SIRT3 aggravates metformin-induced energy stress and apoptosis in ovarian cancer cells

Exploring the Role of Mitochondrial Sirtuin 3 Gene in Gastric Cancer Risk Based on SNP Analysis and LORD-Q Assay

Mitochondrial sirtuin 3 (SIRT3) is a gene involved in key functions like acetylation, DNA repair, stress response, and tumorigenesis. Several studies have been published that showed the role of SIRT3 in various cancers. Still, few studies have been reported on the genetic and expression variation of the SIRT3 gene in gastric carcinogenesis. This study was designed to explore the involvement of the SIRT3 gene in gastric cancer. In this study, we used two study cohorts, cohort 1 contained 510 gastric cancer (GC) patients and an equal number of age and gender-matched controls. Cohort 2 included 220 GC tissue samples along with adjacent control tissues. Tetra Arms PCR was used to measure the frequency of three selected SNPs of the SIRT3 gene (rs28365927, rs11246029, and rs3817629) in cohort 1. Quantitative PCR and immunohistochemistry were performed to analyze the SIRT3 expression variation in cohort 2 GC patients. The superoxide dismutase (SOD), and 8-hydroxydeoxyguanosine (8-OHdG) levels were measured using ELISA, and DNA damage was measured using the LORD-Q assay. Statistical analysis showed the significant increased frequency of mutant allele of selected SNPs (rs28365927 (p < 0.0001); rs11246029 (p < 0.0001); and rs3817629 (p < 0.0001) in GC patients compared to controls. Expression analysis results showed significant downregulation of the SIRT3 gene at mRNA level (P < 0.001) and protein level (P < 0.001) in gastric tumor section vs control tissues. Multivariant Cox regression analysis showed that downregulated SIRT3 expression (p < 0.000001), H. pylori status (p < 0.0001), T-stage (p < 0.008), and N-stage (p < 0.001) act as prognostic markers in GC patients. ROC curve analysis showed the 90% and 100% specificity of the SIRT3 gene as a diagnostic marker in GC at the mRNA level and protein level, respectively. Significant increased oxidative stress (antioxidant enzyme level p < 0.0001; 8-OHdG level p < 0.0001) and lesion frequency/10 kb (p < 0.03) were indicated in the gastric tumor tissue sections vs controls. The result showed the tumor suppressor role of the SIRT3 gene in GC and was found linked with the surge in oxidative stress and damage in GC patients.

Metformin: From Diabetes to Cancer-Unveiling Molecular Mechanisms and Therapeutic Strategies

Metformin, a widely used anti-diabetic drug, has garnered attention for its potential in cancer management, particularly in breast and colorectal cancer. It is established that metformin reduces mitochondrial respiration, but its specific molecular targets within mitochondria vary. Proposed mechanisms include inhibiting mitochondrial respiratory chain Complex I and/or Complex IV, and mitochondrial glycerophosphate dehydrogenase, among others. These actions lead to cellular energy deficits, redox state changes, and several molecular changes that reduce hyperglycemia in type 2 diabetic patients. Clinical evidence supports metformin's role in cancer prevention in type 2 diabetes mellitus patients. Moreover, in these patients with breast and colorectal cancer, metformin consumption leads to an improvement in survival outcomes and prognosis. The synergistic effects of metformin with chemotherapy and immunotherapy highlights its potential as an adjunctive therapy for breast and colorectal cancer. However, nuanced findings underscore the need for further research and stratification by molecular subtype, particularly for breast cancer. This comprehensive review integrates metformin-related findings from epidemiological, clinical, and preclinical studies in breast and colorectal cancer. Here, we discuss current research addressed to define metformin's bioavailability and efficacy, exploring novel metformin-based compounds and drug delivery systems, including derivatives targeting mitochondria, combination therapies, and novel nanoformulations, showing enhanced anticancer effects.

Effect of metformin use on the risk and prognosis of ovarian cancer: an updated systematic review and meta-analysis

INTRODUCTION

Emerging evidence suggests that metformin has a potential antitumor effect both in vitro and in vivo. Increasing epidemiological studies indicate that diabetic patients receiving metformin therapy have lower incidences of cancer and have better survival rates. However, there are limited and inconsistent studies available about the effect of metformin therapy on ovarian cancer (OC). Thus, we conducted this meta-analysis to study the effect of metformin therapy on OC. Meanwhile, we systematically reviewed relevant studies to provide a framework for future research.

EVIDENCE ACQUISITION

We conducted a systematic literature search on PubMed, Web of Science, Springerlink, CNKI, VIP, SinoMed, and Wanfang up to the period of October 2018. A random-effects meta-analysis model was used to derive pooled effect estimates.

EVIDENCE SYNTHESIS

A total of 13 studies were retrieved of which 5 studies explained the prevention and 8 studies explained the treatment for OC. Our pooled results showed that metformin has a potential preventive effect on OC in diabetic women (pooled odds ratio [OR] 0.62, 95% confidence interval [95% CI] 0.34, 1.11; P<0.001). In addition, metformin can also significantly prolong progression-free survival (PFS) (pooled hazard ratio [HR] 0.49, 95% CI 0.34, 0.70; P=0.002), and overall survival (OS) (HR 0.71, 95%CI 0.61, 0.82; P<0.001) in patients with OC, regardless of whether they had diabetes.

CONCLUSIONS

The use of metformin can potentially reduce the risk of OC among diabetics, and it also can significantly improve PFS and OS in patients with OC. A further large clinical investigation would be needed to adopt our finding in practice, however, our systematic review provides an insight for future study designs.

Influence of Polyphenols on Adipose Tissue: Sirtuins as Pivotal Players in the Browning Process

Adipose tissue (AT) can be classified into two different types: (i) white adipose tissue (WAT), which represents the largest amount of total AT, and has the main function of storing fatty acids for energy needs and (ii) brown adipose tissue (BAT), rich in mitochondria and specialized in thermogenesis. Many exogenous stimuli, e.g., cold, exercise or pharmacological/nutraceutical tools, promote the phenotypic change of WAT to a beige phenotype (BeAT), with intermediate characteristics between BAT and WAT; this process is called "browning". The modulation of AT differentiation towards WAT or BAT, and the phenotypic switch to BeAT, seem to be crucial steps to limit weight gain. Polyphenols are emerging as compounds able to induce browning and thermogenesis processes, potentially via activation of sirtuins. SIRT1 (the most investigated sirtuin) activates a factor involved in mitochondrial biogenesis, peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α), which, through peroxisome proliferator-activated receptor γ (PPAR-γ) modulation, induces typical genes of BAT and inhibits genes of WAT during the transdifferentiation process in white adipocytes. This review article aims to summarize the current evidence, from pre-clinical studies to clinical trials, on the ability of polyphenols to promote the browning process, with a specific focus on the potential role of sirtuins in the pharmacological/nutraceutical effects of natural compounds.

Promising Strategy of mPTP Modulation in Cancer Therapy: An Emerging Progress and Future Insight

Cancer has been progressively a major global health concern. With this developing global concern, cancer determent is one of the most significant public health challenges of this era. To date, the scientific community undoubtedly highlights mitochondrial dysfunction as a hallmark of cancer cells. Permeabilization of the mitochondrial membranes has been implicated as the most considerable footprint in apoptosis-mediated cancer cell death. Under the condition of mitochondrial calcium overload, exclusively mediated by oxidative stress, an opening of a nonspecific channel with a well-defined diameter in mitochondrial membrane allows free exchange between the mitochondrial matrix and the extra mitochondrial cytosol of solutes and proteins up to 1.5 kDa. Such a channel/nonspecific pore is recognized as the mitochondrial permeability transition pore (mPTP). mPTP has been established for regulating apoptosis-mediated cancer cell death. It has been evident that mPTP is critically linked with the glycolytic enzyme hexokinase II to defend cellular death and reduce cytochrome c release. However, elevated mitochondrial Ca2+ loading, oxidative stress, and mitochondrial depolarization are critical factors leading to mPTP opening/activation. Although the exact mechanism underlying mPTP-mediated cell death remains elusive, mPTP-mediated apoptosis machinery has been considered as an important clamp and plays a critical role in the pathogenesis of several types of cancers. In this review, we focus on structure and regulation of the mPTP complex-mediated apoptosis mechanisms and follow with a comprehensive discussion addressing the development of novel mPTP-targeting drugs/molecules in cancer treatment.

Potential of histone deacetylase inhibitors for the therapy of ovarian cancer

Malignant ovarian tumors bear the highest mortality rate among all gynecological cancers. Both late tumor diagnosis and tolerance to available chemotherapy increase patient mortality. Accumulating evidence demonstrates that histone modifications play a key role in cancerization and progression. Histone deacetylases is associated with chromatin condensed structure and transcriptional repression and play a role in chromatin remodeling and epigenetics. Histone deacetylases are promising targets for therapeutic interventions intended to reverse aberrant epigenetic associated with cancer. Therefore, histone deacetylases inhibitors could be used as anti-cancer drugs. Preclinical studies have shown promising outcomes of histone deacetylases inhibitors in ovarian cancer while clinical trials have had mixed results and limited success as monotherapy. Therefore, combination therapy with different anticancer drugs for synergistic effects and newly selective histone deacetylases inhibitors development for lower toxicity are hot issues now. In this review, we summarize the latest studies on the classification and mechanisms of action of histone deacetylase and the clinical application of their inhibitors as monotherapy or combination therapy in ovarian cancer.

Sirtuins: Key players in obesity-associated adipose tissue remodeling

Obesity, a complex disease involving an excessive amount of body fat and a major threat to public health all over the world, is the determining factor of the onset and development of metabolic disorders, including type 2 diabetes, cardiovascular diseases, and non-alcoholic fatty liver disease. Long-term overnutrition results in excessive expansion and dysfunction of adipose tissue, inflammatory responses and over-accumulation of extracellular matrix in adipose tissue, and ectopic lipid deposit in other organs, termed adipose tissue remodeling. The mammalian Sirtuins (SIRT1-7) are a family of conserved NAD⁺-dependent protein deacetylases. Mounting evidence has disclosed that Sirtuins and their prominent substrates participate in a variety of physiological and pathological processes, including cell cycle regulation, mitochondrial biogenesis and function, glucose and lipid metabolism, insulin action, inflammatory responses, and energy homeostasis. In this review, we provided up-to-date and comprehensive knowledge about the roles of Sirtuins in adipose tissue remodeling, focusing on the fate of adipocytes, lipid mobilization, adipose tissue inflammation and fibrosis, and browning of adipose tissue, and we summarized the clinical trials of Sirtuin activators and inhibitors in treating metabolic diseases, which might shed light on new therapeutic strategies for obesity and its associated metabolic diseases.

[Metformin and malignant neoplasms: a possible mechanism of antitumor action and prospects for use in practice]

Metformin is a first-line antidiabetic drug for the treatment of type 2 diabetes mellitus (DM2); its molecular target is AMP-activated protein kinase (AMPK), which is involved in many metabolic processes. Metformin not only reduces blood glucose levels and improves insulin sensitivity, but also inhibits lipolysis and reduces cardiovascular risk in patients with DM2. In recent years, it has been proven that metformin slows down the aging process, stimulates hair growth, eliminates cognitive impairment, and also has an antitumor effect. Most basic studies have shown that metformin inhibits the growth of tumor cells and promotes cellular apoptosis, while clinical studies show contradictory results. This discrepancy can be explained by the difference in the concentration of metformin between basic and clinical studies. The maximum daily dose of metformin for patients with DM2 is 2500 mg / day, and the dose used in basic research was much higher. Metformin directly activates the AMPK signaling pathway, inhibits the production of reactive oxygen species, induces the activation of mTORC1, inhibits cyclin D1, which leads to a reduction in the risk of the occurrence and development of malignant neoplasms. In addition, metformin indirectly inhibits tumor growth, proliferation, invasion and metastasis by reducing the concentration of glucose in the blood, insulin resistance, as well as by reducing inflammation and affecting the tumor microenvironment. Glycolysis plays an important role in the energy metabolism of tumors, and metformin is able to have an inhibitory effect on it. Currently, studies of the mechanism of antitumor effects of metformin are becoming more extensive and in-depth, but there are still some contradictions.

Recent Advances in Ovarian Cancer: Therapeutic Strategies, Potential Biomarkers, and Technological Improvements

Aggressive and recurrent gynecological cancers are associated with worse prognosis and a lack of effective therapeutic response. Ovarian cancer (OC) patients are often diagnosed in advanced stages, when drug resistance, angiogenesis, relapse, and metastasis impact survival outcomes. Currently, surgical debulking, radiotherapy, and/or chemotherapy remain the mainstream treatment modalities; however, patients suffer unwanted side effects and drug resistance in the absence of targeted therapies. Hence, it is urgent to decipher the complex disease biology and identify potential biomarkers, which could greatly contribute to making an early diagnosis or predicting the response to specific therapies. This review aims to critically discuss the current therapeutic strategies for OC, novel drug-delivery systems, and potential biomarkers in the context of genetics and molecular research. It emphasizes how the understanding of disease biology is related to the advancement of technology, enabling the exploration of novel biomarkers that may be able to provide more accurate diagnosis and prognosis, which would effectively translate into targeted therapies, ultimately improving patients’ overall survival and quality of life.

Metformin and Glaucoma-Review of Anti-Fibrotic Processes and Bioenergetics

Glaucoma is the leading cause of irreversible blindness globally. With an aging population, disease incidence will rise with an enormous societal and economic burden. The treatment strategy revolves around targeting intraocular pressure, the principle modifiable risk factor, to slow progression of disease. However, there is a clear unmet clinical need to find a novel therapeutic approach that targets and halts the retinal ganglion cell (RGC) degeneration that occurs with fibrosis. RGCs are highly sensitive to metabolic fluctuations as a result of multiple stressors and thus their viability depends on healthy mitochondrial functioning. Metformin, known for its use in type 2 diabetes, has come to the forefront of medical research in multiple organ systems. Its use was recently associated with a 25% reduced risk of glaucoma in a large population study. Here, we discuss its application to glaucoma therapy, highlighting its effect on fibrotic signalling pathways, mitochondrial bioenergetics and NAD oxidation.

Metformin and Malignant Tumors: Not Over the Hill

Malignant tumors are a major cause of death, and their incidence is increasing worldwide. Although the survival rate for some cancers has improved, treatments for other malignant tumors are limited, and their mortality rate continues to increase. People with type 2 diabetes have a higher risk of malignant tumors and a higher mortality rate than those without diabetes. Metformin is a commonly used hypoglycemic drug. In recent years, a growing number of studies have indicated that metformin has antitumor effects and increases the sensitivity of malignant tumors to chemotherapy. However, the effect of metformin on different tumors is currently controversial, and the mechanism of metformin's antitumor action is not fully understood. Insights into the effect of metformin on malignant tumors and the possible mechanism may contribute to the development of antitumor drugs.

Ultrasound‑targeted microbubble destruction‑mediated overexpression of Sirtuin 3 inhibits the progression of ovarian cancer

Ultrasound-targeted microbubble destruction (UTMD) has recently been developed as a promising noninvasive tool for organ- and tissue-specific gene or drug delivery. The aim of the present study was to explore the role of UTMD-mediated Sirtuin 3 (SIRT3) overexpression in the malignant behaviors of human ovarian cancer (HOC) cells. Reverse transcription-quantitative PCR was performed to detect SIRT3 mRNA expression levels in normal human ovarian epithelial cells and HOC cell lines; low SIRT3 expression was found in HOC cell lines, and the SKOV3 cell line was used in the following experiments. The SIRT3-microbubble (MB) was prepared, and the effects of ultrasound-treated SIRT3-MB on biological processes of SKOV3 cells were determined. The proliferation, migration, invasion and apoptosis of SKOV3 cells were measured after SIRT3 upregulation by UTMD. Xenograft tumors in nude mice were induced to observe tumor growth in vivo. Upregulation of SIRT3 inhibited the malignant behaviors of SKOV3 cells, whereas UTMD-mediated SIRT3 upregulation further inhibited proliferation, epithelial-mesenchymal transition, invasion and migration, and induced apoptosis of SKOV3 cells, and it also inhibited tumor formation and growth in vivo. Moreover, the present study identified hypoxia inducible factor-1α (HIF-1α) as a target of SIRT3. The present study provided evidence that UTMD-mediated overexpression of SIRT3 may suppress HOC progression through the inhibition of HIF-1α.

Biochanin A Inhibits Glioblastoma Growth via Restricting Glycolysis and Mitochondrial Oxidative Phosphorylation

Abnormal metabolism serves a critical role in glioblastoma (GBM). Biochanin A (BCA), a flavonoid phenolic compound found in edible and herbal plants, has antioxidative and antitumor activities. However, it remains unclear whether BCA has an effect on energy metabolism. The aim of the present study was to evaluate the anticancer effects and molecular mechanism of the effect of BCA on energy metabolism. We observed that BCA inhibited the growth of U251 cells by the mitochondria-mediated intrinsic apoptotic pathway. BCA treatment reduced metabolic function, repressed mitochondrial membrane potential, and increased the production of reactive oxygen species (ROS) in GBM. In addition, we found that BCA decreased aerobic glycolysis by inactivation of the AKT/mTOR pathway. Taken together, the results demonstrate that treatment with BCA inhibited the proliferation of GBM by regulating metabolic reprogramming.

Energy metabolism disorders and potential therapeutic drugs in heart failure

Heart failure (HF) is a global public health problem with high morbidity and mortality. A large number of studies have shown that HF is caused by severe energy metabolism disorders, which result in an insufficient heart energy supply. This deficiency causes cardiac pump dysfunction and systemic energy metabolism failure, which determine the development of HF and recovery of heart. Current HF therapy acts by reducing heart rate and cardiac preload and afterload, treating the HF symptomatically or delaying development of the disease. Drugs aimed at cardiac energy metabolism have not yet been developed. In this review, we outline the main characteristics of cardiac energy metabolism in healthy hearts, changes in metabolism during HF, and related pathways and targets of energy metabolism. Finally, we discuss drugs that improve cardiac function via energy metabolism to provide new research ideas for the development and application of drugs for treating HF.

miR-224 aggravates cancer-associated fibroblast-induced progression of non-small cell lung cancer by modulating a positive loop of the SIRT3/AMPK/mTOR/HIF-1α axis

OBJECTIVES

Cancer-associated fibroblast (CAF) is among the most important tumor-host microenvironment components by affecting tumor progression. This study explored the role of miR-224 in CAF-induced non-small cell lung cancer (NSCLC).

MATERIALS AND METHODS

A CAF-NSCLC cell co-culture model was established, and the miR-224 expression in CAF was detected by reverse transcription-polymerase chain reaction (RT-PCR). Gain- and loss- of experiments of miR-224 were implemented to verify the effects of CAF on NSCLC cell proliferation, invasion, and epithelial-mesenchymal transition (EMT), and endothelial cell (EC) angiogenesis. Overexpressing genetic or pharmacological interventions were performed to explore the potential mechanisms of Sirtuins 3/AMP-activated protein kinase/mammalian target of rapamycin/hypoxia-inducible factor-1α (SIRT3/AMPK/mTOR/HIF-1α).

RESULTS

CAF enhanced the malignant phenotype of NSCLC cells and induced EC angiogenesis. miR-224 was significantly altered in CAFs. miR-224 up-regulation exacerbated NSCLC development mediated by CAFs, while miR-224 inhibition mostly reversed CAF-induced effects. Mechanistically, miR-224 targeted the 3'-untranslated regions (UTR) of SIRT3 mRNA, thereby inhibiting SIRT3/AMPK and activating mTOR/HIF-1α. Forced overexpression of SIRT3 up-regulated AMPK and inactivated mTOR/HIF-1α, while inhibiting HIF-1α markedly up-regulated SIRT3/AMPK and reduced mTOR phosphorylation. Interestingly, both Sirt1 overexpression and HIF-1α inhibition repressed miR-224 levels and miR-224-mediated promotive effects in NSCLC.

CONCLUSION

The miR-224-SIRT3/AMPK/mTOR/HIF-1α axis formed a positive feedback loop in modulating CAF-induced carcinogenic effects on NSCLC.

The Role of Metformin in Ovarian Cancer: Does Metformin Increase Survival in Ovarian Neoplasm?

The role of metformin in ovarian cancer (OC) remains a topic of research and open discussion. Because OC has a high mortality rate for various reasons, finding a solution is vital. Although metformin has demonstrated a high level of evidence in preventing and increasing survival in other cancers, its role in OC is still not proven. This review highlights the function of metformin as an antineoplastic agent in OC and its effect on overall survival, progress-free survival, and recurrence-free survival. We conducted a literature search in the PubMed database using the medical subject heading keywords, ovarian neoplasm and metformin. The search yielded 94 articles, of which 86 remained after including only English language articles. Finally, 50 articles published between 1997 and 2020 were reviewed. We recommend more randomized controlled trials in the future to determine the safety and efficacy of metformin in OC.

Cytotoxicity of metformin against HT29 colon cancer cells contributes to mitochondrial Sirt3 upregulation

Cancer and diabetes, the two mitochondria-related diseases, have recently been linked to silent mating-type information regulation 2 homolog 3 (SIRT3) activity irregularities. In this study, the effect of metformin, an antidiabetic with anticancer properties, has been evaluated on mitochondrial functionality markers, cell death pathways, and SIRT3 enzyme activity in the colon cancer cell line, HT-29, and human embryonic kidney cells (HEK 293). HT-29 cells were treated with metformin (5, 10, 20, 40, and 80 µM) for 24, 48, and 72 h for measuring the IC₅₀ concentration. Reactive oxygen species (ROS) production, apoptosis, mitochondrial membrane potential, SIRT3 activity, and expression were evaluated against the colon cancer cell line, HT-29. Results indicated a higher ROS production at 6 than 12 h with metformin treatment. Metformin modified the mitochondrial membrane potential, resulting in cell death induction. Results from SIRT3 activity and expression showed that metformin increased its activity and expression in cancer cells. In conclusion, metformin in HT-29 cells disturbed the mitochondrial activity via increased ROS levels and SIRT3 activity, and these rapid modifications may play a key role in its cytotoxic property.

Potential relationship between Sirt3 and autophagy in ovarian cancer

Sirtuin 3 (Sirt3) is an important member of the sirtuin protein family. It is a deacetylase that was previously reported to modulate the level of reactive oxygen species (ROS) production and limit the extent of oxidative damage in cellular components. As an important member of the class III type of histone deacetylases, Sirt3 has also been documented to mediate nuclear gene expression, metabolic control, neuroprotection, cell cycle and proliferation. In ovarian cancer (OC), Sirt3 has been reported to regulate cellular metabolism, apoptosis and autophagy. Sirt3 can regulate autophagy through a variety of different molecular signaling pathways, including the p62, 5'AMP-activated protein kinase and mitochondrial ROS-superoxide dismutase pathways. However, autophagy downstream of Sirt3 and its association with OC remains poorly understood. In the present review, the known characteristics of Sirt3 and autophagy were outlined, and their potential functional roles were discussed. Following a comprehensive analysis of the current literature, Sirt3 and autophagy may either serve positive or negative roles in the regulation of OC. Therefore, it is important to identify the appropriate expression level of Sirt3 to control the activation of autophagy in OC cells. This strategy may prove to be a novel therapeutic method to reduce the mortality of patients with OC. Finally, potential research directions into the association between Sirt3 and other signaling pathways were provided.

Hypoxia-induced NAD+ interventions promote tumor survival and metastasis by regulating mitochondrial dynamics

Hypoxia, an important feature of the tumor microenvironment, is responsible for the chemo-resistance and metastasis of malignant solid tumors. Recent studies indicated that mitochondria undergo morphological transitions as an adaptive response to maintain self-stability and connectivity under hypoxic conditions. NAD⁺ may not only provide reducing equivalents for biosynthetic reactions and in determining energy production, but also functions as a signaling molecule in mitochondrial dynamics regulation. In this review, we describe the upregulated KDAC deacetylase expression in the mitochondria and cytoplasm of tumor cells that results from sensing the changes in NAD⁺ to control mitochondrial dynamics and distribution, which is responsible for survival and metastasis in hypoxia.

Gene expression and prognosis of sirtuin family members in ovarian cancer

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

p53/PGC‑1α‑mediated mitochondrial dysfunction promotes PC3 prostate cancer cell apoptosis

Data for p53 mutation in prostate cancer in The Cancer Genome Atlas database revealed that >85% of p53 mutations occurred in the p53 DNA binding domain. These mutations not only severely damage the function of the p53 protein, but also reduce the disease-free survival of patients. Peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α) is involved in the regulation of mitochondrial function and is highly expressed in prostate cancer PC3 and DU145 cells with p53 deletion or mutation. However, whether p53 negatively regulates PGC-1α in prostate cancer cells remains to be elucidated. In the present study, p53 overexpression was induced in prostate cancer PC3 cells. Subsequently, the expression levels of PGC-1α and alterations to mitochondrial function were assessed. Moreover, PGC-1α was activated in prostate cancer PC3 cells using ZLN005 to investigate alterations to mitochondrial function and cell apoptosis. The present study revealed that p53 decreased the expression and nuclear localization of the PGC-1α protein and induced mitochondrial dysfunction. Activation of PGC-1α partially reversed p53-mediated mitochondrial dysfunction. Inhibition of the p53/PGC-1α pathway on mitochondrial biogenesis and fission-/fusion-associated gene and protein expression were associated with mitochondrial dysfunction. p53/PGC-1α-mediated mitochondrial dysfunction promoted apoptosis of PC3 prostate cancer cells. The results indicated that PGC-1α is an essential target of p53-induced apoptosis in prostate cancer cells and indicated that targeting PGC-1α may provide a new therapeutic strategy for prostate cancer.

Metformin activates AMPK/SIRT1/NF-κB pathway and induces mitochondrial dysfunction to drive caspase3/GSDME-mediated cancer cell pyroptosis

Pyroptosis is a form of programmed cell death initiated by inflammasomes and is critical for immunity. SIRT1, a NAD+-dependent deacetylase, plays multiple roles in inflammatory response and immunity. Metformin can activate SIRT1 to participate in different biological processes and exert its anticancer effects. However, the mechanism by which metformin activates SIRT1 to drive cancer cell pyroptosis has not been reported. In this study, we treated cancer cells with metformin for diverse periods of time (0-24 h) and found that cell viability was decreased obviously. Interestingly, pyroptosis occurred when cancer cells were treated with metformin for the indicated time (4, 8 and 12 h), which was elucidated by the cell swelling and bubbles blowing in the membrane. Metformin also increased the release of lactate dehydrogenase (LDH, an indication of pyroptotic cell cytotoxicity) remarkably. The underlying mechanisms were that metformin enhanced AMPK/SIRT1 pathway and further increased NF-κB p65 expression to stimulate Bax activation and cytochrome c release, triggering caspase3 cleavage of GSDME, which is a characteristic pyroptotic marker. Depletion of SIRT1 inhibited metformin-induced these protein expression, revealing that metformin promotes AMPK/SIRT1/NF-κB signaling to drive cancer cell pyroptosis. Meantime, metformin induced mitochondrial dysfunction to trigger activation of caspase3 and generation of GSDME-N. Moreover, mitochondrial dysfunction activated AMPK/SIRT1 pathway to cause pyroptotic death upon metformin treatment. This research firstly reveals that metformin as a sensitizer amplifies AMPK/SIRT1/NF-κB signaling to induce caspase3/GSDME-mediated cancer cell pyroptosis. Induction of cellular pyroptosis by metformin is considered as a novel therapeutic option against various cancers.

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

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

Targeting epigenetic regulators for cancer therapy: mechanisms and advances in clinical trials

Epigenetic alternations concern heritable yet reversible changes in histone or DNA modifications that regulate gene activity beyond the underlying sequence. Epigenetic dysregulation is often linked to human disease, notably cancer. With the development of various drugs targeting epigenetic regulators, epigenetic-targeted therapy has been applied in the treatment of hematological malignancies and has exhibited viable therapeutic potential for solid tumors in preclinical and clinical trials. In this review, we summarize the aberrant functions of enzymes in DNA methylation, histone acetylation and histone methylation during tumor progression and highlight the development of inhibitors of or drugs targeted at epigenetic enzymes.

The sirtuin family in cancer

Sirtuins are a family of protein deacylases and ADP-ribosyl-transferases, homologs to the yeast SIR2 protein. Seven sirtuin paralogs have been described in mammals, with different subcellular locations, targets, enzymatic activities, and regulatory mechanisms. All sirtuins share NAD+ as substrate, placing them as central metabolic hubs with strong relevance in lifespan, metabolism, and cancer development. Much effort has been devoted to studying the roles of sirtuins in cancer, providing a wealth of data on sirtuins roles in mouse models and humans. Also, extensive data are available on the effects of pharmacological modulation of sirtuins in cancer development. Here, we present a comprehensive and organized resume of all the existing evidence linking every sirtuin with cancer development. From our analysis, we conclude that sirtuin modulation after tumor initiation results in unpredictable outcomes in most tumor types. On the contrary, all genetic and pharmacological models indicate that sirtuins activation prior to tumor initiation can constitute a powerful preventive strategy.

Development and validation of SIRT3-related nomogram predictive of overall survival in patients with serous ovarian cancer

Objective

Our aim is to analyzed the expression pattern of sirtuin(SIRT) superfamily and evaluated their prognostic values in serous ovarian cancer patients.

Methods

We first analyzed the differential expression of SIRT members among fallopian tube epithelium (FTE), primary serous ovarian cancers/tubal cancers (PSOCs/PSTCs), and omental metastases using GSE10971 and GSE30587 datasets. The prognostic values of SIRT members were evaluated using TCGA and GSE9891 dataset.

Results

SIRT3 and SIRT5 expression were significantly decreased and increased in PSOCs/PSTCs compared with that in normal counterparts, respectively. SIRT6 and SIRT7 were overexpressed in ometal metastases compared with corresponding primary counterparts. With respect to recurrence free survival, however, SIRT7 overexpression was correlated with better prognosis. A similar trend was observed by multivariable analysis. Regarding overall survival (OS), increased expression of SIRT3, SIRT5, and SIRT7 were associated with better survival by univariable analysis. Subsequent multivariable analysis showed that SIRT3 remained an independent favorable prognostic factor for OS. The SIRT3-related nomogram illustrated age at initial diagnosis as sharing the largest contribution to OS, followed by SIRT3 expression and FIGO stage. The C-index for OS prediction was 0.65 (95%CI, 0.61–0.69) in training cohort (TCGA dataset) and 0.65 (95%CI, 0.59–0.71) in validation cohort (GSE9891 dataset), respectively. The calibration plots showed optimal agreement between the prediction by SIRT3-related nomogram and actual observation for 1-, 3-, and 5-year OS probability.

Conclusion

In conclusion, SIRT3 was an independent favorable prognostic factor for OS in serous ovarian cancer, and added prognostic value to the traditional clinicopathological factors used to evaluate patients’ prognosis.

Metformin triggers the intrinsic apoptotic response in human AGS gastric adenocarcinoma cells by activating AMPK and suppressing mTOR/AKT signaling

Metformin is commonly used to treat patients with type 2 diabetes and is associated with a decreased risk of cancer. Previous studies have demonstrated that metformin can act alone or in synergy with certain anticancer agents to achieve anti-neoplastic effects on various types of tumors via adenosine monophosphate-activated protein kinase (AMPK) signaling. However, the role of metformin in AMPK-mediated apoptosis of human gastric cancer cells is poorly understood. In the current study, metformin exhibited a potent anti-proliferative effect and induced apoptotic characteristics in human AGS gastric adenocarcinoma cells, as demonstrated by MTT assay, morphological observation method, terminal deoxynucleotidyl transferase dUTP nick end labeling and caspase-3/7 assay kits. Western blot analysis demonstrated that treatment with metformin increased the phosphorylation of AMPK, and decreased the phosphorylation of AKT, mTOR and p70S6k. Compound C (an AMPK inhibitor) suppressed AMPK phosphorylation and significantly abrogated the effects of metformin on AGS cell viability. Metformin also reduced the phosphorylation of mitogen-activated protein kinases (ERK, JNK and p38). Additionally, metformin significantly increased the cellular ROS level and included loss of mitochondrial membrane potential (ΔΨm). Metformin altered apoptosis-associated signaling to downregulate the BAD phosphorylation and Bcl-2, pro-caspase-9, pro-caspase-3 and pro-caspase-7 expression, and to upregulate BAD, cytochrome c, and Apaf-1 proteins levels in AGS cells. Furthermore, z-VAD-fmk (a pan-caspase inhibitor) was used to assess mitochondria-mediated caspase-dependent apoptosis in metformin-treated AGS cells. The findings demonstrated that metformin induced AMPK-mediated apoptosis, making it appealing for development as a novel anticancer drug for the treating gastric cancer.

The antineoplastic drug metformin downregulates YAP by interfering with IRF-1 binding to the YAP promoter in NSCLC

Background

Activation of the oncogene YAP has been shown to be related to lung cancer progression and associates with poor prognosis and metastasis. Metformin is a drug commonly used in the treatment of diabetes and with anticancer activity. However, the mechanism through which metformin inhibits tumorigenesis via YAP is poorly understood.

Methods

The mRNA and protein expressions were analyzed by RT-PCR and western blot. The cellular proliferation was detected by CCK8 and MTT. The cell migration and invasion growth were analyzed by wound healing assay and transwell assay. The activities of promoter were analyzed by luciferase reporter assay. Chromatin immunoprecipitation detected the combining ability of IRF-1 and 5′UTR-YAP.

Findings

Our immunohistochemistry staining and RT-PCR assays showed that the expression of YAP was higher in lung carcinoma samples. Interestingly, metformin was able to downregulate YAP mRNA and protein expression in lung cancer cells. Mechanistically, we found that metformin depressed YAP promoter by competing with the binding of the transcription factor IRF-1 in lung cancer cells. Moreover, combination of metformin and verteporfin synergistically inhibits cell proliferation, promotes apoptosis and suppresses cell migration/invasion by downregulating YAP, therefore reduces the side effects caused by their single use and improve the quality of life for patients with lung cancer.

Interpretation

we concluded that metformin depresses YAP promoter by interfering with the binding of the transcription factor IRF-1. Importantly, verteporfin sensitizes metformin-induced the depression of YAP and inhibition of cell growth and invasion in lung cancer cells.

Fund

This work was supported by National Natural Science Foundation of China (No.31801085), the Science and Technology Development Foundation of Yantai (2015ZH082), Natural Science Foundation of Shandong Province (ZR2018QH004, ZR2016HB55, ZR2017PH067 and ZR2017MH125), and Research Foundation of Binzhou Medical University (BY2015KYQD29 and BY2015KJ14).

Pleiotropic Effects of Metformin on Cancer

Metformin (MTF) is a natural compound derived from the legume Galega officinalis. It is the first line antidiabetic drug for type 2 diabetes (T2D) treatment. One of its main antidiabetic effects results from the reduction of hepatic glucose release. First scientific evidence for the anticancer effects of MTF was found in animal research, published in 2001, and some years later a retrospective observational study provided evidence that linked MTF to reduced cancer risk in T2D patients. Its pleiotropic anticancer effects were studied in numerous in vitro and in vivo studies at the molecular and cellular level. Although the majority of these studies demonstrated that MTF is associated with certain anticancer properties, clinical studies and trials provided a mixed view on its beneficial anticancer effects. This review emphasizes the pleiotropic effects of MTF and recent progress made in MTF applications in basic, preclinical, and clinical cancer research.

Sirt3 inhibits cerebral ischemia-reperfusion injury through normalizing Wnt/β-catenin pathway and blocking mitochondrial fission

Cerebral ischemia-reperfusion injury (IRI) potentiates existing brain damage and increases mortality and morbidity via poorly understood mechanisms. The aim of our study is to investigate the role of Sirtuin 3 (Sirt3) in the development and progression of cerebral ischemia-reperfusion injury with a focus on mitochondrial fission and the Wnt/β-catenin pathway. Our data indicated that Sirt3 was downregulated in response to cerebral IRI. However, the overexpression of Sirt3 reduced the brain infarction area and repressed IRI-mediated neuron apoptosis. Functional assays demonstrated that IRI augmented mitochondrial fission, which induced ROS overproduction, redox imbalance, mitochondrial pro-apoptotic protein leakage, and caspase-9-dependent cell death pathway activation. However, the overexpression of Sirt3 blocked mitochondrial fission and induced pro-survival signals in neurons subjected to IRI. At the molecular level, our data further illustrated that the Wnt/β-catenin pathway is required for the neuroprotection exerted by Sirt3 overexpression. Wnt/β-catenin pathway activation via inhibiting β-catenin phosphorylation attenuates mitochondrial fission and mitochondrial apoptosis. Collectively, our data show that cerebral IRI is associated with Sirt3 downregulation, Wnt/β-catenin pathway phosphorylated inactivation, and mitochondrial fission initiation, causing neurons to undergo caspase-9-dependent cell death. Based on this, strategies for enhancing Sirt3 activity and activating the Wnt/β-catenin pathway could be therapeutic targets for treating cerebral ischemia-reperfusion injury.

Metformin-Induced Mitochondrial Complex I Inhibition: Facts, Uncertainties, and Consequences

Metformin is the most widely prescribed drug to treat patients with type II diabetes, for whom retrospective studies suggest that metformin may have anticancer properties. However, in experiments performed with isolated cells, authors have reported both pro- and anti-apoptotic effects of metformin. The exact molecular mechanism of action of metformin remains partly unknown despite its use for over 60 years and more than 17,000 articles in PubMed. Among the various widely recognized or recently proposed targets, it has been reported consistently that metformin is capable of inhibiting mitochondrial respiratory chain Complex I. Since most of the effects of metformin have been replicated by other inhibitors of Complex I, it has been suggested that the mechanism of action of metformin involved the inhibition of Complex I. However, compared to conventional Complex I inhibitors, the metformin-induced inhibition of Complex I has unique characteristics. Among these, the most original one is that the concentrations of metformin required to inhibit Complex I are lower in intact cells than in isolated mitochondria. Experiments with isolated mitochondria or Complex I were generally performed using millimolar concentrations of metformin, while plasma levels remain in the micromolar range in both human and animal studies, highlighting that metformin concentration is an important issue. In order to explain the effects in animals based on observations in cells and mitochondria, some authors proposed a direct effect of the drug on Complex I involving an accumulation of metformin inside the mitochondria while others proposed an indirect effect (the drug no longer having to diffuse into the mitochondria). This brief review attempts to: gather arguments for and against each hypothesis concerning the mechanism by which metformin inhibits Complex I and to highlight remaining questions about the toxicity mechanism of metformin for certain cancer cells.