Upregulation of SIRT6 predicts poor prognosis and promotes metastasis of non-small cell lung cancer via the ERK1/2/MMP9 pathway

Cytotoxic Effects of 24-Methylenecyloartanyl Ferulate on A549 Nonsmall Cell Lung Cancer Cells through MYBBP1A Up-Regulation and AKT and Aurora B Kinase Inhibition

Lung cancer is the second most prevalent cancer. Nonsmall cell lung cancer (NSCLC) is the most common type of lung cancer. The low efficacy in current chemotherapies impels us to find new alternatives to prevent or treat NSCLC. Rice bran oil is cytotoxic to A549 cells, a NSCLC cell line. Here, we identified 24-methylenecyloartanyl ferulate (24-mCAF) as the main component responsible for the cytotoxicity in A549 cells. An iTRAQ-based quantitative proteomics analysis revealed that 24-mCAF inhibits cell proliferation and activates cell death and apoptosis. 24-mCAF induces up-regulation of Myb binding protein 1A (MYBBP1A), a tumor suppressor that halts cancer progression. 24-mCAF inhibits the activity of AKT and Aurora B kinase, two Ser/Thr kinases involved in MYBBP1A regulation and that represent important targets in NSCLC. This study provides the first insight of the effect of 24-mCAF, the main component of rice bran oil, on A459 cells at the cellular and molecular levels.

Exploring the key genes and pathways in enchondromas using a gene expression microarray

Enchondromas are the most common primary benign osseous neoplasms that occur in the medullary bone; they can undergo malignant transformation into chondrosarcoma. However, enchondromas are always undetected in patients, and the molecular mechanism is unclear. To identify key genes and pathways associated with the occurrence and development of enchondromas, we downloaded the gene expression dataset GSE22855 and obtained the differentially expressed genes (DEGs) by analyzing high-throughput gene expression in enchondromas. In total, 635 genes were identified as DEGs. Of these, 225 genes (35.43%) were up-regulated, and the remaining 410 genes (64.57%) were down-regulated. We identified the predominant gene ontology (GO) categories and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways that were significantly over-represented in the enchondromas samples compared with the control samples. Subsequently the top 10 core genes were identified from the protein-protein interaction (PPI) network. The enrichment analyses of the genes mainly involved in two significant modules showed that the DEGs were principally related to ribosomes, protein digestion and absorption, ECM-receptor interaction, focal adhesion, amoebiasis and the PI3K-Akt signaling pathway.Together, these data elucidate the molecular mechanisms underlying the occurrence and development of enchondromas and provide promising candidates for therapeutic intervention and prognostic evaluation. However, further experimental studies are needed to confirm these results.

Downregulation of SIRT6 by miR-34c-5p is associated with poor prognosis and promotes colon cancer proliferation through inhibiting apoptosis via the JAK2/STAT3 signaling pathway

Sirtuin 6 (SIRT6) is a member of the nicotinamide adenine dinucleotide positivity-dependent class III deacetylase sirtuin family. The present study aimed to explore the expression and function of SIRT6 in colon cancer. Furthermore, the partial mechanism underlying the dysregulation of SIRT6 was investigated. The results of immunohistochemistry demonstrated that SIRT6 was markedly downregulated in colon cancer tissues, and patients with high SIRT6 expression had a better prognosis than those who did not. The proliferation and apoptotic assays demonstrated that SIRT6 was able to suppress colon cancer cell proliferation and induce apoptosis via the Janus kinase 2 (JAK2)/signal transducer and activator of transcription 3 (STAT3) signaling pathway. MicroRNAs (miRNAs/miRs) are important non-coding RNAs, which have a critical role in the negative regulation of their target genes. Through bioinformatics analysis and further experiments, the results demonstrated that miR-34c-5p was not only dysregulated in colon cancer tissues but may also regulate SIRT6 expression via interaction with the 3′-untranslated region of SIRT6 mRNA. The proliferation and apoptotic assays indicated that miR-34c-5p could directly promote cell growth and inhibit apoptosis via activation of the JAK2/STAT3 signaling pathway, which was similar to silencing SIRT6. In conclusion, the results of the present study demonstrated that miR-34c-5p promoted colon cancer cell proliferation by targeting SIRT6 via activation of the JAK2/STAT3 signaling pathway. It may be hypothesized that SIRT6 is a potential biomarker for colon cancer prognosis, and the miR-34c-5p/SIRT6/JAK2/STAT3 axis may provide novel insights into colon cancer treatment.

Coordination of FOXA2 and SIRT6 suppresses the hepatocellular carcinoma progression through ZEB2 inhibition

Background

The Forkhead transcription family member FOXA2 plays a fundamental role in hepatocellular carcinoma (HCC) progression, but the precise interaction factor and molecular regulation of FOXA2 are not fully understood.

Objective

In this study, we found that FOXA2 could interact with sirtuin 6 (SIRT6) directly in vivo and in vitro. We explored that the expressions of FOXA2 and SIRT6 were significantly downregulated in human HCC and HCC cell lines.

Methods

Functionally, cell counting kit-8 assay and Transwell® assay were performed; we demonstrated that the knockdown of FOXA2 and SIRT6 promoted HepG2 cells and Huh7 cells proliferation and invasion in vitro.

Results

Mechanically, using luciferase reporter assay and fast chromatin immunoprecipitation assay, we showed that FOXA2 and SIRT6 regulated the expression of ZEB2 from transcription level. ZEB2 suppression was involved in the anti-oncogenesis effect of FOXA2 and SIRT6. The negative correlation between the expressions of ZEB2 and FOXA2 or SIRT6 was observed in the tissues of HCC patients.

Conclusion

Our findings indicated that the coordination function of FOXA2 and SIRT6 played a critical role in HCC progression and may serve as potential drug candidates for HCC.

SIRT6 inhibitors with salicylate-like structure show immunosuppressive and chemosensitizing effects

The NAD⁺-dependent deacetylase SIRT6 is an emerging cancer drug target, whose inhibition sensitizes cancer cells to chemo-radiotherapy and has pro-differentiating effects. Here we report on the identification of novel SIRT6 inhibitors with a salicylate-based structure. The new SIRT6 inhibitors show improved potency and specificity compared to the hit inhibitor identified in an in silico compound screen. As predicted based on SIRT6 biological roles, the new leads increase histone 3 lysine 9 acetylation and glucose uptake in cultured cells, while blocking TNF-α production and T lymphocyte proliferation. Notably, the new SIRT6 inhibitors effectively sensitize pancreatic cancer cells to gemcitabine. Finally, studies of compound fingerprinting and pharmacokinetics defined the drug-like properties of one of the new SIRT6 inhibitors, potentially allowing for subsequent in vivo proof-of-concept studies. In conclusion, new SIRT6 inhibitors with a salicylate-like structure were identified, which are active in cells and could potentially find applications in disease conditions, including cancer and immune-mediated disorders.

Association of sirtuins with clinicopathological parameters and overall survival in gastric cancer

To evaluate the associations of sirtuins (SIRT1-7) with clinicopathological parameters in gastric cancer, sirtuins expression profile in NCBI GEO datasets, GSE62254 and GSE15459, was integrated and analyzed. The results suggested that SIRT4, SIRT6, and SIRT7 were associated with Lauren classification and SIRT3-5 were associated with pStage in gastric cancer. Then an online database derived from 1,065 gastric cancer cases, Kaplan-Meier plotter, was used to explore the associations of the mRNA levels of sirtuins with overall survival in gastric cancer. Survival curves generated from Kaplan-Meier plotter suggested that high expression of SIRT1 mRNA was favorable for overall survival in gastric cancer (SIRT1: HR = 0.64, 95% CI = 0.54–0.76, P = 2.2E-07), high expressions of SIRT2-4 and SIRT6-7 were poor for overall survival (SIRT2: HR = 2.31, 95% CI = 1.87–2.87, P = 3.6E-15; SIRT3: HR = 1.99, 95% CI = 1.62–2.45, P = 2.6E-11; SIRT4: HR = 1.41, 95% CI = 1.19–1.68, P = 6.6E-05; SIRT6: HR = 2.02, 95% CI = 1.66–2.47, P = 1.7E-12; SIRT7: HR = 1.96, 95% CI = 1.63–2.35, P = 2.7E-13), whereas no significant association existed between SIRT5 mRNA expression and overall survival. Further analyses stratified by gender, stages, Lauren classification, differentiation, treatment, and HER2 status were also performed. In summary, high SIRT1 mRNA level was associated with better overall survival, SIRT2-4 and 6–7 were associated with poor overall survival, whereas SIRT5 did not show significant association with overall survival in gastric cancer.

Plasma microRNA alterations between EGFR-activating mutational NSCLC patients with and without primary resistance to TKI

Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) have obtained excellent therapeutic effects against non-small cell lung cancer (NSCLC) harboring activating EGFR mutations. However, some patients have exhibited primary resistance which becomes a major obstacle in effective treatment of NSCLC. The mechanisms of EGFR-TKIs resistance involved are still poorly understood. Many studies suggest that miRNAs play an important role in regulating drug sensitivity of EGFR-TKIs. The aim of the present study was to examine differentially expressed miRNAs in plasma between EGFR-TKIs sensitive and EGFR-TKIs primary resistance patients. MiRNA microarray of plasma from patients' blood identified 16 differentially expressed miRNAs of which 15 (hsv2-miR-H19, hsa-miR-744-5p, hsa-miR-3196, hsa-miR-3153, hsa-miR-4791, hsa-miR-4803, hsa-miR-4796-3p, hsa-miR-372-5p, hsa-miR-138-2-3p, hsa-miR-16-1-3p, hsa-miR-1469, hsa-miR-585-3p, ebv-miR-BART14-5p, hsa-miR-769-3p, hsa-miR-548aq-5p) were down regulated while only hsa-miR-503-3p was up regulated in primary resistant patients' plasma. Volcano plot and hierarchical clustering were performed to examine the accuracy of the miRNAs. Then validation with quantitative real-time PCR was performed and the result was in accordance with the array data. Functional analysis of these differentially expressed miRNAs with Ingenuity Pathway Analysis (IPA) revealed a common signaling network including MYC, CCND1, IGF1 and RELA. In conclusion, our finding may play important role in understanding the mechanisms underlying the problem and should be further evaluated as potential biomarkers in primary resistance of NSCLC.

Sirtuin 6 contributes to migration and invasion of osteosarcoma cells via the ERK1/2/MMP9 pathway

Dysregulation of sirtuin 6 (SIRT6) is actively involved in tumor progression. High levels of SIRT6 have been associated with hepatocellular carcinoma and non‐small cell lung cancer, and SIRT6 facilitates growth and metastasis of cancer cells. However, the clinical significance and biological function of SIRT6 are not known for osteosarcoma (OS). Here, we report that SIRT6 was notably overexpressed in OS tissues compared with non‐cancerous specimens. The high level of SIRT6 was prominently correlated with malignant clinical parameters and poor prognosis of OS patients. SIRT6 was also up‐regulated in OS cells. SIRT6 knockdown inhibited the invasion and migration of Saos‐2 and U2OS cells in vitro, while SIRT6 restoration increased these cellular biological behaviors in MG‐63 cells. Mechanistically, SIRT6 up‐regulated expression of matrix metallopeptidase 9 (MMP9) in OS cells. MMP9 restoration partially abolished the effects of SIRT6 knockdown on OS cells, with increased cell migration and invasion. MMP9 knockdown reduced migration and invasion of SIRT6‐overexpressing MG‐63 cells. Furthermore, SIRT6 positively modulated the levels of phosphorylated extracellular signal‐regulated kinases 1 and 2 (ERK1/2). PD098059 and PD0325901, inhibitors of mitogen‐activated protein kinase kinase (MEK), blocked the regulatory effects of SIRT6 on p‐ERK1/2 and MMP9 levels, suggesting that SIRT6 regulated MMP9 abundance probably through the MEK–ERK1/2 pathway. These results suggest that SIRT6 may act as a prognostic predictor and a drug target for OS patients.

EGF stimulates glioblastoma metastasis by induction of matrix metalloproteinase-9 in an EGFR-dependent mechanism

Epidermal growth factor (EGF) and EGF receptor (EGFR) play prominent roles in the metastasis of glioblastoma (GBM). However, the molecular mechanisms for the function of EGF and EGFR in GBM metastasis have not been elucidated. Herein, we demonstrate that coactivation of EGF and EGFR drives tumor metastasis in a matrix metalloproteinase-9 (MMP-9)-dependent manner. Expression levels of EGF, EGFR, and MMP-9 were substantially upregulated in the GBM and edema zones of patients, compared with those of paired unaffected participants. Secretion of EGF and MMP-9 was reduced in the cerebrospinal fluid (CSF) after removing GBM for 2 weeks by operation. To the mechanism, MMP-9 was upregulated by activating EGF and EGFR via PI3K/AKT- and ERK1/2-dependent pathways. Moreover, signal transducer and activator of transcription (STAT) 3 and STAT5 mediated the activation of NF-κB by PI3K/AKT and ERK1/2 pathways. This resulted in transactivation of MMP-9 in GBM. Finally, MMP-9 induction facilitated abnormal proliferation, migration, and invasion of cells, which contributed to GBM metastasis.

Overexpression of SIRT6 attenuates the tumorigenicity of hepatocellular carcinoma cells

Objective

This study aimed to explore the effects of overexpression of sirtuin 6 (SIRT6) on the tumorigenicity of hepatocellular carcinoma (HCC) cells

Methods

Stable SIRT6-overexpressed HCC cell lines were established by transfecting SIRT6 plasmid. Soft agar assay and tumor xenograft assay in nude mice were applied. Flow cytometry was employed to detect cell cycle distribution. Western blotting analysis was used to detect the expression of proteins.

Results

Overexpression of SIRT6 attenuated HepG2 and HCCLM3 cells proliferation, colony formation in vitro and tumor formation in nude mice, and resulted in the G1 phase cell cycle arrest. Overexpression of SIRT6 reduced the expression of cyclin D1 and p-ERK proteins in both HepG2 and HCCLM3 cells.

Conclusion

Overexpression of SIRT6 attenuates the tumorigenicity of HCC cells.

RASSF1A and SIRT6 in non-small cell lung cancer: Relationship with clinical outcome

This study investigated the expression of RASSF1A and SIRT6 in non-small cell lung cancer (NSCLC) and its relationship with clinical prognosis. The expression in 122 cases of NSCLC tissues (NSCLC group) and 122 cases of normal lung tissues (NOR group) during the same period were detected by immunohistochemical Super Pic Ture™ Polymer two-step method, and the relationship between its expression and the clinicopathological features and prognosis of patients was analyzed. The positive expression rates of RASSF1A and SIRT6 in NSCLC group were lower than those in the normal group (55.74 vs. 84.43% and 52.46 vs. 82.49%, P<0.01). The differences in expression intensity of RASSF1A in NSCLC tissues between different tumor pathological types, tumor differentiation degrees and lymph node metastases were statistically significant, and the differences in expression intensity of SIRT6 between different TNM stages, tumor differentiation degrees and lymph node metastases were statistically significant. There was a positive correlation between the expression of RASSF1A and SIRT6 in NSCLC group (r=0.532, P<0.01). The 3-year survival rate of patients with high-expression of RASSF1A was higher than in those with low-expression of RASSF1A (81.33 vs. 39.45%, log-rank χ²=19,102, P<0.01); the 3-year survival rate of patients with high-expression of SIRT6 was higher than in those with low-expression of SIRT6 (83.51 vs. 42.43%, log-rank χ²=17,180, P<0.01). The low expression of RASSF1A and SIRT6 and lymph node metastasis were the risk factors affecting the prognosis of NSCLC patients. There is a better correlation between the expression of RASSF1A and SIRT6 in NSCLC tissues, and the detection of their expression is of great significance in the judgement of clinicopathological features and prognosis of NSCLC patients.

SIRT6: Novel Mechanisms and Links to Aging and Disease

SIRT6, a member of the Sirtuin family of NAD⁺-dependent enzymes, has established roles in chromatin signaling and genome maintenance. Through these functions, SIRT6 protects against aging-associated pathologies including metabolic disease and cancer, and can promote longevity in mice. Research from the past few years revealed that SIRT6 is a complex enzyme with multiple substrates and catalytic activities, and uncovered novel SIRT6 functions in the maintenance of organismal health span. Here, we review these new discoveries and models of SIRT6 biology in four areas: heterochromatin stabilization and silencing; stem cell biology; cancer initiation and progression; and regulation of metabolic homeostasis. We discuss the possible implications of these findings for therapeutic interventions in aging and aging-related disease processes.

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

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