Overexpression of SIRT1 promotes metastasis through epithelial-mesenchymal transition in hepatocellular carcinoma

Expression of LC3A, LC3B and p62/SQSTM1 autophagy proteins in hepatocellular carcinoma (HCC) tissues and the predicted microRNAs involved in the autophagy-related pathway

BACKGROUND

Autophagy plays multifaceted roles in regulating hepatocellular carcinoma (HCC) and the mechanisms involved are under-explored. Regulatory microRNAs (miRNAs) have been reported to target autophagy proteins but their roles in HCC is not well studied. Using HCC patient tissues, this study aims to investigate the association of autophagy with several clinicopathological parameters as well as identifying the autophagy-related miRNAs and the possible pathways.

METHODS AND RESULTS

Autophagy level in the HCC patient-derived cancer and non-cancer tissues was determined by immunohistochemistry (IHC) targeting SQSTM1, LC3A and LC3B proteins. Significance tests of clinicopathological variables were tested using the Fisher's exact or Chi-square tests. Gene and miRNA expression assays were carried out and analyzed using Nanostring platform and software followed by validation of other online bioinformatics tools, namely String and miRabel. Autophagy expression was significantly higher in cancerous tissues compared to adjacent non-cancer tissues. High LC3B expression was associated with advanced tumor histology grade and tumor location. Nanostring gene expression analysis revealed that SQSTM1, PARP1 and ATG9A genes were upregulated in HCC tissues compared to non-cancer tissues while SIRT1 gene was downregulated. These genes are closely related to an autophagy pathway in HCC. Further, using miRabel tool, three downregulated miRNAs (hsa-miR-16b-5p, hsa-miR-34a-5p, and hsa-miR-660-5p) and one upregulated miRNA (hsa-miR-539-5p) were found to closely interact with the abovementioned autophagy-related genes. We then mapped out the possible pathway involving the genes and miRNAs in HCC tissues.

CONCLUSIONS

We conclude that autophagy events are more active in HCC tissues compared to the adjacent non-cancer tissues. We also reported the possible role of several miRNAs in regulating autophagy-related genes in the autophagy pathway in HCC. This may contribute to the development of potential therapeutic targets for improving HCC therapy. Future investigations are warranted to validate the target genes reported in this study using a larger sample size and more targeted molecular technique.

Role of sirtuin 1 (SIRT1) in regulation of autophagy and nuclear factor-kappa Beta (NF-ĸβ) pathways in sorafenib-resistant hepatocellular carcinoma (HCC)

Hepatocellular carcinoma (HCC) remains a major global health problem with high incidence and mortality. Diagnosis of HCC at late stages and tumour heterogeneity in patients with different genetic profiles are known factors that complicate the disease treatment. HCC therapy becomes even more challenging in patients with drug resistance such as resistance to sorafenib, which is a common drug used in HCC patients. Sorafenib resistance can further aggravate HCC by regulating various oncogenic pathways such as autophagy and nuclear factor-kappa Beta (NF-ĸβ) signalling. Sirtuin 1 (SIRT1), is a nicotinamide adenosine dinucleotide (NAD)-dependent histone deacetylases that regulates various metabolic and oncogenic events such as cell survival, apoptosis, autophagy, tumourigenesis, metastasis and drug resistance in various cancers, but its role in HCC, particularly in sorafenib resistance is underexplored. In this study, we generated sorafenib-resistant HepG2 and Huh-7 liver cancer cell models to investigate the role of SIRT1 and its effect on autophagy and nuclear factor-kappa Beta (NF-ĸβ) signalling pathways. Western blot analysis showed increased SIRT1, altered autophagy pathway and activated NF-ĸβ signalling in sorafenib-resistant cells. SIRT1-silenced HCC cells demonstrated down-regulated autophagy in both parental and chemoresistant cells. This may occur through the deacetylation of key autophagy molecules such as FOXO3, beclin 1, ATGs and LC3 by SIRT1, highlighting the role of SIRT1 in autophagy induction. Silencing of SIRT1 also resulted in activated NF-ĸβ signalling. This is because SIRT1 failed to deacetylate p65 subunit of NF-κB, translocate the NF-κB from nucleus to cytoplasm, and suppress NF-κB activity due to the silencing. Hence, the NF-κB transcriptional activity was restored. These findings summarize the role of SIRT1 in autophagy/NF-ĸβ regulatory axis, with a similar trend observed in both parental and sorafenib-resistant cells. The present work promotes a better understanding of the role of SIRT1 in autophagy and NF-ĸβ signalling in HCC and sorafenib-resistant HCC. As some key proteins in these pathways are potential therapeutic targets, a better understanding of SIRT1/autophagy/NF-ĸβ axis could further improve the therapeutic strategies against HCC.

Emerging therapeutic strategy for mitigating cancer progression through inhibition of sirtuin-1 and epithelial-mesenchymal transition

With 8.8 million deaths worldwide, cancer is the major reason for the high rate of fatalities. Malignancy's commencement, progression, development, metastasis, and therapy resistance have all been correlated with the epithelial-to-mesenchymal transition (EMT) pathway. EMT promotes the cancer cells' metastatic spread and starts the development of treatment resistance. Sirtuin-1 (SIRT1) is a histone deacetylase that is important for signaling, cell persistence, and apoptosis. It does this by deacetylating important cell signaling molecules and proteins that are associated with apoptosis. The function of SIRT1 in EMT and cancer progression, as well as the emerging therapeutic strategy of treating cancer through the inhibition of SIRT1 and EMT will be discussed in detail.

SIRT1 activation promotes energy homeostasis and reprograms liver cancer metabolism

BACKGROUND

Cancer cells are characterized by uncontrolled cell proliferation and impaired bioenergetics. Sirtuins are a family of highly conserved enzymes that play a fundamental role in energy metabolism regulation. SIRT1, in particular, drives many physiological stress responses and metabolic pathways following nutrient deprivation. We previously showed that SIRT1 activation using SCIC2.1 was able to attenuate genotoxic response and senescence. Here, we report that in hepatocellular carcinoma (HCC) cells under glucose-deprived conditions, SCIC2.1 treatment induced overexpression of SIRT1, SIRT3, and SIRT6, modulating metabolic response.

METHODS

Flow cytometry was used to analyze the cell cycle. The MTT assay and xCELLigence system were used to measure cell viability and proliferation. In vitro enzymatic assays were carried out as directed by the manufacturer, and the absorbance was measured with an automated Infinite M1000 reader. Western blotting and immunoprecipitation were used to evaluate the expression of various proteins described in this study. The relative expression of genes was studied using real-time PCR. We employed a Seahorse XF24 Analyzer to determine the metabolic state of the cells. Oil Red O staining was used to measure lipid accumulation.

RESULTS

SCIC2.1 significantly promoted mitochondrial biogenesis via the AMPK-p53-PGC1α pathway and enhanced mitochondrial ATP production under glucose deprivation. SIRT1 inhibition by Ex-527 further supported our hypothesis that metabolic effects are dependent on SIRT1 activation. Interestingly, SCIC2.1 reprogrammed glucose metabolism and fatty acid oxidation for bioenergetic circuits by repressing de novo lipogenesis. In addition, SCIC2.1-mediated SIRT1 activation strongly modulated antioxidant response through SIRT3 activation, and p53-dependent stress response via indirect recruitment of SIRT6.

CONCLUSION

Our results show that SCIC2.1 is able to promote energy homeostasis, attenuating metabolic stress under glucose deprivation via activation of SIRT1. These findings shed light on the metabolic action of SIRT1 in the pathogenesis of HCC and may help determine future therapies for this and, possibly, other metabolic diseases.

The prognosis and clinicopathological significance of histone deacetylase in hepatocellular carcinoma: a meta-analysis

The value of the different types of HDACs (histone deacetylases) for HCC (hepatocellular carcinoma) prognosis and clinicopathological features is still controversial. Here, we performed a meta-analysis to investigate the possible role of different types of HDACs in HCC. Until October 28, 2021, we have searched the Embase, Cochrane, PubMed, Scopus, Web of Science (WOS), SinoMed, Chinese China National Knowledge Infrastructure (CNKI), Chinese WanFang, and Chinese Weipu databases and evaluated eligible studies according to the criteria. We used hazard ratio (HR) and 95% confidence interval (95% CI) to evaluate the prognostic effects of different types of HDACs on overall survival (OS), disease-free survival (DFS)/recurrence-free survival (RFS) and used odds ratio (OR) and corresponding 95% CI to evaluate the significance of HDACs on clinicopathological characteristics. The I2 statistic and chi-square-based Q test were used to assess the heterogeneity. When the heterogeneity was significant, we conducted a subgroup analysis. In addition, Egger's test and funnel chart were used to assess publication bias. The high expression of class I HDACs was associated with poorer OS, DFS/RFS and differentiation, intrahepatic metastasis, tumor-node-metastasis (TNM), tumor number, tumor size, vascular invasion, and other poor clinicopathological characteristics. The high expression of class II HDACs was related to poor OS and multiple and larger tumors. After subgroup analysis, class II HDACs may also be related to worse TNM and Edmondson grading. The high expression of class III HDACs was related to poor OS, hepatitis B, liver cirrhosis, serum AFP, and vascular invasion. But it was more common in women and was related to single, smaller tumors. Type I, II, and III HDACs are associated with poor prognosis, and there are also correlations with some clinicopathological features, suggesting that different types of HDACs may be valuable biomarkers for HCC.

Cancer invasion and metastasis: Insights from murine pubertal mammary gland morphogenesis

Cancer invasion and metastasis accounts for the majority of cancer related mortality. A better understanding of the players that drive the aberrant invasion and migration of tumors cells will provide critical targets to inhibit metastasis. Postnatal pubertal mammary gland morphogenesis is characterized by highly proliferative, invasive, and migratory normal epithelial cells. Identifying the molecular regulators of pubertal gland development is a promising strategy since tumorigenesis and metastasis is postulated to be a consequence of aberrant reactivation of developmental stages. In this review, we summarize the pubertal morphogenesis regulators that are involved in cancer metastasis and revisit pubertal mammary gland transcriptome profiling to uncover both known and unknown metastasis genes. Our updated list of pubertal morphogenesis regulators shows that most are implicated in invasion and metastasis. This review highlights molecular linkages between development and metastasis and provides a guide for exploring novel metastatic drivers.

Role of sirtuins in hepatocellular carcinoma progression and multidrug resistance: Mechanistical and pharmacological perspectives

Hepatocellular carcinoma (HCC) is the third most common cause of death from cancer worldwide. Therapeutic strategies are still challenging due to the high relapse rate after surgery and multidrug resistance (MDR). It is essential to better understand the mechanisms for HCC progression and MDR for the development of new therapeutic strategies. Mammalian sirtuins (SIRTs), a family of seven members, are related to tumor progression, MDR and prognosis and were proposed as potential prognostic markers, as well as therapeutic targets for treating cancer. SIRT1 is the most studied member and is overexpressed in HCC, playing an oncogenic role and predicting poor prognosis. Several manuscripts describe the role of SIRTs2-7 in HCC; most of them report an oncogenic role for SIRT2 and -7 and a suppressive role for SIRT3 and -4. The scenario is more confusing for SIRT5 and -6, since information is contradictory and scarce. For SIRT1 many inhibitors are available and they seem to hold therapeutic promise in HCC. For the other members the development of specific modulators has just started. This review is aimed to describe the features of SIRTs1-7 in HCC, and the role they play in the onset and progression of the disease. Also, when possible, we will depict the information related to the SIRTs modulators that have been tested in HCC and their possible implication in MDR. With this, we hope to clarify the role of each member in HCC and to shed some light on the most successful strategies to overcome MDR.

Overexpression of miR-4669 Enhances Tumor Aggressiveness and Generates an Immunosuppressive Tumor Microenvironment in Hepatocellular Carcinoma: Its Clinical Value as a Predictive Biomarker

Accumulating evidence suggests the involvement of tumor-derived exosomes in the development and recurrence of hepatocellular carcinoma (HCC). We previously identified miR-4669 as a highly expressed microRNA in circulating exosomes obtained from patients with post-transplant HCC recurrence. This study aimed to explore how overexpression of miR-4669 affects HCC development and recurrence. The impact of miR-4669 overexpression in Hep3B cells on tumor cell behavior and the tumor microenvironment was evaluated in vitro. In addition, the clinical value of exosomal miR-4669 for the prediction of treatment response to HCC downstaging therapies and following post-transplant HCC recurrence was explored. Overexpression of miR-4669 enhanced migration ability and led to acquired sorafenib resistance with an elevation of sirtuin 1 and long noncoding RNA associated with microvascular invasion. Active release of tumor-derived exosomes and glyceraldehyde 3-phosphate dehydrogenase (GAPDH) contributed to generating an immunosuppressive tumor microenvironment through the induction of M2 macrophage polarization. The retrospective analysis demonstrated the clinical value of exosomal miR-4669 for predicting treatment response to HCC downstaging therapies and for risk assessment of post-transplant HCC recurrence. In summary, the present data demonstrate the impact of exosomal miR-4669 on HCC recurrence through the enhancement of tumor aggressiveness and generation of an immunosuppressive tumor microenvironment.

The Interplay between Intracellular Iron Homeostasis and Neuroinflammation in Neurodegenerative Diseases

Iron is essential for life. Many enzymes require iron for appropriate function. However, dysregulation of intracellular iron homeostasis produces excessive reactive oxygen species (ROS) via the Fenton reaction and causes devastating effects on cells, leading to ferroptosis, an iron-dependent cell death. In order to protect against harmful effects, the intracellular system regulates cellular iron levels through iron regulatory mechanisms, including hepcidin-ferroportin, divalent metal transporter 1 (DMT1)-transferrin, and ferritin-nuclear receptor coactivator 4 (NCOA4). During iron deficiency, DMT1-transferrin and ferritin-NCOA4 systems increase intracellular iron levels via endosomes and ferritinophagy, respectively. In contrast, repleting extracellular iron promotes cellular iron absorption through the hepcidin-ferroportin axis. These processes are regulated by the iron-regulatory protein (IRP)/iron-responsive element (IRE) system and nuclear factor erythroid 2-related factor 2 (Nrf2). Meanwhile, excessive ROS also promotes neuroinflammation by activating the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB). NF-κB forms inflammasomes, inhibits silent information regulator 2-related enzyme 1 (SIRT1), and induces pro-inflammatory cytokines (IL-6, TNF-α, and IL-1β). Furthermore, 4-hydroxy-2,3-trans-nonenal (4-HNE), the end-product of ferroptosis, promotes the inflammatory response by producing amyloid-beta (Aβ) fibrils and neurofibrillary tangles in Alzheimer's disease, and alpha-synuclein aggregation in Parkinson's disease. This interplay shows that intracellular iron homeostasis is vital to maintain inflammatory homeostasis. Here, we review the role of iron homeostasis in inflammation based on recent findings.

The NAMPT Inhibitor FK866 in Combination with Cisplatin Reduces Cholangiocarcinoma Cells Growth

It is well established that Cholangiocarcioma (CCA) drug resistance plays a crucial role in the spread and survival of cancer cells. The major enzyme in the nicotinamide-adenine dinucleotide (NAD+)-mediated pathways, nicotinamide phosphoribosyltransferase (NAMPT), is essential for cancer cell survival and metastasis. Previous research has shown that the targeted NAMPT inhibitor FK866 reduces cancer cell viability and triggers cancer cell death; however, whether FK866 affects CCA cell survival has not been addressed before. We show herein that NAMPT is expressed in CCA cells, and FK866 suppresses the capacity of CCA cells to grow in a dose-dependent manner. Furthermore, by preventing NAMPT activity, FK866 significantly reduced the amount of NAD+ and adenosine 5'-triphosphate (ATP) in HuCCT1, KMCH, and EGI cells. The present study's findings further show that FK866 causes changes in mitochondrial metabolism in CCA cells. Additionally, FK866 enhances the anticancer effects of cisplatin in vitro. Taken together, the results of the current study suggest that the NAMPT/NAD+ pathway may be a possible therapeutic target for CCA, and FK866 may be a useful medication targeting CCA in combination with cisplatin.

Sirt1 Regulates Corneal Epithelial Migration by Deacetylating Cortactin

Purpose

Silent information regulator 1 (SIRT1) is a nicotinamide adenine dinucleotide (NAD+) dependent deacetylase, which plays an essential role in cellular metabolism, autophagy, and chromatin accessibility. Our study aimed to determine its role in controlling corneal epithelial wound healing (CEWH).

Methods

Corneal epithelial (CE)–specific Sirt1 deletion mice were created using the Cre-lox system. CE debridement was used to create a CEWH model. Corneal epithelial cells (CECs) were collected with an Algerbrush. Western blot analysis and RT-qPCR were performed to determine protein and mRNA expression levels. SiRNA transfection technology knocked down SIRT1 and cortactin expression levels in human corneal epithelial cells. Scratch wound assay, MTS assay, and TUNEL assay determined cell migratory, proliferative, and apoptotic behavior, respectively. Co-immunoprecipitation probed for SIRT1 and cortactin interaction. Immunofluorescence staining evaluated the location and expression levels of SIRT1, cortactin, acetylated-cortactin, and F-actin.

Results

During CEWH, increases in SIRT1 mRNA and protein expression levels accompanied the downregulation of acetylated lysine in non-histone proteins. The loss of SIRT1 function reduced cell migration and, in turn, delayed CEWH. SIRT1 bound to and deacetylated cortactin in vitro and in vivo. Loss of either SIRT1 or cortactin suppressed wound edge lamellipodia formation, which is consistent with migration retardation.

Conclusions

During CEWH, SIRT1 upregulation and its modification of cortactin boost CEC migration by increasing the development of lamellipodia at the wound edge. Therefore SIRT1 may serve as a potential target to enhance CEWH.

Role of Post-translational Modification of Silent Mating Type Information Regulator 2 Homolog 1 in Cancer and Other Disorders

Silent mating type information regulator 2 homolog 1 (SIRT1), an NAD⁺-dependent histone/protein deacetylase, has multifarious physiological roles in development, metabolic regulation, and stress response. Thus, its abnormal expression or malfunction is implicated in pathogenesis of various diseases. SIRT1 undergoes post-translational modifications, including phosphorylation, oxidation/reduction, carbonylation, nitrosylation, glycosylation, ubiquitination/deubiquitination, SUMOylation etc. which can modulate its catalytic activity, stability, subcellular localization, and also binding affinity for substrate proteins. This short review highlights the regulation of SIRT1 post-translational modifications and their pathophysiologic implications.

Sirtuins and Hypoxia in EMT Control

Epithelial–mesenchymal transition (EMT), a physiological process during embryogenesis, can become pathological in the presence of different driving forces. Reduced oxygen tension or hypoxia is one of these forces, triggering a large number of molecular pathways with aberrant EMT induction, resulting in cancer and fibrosis onset. Both hypoxia-induced factors, HIF-1α and HIF-2α, act as master transcription factors implicated in EMT. On the other hand, hypoxia-dependent HIF-independent EMT has also been described. Recently, a new class of seven proteins with deacylase activity, called sirtuins, have been implicated in the control of both hypoxia responses, HIF-1α and HIF-2α activation, as well as EMT induction. Intriguingly, different sirtuins have different effects on hypoxia and EMT, acting as either activators or inhibitors, depending on the tissue and cell type. Interestingly, sirtuins and HIF can be activated or inhibited with natural or synthetic molecules. Moreover, recent studies have shown that these natural or synthetic molecules can be better conveyed using nanoparticles, representing a valid strategy for EMT modulation. The following review, by detailing the aspects listed above, summarizes the interplay between hypoxia, sirtuins, and EMT, as well as the possible strategies to modulate them by using a nanoparticle-based approach.

MiRNA-124-3p.1 sensitizes hepatocellular carcinoma cells to sorafenib by regulating FOXO3a by targeting AKT2 and SIRT1

As a multikinase inhibitor, sorafenib is commonly used to treat patients with advanced hepatocellular carcinoma (HCC), however, acquired resistance to sorafenib is a major obstacle to the effectiveness of this treatment. Thus, in this study, we investigated the mechanisms underlying sorafenib resistance as well as approaches devised to increase the sensitivity of HCC to sorafenib. We demonstrated that miR-124-3p.1 downregulation is associated with early recurrence in HCC patients who underwent curative surgery and sorafenib resistance in HCC cell lines. Regarding the mechanism of this phenomenon, we identified FOXO3a, an important cellular stress transcriptional factor, as the key factor in the function of miR-124-3p.1 in HCC. We showed that miR-124-3p.1 binds directly to AKT2 and SIRT1 to reduce the levels of these proteins. Furthermore, we showed that AKT2 and SIRT1 phosphorylate and deacetylate FOXO3a. We also found that miR-124-3p.1 maintains the dephosphorylation and acetylation of FOXO3a, leading to the nuclear location of FOXO3a and enhanced sorafenib-induced apoptosis. Moreover, the combination of miR-124-3p.1 mimics and sorafenib significantly enhanced the curative efficacy of sorafenib in a nude mouse HCC xenograft model. Collectively, our data reveal that miR-124-3p.1 represents a predictive indicator of early recurrence and sorafenib sensitivity in HCC. Furthermore, we demonstrate that miR-124-3p.1 enhances the curative efficacy of sorafenib through dual effects on FOXO3a. Thus, the miR-124-3p.1-FOXO3a axis is implicated as a potential target for the diagnosis and treatment of HCC.

Ginsenoside CK Inhibits TGF-β-Induced Epithelial-Mesenchymal Transition in A549 Cell via SIRT1

Ginsenoside CK is the main metabolite of protopanaxadiol saponins in intestinal bacteria. Previous studies have shown that ginsenoside CK can affect many aspects of tumor development through a variety of mechanisms. However, few studies have reported the antimetastatic effects of ginsenoside CK in non-small-cell lung cancer (NSCLC). In this study, we explored the effect of ginsenoside CK on epithelial-mesenchymal transition (EMT) induced by TGF-β in A549 cells and the potential molecular mechanisms. Our data showed that ginsenoside CK effectively prevented TGF-β-induced EMT, as indicated by the upregulation of E-cadherin and downregulation of vimentin. Furthermore, ginsenoside CK inhibited the metastatic ability of A549 cells in the tail vein lung metastasis model of nude mice. Additionally, ginsenoside CK decreased the expression of silent information regulator 2 homolog 1 (SIRT1) in the inhibition of EMT induced by TGF-β. Moreover, the antimetastatic effect of ginsenoside CK was reversed by SIRT1 overexpression. Generally, our results indicated the antimetastatic effect and underlying mechanism of ginsenoside CK on TGF-β-induced EMT in A549 cells, suggesting that ginsenoside CK can be used as an effective antineoplastic agent.

Histone Deacetylase Sirtuin 1 Promotes Loss of Primary Cilia in Cholangiocarcinoma

BACKGROUND AND AIMS

Sirtuin 1 (SIRT1) is a complex NAD⁺ -dependent protein deacetylase known to act as a tumor promoter or suppressor in different cancers. Here, we describe a mechanism of SIRT1-induced destabilization of primary cilia in cholangiocarcinoma (CCA).

APPROACH AND RESULTS

A significant overexpression of SIRT1 was detected in human CCA specimens and CCA cells including HuCCT1, KMCH, and WITT1 as compared with normal cholangiocytes (H69 and NHC). Small interfering RNA (siRNA)-mediated knockdown of SIRT1 in HuCCT1 cells induced cilia formation, whereas overexpression of SIRT1 in normal cholangiocytes suppressed ciliary expression. Activity of SIRT1 was regulated by presence of NAD+ in CCA cells. Inhibition of NAD -producing enzyme nicotinamide phosphoribosyl transferase increased ciliary length and frequency in CCA cells and in SIRT1-overexpressed H69 cells. Furthermore, we also noted that SIRT1 induces the proteasomal mediated degradation of ciliary proteins, including α-tubulin, ARL13B, and KIF3A. Moreover, overexpression of SIRT1 in H69 and NHC cells significantly induced cell proliferation and, conversely, SIRT1 inhibition in HuCCT1 and KMCH cells using siRNA or sirtinol reduced cell proliferation. In an orthotopic transplantation rat CCA model, the SIRT1 inhibitor sirtinol reduced tumor size and tumorigenic proteins (glioma-associated oncogene 1, phosphorylated extracellular signal-regulated kinase, and IL-6) expression.

CONCLUSIONS

In conclusion, these results reveal the tumorigenic role of SIRT1 through modulation of primary cilia formation and provide the rationale for developing therapeutic approaches for CCA using SIRT1 as a target.

Novel oncogenes and tumor suppressor genes in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a very deadly disease. HCC initiation and progression involve multiple genetic events, including the activation of proto-oncogenes and disruption of the function of specific tumor suppressor genes. Activation of oncogenes stimulates cell growth and survival, while loss-of-function mutations of tumor suppressor genes result in unrestrained cell growth. In this review, we summarize the new findings that identified novel proto-oncogenes and tumor suppressors in HCC over the past five years. These findings may inspire the development of novel therapeutic strategies to improve the outcome of HCC patients.

Trending topics of SIRT1 in tumorigenicity

BACKGROUND

Carcinogenesis is governed by a series of genetic alterations and epigenetic changes that lead to aberrant patterns in neoplastic cells. Sirtuin-1(SIRT1), an NAD⁺-dependent protein deacetylase, is capable of deacetylating histones and non-histone substrates that regulate various physiological activities during tumorigenesis. Recent studies have identified the role of SIRT1 in different stages of cancer, including genome instability, tumor initiation, proliferation, metabolism, and therapeutic response. However, the action of SIRT1 has been reported to be both oncogenic and tumor suppressive during carcinogenesis. Consequently, the biological functions of SIRT1 in cancer remain controversial.

SCOPE OF REVIEW

We highlight the most recent findings on SIRT1 in different stages of tumorigenesis, and update the current status of SIRT1 small molecule modulators in clinical application of cancer treatment.

MAJOR CONCLUSION

By targeting both tumor suppressors and oncogenic proteins, SIRT1 has a bifunctional role at different stages of tumorigenesis. The impact of SIRT1 on tumorigenesis is also distinct at different stages and is dependent on its dosages. SIRT1 suppresses tumor initiation through its functions in promoting DNA repair, increasing genome stability, and inhibiting inflammation at the pre-cancer stage. However, SIRT1 enhances tumor proliferation, survival, and drug resistance through its roles in anti-apoptosis, pro-tumor metabolism, and anti-inflammation (inhibition of anti-tumor immunity) at the stages of tumor progression, metastasis, and relapse. Consequently, both SIRT1 inhibitors and activators have been explored for cancer treatment.

GENERAL SIGNIFICANCE

Better understanding the dose- and stage-dependent roles of SIRT1 in each cancer type can provide new avenues of exploration for therapy development.

Nicotinamide N-Methyltransferase in Acquisition of Stem Cell Properties and Therapy Resistance in Cancer

The activity of nicotinamide N-methyltransferase (NNMT) is tightly linked to the maintenance of the nicotinamide adenine dinucleotide (NAD⁺) level. This enzyme catalyzes methylation of nicotinamide (NAM) into methyl nicotinamide (MNAM), which is either excreted or further metabolized to N1-methyl-2-pyridone-5-carboxamide (2-PY) and H₂O₂. Enzymatic activity of NNMT is important for the prevention of NAM-mediated inhibition of NAD⁺-consuming enzymes poly-adenosine -diphosphate (ADP), ribose polymerases (PARPs), and sirtuins (SIRTs). Inappropriately high expression and activity of NNMT, commonly present in various types of cancer, has the potential to disrupt NAD⁺ homeostasis and cellular methylation potential. Largely overlooked, in the context of cancer, is the inhibitory effect of 2-PY on PARP-1 activity, which abrogates NNMT's positive effect on cellular NAD⁺ flux by stalling liberation of NAM and reducing NAD⁺ synthesis in the salvage pathway. This review describes, and discusses, the mechanisms by which NNMT promotes NAD⁺ depletion and epigenetic reprogramming, leading to the development of metabolic plasticity, evasion of a major tumor suppressive process of cellular senescence, and acquisition of stem cell properties. All these phenomena are related to therapy resistance and worse clinical outcomes.

Targeting Sirtuin 1 signaling pathway by ginsenosides

ETHNOPHARMACOLOGICAL RELEVANCE

Ginseng is a kind of traditional Chinese herbal medicine, known as "king of herbs" and widely used in China, South Korea, and other Asian countries. Ginsenosides are one of active components of Panax ginseng Meyer, which have many pharmacological effects, such as enhancing memory, improving immunity and cardiovascular system, delaying aging, and preventing cancer.

AIMS OF THE REVIEW

This review aims to summarize the recent findings for ginsenosides targeting Sirtuin 1 (SIRT1) signaling pathway for the prevention and treatment of a series of diseases.

MATERIALS AND METHODS

An up-to-August 2020 search was carried out in databases such as PubMed, ScienceDirect, Google Scholar, China National Knowledge Infrastructure, and classic books of traditional Chinese medicine using the keywords: "SIRT1", and/or paired with "ginseng", and "ginsenosides".

RESULTS

SIRT1 is a class-III histone deacetylase (HDAC), a nicotinamide adenine dinucleotide (NAD⁺)-dependent enzyme, which is deeply involved in a series of pathological processes. Based on specific intracellular localization, SIRT1 has various cytoplasmic and nuclear targets and plays a potential role in energy metabolism, oxidative stress, inflammation, tumorigenesis, and aging. Ginsenosides are generally classified into three groups and microbially transformed to final metabolites. Among of them, most ginsenosides have been reported as SIRT1 activators, especially those ginsenosides with two glucopyranosyl groups on the C-3 position. Importantly, many ginsenosides can be used to prevent and treat oxidative stress, inflammation, aging, tumorigenesis, depression, and others by targeting SIRT1 signaling pathway.

CONCLUSIONS

This paper reviews recent evidences of ginsenosides targeting SIRT1 for the first time, which could provide new insights on the preclinical and clinical researches for ginsenosides against multiple disorders.

SIRT1 is involved in adrenocortical cancer growth and motility

Adrenocortical cancer (ACC) is a rare tumour with unfavourable prognosis, lacking an effective treatment. This tumour is characterized by IGF‐II (insulin‐like growth factor II) overproduction, aromatase and ERα (oestrogen receptor alpha) up‐regulation. Previous reports suggest that ERα expression can be regulated by sirt1 (sirtuin 1), a nicotinamide adenine dinucleotide (NAD+)‐dependent class III histone deacetylases that modulates activity of several substrates involved in cellular stress, metabolism, proliferation, senescence, protein degradation and apoptosis. Nevertheless, sirt1 can act as a tumour suppressor or oncogenic protein. In this study, we found that in H295R and SW13 cell lines, sirt1 expression is inhibited by sirtinol, a potent inhibitor of sirt1 activity. In addition, sirtinol is able to decrease ACC cell proliferation, colony and spheroids formation and to activate the intrinsic apoptotic mechanism. Particularly, we observed that sirtinol interferes with E2/ERα and IGF1R (insulin growth factor 1 receptor) pathways by decreasing receptors expression. Sirt1 involvement was confirmed by using a specific sirt1 siRNA. More importantly, we observed that sirtinol can synergize with mitotane, a selective adrenolitic drug, in inhibiting adrenocortical cancer cell growth. Collectively, our data reveal an oncogenic role for sirt1 in ACC and its targeting could implement treatment options for this type of cancer.

Nicotinamide N-methyltransferase: At the crossroads between cellular metabolism and epigenetic regulation

Background

The abundance of energy metabolites is intimately interconnected with the activity of chromatin-modifying enzymes in order to guarantee the finely tuned modulation of gene expression in response to cellular energetic status. Metabolism-induced epigenetic gene regulation is a key molecular axis for the maintenance of cellular homeostasis, and its deregulation is associated with several pathological conditions. Nicotinamide N-methyltransferase (NNMT) is a metabolic enzyme that catalyzes the methylation of nicotinamide (NAM) using the universal methyl donor S-adenosyl methionine (SAM), directly linking one-carbon metabolism with a cell's methylation balance and nicotinamide adenine dinucleotide (NAD⁺) levels. NNMT expression and activity are regulated in a tissue-specific-manner, and the protein can act either physiologically or pathologically depending on its distribution. While NNMT exerts a beneficial effect by regulating lipid parameters in the liver, its expression in adipose tissue correlates with obesity and insulin resistance. NNMT upregulation has been observed in a variety of cancers, and increased NNMT expression has been associated with tumor progression, metastasis and worse clinical outcomes. Accordingly, NNMT represents an appealing druggable target for metabolic disorders as well as oncological and other diseases in which the protein is improperly activated.

Scope of review

This review examines emerging findings concerning the complex NNMT regulatory network and the role of NNMT in both NAD metabolism and cell methylation balance. We extensively describe recent findings concerning the physiological and pathological regulation of NNMT with a specific focus on the function of NNMT in obesity, insulin resistance and other associated metabolic disorders along with its well-accepted role as a cancer-associated metabolic enzyme. Advances in strategies targeting NNMT pathways are also reported, together with current limitations of NNMT inhibitor drugs in clinical use.

Major conclusions

NNMT is emerging as a key point of intersection between cellular metabolism and epigenetic gene regulation, and growing evidence supports its central role in several pathologies. The use of molecules that target NNMT represents a current pharmaceutical challenge for the treatment of several metabolic-related disease as well as in cancer.

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.

ROS-Induced SIRT2 Upregulation Contributes to Cisplatin Sensitivity in Ovarian Cancer

Cisplatin resistance remains a significant obstacle for improving the clinical outcome of ovarian cancer patients. Recent studies have demonstrated that cisplatin is an important inducer of intracellullar reactive oxygen species (ROS), triggering cancer cell death. Sirtuin 2 (SIRT2), a member of class III NAD⁺ dependent histone deacetylases (HDACs), has been reported to be involved in regulating cancer hallmarks including drug response. In this study, we aimed to identify the role of SIRT2 in oxidative stress and cisplatin response in cancer. Two ovarian cancer cell lines featuring different sensitivities to cisplatin were used in this study. We found different expression patterns of SIRT2 in cisplatin-sensitive (A2780/S) and cisplatin-resistant (A2780/CP) cancer cells with cisplatin treatment, where SIRT2 expression was augmented only in A2780/S cells. Furthermore, cisplatin-induced ROS generation was responsible for the upregulation of SIRT2 in A2780/S cells, whereas overexpression of SIRT2 significantly enhanced the sensitivity of cisplatin-resistant counterpart cells to cisplatin. Our study proposes that targeting SIRT2 may provide new strategies to potentiate platinum-based chemotherapy in ovarian cancer patients.

Epigenetic reprogramming of epithelial-mesenchymal transition promotes ferroptosis of head and neck cancer

Ferroptosis is a newly defined form of cell death induced by iron-dependent accumulation of lethal lipid peroxidation. Ferroptosis represent a therapeutic strategy to suppress therapy-resistant cancer cells with more property of epithelial-mesenchymal transition (EMT). However, epigenetic reprogramming of EMT has been rarely studied in the context of ferroptosis susceptibility. Therefore, we examined the therapeutic potentiality of EMT epigenetic reprogramming in promoting ferroptosis in head and neck cancer (HNC) cells. The effects of ferroptosis inducers and EMT inhibition or induction were tested in HNC cell lines and mouse tumor xenograft models. These effects were analyzed concerning cell viability and death, lipid reactive oxygen species and iron production, labile iron pool, glutathione contents, NAD/NADH levels, and mRNA/protein expression. Cell density and the expression levels of E-cadherin, vimentin, and ZEB1 were associated with the different susceptibility to ferroptosis inducers. CDH1 silencing or ZEB1 overexpression increased the susceptibility to ferroptosis, whereas CDH overexpression or ZEB1 silencing decreased the susceptibility, in vitro and in vivo. Histone deacetylase SIRT1 gene silencing or pharmacological inhibition by EX-527 suppressed EMT and consequently decreased ferroptosis, whereas SIRT inducers, resveratrol and SRT1720, increased ferroptosis. MiR-200 family inhibitors induced EMT and increased ferroptosis susceptibility. In HNC cells with low expression of E-cadherin, the treatment of 5-azacitidine diminished the hypermethylation of CDH1, resulting in increased E-cadherin expression and decreased ferroptosis susceptibility. Our data suggest that epigenetic reprogramming of EMT contributes to promoting ferroptosis in HNC cells.

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The EMT markers of E-cadherin and ZEB1 were closely related to ferroptosis susceptibility.

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Transition to epithelial traits by CDH overexpression or ZEB1 silencing decreased ferroptosis.

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Gaining of mesenchymal traits by CDH1 silencing or ZEB overexpression increased ferroptosis.

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SIRT1 activation or miR-200 family inhibition shifted HNC to EMT and increased ferroptosis.

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5-Azacitidine induced CDH1 demethylation that contributed to reducing EMT and decreasing ferroptosis.

Role of Sirtuin-1 in Neonatal Hypoxic-Ischemic Encephalopathy and Its Underlying Mechanism

Background

Neonatal hypoxic-ischemic encephalopathy (HIE) is a dreaded disease and one of the leading causes of severe neurological dysfunction in neonates. The present study explored the functions of Sirtuin-1 (SIRT1) in neonatal HIE.

Material/Methods

A HIE neonatal rat model was generated to determine SIRT1 levels in brain tissues. Cell apoptosis and cell viability were analyzed by flow cytometry and MTT assay. qRT-PCR and Western blot analysis were used to assess gene mRNA and protein levels. Subsequently, the effect of SIRT1 on HIE was investigated in vitro by constructing an oxygen-glucose deprivation (OGD) cell model.

Results

The effective construction of the HIE rat model was confirmed by the enhanced brain cell apoptosis and the increased expression of HIE-related molecular markers, including S100 calcium-binding protein B (S100B) and neuron-specific enolase (NSE). SIRT1 expression was downregulated in HIE rat brain tissues. These findings indicated that SIRT1 was downregulated in neuronal cells subjected to OGD. In addition, enhanced cell viability and reduced cell apoptosis were observed, suggesting that SIRT1 overexpression relieved OGD-induced neuronal cell injury. Transfection with SIRT1-siRNA further increased OGD-induced neuronal cell injury, evidenced by decreased cell viability and enhanced cell apoptosis. Finally, SIRT1 overexpression significantly downregulated p-p65 protein expression.

Conclusions

Our findings revealed that SIRT1 may be a novel and promising therapy target for HIE treatment.

Hepatocellular Expression of SIRT1 and Its Effect on Hepatocellular Carcinoma Progression: A Future Therapeutic Perspective

Hepatocellular carcinoma (HCC) is an aggressive primary hepatic malignancy with a significant morbidity and mortality rate. Although chemotherapy along with surgical incision is believed to be an effective therapeutic approach, to date recurrence is being lifted a major concern. Thus, identifying another best therapeutic approach is becoming the main aim of physicians and scholars. In support of this, recently, several studies reported a significant observation of Sirtuin1 (SIRT1) overexpression in the malignant tumor cells, including HCC. As a result, they believed that overexpression of SIRT1 may have an effect on the progression of HCC by targeting growth and/or apoptotic controlling transcriptional factors/signaling pathways. Similarly, other reports confirmed that SIRT1 inhibition had a direct or indirect role in the control of tumor cell growth and metastasis. Therefore, inhibiting the expression and activity of SIRT1 might have a therapeutic effect to handle HCC. However, there are a limited number of reviews regarding the issue, and here, we summarized hepatocellular expression of SIRT1 and its role on HCC progression.

HBx mediated Increase of SIRT1 Contributes to HBV-related Hepatocellular Carcinoma Tumorigenesis

Objective: Hepatocellular carcinoma (HCC) is one of the main causes of cancer-related deaths worldwide, and chronic hepatitis B virus (HBV) infection is strongly associated with HCC development, but the pathogenesis of HBV-related HCC remains obscure. Sirtuin 1 (SIRT1) has been implicated to enhance the replication of HBV and to promote the tumorigenesis of HCC. In this study, we aim to investigate the functional role of SIRT1 on HBV viral protein and HBV-induced HCC. Methods: Tumorous liver tissues from patient diagnosed with HBV-related HCC were collected and further divided into two groups (with or without metastasis). Then, the mRNA and protein level of SIRT1 in those tissues were detected by real time PCR and Western blot, respectively. Meanwhile, the protein level of epithelial-mesenchymal transition (EMT) relative markers in those tissues was determined by Western blot. Furthermore, the expression of SIRT1 in HBV-expressing HCC cells was examined. Next, the relationship between viral proteins and SIRT1 expression were determined by real time PCR and Western blot. In addition, the potential role of HBx-upregulated SIRT1 in HCC proliferation, migration and invasion were analyzed by cell viability assays, cell proliferation assay, wound healing assay, transwell assay and Western blot. Results: In this study, we found that the expression of SIRT1 was obviously increased in patients with metastasis compared to the patients without metastasis. Consistently, the expression of SIRT1 was also upregulated in HBV-expressing HCC cells compared to the controls. Further investigation showed that viral protein HBx was responsible for the elevated SIRT1 in HBV-expressing HCC cells. Meanwhile, the expression of HBx could be upregulated by SIRT1. Additionally, functional studies showed that HBx-elevated SIRT1 could promote HCC cell proliferation, migration and invasion. Importantly, HBx induced HCC proliferation and migration could be suppressed by Nicotinamide in a dose dependent manner. Conclusions: Our findings uncovered the positive role of SIRT1 in HBx-mediated tumorigenesis which implicated the potential role of SIRT1 in HBV-related HCC treatment.

Association between different levels of lipid metabolism‑related enzymes and fatty acid synthase in Wilms' tumor

Wilms’ tumor is one of the most common malignant tumors of the abdomen in children. However, there is currently no recognized specific biomarker for the clinical diagnosis and prognosis of this tumor. Lipid metabolism is involved in membrane synthesis and oxidation in tumor cells. This process plays an important role in the development of tumors, but it has not yet been investigated in Wilms’ tumor. The aim of the present study was to characterize the changes in lipid metabolism and to contribute to the diagnosis and prognosis of Wilms’ tumor. Proteomics analysis was performed to detect lipid-metabolizing enzymes in 9 tissue samples from Wilms’ tumors and adjacent tissues, and proteomics revealed the presence of 19 differentially expressed lipid-metabolizing enzymes. Protein interaction analysis with the Search Tool for the Retrieval of Interacting Genes/Proteins was used to identify the interacting proteins. Immunohistochemistry (IHC), immunofluorescence and western blotting were used to further confirm whether the expression of fatty acid synthase (FASN) was significantly increased in the tumor tissues. Oncomine database and reverse transcription-PCR analyses further confirmed that the expression of FASN at the gene level was significantly increased in the tumors. Following collection of 65 pediatric cases of Wilms’ tumor at the Shandong Provincial Hospital between 2007 and 2012, the association between the expression of FASN and the clinical characteristics was analyzed, and IHC analysis further demonstrated that FASN expression was significantly associated with tumor stage and size. The association between FASN and the prognosis of children with Wilms’ tumor was analyzed using Kaplan-Meier survival curves. In addition, univariate survival analysis revealed that higher expression of FASN in Wilms’ tumors was associated with poorer prognosis. Our findings revealed that FASN may be used as a prognostic biomarker in patients with Wilms’ tumor. Furthermore, lipid metabolism may play an important role in the occurrence and development of Wilms’ tumor.

Deubiquitinating enzyme USP10 promotes hepatocellular carcinoma metastasis through deubiquitinating and stabilizing Smad4 protein

Hepatocellular carcinoma (HCC) has emerged as one of the most prevalent life-threatening cancers, and the high mortality rate is largely due to the metastasis. The sustained activation of Smad4 and transforming growth factor-β (TGF-β) is closely associated with advanced HCC metastasis. However, the regulatory mechanism underlying the aberrant activation of Smad4 and TGF-β pathway remains elusive. In this study, using a functional screen of USPs siRNA library, we identified ubiquitin-specific proteases USP10 as a deubiquitinating enzyme (DUB) that sustains the protein level of Smad4 and activates TGF-β signaling. Further analysis showed that USP10 directly interacts with Smad4 and stabilizes it through the cleavage of its proteolytic ubiquitination, thus promoting HCC metastasis. The suppression of USP10 by either shRNAs or catalytic inhibitor Spautin-1 significantly inhibited the migration of HCC cells, whereas the reconstitution of Smad4 was able to efficiently rescue this defect. Overall, our study not only uncovers the regulatory effect of USP10 on the protein abundance of Smad4, but also indicates that USP10 could be regarded as a potential intervention target for the metastatic HCC in Smad4-positive patients.

SIRT1 in the Development and Treatment of Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is one of the most common causes of cancer-related death worldwide. Current treatment options for inoperable HCCs have decreased therapeutic efficacy and are associated with systemic toxicity and chemoresistance. Sirtuin 1 (SIRT1) is a nicotinamide adenine dinucleotide–dependent enzyme that is frequently overexpressed in HCC, where it promotes tumorigenicity, metastasis, and chemoresistance. SIRT1 also maintains the tumorigenic and self-renewal proprieties of liver cancer stem cells. Multiple tumor-suppressive microRNAs (miRNAs) are downregulated in HCC and, as a consequence, permit SIRT1-induced tumorigenicity. However, either directly targeting SIRT1, combining conventional chemotherapy with SIRT1 inhibitors, or upregulating tumor-suppressive miRNAs may improve therapeutic efficacy and patient outcomes. Here, we present the interaction between SIRT1, miRNAs, and liver cancer stem cells and discuss the consequences of their interplay for the development and treatment of HCC.

RNA-binding protein RPS3 contributes to hepatocarcinogenesis by post-transcriptionally up-regulating SIRT1

Although several studies indicate that RNA-binding proteins (RBPs) contribute to key steps in a variety of physiological processes and cancer, the detailed biological functions and mechanisms remain to be determined. By performing bioinformatics analysis using well-established hepatocellular carcinoma (HCC) datasets, we identified a set of HCC progression-associated RBPs (HPARBPs) and found that the global expression of HPARBPs was significantly correlated with patient prognosis. Among the 42 HPARBPs, human ribosomal protein S3 (RPS3) was one of the most abundant genes whose role remains uncharacterized in HCC. Gain- and loss-of-function analyses demonstrated that RPS3 promoted HCC tumorigenesis both in vitro and in vivo. Mechanistically, we revealed that silent information regulator 1 (SIRT1) was a critical target of RPS3 and was essential for sustaining the RPS3-induced malignant phenotypes of HCC cells. RPS3 stabilized SIRT1 mRNA by binding to AUUUA motifs in the 3448–3530 region of the 3′ untranslated region (UTR) of SIRT1 mRNA. In addition, we found that (5-formylfuran-2-yl) methyl 4-hydroxy-2-methylenebutanoate (FMHM) inhibited HCC progression by repressing the RPS3/SIRT1 pathway. Our study unveils a novel extra-ribosomal role of RPS3 in facilitating hepatocarcinogenesis via the post-transcriptional regulation of SIRT1 expression and proposes that the RPS3/SIRT1 pathway serves as a potential therapeutic target in HCC.

SIRT1 Modulators in Experimentally Induced Liver Injury

This article is directed at highlighting the involvement of the endogenous stress sensor SIRT1 (silent information regulator T1) as a possible factor involved in hepatoprotection. The selective SIRT1 modulators whether activators (STACs) or inhibitors are being tried experimentally and clinically. We discuss the modulation of SIRT1 on cytoprotection or even cytotoxicity in the liver chemically injured by hepatotoxic agents in rats, to shed light on the crosstalk between SIRT1 and its modulators. A combination of D-galactosamine and lipopolysaccharide (D-GalN/LPS) downregulated SIRT1 expression, while SIRT1 activators, SRT1720, resveratrol, and quercetin, upregulated SIRT1 and alleviated D-GalN/LPS-induced acute hepatotoxicity. Liver injury markers exhibited an inverse relationship with SIRT1 expression. However, under subchronic hepatotoxicity, quercetin decreased the significant increase in SIRT1 expression to lower levels which are still higher than normal ones and mitigated the liver-damaging effects of carbon tetrachloride. Each of these STACs was hepatoprotective and returned the conventional antioxidant enzymes to the baseline. Polyphenols tend to fine-tune SIRT1 expression towards normal in the liver of intoxicated rats in both acute and subchronic studies. Together, all these events give an impression that the cytoprotective effects of SIRT1 are exhibited within a definite range of expression. The catalytic activity of SIRT1 is important in the hepatoprotective effects of polyphenols where SIRT1 inhibitors block and the allosteric SIRT1 activators mimic the hepatoprotective effects of polyphenols. Our findings indicate that the pharmacologic modulation of SIRT1 could represent both an important move in alleviating hepatic insults and a future major step in the treatment of xenobiotic-induced hepatotoxicity.

Capsaicin attenuates cell migration via SIRT1 targeting and inhibition to enhance cortactin and β-catenin acetylation in bladder cancer cells

We have studied the chemopreventive property of capsaicin, a major active component in chili pepper, and found that it exhibited apoptotic activity against various lines of cancer cells. Interestingly, accumulating data has revealed that, in addition to cytotoxicity, capsaicin also plays regulatory role on cell migration and invasion. However, its effect on cell migration is paradoxical and not completely understood. Here, we set out to elucidate the molecular events underlying capsaicin-inhibited cell migration in bladder cancer cells. Our results show that the capsaicin-reduced cell migration was associated with down-regulation of sirtuin 1 (SIRT1) deacetylase, possibly through proteasome-mediated protein degradation. More importantly, we employed a cellular thermal shift assay (CETSA) to demonstrate that there was a direct binding between capsaicin and SIRT1. The engagement with capsaicin and protein degradation diminished the deacetylase of SIRT1, which in turn, enhanced acetylation of cortactin and β-catenin to decrease MMP-2 and MMP-9 activation, resulting in cell migration impairment in bladder cancer cells.

20(S)-Protopanaxadiol Inhibits Angiotensin II-Induced Epithelial- Mesenchymal Transition by Downregulating SIRT1

20(S)-Protopanaxadiol (PPD) is one of the major active metabolites in ginseng saponin. Our previous studies revealed a broad spectrum of antitumor effects of PPD. Angiotensin II (Ang II), the biologically active peptide of the renin-angiotensin system (RAS), plays a critical role in the metastasis of various cancers. However, its role in the anti-metastatic effects of PPD is not clearly understood. In this study, we investigated the inhibitory effect of PPD on Ang II-induced epithelial-mesenchymal transition (EMT) in non-small cell lung cancer (NSCLC) cells, and the potential molecular mechanisms of suppression of NSCLC migration and metastasis by PPD. Treatment of A549 cells with Ang II increased metastases in an experimental model of cancer metastasis in vivo. PPD effectively prevented Ang II-induced EMT, as indicated by upregulation of E-cadherin and downregulation of vimentin. Additionally, Ang II upregulated the class III deacetylase sirtuin 1 (SIRT1) expression in EMT progression, while downregulation of SIRT1 was involved in suppression of Ang II-induced EMT by PPD. Moreover, the inhibitory effect of PPD was reversed by SIRT1 upregulation, and PPD demonstrated synergy with an SIRT1 inhibitor on Ang II-induced EMT. Taken together, our data reveal the mechanism of the anti-metastatic effects of PPD on Ang II-induced EMT and indicate that PPD can be used as an effective anti-tumor treatment.

SIRT1: a potential tumour biomarker and therapeutic target

SIRT1, which is highly homologous to yeast silent information regulator 2, has recently garnered tremendous attention because of its various regulatory effects in several pathological conditions. Numerous studies have found that SIRT1 is highly expressed in a broad range of tumours compared with the paracancerous tissue. However, the role of SIRT1 in malignancies has yet to be systematically elucidated, and its use as a promising biomarker or therapeutic target for tumours has not been well-reported. Herein, we focus on the roles of SIRT1 in cancers and summarise the potential use of SIRT1 as a promising tumour biomarker or therapeutic target.

Unmasking the pathological and therapeutic potential of histone deacetylases for liver cancer

Hepatocellular carcinoma (HCC) is the most common form of primary liver cancer, currently ranking as one of the highest neoplastic-related mortalities in the world. Due to the difficulty in early diagnosis and lack of effective treatment options, the 5-year survival rate of HCC remains extremely low. Histone deacetylation is one of the most important epigenetic mechanisms, regulating cellular events such as differentiation, proliferation and cell cycle. Histone deacetylases (HDACs), the chief mediators of this epigenetic mechanism, are often aberrantly expressed in various tumours including HCC. Areas covered: This review focuses on the most up-to-date findings of HDACs and their associated molecular mechanisms in HCC onset and progression. In addition, a potential network between HDACs and non-coding RNAs including microRNAs and long noncoding RNAs underlying hepatocarcinogenesis is considered. Expert opinion: Unmasking the role of HDACs and their association with HCC pathogenesis could have implications for future personalized therapeutic and diagnostic targeting.

Dual Tumor Suppressor and Tumor Promoter Action of Sirtuins in Determining Malignant Phenotype

Sirtuins (SIRTs), class III histone deacetylases, are differentially expressed in several human cancers, where they display both oncogenic and tumor-suppressive properties depending on cellular context and experimental conditions. SIRTs are involved in many important biological processes and play a critical role in cancer initiation, promotion, and progression. A growing body of evidence indicates the involvement of SIRTs in regulating three important tumor processes: epithelial-to-mesenchymal transition (EMT), invasion, and metastasis. Many SIRTs are responsible for cellular metabolic reprogramming and drug resistance by inactivating cell death pathways and promoting uncontrolled proliferation. In this review, we summarize current knowledge on the role of SIRTs in cancer and discuss their puzzling dual function as tumor suppressors and tumor promoters, important for the future development of novel tailored SIRT-based cancer therapies.

Retracted Article: MicroRNA-1271 modulates hepatitis B virus replication, cell proliferation and apoptosis in hepatitis B virus-related hepatocellular carcinoma by targeting SIRT1

Chronic hepatitis B virus (HBV) infection is a leading cause of hepatocellular carcinoma (HCC). Certain studies have revealed that microRNAs play crucial roles in HBV-related HCC. The aim of this study was to investigate the effects of microRNA-1271 (miR-1271) on HBV replication, cell proliferation and apoptosis in HBV-related HCC. The expression of HBV DNA and miR-1271 was detected by quantitative real time-polymerase chain reaction (qRT-PCR). The mRNA and protein levels of SIRT1 were detected by qRT-PCR and western blot analysis, respectively. HBV replication was assessed by the expression of HBV DNA and the levels of HBsAg and HBeAg. Cell proliferation was assessed by cell counting kit-8 (CCK-8) and 5-bromo-2-deoxyuidine (BrdU) assay, and apoptosis was evaluated by flow cytometry assay, enzyme-linked immunosorbent assay (ELISA) and the activity of caspase-3. The relationship between miR-1271 and SIRT1 was predicated by online software and confirmed by dual-luciferase reporter assay, RNA immunoprecipitation (RIP) and pull-down assay. We first found that the expression of miR-1271 was downregulated and SIRT1 was upregulated in both HBV-related HCC tissues and cells. Overexpression of miR-1271 inhibited HBV replication and cell proliferation whilst promoting apoptosis in HBV-related HCC cells. Subsequently, SIRT1 was identified as a target of miR-1271. Moreover, overexpression of SIRT1 reversed the effects of miR-1271 overexpression on HBV replication, cell proliferation and apoptosis in HBV-related HCC cells. In conclusion, our study demonstrated that miR-1271 inhibited HBV replication and proliferation and promoted apoptosis of HBV-related HCC cells via targeting SIRT1, which might contribute to the diagnosis and therapy of HBV-related HCC.

MiR-1271 suppressed HBV-related HCC cells development by downregulating SIRT1.

Survival and Clinicopathological Significance of SIRT1 Expression in Cancers: A Meta-Analysis

Background: Silent information regulator 2 homolog 1 (SIRT1) is an evolutionarily conserved enzymes with nicotinamide adenine dinucleotide (NAD)⁺-dependent deacetylase activity. SIRT1 is involved in a large variety of cellular processes, such as genomic stability, energy metabolism, senescence, gene transcription, and oxidative stress. SIRT1 has long been recognized as both a tumor promoter and tumor suppressor. Its prognostic role in cancers remains controversial. Methods: A meta-analysis of 13,138 subjects in 63 articles from PubMed, EMBASE, and Cochrane Library was performed to evaluate survival and clinicopathological significance of SIRT1 expression in various cancers. Results: The pooled results of meta-analysis showed that elevated expression of SIRT1 implies a poor overall survival (OS) of cancer patients [Hazard Ratio (HR) = 1.566, 95% CI: 1.293-1.895, P < 0.0001], disease free survival (DFS) (HR = 1.631, 95% CI: 1.250-2.130, P = 0.0003), event free survival (EFS) (HR = 2.534, 95% CI: 1.602-4.009, P = 0.0001), and progress-free survival (PFS) (HR = 3.325 95% CI: 2.762-4.003, P < 0.0001). Elevated SIRT1 level was associated with tumor stage [Relative Risk (RR) = 1.299, 95% CI: 1.114-1.514, P = 0.0008], lymph node metastasis (RR = 1.172, 95% CI: 1.010-1.360, P = 0.0363), and distant metastasis (RR = 1.562, 95% CI: 1.022-2.387, P = 0.0392). Meta-regression and subgroup analysis revealed that ethnic background has influence on the role of SIRT1 expression in predicting survival and clinicopathological characteristics of cancers. Overexpression of SIRT1 predicted a worse OS and higher TNM stage and lymphatic metastasis in Asian population especially in China. Conclusion: Our data suggested that elevated expression of SIRT1 predicted a poor OS, DFS, EFS, PFS, but not for recurrence-free survival (RFS) and cancer-specific survival (CCS). SIRT1 overexpression was associated with higher tumor stage, lymph node metastasis, and distant metastasis. SIRT1-mediated molecular events and biological processes could be an underlying mechanism for metastasis and SIRT1 is a therapeutic target for inhibiting metastasis, leading to good prognosis.

The Beneficial Roles of SIRT1 in Drug-Induced Liver Injury

Drug-induced liver injury (DILI) is a major cause of acute liver failure (ALF) as a result of accumulated drugs in the human body metabolized into toxic agents and helps generate heavy oxidative stress, inflammation, and apoptosis, which induces necrosis in hepatocytes and ultimately damages the liver. Sirtuin 1 (SIRT1) is said to have multiple vital roles in cell proliferation, aging, and antistress systems of the human body. The levels of SIRT1 and its activation precisely modulate its critical role in the interaction between multiple step procedures of DILI. The nuclear factor kappa-light-chain-enhancer of activated B cell- (NF-κB-) mediated inflammation signaling pathway, reactive oxygen species (ROS), DNA damage, mitochondrial membrane potential collapse, and endoplasmic reticulum (ER) stress also contribute to aggravate DILI. Apoptosis is regarded as the terminal reaction followed by multiple signaling cascades including caspases, p53, and mitochondrial dysfunction which have been said to contribute in DILI. The SIRT1 activator is regarded as a potential candidate for DILI, because the former could inhibit signaling of p53, NF-κB, and ER stress. On the other hand, overexpression of SIRT1 also enhances the activation of antioxidant responses via Kelch-like ECH-associated protein 1- (Keap1-) nuclear factor- (erythroid-derived 2-) like 2 (Nrf2) signaling. The current manuscript will highlight the mechanism of DILI and the interaction of SIRT1 with various cytoplasmic factors leading to DILI along with the summary of potent SIRT1 agonists.

ZEB2 stably represses RAB25 expression through epigenetic regulation by SIRT1 and DNMTs during epithelial-to-mesenchymal transition

Background

Epithelial mesenchymal transition (EMT) is tightly regulated by a network of transcription factors (EMT-TFs). Among them is the nuclear factor ZEB2, a member of the zinc-finger E-box binding homeobox family. ZEB2 nuclear localization has been identified in several cancer types, and its overexpression is correlated with the malignant progression. ZEB2 transcriptionally represses epithelial genes, such as E-cadherin (CDH1), by directly binding to the promoter of the genes it regulates and activating mesenchymal genes by a mechanism in which there is no full agreement. Recent studies showed that EMT-TFs interact with epigenetic regulatory enzymes that alter the epigenome, thereby providing another level of control. The role of epigenetic regulation on ZEB2 function is not well understood. In this study, we aimed to characterize the epigenetic effect of ZEB2 repressive function on the regulation of a small Rab GTPase RAB25.

Results

Using cellular models with conditional ZEB2 expression, we show a clear transcriptional repression of RAB25 and CDH1. RAB25 contributes to the partial suppression of ZEB2-mediated cell migration. Furthermore, a highly significant reverse correlation between RAB25 and ZEB2 expression in several human cancer types could be identified. Mechanistically, ZEB2 binds specifically to E-box sequences on the RAB25 promoter. ZEB2 binding is associated with the local increase in DNA methylation requiring DNA methyltransferases as well as histone deacetylation (H3K9Ac) depending on the activity of SIRT1. Surprisingly, SIRT1 and DNMTs did not interact directly with ZEB2, and while SIRT1 inhibition decreased the stability of long-term repression, it did not prevent down-regulation of RAB25 and CDH1 by ZEB2.

Conclusions

ZEB2 expression is resulting in drastic changes at the chromatin level with both clear DNA hypermethylation and histone modifications. Here, we revealed that SIRT1-mediated H3K9 deacetylation helps to maintain gene repression but is not required for the direct ZEB2 repressive function. Targeting epigenetic enzymes to prevent EMT is an appealing approach to limit cancer dissemination, but inhibiting SIRT1 activity alone might have limited effect and will require drug combination to efficiently prevent EMT.

Electronic supplementary material

The online version of this article (10.1186/s13072-018-0239-4) contains supplementary material, which is available to authorized users.

Sirtuin 1 and oral cancer

The sirtuins (SIRTs) are a family of highly conserved histone deacetylases (HDACs) consisting of seven members (SIRT1-SIRT7). Over the past few decades, SIRT1 has been the most extensively studied and garnered tremendous attention in the scientific community due to its emerging role in cancer biology. However, its biological role in the regulation of oral cancer is not yet fully understood. Owing to contradictory findings regarding the role of SIRT1 in oral cancer, debate about it continues. The present study discusses the biological roles and potential therapeutic implications of SIRT1 in precancerous oral lesions and oral cancer.

FK866 inhibits the epithelial-mesenchymal transition of hepatocarcinoma MHCC97-H cells

Epithelial-mesenchymal transition (EMT) is known to serve a pivotal function in hepatocellular carcinoma (HCC) metastasis. Nicotinamide phosphoribosyltransferase (NAMPT), the key enzyme in the nicotinamide-adenine dinucleotide (NAD⁺)-mediated pathway for the activation of silent information regulator 1 (SIRT1), serves a key function in HCC cell invasion and metastasis. Previous studies demonstrated that FK866, a targeted NAMPT inhibitor, inhibits the viability of HCC cells and induces cancer cell apoptosis; however, the effect of FK866 on the invasion and metastasis of HCC cells, particularly those associated with EMT through the SIRT1 pathway, remains unknown. In the present study, FK866 was identified to inhibit the capability of invasion and metastasis of cells from the HCC MHCC97-H line in a dose-dependent manner using a wound healing assay, an invasion assay and a migration assay. Furthermore, FK866 markedly decreased NAD+ and adenosine 5′-triphosphate content in MHCC97-H cells by inhibiting NAMPT expression. The results of the present study also revealed that FK866 led to a decrease in the expression of SIRT1, and to increased and decreased levels of the EMT marker proteins epithelial cadherin and vimentin, respectively, in MHCC97-H cells. Furthermore, FK866 inhibited the SIRT1-mediated EMT, invasion and migration of HCC cells by decreasing the expression of the NAMPT/NAD+ pathway. Taken together, the results of the present study suggest that FK866 may be an effective drug targeting HCC metastasis and invasion, and that the NAMPT/NAD+/SIRT1 pathway may be a potential therapeutic target for HCC.

The implications of signaling lipids in cancer metastasis

Metastasis is the most malignant stage of cancer. Lipid metabolic abnormalities are now increasingly recognized as characteristics of cancer cells. The accumulation of certain lipid species, such as signaling lipids, due to the avidity of lipid metabolism may be a causal factor of tumor malignant progression and metastatic behavior. In this review, we first describe signaling lipids implicated in cancer migration, invasion and metastasis. Next, we summarize the regulatory signaling hubs of lipid anabolic and catabolic metabolism. We then address lipid-rich circulating tumor cells (CTCs) and the lipid composition of exosomes budded off from tumor cells. We also present advances in targeting the regulatory hubs of lipid metabolism and signaling lipids in cancer therapy. Given the complexity of metabolic disorders in cancer, the development of significant portfolios of approaches to target signaling lipids by the integration of multiple chemical modulations, as well as molecular imaging modalities, should offer promising strategies for cancer therapy.

Lipid molecules with cellular signaling roles are increasingly recognized as playing a role in cancer metastasis, the dangerous spread of cancer cells beyond a primary tumor, and these lipids may offer new targets for anti-cancer treatments. Researchers in China led by Xiangjian Luo and Ya Cao at the Central South University in Changsha review the involvement of signaling lipids in cancer. The signaling lipids are a structurally diverse range of molecules that can regulate metabolic processes which become disrupted in cancer. They can act within cells and also when released from some cells to interact with others. Some of the lipids are released in tiny membrane-bound sacs called exosomes. Modifying the lipid content of exosomes, or purifying and then re-administering exosomes to deliver drugs, could offer promising options for developing novel treatments for cancer.

Anticancer activities of a benzimidazole compound through sirtuin inhibition in colorectal cancer

Aim: This study aims to investigate the mode of action of a novel sirtuin inhibitor (BZD9L1) and its associated molecular pathways in colorectal cancer (CRC) cells. Materials & methods: BZD9L1 was tested against metastatic CRC cell lines to evaluate cytotoxicity, cell cycle and apoptosis, senescence, apoptosis related genes and protein expressions, as well as effect against major cancer signaling pathways. Results & conclusion: BZD9L1 reduced the viability, cell migration and colony forming ability of both HCT 116 and HT-29 metastatic CRC cell lines through apoptosis. BZD9L1 regulated major cancer pathways differently in CRC with different mutation profiles. BZD9L1 exhibited anticancer activities as a cytotoxic drug in CRC and as a promising therapeutic strategy in CRC treatment.

Poly(adenosine diphosphate-ribose) polymerase as therapeutic target: lessons learned from its inhibitors

Poly(ADP-ribose) polymerases are a family of DNA-dependent nuclear enzymes catalyzing the transfer of ADP-ribose moieties from cellular nicotinamide-adenine-dinucleotide to a variety of target proteins. Although they have been considered as resident nuclear elements of the DNA repair machinery, recent works revealed a more intricate physiologic role of poly(ADP-ribose) polymerases with numerous extranuclear activities. Indeed, poly(ADP-ribose) polymerases participate in fundamental cellular processes like chromatin remodelling, transcription or regulation of the cell-cycle. These new insight into the physiologic roles of poly(ADP-ribose) polymerases widens the range of human pathologies in which pharmacologic inhibition of these enzymes might have a therapeutic potential. Here, we overview our current knowledge on extranuclear functions of poly(ADP-ribose) polymerases with a particular focus on the mitochondrial ones and discuss potential fields of future clinical applications.

The role of extracellular and intracellular Nicotinamide phosphoribosyl-transferase in cancer: Diagnostic and therapeutic perspectives and challenges

Nicotinamide phosphoribosyl-transferase (Nampt) or pre-B cell colony-enhancing factor or visfatin represents a pleiotropic molecule acting as an enzyme, a cytokine and a growth factor. Intracellular Nampt plays an important role in cellular bioenergetics and metabolism, particularly NAD biosynthesis. NAD biosynthesis is critical in DNA repair, oncogenic signal transduction, transcription, genomic integrity and apoptosis. Although its insulin-mimetic function remains a controversial issue, extracellular Nampt presents proliferative, anti-apoptotic, pro-inflammatory, pro-angiogenic and metastatic properties. Nampt is upregulated in many malignancies, including obesity-associated cancers, and is associated with worse prognosis. Serum Nampt may be a potential diagnostic and prognostic biomarker in cancer. Pharmacologic agents that neutralize Nampt or medications that decrease Nampt levels or downregulate signaling pathways downstream of Nampt may prove to be useful anti-cancer treatments. In particular, Nampt inhibitors as monotherapy or in combination therapy have displayed anti-cancer activity in vivo and in vitro. The aim of this review is to explore the role of Nampt in cancer pathophysiology as well as to synopsize the mechanisms underlying the association between extracellular and intracellular Nampt, and malignancy. Exploring the interplay of cellular bioenergetics, inflammation and adiposopathy is expected to be of importance in the development of preventive and therapeutic strategies against cancer.

Inhibition of sirtuins 1 and 2 impairs cell survival and migration and modulates the expression of P-glycoprotein and MRP3 in hepatocellular carcinoma cell lines

Sirtuins (SIRTs) 1 and 2 deacetylases are overexpressed in hepatocellular carcinoma (HCC) and are associated with tumoral progression and multidrug resistance (MDR). In this study we analyzed whether SIRTs 1 and 2 activities blockage was able to affect cellular survival and migration and to modulate p53 and FoxO1 acetylation in HepG2 and Huh7 cells. Moreover, we analyzed ABC transporters P-glycoprotein (P-gp) and multidrug resistance-associated protein 3 (MRP3) expression. We used cambinol and EX-527 as SIRTs inhibitors. Both drugs reduced cellular viability, number of colonies and cellular migration and augmented apoptosis. In 3D cultures, SIRTs inhibitors diminished spheroid growth and viability. 3D culture was less sensitive to drugs than 2D culture. The levels of acetylated p53 and FoxO1 increased after treatments. Drugs induced a decrease in ABC transporters mRNA and protein levels in HepG2 cells; however, only EX-527 was able to reduce MRP3 mRNA and protein levels in Huh7 cells. This is the first work demonstrating the regulation of MRP3 by SIRTs. In conclusion, both drugs decreased HCC cells survival and migration, suggesting SIRTs 1 and 2 activities blockage could be beneficial during HCC therapy. Downregulation of the expression of P-gp and MRP3 supports the potential application of SIRTs 1 and 2 inhibitions in combination with conventional chemotherapy.