SIRT3 is correlated with the malignancy of non-small cell lung cancer

Mitochondrial sirtuin 3 and role of natural compounds: the effect of post-translational modifications on cellular metabolism

Sirtuins (SIRTs) are a family of proteins with enzymatic activity. In particular, they are a family of class III NAD+-dependent histone deacetylases and ADP-ribosyltransferases. NAD+-dependent deac(et)ylase activities catalyzed by sirtuin include ac(et)ylation, propionylation, butyrylation, crotonylation, manylation, and succinylation. Specifically, human SIRT3 is a 399 amino acid protein with two functional domains: a large Rossmann folding motif and NAD+ binding, and a small complex helix and zinc-binding motif. SIRT3 is widely expressed in mitochondria-rich tissues and is involved in maintaining mitochondrial integrity, homeostasis, and function. Moreover, SIRT3 regulates related diseases, such as aging, hepatic, kidney, neurodegenerative and cardiovascular disease, metabolic diseases, and cancer development. In particular, one of the most significant and damaging post-translational modifications is irreversible protein oxidation, i.e. carbonylation. This process is induced explicitly by increased ROS production due to mitochondrial dysfunction. SIRT3 is carbonylated by 4-hydroxynonenal at the level of Cys280. The carbonylation induces conformational changes in the active site, resulting in allosteric inhibition of SIRT3 activity and loss of the ability to deacetylate and regulate antioxidant enzyme activity. Phytochemicals and, in particular, polyphenols, thanks to their strong antioxidant activity, are natural compounds with a positive regulatory action on SIRT3 in various pathologies. Indeed, the enzymatic SIRT3 activity is modulated, for example, by different natural polyphenol classes, including resveratrol and the bergamot polyphenolic fraction. Thus, this review aims to elucidate the mechanisms by which phytochemicals can interact with SIRT3, resulting in post-translational modifications that regulate cellular metabolism.

SIRT3 Regulates the ROS-FPR1/HIF-1α Axis under Hypoxic Conditions to Influence Lung Cancer Progression

Hypoxia-inducible factor (HIF-1α) is a therapeutic target in lung cancer, and the deacetylase sirtuin 3 (SIRT3) is closely associated with tumorigenesis. Formyl peptide receptor 1 (FPR1) is involved in a wide range of physiopathological processes in various tumor cells. We explored whether SIRT3 affects the development of lung cancer by regulating the reactive oxygen species (ROS)-FPR1/HIF-1α axis under hypoxic conditions. The effects of SIRT3 overexpression on the levels of FPR1, HIF-1α, ROS, inflammatory factors, and cell proliferation and migration in A549 cells under hypoxic conditions were assessed in combination with the FPR1 inhibitor. BALB/c nude mice were subcutaneously injected with cancer cells transfected/untransfected with SIRT3 overexpressing lentiviral vectors. Immunohistochemistry and enzyme-linked immunosorbent assay were performed to detect SIRT3 expression and the expression levels of IL-1β, TNF-α, and IL-6, respectively, in tumor tissues. Cell proliferation, invasion, migration, and IL-1β, TNF-α, IL-6, and ROS levels were significantly higher in the Hypoxia group than in the Control group. Moreover, the mRNA and protein expression levels of SIRT3 were significantly down-regulated, whereas they were significantly up-regulated for FPR1 and HIF-1α. In contrast, SIRT3 overexpression in a hypoxic environment inhibited cell proliferation, invasion, and migration, decreased IL-1β, TNF-α, IL-6, and ROS levels, up-regulated the mRNA and protein expression levels of SIRT3, and down-regulated the mRNA and protein expression levels of FPR1 and HIF-1α. In addition, we found the same results in tumorigenic experiments in nude mice. SIRT3 in hypoxic environments may affect tumor cell proliferation, invasion, migration, and inflammation levels via the ROS-FPR1/HIF-1α axis, thereby inhibiting tumor cell development.

circ_rac GTPase-Activating Protein 1 Facilitates Stemness and Metastasis of Non-Small Cell Lung Cancer via Polypyrimidine Tract-Binding Protein 1 Recruitment to Promote Sirtuin-3-Mediated Replication Timing Regulatory Factor 1 Deacetylation

Circular RNAs have been identified as diagnostic and therapeutic targets for various tumors. The expression of circ_rac GTPase-activating protein 1 (circRACGAP1) is reported to drive the development of non-small cell lung cancer (NSCLC). This study further explored the potential mechanism of circRACGAP1-mediated development of NSCLC. The circRACGAP1 level was detected by quantitative RT-PCR. Sphere formation, CD133-positive cell percentage, and expression of octamer-binding transcription factor 4, Sox2, Nanog, and CD133 were detected to evaluate stemness of NSCLC. Migration and invasion were determined using wound healing and transwell assays. Protein expression was measured using Western blotting. The molecular mechanism was evaluated using RNA pull-down, RNA immunoprecipitation, and coimmunoprecipitation assays. In vivo tumor growth and metastasis were determined in nude mice. circRACGAP1 was highly expressed in NSCLC and was associated with stemness marker Sox2 expression. The stemness, metastasis, and epithelial mesenchymal transformation were repressed in circRACGAP1-depleted NSCLC cells. Mechanistically, circRACGAP1 recruited RNA-binding protein polypyrimidine tract-binding protein 1 to enhance the stability and expression of sirtuin-3 (SIRT3), which subsequently led to replication timing regulatory factor 1 (RIF1) deacetylation and activation of the Wnt/β-catenin pathway. circRACGAP1 overexpression counteracted SIRT3 or RIF1 knockdown-mediated inhibition in stemness and metastasis of NSCLC cells. The in vivo tumor growth and metastasis were repressed by circRACGAP1 depletion. Patients with NSCLC with a higher serum exosomal circRACGAP1 level had a lower overall survival rate. In conclusion, circRACGAP1 facilitated stemness and metastasis of NSCLC cells through the recruitment of polypyrimidine tract-binding protein 1 to promote SIRT3-mediated RIF1 deacetylation. Our results uncover a novel regulatory mechanism of circRACGAP1 in NSCLC and identify circRACGAP1 as a promising therapeutic target.

CRIF1 promotes the progression of non-small-cell lung cancer by SIRT3- mediated deacetylation of PYCR1

Lung cancer is the cancer with the highest mortality in the world. So further exploration of the pathogenesis of lung cancer is of great significance. In this study, the specific role and related mechanism of CRIF1 in non-small cell lung cancer (NSCLC) were explored in this research. TheRT-PCR, western blot and IHC assays were used to examine the expression level of CRIF1 in NSCLC tissue, tissue adjacent to carcinoma, NSCLC cell lines and human normal lung epithelial cells. Next, colony formation assay, Alamar blue Kit and EdU assays were employed to examine the proliferation of transfected A549 and NCI-H2009 cells. Measurement of mitochondrial permeability transition pore opening, ATP production and cellular oxygen consumption were used to evaluate the mitochondrial apoptosis of transfected NSCLC cells. Enzymatic activity assays for PYCR1, western blot and flow cytometry assays were used to explore the relationship between PYCR1 and CRIF1. The subcutaneous xenograft tumor mice model was established to explore the role of CRIF1 in vivo. Collectively, results revealed that CRIF1 was upregulated in NSCLC cells and tissues (p < 0.001). CRIF1 promoted proliferation of NSCLC cells (p < 0.001). CRIF1 inhibited mitochondrial apoptosis in NSCLC cells (p < 0.05). Moreover, CRIF1 promoted PYCR1 deacetylation and increased its activity through SIRT3 (p < 0.05). Deacetylation of PYCR1 reversed the antitumor effect of CRIF1 knockdown (p < 0.05). Finally, knockdown of CRIF1 inhibited the tumor growth of NSCLC in vivo (p < 0.05).This research found that CRIF1 promoted the progression of non-small-cell lung cancer by SIRT3- mediated deacetylation of PYCR1.

Flavonoids as Sirtuin Modulators

Sirtuins (SIRTs) are described as NAD+-dependent deacetylases, also known as class III histone deacetylases. So far, seven sirtuin genes (SIRTS 1-7) have been identified and characterized in mammals and also known to occur in bacteria and eukaryotes. SIRTs are involved in various biological processes including endocrine system, apoptosis, aging and longevity, diabetes, rheumatoid arthritis, obesity, inflammation, etc. Among them, the best characterized one is SIRT1. Actually, small molecules seem to be the most effective SIRT modulators. Flavonoids have been reported to possess many positive effects favrable for human health, while a relatively less research has been reported so far on their funcions as SIRT modulation mechanisms. In this regard, we herein aimed to focus on modulatory effects of flavonoids on SIRTs as the most common secondary metabolites in natural products. Our literature survey covering the years of 2006-2021 pointed out that flavonoids frequently interact with SIRT1 and SIRT3 followed by SIRT6. It can be also concluded that some popular flavonoid derivatives, e.g. resveratrol, quercetin, and catechin derivatives came forward in terms of SIRT modulation.

Sirt3 Promoted DNA Damage Repair and Radioresistance Through ATM-Chk2 in Non-small Cell Lung Cancer Cells

Objective: Radiotherapy is an indispensable approach for lung cancer, especially for non-small cell lung cancer (NSCLC) with high incidence and mortality. However, cellular resistance to ionizing radiation often results in failure in treatment. In this study, we aimed to investigate the role of Sirt3 in radiotherapy on NSCLC. Materials and Methods: Resected samples from 80 pairs of lung cancer was used to prepare tissue array and Sirt3 was stained with immunochemical method. Cell survival as well as apoptosis assay were used to determine the cellular radiosensitivity. Moreover, DNA damage was evaluated by using γ-H2AX foci. Finally, an in situ lung cancer model to test the radiosensitivity in vivo. Results: Sirtuin 3 (Sirt3) was found upregulated in NSCLC cell lines, as well as lung cancer tissues compared with normal tissues. Knockdown of Sirt3 significantly increased radiation-induced cell apoptosis, and increased cell survival efficacy. In contrast, Sirt3 overexpression promoted radioresistance in lung cancer cells. Sirt3 knockdown also aggravated the G2/M cell cycle arrest caused by irradiation. Furthermore, Sirt3 was found to be critical for the activation of ATM-Chk2 pathway upon irradiation. Finally, our in vivo model showed that targeting Sirt3 significantly sensitized lung cancer to radiotherapy. Conclusion: In conclusion, our findings identified a significant role of Sirt3 in radioresistanct of NSCLC, which provides novel mechanism as well as target for radiotherapy.

SIRT4 and SIRT6 Serve as Novel Prognostic Biomarkers With Competitive Functions in Serous Ovarian Cancer

Sirtuins (SIRTs) are class III histone deacetylases (HDACs) that include seven members and are widely expressed in mammals. Accumulating evidence shows that sirtuins may have contradictory roles in various malignancies. They mainly participate in metabolic homeostasis, DNA damage repair, cell survival, and differentiation, as well as other cancer-related biological processes. To better understand their prognostic role and biological functions, we used comprehensive bioinformatic analyses to demonstrate the expression and mutation of sirtuin family member genes in ovarian cancer (OC), with a detailed focus on prognostic prediction, including the effectiveness of anti-OC drugs. Furthermore, the co-expression genes of SIRT4 and SIRT6 with contradictory survival prediction values in both overall and progression-free survival (PFS) times were further analyzed through Gene Ontology enrichment and Kyoto Encyclopedia annotation. Additionally, we performed and obtained the immunohistochemical staining patterns of these two biomarkers from the serous OC patient database and clinical patient samples to demonstrate their potential applicability in clinical pathology. According to our findings, SIRT4 and SIRT6 are novel prognostic biomarkers that may serve as contradictory competitors for OC cell survival. They are also sensitive biomarkers for the prediction of Avastin's anticancer effect. While SIRT4 is related to the immune response during oocyte maturation, SIRT6 participates in immune-related disease pathways and mitochondrial metabolism-mediated DNA translation. These findings contribute to the novel hypothesis that SIRT4 and SIRT6 act as contradictory competitors in the regulation of OC behavior. Further studies are required to validate our hypothesis.

SIRT3 acts as a novel biomarker for the diagnosis of lung cancer: A retrospective study

Lung cancer (LC) is a prevalent malignancy worldwide with increased morbidity and mortality. Mitochondrial nicotinamide adenine dinucleotide-dependent deacetylase sirtuin-3 (SIRT3) has been reported to be involved in tumorigenesis. In this retrospective study, we measured the expression and diagnostic value of SIRT3 in LC patients.Quantitative real-time polymerase chain reaction (qRT-PCR) was performed to measure serum SIRT3 mRNA level in 150 LC patients and 52 healthy volunteers. SIRT3 protein level was detected using western blot for 84 pairs of LC and adjacent normal tissues. The association of SIRT3 mRNA level with clinical parameters of LC patients was estimated via chi-square test. Receiver operating characteristic curve (ROC) was plotted to evaluate the diagnostic performance of serum SIRT3 in LC patients.SIRT3 mRNA and protein levels were significantly decreased in LC tissues and serum samples, compared with corresponding controls (P < .05). Moreover, the expression of SIRT3 mRNA was negatively associated with tumor size (P = .002), tumor node metastasis stage (P < .001), and metastasis (P < .001). ROC curve demonstrated that serum SIRT3 could distinguish LC patients from healthy individuals, with an area under the curve of 0.918. The optimal cutoff value was 3.12, reaching a sensitivity of 86.4%, and a specificity of 94%.SIRT3 expression is significantly down-regulated in LC serum and tissues. SIRT3 may be employed as a promising biomarker in the early diagnosis of LC.

STYK1/NOK Promotes Metastasis and Epithelial-Mesenchymal Transition in Non-small Cell Lung Cancer by Suppressing FoxO1 Signaling

Aims

Serine/threonine/tyrosine kinase 1 (STYK1) has been previously shown to have oncogenic properties, and emerging evidence suggests that STYK1 expression correlates with epithelial-mesenchymal transition (EMT). However, the mechanism of STYK1 involvement in oncogenesis remains unknown. The present study aimed to elucidate how STYK1 expression level relates to the metastasis, migration, invasion, and EMT in non-small cell lung cancer (NSCLC) and to determine the molecular mechanism of STYK1 effects.

Methods

Serine/threonine/tyrosine kinase 1 (STYK1) expression level and its relationship with the prognosis of NSCLC were determined using the ONCOMINE database and clinical cases. Non-small cell lung cancer cell lines with the overexpression or knockdown of STYK1 were established to determine whether STYK1 promotes cell migration, invasion, and EMT in vitro and in vivo. In addition, a constitutively active FoxO1 mutant (FoxO1AAA) was used to examine the role of FoxO1 in the STYK1-mediated upregulation of metastasis and EMT in NSCLC.

Results

Serine/threonine/tyrosine kinase 1 (STYK1) was upregulated in NSCLC tissues and cell lines, and its overexpression correlated with poor prognosis in patients with NSCLC after surgery. Enhanced expression of STYK1 potentiated the migration, invasion, and EMT in SW900 cells, thereby promoting metastasis, whereas knockdown of STYK1 inhibited these cellular phenomena in Calu-1 cells. Furthermore, STYK1 expression was positively related to the level of phosphorylated-FoxO1, whereas the constitutively active FoxO1 mutant protected against the positive effect of STYK1 overexpression on cell migration, invasion, and EMT.

Conclusion

Serine/threonine/tyrosine kinase 1 (STYK1) was upregulated in NSCLC and correlated with poor clinical outcomes. In addition, STYK1 suppressed FoxO1 functions, thereby promoting metastasis and EMT in NSCLC.

SIRT2 and SIRT3 expression correlates with redox imbalance and advanced clinical stage in patients with multiple myeloma

OBJECTIVES

Sirtuins comprise seven family elements (SIRT1-7) involved in various cell signalling pathways comprising cancer inhibition and tumorigenesis. The present study aims to evaluate SIRT2 and SIRT3 gene expression and potential redox reactions in patients with multiple myeloma (MM) at onset and its correlation with disease status, extent and presence of organ damage secondary to myeloma.

DESIGN & METHODS

Total RNA was extracted from 17 MM patients and 10 controls to assess gene expression using real-time PCR. The NAD+/NADH ratio as well as the levels of glutathione peroxidase (GPx) and hydrogen peroxide (HP) in peripheral blood mononuclear cells (PBMCs) were determined using established biochemical assays.

RESULTS

SIRT2 and SIRT3 expression is reduced in MM patients compared to healthy controls. Correlational analysis demonstrated that SIRT2 reduction is associated with advanced clinical stage and with more advanced bone lesions than in the remaining patients. SIRT3 expression is correlated with lytic bone lesions. Biochemical analysis indicated an imbalance of oxidative stress biomarkers with low concentrations of the antioxidant enzyme GPx, low amounts of NAD + and higher concentrations of pro-oxidant enzyme HP in PBMCs of MM patients compared to controls. Moreover, MM patients with bone lesions had lower concentrations of NAD + and GPx in PBMCs than patients without signs of bone disease. In addition, MM patients had higher quantities of intracellular HP than controls.

CONCLUSIONS

Our results demonstrate that SIRT2 and SIRT3 are downregulated in MM and that lower concentrations correlate with an advanced stage of disease and redox imbalance. We conclude that SIRT2 and SIRT3 together with oxidative stress biomarkers, may be useful for improved risk stratification of MM patients.

Mitochondrial sirtuins in stem cells and cancer

The mammalian sirtuin family consists of seven proteins, three of which (SIRT3, SIRT4, and SIRT5) localise specifically within mitochondria and preserve mitochondrial function and homeostasis. Mitochondrial sirtuins are involved in diverse functions such as deacetylation, ADP-ribosylation, demalonylation and desuccinylation, thus affecting various aspects of cell fate. Intriguingly, mitochondrial sirtuins are able to manage these delicate processes with accuracy mediated by crosstalk between the nucleus and mitochondria. Previous studies have provided ample information about their substrates and targets, whereas less is known about their role in cancer and stem cells. Here, we review and discuss recent advances in our understanding of the structural and functional properties of mitochondrial sirtuins, including their targets in cancer and stem cells. These advances could help to improve the understanding of their interplay with signalling cascades and pathways, leading to new avenues for developing novel drugs for sirtuin-related disease treatments. We also highlight the complex network of mitochondrial sirtuins in cancer and stem cells, which may be important in deciphering the molecular mechanism for their activation and inhibition.

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.

Resveratrol's Anti-Cancer Effects through the Modulation of Tumor Glucose Metabolism

Simple Summary

The prevention and treatment of cancer is an ongoing medical challenge. In the context of personalized medicine, the well-studied polyphenol resveratrol could complement classical tumor therapy. It may affect key processes such as inflammation, angiogenesis, proliferation, metastasis, glucose metabolism, and apoptosis in various cancers because resveratrol acts as a multi-targeting agent by modulating multiple signal transduction pathways. This review article focuses on resveratrol’s ability to modify tumor glucose metabolism and its associated therapeutic capacity. Resveratrol reduces glucose uptake and glycolysis by affecting Glut1, PFK1, HIF-1α, ROS, PDH, and the CamKKB/AMPK pathway. It also inhibits cell growth, invasion, and proliferation by targeting NF-kB, Sirt1, Sirt3, LDH, PI-3K, mTOR, PKM2, R5P, G6PD, TKT, talin, and PGAM. In addition, resveratrol induces apoptosis by targeting integrin, p53, LDH, and FAK. In conclusion, resveratrol has many potentials to intervene in tumor processes if bioavailability can be increased and this natural compound can be used selectively.

Abstract

Tumor cells develop several metabolic reprogramming strategies, such as increased glucose uptake and utilization via aerobic glycolysis and fermentation of glucose to lactate; these lead to a low pH environment in which the cancer cells thrive and evade apoptosis. These characteristics of tumor cells are known as the Warburg effect. Adaptive metabolic alterations in cancer cells can be attributed to mutations in key metabolic enzymes and transcription factors. The features of the Warburg phenotype may serve as promising markers for the early detection and treatment of tumors. Besides, the glycolytic process of tumors is reversible and could represent a therapeutic target. So-called mono-target therapies are often unsafe and ineffective, and have a high prevalence of recurrence. Their success is hindered by the ability of tumor cells to simultaneously develop multiple chemoresistance pathways. Therefore, agents that modify several cellular targets, such as energy restriction to target tumor cells specifically, have therapeutic potential. Resveratrol, a natural active polyphenol found in grapes and red wine and used in many traditional medicines, is known for its ability to target multiple components of signaling pathways in tumors, leading to the suppression of cell proliferation, activation of apoptosis, and regression in tumor growth. Here, we describe current knowledge on the various mechanisms by which resveratrol modulates glucose metabolism, its potential as an imitator of caloric restriction, and its therapeutic capacity in tumors.

SIRT3-Mediated SOD2 and PGC-1α Contribute to Chemoresistance in Colorectal Cancer Cells

BACKGROUND

Anticancer drugs generate excessive reactive oxygen species (ROS), which can cause cell death. Cancer cells can resist this oxidative stress, but the mechanism of resistance and associations with chemoresistance are unclear. Here, we focused on Sirtuin 3 (SIRT3), a deacetylating mitochondrial enzyme, in oxidative stress resistance in colorectal cancer (CRC).

METHODS

To evaluate SIRT3-related changes in mitochondrial function, ROS (mtROS) induction, and apoptosis, we used the human CRC cell lines HT29 and HCT116 transfected with short-hairpin RNA targeting SIRT3 and small interfering RNAs targeting superoxide dismutase 2 mitochondrial (SOD2) and peroxisome proliferator-activated receptor γ coactivator-1 (PGC-1α). In 142 clinical specimens from patients with CRC, we also assessed the association of SIRT3 protein levels (high/low) and prognosis.

RESULTS

SIRT3 expression correlated with mtROS generation and apoptosis induction in cells treated with anticancer agents. Suppressing SIRT3 increased mtROS levels and cell sensitivity to anticancer agents. SIRT3 knockdown decreased SOD2 expression and activity, and suppressing SOD2 also improved sensitivity to anticancer drugs. In addition, SIRT3 was recruited with PGC-1α under oxidative stress, and suppressing SIRT3 decreased PGC-1α expression and mitochondrial function. PGC-1α knockdown decreased mitochondrial activity and increased apoptosis in cells treated with anticancer drugs. In resected CRC specimens, high vs low SIRT3 protein levels were associated with significantly reduced cancer-specific survival.

CONCLUSIONS

SIRT3 expression affected CRC cell chemoresistance through SOD2 and PGC-1α regulation and was an independent prognostic factor in CRC. SIRT3 may be a novel target for CRC therapies and a predictive marker of sensitivity to chemotherapy.

Nicotinic-nAChR signaling mediates drug resistance in lung cancer

Lung cancer is the leading cause of cancer death worldwide. Cigarette smoking is the most common risk factor for lung carcinoma; other risks include genetic factors and exposure to radon gas, asbestos, secondhand smoke, and air pollution. Nicotine, the primary addictive constituent of cigarettes, contributes to cancer progression through activation of nicotinic acetylcholine receptors (nAChRs), which are membrane ligand-gated ion channels. Activation of nicotine/nAChR signaling is associated with lung cancer risk and drug resistance. We focused on nAChR pathways activated by nicotine and its downstream signaling involved in regulating apoptotic factors of mitochondria and drug resistance in lung cancer. Increasing evidence suggests that several sirtuins play a critical role in multiple aspects of cancer drug resistance. Thus, understanding the consequences of crosstalk between nicotine/nAChRs and sirtuin signaling pathways in the regulation of drug resistance could be a critical implication for cancer therapy.

Aberrantly High Expression Of NOK/STYK1 Is Tightly Associated With The Activation Of The AKT/GSK3β/N-Cadherin Pathway In Non-Small Cell Lung Cancer

Purpose

High metastasis is a leading risk factor for the survival of non-small cell lung cancer (NSCLC) and epithelial-mesenchymal transition (EMT) is a vital step of metastasis. The expression of novel oncogene with kinase domain (NOK) has been observed in some human malignancies, including non-small cell lung cancer (NSCLC); however, the biological function of NOK in NSCLC remains unclear. In the study, we explored the function of NOK in NSCLC, with an aim to elucidate the relevant underlying mechanisms.

Patients and methods

We investigate the expression of NOK, p-Akt, p-GSK-3β, E-cadherin and N-cadherin expression by immunohistochemical analysis using tissue microarrays of 72 paired NSCLC samples of cancerous and adjacent normal tissues. The associations between NOK expression and clinicopathological factors, overall survival, other proteins were assessed. Immunofluorescence analysis of NSCLC tissues was performed to study the location of NOK, Akt and GSK-3β. Up or down-regulated of NOK were conducted in two NSCLC cell lines to analyze its impact on AKT/GSK3β pathway.

Results

Statistical analysis revealed NOK expression increased in NSCLC tissues compared with normal tissues (P<0.05). It also showed that low NOK expression were associated with a higher possibility of non-lymphatic metastasis, an early pN stage and clinical stage (P<0.05). Moreover, NOK expression was positively correlated with the expression of oncogene p-Akt (Thr308), p-GSK-3β (Ser9) and N-cadherin (P<0.05). Immunofluorescence analysis of NSCLC tissues revealed that NOK is co-located with Akt and GSK-3β. Further study in NSCLC cell lines revealed that NOK overexpression can activate the AKT/GSK3β pathway. Conversely, knockdown of NOK can suppress the AKT/GSK3β pathway.

Conclusion

Our results suggest that NOK overexpression correlated significantly with lymphatic metastasis, advanced pN and clinical stage in NSCLC. And NOK may promote EMT by activating the AKT/GSK3β/N-cadherin pathway in NSCLC.

Sirtuin 3 deficiency does not impede digit regeneration in mice

The mitochondrial deacetylase sirtuin 3 (SIRT3) is thought to be one of the main contributors to metabolic flexibility-promoting mitochondrial energy production and maintaining homeostasis. In bone, metabolic profiles are tightly regulated and the loss of SIRT3 has deleterious effects on bone volume in vivo and on osteoblast differentiation in vitro. Despite the prominent role of this protein in bone stem cell proliferation, metabolic activity, and differentiation, the importance of SIRT3 for regeneration after bone injury has never been reported. We show here, using the mouse digit amputation model, that SIRT3 deficiency has no impact on the regenerative capacity and architecture of bone and soft tissue. Regeneration occurs in SIRT3 deficient mice in spite of the reduced oxidative metabolic profile of the periosteal cells. These data suggest that bone regeneration, in contrast to homeostatic bone turnover, is not reliant upon active SIRT3, and our results highlight the need to examine known roles of SIRT3 in the context of injury.

STYK1/NOK correlates with ferroptosis in non-small cell lung carcinoma

Serine Threonine Tyrosine Kinase 1 (STYK1) presents oncogenic properties in many studies, and emerging evidence suggests that ferroptosis serve as a novel tumor suppressor. However, the interplay between STYK1 and ferroptosis in NSCLC remains unclear. Our aim is to illustrate the expression of ferroptotic regulator Glutathione peroxidase 4 (GPX4) in NSCLC and the relationship between STYK1 and ferroptosis. Herein, results based on ONCOMINE database, clinical specimens, and cellular manipulation revealed GPX4 was upregulated in NSCLC tissues and cell lines, and high GPX4 expression predicted worse prognosis. High STYK1 expression predicted worse OS and was related to high GPX4 in NSCLC tissues; overexpression of STYK1 in lung cancer cell line SW900 upregulated the expression of GPX4, promoted proliferation, and attenuated diverse mitochondrial abnormalities specific to ferroptosis, whereas knockdown of GPX4 exacerbated such attenuations without affecting cell proliferation. Taken together, ferroptosis as an anti-tumor factor is inhibited in NSCLC, and targeting ferroptosis could be a novel therapeutic strategy for the management of NSCLC; furthermore, regulating ferroptosis could be another cancerous mechanism of STYK1.

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.

Associations of sirtuins with clinicopathological parameters and prognosis in non-small cell lung cancer

BACKGROUND

Lung cancer is the leading cause of cancer-related death worldwide and it is critical to discover specific biomarkers to provide better individualized treatment and subsequently better prognosis. The sirtuins (SIRT1-7) have been reported to be involved in cancers including non-small cell lung cancer (NCSLC), however, the results are not consistent and not all the seven sirtuins are explored and compared.

METHODS

TCGA data was downloaded and used to investigate and compare the associations of sirtuins mRNA levels with clinicopathological parameters and prognosis in NSCLC.

RESULTS

Our results suggested SIRT1, SIRT3, SIRT4, and SIRT7 were highly expressed in adeno-carcinoma (ADC) patients and female patients while SIRT5 were highly expressed in squamous cell carcinoma (SCC) patients and male patients. Associations of high SIRT7 with younger onset age, high SIRT1 with distant metastasis and low T stage, and high SIRT4 with high T stage and TNM stage were also found. Kaplan-Meier plot curves and univariate Cox proportional regression analyses indicated that high SIRT2, SIRT4, and SIRT6 expressions were associated with longer overall survival (OS) time. Multivariate analyses indicated that SIRT2 and SIRT6 were still associated with OS. For recurrence-free survival (RFS), high SIRT1 expression was significantly associated with shorter RFS time while high SIRT2-3 and SIRT5-7 expressions were associated with longer RFS time in univariate analyses. After adjusting the confounding factors, significant associations were still found in SIRT1-2 and SIRT5-7 but not in SIRT3. We also stratified the patients by combining SIRT1 and SIRT2 and revealed that the combination of SIRT1 and SIRT2 was a better prediction model for RFS in NSCLC. To preliminarily understand the potential mechanisms of sirtuins in NSCLC carcinogenesis, the genes co-expressed with sirtuins were analyzed and annotated.

CONCLUSION

sirtuins might be the potential therapy targets and prognostic biomarkers in NSCLC.

Diabetes induces fibrotic changes in the lung through the activation of TGF-β signaling pathways

In the long term, diabetes profoundly affects multiple organs, such as the kidney, heart, brain, liver, and eyes. The gradual loss of function in these vital organs contributes to mortality. Nonetheless, the effects of diabetes on the lung tissue are not well understood. Clinical and experimental data from our studies revealed that diabetes induces inflammatory and fibrotic changes in the lung. These changes were mediated by TGF-β-activated epithelial-to-mesenchymal transition (EMT) signaling pathways. Our studies also found that glucose restriction promoted mesenchymal-to-epithelial transition (MET) and substantially reversed inflammatory and fibrotic changes, suggesting that diabetes-induced EMT was mediated in part by the effects of hyperglycemia. Additionally, the persistent exposure of diabetic cells to high glucose concentrations (25 mM) promoted the upregulation of caveolin-1, N-cadherin, SIRT3, SIRT7 and lactate levels, suggesting that long-term diabetes may promote cell proliferation. Taken together, our results demonstrate for the first time that diabetes induces fibrotic changes in the lung via TGF-β1-activated EMT pathways and that elevated SMAD7 partially protects the lung during the initial stages of diabetes. These findings have implications for the management of patients with diabetes.

Sirt3 deficiency impairs neurovascular recovery in ischemic stroke

AIMS

Sirt3 is one member of the NAD⁺ -dependent protein deacetylase family and plays crucial roles in diverse aspects of mammalian biological function. Then the role of Sirt3 on ischemia stroke is unknown.

METHODS

To examine the effect of Sirt3 on ischemic stroke, we performed transient middle cerebral artery occlusion (tMCAO) in adult male Sirt3 knockout (KO) and wild-type (WT) mice.

RESULTS

The level of Sirt3 in infarct region is decreased after ischemic stroke. In addition, we found that Sirt3 KO mice showed worse neurobehavioral outcome compared with WT mice, accompanied by decreased neurogenesis and angiogenesis as shown by the reduction in number of DCX⁺ /BrdU⁺ cells, NeuN⁺ /BrdU⁺ cells, and CD31⁺ /BrdU⁺ cells in the perifocal region during recovery phase after ischemic stroke. Furthermore, Sirt3 deficiency reduced the activation of vascular endothelial growth factor (VEGF), AKT, and extracellular signal-regulated kinases (ERK) signaling pathways.

CONCLUSION

Our results indicated that Sirt3 is beneficial to neurovascular and functional recovery following chronic ischemic stroke.

Prognostic and clinicopathological value of SIRT3 expression in various cancers: a systematic review and meta-analysis

Background

Several studies have explored the prognostic value of sirtuin 3 (SIRT3) in various cancers, but obtained inconsistent results. The current systematic review and meta-analysis was conducted to investigate the association between SIRT3 expression and prognosis in various cancers.

Methods

PubMed, Embase, Web of Science and the Cochrane Library were comprehensively retrieved by the end of September 29, 2017. All the relevant studies were checked and included in the meta-analysis if they met the inclusion criteria.

Results

A total of 17 studies involving 2,865 patients were included in the systematic review and meta-analysis. The results indicated that SIRT3 expression was not significantly associated with overall survival (OS) (hazard ratio [HR]=0.87, 95% CI=0.59–1.29, P=0.50) and disease-free survival (HR=0.87, 95% CI=0.57–1.31, P=0.50) in total various cancers. However, significant relationship between SIRT3 expression and OS in specific cancers was detected, including chronic lymphocytic leukemia (CLL) (HR=0.48, 95% CI=0.26–0.89, P=0.019), hepatocellular carcinoma (HCC) (HR=0.56, 95% CI=0.42–0.74, P<0.001), pancreatic carcinoma (PC) (HR=0.55, 95% CI=0.30–1.00, P=0.049), renal cell carcinoma (RCC) (HR=0.13, 95% CI=0.02–0.98, P=0.048), breast cancer (BC) (HR=2.53, 95% CI=1.83–3.67, P<0.001), colon cancer (CC) (HR=1.87, 95% CI=1.12–3.26, P=0.022) and non-small-cell lung cancer (NSCLC) (HR=2.20, 95% CI=1.38–3.50, P=0.001). Moreover, SIRT3 expression was obviously associated with tumor size (odds ratio [OR]=1.41, 95% CI=1.02–1.94, P=0.04), tumor differentiation (OR=1.52, 95% CI=1.08–2.16, P=0.02) and clinical stage (OR=2.07, 95% CI=1.23–3.46, P=0.01) in HCC.

Conclusion

SIRT3 was distinctly related to the OS in specific cancers. SIRT3 was an unfavorable prognostic factor in BC, CC and NSCLC; however, it was also a favorable prognostic factor in CLL, HCC, PC and RCC, especially in HCC.

SIRT3 deacetylates and promotes degradation of P53 in PTEN-defective non-small cell lung cancer

PURPOSE

In non-small cell lung cancer (NSCLC), success of targeted therapy has promoted researches explicitly orientated based on genetic background. Although PTEN deficiency is common in NSCLC, carcinogenesis about such genetic type has not been fully explored. Here, we have found that classical tumor suppressor P53 could be modulated by deacetylase sirtuin-3 (SIRT3) depending on the PTEN condition in NSCLC, which may be a novel breakpoint for handling PTEN deficiency NSCLC.

METHODS

First, we examined SIRT3 and P53 expression files in PTEN-deficient NSCLC clinical samples and investigated their correlation. Second, we built SIRT3 high or low expression models in different PTEN conditions by plasmid overexpression or si-RNA interference in NSCLC cell lines and explored the effect of SIRT3 upon P53. Furthermore, we investigated the influence of SIRT3 upon the ubiquitin-proteasome dependent degradation pathway of P53 in PTEN-deficient NSCLC cell lines. Finally, we probed into the deacetylation modification of P53 via SIRT3.

RESULTS

We found that SIRT3 expression was strongly positive and P53 expression was almost negative in PTEN-deficient NSCLC clinical samples. Further, we demonstrated that SIRT3 promoted degradation of P53 in PTEN-deficient NSCLC cell lines via the ubiquitin-proteasome pathway. Finally, we demonstrated that SIRT3 could deacetylate P53 at lysines 320 and 382, which may account for the observed degradation of P53 in PTEN-deficient tumor cells.

CONCLUSIONS

We have identified a novel mechanism by which P53 was inactivated via SIRT3 in PTEN-deficient cells. This may shed light on the mechanisms underlying the malignancy of PTEN-deficient NSCLC.