SIRT3 regulates cellular iron metabolism and cancer growth by repressing iron regulatory protein 1

Sirtuin 3 Protects Lung Adenocarcinoma from Ferroptosis by Deacetylating and Stabilizing Mitochondrial Glutamate Transporter Solute Carrier Family 25 Member A22

Solute carrier family 25 member A22 (SLC25A22) is a glutamate transporter in the inner mitochondrial membrane that is known to suppress ferroptosis in pancreatic ductal adenocarcinoma (PDAC). Sirtuin 3 (SIRT3) is the main mitochondrial deacetylase, and we previously demonstrated that targeting SIRT3 sensitized glioblastoma to ferroptosis by promoting mitophagy and inhibiting SLC7A11. The purpose of this study was to analyze the effect of SIRT3-mediated deacetylation of mitochondrial SLC25A22 on RAS-selective lethal 3 (RSL3)-induced ferroptosis in lung adenocarcinoma (LUAD). We found that the expression of SLC25A22 and SIRT3 had a high positive correlation and that their expression was greater in LUAD tissues than in adjacent tissues. The RSL3-induced ferroptosis of LUAD led to upregulation of SLC25A22 and SIRT3, and SIRT3 protected RSL3-induced LUAD from ferroptosis in vitro and in vivo. At the molecular level, SIRT3 bound with SLC25A22 and deacetylated this protein. Targeting SIRT3 enhanced the acetylation of SLC25A22, decreased its ubiquitination, and promoted 26S proteasome degradation in LUAD cells. Therefore, our results demonstrated that SIRT3 protected LUAD cells from RSL3-induced ferroptosis, and this effect is at least partially due to its deacetylation of SLC25A22, revealing that the SIRT3-SLC25A22 axis has an important role in regulating the ferroptosis of LUAD cells.

Vitamin D supplementation alleviates high fat diet-induced metabolic associated fatty liver disease by inhibiting ferroptosis pathway

PURPOSE

Recently, a significant negative correlation has been found between vitamin D (VD) and metabolic associated fatty liver disease (MAFLD), suggesting a potential beneficial role of VD in preventing of MAFLD, while underscoring the importance of exploring its mechanisms.

METHODS

The experiment comprised two parts: male C57BL/6J mice (6 weeks) were fed a high-fat diet (HFD) and intraperitoneally injected with vitamin D3 (VD3) (1.68 IU/g/week) for 16 weeks. Meanwhile, palmitic acid (PA)-induced HepG2 cells were treated with 1,25(OH)2D3 (10 nM). The general conditions of the mice were evaluated by measuring body weight, liver/body weight, serum biochemical parameters, and inflammation indices. Additionally, injury-associated indices and histopathology were used to assess the severity of liver injury. Furthermore, indicators of ferroptosis, including lipid peroxidation, iron aggregation, and the aberrant expression of related proteins, were determined using Prussian blue staining, ELISA assay, and Western blot.

RESULTS

Long-term VD3 administration significantly reduced body weight gain and the liver/body weight ratio of HFD-induced MAFLD mice, while also improving serum lipid metabolism dysregulation and enhancing insulin sensitivity. The changes in the expressions of liver injury indices and histological manifestations due to VD3 treatment indicated that VD3 may exerts beneficial effects on liver injury through inhibiting inflammatory cell infiltration and vacuolation. Importantly, VD3 supplementation also inhibited ferroptosis by enhancing the body's antioxidant capacity, reducing local iron aggregation, and modulating the expression levels of ferroptosis-related proteins. These findings were further confirmed in a PA-induced HepG2 steatosis cell model, highlighting the pharmacological effects of VD.

CONCLUSIONS

VD shows promise in mitigating HFD -induced liver injury by improving metabolic dysregulation and inhibiting ferroptosis, suggesting therapeutic potential in MAFLD.

Sirtuins as Key Regulators in Pancreatic Cancer: Insights into Signaling Mechanisms and Therapeutic Implications

Pancreatic ductal adenocarcinoma (PDAC) stands as one of the most lethal cancers, marked by rapid progression, pronounced chemoresistance, and a complex network of genetic and epigenetic dysregulation. Within this challenging context, sirtuins, NAD+-dependent deacetylases, have emerged as pivotal modulators of key cellular processes that drive pancreatic cancer progression. Each sirtuin contributes uniquely to PDAC pathogenesis. SIRT1 influences apoptosis and chemoresistance through hypoxia, enhancing glycolytic metabolism and HIF-1α signaling, which sustain tumor survival against drugs like gemcitabine. SIRT2, conversely, disrupts cancer cell proliferation by inhibiting eIF5A, while SIRT3 exerts tumor-suppressive effects by regulating mitochondrial ROS and glycolysis. SIRT4 inhibits aerobic glycolysis, and its therapeutic upregulation has shown promise in curbing PDAC progression. Furthermore, SIRT5 modulates glutamine and glutathione metabolism, offering an avenue to disrupt PDAC's metabolic dependencies. SIRT6 and SIRT7, through their roles in angiogenesis, EMT, and metastasis, represent additional targets, with modulators of SIRT6, such as JYQ-42, showing potential to reduce tumor invasiveness. This review aims to provide a comprehensive exploration of the emerging roles of sirtuins, a family of NAD+-dependent enzymes, as critical regulators within the oncogenic landscape of pancreatic cancer. This review meticulously explores the nuanced involvement of sirtuins in pancreatic cancer, elucidating their contributions to tumorigenesis and suppression through mechanisms such as metabolic reprogramming, the maintenance of genomic integrity and epigenetic modulation. Furthermore, it emphasizes the urgent need for the development of targeted therapeutic interventions aimed at precisely modulating sirtuin activity, thereby enhancing therapeutic efficacy and optimizing patient outcomes in the context of pancreatic malignancies.

Alcohol- and Low-Iron Induced Changes in Antioxidant and Energy Metabolism Associated with Protein Lys Acetylation

Understanding the role of iron in ethanol-derived hepatic stress could help elucidate the efficacy of dietary or clinical interventions designed to minimize liver damage from chronic alcohol consumption. We hypothesized that normal levels of iron are involved in ethanol-derived liver damage and reduced dietary iron intake would lower the damage caused by ethanol. We used a pair-fed mouse model utilizing basal Lieber-DeCarli liquid diets for 22 weeks to test this hypothesis. In our mouse model, chronic ethanol exposure led to mild hepatic stress possibly characteristic of early-stage alcoholic liver disease, seen as increases in liver-to-body weight ratios. Dietary iron restriction caused a slight decrease in non-heme iron and ferritin (FeRL) expression while it increased transferrin receptor 1 (TfR1) expression without changing ferroportin 1 (FPN1) expression. It also elevated protein lysine acetylation to a more significant level than in ethanol-fed mice under normal dietary iron conditions. Interestingly, iron restriction led to an additional reduction in nicotinamide adenine dinucleotide (NAD+) and NADH levels. Consistent with this observation, the major mitochondrial NAD+-dependent deacetylase, NAD-dependent deacetylase sirtuin-3 (SIRT3), expression was significantly reduced causing increased protein lysine acetylation in ethanol-fed mice at normal and low-iron conditions. In addition, the detection of superoxide dismutase 1 and 2 levels (SOD1 and SOD2) and oxidative phosphorylation (OXPHOS) complex activities allowed us to evaluate the changes in antioxidant and energy metabolism regulated by ethanol consumption at normal and low-iron conditions. We observed that the ethanol-fed mice had mild liver damage associated with reduced energy and antioxidant metabolism. On the other hand, iron restriction may exacerbate certain activities of ethanol further, such as increased protein lysine acetylation and reduced antioxidant metabolism. This metabolic change may prove a barrier to the effectiveness of dietary reduction of iron intake as a preventative measure in chronic alcohol consumption.

Gene expression patterns of Sirtuin family members (SIRT1 TO SIRT7): Insights into pathogenesis and prognostic of Myelodysplastic neoplasm

To assess and validate the gene expression profile of SIRTs (SIRT1, SIRT2, SIRT3, SIRT4, SIRT5, SIRT6, and SIRT7) in relation to the pathogenesis and prognostic progression of Myelodysplastic neoplasm (MDS). Eighty bone marrow samples of patients with de novo MDS were diagnosed according to WHO 2022 and IPSS-R criteria. Ten bone marrow samples were obtained from elderly healthy volunteers and used as control samples. Gene expression levels of all SIRTs were assessed using RT-qPCR assays. Downregulation of SIRT2 (p = 0.009), SIRT3 (p = 0.048), SIRT4 (p = 0.049), SIRT5 (p = 0.046), SIRT6 (p = 0.043), and SIRT7 (p = 0.047) was identified in MDS patients compared to control individuals. Also, we identified that while SIRT2-7 genes are typically down-regulated in MDS patients compared to normal controls, there are relative expression variations among MDS patient subgroups. Specifically, SIRT4 (p = 0.029) showed increased expression in patients aged 60 or above, and both SIRT2 (p = 0.016) and SIRT3 (p = 0.036) were upregulated in patients with hemoglobin levels below 8 g/dL. SIRT2 (p = 0.045) and SIRT3 (p = 0.033) were highly expressed in patients with chromosomal abnormalities. Different SIRTs exhibited altered expression patterns concerning specific MDS clinical and prognostic characteristics. The downregulation in SIRTs genes (e.g., SIRT2 to SIRT7) expression in Brazilian MDS patients highlights their role in the disease's development. The upregulation of SIRT2 and SIRT3 in severe anemia patients suggests a potential link to manage iron overload-related complications in transfusion-dependent patients. Moreover, the association of SIRT2/SIRT3 with genomic instability and their role in MDS progression signify promising areas for future research and therapeutic targets. These findings underscore the importance of SIRT family in understanding and addressing MDS, offering novel clinical, prognostic, and therapeutic insights for patients with this condition.

Cell density impacts the susceptibility to ferroptosis by modulating IRP1-mediated iron homeostasis

Ferroptosis has been implicated in several neurological disorders and may be therapeutically targeted. However, the susceptibility to ferroptosis varies in different cells, and inconsistent results have been reported even using the same cell line. Understanding the effects of key variables of in vitro studies on ferroptosis susceptibility is of critical importance to facilitate drug discoveries targeting ferroptosis. Here, we showed that increased cell seeding density leads to enhanced resistance to ferroptosis by reducing intracellular iron levels. We further identified iron-responsive protein 1 (IRP1) as the key protein affected by cell density, which affects the expression of ferroportin or transferrin receptor and results in altered iron levels. Such observations were consistent across different cell lines, indicating that cell density should be tightly controlled in studies of ferroptosis. Since cell densities vary in different brain regions, these results may also shed light on selective regional vulnerability observed in neurological disorders.

The dual role of sirtuins in cancer: biological functions and implications

Sirtuins are pivotal in orchestrating numerous cellular pathways, critically influencing cell metabolism, DNA repair, aging processes, and oxidative stress. In recent years, the involvement of sirtuins in tumor biology has garnered substantial attention, with a growing body of evidence underscoring their regulatory roles in various aberrant cellular processes within tumor environments. This article delves into the sirtuin family and its biological functions, shedding light on their dual roles-either as promoters or inhibitors-in various cancers including oral, breast, hepatocellular, lung, and gastric cancers. It further explores potential anti-tumor agents targeting sirtuins, unraveling the complex interplay between sirtuins, miRNAs, and chemotherapeutic drugs. The dual roles of sirtuins in cancer biology reflect the complexity of targeting these enzymes but also highlight the immense therapeutic potential. These advancements hold significant promise for enhancing clinical outcomes, marking a pivotal step forward in the ongoing battle against cancer.

Iron, Copper, and Selenium: Cancer's Thing for Redox Bling

Cells require micronutrients for numerous basic functions. Among these, iron, copper, and selenium are particularly critical for redox metabolism, and their importance is heightened during oncogene-driven perturbations in cancer. In this review, which particularly focuses on iron, we describe how these micronutrients are carefully chaperoned about the body and made available to tissues, a process that is designed to limit the toxicity of free iron and copper or by-products of selenium metabolism. We delineate perturbations in iron metabolism and iron-dependent proteins that are observed in cancer, and describe the current approaches being used to target iron metabolism and iron-dependent processes.

Progress of Ferroptosis in Ischemic Stroke and Therapeutic Targets

Ferroptosis is an iron-dependent form of programmed cell death (PCD) and ischemic stroke (IS) has been confirmed to be closely related to ferroptosis. The mechanisms of ferroptosis were summarized into three interrelated aspects: iron metabolism, lipid peroxide metabolism, as well as glutathione and amino acid metabolism. What's more, the causal relationship between ferroptosis and IS has been elucidated by several processes. The disruption of the blood-brain barrier, the release of excitatory amino acids, and the inflammatory response after ischemic stroke all lead to the disorder of iron metabolism and the antioxidant system. Based on these statements, we reviewed the reported effects of compounds and drugs treating IS by modulating key molecules in ferroptosis. Through detailed analysis of the roles of these key molecules, we have also more clearly demonstrated the essential effect of ferroptosis in the occurrence of IS so as to provide new targets and ideas for the therapeutic targets of IS.

Targeting SIRT3 sensitizes glioblastoma to ferroptosis by promoting mitophagy and inhibiting SLC7A11

Glioblastoma (GBM) cells require large amounts of iron for tumor growth and progression, which makes these cells vulnerable to destruction via ferroptosis induction. Mitochondria are critical for iron metabolism and ferroptosis. Sirtuin-3 (SIRT3) is a deacetylase found in mitochondria that regulates mitochondrial quality and function. This study aimed to characterize SIRT3 expression and activity in GBM and investigate the potential therapeutic effects of targeting SIRT3 while also inducing ferroptosis in these cells. We first found that SIRT3 expression was higher in GBM tissues than in normal brain tissues and that SIRT3 protein expression was upregulated during RAS-selective lethal 3 (RSL3)-induced GBM cell ferroptosis. We then observed that inhibition of SIRT3 expression and activity in GBM cells sensitized GBM cells to RSL3-induced ferroptosis both in vitro and in vivo. Mechanistically, SIRT3 inhibition led to ferrous iron and ROS accumulation in the mitochondria, which triggered mitophagy. RNA-Sequencing analysis revealed that upon SIRT3 knockdown in GBM cells, the mitophagy pathway was upregulated and SLC7A11, a critical antagonist of ferroptosis via cellular import of cystine for glutathione (GSH) synthesis, was downregulated. Forced expression of SLC7A11 in GBM cells with SIRT3 knockdown restored cellular cystine uptake and consequently the cellular GSH level, thereby partially rescuing cell viability upon RSL3 treatment. Furthermore, in GBM cells, SIRT3 regulated SLC7A11 transcription through ATF4. Overall, our study results elucidated novel mechanisms underlying the ability of SIRT3 to protect GBM from ferroptosis and provided insight into a potential combinatorial approach of targeting SIRT3 and inducing ferroptosis for GBM treatment.

Research Progress on the Anticancer Activity of Plant Polysaccharides

Tumor is a serious threat to human health, with extremely high morbidity and mortality rates. However, tumor treatment is challenging, and the development of antitumor drugs has always been a significant research focus. Plant polysaccharides are known to possess various biological activities. They have many pharmacological properties such as immunomodulation, antitumor, antiviral, antioxidative, antithrombotic, and antiradiation effects, reduction of blood pressure and blood sugar levels, and protection from liver injury. Among these effects, the antitumor effect of plant polysaccharides has been widely studied. Plant polysaccharides can inhibit tumor proliferation and growth by inhibiting tumor cell invasion and metastasis, inducing cell apoptosis, affecting the cell cycle, and regulating the tumor microenvironment. They also have the characteristics of safety, high efficiency, and low toxicity, which can alleviate, to a certain extent, the adverse reactions caused by traditional tumor treatment methods such as surgery, radiotherapy, and chemotherapy. Therefore, this paper systematically summarizes the direct antitumor effects of plant polysaccharides, their regulatory effects on the tumor microenvironment, and intervening many common high-incidence tumors in other ways. It also provides data support for the administration of plant polysaccharides in modern tumor drug therapy, enabling the identification of new targets and development of new drugs for tumor therapy.

Mechanisms and regulations of ferroptosis

Regulation of cell mortality for disease treatment has been the focus of research. Ferroptosis is an iron-dependent regulated cell death whose mechanism has been extensively studied since its discovery. A large number of studies have shown that regulation of ferroptosis brings new strategies for the treatment of various benign and malignant diseases. Iron excess and lipid peroxidation are its primary metabolic features. Therefore, genes involved in iron metabolism and lipid metabolism can regulate iron overload and lipid peroxidation through direct or indirect pathways, thereby regulating ferroptosis. In addition, glutathione (GSH) is the body's primary non-enzymatic antioxidants and plays a pivotal role in the struggle against lipid peroxidation. GSH functions as an auxiliary substance for glutathione peroxidase 4 (GPX4) to convert toxic lipid peroxides to their corresponding alcohols. Here, we reviewed the researches on the mechanism of ferroptosis in recent years, and comprehensively analyzed the mechanism and regulatory process of ferroptosis from iron metabolism and lipid metabolism, and then described in detail the metabolism of GPX4 and the main non-enzymatic antioxidant GSH in vivo.

A Compared Study of Eicosapentaenoic Acid and Docosahexaenoic Acid in Improving Seizure-Induced Cognitive Deficiency in a Pentylenetetrazol-Kindling Young Mice Model

Epilepsy is a chronic neurological disorder that is more prevalent in children, and recurrent unprovoked seizures can lead to cognitive impairment. Numerous studies have reported the benefits of docosahexaenoic acid (DHA) on neurodevelopment and cognitive ability, while comparatively less attention has been given to eicosapentaenoic acid (EPA). Additionally, little is known about the effects and mechanisms of DHA and EPA in relation to seizure-induced cognitive impairment in the young rodent model. Current research indicates that ferroptosis is involved in epilepsy and cognitive deficiency in children. Further investigation is warranted to determine whether EPA or DHA can mitigate seizure-induced cognitive deficits by inhibiting ferroptosis. Therefore, this study was conducted to compare the effects of DHA and EPA on seizure-induced cognitive deficiency and reveal the underlying mechanisms focused on ferroptosis in a pentylenetetrazol (PTZ)-kindling young mice model. Mice were fed a diet containing DHA-enriched ethyl esters or EPA-enriched ethyl esters for 21 days at the age of 3 weeks and treated with PTZ (35 mg/kg, i.p.) every other day 10 times. The findings indicated that both EPA and DHA exhibited ameliorative effects on seizure-induced cognitive impairment, with EPA demonstrating a superior efficacy. Further mechanism study revealed that supplementation of DHA and EPA significantly increased cerebral DHA and EPA levels, balanced neurotransmitters, and inhibited ferroptosis by modulating iron homeostasis and reducing lipid peroxide accumulation in the hippocampus through activating the Nrf2/Sirt3 signal pathway. Notably, EPA exhibited better an advantage in ameliorating iron dyshomeostasis compared to DHA, owing to its stronger upregulation of Sirt3. These results indicate that DHA and EPA can efficaciously alleviate seizure-induced cognitive deficiency by inhibiting ferroptosis in PTZ-kindled young mice.

Sirtuin-3-Mediated Cellular Metabolism Links Cardiovascular Remodeling with Hypertension

Hypertension can cause structural and functional abnormalities in the cardiovascular system, which can be attributed to both hemodynamic and nonhemodynamic factors. These alterations are linked with metabolic changes and are induced by pathological stressors. Sirtuins are enzymes that act as stress sensors and regulate metabolic adaptation by deacetylating proteins. Among them, mitochondrial SIRT3 performs a crucial role in maintaining metabolic homeostasis. Evidence from experimental and clinical studies has shown that hypertension-induced decreases in SIRT3 activity can lead to cellular metabolism reprogramming and, subsequently, increased susceptibility to endothelial dysfunction, myocardial hypertrophy, myocardial fibrosis, and heart failure. This review presents recent research advances in SIRT3-mediated metabolic adaptation in hypertensive cardiovascular remodeling.

The roles of sirtuins in ferroptosis

Ferroptosis represents a novel non-apoptotic form of regulated cell death that is driven by iron-dependent lipid peroxidation and plays vital roles in various diseases including cardiovascular diseases, neurodegenerative disorders and cancers. Plenty of iron metabolism-related proteins, regulators of lipid peroxidation, and oxidative stress-related molecules are engaged in ferroptosis and can regulate this complex biological process. Sirtuins have broad functional significance and are targets of many drugs in the clinic. Recently, a growing number of studies have revealed that sirtuins can participate in the occurrence of ferroptosis by affecting many aspects such as redox balance, iron metabolism, and lipid metabolism. This article reviewed the studies on the roles of sirtuins in ferroptosis and the related molecular mechanisms, highlighting valuable targets for the prevention and treatment of ferroptosis-associated diseases.

ACO1 and IREB2 downregulation confer poor prognosis and correlate with autophagy-related ferroptosis and immune infiltration in KIRC

Background

ACO1 and IREB2 are two homologous cytosolic regulatory proteins, which sense iron levels and change iron metabolism–linked molecules. These two genes were noticeably decreased in kidney renal clear cell carcinoma (KIRC), which confer poor survival. Meanwhile, there is a paucity of information about the mechanisms and clinical significance of ACO1 and IREB2 downregulation in renal cancers.

Methods

The expression profiles of ACO1 and IREB2 were assessed using multiple public data sets via several bioinformatics platforms. Clinical and pathological information was utilized to stratify cohorts for comparison. Patient survival outcomes were evaluated using the Kaplan–Meier plotter, a meta-analysis tool. The correlations of ACO1 and IREB2 with ferroptosis were further evaluated in The Cancer Genome Atlas (TCGA)–KIRC database. Tumor immune infiltration was analyzed using the CIBERSORT, TIMER, and GEPIA data resources. ACO1 antagonist sodium oxalomalate (OMA) and IREB2 inhibitor sodium nitroprusside (SNP) was used to treat renal cancer ACHN cells together with sorafenib.

Results

KIRC patients with low ACO1 or IREB2 contents exhibited a remarkably worse survival rate in contrast with those with high expression in Kaplan–Meier survival analyses. Meanwhile, ACO1 and IREB2 regulate autophagy-linked ferroptosis along with immune cell invasion in the tumor microenvironment in KIRC patients. Blocking the activation of these two genes by their inhibitors OMA and SNP ameliorated sorafenib-triggered cell death, supporting that ACO1 and IREB2 could be participated in its cytotoxic influence on renal cancer cells.

Conclusion

ACO1 and IREB2 downregulation in renal cancers were correlated with cancer aggressiveness, cellular iron homeostasis, cytotoxic immune cell infiltration, and patient survival outcomes. Our research is integral to verify the possible significance of ACO1 and IREB2 contents as a powerful signature for targeted treatment or novel immunotherapy in clinical settings.

BACH1 Expression Is Promoted by Tank Binding Kinase 1 (TBK1) in Pancreatic Cancer Cells to Increase Iron and Reduce the Expression of E-Cadherin

BTB and CNC homology 1 (BACH1) represses the expression of genes involved in the metabolism of iron, heme and reactive oxygen species and promotes metastasis of various cancers including pancreatic ductal adenocarcinoma (PDAC). However, it is not clear how BACH1 is regulated in PDAC cells. Knockdown of Tank binding kinase 1 (TBK1) led to reductions of BACH1 mRNA and protein amounts in AsPC−1 human PDAC cells. Gene expression analysis of PDAC cells with knockdown of TBK1 or BACH1 suggested the involvement of TBK1 and BACH1 in the regulation of iron homeostasis. Ferritin mRNA and proteins were both increased upon BACH1 knockdown in AsPC−1 cells. Flow cytometry analysis showed that AsPC−1 cells with BACH1 knockout or knockdown contained lower labile iron than control cells, suggesting that BACH1 increased labile iron by repressing the expression of ferritin genes. We further found that the expression of E-cadherin was upregulated upon the chelation of intracellular iron content. These results suggest that the TBK1-BACH1 pathway promotes cancer cell metastasis by increasing labile iron within cells.

Mitochondrial sirtuin 3 and various cell death modalities

Sirtuin 3, a member of the mammalian sirtuin family of proteins, is involved in the regulation of multiple processes in cells. It is a major mitochondrial NAD⁺-dependent deacetylase with a broad range of functions, such as regulation of oxidative stress, reprogramming of tumor cell energy pathways, and metabolic homeostasis. One of the intriguing functions of sirtuin 3 is the regulation of mitochondrial outer membrane permeabilization, a key step in apoptosis initiation/progression. Moreover, sirtuin 3 is involved in the execution of various cell death modalities, which makes sirtuin 3 a possible regulator of crosstalk between them. This review is focused on the role of sirtuin 3 as a target for tumor cell elimination and how mitochondria and reactive oxygen species (ROS) are implicated in this process.

The Role and Therapeutic Perspectives of Sirtuin 3 in Cancer Metabolism Reprogramming, Metastasis, and Chemoresistance

Sirtuin 3 (SIRT3), the nicotinamide adenine dinucleotide (NAD⁺)-dependent deacetylase, acts as a metabolic modulator mainly located in mitochondria via regulating the process of the relevant biochemical processes by targeting crucial mediators. Recently, owing to its dual role in cancer, SIRT3 has attracted extensive attention. Cancer cells have different metabolic patterns from normal cells, and SIRT3-mediated metabolism reprogramming could be critical in the cancer context, which is closely related to the mechanism of metabolism reprogramming, metastasis, and chemoresistance in tumor cells. Therefore, it is crucial to elucidate the relevant pathological mechanisms and take appropriate countermeasures for the progression of clinical strategies to inhibit the development of cancer. In this review, existing available data on the regulation of cancer metabolism reprogramming, metastasis, and chemoresistance progression of SIRT3 are detailed, as well as the status quo of SIRT3 small molecule modulators is updated in the application of cancer therapy, aiming to highlight strategies directly targeting SIRT3-mediated tumor-suppressing and tumor-promoting, and provide new approaches for therapy application. Furthermore, we offer an effective evidence-based basis for the evolvement of potential personalized therapy management strategies for SIRT3 in cancer settings.

A comparative study of the effect of a gentle ketogenic diet containing medium-chain or long-chain triglycerides on chronic sleep deprivation-induced cognitive deficiency

The ketogenic diet (KD) is well known for its neuroprotective effect, but little is known about its prophylactic efficacy against chronic sleep deprivation (SD) induced cognitive deficiency. An emerging study indicated that ferroptosis plays an important role in neurologic diseases but has been rarely reported in chronic SD. Here, we investigated the prophylactic effects of a medium-chain triglyceride-enriched KD (MKD) and a long-chain triglyceride-enriched KD (LKD) on cognitive deficiency and revealed the underlying mechanism focused on ferroptosis in chronic SD model mice. The results showed that the MKD exhibited stronger effects than the LKD on improving cognitive deficiency via suppressing ferroptosis and improving synaptic plasticity. Further mechanism results indicated that MKD produced higher Sirt3 protein levels than LKD, which probably contributed to the synergistic effect of beta hydroxybutyric acid and decanoic acid. Our finds provide novel evidence for the KD as a safe and feasible dietary intervention to prevent chronic SD-induced cognitive deficiency, and suggest a better choice of medium-chain fatty acid-enriched KD.

A narrative review of mechanisms of ferroptosis in cancer: new challenges and opportunities

Objective

This article reviews the specific mechanism of ferroptosis in cancer and introduces in detail the opportunities and challenges of ferroptosis-based cancer therapy, aiming to provide a new research direction for tumor therapy.

Background

Ferroptosis is a newly discovered programmed non-apoptotic form of cell death. Involving changes in metabolic processes and the accumulation of peroxidation caused by factors such as drugs or genes which destruct the cell membrane structure, this kind of cell death has been linked with the pathological process of diseases such as tumors, neurological diseases, ischemia-reperfusion injury, kidney injury, and hemopathy. This kind of cell death can play a vital role in inhibiting tumorigenesis by eliminating the adaptive characteristics of malignant cells and removing cells that are unable to obtain key nutritional factors or are infected and damaged by environmental changes. The present focus of research on the regulation of ferroptosis-related diseases involves the use of small molecule compounds.

Methods

We described the mechanism of ferroptosis and its related small molecules compounds, which involved in the regulatory mechanism, and analyzed the role and regulatory mechanism of ferroptosis in different tumors.

Conclusions

This article reviewed the mechanism of ferroptosis and its role and mechanism in different tumors, and showed it can inhibit the occurrence and development of different tumors and may reduce the adverse effects of current treatment methods.

Targeting iron metabolism in cancer therapy

Iron is a critical component of many cellular functions including DNA replication and repair, and it is essential for cell vitality. As an essential element, iron is critical for maintaining human health. However, excess iron can be highly toxic, resulting in oxidative DNA damage. Many studies have observed significant associations between iron and cancer, and the association appears to be more than just coincidental. The chief characteristic of cancers, hyper-proliferation, makes them even more dependent on iron than normal cells. Cancer therapeutics are becoming as diverse as the disease itself. Targeting iron metabolism in cancer cells is an emerging, formidable field of therapeutics. It is a strategy that is highly diverse with regard to specific targets and the various ways to reach them. This review will discuss the importance of iron metabolism in cancer and highlight the ways in which it is being explored as the medicine of tomorrow.

Sirtuins as molecular targets, mediators, and protective agents in metal-induced toxicity

Metal dyshomeostasis, and especially overexposure, is known to cause adverse health effects due to modulation of a variety of metabolic pathways. An increasing body of literature has demonstrated that metal exposure may affect SIRT signaling, although the existing data are insufficient. Therefore, in this review we discuss the available data (PubMed-Medline, Google Scholar) on the influence of metal overload on sirtuin (SIRT) signaling and its association with other mechanisms involved in metal-induced toxicity. The existing data demonstrate that cadmium (Cd), mercury (Hg), arsenic (As), lead (Pb), aluminium (Al), hexavalent chromium (Cr^VI), manganese (Mn), iron (Fe), and copper (Cu) can inhibit SIRT1 activity. In addition, an inhibitory effect of Cd, Pb, As, and Fe on SIRT3 has been demonstrated. In turn, metal-induced inhibition of SIRT was shown to affect deacetylation of target proteins including FOXO, PGC1α, p53 and NF-kB. Increased acetylation downregulates PGC1α signaling pathway, resulting in cellular altered redox status and increased susceptibility to oxidative stress, as well as decreased mitochondrial biogenesis. Lower rates of LKB1 deacetylation may be responsible for metal-induced decreases in AMPK activity and subsequent metabolic disturbances. A shift to the acetylated FOXO results in increased expression of pro-apoptotic genes which upregulates apoptosis together with increased p53 signaling. Correspondingly, decreased NF-kB deacetylation results in upregulation of target genes of proinflammatory cytokines, enzymes, and cellular adhesion molecules thus promoting inflammation. Therefore, alterations in sirtuin activity may at least partially mediate metal-induced metabolic disturbances that have been implicated in neurotoxicity, nephrotoxicity, cardiotoxicity, and other toxic effects of heavy metals.

Genetic Manipulation of Sirtuin 3 Causes Alterations of Key Metabolic Regulators in Melanoma

The mitochondrial sirtuin SIRT3 plays key roles in cellular metabolism and energy production, which makes it an obvious target for the management of cancer, including melanoma. Previously, we have demonstrated that SIRT3 was constitutively upregulated in human melanoma and its inhibition resulted in anti-proliferative effects in vitro in human melanoma cells and in vivo in human melanoma xenografts. In this study, we expanded our data employing knockdown and overexpression strategies in cell culture and mouse xenografts to further validate and establish the pro-proliferative function of SIRT3 in melanocytic cells, and its associated potential mechanisms, especially focusing on the metabolic regulation. We found that short-hairpin RNA (shRNA) mediated SIRT3 knockdown in G361 melanoma cells showed diminished tumorigenesis in immunodeficient Nu/Nu mice. Conversely, SIRT3 overexpressing Hs294T melanoma cells showed increased tumor growth. These effects were consistent with changes in markers of proliferation (PCNA), survival (Survivin) and angiogenesis (VEGF) in xenografted tissues. Further, in in vitro culture system, we determined the effect of SIRT3 knockdown on glucose metabolism in SK-MEL-2 cells, using a PCR array. SIRT3 knockdown caused alterations in a total of 37 genes involved in the regulation and enzymatic pathways of glucose (32 genes) and glycogen (5 genes) metabolism. Functions annotation of these identified genes, using the ingenuity pathway analysis (IPA), predicted cumulative actions of decreased cell viability/proliferation, tumor growth and reactive oxygen species (ROS), and increased apoptosis in response to SIRT3 knockdown. Further, IPA gene network analysis of SIRT3 modulated genes revealed the interactions among these genes in addition to several melanoma-associated genes. Sirtuin pathway was identified as one of the top canonical pathways showing the interaction of SIRT3 with metabolic regulatory genes along with other sirtuins. IPA analysis also predicted the inhibition of HIF1α, PKM, KDM8, PPARGC1A, mTOR, and activation of P53 and CLPP; the genes involved in major cancer/melanoma-associated signaling events. Collectively, these results suggest that SIRT3 inhibition affects cellular metabolism, to impart an anti-proliferative response against melanoma.

Iron metabolism: an emerging therapeutic target underlying the anti-cancer effect of quercetin

Iron, an essential micronutrient for all kinds of cells, is essential for the balance of body internal environment. Notably, cancer cells exhibit a strong dependence on iron and require a large amount of iron for proliferation. A growing number of studies suggested that iron metabolism imbalance and subsequent excess iron accumulation are closely related to the occurrence and progression of cancer. Precisely, excess iron promotes the development of cancer due to the pro-oxidative nature of iron and its damaging effects on DNA. Simultaneously, tumor cells acquire large amounts of iron to maintain rapid growth and proliferation. Therefore, targeting iron metabolism may provide a new way for the treatment of cancer. Quercetin, a natural flavonoid, has long been regarded as potential drug for cancer treatments owing to its anti-inflammatory, antioxidant and anti-tumor effects. It is proven that quercetin possesses a high iron-chelating capacity, depriving cancer cells of iron or altering iron metabolism. Herein, we conduct a review on the mechanisms of iron imbalance in tumors and the role of quercetin in iron chelation, which will provide insight into the potential for quercetin as an anti-cancer drug.

Antibodies Targeting the Transferrin Receptor 1 (TfR1) as Direct Anti-cancer Agents

The transferrin receptor 1 (TfR1), also known as cluster of differentiation 71 (CD71), is a type II transmembrane glycoprotein that binds transferrin (Tf) and performs a critical role in cellular iron uptake through the interaction with iron-bound Tf. Iron is required for multiple cellular processes and is essential for DNA synthesis and, thus, cellular proliferation. Due to its central role in cancer cell pathology, malignant cells often overexpress TfR1 and this increased expression can be associated with poor prognosis in different types of cancer. The elevated levels of TfR1 expression on malignant cells, together with its extracellular accessibility, ability to internalize, and central role in cancer cell pathology make this receptor an attractive target for antibody-mediated therapy. The TfR1 can be targeted by antibodies for cancer therapy in two distinct ways: (1) indirectly through the use of antibodies conjugated to anti-cancer agents that are internalized by receptor-mediated endocytosis or (2) directly through the use of antibodies that disrupt the function of the receptor and/or induce Fc effector functions, such as antibody-dependent cell-mediated cytotoxicity (ADCC), antibody-dependent cell-mediated phagocytosis (ADCP), or complement-dependent cytotoxicity (CDC). Although TfR1 has been used extensively as a target for antibody-mediated cancer therapy over the years, interest continues to increase for both targeting the receptor for delivery purposes and for its use as direct anti-cancer agents. This review focuses on the developments in the use of antibodies targeting TfR1 as direct anti-tumor agents.

Chlorogenic acid depresses cellular bioenergetics to suppress pancreatic carcinoma through modulating c-Myc-TFR1 axis

Pancreatic ductal adenocarcinoma (PDAC) is severe malignant tumor in human, the outcomes of PDAC is extremely poor. Here, we evaluated the potential anti-tumor activity of chlorogenic Acid (CA) in PDAC. Here, we found CA was effective to suppress PDAC cell growth in vitro and in vivo. Importantly, we found overall oxygen consumption rate was significantly decreased in CA dose-dependent manner. We also found glycolysis reverse was decreased in CA-treated cells, while basal glycolysis and glycolytic capacity were not significantly changed. Mechanistically, we demonstrated TFR1 could be a novel downstream target of CA, which is essential for PDAC cell growth and cellular bioenergetics maintenance. Furthermore, we validated that CA-reduced c-Myc resulted to down-regulation of TFR1, which contributes to mitochondrial respiration dysfunction and cell growth delay. Together, this study indicates that CA suppresses PDAC cell growth through targeting c-Myc-TFR1 axis and suggests CA could be considered as a promising compound for PDAC treatment.

YTHDF1-enhanced iron metabolism depends on TFRC m6A methylation

Background: Among head and neck squamous cell carcinomas (HNSCCs), hypopharyngeal squamous cell carcinoma (HPSCC) has the worst prognosis. Iron metabolism, which plays a crucial role in tumor progression, is mainly regulated by alterations to genes and post-transcriptional processes. The recent discovery of the N6-methyladenosine (m⁶A) modification has expanded the realm of previously undiscovered post-transcriptional gene regulation mechanisms in eukaryotes. Many studies have demonstrated that m⁶A methylation represents a distinct layer of epigenetic deregulation in carcinogenesis and tumor proliferation. However, the status of m⁶A modification and iron metabolism in HPSCC remains unknown.

Methods: Bioinformatics analysis, sample analysis, and transcriptome sequencing were performed to evaluate the correlation between m⁶A modification and iron metabolism. Iron metabolic and cell biological analyses were conducted to evaluate the effect of the m⁶A reader YTHDF1 on HPSCC proliferation and iron metabolism. Transcriptome-wide m⁶A-seq and RIP-seq data were mapped to explore the molecular mechanism of YTHDF1 function in HPSCC.

Results: YTHDF1 was found to be closely associated with ferritin levels and intratumoral iron concentrations in HPSCC patients at Sir Run Run Shaw Hospital. YTHDF1 induced-HPSCC tumorigenesis depends on iron metabolism in vivo in vitro. Mechanistically, YTHDF1 methyltransferase domain interacts with the 3'UTR and 5'UTR of TRFC mRNA, then further positively regulates translation of m⁶A-modified TFRC mRNA. Gain-of-function and loss-of-function analyses validated the finding showing that TFRC is a crucial target gene for YTHDF1-mediated increases in iron metabolism.

Conclusion: YTHDF1 enhanced TFRC expression in HPSCC through an m⁶A-dependent mechanism. From a therapeutic perspective, targeting YTHDF1 and TFRC-mediated iron metabolism may be a promising strategy for HPSCC.

Inflammation Mediated Hepcidin-Ferroportin Pathway and Its Therapeutic Window in Breast Cancer

Experimental and clinical data strongly support that iron is an essential element which plays a big role in cancer biology. Thus, hepcidin (Hp) and ferroportin (Fpn) are molecules that regulate and maintain the metabolism of iron. A peptide hormone hepcidin limits recycled and stored iron fluxes in macrophage and hepatic hepatocyte, respectively, to the blood stream by promoting degradation of the only iron exporter, Fpn, in the target cells. Moreover, the inflammatory microenvironment of breast cancer and altered hepcidin/ferroportin pathway is intimately linked. Breast cancer exhibits an iron seeking phenotype that is accomplished by tumor-associated macrophage (TAM). Because macrophages contribute to breast cancer growth and progression, this review will discuss TAM with an emphasis on describing how TAM (M2Ф phenotypic) interacts with their surrounding microenvironment and results in dysregulated Hp/Fpn and pathologic accumulation of iron as a hallmark of its malignant condition. Moreover, the underlying stroma or tumor microenvironment releases significant inflammatory cytokines like IL-6 and bone morphogenetic proteins like BMP-2 and 6 leading in aberrant Hp/Fpn pathways in breast cancer. Inflammation is primarily associated with the high intracellular iron levels, deregulated hepcidin/ferroportin pathway, and its upstream signaling in breast cancer. Subsequently, scholars have been reported that reducing iron level and manipulating the signaling molecules involved in iron metabolism can be used as a promising strategy of tumor chemotherapy. Here, we review the key molecular aspects of iron metabolism and its regulatory mechanisms of the hepcidin/ferroportin pathways and its current therapeutic strategies in breast cancer.

Sirtuin 3 Inhibits Airway Epithelial Mitochondrial Oxidative Stress in Cigarette Smoke-Induced COPD

Mitochondrial damage in airway epithelial cells plays an important role in the pathogenesis of chronic obstructive pulmonary disease (COPD). Sirtuin 3 (Sirt3) is a mitochondrial deacetylase regulating mitochondrial function, but its role in the pathogenesis of COPD is still unknown. The aim of the present study was to investigate the effect of Sirt3 on airway epithelial mitochondria in cigarette smoke-induced COPD. Our present study has shown serious airway inflammation, alveolar space enlargement, and mitochondrial damage of the airway epithelium in COPD rats. Compared to the control rats, Sirt3 protein expression was significantly decreased in the airway epithelium and lung tissue homogenate from COPD rats. In airway epithelial cells (BEAS-2B), cigarette smoke extract (CSE) treatment significantly decreased mRNA and protein expression of Sirt3 and manganese superoxide dismutase (MnSOD), as well as MnSOD activity in a concentration and time-dependent manner. Sirt3 siRNA further significantly intensified the decreases in MnSOD expression and activity and aggravated mitochondrial oxidative stress and cell injury when airway epithelial cells were treated with 7.5% CSE. In contrast, Sirt3 overexpression significantly prevented the decrease of MnSOD expression and activity and improved mitochondrial oxidative stress and cell injury in CSE-treated airway epithelial cells. These data suggest that Sirt3 inhibits airway epithelial mitochondrial oxidative stress possibly through the regulation of MnSOD, thereby contributing to the pathogenesis of COPD.

Downregulation of TfR1 promotes progression of colorectal cancer via the JAK/STAT pathway

Background: Colorectal cancer (CRC) is one of the most prevalent gastrointestinal malignancies. The incidence of CRC has been rapidly increasing in China. Transferrin receptor 1 (TfR1) is a key regulator of cellular iron homeostasis. Several studies have demonstrated TfR1 overexpression in a variety of human tumors, but the association between TfR1 and CRC remains unclear.

Methods: TfR1 expression was evaluated in six CRC cell lines and tumor tissues. A total of 201 CRC patients were included for immunohistochemistry and 19 pairs of frozen tissues were used for real-time PCR. Cell proliferation, cell cycle, cell migration and invasion, and in vivo carcinogenesis were tested after downregulation of TfR1 by lentivirus. Protein microarray and Western blot analyses were used to explore the underlying mechanisms of TfR1 in CRC.

Results: TfR1 expression was higher in CRC tissues than in normal tissues (57.2% vs 22.9%, P＜0.001). TfR1 expression was obviously higher in CRC tissues with well differentiation (P＝0.008), no lymph node metastasis (P＝0.002), no distant metastasis (P＝0.006), no vascular invasion (P＜0.001) and early TNM stage (P＝0.013). CRC patients with TfR1-positive expression had a better survival than those with TfR1-negative expression (P＝0.044). Downregulation of TfR1 expression inhibited cell proliferation, promoted cells from G1 phase to S phase and facilitated cell migration and invasion. Knockdown of TfR1 also suppressed tumor growth in BALB/C-nu mice. Protein microarray and Western blot analyses showed that the Janus protein tyrosine kinase/signal transducer and activator of transcription pathway was activated along with downregulation of TfR1 expression.

Conclusion: Though TfR1 was overexpressed in colorectal cancer tissues, there was evidence that downregulation of TfR1 could promote cancer progression.

Elucidation and Structural Modeling of CD71 as a Molecular Target for Cell-Specific Aptamer Binding

Pancreatic cancer is a highly lethal malignancy associated with tissues of the pancreas. Early diagnosis and effective treatment are crucial to improving the survival rate of patients with pancreatic cancer. In a previous study, we employed the cell-SELEX strategy to obtain an ssDNA aptamer termed XQ-2d with high binding affinity for pancreatic cancer. Here, we first identify CD71 as the XQ-2d-binding target. We found that knockdown of CD71 abolished the binding of XQ-2d and that the binding affinity of XQ-2d is associated with membrane-bound CD71, rather than total CD71 levels. Competitive analysis revealed that XQ-2d shares the same binding site on CD71 with transferrin (Tf), but not anti-CD71 antibody. We then used a surface energy transfer (SET) nanoruler to measure the distance between the binding sites of XQ-2d and anti-CD71 antibody, and it was about 15 nm. Furthermore, we did molecular dynamics simulation to clarify that the spatial structure of XQ-2d and Tf competitively binding to CD71. We also engineered XQ-2d-mediated targeted therapy for pancreatic cancer, using an XQ-2d-based complex for loading doxorubicin (Dox). Because CD71 is overexpressed not only in pancreatic cancer but also in a variety of tumors, our work provides a systematic novel way of studying a potential biomarker and also promising tools for cancer diagnosis and therapy, opening new doors for effective cancer theranostics.

Iron and Cancer

This review explores the multifaceted role that iron has in cancer biology. Epidemiological studies have demonstrated an association between excess iron and increased cancer incidence and risk, while experimental studies have implicated iron in cancer initiation, tumor growth, and metastasis. The roles of iron in proliferation, metabolism, and metastasis underpin the association of iron with tumor growth and progression. Cancer cells exhibit an iron-seeking phenotype achieved through dysregulation of iron metabolic proteins. These changes are mediated, at least in part, by oncogenes and tumor suppressors. The dependence of cancer cells on iron has implications in a number of cell death pathways, including ferroptosis, an iron-dependent form of cell death. Uniquely, both iron excess and iron depletion can be utilized in anticancer therapies. Investigating the efficacy of these therapeutic approaches is an area of active research that promises substantial clinical impact.

Adjudin synergizes with paclitaxel and inhibits cell growth and metastasis by regulating the sirtuin 3-Forkhead box O3a axis in human small-cell lung cancer

Background

Small‐cell lung cancer (SCLC), a malignant tumor, is usually widely metastatic when diagnosed. The lack of important therapeutic clinical advances makes it difficult to treat. Previous studies showed that Adjudin had anticancer effects in many other human cancers, and it was synergetic with cisplatin in non‐small cell lung cancer. However, the mechanism on SCLC was unclear.

Methods

We investigated the potential mechanism and effect of Adjudin on SCLC both in vitro and in vivo.

Results

An SCLC xenograft model showed that Adjudin inhibited tumor growth and was significantly synergetic with paclitaxel (in vitro as well). Cell Counting Kit‐8 assays, flow cytometric analysis and western blotting showed that Adjudin effectively suppressed SCLC cell proliferation by inducing S phase arrest and caspase‐dependent apoptosis. Moreover, Transwell and scratch assays showed that Adjudin also effectively inhibited migration and invasion. Furthermore, Adjudin activated the sirtuin 3 (SIRT3)–Forkhead box O3a (FOXO3a) pathway. Downregulating SIRT3 or FOXO3a significantly attenuated Adjudin‐induced anticancer effects. Furthermore, higher expression of SIRT3 and FOXO3a were positively correlated, and both were associated with longer survival in lung cancer patients.

Conclusion

Overall, the present study is the first to show that Adjudin synergizes with paclitaxel and inhibits cell growth and metastasis by regulating the SIRT3–FOXO3a axis in SCLC; thus, Adjudin has great potential to be an anticancer agent.

Regulatory Effects of NAD+ Metabolic Pathways on Sirtuin Activity

NAD⁺ acts as a crucial regulator of cell physiology and as an integral participant in cellular metabolism. By virtue of a variety of signaling activities this central metabolite can exert profound effects on organism health status. Thus, while it serves as a well-known metabolic cofactor functioning as a redox-active substrate, it can also function as a substrate for signaling enzymes, such as sirtuins, poly (ADP-ribosyl) polymerases, mono (ADP-ribosyl) transferases, and CD38. Sirtuins function as NAD⁺-dependent protein deacetylases (deacylases) and catalyze the reaction of NAD⁺ with acyllysine groups to remove the acyl modification from substrate proteins. This deacetylation provides a regulatory function and integrates cellular NAD⁺ metabolism into a large spectrum of cellular processes and outcomes, such as cell metabolism, cell survival, cell cycle, apoptosis, DNA repair, mitochondrial homeostasis and mitochondrial biogenesis, and even lifespan. Increased attention to how regulated and pharmacologic changes in NAD⁺ concentrations can impact sirtuin activities has motivated openings of new areas of research, including investigations of how NAD⁺ levels are regulated at the subcellular level, and searches for more potent NAD⁺ precursors typified by nicotinamide riboside (NR) and nicotinamide mononucleotide (NMN). This review describes current results and thinking of how NAD⁺ metabolic pathways regulate sirtuin activities and how regulated NAD⁺ levels can impact cell physiology. In addition, NAD⁺ precursors are discussed, with attention to how these might be harnessed to generate novel therapeutic options to treat the diseases of aging.

Iron Metabolism in Cancer

Demanded as an essential trace element that supports cell growth and basic functions, iron can be harmful and cancerogenic though. By exchanging between its different oxidized forms, iron overload induces free radical formation, lipid peroxidation, DNA, and protein damages, leading to carcinogenesis or ferroptosis. Iron also plays profound roles in modulating tumor microenvironment and metastasis, maintaining genomic stability and controlling epigenetics. in order to meet the high requirement of iron, neoplastic cells have remodeled iron metabolism pathways, including acquisition, storage, and efflux, which makes manipulating iron homeostasis a considerable approach for cancer therapy. Several iron chelators and iron oxide nanoparticles (IONPs) has recently been developed for cancer intervention and presented considerable effects. This review summarizes some latest findings about iron metabolism function and regulation mechanism in cancer and the application of iron chelators and IONPs in cancer diagnosis and therapy.

The role of transferrin receptor in the Helicobacter pylori pathogenesis; L-ferritin as a novel marker for intestinal metaplasia

Helicobacter pylori growth requirements is a prerequisite to invade gastric epithelium and the process of injury to gastric cells will eventually lead to gastric cancer. The aim of this study is to investigate the effect of iron challenge on the expression of genes involved in iron homeostasis. The presence of Phosphoglucosamine mutase (glmM), cytotoxin-associated gene A (cagA) and vacuolating cytotoxin A (vacA) genes and mRNA expression of Iron Regulatory Protein 2 (IRP2), Transferrin Receptor (TFRC) and Ferritin Light Chain (FTL) genes in samples of 28 normal gastric mucosa, 33 chronic gastritis, 29 gastritis with intestinal metaplasia, 29 intestinal type adenocarcinoma patients were examined by real-time PCR. Immunohistochemistry was used to analyze cellular localization and protein levels. In the all H. pylori positive tissues, particularly in the basal regions of foveolar cells, TFRC was overexpressed (P < 0.05), and regardless of the H. pylori infection, FTL was overexpressed in all patient, exclusively in metaplastic glandular cells (P < 0.05). Furthermore, overexpression of IRP2 was associated with H. pylori positive chronic gastritis and intestinal metaplasia (P < 0.05). Our findings confirm the role of transferrin receptor in H. pylori attachment into the gastric mucosa to capture iron. Overexpression of FTL gene in metaplastic cells could be considered as a research background to investigate the role of this gene in the differentiation of gastric cells into intestinal metaplasia. In addition, this gene could be suggested as a diagnostic marker to be included among the other markers routinely performed by clinical diagnostic laboratories.

Ferritin: A potential serum marker for lymph node metastasis in head and neck squamous cell carcinoma

Head and neck squamous cell carcinoma (HNSCC) is the sixth most common cancer in the world, yet current treatment options are associated with limited success. The aim of the present study was to investigate the expression of ferritin in HNSCC and clarify whether it may serve as a biomarker for predicting HNSCC metastasis. The chemiluminescent immunoassay method was used to investigate the differences in the serum ferritin (SF) levels between patients with and without tumors, and between HNSCC with and without lymph node metastasis. The iron content and expression levels of ferritin were detected to verify the differences between tumor and normal tissues, and between HNSCC without and with lymph node metastasis. Data from the Gene Expression Omnibus (GEO) dataset was used to support the aforementioned results. No statistically significant difference in the SF level was observed between patients with and without tumors. Iron content and expression levels of ferritin heavy chain (FTH) and ferritin light chain (FTL) were higher in tumor tissues compared with normal tissues. The iron content and expression levels of SF, FTH and FTL were increased in HNSCC with metastasis compared with HNSCC without metastasis. The GEO dataset further verified the results and reported that the expression level of FTH was correlated with the prognosis of patients with HNSCC. Ferritin may not be a biomarker for the early diagnosis of HNSCC. However, an association exists between the expression level of ferritin and HNSCC cervical metastasis. SF may be a potential biomarker for predicting cervical lymph node metastasis in patients with HNSCC.

Inhibition of epithelial cell migration and Src/FAK signaling by SIRT3

Metastasis remains the leading cause of cancer mortality, and reactive oxygen species (ROS) signaling promotes the metastatic cascade. However, the molecular pathways that control ROS signaling relevant to metastasis are little studied. Here, we identify SIRT3, a mitochondrial deacetylase, as a regulator of cell migration via its control of ROS signaling. We find that, although mitochondria are present at the leading edge of migrating cells, SIRT3 expression is down-regulated during migration, resulting in elevated ROS levels. This SIRT3-mediated control of ROS represses Src oxidation and attenuates focal adhesion kinase (FAK) activation. SIRT3 overexpression inhibits migration and metastasis in breast cancer cells. Finally, in human breast cancers, SIRT3 expression is inversely correlated with metastatic outcome and Src/FAK signaling. Our results reveal a role for SIRT3 in cell migration, with important implications for breast cancer progression.

Alterations in Cellular Iron Metabolism Provide More Therapeutic Opportunities for Cancer

Iron is an essential element for the growth and proliferation of cells. Cellular iron uptake, storage, utilization and export are tightly regulated to maintain iron homeostasis. However, cellular iron metabolism pathways are disturbed in most cancer cells. To maintain rapid growth and proliferation, cancer cells acquire large amounts of iron by altering expression of iron metabolism- related proteins. In this paper, normal cellular iron metabolism and the alterations of iron metabolic pathways in cancer cells were summarized. Therapeutic strategies based on targeting the altered iron metabolism were also discussed and disrupting redox homeostasis by intracellular high levels of iron provides new insight for cancer therapy. Altered iron metabolism constitutes a promising therapeutic target for cancer therapy.

Brassica rapa hairy root extracts promote skin depigmentation by modulating melanin production and distribution

BACKGROUND

Skin whitening products, used for ages by Asian people for cultural and esthetic purposes, are very popular nowadays in Western countries as well, where the need to inhibit skin spots after sun exposure has become not only a cosmetic but also a health-related issue. Thus, the development of effective and safe depigmenting agents derived from natural products gets continuous attention by cosmetic brands and consumers.

OBJECTIVES

The aim of this study was to determine the effects of two preparations, obtained from the hairy root cultures of the species Brassica rapa, on melanogenesis and the expression of the extracellular matrix proteins involved in a correct pigment distribution.

METHODS

The two preparations, obtained by water-ethanol extraction and by digestion of cell-wall glycoproteins of the root cells, were chemically characterized and tested on skin cell cultures and on human skin explants to investigate on their dermatological activities.

RESULTS

Both the extracts were able to decrease melanin synthesis pathway in melanocytes and modulate the expression of genes involved in melanin distribution. One of the extracts was also effective in inducing the expression of laminin-5 and collagen IV, involved into the maintenance of tissue integrity. The two extracts, when tested together on human skin explants, demonstrated a good synergic hypopigmenting activity.

CONCLUSIONS

Taken together, the results indicate that the extracts from B. rapa root cultures can be employed as cosmetic active ingredients in skin whitening products and as potential therapeutic agents for treating pigmentation disorders.

The mitochondrion: a central architect of copper homeostasis

All known eukaryotes require copper for their development and survival. The essentiality of copper reflects its widespread use as a co-factor in conserved enzymes that catalyze biochemical reactions critical to energy production, free radical detoxification, collagen deposition, neurotransmitter biosynthesis and iron homeostasis. However, the prioritized use of copper poses an organism with a considerable challenge because, in its unbound form, copper can potentiate free radical production and displace iron-sulphur clusters to disrupt protein function. Protective mechanisms therefore evolved to mitigate this challenge and tightly regulate the acquisition, trafficking and storage of copper such that the metal ion is rarely found in its free form in the cell. Findings by a number of groups over the last ten years emphasize that this regulatory framework forms the foundation of a system that is capable of monitoring copper status and reprioritizing copper usage at both the cellular and systemic levels of organization. While the identification of relevant molecular mechanisms and signaling pathways has proven to be difficult and remains a barrier to our full understanding of the regulation of copper homeostasis, mounting evidence points to the mitochondrion as a pivotal hub in this regard in both healthy and diseased states. Here, we review our current understanding of copper handling pathways contained within the organelle and consider plausible mechanisms that may serve to functionally couple their activity to that of other cellular copper handling machinery to maintain copper homeostasis.

Low SIRT3 expression contributes to tumor progression, development and poor prognosis in human pancreatic carcinoma

SIRT3, an important mitochondrial protein, may act as either an oncogene or tumor suppressor depending on the tumor-type. The aim of this study was to investigate the expression of SIRT3 in pancreatic carcinoma (PC) and its clinical association in PC patients. Immunohistochemistry was adopted to investigate the expression of SIRT3 in cancer and corrresponding adjacent non-cancer tissues across 79 patients with PC. The log-rank test and Cox hazard model were used to estimate the relationship between SIRT3 expression and prognosis. The staining results revealed that SIRT3 negative expression was more common in cancer tissues than in adjacent non-cancer tissues (P<0.001). Chi-square tests indicated that the expression of SIRT3 correlated with T status (p<0.001) and tumor stage (p=0.013). Kaplan-Meier analysis showed that negative SIRT3 expression is linked to a poor prognosis in PC patients. Multivariate analysis identified SIRT3 expression as an independent predictor for PC outcome both in the whole cohort and several subgroups of PC patients. Our results indicate that down-regulated SIRT3 may contribute to tumor progression and gloomy prognosis in PC patients and may sever as a novel prognostic marker.

Cell-surface G-protein-coupled receptors for tumor-associated metabolites: A direct link to mitochondrial dysfunction in cancer

Mitochondria are the sites of pyruvate oxidation, citric acid cycle, oxidative phosphorylation, ketogenesis, and fatty acid oxidation. Attenuation of mitochondrial function is one of the most significant changes that occurs in tumor cells, directly linked to oncogenesis, angiogenesis, Warburg effect, and epigenetics. In particular, three mitochondrial enzymes are inactivated in cancer: pyruvate dehydrogenase (PDH), succinate dehydrogenase (SDH), and 3-hydroxy-3-methylglutaryl CoA synthase-2 (HMGCS2). These enzymes are subject to regulation via acetylation/deacetylation. SIRT3, the predominant mitochondrial deacetylase, directly targets these enzymes for deacetylation and maintains their optimal catalytic activity. SIRT3 is a tumor suppressor, and deacetylation of these enzymes contributes to its biological function. PDH catalyzes the oxidative decarboxylation of pyruvate into acetyl CoA, SDH oxidizes succinate into fumarate, and HMGCS2 controls the synthesis of the ketone body β-hydroxybutyrate. As the activities of these enzymes are decreased in cancer, tumor cells accumulate lactate and succinate but produce less amounts of β-hydroxybutyrate. Apart from their role in cellular energetics, these metabolites function as signaling molecules via specific cell-surface G-protein-coupled receptors. Lactate signals via GPR81, succinate via GPR91, and β-hydroxybutyrate via GPR109A. In addition, lactate activates hypoxia-inducible factor HIF1α and succinate promotes DNA methylation. GPR81 and GPR91 are tumor promoters, and increased production of lactate and succinate as their agonists drives tumorigenesis by enhancing signaling via these two receptors. In contrast, GPR109A is a tumor suppressor, and decreased synthesis of β-hydroxybutyrate as its agonist suppresses signaling via this receptor, thus attenuating the tumor-suppressing function of GPR109A. In parallel with the opposing changes in lactate/succinate and β-hydroxybutyrate levels, tumor cells upregulate GPR81 and GPR91 but downregulate GPR109A. As such, these three metabolite receptors play a critical role in cancer and represent a new class of drug targets with selective antagonists of GPR81 and GPR91 for cancer treatment and agonists of GPR109A for cancer prevention.

Potentially functional variants in lncRNAs are associated with breast cancer risk in a Chinese population

Long non-coding RNAs (lncRNAs) participate in the development of breast cancer. Genetic variants in lncRNAs may be involved in their abnormal expressions and associated with cancer risk. In the present study, we performed RNA sequencing on five paired breast cancer tumor and adjacent non-cancerous tissues to obtain differentially expressed lncRNAs. We systematically selected potential regulatory variants of these lncRNAs and investigated the associations between these variants and breast cancer susceptibility in 1486 breast cancer cases and 1519 cancer-free controls in a Chinese population. Eleven lncRNAs were significantly differentially expressed between breast cancer tumor and normal tissues (false discovery rate (FDR) ≤0.05 and fold-change ≥2), including two known lncRNAs HOTAIR and UCA1. We subsequently genotyped 20 variants located on these lncRNAs and identified two variants (rs11471161 in AC104135.3 and rs3751232 in RP11-1060J15.4) associated with breast cancer risk. Logistic regression analysis indicated that the variant allele of rs11471161 was significantly associated with a decreased breast cancer risk (additive model: OR = 0.84, 95%CI = 0.74-0.94, P = 0.004), while the variant allele of rs3751232 showed an increased risk of breast cancer (additive model: OR = 1.20, 95%CI = 1.02-1.40, P = 0.027). Further co-expression analysis indicated that AC104135.3 associated with ERBB2, which promotes the development and progression of breast cancer through overexpression. Together, these results suggest that genetic variants rs11471161 and rs3751232 in AC104135.3, and RP11-1060J15.4, respectively, may influence the susceptibility to breast cancer in the Chinese population. Further functional evaluations and larger studies are warranted to validate these findings.

Sirtuin 2 regulates cellular iron homeostasis via deacetylation of transcription factor NRF2

SIRT2 is a cytoplasmic sirtuin that plays a role in various cellular processes, including tumorigenesis, metabolism, and inflammation. Since these processes require iron, we hypothesized that SIRT2 directly regulates cellular iron homeostasis. Here, we have demonstrated that SIRT2 depletion results in a decrease in cellular iron levels both in vitro and in vivo. Mechanistically, we determined that SIRT2 maintains cellular iron levels by binding to and deacetylating nuclear factor erythroid-derived 2-related factor 2 (NRF2) on lysines 506 and 508, leading to a reduction in total and nuclear NRF2 levels. The reduction in nuclear NRF2 leads to reduced ferroportin 1 (FPN1) expression, which in turn results in decreased cellular iron export. Finally, we observed that Sirt2 deletion reduced cell viability in response to iron deficiency. Moreover, livers from Sirt2-/- mice had decreased iron levels, while this effect was reversed in Sirt2-/- Nrf2-/- double-KO mice. Taken together, our results uncover a link between sirtuin proteins and direct control over cellular iron homeostasis via regulation of NRF2 deacetylation and stability.

Tumor-initiating cells of breast and prostate origin show alterations in the expression of genes related to iron metabolism

The importance of iron in the growth and progression of tumors has been widely documented. In this report, we show that tumor-initiating cells (TICs), represented by spheres derived from the MCF7 cell line, exhibit higher intracellular labile iron pool, mitochondrial iron accumulation and are more susceptible to iron chelation. TICs also show activation of the IRP/IRE system, leading to higher iron uptake and decrease in iron storage, suggesting that level of properly assembled cytosolic iron-sulfur clusters (FeS) is reduced. This finding is confirmed by lower enzymatic activity of aconitase and FeS cluster biogenesis enzymes, as well as lower levels of reduced glutathione, implying reduced FeS clusters synthesis/utilization in TICs. Importantly, we have identified specific gene signature related to iron metabolism consisting of genes regulating iron uptake, mitochondrial FeS cluster biogenesis and hypoxic response (ABCB10, ACO1, CYBRD1, EPAS1, GLRX5, HEPH, HFE, IREB2, QSOX1 and TFRC). Principal component analysis based on this signature is able to distinguish TICs from cancer cells in vitro and also Leukemia-initiating cells (LICs) from non-LICs in the mouse model of acute promyelocytic leukemia (APL). Majority of the described changes were also recapitulated in an alternative model represented by MCF7 cells resistant to tamoxifen (TAMR) that exhibit features of TICs. Our findings point to the critical importance of redox balance and iron metabolism-related genes and proteins in the context of cancer and TICs that could be potentially used for cancer diagnostics or therapy.

Metabolic reprogramming and AMPKα1 pathway activation by caulerpin in colorectal cancer cells

Caulerpin, a secondary metabolite from the marine invasive green algae Caulerpa cylindracea is known to induce mitochondrial dysfunctions. In this study, the anticancer property of caulerpin was assessed in a panel of colorectal cancer cell lines. We demonstrated that caulerpin inhibited oxidative phosphorylation (OXPHOS) and facilitated an early intervention of the mitochondrial function, via inhibiting mitochondrial complex I, accompanied by the dissipation of mitochondrial membrane potential and a surge of reactive oxygen species (ROS) generation. Moreover, in response to the increment in AMP/ATP ratio, the energy sensor AMP-activated protein kinase (AMPK) was activated by caulerpin treatment in a calcium/calmodulin-dependent protein kinase 2 (CaMKK2)‑dependent manner. Distinguished effect on glycolysis was observed at different time-points after caulerpin treatment. Glycolysis was enhanced after a short time treatment with caulerpin, associated with upregulation of glucose transporter 1 (GLUT1), hexokinase II (HKII) and 6-phosphofructo-2-kinase (PFKFB3) protein expressions. However, long-term activation of AMPK by caulerpin damaged the glycolysis and glucose metabolism in colorectal cells, finally causing cell death. The persistent effect of caulerpin was mediated by AMPKα1, rather than AMPKα2, to abolish cell viability through hindering mTORC1-4E-BP1 axis. Moreover, caulerpin synergized with the glycolytic inhibitor 3BP in inhibiting cellular proliferation both in vitro and in vivo. Our findings on the previously uncharacterized anticancer effects of caulerpin may provide potential therapeutic approaches targeting the colorectal carcinoma metabolism.

Sirtuin 3: A Janus face in cancer (Review)

The NAD-dependent protein deacetylase sirtuin 3 (SIRT3) is an enzyme localized primarily in the mitochondrion, where it modulates cellular functions such as nutrient metabolism, ATP balance, antioxidant machinery, and other mechanisms fundamental to mitochondria. SIRT3 is closely associated with the pathogenesis of diverse disorders. In particular, it plays a dual role in the development and progression of cancer. In many cancers, SIRT3 acts as an oncogene by promoting or maintaining the malignant phenotypes of neoplastic cells, including uncontrolled proliferation, resistance to apoptosis, and increased motility or invasiveness; however, SIRT3 suppresses these phenotypes in certain types of malignancy. The underlying mechanisms involve depletion of intracellular reactive oxygen species, modulation of metabolic reprogramming, and regulation of intracellular signaling responsible for cell growth and death. This review summarizes recent findings concerning the characteristics and substrates/interacting partners of SIRT3, with particular emphasis on emerging mechanisms responsible for fine-tuning cellular behaviors that potentially underlie its conflicting roles in carcinogenesis.