SIRT1 regulates Dishevelled proteins and promotes transient and constitutive Wnt signaling. Proc Natl Acad Sci U S A. 2010;107:9216-9221. [PMID: 20439735 DOI: 10.1073/pnas.0911325107]

DVL/GSK3/ISL1 pathway signaling: unraveling the mechanism of SIRT3 in neurogenesis and AD therapy

BACKGROUND

The established association between Alzheimer's disease (AD) and compromised neural regeneration is well-documented. In addition to the mitigation of apoptosis in neural stem cells (NSCs), the induction of neurogenesis has been proposed as a promising therapeutic strategy for AD. Our previous research has demonstrated the effective inhibition of NSC injury induced by microglial activation through the repression of oxidative stress and mitochondrial dysfunction by Sirtuin 3 (SIRT3). Nonetheless, the precise role of SIRT3 in neurogenesis remains incompletely understood.

METHODS

In vivo, SIRT3 overexpression adenovirus was firstly injected by brain stereotaxic localization to affect the hippocampal SIRT3 expression in APP/PS1 mice, and then behavioral experiments were performed to investigate the cognitive improvement of SIRT3 in APP/PS1 mice, as well as neurogenic changes in hippocampal region by immunohistochemistry and immunofluorescence. In vitro, under the transwell co-culture condition of microglia and neural stem cells, the mechanism of SIRT3 improving neurogenesis of neural stem cells through DVL/GSK3/ISL1 axis was investigated by immunoblotting, immunofluorescence and other experimental methods.

RESULTS

Our findings indicate that the overexpression of SIRT3 in APP/PS1 mice led to enhanced cognitive function and increased neurogenesis. Additionally, SIRT3 was observed to promote the differentiation of NSCs into neurons during retinoic acid (RA)-induced NSC differentiation in vitro, suggesting a potential role in neurogenesis. Furthermore, we observed the activation of the Wnt/ß-catenin signaling pathway during this process, with Glycogen Synthase Kinase-3a (GSK3a) primarily governing NSC proliferation and GSK3ß predominantly regulating NSC differentiation. Moreover, the outcomes of our study demonstrate that SIRT3 exerts a protective effect against microglia-induced apoptosis in neural stem cells through its interaction with DVLs.

CONCLUSIONS

Our results show that SIRT3 overexpressing APP/PS1 mice have improved cognition and neurogenesis, as well as improved neurogenesis of NSC in microglia and NSC transwell co-culture conditions through the DVL/GSK3/ISL1 axis.

miR-29a-SIRT1-Wnt/β-Catenin Axis Regulates Tumor Progression and Survival in Hepatocellular Carcinoma

Sirtuin 1 (SIRT1) participates in the initiation and evolution of hepatocellular carcinoma (HCC). However, the specific mechanism of SIRT1 in HCC remains unclear. The mRNA expression of miR-29a in HCC were identified by qRT-PCR. miR-29a mimic and inhibitor were employed. The alteration of biological behavior was evaluated by Cell Counting Kit-8 (CCK8), clone formation, transwell and wound-healing assay. SIRT1 was verified to be a target gene which directly regulated by miR-29a. Luciferase reporter assay and co-IP were employed to evaluate the direct binding of miR-29a and SIRT1. Animal model was used to evaluate its function on tumor growth and metastasis in vivo. The relationship between miR-29a/SIRT1 and prognosis of HCC patients was analyzed. SIRT1 overexpression accompanied by low expression of miR-29a were detected in HCC which was negatively correlated, and associated with overall survival, vascular invasion and TNM stage. Up-regulation of miR-29a suppressed cell growth and motility. Deprivation of miR-29a expression led to opposite effect. The direct binding of miR-29a to SIRT1 was confirmed by luciferase reporter assay and co-IP. miR-29a repressed SIRT1, DKK2 and β-catenin, but their expression was obviously elevated by miR-29a inhibitor. Animal model suggested miR-29a could reduce the expression of SIRT1, thereby inhibiting HCC growth and metastasis by inactivating Wnt/β-catenin pathway. Low expression of miR-29a and high expression of SIRT1 predicted shorter survival time in HCC patients. miR-29a had the function of tumor suppressor which directly inhibited oncogenic SIRT1. The loss of miR-29a led to up-regulation of SIRT1, aggravate malignant transformation and poor prognosis of HCC.

The role of resveratrol in neurogenesis: a systematic review

CONTEXT

Resveratrol (RV) is a natural compound found in grapes, wine, berries, and peanuts and has potential health benefits-namely, neurogenesis improvement. Neurogenesis, which is the process through which new neurons or nerve cells are generated in the brain, occurs in the subventricular zone and hippocampus and is influenced by various factors. RV has been shown to increase neural stem cell proliferation and survival, improving cognitive function in hippocampus-dependent tasks. Thus, to provide a convergent and unbiased conclusion of the available evidence on the correlation between the RV and neurogenesis, a systematic review needs to be undertaken meticulously and with appropriate attention.

OBJECTIVE

This study aimed to systematically review any potential connection between the RV and neurogenesis in animal models.

DATA SOURCES AND EXTRACTION

Based on the particular selection criteria, 8 original animal studies that investigated the relationship between RV and neurogenesis were included. Studies written in English and published in peer-reviewed journals with no restrictions on the starting date of publication on August 17, 2023, were searched in the Google Scholar and PubMed databases. Furthermore, data were extracted and analyzed independently by 2 researchers and then reviewed by a third researcher, and discrepancies were resolved by consensus. This project followed PRISMA reporting standards.

DATA ANALYSIS

In the studies analyzed in this review, there is a definite correlation between RV and neurogenesis, meaning that RV intake, irrespective of the mechanisms thereof, can boost neurogenesis in both the subventricular zone and hippocampus.

CONCLUSION

This finding, albeit with some limitations, provides a plausible indication of RV's beneficial function in neurogenesis. Indeed, RV intake may result in neurogenesis benefits-namely, cognitive function, mood regulation, stress resilience, and neuroprotection, potentially preventing cognitive decline.

Targeting signaling pathways in cancer stem cells: A potential approach for developing novel anti-cancer therapeutics

Cancer stem cells (CSCs) have emerged as prime players in the intricate landscape of cancer development, progression, and resistance to traditional treatments. These unique cellular subpopulations own the remarkable capability of self-renewal and differentiation, giving rise to the diverse cellular makeup of tumors and fostering their recurrence following conventional therapies. In the quest for developing more effective cancer therapeutics, the focus has now shifted toward targeting the signaling pathways that govern CSCs behavior. This chapter underscores the significance of these signaling pathways in CSC biology and their potential as pivotal targets for the development of novel chemotherapy approaches. We delve into several key signaling pathways essential for maintaining the defining characteristics of CSCs, including the Wnt, Hedgehog, Notch, JAK-STAT, NF-κB pathways, among others, shedding light on their potential crosstalk. Furthermore, we highlight the latest advancements in CSC-targeted therapies, spanning from promising preclinical models to ongoing clinical trials. A comprehensive understanding of the intricate molecular aspects of CSC signaling pathways and their manipulation holds the prospective to revolutionize cancer treatment paradigms. This, in turn, could lead to more efficacious and personalized therapies with the ultimate goal of eradicating CSCs and enhancing overall patient outcomes. The exploration of CSC signaling pathways represents a key step towards a brighter future in the battle against cancer.

Adiponectin overexpression promotes fracture healing through regulating the osteogenesis and adipogenesis balance in osteoporotic mice

INTRODUCTION

Osteoporosis invariably manifests as loss of bone, which is replaced by adipose tissue; this can easily lead to fractures, accompanied by delayed and poor healing. Adiponectin (APN) balances osteogenesis and adipogenesis in bone marrow mesenchymal stem cells (BMSCs). Therefore, this study explored whether adiponectin promotes bone fracture healing by regulating the balance between osteogenesis and adipogenesis.

MATERIALS AND METHODS

We used adenovirus overexpression vectors carrying APN (Ad-APN-GFP) to treat ovariectomized (OVX) mouse BMSCs and osteoporotic bone fractures to investigate the role of APN in bone microenvironment metabolism in osteoporotic fractures. We subsequently established an OVX mice and bone fracture model using Ad-APN-GFP treatment to investigate whether APN could promote bone fracture healing in osteoporotic mice.

RESULTS

The experimental results showed that APN is a critical molecule in diverse differentiation directions in OVX mouse BMSCs, with pro-osteogenesis and anti-adipogenesis properties. Importantly, our study revealed that Ad-APN-GFP treatment facilitates bone generation and healing around the osteoporotic fracture ends. Moreover, we identified that Sirt1 and Wnt signaling were closely related to the pro-osteogenesis and anti-adipogenesis commitment of APN in OVX mouse BMSCs and femoral tissues.

CONCLUSION

We demonstrated that APN overexpression facilitates bone fracture healing in osteoporosis. Furthermore, APN overexpression promoted bone formation in OVX mouse BMSCs and bone fracture ends by regulating the balance between osteogenesis and adipogenesis both in vitro and in vivo.

Interactions between Intestinal Homeostasis and NAD+ Biology in Regulating Incretin Production and Postprandial Glucose Metabolism

The intestine has garnered attention as a target organ for developing new therapies for impaired glucose tolerance. The intestine, which produces incretin hormones, is the central regulator of glucose metabolism. Glucagon-like peptide-1 (GLP-1) production, which determines postprandial glucose levels, is regulated by intestinal homeostasis. Nicotinamide phosphoribosyltransferase (NAMPT)-mediated nicotinamide adenine dinucleotide (NAD⁺) biosynthesis in major metabolic organs such as the liver, adipose tissue, and skeletal muscle plays a crucial role in obesity- and aging-associated organ derangements. Furthermore, NAMPT-mediated NAD⁺ biosynthesis in the intestines and its upstream and downstream mediators, adenosine monophosphate-activated protein kinase (AMPK) and NAD⁺-dependent deacetylase sirtuins (SIRTs), respectively, are critical for intestinal homeostasis, including gut microbiota composition and bile acid metabolism, and GLP-1 production. Thus, boosting the intestinal AMPK-NAMPT-NAD⁺-SIRT pathway to improve intestinal homeostasis, GLP-1 production, and postprandial glucose metabolism has gained significant attention as a novel strategy to improve impaired glucose tolerance. Herein, we aimed to review in detail the regulatory mechanisms and importance of intestinal NAMPT-mediated NAD⁺ biosynthesis in regulating intestinal homeostasis and GLP-1 secretion in obesity and aging. Furthermore, dietary and molecular factors regulating intestinal NAMPT-mediated NAD⁺ biosynthesis were critically explored to facilitate the development of new therapeutic strategies for postprandial glucose dysregulation.

Targeting crosstalk of signaling pathways in cancer stem cells: a promising approach for development of novel anti-cancer therapeutics

Wnt, Hedgehog (Hh), and Notch signaling pathways are the evolutionarily conserved signaling pathways that regulate the embryonic development and also play crucial role in maintaining stemness properties of cancer stem cells (CSCs) and inducing epithelial-to-mesenchymal transition (EMT), metastasis, and angiogenesis. It has been highly challenging to inhibit the CSCs growth and proliferation as these are capable of evading chemotherapeutic drugs and cause cancer recurrence through multiple signaling pathways. Therefore, novel therapeutic strategies to target the key players involved in the crosstalk of these signaling pathways need to be developed. In this review, we have identified the interacting molecules of Wnt, Hh, and Notch pathways responsible for enhancing the malignant properties of CSCs. Analyzing the functions of these crosstalk molecules will help us to find an approach toward the development of new anti-cancer drugs for inhibition of CSCs growth and progression. Long non-coding RNAs (LncRNAs) play a significant role in various cellular processes, like chromatin remodeling, epigenetic modifications, transcriptional, and post-transcriptional regulations. Here, we have highlighted the research findings suggesting the involvement of LncRNAs in maintenance of the stemness properties of CSCs through modulation of the above-mentioned signaling pathways. We have also discussed about the different therapeutic approaches targeting those key players responsible for mediating the crosstalk between the pathways. Overall, this review article will surely help the cancer biologists to design novel anti-CSCs agents that will open up a new horizon in the field of anti-cancer therapeutics.

Resveratrol Mediated Regulation of Hippocampal Neuroregenerative Plasticity via SIRT1 Pathway in Synergy with Wnt Signaling: Neurotherapeutic Implications to Mitigate Memory Loss in Alzheimer's Disease

Alzheimer's disease (AD) is a major form of dementia. Abnormal amyloidogenic event-mediated degeneration of cholinergic neurons in the cognitive centers of the brain has been attributed to neuropathological sequelae and behavioral deficits in AD. Besides, impaired adult neurogenesis in the hippocampus has experimentally been realized as an underlying cause of dementia regardless of neurodegeneration. Therefore, nourishing the neurogenic process in the hippocampus has been considered an effective therapeutic strategy to mitigate memory loss. In the physiological state, the Wnt pathway has been identified as a potent mitogenic generator in the hippocampal stem cell niche. However, downstream components of Wnt signaling have been noticed to be downregulated in AD brains. Resveratrol (RSV) is a potent Sirtuin1 (SIRT1) enhancer that facilitates neuroprotection and promotes neurogenesis in the hippocampus of the adult brain. While SIRT1 is an important positive regulator of Wnt signaling, ample reports indicate that RSV treatment strongly mediates the fate determination of stem cells through Wnt signaling. However, the possible therapeutic roles of RSV-mediated SIRT1 enhancement on the regulation of hippocampal neurogenesis and reversal of memory loss through the Wnt signaling pathway have not been addressed yet. Taken together, this review describes RSV-mediated effects on the regulation of hippocampal neurogenesis via the activation of SIRT1 in synergy with the Wnt signaling. Further, the article emphasizes a hypothesis that RSV treatment can provoke the activation of quiescent neural stem cells and prime their neurogenic capacity in the hippocampus via Wnt signaling in AD.

SIRT1, a novel transcriptional downstream target of CD44, linking its deacetylase activity to tumor cell invasion/metastasis

Our tetracycline-off-inducible CD44 expression system previously established in mouse model, revealed that activation of CD44 with its major ligand hyaluronan (HA) promoted breast cancer (BC) metastasis to the liver. To identify the mechanisms that underpin CD44-promoted BC cell invasion, microarray gene expression profiling using RNA samples from (Tet)-Off-regulated expression system of CD44s in MCF7 cells, revealed a set of upregulated genes including, nuclear sirtuin-1 (SIRT1 also known as NAD-dependent deacetylase), an enzyme that requires NAD⁺ as a cofactor to deacetylate several histones and transcription factors. It stimulates various oncogenic pathways promoting tumorigenesis. This data suggests that SIRT1 is a potential novel transcriptional target of CD44-downstream signaling that promote BC cell invasion/metastasis. This review will discuss the evidence supporting this hypothesis as well as the mechanisms linking SIRT1 to cell proliferation and invasion.

Nuclear Dishevelled: An enigmatic role in governing cell fate and Wnt signaling

The Dishevelled gene was first identified in Drosophila mutants with disoriented hair and bristle polarity and subsequent work has now demonstrated its importance in critical and diverse aspects of biology. Since those early discoveries, Dishevelled has been shown to coordinate a plethora of developmental and cellular processes that range from controlling cell polarity during gastrulation to partnering with chromatin modifying enzymes to regulate histone methylation at genomic loci. While the role of DVL in development is well-respected and the cytosolic function of DVL has been studied more extensively, its nuclear role continues to remain murky. In this review we highlight some of the seminal discoveries that have contributed to the field, but the primary focus is to discuss recent advances with respect to the nuclear role of Dishevelled. This nuclear function of Dishevelled is a dimension which is proving to be increasingly important yet remains enigmatic.

SIRT4-Catalyzed Deacetylation of Axin1 Modulates the Wnt/β-Catenin Signaling Pathway

Axin1 is a fundamental scaffolding protein of the destruction complex in the canonical Wnt signaling pathway, which plays a critical role in various biological processes. However, how Axin1 is regulated in the activation of the canonical Wnt signaling pathway remains elusive. Here, we report that Axin1 is constitutively acetylated in resting cells. Upon stimulation with Wnt, SIRT4 translocates from mitochondria to the cytoplasm and catalyzes Axin1 deacetylation, thus turning off the destruction complex. In this process, Lys147, a residue in the RGS domain of Axin1, plays a key role. We proved that the Axin1-K147R mutant impairs the assembly of β-TrCP to the destruction complex, which leads to β-catenin accumulation even without Wnt stimulation. In summary, our work proposes a new model for better understanding the initial stage of the canonical Wnt signaling pathway in which SIRT4 translocates from mitochondria into the cytoplasm to deacetylate Axin1-K147 after Wnt stimulation, which results in reduced assembly of β-TrCP to the destruction complex.

Dishevelled-1 DIX and PDZ domain lysine residues regulate oncogenic Wnt signaling

DVL proteins are central mediators of the Wnt pathway and relay complex input signals into different branches of the Wnt signaling network. However, molecular mechanism(s) that regulate DVL-mediated relay of Wnt signals still remains unclear. Here, for the first time, we elucidate the functional significance of three DVL-1 lysines (K/Lys) which are subject to post-translational acetylation. We demonstrate that K34 Lys residue in the DIX domain regulates subcellular localization of β-catenin, thereby influencing downstream Wnt target gene expression. Additionally, we show that K69 (DIX domain) and K285 (PDZ domain) regulate binding of DVL-1 to Wnt target gene promoters and modulate expression of Wnt target genes including CMYC, OCT4, NANOG, and CCND1, in cell line models and xenograft tumors. Finally, we report that conserved DVL-1 lysines modulate various oncogenic functions such as cell migration, proliferation, cell-cycle progression, 3D-spheroid formation and in-vivo tumor growth in breast cancer models. Collectively, these findings highlight the importance of DVL-1 domain-specific lysines which were recently shown to be acetylated and characterize their influence on Wnt signaling. These site-specific modifications may be subject to regulation by therapeutics already in clinical use (lysine deacetylase inhibitors such as Panobinostat and Vorinostat) or may possibly have prognostic utility in translational efforts that seek to modulate dysfunctional Wnt signaling.

Epigenetic Regulation of the Wnt/β-Catenin Signaling Pathway in Cancer

Studies over the past four decades have elucidated the role of Wnt/β-catenin mediated regulation in cell proliferation, differentiation and migration. These processes are fundamental to embryonic development, regeneration potential of tissues, as well as cancer initiation and progression. In this review, we focus on the epigenetic players which influence the Wnt/β-catenin pathway via modulation of its components and coordinated regulation of the Wnt target genes. The role played by crosstalk with other signaling pathways mediating tumorigenesis is also elaborated. The Hippo/YAP pathway is particularly emphasized due to its extensive crosstalk via the Wnt destruction complex. Further, we highlight the recent advances in developing potential therapeutic interventions targeting the epigenetic machinery based on the characterization of these regulatory networks for effective treatment of various cancers and also for regenerative therapies.

Regulation of Dishevelled protein activity and stability by post-translational modifications and autophagy

As a key component of Wnt signaling, Dishevelled (Dvl/Dsh) plays essential roles in development processes and adult tissue homeostasis in multicellular organisms, and its deregulation results in human development disorders and other diseases. Dvl integrates and relays complex Wnt signals by acting as a branch-point of β-catenin-dependent canonical and β-catenin-independent noncanonical pathways. It dynamically interacts with multiple proteins to modulate Wnt signaling, while its activity and stability are tightly controlled by other proteins. This Review summarizes the current understanding of regulation of Dvl activity, localization, and stability by post-translational modifications, aggregation, and autophagy, and the impacts on Dvl function in both Wnt signaling and biological processes.

Suggested role of silent information regulator 1 (SIRT1) gene in female infertility: A cross-sectional study in Pakistan

AIM & OBJECTIVE

Silent information regulator 1 (SIRT1) gene stimulates the expression of antioxidants and repairs damaged cells. It affects the mitochondrial activity within the oocytes to overcome the oxidant stress. We aimed to assess an association of SIRT1 polymorphism (Tag SNPs rs10509291 and rs12778366) with fertility, and assess serum levels of follicle stimulating hormone (FSH), luteinizing hormone (LH), oestradiol, progesterone, manganese superoxide (MnSOD) and SIRT1.

MATERIAL AND METHODS

In this cross-sectional study, 207 fertile and 135 infertile subjects between the ages of 18-45 years were recruited. Polymerase chain reaction (PCR) was performed; products were electrophoresed in a 2% agarose gel. Descriptive analysis of continuous variables was expressed as mean ± standard deviation. Mann-Whitney test was performed for comparison of groups, P value <.001 was considered significant. Single Nucleotide Polymorphism (SNP) data were analysed by applying chi-squared statistics.

RESULTS

All subjects were age matched (P = .896). SIRT1 levels were significantly lower in infertile females when compared with fertile subjects (P < .001). AA (rs10509291) and CC (rs12778366) variant frequency was higher in the infertile than fertile subjects (P < .01). Similarly, the frequency of A allele (rs10509291) and C allele (rs12778366) was higher in infertile subjects (P < .001). Infertile females (29%) showed existence of SNP rs10509291 while 49% demonstrated genetic variation of rs12778366. MnSOD and SIRT1 levels were found to be lower in these subjects.

CONCLUSION

The presence of SIRT1 genetic variants (rs10509291 and rs12778366) apparently disturbs the expression of SIRT1 deteriorating mitochondrial antioxidant function within the oocytes, instigating oxidative stress within. Their probable effect on modulating oocyte maturation may be the cause of infertility in females.

Roles of individual human Dishevelled paralogs in the Wnt signalling pathways

Dishevelled (DVL) proteins are key mediators of most Wnt pathways. In all vertebrates, three DVL paralogs are present (DVL1, DVL2 and DVL3) but it is poorly defined to what extent they are functionally redundant. Here, we generated T-REx HEK 293 cells with only one DVL paralog (i.e., DVL1-only, DVL2-only, and DVL3-only) and compared their response to Wnt-3a and Wnt-5a ligands with wild type and DVL triple knockout cells. We show that DVL is essential, in addition to the previously shown Wnt-3a-induced phosphorylation of LRP6 and transcriptional activation of TCF/LEF-dependent reporter, also for Wnt-3a-induced degradation of AXIN1 and Wnt-5a-induced phosphorylation of ROR1. We have quantified the molar ratios of DVL1:DVL2:DVL3 in our model to be approximately 4:80:16. Interestingly, DVL-only cells do not compensate for the lack of other paralogs and are still fully functional in all analyzed readouts with the exception of Wnt-3a-induced transcription assessed by TopFlash assay. In this assay, the DVL1-only cell line was the most potent; on the contrary, the DVL3-only cell line exhibited only the negligible capacity to mediate Wnt signals. Using a novel model system - complementation assays in T-REx HEK 293 with amplified Wnt signal response (RNF43/ZNRF3/DVL1/DVL2/DVL3 penta KO cells) we demonstrate that it is not the total amount of DVL but ratio of individual paralogs what decides the signal strength. In sum, this study contributes to our better understanding of the role of individual human DVL paralogs in the Wnt pathway.

Clinicopathological Association of Autophagy Related 5 Protein with Prognosis of Colorectal Cancer

Gene mutation and pathogenesis bacteria are highly associated with colorectal cancer (CRC) development and progression. Autophagy is a self-clearance pathway to degrade abnormal proteins and infected bacteria in cells. Autophagy plays a dual role in cancer development. Among the autophagy-related (ATG) proteins, ATG5 is the key component required for the core machinery of autophagy. However, the role of ATG5 in CRC malignancy remains unclear. Herein, we found that a high ATG5 protein level was correlated with poor overall survival (OS) and disease-free survival (DFS) of 118 patients with CRC. After stratification with demographic and clinicopathologic factors, a high ATG5 protein level was significantly correlated with unfavorable overall survival in female and elder (>60 year) CRC patients and tumor tissues with poor differentiation, late T stages (III + IV), whereas the ATG5 protein level was positively associated with the overall survival in CRC patients without lymph node invasion and radiation therapy. In contrast, a high ATG5 protein level was significantly associated with worse DFS in CRC patients with early stage of AJCC and no radiation therapy. In addition, colorectal cancer cells stably harboring small interfering RNA (siRNA) against ATG5 diminished the tumorsphere formation and sensitized cancer cells to chemotherapeutic agents. Taken together, our results suggest that ATG5 might be a prognostic biomarker for CRC and a potential therapeutic target for CRC patients.

Nuclear Dishevelled targets gene regulatory regions and promotes tumor growth

Dishevelled (DVL) critically regulates Wnt signaling and contributes to a wide spectrum of diseases and is important in normal and pathophysiological settings. However, how it mediates diverse cellular functions remains poorly understood. Recent discoveries have revealed that constitutive Wnt pathway activation contributes to breast cancer malignancy, but the mechanisms by which this occurs are unknown and very few studies have examined the nuclear role of DVL. Here, we have performed DVL3 ChIP-seq analyses and identify novel target genes bound by DVL3. We show that DVL3 depletion alters KMT2D binding to novel targets and changes their epigenetic marks and mRNA levels. We further demonstrate that DVL3 inhibition leads to decreased tumor growth in two different breast cancer models in vivo. Our data uncover new DVL3 functions through its regulation of multiple genes involved in developmental biology, antigen presentation, metabolism, chromatin remodeling, and tumorigenesis. Overall, our study provides unique insight into the function of nuclear DVL, which helps to define its role in mediating aberrant Wnt signaling.

ESC-sEVs Rejuvenate Aging Hippocampal NSCs by Transferring SMADs to Regulate the MYT1-Egln3-Sirt1 Axis

Tissue stem cell senescence leads to stem cell exhaustion, which results in tissue homeostasis imbalance and a decline in regeneration capacity. However, whether neural stem cell (NSC) senescence occurs and causes neurogenesis reduction during aging is unknown. In this study, mice at different ages were used to detect age-related hippocampal NSC (H-NSC) senescence, as well as the function and mechanism of embryonic stem cell-derived small extracellular vesicles (ESC-sEVs) in rejuvenating H-NSC senescence. We found a progressive cognitive impairment, as well as age-related H-NSC senescence, in mice. ESC-sEV treatment significantly alleviated H-NSC senescence, recovered compromised self-renewal and neurogenesis capacities, and reversed cognitive impairment. Transcriptome analysis revealed that myelin transcription factor 1 (MYT1) is downregulated in senescent H-NSCs but upregulated by ESC-sEV treatment. In addition, knockdown of MYT1 in young H-NSCs accelerated age-related phenotypes and impaired proliferation and differentiation capacities. Mechanistically, ESC-sEVs rejuvenated senescent H-NSCs partly by transferring SMAD family members 4 (SMAD4) and 5 (SMAD5) to activate MYT1, which downregulated egl-9 family hypoxia inducible factor 3 (Egln3), followed by activation of hypoxia inducible factor 2 subunit α (HIF-2α), nicotinamide phosphoribosyl transferase (NAMPT), and sirtuin 1 (Sirt1) successively. Taken together, our results indicated that H-NSC senescence caused cellular exhaustion, neurogenesis reduction, and cognitive impairment during aging, which can be reversed by ESC-sEVs. Thus, ESC-sEVs may be promising therapeutic candidates for age-related diseases.

Sirtuin 1 and 2 inhibitors enhance the inhibitory effect of sorafenib in hepatocellular carcinoma cells

Multidrug resistance (MDR) counteracts the efficiency of sorafenib, an important first-line therapy for hepatocellular carcinoma (HCC). Sirtuins (SIRTs) 1 and 2 are associated with tumor progression and MDR. We treated 2D and 3D cultures (which mimic the features of in vivo tumors) from HCC cells with sorafenib alone or in the presence of SIRTs 1 and 2 inhibitors (cambinol or EX-527; combined treatments). Cultures subjected to combined treatments showed a greater fall in cellular viability, proliferation (PCNA, cyclin D1 and Ki-67 expression and cell cycle analysis), migration and invasion when compared with cultures treated only with sorafenib. Similarly, combined treatments produced more apoptosis (annexin V/PI, caspase-3/7 activity) than sorafenib alone. Since cell cycle dysregulation and apoptotic blockage are reported mechanisms of MDR, the modulation found in PCNA, cyclin D1, Ki-67 and caspase-3/7 proteins by cambinol and EX-527 are probably playing a role in enhancing the sensitivity of HCC cell lines to sorafenib. EX-527 reduced MRP3 and BCRP expression in sorafenib-treated HCC cells. Since ABC transporters contribute to MDR, MRP3 and BCRP could be also influencing in the response of HCC cells to sorafenib. Overall, 2D and 3D cultures behave similarly except that 3D cultures were less sensitive to treatments, reinforcing the clinical relevance of the current study. Findings presented in this manuscript support a potential application for SIRTs 1 and 2 inhibitors since we demonstrated that these compounds enhance the inhibitory effect of sorafenib upon treatment of hepatocellular carcinoma cells lines.

Wnt Pathway: An Integral Hub for Developmental and Oncogenic Signaling Networks

The Wnt pathway is an integral cell-to-cell signaling hub which regulates crucial development processes and maintenance of tissue homeostasis by coordinating cell proliferation, differentiation, cell polarity, cell movement, and stem cell renewal. When dysregulated, it is associated with various developmental diseases, fibrosis, and tumorigenesis. We now better appreciate the complexity and crosstalk of the Wnt pathway with other signaling cascades. Emerging roles of the Wnt signaling in the cancer stem cell niche and drug resistance have led to development of therapeutics specifically targeting various Wnt components, with some agents currently in clinical trials. This review highlights historical and recent findings on key mediators of Wnt signaling and how they impact antitumor immunity and maintenance of cancer stem cells. This review also examines current therapeutics being developed that modulate Wnt signaling in cancer and discusses potential shortcomings associated with available therapeutics.

Dishevelled family proteins in serous ovarian carcinomas: a clinicopathologic and molecular study

Dishevelled family proteins (DVL1, DVL2, and DVL3) are cytoplasmic mediators involved in canonical and non-canonical Wnt signaling that are important for embryonic development. Since Wnt signaling promotes cell proliferation and invasion, its increased activation is associated with cancer development as well. To get deeper insight into the behavior of Dishevelled proteins in cancer, we studied their expression in serous ovarian carcinomas [both low- (LGSC) and high-grade (HGSC)], and HGSC cell lines OVCAR5, OVCAR8, and OVSAHO. DVL protein expression in serous ovarian carcinomas tissues was analyzed using immunohistochemistry, while DVL protein and mRNA expressions in HGSC cell lines were analyzed using Western blot and quantitative real-time PCR. DVL1 protein expression was significantly higher in LGSC compared with normal ovarian tissue, while DVL3 was overexpressed in both LGSC and HGSC. DVL2 and DVL3 protein expression was higher in HGSC cell lines when compared with normal control cell line FNE1, while DVL1, DVL2, and DVL3 mRNA expression was significantly increased only in OVSAHO cell line. Survival analysis revealed no significant impact of DVL proteins on patients' outcome. Our data show an active involvement of Dishevelled family proteins in serous ovarian carcinomas. Further studies should confirm the clinical relevance of these observations.

Acetylation of conserved DVL-1 lysines regulates its nuclear translocation and binding to gene promoters in triple-negative breast cancer

Dishevelled (DVL) proteins are central mediators of the Wnt signalling pathway and are versatile regulators of several cellular processes, yet little is known about their post-translational regulation. Acetylation is a reversible post-translational modification (PTM) which regulates the function of several non-histone proteins involved in tumorigenesis. Since we previously demonstrated that lysine deacetylase, SIRT-1, regulates DVL protein levels and its function, we reasoned that DVL could potentially be a substrate for SIRT-1 mediated deacetylation. To further examine the potential role of multiple families of lysine deacetylases in the post-translational regulation of DVL, we screened for novel acetylation sites using liquid chromatography mass-spectrometry (LC-MS/MS) analysis. Herein, we report 12 DVL-1 lysine residues that show differential acetylation in response to changes in oxygen tension and deacetylase inhibition in triple-negative breast cancer (TNBC). PTMs are well documented to influence protein activity, and cellular localization. We also identify that acetylation of two key lysine residues, K69 and K285, present on the DIX and PDZ domains respectively, promote nuclear over cytoplasmic localization of DVL-1, and influences its promoter binding and regulation of genes implicated in cancer. Collectively, these findings for the first time, uncover acetylation as a novel layer of regulation of DVL-1 proteins.

Functional roles of circular RNAs during epithelial-to-mesenchymal transition

Cancer has become a major health issue worldwide, contributing to a high mortality rate. Tumor metastasis is attributed to the death of most patients. Epithelial-to-mesenchymal transition (EMT) plays a vital role in inducing metastasis. During EMT, epithelial cells lose their characteristics, such as cell-to-cell adhesion and cell polarity, and cells gain motility, migratory potential, and invasive properties to become mesenchymal stem cells. Circular RNAs (circRNAs) are closely associated with tumor metastasis and patient prognosis, as revealed by increasing lines of evidence. CircRNA is a type of single-stranded RNA that forms a covalently closed continuous loop. CircRNAs are insensitive to ribonucleases and are widespread in body fluids. This work is the first review on EMT-related circRNAs. In this review, we briefly discuss the characteristics and functions of circRNAs. The correlation of circRNAs with EMT has been reported, and we discuss the ways circRNAs can regulate EMT progression through EMT transcription factors, EMT-related signaling pathways, and other mechanisms. This work summarizes current studies on EMT-related circRNAs in various cancers and provides a theoretical basis for the use of EMT-related circRNAs in targeted management and therapy.

SNX3 suppresses the migration and invasion of colorectal cancer cells by reversing epithelial-to-mesenchymal transition via the β-catenin pathway

The Wnt/β-catenin signaling pathway is a well-studied pathway that drives the carcinogenesis and metastasis of colorectal cancer (CRC). The secretion of Wnt proteins is essential for the continuous activation of Wnt/β-catenin signaling in CRC. The secretion of Drosophila wingless, which is homologous to the human Wnt protein, is mediated by sorting nexin 3 (SNX3) in Drosophila; however, the role of SNX3 in CRC remains unknown. In the present study it was demonstrated that SNX3 reduced the migratory and invasive ability of HCT116 human CRC cells, and reversed epithelial-mesenchymal transition (EMT). Conversely, in the HT29 CRC cell line, which endogenously expresses high levels of SNX3, short hairpin RNA or siRNA-mediated knockdown of SNX3 induced EMT, and enhanced cell migration and invasion. In addition, upregulation of SNX3 significantly inhibited metastasis of HCT116 cells to the lungs of mice. These SNX3-mediated effects were associated with downregulation of β-catenin. Taken together, by downregulating β-catenin, SNX3 may mediate EMT and reverse CRC metastasis.

The effect of adipocyte-macrophage crosstalk in obesity-related breast cancer

Adipose tissue is the primary source of many pro-inflammatory cytokines in obesity. Macrophage numbers and pro-inflammatory gene expression are positively associated with adipocyte size. Free fatty acid and tumor necrosis factor-α involve in a vicious cycle between adipocytes and macrophages aggravating inflammatory changes. Thereby, M1 macrophages form a characteristic 'crown-like structure (CLS)' around necrotic adipocytes in obese adipose tissue. In obese women, CLSs of breast adipose tissue are responsible for both increase in local aromatase activity and aggressive behavior of breast cancer cells. Interlinked molecular mechanisms between adipocyte-macrophage-breast cancer cells in obesity involve seven consecutive processes: Excessive release of adipocyte- and macrophage-derived inflammatory cytokines, TSC1-TSC2 complex-mTOR crosstalk, insulin resistance, endoplasmic reticulum (ER) stress and excessive oxidative stress generation, uncoupled respiration and hypoxia, SIRT1 controversy, the increased levels of aromatase activity and estrogen production. Considering elevated risks of estrogen receptor (E2R)-positive postmenopausal breast cancer growth in obesity, adipocyte-macrophage crosstalk is important in the aforementioned issues. Increased mTORC1 signaling in obesity ensures the strong activation of oncogenic signaling in E2Rα-positive breast cancer cells. Since insulin and insulin-like growth factors have been identified as tumor promoters, hyperinsulinemia is an independent risk factor for poor prognosis in breast cancer despite peripheral insulin resistance. The unpredictable effects of adipocyte-derived leptin-estrogen-macrophage axis, and sirtuin 1 (SIRT1)-adipose-resident macrophage axis in obese postmenopausal patients with breast cancer are unresolved mechanistic gaps in the molecular links between the tumor growth and adipocytokines.

Effects of SIRT1 silencing on viability, invasion and metastasis of human glioma cell lines

Silent information regulator 1 (SIRT1), a member of the sirtuin family, is involved in the development of various types of tumor. Previous studies have revealed that SIRT1 has dual functions, as a promoter and an inhibitor, in certain tumors. However, the role of SIRT1 in invasion and metastasis of glioma cells and its associated signaling pathway remain unclear. The aim of the present study was to determine the effects of SIRT1 on these processes and on the epithelial-mesenchymal transition (EMT) in human glioma and adjacent tissues, and in the human glioma cell lines U87 and U251. SIRT1 expression in tissues was investigated using the reverse transcription-quantitative polymerase chain reaction, western blotting and immunohistochemistry. The U87 and U251 cell lines were divided into control and SIRT1-small interfering RNA (siRNA) groups. The Cell Counting Kit-8, cell invasion assays were used to evaluate the effects of SIRT1 silencing on cell viability, invasion and EMT. Results indicated that SIRT1 was highly expressed in glioma tissues compared with in adjacent brain tissues. In addition, SIRT1-siRNA significantly inhibited the viability and invasion of U87 and U251 cells. Furthermore, EMT analysis revealed that the expression levels of the mesenchymal markers fibronectin and vimentin were significantly lower in the SIRT1-siRNA group compared with in the control group. Conversely, expression levels of the epithelial markers epithelial cadherin and β-catenin were significantly higher in the SIRT1-siRNA group compared with in the control group. In conclusion, the results of the present study indicated that SIRT1 was positively associated with viability and invasion of U87 cells, potentially through EMT. These results suggested that SIRT1 may serve a crucial role in the proliferation and development of glioma.

The Interplay of SIRT1 and Wnt Signaling in Vascular Calcification

Vascular calcification is a major health risk and is highly correlated with atherosclerosis, diabetes, and chronic kidney disease. The development of vascular calcification is an active and complex process linked with a multitude of signaling pathways, which regulate promoters and inhibitors of osteogenesis, the balance of which become deregulated in disease conditions. SIRT1, a protein deacetylase, known to be protective in inhibiting oxidative stress and inflammation within the vessel wall, has been shown as a possible key player in modulating the cell-fate determining canonical Wnt signaling pathways. Suppression of SIRT1 has been reported in patients suffering with cardiovascular pathologies, suggesting that the sustained acetylation of osteogenic factors could contribute to their activation and in turn, lead to the progression of calcification. There is clear evidence of the synergy between β-Catenin and elevated Runx2, and with Wnt signaling being β-Catenin dependent, further understanding is needed as to how these molecular pathways converge and interact, in order to provide novel insight into the mechanism by which smooth muscle cells switch to an osteogenic differentiation programme. Therefore, this review will describe the current concepts of pathological soft tissue mineralization, with a focus on the contribution of SIRT1 as a regulator of Wnt signaling and its targets, discussing SIRT1 as a potential target for manipulation and therapy.

DVL1 and DVL3 differentially localize to CYP19A1 promoters and regulate aromatase mRNA in breast cancer cells

The CYP19A1 gene encodes aromatase, an enzyme that converts androgens into estrogens and consequently directly contributes to both the depletion of androgens and the synthesis of estrogens in several organs. Aromatase is critical for diverse biological processes such as proliferation, regulation of fat metabolism and hormone signaling. Additionally, it is also overexpressed in diverse cancers and drives hormone-dependent tumor progression and increases 17-β-estradiol (E₂) within tumors and the tumor microenvironment. Although the inhibition of E₂ production via aromatase inhibitors represents a major therapeutic paradigm in clinical oncology, fundamental questions regarding how cancer cells gain the capacity to overexpress aromatase remain unanswered. Multiple tissue-specific CYP19A1 promoters are known to be aberrantly active in tumors, yet how this occurs is unclear. Here, for the first time, we report that Dishevelled (DVL) proteins, which are key mediators of Wnt signaling, regulate aromatase expression in multiple breast cancer cell lines. We also report that DVL enters the nucleus and localizes to at least two different CYP19A1 promoters (pII and I.4) previously reported to drive overexpression in breast tumors and to a very distal CYP19A1 placental promoter (I.1) that remains poorly characterized. We go on to demonstrate that DVL-1 and DVL-3 loss of function leads to differential changes in various aromatase transcripts and in E₂ production. The report, herein, uncovers a new regulator of CYP19A1 transcription and for the first time demonstrates that DVL, a critical mediator of WNT signaling, contributes to aberrant breast cancer-associated estrogen production.

Neurotherapeutic capacity of P7C3 agents for the treatment of Traumatic Brain Injury

Traumatic brain injury (TBI) is a significant public health problem around the world. A promising area of research is the characterization of small, drug-like molecules that have potent clinical properties. One pharmacotherapeutic agent in particular, an aminopropyl carbazole called P7C3, was discovered using an in vivo screen to identify new agents that augmented the net magnitude of adult hippocampal neurogenesis. P7C3 greatly enhanced neurogenesis by virtue of increasing survival rates of immature neurons. The potent neuroprotective efficacy of P7C3 is likely due to enhanced nicotinamide phosphoribosyltransferase (NAMPT) activity, which supports critical cellular processes. The scaffold of P7C3 was found to have favorable pharmacokinetic properties, good bioavailability, and was nontoxic. Preclinical studies have shown that administration of the P7C3-series of neuroprotective compounds after TBI can rescue and reverse detrimental cellular events leading to improved functional recovery. In several TBI models and across multiple species, P7C3 and its analogues have produced significant neuroprotection, axonal preservation, robust increases in the net magnitude of adult neurogenesis, protection from injury-induced LTP deficits, and improvement in neurological functioning. This review will elucidate the exciting and diverse therapeutic findings of P7C3 administration in the presence of a complex and multifactorial set of cellular and molecular challenges brought forth by experimental TBI. The clinical potential and broad therapeutic applicability of P7C3 warrants much needed investigation into whether these remedial effects can be replicated in the clinic. P7C3 may serve as an important step forward in the design, understanding, and implementation of pharmacotherapies for treating patients with TBI. This article is part of the Special Issue entitled "Novel Treatments for Traumatic Brain Injury".

Gold nanoparticles-induced cytotoxicity in triple negative breast cancer involves different epigenetic alterations depending upon the surface charge

Gold nanoparticles (AuNPs) are used enormously in different cancers but very little is known regarding their molecular mechanism and surface charge role in the process of cell death. Here, we elucidate the molecular mechanism by which differentially charged AuNPs induce cytotoxicity in triple negative breast cancer (TNBC) cells. Cytotoxicity assay revealed that both negatively charged (citrate-capped) and positively charged (cysteamine-capped) AuNPs induced cell-death in a dose-dependent manner. We provide first evidence that AuNPs-induced oxidative stress alters Wnt signalling pathway in MDA-MB-231 and MDA-MB-468 cells. Although both differentially charged AuNPs induced cell death, the rate and mechanism involved in the process of cell death were different. Negatively charged AuNPs increased the expression of MKP-1, dephosphorylated and deacetylated histone H3 at Ser10 and K9/K14 residues respectively whereas, positively charged AuNPs decreased the expression of MKP-1, phosphorylated and acetylated histone H3 at Ser 10 and K9/K14 residues respectively. High-resolution transmission electron microscopy (HRTEM) studies revealed that AuNPs were localised in cytoplasm and mitochondria of MDA-MB-231 cells. Interestingly, AuNPs treatment makes MDA-MB-231 cells sensitive to 5-fluorouracil (5-FU) by decreasing the expression of thymidylate synthetase enzyme. This study highlights the role of surface charge (independent of size) in the mechanisms of toxicity and cell death.

SIRT-1 regulates TGF-β-induced dermal fibroblast migration via modulation of Cyr61 expression

SIRT1 is a NAD-dependent protein deacetylase that participates in cellular regulation. The increased migration of fibroblasts is an important phenotype in fibroblast activation. The role of SIRT1 in cell migration remains controversial as to whether SIRT1 acts as an activator or suppressor of cell migration. Therefore, we have established the role of SIRT1 in the migration of human dermal fibroblasts and explored targets of SIRT1 during dermal fibroblast migration. SIRT1 and Cyr61 were expressed in human dermal fibroblasts and the stimulation with TGF-β further induced their expression. Treatment with resveratrol (RSV), a SIRT1 agonist, or overexpression of SIRT1 also promoted the expression Cyr61 in human dermal fibroblasts, whereas the inhibition of SIRT1 activity by nicotinamide or knockdown of SIRT1 decreased the level of Cyr61, as well as TGF-β or RSV-induced Cyr61 expression. Blocking of ERK signaling by PD98509 reduced the expression of Cyr61 induced by TGF-β or RSV. TGF-β, RSV, or SIRT1 overexpression enhanced β-catenin as well as Cyr61 expression. This stimulation was reduced by the Wnt inhibitor XAV939. RSV increased migration and nicotinamide attenuated RSV-induced migration of human dermal fibroblasts. Furthermore, SIRT1 overexpression promoted cell migration, whereas blocking Cyr61 attenuated SIRT1-stimulated migration of human dermal fibroblasts. SIRT1 increased cell migration by stimulating Cyr61 expression and the ERK and Wnt/β-catenin signaling. SIRT1-induced Cyr61 activity is very important for human dermal fibroblasts migration.

Dishevelled: A masterful conductor of complex Wnt signals

The Dishevelled gene was first identified in Drosophila mutants with disoriented hair and bristle polarity [1-3]. The Dsh gene (Dsh/Dvl, in Drosophila and vertebrates respectively) gained popularity when it was discovered that it plays a key role in segment polarity during early embryonic development in Drosophila [4]. Subsequently, the vertebrate homolog of Dishevelled genes were identified in Xenopus (Xdsh), mice (Dvl1, Dvl2, Dvl3), and in humans (DVL1, DVL2, DVL3) [5-10]. Dishevelled functions as a principal component of Wnt signaling pathway and governs several cellular processes including cell proliferation, survival, migration, differentiation, polarity and stem cell renewal. This review will revisit seminal discoveries and also summarize recent advances in characterizing the role of Dishevelled in both normal and pathophysiological settings.

SIRT1 suppresses adipogenesis by activating Wnt/β-catenin signaling in vivo and in vitro

Sirtuin 1 (SIRT1) regulates adipocyte and osteoblast differentiation. However, the underlying mechanism should be investigated. This study revealed that SIRT1 acts as a crucial repressor of adipogenesis. RNA-interference-mediated SIRT1 knockdown or genetic ablation enhances adipogenic potential, whereas SIRT1 overexpression inhibits adipogenesis in mesenchymal stem cells (MSCs). SIRT1 also deacetylates the histones of sFRP1, sFRP2, and Dact1 promoters; inhibits the mRNA expression of sFRP1, sFRP2, and Dact1; activates Wnt signaling pathways; and suppresses adipogenesis. SIRT1 deacetylates β-catenin to promote its accumulation in the nucleus and thus induces the transcription of genes that block MSC adipogenesis. In mice, the partial absence of SIRT1 promotes the formation of white adipose tissues without affecting the development of the body of mice. Our study described the regulatory role of SIRT1 in Wnt signaling and proposed a regulatory mechanism of adipogenesis.

Leptin induces SIRT1 expression through activation of NF-E2-related factor 2: Implications for obesity-associated colon carcinogenesis

Leptin, a representative adipokine secreted from the white adipose tissue, is considered as a potential linker between obesity and cancer. SIRT1 is an NAD⁺-dependent histone/protein deacetylase speculated to function as an oncogene. In the present study, we found that leptin signaling-defective ob/ob and db/db mice had lower colonic expression of SIRT1 compared with leptin signaling-intact C57BL/6J mice, implying that leptin signaling is crucial for SIRT1 expression in vivo. Moreover, leptin induced up-regulation of SIRT1 in human colon cancer (HCT-116) cells. Leptin stimulated migration and invasion of cultured HCT-116 cells and tumor growth in the xenograft assay, and these effects were abrogated by a SIRT1 inhibitor sirtinol, suggesting that SIRT1 plays a role in leptin-induced colon carcinogenesis. Leptin-induced SIRT1 expression was regulated by the redox-sensitive transcription factor NF-E2-related factor 2 (Nrf2). Leptin stimulated nuclear accumulation of Nrf2 as well as its binding to the antioxidant response elements located in the SIRT1 promoter. Moreover, siRNA knockdown of Nrf2 abrogated the leptin-induced SIRT1 expression. Notably, SIRT1 was significantly reduced in colon tissues of Nrf2-null mice, lending further support to Nrf2-dependent SIRT1 expression. Expression of leptin, Nrf2 and SIRT1 was coordinately increased in human colon tumor tissues. In conclusion, leptin might play a role in colon carcinogenesis by inducing Nrf2-dependent SIRT1 overexpression.

Narrower insight to SIRT1 role in cancer: A potential therapeutic target to control epithelial-mesenchymal transition in cancer cells

The epithelial-mesenchymal transition (EMT) is a highly networked cellular process which involves cell transition from the immotile epithelial to the motile mesenchymal phenotype, whereby cells lose their cell-cell adhesion and cell polarity. This important process is one of the underlying mechanisms for enabling invasion and metastasis of cancer cells which is considered as malignant phase of tumor progression. However, the molecular mechanisms of this process are not fully clarified. It is reported that Sirtuin1 (SIRT1), a NAD+ dependent class III histone deacetylase is associated with tumor metastasis through positive regulation of EMT in several types of cancers. Recent studies confirmed that up and down regulation of SIRT1 expression remarkably change the migration ability of different cancer cells in vitro and tumor metastasis in vivo. Also, according to this fact that carcinomas as the main human solid tumors, originate from different epithelial cell types, SIRT1 role in EMT has received a great attention due to its potential role in tumor development and metastasis. Therefore, SIRT1 has been proposed as a key regulator of cancer metastasis by promoting EMT, although little is known about the cleared effect of SIRT1 in this transition. Our aim in this review is to explain in more detail the role of SIRT1 in various signaling pathways related to carcinogenesis, with the focus on the promoting role of SIRT1 in EMT as a potential therapeutic target to control EMT and to prevent cancer progression.

Sirtuins at the crossroads of stemness, aging, and cancer

Sirtuins are stress‐responsive proteins that direct various post‐translational modifications (PTMs) and as a result, are considered to be master regulators of several cellular processes. They are known to both extend lifespan and regulate spontaneous tumor development. As both aging and cancer are associated with altered stem cell function, the possibility that the involvement of sirtuins in these events is mediated by their roles in stem cells is worthy of investigation. Research to date suggests that the individual sirtuin family members can differentially regulate embryonic, hematopoietic as well as other adult stem cells in a tissue‐ and cell type‐specific context. Sirtuin‐driven regulation of both cell differentiation and signaling pathways previously involved in stem cell maintenance has been described where downstream effectors involved determine the biological outcome. Similarly, diverse roles have been reported in cancer stem cells (CSCs), depending on the tissue of origin. This review highlights the current knowledge which places sirtuins at the intersection of stem cells, aging, and cancer. By outlining the plethora of stem cell‐related roles for individual sirtuins in various contexts, our purpose was to provide an indication of their significance in relation to cancer and aging, as well as to generate a clearer picture of their therapeutic potential. Finally, we propose future directions which will contribute to the better understanding of sirtuins, thereby further unraveling the full repertoire of sirtuin functions in both normal stem cells and CSCs.

Resveratrol controlled the fate of porcine pancreatic stem cells through the Wnt/β-catenin signaling pathway mediated by Sirt1

Porcine pancreatic stem cells (PSCs) are considered promising transplant materials that may be used to treat diabetes, but some problems, such as insufficient cell number and low differentiation efficiency, should be solved before its clinical application. Resveratrol is a natural polyphenolic compound that can alleviate the complications of diabetes. In this study, we aimed to explore the specific effect of resveratrol on porcine PSCs. We treated porcine PSCs with 10 μM, 25 μM resveratrol to explore the effect of resveratrol on porcine PSCs. We found that 10 μM resveratrol improved the proliferation of porcine PSCs, increased the expression of A-β-catenin (active β-catenin), Pcna, C-Myc, Bcl-2 and sirtuin-1 (Sirt1), and decreased the expression of P53, Caspase3. While 25 μM resveratrol had almost opposite effect compared with 10 μM resveratrol group. The utilization of Dickkopf-related protein 1 (DKK1, Wnt signaling pathway inhibitor) and nicotinamide (Sirt1 inhibitor) suggested that resveratrol regulated cell proliferation by controlling Wnt signaling pathway and this effect was mediated by Sirt1. Our results further revealed that 10 μM resveratrol promoted the formation of β-like cells regulated by Wnt/β-catenin signal pathway. Relatively low-dose resveratrol could improve porcine PSCs fate. It lays theoretical foundation for diabetes treatment with cell transplantation in future.

Long non-coding RNA TUG1 promotes cervical cancer progression by regulating the miR-138-5p-SIRT1 axis

Increasing evidences showed that long non-coding RNAs (lncRNAs) play vital roles in tumor progression. Recent studies indicated that lncRNA TUG1 was upregulated and promoted tumor processes in several cancers. However, the expression and underlying mechanism of TUG1 in cervical cancer remain unclear. In the present study, we found that TUG1 expression was upregulated in cervical cancer tissues and correlated with advanced clinical features and poor overall survival. TUG1 knockdown suppressed cervical cancer cell growth and metastasis in vitro and tumor growth in vivo. In addition, our results indicated that TUG1 could act as an endogenous sponge by directly binding to miR-138-5p and suppressed miR-138-5p expression. Furthermore, we found that TUG1 could reverse the inhibitory effect of miR-138-5p on cervical cancer cells processes, which might be involved in the activation of SIRT1, a target gene of miR-138-5p, and activation of Wnt/β-catenin signaling pathway. Taken together, we elucidated that TUG1 might promote cervical cancer malignant progression via miR-138-5p-SIRT1-Wnt/β-catenin signaling pathway axis.

AMPK activators suppress breast cancer cell growth by inhibiting DVL3-facilitated Wnt/β-catenin signaling pathway activity

Adenosine monophosphate-activated protein kinase (AMPK) is a principal regulator of metabolism and the conservation of energy in cells, and protects them from exposure to various stressors. AMPK activators may exhibit therapeutic potential as suppressors of cell growth; however, the molecular mechanism underlying this phenomenon in various cancer cells remains to be fully elucidated. The present study investigated the effects of AMPK activators on breast cancer cell growth and specified the underlying molecular mechanism. In the present study, the AMPK activator metformin impaired breast cancer cell growth by reducing dishevelled segment polarity protein 3 (DVL3) and β‑catenin levels. Western blotting and immunohistochemistry demonstrated that DVL3 was recurrently upregulated in breast cancer cells that were not treated with metformin, and was significantly associated with enhanced levels of β‑catenin, c‑Myc and cyclin D1. Overexpression of DVL3 resulted in upregulation of β‑catenin and amplification of breast cancer cell growth, which confirmed that Wnt/β‑catenin activation via DVL3 is associated with breast cancer oncogenesis. To elucidate the underlying mechanism of these effects, the present study verified that metformin resulted in a downregulation of DVL3 and β‑catenin in a dose‑dependent manner, and induced phosphorylation of AMPK. Compound C is an AMPK inhibitor, which when administered alongside metformin, significantly abolished the effects of metformin on the reduction of DVL3 and activation of the phosphorylation of AMPK. Notably, the effects of metformin on the mRNA expression levels of DVL3 remain to be fully elucidated; however, a possible interaction with DVL3 at the post‑transcriptional level was observed. It has previously been suggested that the molecular mechanism underlying AMPK activator‑induced suppression of breast cancer cell growth involves an interaction with, and impairment of, DVL3 proteins. The results of the present study are of future clinical importance and advocate the use of metformin as a potential therapeutic agent against breast cancer.

Molecular and Cellular Changes During Cancer Progression Resulting From Genetic and Epigenetic Alterations

Tumorigenesis is a complex process that involves a persistent dismantling of cellular safeguards and checkpoints. These molecular and cellular changes that accumulate over months or decades lead to a change in the fundamental identity of a cell as it transitions from normal to malignant. In this chapter, we will examine some of the molecular changes in the evolving relationship between the genome and epigenome and highlight some of the key changes that occur as normal cells progress to tumor cells. For many years tumorigenesis was almost exclusively attributed to mutations in protein-coding genes. This notion that mutations in protein-coding genes were a fundamental driver of tumorigenesis enabled the development of several novel therapeutics that targeted the mutant protein or overactive pathway responsible for driving a significant portion of the tumor growth. However, because many therapeutic challenges remained in the face of these advances, it was clear that other pieces to the puzzle had yet to be discovered. Advances in molecular and genomics techniques continued and the study of epigenetics began to expand and helped reshape the view that drivers of tumorigenesis extended beyond mutations in protein-coding genes. Studies in the field of epigenetics began to identify aberrant epigenetic marks which created altered chromatin structures and enabled protein expression in tissues that defied rules governing tissue-specificity. Not only were epigenetic alterations found to enable overexpression of proto-oncogenes, they also led to the silencing of tumor suppressor genes. With these discoveries, it became clear that tumor growth could be stimulated by much more than mutations in protein-coding genes. In fact, it became increasingly clear that much of the human genome, while transcribed, did not lead to proteins. This discovery further led to studies that began to uncover the role of noncoding RNAs in regulating chromatin structure, gene transcription, and tumor biology. In this chapter, some of the key alterations in the genome and epigenome will be explored, and some of the cancer therapies that were developed as a result of these discoveries will be discussed.

Brachyury promotes tamoxifen resistance in breast cancer by targeting SIRT1

Tamoxifen is effective for treating estrogen receptor-alpha (ERα)-positive breast cancers. However, few molecular mediators of tamoxifen resistance have been elucidated. In the present study, we determine the underlying roles of Brachyury in tamoxifen resistance. Loss- and gain-of-function assay are utilized to confirm the oncogenic roles of Brachyury in breast cancer. Compared with the normal MCF10A cells, Brachyury is commonly overexpressed in breast cancer cell lines. Knockdown of Brachyury inhibits tamoxifen resistance, whereas overexpression of Brachyury enhances tamoxifen resistance as demonstrated increased cell viability and reduced cell apoptosis. Mechanistically, we demonstrate for the first time that Brachyury mediates tamoxifen resistance by regulating Sirtuin-1 (SIRT1). Collectively, our data, as a proof of principle, indicate that Brachyury is a candidate marker for predicting the clinical efficacy of tamoxifen and targeting SIRT1 could overcome resistance to tamoxifen in breast cancer cells.

Effects of BMAL1-SIRT1-positive cycle on estrogen synthesis in human ovarian granulosa cells: an implicative role of BMAL1 in PCOS

Brain and muscle ARNT-like protein 1 (BMAL1) is necessary for fertility and has been found to be essential to follicle growth and steroidogenesis. Sirtuin1 (SIRT1) has been reported to interact with BMAL1 and function in a circadian manner. Evidence has shown that SIRT1 regulates aromatase expression in estrogen-producing cells. We aimed to ascertain if there is a relationship between polycystic ovary syndrome (PCOS) and BMAL1, and whether and how BMAL1 takes part in estrogen synthesis in human granulosa cells (hGCs). Twenty-four women diagnosed with PCOS and 24 healthy individuals undergoing assisted reproduction were studied. BMAL1 expression in their granulosa cells (GCs) was observed by quantitative real-time polymerase chain reaction (qRT-PCR). The level of expression in the PCOS group was lower than that of the group without PCOS (p < 0.05). We also analyzed estrogen synthesis and aromatase expression in KGN cell lines. Both were downregulated after BMAL1 and SIRT1 knock-down and, conversely, upregulated after overexpression treatments of these two genes in KGN cells. Both BMAL1 and SIRT1 had a mutually positive regulation, as did the phosphorylation of JNK. Furthermore, JNK overexpression increased estrogen synthesis activity and the expression levels of aromatase, BMAL1, and SIRT1. In KGN and hGCs, estrogen synthesis and aromatase expression were downregulated after treatment with JNK and SIRT1 inhibitors. In addition, BMAL1, SIRT1, and JNK expression levels were all downregulated. Our results demonstrate the effects of BMAL1 on estrogen synthesis in hGCs and suggest a BMAL1-SIRT1-JNK positive feedback cycle in this process, which points out an important role of BMAL1 in the development of PCOS.

Understanding Genetic Heterogeneity in Type 2 Diabetes by Delineating Physiological Phenotypes: SIRT1 and its Gene Network in Impaired Insulin Secretion

Type 2 diabetes (T2D) is a chronic metabolic disease which shows an exponential increase in all parts of the world. However, the disease is controllable by early detection and modified lifestyle. A series of factors have been associated with the pathogenesis of diabetes, and genes are considered to play a critical role. The individual risk of developing T2D is determined by an altered genetic background of the en-zymes involved in several metabolism-related biological mechanisms, including glucose homeostasis, insulin metab-olism, the glucose and ion transporters involved in glucose uptake, transcription factors, signaling intermediates of insulin signaling pathways, insulin production and secretion, pancreatic tissue development, and apoptosis. However, many candidate genes have shown heterogeneity of associations with the disease in different populations. A possible approach to resolving this complexity and under-standing genetic heterogeneity is to delineate the physiological phenotypes one by one as studying them in combination may cause discrepancies in association studies. A systems biology approach involving regulatory proteins, transcription factors, and microRNAs is one way to understand and identify key factors in complex diseases such as T2D. Our earlier studies have screened more than 100 single nucleotide polymorphisms (SNPs) belonging to more than 60 globally known T2D candidate genes in the Indian population. We observed that genes invariably involved in the activity of pancreatic β-cells provide susceptibility to type 2 diabetes (T2D). Encouraged by these results, we attempted to delineate in this review one of the commonest physiological phenotypes in T2D, namely impaired insulin secretion, as the cause of hyperglycemia. This review is also intended to explain the genetic basis of the pathophysiology of insulin secretion in the context of variations in the SIRT1 gene, a major switch that modulates insulin secretion, and a set of other genes such as HHEX, PGC-α, TCF7L2, UCP2, and ND3 which were found to be in association with T2D. The review aims to look at the genotypic and transcriptional regulatory relationships with the disease phenotype.

SIRT1 promotes epithelial-mesenchymal transition and metastasis in colorectal cancer by regulating Fra-1 expression

Understanding molecular mechanisms of colorectal cancer (CRC) metastasis is urgently required for targeted therapy and prognosis of metastatic CRC. In this study, we explored potential effects of silent mating type information regulation 2 homolog 1 (SIRT1) on CRC metastasis. Our data showed that ectopic expression of SIRT1 markedly increased the migration and invasion of CRC cells. In contrast, silencing SIRT1 repressed this behavior in aggressive CRC cells. Tumor xenograft experiments revealed that knockdown of SIRT1 impaired CRC metastasis in vivo. Silencing SIRT1 in CRC cells induced mesenchymal-epithelial transition (MET), which is the reverse process of epithelial-mesenchymal transition (EMT) and characterized by a gain of epithelial and loss of mesenchymal markers. We provided a mechanistic insight toward regulation of Fra-1 by SIRT1 and demonstrated a direct link between the SIRT1-Fra-1 axis and EMT. Moreover, SIRT1 expression correlated positively with Fra-1 expression, metastasis and overall survival in patients with CRC. Taken together, our data provide a novel mechanistic role of SIRT1 in CRC metastasis, suggesting that SIRT1 may serve as a potential therapeutic target for metastatic CRC.