Metformin induces mitochondrial fission and reduces energy metabolism by targeting respiratory chain complex I in hepatic stellate cells to reverse liver fibrosis.

The activation and proliferation of hepatic stellate cells (HSCs) are critical processes for the treatment of liver fibrosis. It is necessary to identify effective drugs for the treatment of liver fibrosis and elucidate their mechanisms of action. Metformin can inhibit HSCs; however, no systematic studies demonstrating the effects of metformin on mitochondria in HSCs have been reported. This study demonstrated that metformin induces mitochondrial fission by phosphorylating AMPK/DRP1 (S616) in HSCs to decrease the expression of α-SMA and collagen. Additionally, metformin repressed the total ATP production rate, especially the production rate of ATP produced through mitochondrial oxidative phosphorylation, by inhibiting the enzymatic activity of complex I. Further analysis revealed that metformin strongly constrained the transcription of mitochondrial genes (ND1-ND6 and ND4L) that encode the core subunits of respiratory chain I. Upregulation of the mRNA expression of HK2 and GLUT1 slightly enhanced glycolysis. Additionally, metformin increased mitochondrial DNA (mtDNA) copy number to suppress the proliferation and activation of HSCs, indicating that mtDNA copy number can alter the fate of HSCs. In conclusion, metformin can induce mitochondrial fragmentation and low-level energy metabolism in HSCs, thereby suppressing HSCs activation and proliferation to reverse liver fibrosis.

Targeted lipidomics analysis of lysine 179 acetylation of ACSF2 in rat hepatic stellate cells.

Activation of hepatic stellate cells (HSCs) is generally recognized as a central driver of liver fibrosis. Metabolism of fatty acids (FA) plays a critical role in the activation of HSCs. Proteomics analysis on lysine acetylation of proteins in activated HSCs in our previous study indicated that acetylation of the lysine residues on ACSF2 is one of the most significantly upregulated sites in activated-HSCs and K179 is its important acetylation site. However, the role of acetylation at K179 of ACSF2 on activation of HSCs and free fatty acids (FFA) metabolism remains largely unknown. The reported study demonstrates that acetylation at K179 of ACSF2 promoted HSCs activation. The targeted lipidomic analysis indicated K179 acetylation of ACSF2 mainly affected long chain fatty acids (LCFA) metabolism, especially oleic acid, elaidic acid and palmitoleic acid. And the liquid chromatography mass spectrometry (LC-MS) analysis further demonstrated the formation of many long-chain acyl-CoAs were catalyzed by acetylation at K179 of ACSF2 including oleic acid, elaidic acid and palmitoleic acid. In conclusion, this study indicated that ACSF2 may be a potential therapeutic targets by regulating the metabolism of LCFA for liver fibrosis.

Mitigation of liver fibrosis via hepatic stellate cells mitochondrial apoptosis induced by metformin.

Liver fibrosis, a disease characterized by the excessive accumulation of extracellular matrix originating from activated hepatic stellate cells (HSCs), is a common pathological response to chronic liver injury resulting from a variety of insults. However, drugs that effectively block the activation of HSCs have still not been adequately investigated. This study demonstrates that metformin decreased the number of activated-HSCs through induction of apoptosis, but did not impact numbers of hepatocytes. Metformin upregulated BAX activation with facilitation of BIM, BAD and PUMA; downregulated Bcl-2 and Bcl-xl, but did not affect Mcl-1. Additionally, metformin induced cytochrome c release from mitochondria into the cytoplasm, directly triggering caspase-9-mediated mitochondrial apoptosis. The decline in mitochondrial membrane potential (ΔΨm) and deposition of superoxide in mitochondria accelerated the destruction of the integrity of mitochondrial membrane. Moreover, we verified the therapeutic effect of metformin in our mouse model of liver fibrosis associated with nonalcoholic steatohepatitis (NASH) in which hepatic function, NASH lesions and fibrosis were improved by metformin. In conclusion, this study indicated that metformin has significant therapeutic value in NASH-derived liver fibrosis by inducing apoptosis in HSCs, but does not affect the proliferation of hepatocytes.

C/EBP-α induces autophagy by binding to Beclin1 through its own acetylation modification in activated hepatic stellate cells.

The activation of hepatic stellate cells (HSCs) plays a key role in the occurrence of liver fibrosis，and promoting the apoptosis of activated HSCs or reducing the number of activated HSCs can reverse the development of liver fibrosis. In our previous studies, we have demonstrated that the CCAAT/enhancer binding protein α (C/EBP-α) played an important role in promoting the apoptosis of activated HSCs, thereby exerting an anti-liver fibrosis effect. Unlike apoptosis, autophagy, as a caspase-independent programmed cell death, can promptly remove the abnormal accumulation of substances or damaged organelles in cells and play a key role in regulating the homeostasis of intracellular environment. However, it is still unclear whether C/EBP-α participates in the occurrence of autophagy in HSCs. Therefore, in this study, we firstly used the methods of Western blot and immunofluorescence to characterize the consequence of C/EBP-α overexpression on the expression of proteins LC3B, P62, ATG5 and Beclin1 which were related to autophagy in HSCs. Subsequently, we performed Western blot and site-directed mutagenesis methods to clarify the type and related mechanism of autophagy which was induced by C/EBP-α. Here we show that C/EBP-α promotes the occurrence of autophagy in HSCs and the autophagy induced by C/EBP-α belongs to mitophagy. The stability of C/EBP-α protein regulates the level of autophagy in HSCs. In addition, acetylation of C/EBP-α also regulates the occurrence of autophagy in HSCs. Acetylation of lysine at positions K298, K302 and K326 of C/EBP-α promotes its binding to Beclin1. In conclusion, our study uncovers the role of C/EBP-α in regulating autophagy in HSCs, thereby providing a new strategy for clinical treatment of liver fibrosis.

OGT regulated O-GlcNAcylation promotes papillary thyroid cancer malignancy via activating YAP.

The incidence of thyroid cancer is growing rapidly during the past decades worldwide. Although most thyroid tumors are curable, some patients diagnosed with distant metastases are associated with poor prognosis. The molecular mechanisms underlying these cases are still largely unknown. Here we found that the upregulated O-Linked N-Acetylglucosamine Transferase (OGT) expression and O-GlcNAcylation (O-GlcNAc) modification in papillary thyroid cancer (PTC) were essential in tumor growth and metastasis. Mass spectrometry analysis showed that YAP was the effector protein modified by OGT. In details, YAP Ser109 O-GlcNAcylation promoted the malignant phenotypes in PTC cells by inducing YAP Ser127 dephosphorylation and activation. Our work clearly showed the critical role of OGT and YAP played in PTC tumors and made it possible for us to seek the clinical potential of manipulating OGT/YAP activity in PTC targeted therapies. These findings also confirmed OGT worked in collaboration with classical Hippo pathway kinases as an upstream regulator of YAP in PTC tumors.

ADAM10 is involved in the oncogenic process and chemo-resistance of triple-negative breast cancer via regulating Notch1 signaling pathway, CD44 and PrPc.

BACKGROUND: Triple-negative breast cancer (TNBC) is the most challenging breast cancer subtype to treat, because it is so aggressive with shorter survival. Chemotherapy remains the standard treatment due to the lack of specific and effective molecular targets. The aim of the present study is to investigate the potential roles of A Disintegrin and Metalloproteinase 10 (ADAM10) on TNBC cells and the effects of combining ADAM10 expression and neoadjuvant chemotherapy treatment (NACT) to improve the overall survival in breast cancer patients. METHODS: Using a series of breast cancer cell lines, we measured the expression of ADAM10 and its substrates by quantitative real-time PCR assay (qRT-PCR) and western blot analysis. Cell migration and invasion, cell proliferation, drug sensitivity assay, cell cycle and apoptosis were conducted in MDA-MB-231 cells cultured with ADAM10 siRNA. The effect of ADAM10 down-regulation by siRNA on its substrates was assessed by western blot analysis. We performed immunohistochemical staining for ADAM10 in clinical breast cancer tissues in 94 patients receiving NACT. RESULTS: The active form of ADAM10 was highly expressed in TNBC cell lines. Knockdown of ADAM10 in MDA-MB-231 cells led to a significant decrease in cell proliferation, migration, invasion and the IC50 value of paclitaxel and adriamycin, while induced cell cycle arrest and apoptosis. And these changes were correlated with down-regulation of Notch signaling, CD44 and cellular prion protein (PrPc). In clinical breast cancer cases, a high ADAM10 expression in pre-NACT samples was strongly associated with poorer response to NACT and shorter overall survival. CONCLUSIONS: These data suggest the previously unrecognized roles of ADAM10 in contributing to the progression and chemo-resistance of TNBC.

RACGAP1 modulates ECT2-Dependent mitochondrial quality control to drive breast cancer metastasis.

Most cancer deaths are due to the colonization of tumor cells in distant organs. More evidence indicates that overexpression of RACGAP1 plays a critical role in cancer metastasis. However, the underlying mechanism still remains poorly understood. Here we found that RACGAP1 promoted breast cancer metastasis through regulating mitochondrial quality control. Overexpression of RACGAP1 in breast cancer cells led to the fragmentation of mitochondria, increased mitophagy intensity, mitochondrial turnover, and aerobic glycolysis ATP production. We showed that RACGAP1 promoted mitochondrial fission through recruiting ECT2 during anaphase and subsequently had activated ERK-DRP1 pathway. We further demonstrated the phosphorylation of RACGAP1 is essential for its ability of binding with ECT2 and its downstream effects. RACGAP1 overexpression also increased the expression of PGC-1a, a key mitochondrial biogenesis regulator, presumably by the increased mitophagy intensity induced by RACGAP1. PGC-1a increased the enrichment of DNMT1 in mitochondria, mitochondrial DNMT1 augmented mitochondrial DNA methylation and upregulated mitochondrial genome transcription. Our data indicated that RACGAP1 simultaneously facilitated mitophagy and mitochondrial biogenesis through regulating DRP1 phosphorylation and PGC-1a expression, eventually improved mitochondrial quality control in breast cancer cells. Our study provided a new angle in understanding the RACGAP1-overexpression related malignancy in breast cancer patients.

Long non-coding RNA RACGAP1P promotes breast cancer invasion and metastasis via miR-345-5p/RACGAP1-mediated mitochondrial fission.

Long non-coding RNAs (lncRNAs) are emerging as key molecules in various cancers, yet their potential roles in the pathogenesis of breast cancer are not fully understood. Herein, using microarray analysis, we revealed that the lncRNA RACGAP1P, the pseudogene of Rac GTPase activating protein 1 (RACGAP1), was up-regulated in breast cancer tissues. Its high expression was confirmed in 25 pairs of breast cancer tissues and 8 breast cell lines by qRT-PCR. Subsequently, we found that RACGAP1P expression was positively correlated with lymph node metastasis, distant metastasis, TNM stage, and shorter survival time in 102 breast cancer patients. Then, in vitro and in vivo experiments were designed to investigate the biological function and regulatory mechanism of RACGAP1P in breast cancer cell lines. Overexpression of RACGAP1P in MDA-MB-231 and MCF7 breast cell lines increased their invasive ability and enhanced their mitochondrial fission. Conversely, inhibition of mitochondrial fission by Mdivi-1 could reduce the invasive ability of RACGAP1P-overexpressing cell lines. Furthermore, the promotion of mitochondrial fission by RACGAP1P depended on its competitive binding with miR-345-5p against its parental gene RACGAP1, leading to the activation of dynamin-related protein 1 (Drp1). In conclusion, lncRNA RACGAP1P promotes breast cancer invasion and metastasis via miR-345-5p/RACGAP1 pathway-mediated mitochondrial fission.

SETDB1 induces epithelial­mesenchymal transition in breast carcinoma by directly binding with Snail promoter.

SET domain bifurcated 1 (SETDB1) is a histone H3 lysine 9 methyltransferase that is highly expressed in various tumor types, including breast cancer. However, how SETDB1 functions in breast cancer is unclear. In the present study, proliferation, migration and invasion assays were performed to explore the role of SETDB1 in breast cancer cells. SETDB1 downregulation in BT549 and MDA­MB­231 cells reduced cell proliferation, whereas upregulation in MCF7 and T47D cells enhanced proliferation. Depletion of SETDB1 suppressed cell migration and invasion in vitro and reduced lung metastasis in vivo. By contrast, SETDB1 overexpression enhanced cell migration and invasiveness. Notably, SETDB1 overexpression appeared to induce epithelial­mesenchymal transition (EMT) in MCF7 cells. Mechanistic investigations indicated that SETDB1 acts as an EMT inducer by binding directly to the promoter of the transcription factor Snail. Thus, SETDB1 is involved in breast cancer metastasis and may be a therapeutic target for treating patients with breast cancer.

Trichostatin A inhibits the activation of Hepatic stellate cells by Increasing C/EBP-α Acetylation in vivo and in vitro.

Reversal of activated hepatic stellate cells (HSCs) to a quiescent state and apoptosis of activated HSCs are key elements in the reversion of hepatic fibrosis. CCAAT/enhancer binding protein α (C/EBP-α) has been shown to inhibit HSC activation and promote its apoptosis. This study aims to investigate how C/EBP-α acetylation affects the fate of activated HSCs. Effects of a histone deacetylation inhibitor trichostatin A (TSA) on HSC activation were evaluated in a mouse model of liver fibrosis caused by carbon tetrachloride (CCl4) intoxication. TSA was found to ameliorate CCl4-induced hepatic fibrosis and improve liver function through increasing the protein level and enhancing C/EBP-α acetylation in the mouse liver. C/EBP-α acetylation was determined in HSC lines in the presence or absence of TSA, and the lysine residue K276 was identified as a main acetylation site in C/EBP-α protein. C/EBP-α acetylation increased its stability and protein level, and inhibited HSC activation. The present study demonstrated that C/EBP-α acetylation increases the protein level by inhibiting its ubiquitination-mediated degradation, and may be involved in the fate of activated HSCs. Use of TSA may confer an option in minimizing hepatic fibrosis by suppressing HSC activation, a key process in the initiation and progression of hepatic fibrosis.

TSA increases C/EBP­α expression by increasing its lysine acetylation in hepatic stellate cells.

CCAAT enhancer binding protein­α (C/EBP­α) is a transcription factor expressed only in certain tissues, including the liver. It has been previously demonstrated that C/EBP­α may induce apoptosis in hepatic stellate cells (HSCs), raising the question of whether acetylation of C/EBP­α is associated with HSCs, and the potential associated mechanism. A total of three histone deacetylase inhibitors (HDACIs), including trichostatin A (TSA), suberoylanilide hydroxamic acid and nicotinamide, were selected to determine whether acetylation affects C/EBP­α expression. A Cell Counting Kit­8 assay was used to determine the rate of proliferation inhibition following treatment with varying doses of the three HDACIs in HSC­T6 and BRL­3A cells. Western blot analysis was used to examine Caspase­3, ­8, ­9, and ­12 levels in HSC­T6 cells treated with adenoviral­C/EBP­α and/or TSA. Following treatment with TSA, a combination of reverse transcription­quantitative polymerase chain reaction and western blot analyses was used to determine the inherent C/EBP­α mRNA and protein levels in HSC­T6 cells at 0, 1, 2, 4, 8, 12, 24, 36 and 48 h. Nuclear and cytoplasmic proteins were extracted to examine C/EBP­α distribution. Co­immunoprecipitation analysis was used to examine the lysine acetylation of C/EBP­α. It was observed that TSA inhibited the proliferation of HSC­T6 cells to a greater extent compared with BRL­3A cells, following treatment with the three HDACIs. TSA induced apoptosis in HSC­T6 cells and enhanced the expression of C/EBP­α. Following treatment of HSC­T6 cells with TSA, inherent C/EBP­α expression increased in a time­dependent manner, and its lysine acetylation simultaneously increased. Therefore, the results of the present study suggested that TSA may increase C/EBP­α expression by increasing its lysine acetylation in HSCs.

HCRP1 inhibits TGF-ß induced epithelial-mesenchymal transition in hepatocellular carcinoma.

Hepatocellular carcinoma-related protein 1 (HCRP1), also known as human vacuolar protein sorting 37 homologue A (hVps37A), has not been detected or is significantly downregulated in hepatocellular carcinoma (HCC) tissues. However, information on the regulatory mechanisms of HCRP1 in HCC remains unclear. Here we found that the downregulation of HCRP1 in HepG2 cells (with low invasion capacity) significantly enhanced migration and invasion, whereas HCRP1 upregulation in SMMC-7721 cells (with high invasion capacity) generated the opposite result. Interestingly, the morphology of HepG2 cells significantly changed from an epithelial to mesenchymal phenotype after HCRP1 knockdown. Moreover, we observed a decrease in the expression of epithelial cell markers E-cadherin and ß-catenin, and an increase in the expression of mesenchymal cell markers N-cadherin and vimentin. We also observed that the downregulation of HCRP1 induced epithelial-mesenchymal transition (EMT) through the transforming growth factor-ß pathway. Together, our findings define a novel function for HCRP1 from the perspective of EMT, which is closely associated with the migration and invasion of HCC cells.

Decreased HCRP1 promotes breast cancer metastasis by enhancing EGFR phosphorylation.

Previous study showed that hepatocellular carcinoma related protein 1 (HCRP1) is decreased in breast cancer. HCRP1 expression is inversely related to epithelial growth factor receptor (EGFR) in breast cancer tissues, and patients with breast cancer expressing lower HCRP1 tended to suffer a shorter life expectancy. However, the detailed biological functions of HCRP1 in breast cancer as well as the interaction between HCRP1 and EGFR remain unexplored. In this study, we examined HCRP1 expression in breast cancer tissues and cell lines by western blot. Thereafter, we performed transwell migration and matrigel invasion assays after siRNA interference and lentiviral vector of HCRP1 infection. To further investigate the interaction between HCRP1 downregulation and EGFR signaling pathway, we evaluated the phosphorylation status of EGFR, Erk1/2 and Akt by western blot following HCRP1-siRNA transfection. Moreover, we investigated the in vivo functions of HCRP1 using a breast cancer xenograft model. We found that HCRP1 depletion significantly promoted breast cancer migration and invasion while HCRP1 overexpression produced an opposite effect. In addition, HCRP1 depletion decreased EGFR degradation and enhanced phosphorylation of EGFR. Interestingly, HCRP1 depletion also led to insensitivity to EGFR inhibitors treatment. The in vivo experiment confirmed the metastasis inhibition function of HCRP1. The present data indicate that HCRP1 inhibits breast cancer metastasis through downregulating EGFR phosphorylation.