongly decreased phospho-ERK signals. Thus, we propose an additional extra-mitochondrial function of SIRT4 as a cytosolic tumor suppressor of C-RAF-MAPK signaling, besides its metabolic tumor suppressor role of glutamate dehydrogenase and glutamate levels in mitochondria.

Decoding dynamic miRNA:ceRNA interactions unveils therapeutic insights and targets across predominant cancer landscapes

Competing endogenous RNAs play key roles in cellular molecular mechanisms through cross-talk in post-transcriptional interactions. Studies on ceRNA cross-talk, which is particularly dependent on the abundance of free transcripts, generally involve large- and small-scale studies involving the integration of transcriptomic data from tissues and correlation analyses. This abundance-dependent nature of ceRNA interactions suggests that tissue- and condition-specific ceRNA dynamics may fluctuate. However, there are no comprehensive studies investigating the ceRNA interactions in normal tissue, ceRNAs that are lost and/or appear in cancerous tissues or their interactions. In this study, we comprehensively analyzed the tumor-specific ceRNA fluctuations observed in the three highest-incidence cancers, LUAD, PRAD, and BRCA, compared to healthy lung, prostate, and breast tissues, respectively. Our observations pertaining to tumor-specific competing endogenous RNA (ceRNA) interactions revealed that, in the cases of lung adenocarcinoma (LUAD), prostate adenocarcinoma (PRAD), and breast invasive carcinoma (BRCA), 3,204, 1,233, and 406 ceRNAs, respectively, engage in post-transcriptional intercommunication within tumor tissues, in contrast to their absence in corresponding healthy samples. We also found that 90 ceRNAs are shared by the three cancer types and that these ceRNAs participate in ceRNA interactions in tumor tissues compared to those in normal tissues. Among the 90 ceRNAs that directly interact with miRNAs, we uncovered a core network of 165 miRNAs and 63 ceRNAs that should be considered in RNA-targeted and RNA-mediated approaches in future studies and could be used in these three aggressive cancer types. More specifically, in this core interaction network, ceRNAs such as GALNT7, KLF9, and DAB2 and miRNAs like miR-106a/b-5p, miR-20a-5p, and miR-519d-3p may have potential as common targets in the three critical cancers. In contrast to conventional methods that construct ceRNA networks using differentially expressed genes compared to normal tissues, our proposed approach identifies ceRNA players by considering their context within the ceRNA:miRNA interactions. Our results have the potential to reveal distinct and common ceRNA interactions in cancer types and to pinpoint critical RNAs, thereby paving the way for RNA-based strategies in the battle against cancer.

SIRT4 in ageing

Ageing is a phenomenon in which cells, tissues and organs undergo systemic pathological changes as individuals age, leading to the occurrence of ageing-related diseases and the end of life. It is associated with many phenotypes known as ageing characteristics, such as genomic instability, nutritional imbalance, mitochondrial dysfunction, cell senescence, stem cell depletion, and an altered microenvironment. The sirtuin family (SIRT), known as longevity proteins, is thought to delay ageing and prolong life, and mammals, including humans, have seven family members (SIRT1-7). SIRT4 has been studied less among the sirtuin family thus far, but it has been reported that it has important physiological functions in organisms, such as promoting DNA damage repair, participating in the energy metabolism of three substances, inhibiting inflammatory reactions and apoptosis, and regulating mitochondrial function. Recently, some studies have demonstrated the involvement of SIRT4 in age-related processes, but knowledge in this field is still scarce. Therefore, this review aims to analyse the relationship between SIRT4 and ageing characteristics as well as some age-related diseases (e.g., cardiovascular diseases, metabolic diseases, neurodegenerative diseases and cancer).

Shedding light on structure, function and regulation of human sirtuins: a comprehensive review

Sirtuins play an important role in signalling pathways associated with various metabolic regulations. They possess mono-ADP-ribosyltransferase or deacylase activity like demalonylase, deacetylase, depalmitoylase, demyristoylase and desuccinylase activity. Sirtuins are histone deacetylases which depends upon nicotinamide adenine dinucleotide (NAD) that deacetylate lysine residues. There are a total of seven human sirtuins that have been identified namely, SIRT1, SIRT2, SIRT3, SIRT4, SIRT5, SIRT6 and SIRT7. The subcellular location of mammalian sirtuins, SIRT1, SIRT6, and SIRT7 are in the nucleus; SIRT3, SIRT4, and SIRT5 are in mitochondria, and SIRT2 is in cytoplasm. Structurally sirtuins contains a N-terminal, a C-terminal and a Zn+ binding domain. The sirtuin family has been found to be crucial for maintaining lipid and glucose homeostasis, and also for regulating insulin secretion and sensitivity, DNA repair pathways, neurogenesis, inflammation, and ageing. Based on the literature, sirtuins are overexpressed and play an important role in tumorigenicity in various types of cancer such as non-small cell lung cancer, colorectal cancer, etc. In this review, we have discussed about the different types of human sirtuins along with their structural and functional features. We have also discussed about the various natural and synthetic regulators of sirtuin activities like resveratrol. Our overall study shows that the correct regulation of sirtuins can be a good target for preventing and treating various diseases for improving the human lifespan. To investigate the true therapeutic potential of sirtuin proteins and their efficacy in a variety of pathological diseases, a better knowledge of the link between the structure and function of sirtuin proteins would be necessary.

Sirtuins (SIRTs) As a Novel Target in Gastric Cancer

Gastric cancer is a major health burden worldwide. Among all neoplasms, gastric cancer is the fifth most common and the third most deadly type of cancer. It is known that sirtuins (SIRTs), are NAD⁺-dependent histone deacetylases regulating important metabolic pathways. High expression of SIRTs in the human body can regulate metabolic processes; they prevent inflammation but also resist cell death and aging processes. The seven members of this family enzymes can also play a fundamental role in process of carcinogenesis by influencing cell viability, apoptosis and metastasis. This review collects and discusses the role of all seven sirtuins (SIRT1-SIRT7) in the pathogenesis of gastric cancer (GC).

Histone Deacetylase Functions in Gastric Cancer: Therapeutic Target?

Gastric cancer (GC) is one of the most aggressive cancers. Therapeutic treatments are based on surgery combined with chemotherapy using a combination of platinum-based agents. However, at metastatic stages of the disease, survival is extremely low due to late diagnosis and resistance mechanisms to chemotherapies. The development of new classifications has not yet identified new prognostic markers for clinical use. The studies of epigenetic processes highlighted the implication of histone acetylation status, regulated by histone acetyltransferases (HATs) and by histone deacetylases (HDACs), in cancer development. In this way, inhibitors of HDACs (HDACis) have been developed and some of them have already been clinically approved to treat T-cell lymphoma and multiple myeloma. In this review, we summarize the regulations and functions of eighteen HDACs in GC, describing their known targets, involved cellular processes, associated clinicopathological features, and impact on survival of patients. Additionally, we resume the in vitro, pre-clinical, and clinical trials of four HDACis approved by Food and Drug Administration (FDA) in cancers in the context of GC.

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.

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.

Loss of SIRT4 promotes the self-renewal of Breast Cancer Stem Cells

Rationale: It has been proposed that cancer stem/progenitor cells (or tumor-initiating cells, TICs) account for breast cancer initiation and progression. Sirtuins are nicotinamide adenine dinucleotide (NAD+)-dependent class-III histone deacetylases and mediate various basic biological processes, including metabolic homeostasis. However, interplay and cross-regulation among the sirtuin family are not fully understood. As one of the least studied sirtuin family members, the mitochondrial sirtuin SIRT4 is a tumor suppressor gene in various cancers. However, its role in cancer stemness, as well as initiation and progression of breast cancer, remains unknown. Methods: The expression of SIRT4 in breast cancer was analyzed using the TCGA breast cancer database and 3 GSEA data. Normal breast epithelial cells MCF10A and breast cancer cell lines MCF-7, MDA-MB-231, BT549, MDA-MB-468 were used to establish SIRT4 gene knockdown and corresponding overexpression cells. Identified MTT cytotoxicity assays, cell invasion and motility assay, sorting of SP, confocal immunofluorescence microscopy, mouse mammary stem cell analysis, glutamine and glucose production, clonogenic and sphere-formation assay, mass spectrometric metabolomics analysis and ChIP-seq to further explore SIRT4 biological role in breast cancer. Results: We elucidated a novel role for SIRT4 in the negative regulation of mammary gland development and stemness, which is related to the mammary tumorigenesis. We also uncovered an inverse correlation between SIRT4 and SIRT1. Most importantly, SIRT4 negatively regulates SIRT1 expression via repressing glutamine metabolism. Besides, we identified H4K16ac and BRCA1 as new prime targets of SIRT4 in breast cancer. Conclusions: These results demonstrate that SIRT4 exerts its tumor-suppressive activity via modulating SIRT1 expression in breast cancer and provide a novel cross-talk between mitochondrial and nuclear sirtuins.

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.

Associations of sirtuins with clinicopathological variables and prognosis in human ovarian cancer

Ovarian cancer (OC) is the fifth most frequent cause of cancer-associated mortality worldwide, and is accompanied by asymptomatic progression. Sirtuins (SIRTs) are a family of nicotinamide adenine dinucleotide-dependent protein deacetylases, comprising seven members (SIRT1, SIRT2, SIRT3, SIRT4, SIRT5, SIRT6 and SIRT7). Accumulating evidence has demonstrated that SIRTs act as prognostic estimators in certain types of cancer such as lung cancer, prostate cancer, gastric cancer, breast cancer and colorectal cancer. However, it remains unknown whether individual SIRTs can serve as independent prognostic factors in OC. In the present study, the Kaplan-Meier plotter online database was utilized to examine the prognostic values of SIRT mRNA expression in patients with OC. The results demonstrated that the overexpression of SIRT3, SIRT5, SIRT6 and SIRT7 mRNAs was associated with a good prognosis in patients, whereas elevated mRNA levels of SIRT1 and SIRT4 indicated poor survival in patients with OC. In addition, among the favorable predictors, SIRT3, SIRT5, SIRT6 and SIRT7 overexpression were associated with overall survival (OS), according to clinical characteristics, such as histological classification, clinical stage, pathology grade, drug therapy and tumor protein p53 mutation status in patients with OC. Similarly, SIRT4 mRNA overexpression was associated with poor OS in pathological grade III cancer. High SIRT1 and SIRT4 expression were associated with unfavorable OS at all clinical stages. Furthermore, SIRT1 and SIRT4 were negatively associated with OS in drug-treated patients. In summary, the present study demonstrated that the SIRT family is associated with the prognosis of human OC, suggesting that individual SIRTs may also act as prognostic predictors in 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.

Histone Deacetylases and their Inhibitors in Cancer Epigenetics

Histone deacetylases (HDAC) and histone deacetylase inhibitors (HDACi) have greatly impacted the war on cancer. Their role in epigenetics has significantly altered the development of anticancer drugs used to treat the most rare, persistent forms of cancer. During transcription, HDAC and HDACi are used to regulate the genetic mutations found in cancerous cells by removing and/or preventing the removal of the acetyl group on specific histones. This activity determines the relaxed or condensed conformation of the nucleosome, changing the accessibility zones for transcription factors. These modifications lead to other biological processes for the cell, including cell cycle progression, proliferation, and differentiation. Each HDAC and HDACi class or group has a distinctive mechanism of action that can be utilized to halt the progression of cancerous cell growth. While the use of HDAC- and HDACi-derived compounds are relatively new in treatment of cancers, they have a proven efficacy when the appropriately utilized. This following manuscript highlights the mechanisms of action utilized by HDAC and HDACi in various cancer, their role in epigenetics, current drug manufacturers, and the impact predicative modeling systems have on cancer therapeutic drug discovery.

SIRT4 enhances the sensitivity of ER-positive breast cancer to tamoxifen by inhibiting the IL-6/STAT3 signal pathway

Recent advances in endocrine therapy have improved the prospects for estrogen receptor‐positive breast cancer. Tamoxifen is an effective drug for patients with estrogen receptor‐positive breast cancer, but the development of resistance is common. Therefore, discovering ways to enhance the sensitivity of cancer cells to tamoxifen may help improve breast cancer treatment. We studied the biological role of sirtuin 4 (SIRT4) in tamoxifen‐treated MCF7 and T47D cells. The levels of the MYC proto‐oncogene (MYC) and cyclin D1 (CCND1) were detected by western blotting and quantitative reverse transcription‐polymerase chain reaction in breast cancer cells with SIRT4 overexpression or depletion. Immunofluorescence and western blotting were used to assess the phosphorylation status of signal transducer and activator of transcription 3 (STAT3). SIRT4 overexpression decreased the half maximal inhibitory concentration of tamoxifen in MCF7 and T47D cells, while its depletion increased it. Thus, SIRT4 enhances the sensitivity of breast cancer cells to tamoxifen. Moreover, western blotting revealed decreased STAT3 phosphorylation after SIRT4 transfection. The transcription and translation of MYC and CCND1, target genes of the STAT3 pathway, were also blocked. Immunofluorescence revealed that pathway activation and nuclear STAT4 translocation were suppressed when SIRT4 was overexpressed. Furthermore, the effects of SIRT4 overexpression or depletion on proliferation could be offset by STAT3 activation or inhibition. Taken together, these results demonstrate that SIRT4 enhances the tamoxifen sensitivity of breast cancer cells by inhibiting the STAT3 signaling pathway. With this knowledge, therapeutic strategies with reduced drug resistance risk may be developed.