SUN2: A potential therapeutic target in cancer.

The incidence of cancer is increasing at an alarming rate despite recent advances in prevention strategies, diagnostics and therapeutics for various types of cancer. The identification of novel biomarkers to aid in prognosis and treatment for cancer is urgently required. Uncontrolled proliferation and dysregulated apoptosis are characteristics exhibited by cancer cells in the initiation of various types of cancer. Notably, aberrant expression of crucial oncogenes or cancer suppressors is a defining event in cancer occurrence. Research has demonstrated that SAD1/UNC84 domain protein-2 (SUN2) serves a suppressive role in breast cancer, atypical teratoid/rhabdoid tumors and lung cancer progression. Furthermore, SUN2 inhibits cancer cell proliferation, migration and promotes apoptosis. Recent reports have also shown that SUN2 serves prominent roles in resistance to the excessive DNA damage that destabilizes the genome and promotes cancer development, and these functions of SUN2 are critical for evading initiation of cancer. Additionally, increasing evidence has demonstrated that SUN2 is involved in maintaining cell nuclear structure and appears to be a central component for organizing the natural nuclear architecture in cancer cells. The focus of the present review is to provide an overview on the pharmacological functions of SUN2 in cancers. These findings suggest that SUN2 may serve as a promising therapeutic target and novel predictive marker in various types of cancer.

Suppression of SUN2 by DNA methylation is associated with HSCs activation and hepatic fibrosis.

Hepatic myofibroblasts, activated hepatic stellate cells (HSCs), are the main cell type of extracellular matrix (ECM) deposition during hepatic fibrosis. Aberrant DNA methylation-regulated HSCs activation in liver fibrogenesis has been reported, but the functional roles and mechanisms of DNA methylation in hepatic fibrosis remain to be elucidated. In the present study, reduced representation bisulfite sequencing (RRBS) analysis of primary HSCs revealed hypermethylation patterns in hepatic fibrosis. Interestingly, we found SAD1/UNC84 domain protein-2 (SUN2) gene hypermethylation at CpG sites during liver fibrogenesis in mice with CCl4-induced hepatic fibrosis, which was accompanied by low expression of SUN2. In vivo overexpression of SUN2 following adeno-associated virus-9 (AAV9) administration inhibited CCl4-induced liver injury and reduced fibrogenesis marker expression. Consistently, in vitro experiments showed that enforced expression of SUN2 suppressed HSCs activation and exerted anti-fibrogenesis effects in TGF-ß1-activated HSC-T6 cells. In addition, the signaling mechanisms related to SUN2 expression were investigated in vivo and in vitro. Methyltransferase-3b (DNMT3b) is the principal regulator of SUN2 expression. Mechanistically, inhibition of protein kinase B (AKT) phosphorylation may be a crucial pathway for SUN2-mediated HSCs activation. In conclusion, these findings provide substantial new insights into SUN2 in hepatic fibrosis.

PSTPIP2 connects DNA methylation to macrophage polarization in CCL4-induced mouse model of hepatic fibrosis.

Macrophages play a crucial role in the progression of hepatic fibrosis (HF). In macrophages, epigenetic mechanisms are increasingly being recognized as crucial controllers of their phenotype. However, the functions of macrophage DNA methylation in experimental models of hepatic fibrosis have not been fully addressed. Here, we analyzed isolated hepatic macrophages DNA methylation from CCL4-induced (4 weeks) mice using reduced representation bisulfite sequencing (RRBS). We identified and validated the methylation status of 26 gene promoter regions associated with CpG islands. We further investigated the function of PSTPIP2 in HF by hepatic-adeno-associated virus (AAV9)-PSTPIP2 overexpression. The molecular mechanisms underlying PSTPIPS2-regulated HF were further explored in mice and RAW264.7 cell line. RRBS results show hypermethylation of PSTPIP2 (chr18: 77,843,840-77,843,968) in the 5'-UTR region. PSTPIP2 expression was significantly decreased in isolated hepatic macrophages from CCL4-induced mice. PSTPIP2 hypermethylation is mediated by the methyltransferases DNMT3a and DNMT3b in LPS-induced RAW264.7 cell line. Further investigation indicated that specific overexpression of PSTPIP2 in C57BL/6 mice reduced the inflammatory response and ameliorated liver fibrosis. These data indicated that hypermethylation of PSTPIP2 caused a mixed induction of hepatic classical macrophage (M1) and alternative macrophage (M2) biomarkers in CCL4-induced HF mice. Furthermore, overexpression of PSTPIP2 inhibited the expression of M1 markers by suppressing STAT1 activity, and enhanced the expression of M2 markers by promoting STAT6 activity. In contrast, knockdown of PSTPIP2 promoted M1 polarization and suppressed M2 polarization in vitro. Adding PSTPIP2 expression alleviates liver fibrosis and hepatic inflammation in mice by regulating macrophage polarization.

EZH2-mediated repression of Dkk1 promotes hepatic stellate cell activation and hepatic fibrosis.

EZH2, a histone H3 lysine-27-specific methyltransferase, is involved in diverse physiological and pathological processes including cell proliferation and differentiation. However, the role of EZH2 in liver fibrosis is largely unknown. In this study, it was identified that EZH2 promoted Wnt pathway-stimulated fibroblasts in vitro and in vivo by repressing Dkk-1, which is a Wnt pathway antagonist. The expression of EZH2 was increased in CCl4 -induced rat liver and primary HSCs as well as TGF-ß1-treated HSC-T6, whereas the expression of Dkk1 was reduced. Silencing of EZH2 prevented TGF-ß1-induced proliferation of HSC-T6 cells and the expression of α-SMA. In addition, knockdown of Dkk1 promoted TGF-ß1-induced activation of HSCs. Moreover, silencing of EZH2 could restore the repression of Dkk-1 through trimethylation of H3K27me3 in TGF-ß1-treated HSC-T6 cells. Interestingly, inhibition of EZH2 had almost no effect on the activation of HSC when Dkk1 was silenced. Collectively, EZH2-mediated repression of Dkk1 promotes the activation of Wnt/ß-catenin pathway, which is an essential event for HSC activation.

Hesperitin derivative-11 suppress hepatic stellate cell activation and proliferation by targeting PTEN/AKT pathway.

Hesperitin derivative (HD-11) is a monomeric compound derived from Hesperidin, which is a naturally occurring flavanone glycoside that exerts extensive clinical effects such as anti-inflammatory, anti-oxidant and anti-angiogenic. However, the role and fundamental mechanism of HD-11 in hepatic fibrosis are still unrevealed. In this study, HD-11 not only alleviates ECM deposition in rats with liver fibrosis, but also reduces the expression of α-SMA and col1a1 in TGF-ß1-induced HSC-T6 cells. Moreover, it was demonstrated that HD-11 significantly promoted the expression of PTEN in vivo and in vitro. In order to evaluate the involvement of HD-11 in TGF-ß1-induced HSC-T6 activation, a specific blocking agent of PTEN (bpv) and PTEN small interfering (si)-RNA-mediated silencing were used. Interestingly, HD-11 treatment couldn't inhibit α-SMA and col1a1 expression on the basis of PTEN knockdown. On the contrary, over-expression of PTEN had an opposite effect on the expression of α-SMA and col1a1 in TGF-ß1-induced HSC-T6 cells after treatment of HD-11. In addition, HD-11 remarkably inhibited the expression of p-AKT in vivo and in vitro. Taken together, all the above results indicate that HD-11 may play the part of an effective modulator of PTEN/AKT signaling pathway.

Role of histone deacetylases(HDACs) in progression and reversal of liver fibrosis.

Liver fibrosis refers to a reversible wound healing process response to chronic liver injuries. Activation of hepatic stellate cells (HSCs) is closely correlated with the development of liver fibrosis. Histone deacetylases(HDACs) determine the acetylation levels of core histones to modulate expression of genes. To demonstrate the link between HDACs and liver fibrosis, CCl4-induced mouse liver fibrosis model and its spontaneous reversal model were established. Results of the current study demonstrated that deregulation of liver HDACs may involved in the development of liver fibrosis. Among 11 HDACs tested in our study (Class I, II, and IV HDACs), expression of HDAC2 was maximally increased in CCl4-induced fibrotic livers but decreased after spontaneous recovery. Moreover, expression of HDAC2 was elevated in human liver fibrotic tissues. In this regard, the potential role of HDAC2 in liver fibrosis was further evaluated. Our results showed that administration of HSC-T6 cells with transforming growth factor-beta1 (TGF-ß1) resulted in an increase of HDAC2 protein expression in dose- and time-dependent manners. Moreover, HDAC2 deficiency inhibited HSC-T6 cell proliferation and activation induced by TGF-ß1. More importantly, the present study showed HDAC2 may regulate HSCs activation by suppressing expression of Smad7, which is a negative modulator in HSCs activation and liver fibrosis. Collectively, these observations revealed that HDAC2 may play a pivotal role in HSCs activation and liver fibrosis while deregulation of HDACs may serve as a novel mechanism underlying liver fibrosis.

MicroRNA-20a negatively regulates expression of NLRP3-inflammasome by targeting TXNIP in adjuvant-induced arthritis fibroblast-like synoviocytes.

OBJECTIVES: Rheumatoid arthritis (RA) is a heterogenic and systemic autoimmune disease characterized by synovitis and joint structural damage. However, the pathogenesis of RA is still obscure. It has been reported microRNA-20a (miRNA-20a) was significantly associated with the regulation of pro-inflammatory cytokines release in RA FLS. The purpose of this study was to explore the function and underlying mechanisms of miRNA-20a on NLRP3-inflammasome in adjuvant-induced arthritis (AA) fibroblast-like synoviocytes (FLSs) in vitro. METHODS: In this study, using a combination of Western blotting, Q-PCR, and ELISA analysis, we investigated the influence and function of miRNA-20a on NLRP3-inflammasome by targeting TXNIP in AA FLSs. RESULTS: In the present study, the expression of NLRP3-inflammasome was significant up-regulated in AA model in vitro. Our study indicated that silence of NLRP3 down-regulated the expression of NLRP3-inflammasome and the secretion of IL-1ß and MMP-1. Moreover, over-expression of miR-20a decreased formation of NLRP3-inflammasome, including NLRP3, ASC and caspase-1, and suppressed the secretion of IL-1ß and MMP-1, along with down-regulated the expressions of TXNIP in primary FLSs isolated from AA. With the combined use of prediction programs and luciferase assay, the rat TXNIP mRNA 3'UTR predicted to be targeted by miR-20a. Similarly, inhibitor TXNIP expression by TXNIP-siRNA markedly repressed formation of NLRP3-inflammasome and the secretion of IL-1ß and MMP-1. CONCLUSION: Taken together, these results indicate that miR-20a may play a pivotal role in the NLRP3-inflammasome by targeted inhibit TXNIP expression in AA FLSs.

Telomerase reverse transcriptase acts in a feedback loop with NF-κB pathway to regulate macrophage polarization in alcoholic liver disease.

Activation of Kupffer cells (KCs) plays a central role in the pathogenesis of alcoholic liver disease (ALD). C57BL/6 mice fed EtOH-containing diet showed a mixed induction of hepatic classical (M1) and alternative (M2) macrophage markers. Since telomerase activation occurs at critical stages of myeloid and lymphoid cell activation, we herein investigated the role of telomerase reverse transcriptase (TERT), the determining factor of telomerase, in macrophage activation during ALD. In our study, TERT expression and telomerase activity (TA) were remarkably increased in liver tissue of EtOH-fed mice. Moreover, EtOH significantly up-regulated TERT in isolated KCs and RAW 264.7 cells and LPS induced TERT production in vitro. These data indicate that up-regulation of TERT may play a critical role in macrophages during ALD. Furthermore, loss- and gain-of-function studies suggested that TERT switched macrophages towards M1 phenotype by regulating NF-κB signaling, but had limited effect on M2 macrophages polarization in vitro. Additionally, PDTC, a chemical inhibitor of NF-κB, could dramatically down-regulate TERT expression and the hallmarks of M1 macrophages. Therefore, our study unveils the role of TERT in macrophage polarization and the cross-talk between TERT and p65, which may provide a possible explanation for the ethanol-mediated hepatic proinflammatory response and M1 macrophage polarization.

PTP1B confers liver fibrosis by regulating the activation of hepatic stellate cells.

Liver fibrosis is a reversible wound-healing response to chronic hepatic injuries. Activation of hepatic stellate cells (HSCs) plays a pivotal role in the development of hepatic fibrosis. The currently accepted mechanism for the resolution of liver fibrosis is the apoptosis and inactivation of activated HSCs. Protein tyrosine phosphatase 1B (PTP1B), a prototype of non-receptor protein tyrosine phosphatase, is proved to be a vital modulator in cardiac fibrogenesis. However, the precise role of PTP1B on liver fibrosis and HSC activation is still unclear. Our study showed that the expression of PTP1B was elevated in fibrotic liver but reduced after spontaneous recovery. Moreover, stimulation of HSC-T6 cells with transforming growth factor-ß1 (TGF-ß1) resulted in a dose/time-dependent increase of PTP1B mRNA and protein. Co-incubation of HSC-T6 cells with PTP1B-siRNA inhibited the cell proliferation and activation induced by TGF-ß1. Additionally, both mRNA and protein of PTP1B were dramatically decreased in inactivated HSCs after treated with adipogenic differentiation mixture (MDI). Over-expression of PTP1B hindered the inactivation of HSC-T6 cells induced by MDI. These observations revealed a regulatory role of PTP1B in liver fibrosis and implied PTP1B as a potential therapeutic target.

Hyperin attenuates inflammation by activating PPAR-γ in mice with acute liver injury (ALI) and LPS-induced RAW264.7 cells.

Hyperin (HP) is a flavonoid compound found in various plants like Ericaceae, Guttifera and Celastraceae. The present study has revealed that HP has a variety of pharmacological effects including anti-oxidant, anticancer, and anti-coagulant, especially anti-inflammatory. However, the potential molecular mechanism of anti-inflammatory is still unrevealed. In this study, HP not only significantly attenuated inflammation in C57BL/6J mice with acute liver injury (ALI), but also reduced the expression of TNF-α and IL-6 in lipopolysaccharide (LPS)-induced RAW264.7 cells. Furthermore, our findings showed that HP remarkably induced the expression of PPAR-γ in vivo and in vitro. Interestingly, compared with the HP treatment group, a specific blocking agent of PPAR-γ T0070907 and PPAR-γ small interfering (si)-RNA-mediated silencing in RAW264.7 cells were used to evaluate the involvement of HP in alleviating LPS-induced inflammation. More importantly, over-expression of PPAR-γ had an opposite effect on the expression of TNF-α and IL-6 in LPS-induced RAW264.7 cells after treatment with HP. In addition, HP remarkably inhibited the expression of P-ERK1/2 and P-P38 MAPK. Taken together, all the above results indicate that HP may serve as an effective modulator of PPAR-γ, further down-regulating ERK1/2 and p38 MAPK during the pathogenesis of inflammation.

Geniposide alleviates inflammation by suppressing MeCP2 in mice with carbon tetrachloride-induced acute liver injury and LPS-treated THP-1 cells.

Geniposide (GP), an iridoid glucoside extracted from Gardenia jasminoides Ellis fruits, has been used as a herbal medicine to treat liver and gall bladder disorders for many years. However the mechanism of anti-inflammatory is largely unknown. In this study, GP significantly attenuated inflammation in acute liver injury (ALI) mice model and in lipopolysaccharide (LPS)-induced THP-1 cells. It was demonstrated that GP obviously decreased the expression of Methyl-CpG binding protein 2 (MeCP2) in vivo and in vitro. Knockdown of MeCP2 with siRNA suppressed the expressions of IL-6 and TNF-α, while over-expression of MeCP2 had a proinflammatory effect on the expression of IL-6 and TNF-α in LPS-induced THP-1 cells. Mechanistically, it was indicated that GP had anti-inflammatory effects at least in part, through suppressing MeCP2. Interestingly, GP could attenuate expressions of Sonic hedgehog (Shh) and GLIS family zinc finger 1 (GLIS1) but increase Ptched1 (PTCH1) expression. Similar findings were also demonstrated at the protein level by siRNA MeCP2. Furthermore, over-expression of MeCP2 obviously increased Shh and GLIS1 expressions but reduced PTCH1 expression. Taken together, GP may serve as an effective modulator of MeCP2-hedgehog pathway (Hh)-axis during the pathogenesis of inflammation. Our findings shed light on the potential therapeutic feature of GP in recovering inflammatory diseases.