Aberrant upregulation of 14-3-3σ and EZH2 expression serves as an inferior prognostic biomarker for hepatocellular carcinoma

Establishment and Validation of a Four-stress Granule-related Gene Signature in Hepatocellular Carcinoma

Background and Aims

Stress granules (SGs) as membrane-less cytoplasmic foci formed in response to unfavorable external stimuli could promote cancer cells to adapt to hostile environments. Hepatocellular carcinoma (HCC) is prone to be highly aggressive once diagnosed, which markedly reduces patient survival time. Therefore, it is crucial to develop valid diagnostic markers to prognosticate HCC patient prognosis, which promotes individualized precision therapeutics in HCC. Considering the pro-tumorigenic activity of SGs, it is of great potential value to construct a prognostic tool for HCC based on the expression profiles of SG-related genes (SGGs).

Methods

Bioinformatic analysis was employed to establish an SGG-based prognostic signature. Western blotting and real-time polymerase chain reaction assays were used to assess the expression patterns of the related SGGs. Loss-of-function experiments were performed to analyze the effect of the SGGs on SG formation and cell survival.

Results

A four-SGG signature (KPNA2, MEX3A, WDR62, and SFN) targeting HCC was established and validated to exhibit a robust performance in predicting HCC prognosis. Consistently, all four genes were further found to be highly expressed in human HCC tissues. More important, we demonstrated that individually knocking down the four SGGs significantly reduced HCC cell proliferation and metastasis by compromising the SG formation process.

Conclusions

We developed an SGG-based predictive signature that can be used as an independent prognostic tool for HCC. The strong predictive power of this signature was further elucidated by the carcinogenic activity of KPNA2, MEX3A, WDR62, and SFN in HCC cells by regulating SG formation.

Mechanism Research and Application for Ginsenosides in the Treatment of Hepatocellular Carcinoma

Ginsenosides, the main active pharmacological ingredients of ginseng, have been widely used for the treatment of numerous carcinomas. Hepatocellular carcinoma (HCC) is 3rd leading malignant tumor in terms of mortality worldwide. Accumulating evidence indicates that ginsenosides play a vital role in the prevention and treatment of HCC. Ginsenosides can significantly improve the symptoms of HCC, and their anticancer activity is mainly involved in inhibiting proliferation and migration, inducing cell cycle arrest at the G0/G1 phase, promoting caspase-3 and 8-mediated apoptosis, regulating autophagy related to Atg5, Atg7, Atg12, LC3-II, and PI3K/Akt pathways, and lowering invasion and metastasis associated with decreased nuclear translocation of NF-κB p65 and MMP-2/9, increasing IL-2 and IFN-γ levels to enhance immune function, as well as regulating the gut-liver axis. In addition, ginsenosides can be used as an adjuvant to conventional cancer therapies, enhancing sensitivity to chemotherapy drugs, and improving efficacy and/or reducing adverse reactions through synergistic effects. Therefore, the current manuscript discusses the mechanism and application of ginsenosides in HCC. It is hoped to provide theoretical basis for the treatment of HCC with ginsenosides.

Stratifin Promotes Hepatocellular Carcinoma Progression by Modulating the Wnt/β-Catenin Pathway

Abnormal stratifin (SFN) expression is closely related to the progression of several human cancers, but the potential roles of SFN in hepatocellular carcinoma (HCC) remain largely unknown. In this study, we found that SFN was upregulated in HCC cell lines and tissues and was positively associated with tumor size, poor differentiation, Tumor Node Metastasis (TNM) stage, and vascular invasion. In addition, high expression levels of SFN were associated with poor overall survival and disease-free survival. Biologically, downregulation of SFN suppressed tumor cell proliferation, epithelial-mesenchymal transition (EMT), invasion, and migration in vitro and tumor growth in vivo. However, overexpression of SFN promoted cell proliferation, EMT, invasion, and migration in vitro and tumor growth in vivo. Mechanistically, overexpression of SFN activated the Wnt/β-catenin pathway by promoting Glycogen synthase kinase-3 beta (GSK-3β) phosphorylation, decreasing β-catenin phosphorylation, promoting β-catenin transport into the nucleus, and enhancing the expression of c-Myc, whereas depletion of SFN inhibited the Wnt/β-catenin pathway. In addition, TOPFlash/FOPFlash reporter assays showed that overexpression or downregulation of SFN obviously increased or decreased, respectively, the activity of the Wnt/β-catenin pathway. Our results indicated that SFN plays an important role in HCC, possibly providing a prognostic factor and therapeutic target for HCC.

The Pivotal Immunomodulatory and Anti-Inflammatory Effect of Histone-Lysine N-Methyltransferase in the Glioma Microenvironment: Its Biomarker and Therapy Potentials

Enhancer of zeste homolog 2 (EZH2) is a histone-lysine N-methyltransferase that encrypts a member of the Polycomb group (PcG) family. EZH2 forms a repressive chromatin structure which eventually participates in regulating the development as well as lineage propagation of stem cells and glioma progression. Posttranslational modifications are distinct approaches for the adjusted modification of EZH2 in the development of cancer. The amino acid succession of EZH2 protein makes it appropriate for covalent modifications, like phosphorylation, acetylation, O-GlcNAcylation, methylation, ubiquitination, and sumoylation. The glioma microenvironment is a dynamic component that comprises, besides glioma cells and glioma stem cells, a complex network that comprises diverse cell types like endothelial cells, astrocytes, and microglia as well as stromal components, soluble factors, and the extracellular membrane. EZH2 is well recognized as an essential modulator of cell invasion as well as metastasis in glioma. EZH2 oversecretion was implicated in the malfunction of several fundamental signaling pathways like Wnt/β-catenin signaling, Ras and NF-κB signaling, PI3K/AKT signaling, β-adrenergic receptor signaling, and bone morphogenetic protein as well as NOTCH signaling pathways. EZH2 was more secreted in glioblastoma multiforme than in low-grade gliomas as well as extremely secreted in U251 and U87 human glioma cells. Thus, the blockade of EZH2 expression in glioma could be of therapeutic value for patients with glioma. The suppression of EZH2 gene secretion was capable of reversing temozolomide resistance in patients with glioma. EZH2 is a promising therapeutic as well as prognostic biomarker for the treatment of glioma.

Significance of stratifin in early progression of lung adenocarcinoma and its potential therapeutic relevance

Lung cancer is the most common cause of global cancer-related mortality, and the main histological type is adenocarcinoma, accounting for 50% of non-small cell lung cancer. In 2015, the World Health Organization (WHO) histological classification defined the concepts of "adenocarcinoma in situ" (AIS) and "minimally invasive adenocarcinoma" (MIA), which are considered to be adenocarcinomas at a very early stage. Although AIS and MIA have a very favorable outcome, once they progress to early but invasive adenocarcinoma (eIA), they can sometimes have a fatal outcome. We previously compared the expression profiles of eIA and AIS, and identified stratifin (SFN; 14-3-3 sigma) as a protein showing significantly higher expression in eIA than in AIS. Expression of SFN is controlled epigenetically by DNA demethylation, and its overexpression is significantly correlated with poorer outcome. In vitro and in vivo analyses have shown that SFN facilitates early progression of adenocarcinoma by enhancing cell proliferation. This review summarizes genetic and epigenetic abnormalities that can occur in early-stage lung adenocarcinoma and introduces recent findings regarding the biological significance of SFN overexpression during the course of lung adenocarcinoma progression. Therapeutic strategies for targeting SFN are also discussed.

The 14-3-3σ protein promotes HCC anoikis resistance by inhibiting EGFR degradation and thereby activating the EGFR-dependent ERK1/2 signaling pathway

Resistance to anoikis, cell death due to matrix detachment, is acquired during tumor progression. The 14-3-3σ protein is implicated in the development of chemo- and radiation resistance, indicating a poor prognosis in multiple human cancers. However, its function in anoikis resistance and metastasis in hepatocellular carcinoma (HCC) is currently unknown. Methods: Protein expression levels of 14-3-3σ were measured in paired HCC and normal tissue samples using western blot and immunohistochemical (IHC) staining. Statistical analysis was performed to evaluate the clinical correlation between 14-3-3σ expression, clinicopathological features, and overall survival. Artificial modulation of 14-3-3σ (downregulation and overexpression) was performed to explore the role of 14-3-3σ in HCC anoikis resistance and tumor metastasis in vitro and in vivo. Association of 14-3-3σ with epidermal growth factor receptor (EGFR) was assayed by co-immunoprecipitation. Effects of ectopic 14-3-3σ expression or knockdown on EGFR signaling, ligand-induced EGFR degradation and ubiquitination were examined using immunoblotting and co-immunoprecipitation, immunofluorescence staining, and flow cytometry analysis. The levels of EGFR ubiquitination, the interaction between EGFR and 14-3-3σ, and the association of EGFR with c-Cbl after EGF stimulation, in 14-3-3σ overexpressing or knockdown cells were examined to elucidate the mechanism by which 14-3-3σ inhibits EGFR degradation. Using gain-of-function or loss-of-function strategies, we further investigated the role of the EGFR signaling pathway and its downstream target machinery in 14-3-3σ-mediated anoikis resistance of HCC cells. Results: We demonstrated that 14-3-3σ was upregulated in HCC tissues, whereby its overexpression was correlated with aggressive clinicopathological features and a poor prognosis. In vitro and in vivo experiments indicated that 14-3-3σ promoted anoikis resistance and metastasis of HCC cells. Mechanistically, we show that 14-3-3σ can interact with EGFR and significantly inhibit EGF-induced degradation of EGFR, stabilizing the activated receptor, and therefore prolong the activation of EGFR signaling. We demonstrated that 14-3-3σ downregulated ligand-induced EGFR degradation by inhibiting EGFR-c-Cbl association and subsequent c-Cbl-mediated EGFR ubiquitination. We further verified that activation of the ERK1/2 pathway was responsible for 14-3-3σ-mediated anoikis resistance of HCC cells. Moreover, EGFR inactivation could reverse the 14-3-3σ-mediated effects on ERK1/2 phosphorylation and anoikis resistance. Expression of 14-3-3σ and EGFR were found to be positively correlated in human HCC tissues. Conclusions: Our results indicate that 14-3-3σ plays a pivotal role in the anoikis resistance and metastasis of HCC cells, presumably by inhibiting EGFR degradation and regulating the activation of the EGFR-dependent ERK1/2 pathway. To our best knowledge, this is the first report of the role of 14-3-3σ in the anoikis resistance of HCC cells, offering new research directions for the treatment of metastatic cancer by targeting 14-3-3σ.

The 14-3-3η/GSK-3β/β-catenin complex regulates EndMT induced by 27-hydroxycholesterol in HUVECs and promotes the migration of breast cancer cells

Endothelial-mesenchymal transition (EndMT) is the transformation of endothelial cell morphology to mesenchymal cell morphology, accompanied by decline of endothelial function and enhancement of mesenchymal function, which promotes tumor progression and tumor cell invasion and metastasis. 27-Hydroxycholesterol (27-HC) is a cholesterol metabolite, which has a high content in human blood. 27-HC promotes breast cancer cell proliferation, invasion, and migration. We previously showed that 27-HC promotes EndMT; however, the underlying mechanism still needs to be further explored. We studied the role of the 14-3-3η/GSK-3β/β-catenin complex in EndMT. Our results show that 27-HC induces oxidative stress in HUVECs and activates the p38 signaling pathway, thereby inhibiting the binding of 14-3-3η/GSK-3β/β-catenin, promoting the increase of free β-catenin and nuclear translocation, and finally inducing EndMT. Treatment with N-acetylcysteine (NAC) blocked 27-HC-induced ROS generation and p38 signaling pathway activation, prevented β-catenin from release from binding, and inhibited EndMT. Blocking ROS production or p38 signaling or knocking down 14-3-3η inhibited 27-HC-induced EndMT and inhibited breast cancer cell metastasis. These findings indicate 14-3-3η is necessary for interactions between the p38 kinase and the GSK-3β/β-catenin complex and serves as an adaptor to transmit the upstream kinase signal to the downstream signal, thereby promoting EndMT and breast cancer cell migration.

14-3-3 σ: A potential biomolecule for cancer therapy

As more studies have focused on the function of 14-3-3 proteins, their role in tumor progression has gradually improved. In the 14-3-3 protein family, 14-3-3σ is the protein that is most associated with tumor occurrence and development. In some malignancies, 14-3-3σ acts as a tumor suppressor via p53 and tumor suppressor genes. In most tumors, 14-3-3σ overexpression increases resistance to chemotherapy and radiotherapy and mediates the G2-M checkpoint after DNA damage. Although 14-3-3σ overexpression has been closely associated with poorer prognosis in pancreatic, gastric and colorectal cancer, its role in gallbladder and nasopharyngeal cancer remains less clear. As such, the function of 14-3-3σ in specific cancer types needs to be further clarified. It has been hypothesized that a role may be related to its molecular chaperone function combined with various protein ligands. In this review, we examine the role of 14-3-3σ in tumor development and drug resistance. We discuss the potential of targeting 14-3-3σ regulators in cancer therapy and treatment.

A three-mRNA status risk score has greater predictive ability compared with a lncRNA-based risk score for predicting prognosis in patients with hepatocellular carcinoma

Hepatocellular carcinoma (HCC) represents the fifth most common cause of cancer-associated mortality in men, and the seventh in women, worldwide. The aim of the present study was to identify a reliable and robust RNA-based risk score for the survival prediction of patients with hepatocellular carcinoma (HCC). Gene expression data from HCC and healthy control samples were obtained from The Cancer Genome Atlas to screen differentially expressed mRNAs and long non-coding RNAs (lncRNAs). Univariate and multivariate Cox proportional-hazards regression models and the LASSO algorithm for the Cox proportional-hazards model (LASSO Cox-PH model) were used to identify the prognostic mRNAs and lncRNAs among differentially expressed mRNAs (DEMs) and differentially expressed lncRNAs (DELs), respectively. Prognostic risk scores were generated based on the expression level or status of the prognostic lncRNAs and mRNAs, and the predictive abilities of these RNAs in TCGA and validation datasets were compared. Functional enrichment analyses were also performed. The results revealed a total of 154 downregulated and 625 upregulated mRNAs and 18 upregulated lncRNAs between tumor and control samples in TCGA dataset. A three-mRNA and a five-lncRNA expression signatures were identified using the LASSO Cox-PH model. Three-mRNA and five-lncRNA expression and status risk scores were generated. Using likelihood ratio P-values and area under the curve values from TCGA and the validation datasets, the three-mRNA status risk score was more accurate compared with the other risk scores in predicting the mortality of patients with HCC. The three identified mRNAs, including hepatitis A virus cellular receptor 1, MYCN proto-oncogene BHLH transcription factor and stratifin, were associated with the cell cycle and oocyte maturation pathways. Therefore, a three-mRNA status risk score may be valuable and robust for risk stratification of patients with HCC. The three-mRNA status risk score exhibited greater prognostic value compared with the lncRNA-based risk score.

Reversal of sorafenib resistance in hepatocellular carcinoma: epigenetically regulated disruption of 14-3-3η/hypoxia-inducible factor-1α

Sorafenib resistance is one of the main obstacles to the treatment of advanced/recurrent hepatocellular carcinoma (HCC). Here, sorafenib-resistant HCC cells and xenografts in nude mice were used as experimental models. A cohort of patients with advanced recurrent HCC who were receiving sorafenib therapy was used to assess the clinical significance of this therapy. Our data showed that 14-3-3η maintained sorafenib resistance in HCC. An analysis of the underlying molecular mechanisms revealed that 14-3-3η stabilizes hypoxia-inducible factor 1α (HIF-1α) through the inhibition of ubiquitin-dependent proteasome protein degradation, which leads to the maintenance of cancer stem cell (CSC) properties. We further found that microRNA-16 (miR-16) is a competent miRNA that reverses sorafenib resistance by targeting the 3'-UTR of 14-3-3η and thereby inhibits 14-3-3η/HIF-1α/CSC properties. In HCC patients, significant negative correlations were found between the expression of miR-16 and 14-3-3η, HIF-1α, or CSC properties. Further analysis showed that low miR-16 expression but high 14-3-3η expression can prognosticate sorafenib resistance and poor survival. Collectively, our present study indicated that miR-16/14-3-3η is involved in sorafenib resistance in HCC and that these two factors could be potential therapeutic targets and biomarkers for predicting the response to sorafenib treatment.

Knockdown of tyrosine 3-monooxygenase/tryptophan 5-monooxygenase activation protein zeta (YWHAZ) enhances tumorigenesis both in vivo and in vitro in bladder cancer

Bladder cancer is the most common tumor of the urinary tract. Tyrosine 3-monooxygenase/tryptophan 5-monooxygenase activation protein zeta (YWHAZ), a gene encoding the 14-3-3ζ protein, has been observed to be frequently amplified in bladder cancer. However, the role of 14-3-3ζ in various types of cancer is controversial. With reproduction of The Cancer Genome Atlas database, we searched the correlation of YWHAZ expression with survival outcomes of multiple cancers in silico. Our results revealed that only in bladder cancer was there a positive survival trend with YWHAZ overexpression. To study its role in bladder cancer, YWHAZ was successfully downregulated by lentivirus in 5637 and T24 cells. MTT and colony-formation assays showed that YWHAZ downregulation increased cell proliferation. Wound healing and Transwell assays showed that YWHAZ downregulation enhanced cell migration and invasiveness. FACS analysis showed that YWHAZ induced cell cycle arrest, but not apoptosis. A xenograft tumor model revealed that YWHAZ knockdown enhanced tumor growth. Gene set enrichment analysis confirmed that the cell cycle pathway plays a vital role in the function of the YWHAZ gene. In conclusion, knockdown of YWHAZ promoted both in vitro and in vivo tumorigenesis in bladder cancer and may be a novel biomarker for bladder cancer deserving further study.

microRNA-874 suppresses tumor proliferation and metastasis in hepatocellular carcinoma by targeting the DOR/EGFR/ERK pathway

The δ opioid receptor (DOR) is involved in the regulation of malignant transformation and tumor progression of hepatocellular carcinoma (HCC). However, regulation of the DOR in HCC remains poorly defined. We found that miR-874 was identified as a negative regulator of the DOR, which is a direct and functional target of miR-874 via its 3' untranslated region (UTR). Moreover, miR-874 was downregulated in HCC and its expression was inversely correlated with DOR expression. Downregulation of miR-874 was also associated with larger tumor size, more vascular invasion, a poor TNM stage, poor tumor differentiation, and inferior patient outcomes. Functionally, overexpression of miR-874 in the HCC cell line SK-hep-1 inhibited cell growth, migration, in vitro invasion, and in vivo tumorigenicity. Furthermore, miR-874 overexpression suppressed the DOR, resulting in a downregulated epidermal growth factor receptor (EGFR) and extracellular signal-regulated kinase (ERK) phosphorylation. The EGFR activator-epidermal growth factor (EGF)-can rescue the proliferation and migration suppression induced by miR-874 overexpression, and the rescue effects of the EGF were blocked by an ERK inhibitor. Our study results suggest that miRNA-874 is a negative regulator of the DOR that can suppress tumor proliferation and metastasis in HCC by targeting the DOR/EGFR/ERK pathway, which may be a potential target for HCC treatment.

Paracrine regulation of matrix metalloproteinases contributes to cancer cell invasion by hepatocellular carcinoma-secreted 14-3-3σ

14-3-3σ overexpression results in enhanced hepatocellular carcinoma (HCC) cell migration and HCC tumor vascular-invasion is significantly associated with 14-3-3σ expression. However, increased expression of 14-3-3σ paradoxically suppresses in vitro cell invasion of HCC. We hypothesize that surrounding tumor-associated stromal cells play a crucial role in 14-3-3σ-regulated HCC cell invasion. In this study, H68 fibroblasts, THP-1 and phorbol-12-myristate-13-acetate (PMA)-treated THP-1 (PMA-THP-1) cells were incubated with conditioned media of control (control-CM) and 14-3-3σ-overepxressing cells (14-3-3σ-CM), followed by co-culture with HCC cells. Invasiveness of HCC cells was examined by a Boyden chamber assay. HCC cells co-cultured with 14-3-3σ-CM treated cells significantly enhanced their invasive ability compared with control-CM treated cells. Moreover, incubation with 14-3-3σ-CM induced differential expression profiles of matrix metalloproteinases (MMPs) in fibroblasts (MMP-1, MMP-2, MMP-9, MMP-12 and MMP-14), THP-1 (MMP-1 and MMP-12) and PMA-THP-1 cells (MMP-2, MMP-12 and MMP-14). In contrast, silencing of 14-3-3σ by siRNA significantly abolished 14-3-3σ-CM induced MMPs. In addition, treatment with recombinant 14-3-3σ (r14-3-3σ) protein exhibits a similar expression profile of MMPs induced by 14-3-3σ-CM in fibroblasts, THP-1 and PMA-THP-1 cells. Finally, knockdown of aminopeptidase N (APN) significantly abrogated r14-3-3σ induced expression of MMPs in HS68 fibroblasts. These results suggest that HCC-secreted 14-3-3σ promotes expression of MMPs in cancerous surrounding cells via an APN dependent mechanism. 14-3-3σ has a paracrine effect in educating stromal cells in tumor-associated microenvironment.

Coexistence of YWHAZ amplification predicts better prognosis in muscle-invasive bladder cancer with CDKN2A or TP53 loss

The amplification of YWHAZ was commonly seen in bladder cancer. We explore the biological significance of YWHAZ amplification on bladder cancer, and the correlation with important other molecular events. The Cancer Genome Atlas (TCGA) database was exploited to study the impact of YWHAZ amplification on either CDKN2A or TP53 mutations. The Database for Annotation, Visualization and Integrated Discovery (DAVID) was also exploited to clustering of enriched genes in the cBioPortal Enrichment tests. There were 127 cases with available mutation and CNV data in the corresponding TCGA bladder cancer dataset, 20% of them had YWHAZ alteration. Patients with both YWHAZ amplification and CDKN2A loss demonstrated significantly better overall survival (OS) compared with CDKN2A loss alone. Patients with both YWHAZ amplification and TP53 mutation demonstrated significantly better overall survival (OS) and disease-free survival (DFS) compared with TP53 mutation alone. The amplification of YWHAZ, along with alteration of CDKN2A or TP53, predict better survival in bladder cancers that only had CDKN2A or TP53 alteration. The protective role of YWHAZ in bladder cancer deserve insightful further studies.

Global proteomic profiling in multistep hepatocarcinogenesis and identification of PARP1 as a novel molecular marker in hepatocellular carcinoma

The more accurate biomarkers have long been desired for hepatocellular carcinoma (HCC). Here, we characterized global large-scale proteomics of multistep hepatocarcinogenesis in an attempt to identify novel biomarkers for HCC. Quantitative data of 37874 sequences and 3017 proteins during hepatocarcinogenesis were obtained in cohort 1 of 75 samples (5 pooled groups: normal livers, hepatitis livers, cirrhotic livers, peritumoral livers, and HCC tissues) by iTRAQ 2D LC-MS/MS. The diagnostic performance of the top six most upregulated proteins in HCC group and HSP70 as reference were subsequently validated in cohort 2 of 114 samples (hepatocarcinogenesis from normal livers to HCC) using immunohistochemistry. Of seven candidate protein markers, PARP1, GS and NDRG1 showed the optimal diagnostic performance for HCC. PARP1, as a novel marker, showed comparable diagnostic performance to that of classic markers GS and NDRG1 in HCC (AUCs = 0.872, 0.856 and 0.792, respectively). A significant higher AUC of 0.945 was achieved when three markers combined. For diagnosis of HCC, the sensitivity and specificity were 88.2% and 81.0% when at least two of the markers were positive. Similar diagnostic values of PARP1, GS and NDRG1 were confirmed by immunohistochemistry in cohort 3 of 180 HCC patients. Further analysis indicated that PARP1 and NDRG1 were associated with some clinicopathological features, and the independent prognostic factors for HCC patients. Overall, global large-scale proteomics on spectrum of multistep hepatocarcinogenesis are obtained. PARP1 is a novel promising diagnostic/prognostic marker for HCC, and the three-marker panel (PARP1, GS and NDRG1) with excellent diagnostic performance for HCC was established.

Identification of a novel YAP-14-3-3ζ negative feedback loop in gastric cancer

Growing evidence indicates that 14-3-3ζ and yes-associated protein (YAP) substantially promote tumorigenesis and tumor development. However, the regulatory mechanism underlying these two proteins remains unknown. Herein, we report a new regulatory role of 14-3-3ζ in the phosphorylation of YAP and the feedback inhibition of 14-3-3ζ by YAP. YAP and 14-3-3ζ expression exhibited a negative correlation in gastric cancer (GC) tissues. Moreover, patients with higher YAP and lower 14-3-3ζ expression had poor prognoses. Studies have revealed that 14-3-3ζ promotes cytoplasmic retention and suppresses the transcriptional activity of YAP by inducing its phosphorylation. Furthermore, we observed that the overexpression of YAP significantly reduced the expression of 14-3-3ζ by inducing its ubiquitination. YAP, 14-3-3ζ, and mouse double minute 2 homolog (MDM2) were colocalized, and the knockdown of MDM2 by siRNA attenuated the YAP-induced decrease of 14-3-3ζ. The binding of 14-3-3ζ and MDM2 was also restrained when the expression of YAP was interfered. Our results indicated the presence of a 14-3-3ζ-YAP negative regulatory feedback loop, which has a crucial role in cell proliferation and survival and is a potential target for the clinical treatment of GC.

20(S)-Ginsenoside Rh2 suppresses proliferation and migration of hepatocellular carcinoma cells by targeting EZH2 to regulate CDKN2A-2B gene cluster transcription

20(S)-Ginsenoside Rh2 (20(S)-GRh2) exerts important pharmacological effects with regard to the control of human hepatocellular carcinoma (HCC). EZH2 is a potent histone methyltransferase of H3K27me³, which has been determined as an oncogene in many malignancies. The CDKN2A-2B gene cluster encodes three important tumor suppressors, P14, P15 and P16. In this study, the anticancer effect and molecular mechanism of 20(S)-GRh2 on HCC was investigated. Treatment of HCC cells with 20(S)-GRh2 inhibited cell proliferation, migration and induced cell cycle arrest at the G0/G1 phase, and inhibited tumor growth in vivo. We demonstrate for the first time that this effect was specifically mediated by down-regulating expression of EZH2. Further molecular mechanism study indicated that the decreased EZH2 promoted P14, P15 and P16 gene transcription through reducing H3K27me³ modification in the promoter of CDKN2A-2B gene cluster loci. Similarly, silencing of EZH2 by siRNA down-regulated P14, P15, P16 mRNA levels and inhibited HCC cell proliferation. Our results suggested that EZH2 could be a potentially therapeutic target by 20(S)-GRh2 in HCC, which provided a rationale for the development of drugs that inhibited histone methylase as a strategy against various cancers.

14-3-3σ downregulation suppresses ICC metastasis via impairing migration, invasion, and anoikis resistance of ICC cells

BACKGROUND

14-3-3σ protein plays an important role in multiple cellular processes. The role of 14-3-3σ in the progression of intrahepatic cholangiocarcinoma (ICC) has not been well understood.

OBJECTIVE

We performed this research to explore the relationship between 14-3-3σ level and clinical characteristics and prognosis of ICC patients. Besides, we used ICC cell lines HCCC-9810 and RBE to assess the biological function of 14-3-3σ.

METHODS

We examined 14-3-3σ expression in 28 ICC tissues and matched paratumor tissues by quantitative real-time PCR and immunohistochemistry. Additionally, ICC tissue array from 100 patients and normal liver tissue array from 24 healthy people were also analyzed by immunohistochemistry. 14-3-3σ was knocked down in ICC cell lines and the functions and mechanisms of 14-3-3σ were assessed.

RESULTS

14-3-3σ is highly expressed in ICC tissues and high expression of 14-3-3σ correlates poor overall survival in ICC patients. Knocking down of 14-3-3σ in ICC cell lines reduced cells migration, invasion and anoikis resistance. Furthermore, 14-3-3σ-silenced ICC cells showed significantly decreased invasion-related protein MMP2 and MMP9 expression.

CONCLUSIONS

Our results demonstrate prognostic value of 14-3-3σ and its role in metastasis, which is associated with ICC cell lines migration, invasion and anoikis resistance.

Regulation and role of post-translational modifications of enhancer of zeste homologue 2 in cancer development

Post-translational modifications (PTMs) are critical molecular events which alter protein conformation after their synthesis and diversity protein properties by modulating their stability, localization, interacting partners or the activity of their substrates, consequently exerting pivotal roles in regulating the functions of many important eukaryotic proteins. It has been well acknowledged that PTMs are of great importance in a broad range of biological processes such as gene regulation, cell proliferation, differentiation and apoptosis, tissue development, diseases, tumor progression and drug resistance. As the core and contributing catalytic subunit of Polycomb repressive complex 2(PRC2), Enhancer of zeste homolog 2 (EZH2) is a master epigenetic regulator, often serving as a highly conserved histone methyltransferase (HMTase) to induce histone H3 lysine 27 trimethylation (H3K27me3) and repress gene transcription and expression. Dysregulated EZH2 expression is frequently associated with cancer development and poor prognosis in a wide variety of cancers. Considered its essential role in carcinogenesis, EZH2 is a potential candidate for cancer targeted therapy. Remarkably, mounting evidence highlights that EZH2 expression, activity and stability can be regulated by PTMs including phosphorylation, acetylation, ubiquitination, sumoylation and GlcNAcylation aside from its well-validated modifications in transcriptional and post-transcriptional levels. However, the precise regulatory mechanisms underlying EZH2 PTMs and whether other types of PTMs orchestrate in EZH2 remain largely unclear. In this review, we summarize current advances in the understanding of EZH2 regulation by PTMs and their associated biological functions during tumorigenesis.

Prognostic value of high EZH2 expression in patients with different types of cancer: a systematic review with meta-analysis

Enhancer of zeste homologue 2 (EZH2) is a potential independent mechanism for epigenetic silencing of tumor suppressor genes in cancer. We conducted an electronic search on PubMed, EMBASE, Web of Science, and Cochrane library to perform this up-to-date meta-analysis. Fifty-one studies with a total of 9444 patients were included. The prevalence of high EZH2 expression was 0.54 (95% CI: 0.47-0.61). High EZH2 expression was significantly associated with poorer prognosis [overall survival: HR 1.54 (95% CI: 1.30-1.78), P < 0.000; disease free survival: HR 1.35 (95% CI: 1.00-1.71), P < 0.000]. In breast cancer, high EZH2 expression correlated with histological types [OR: 1.53 (95CI: 1.13-2.06); P < 0.006], histological grade [OR: 1.62 (95CI: 1.35-1.95); P < 0.000], estrogen receptor (ER) negativity [OR: 2.05 (95CI: 1.67-2.52); P < 0.000], progesterone receptor (PgR) negativity [OR: 1.42 (95CI: 1.03-1.96); P = 0.034], HER-2 positivity [OR: 1.35 (95CI: 1.08-1.69); P = 0.009], and high p53 expression [OR: 1.66 (95CI: 1.07-2.59); P = 0.024]. These results suggest that high EZH2 expression may be a promising prognostic factor to different cancers. High EZH2 expression tends to correlate with pathological types, histological grade, ER negativity, PgR negativity, HER-2 positivity and p53 high expression in breast cancer.

Regulation of aldo-keto-reductase family 1 B10 by 14-3-3ε and their prognostic impact of hepatocellular carcinoma

14-3-3ε is overexpressed in hepatocellular carcinoma (HCC) and its expression significantly associates with a poor prognostic outcome. To uncover how 14-3-3ε contributes to the tumor progression of HCC, we investigated the potential downstream targets regulated by 14-3-3ε. We found that 14-3-3ε increases expression and nuclear translocation of β-catenin and that 14-3-3ε-induced cell proliferation is attenuated by β-catenin silencing in HCC cells. Moreover, 14-3-3ε induces aldo-keto reductase family 1 member B10 (AKR1B10) expression through the activation of β-catenin signaling. Knockdown of AKR1B10 by siRNAs abolished 14-3-3ε-induced in vitro cell proliferation, anchorage-independent growth as well as in vivo tumor growth. Furthermore, AKR1B10 silencing increased retinoic acid (RA) levels in the serum of tumor-bearing mice and RA treatment attenuated 14-3-3ε-induced HCC cell proliferation. We further examined 14-3-3ε and AKR1B10 expression and clinicopathological characteristics of HCC tumors. Although the expression of AKR1B10 was significantly correlated with 14-3-3ε, an increase of AKR1B10 expression in 14-3-3ε positive patients paradoxically had better overall survival and disease-free survival rates as well as lower metastatic incidence than those without an AKR1B10 increase. Finally, we found a loss of AKR1B10 expression in cells exhibiting a high capacity of invasiveness. Silencing of AKR1B10 resulted in inducing snail and vimentin expression in HCC cells. These results indicate that AKR1B10 may play a dual role during HCC tumor progression. Our results also indicate that 14-3-3ε regulates AKR1B10 expression by activating β-catenin signaling. A combination of 14-3-3ε with AKR1B10 is a potential therapeutic target and novel prognostic biomarker of HCC.

MicroRNA-506 suppresses tumor proliferation and metastasis in colon cancer by directly targeting the oncogene EZH2

Increasing evidence reveals that aberrant expression of microRNA contributes to the development and progression of colon cancer, but the roles of microRNA-506 (miR-506) in colon cancer remain elusive. Here, we demonstrated that miR-506 was down-regulated in colon cancer tissue and cells and that miR-506 expression was inversely correlated with EZH2 expression, tumor size, lymph node invasion, TNM stage and metastasis. A high level of miR-506 identified patients with a favorable prognosis. In vitro and in vivo experiments confirmed that miR-506 inhibits the proliferation and metastasis of colon cancer, and a luciferase reporter assay confirmed that EZH2 is a direct and functional target of miR-506 via the 3′UTR of EZH2. The restoration of EZH2 expression partially reversed the proliferation and invasion of miR-506-overexpressing colon cancer cells. Moreover, we confirmed that the miR-506-EZH2 axis inhibits proliferation and metastasis by activating/suppressing specific downstream tumor-associated genes and the Wnt/β-catenin signaling pathway. Taking together, our study sheds light on the role of miR-506 as a suppressor for tumor growth and metastasis and raises the intriguing possibility that miR-506 may serve as a new potential marker for monitoring and treating colon cancer.

Identification of 14-3-3 Proteins Phosphopeptide-Binding Specificity Using an Affinity-Based Computational Approach

The 14-3-3 proteins are a highly conserved family of homodimeric and heterodimeric molecules, expressed in all eukaryotic cells. In human cells, this family consists of seven distinct but highly homologous 14-3-3 isoforms. 14-3-3σ is the only isoform directly linked to cancer in epithelial cells, which is regulated by major tumor suppressor genes. For each 14-3-3 isoform, we have 1,000 peptide motifs with experimental binding affinity values. In this paper, we present a novel method for identifying peptide motifs binding to 14-3-3σ isoform. First, we propose a sampling criteria to build a predictor for each new peptide sequence. Then, we select nine physicochemical properties of amino acids to describe each peptide motif. We also use auto-cross covariance to extract correlative properties of amino acids in any two positions. Finally, we consider elastic net to predict affinity values of peptide motifs, based on ridge regression and least absolute shrinkage and selection operator (LASSO). Our method tests on the 1,000 known peptide motifs binding to seven 14-3-3 isoforms. On the 14-3-3σ isoform, our method has overall pearson-product-moment correlation coefficient (PCC) and root mean squared error (RMSE) values of 0.84 and 252.31 for N-terminal sublibrary, and 0.77 and 269.13 for C-terminal sublibrary. We predict affinity values of 16,000 peptide sequences and relative binding ability across six permutated positions similar with experimental values. We identify phosphopeptides that preferentially bind to 14-3-3σ over other isoforms. Several positions on peptide motifs are in the same amino acid category with experimental substrate specificity of phosphopeptides binding to 14-3-3σ. Our method is fast and reliable and is a general computational method that can be used in peptide-protein binding identification in proteomics research.

Binding of 14-3-3 reader proteins to phosphorylated DNMT1 facilitates aberrant DNA methylation and gene expression

Mammalian DNA (cytosine-5) methyltransferase 1 (DNMT1) is essential for maintenance methylation. Phosphorylation of Ser143 (pSer143) stabilizes DNMT1 during DNA replication. Here, we show 14-3-3 is a reader protein of DNMT1pSer143. In mammalian cells 14-3-3 colocalizes and binds DNMT1pSer143 post-DNA replication. The level of DNMT1pSer143 increased with overexpression of 14-3-3 and decreased by its depletion. Binding of 14-3-3 proteins with DNMT1pSer143 resulted in inhibition of DNA methylation activity in vitro. In addition, overexpression of 14-3-3 in NIH3T3 cells led to decrease in DNMT1 specific activity resulting in hypomethylation of the genome that was rescued by transfection of DNMT1. Genes representing cell migration, mobility, proliferation and focal adhesion pathway were hypomethylated and overexpressed. Furthermore, overexpression of 14-3-3 also resulted in enhanced cell invasion. Analysis of TCGA breast cancer patient data showed significant correlation for DNA hypomethylation and reduced patient survival with increased 14-3-3 expressions. Therefore, we suggest that 14-3-3 is a crucial reader of DNMT1pSer143 that regulates DNA methylation and altered gene expression that contributes to cell invasion.

Involvement of 14-3-3 Proteins in Regulating Tumor Progression of Hepatocellular Carcinoma

There are seven mammalian isoforms of the 14-3-3 protein, which regulate multiple cellular functions via interactions with phosphorylated partners. Increased expression of 14-3-3 proteins contributes to tumor progression of various malignancies. Several isoforms of 14-3-3 are overexpressed and associate with higher metastatic risks and poorer survival rates of hepatocellular carcinoma (HCC). 14-3-3β and 14-3-3ζ regulate HCC cell proliferation, tumor growth and chemosensitivity via modulating mitogen-activated protein kinase (MAPK), c-Jun N-terminal kinase (JNK) and p38 signal pathways. Moreover, 14-3-3ε suppresses E-cadherin and induces focal adhesion kinase (FAK) expression, thereby enhancing epithelial-mesenchymal transition (EMT) and HCC cell migration. 14-3-3ζ forms complexes with αB-crystallin, which induces EMT and is the cause of sorafenib resistance in HCC. Finally, a recent study has indicated that 14-3-3σ induces heat shock protein 70 (HSP70) expression, which increases HCC cell migration. These results suggest that selective 14-3-3 isoforms contribute to cell proliferation, EMT and cell migration of HCC by regulating distinct targets and signal pathways. Targeting 14-3-3 proteins together with specific downstream effectors therefore has potential to be therapeutic and prognostic factors of HCC. In this article, we will overview 14-3-3’s regulation of its downstream factors and contributions to HCC EMT, cell migration and proliferation.

MicroRNA-31 functions as a tumor suppressor by regulating cell cycle and epithelial-mesenchymal transition regulatory proteins in liver cancer

MicroRNA-31 (miR-31) is among the most frequently altered microRNAs in human cancers and altered expression of miR-31 has been detected in a large variety of tumor types, but the functional role of miR-31 still hold both tumor suppressive and oncogenic roles in different tumor types. MiR-31 expression was down-regulated in a large cohort of hepatocellular carcinoma (HCC) patients, and low expression of miR-31 was significantly associated with poor prognosis of HCC patients. Ectopic expression of miR-31 mimics suppressed HCC cell growth by transcriptional deregulation of cell cycle proteins. Additional study evidenced miR-31 directly to suppress HDAC2 and CDK2 expression by inhibiting mRNA translation in HCC cells. We also found that ectopic expression of miR-31 mimics reduced metastatic potential of HCC cells by selectively regulating epithelial-mesenchymal transition (EMT) regulatory proteins such as N-cadherin, E-cadherin, vimentin and fibronectin. HCC tissues derived from chemical-induced rat liver cancer models validated that miR-31 expression is significantly down-regulated, and that those cell cycle- and EMT-regulatory proteins are deregulated in rat liver cancer. Overall, we suggest that miR-31 functions as a tumor suppressor by selectively regulating cell cycle and EMT regulatory proteins in human hepatocarcinogenesis providing a novel target for the molecular treatment of liver malignancies.