Up-regulation of 14-3-3zeta in lung cancer and its implication as prognostic and therapeutic target

MiR-3074-5p suppresses non-small cell lung cancer progression by targeting the YWHAZ/Hsp27 axis

Non-small cell lung cancer (NSCLC) accounts for more than 80% of lung cancer cases, and the 5-year survival rate of patients remains unsatisfactory. MicroRNAs (miRNAs) are small endogenous noncoding RNAs that are considered essential posttranscriptional regulators of tumorigenesis, including NSCLC. In this study, we aimed to investigate the biological role of miR-3074-5p in NSCLC cells and the underlying molecular mechanisms. We showed that miR-3074-5p expression was decreased in human NSCLC specimens and cell lines. Moreover, miR-3074-5p overexpression inhibited cell proliferation, migration and invasion and induced apoptosis and cell cycle arrest. In addition, miR-3074-5p overexpression not only suppressed tumor growth but also enhanced the antitumor effect of paclitaxel (PTX) on NSCLC cells in vitro and in vivo. A transcriptome sequencing assay revealed genes that were differentially expressed after miR-3074-5p overexpression, and among the genes whose expression levels were most significantly decreased, tyrosine 3-monooxygenase/tryptophan 5-monooxygenase activation protein zeta (YWHAZ) was a target of miR-3074-5p. The regulatory effect of miR-3074-5p on YWHAZ expression was verified by Western blotting and dual-luciferase reporter assays. The inhibition of A549 cell growth, migration and invasion was reversed by YWHAZ overexpression. Furthermore, we showed that PTX stimulated the expression of the YWHAZ and Hsp27 proteins and promoted the phosphorylation of Hsp27 (at S15 and S78). YWHAZ was confirmed to interact with Hsp27 in A549 cells, and downregulating YWHAZ expression promoted the degradation of the Hsp27 protein. Taken together, these results suggest that the miR-3074-5p/YWHAZ/Hsp27 axis may be a novel therapeutic target for NSCLC treatment.

Quantitative proteomics reveals serum proteome alterations during metastatic disease progression in breast cancer patients

BACKGROUND

Tumor recurrence and metastatic progression remains the leading cause for breast cancer related mortalities. However, the proteomes of patient- matched primary breast cancer (BC) and metastatic lesions have not yet been identified, due to the lack of clinically annotated longitudinal samples. In this study, we evaluated the global-proteomic landscape of BC patients with and without distant metastasis as well as compared the proteome of distant metastatic disease with its corresponding primary BC, within the same patient.

METHODS

We performed mass spectrometry-based proteome profiling of 73 serum samples from 51 BC patients. Among the 51 patients with BC, 29 remained metastasis-free (henceforth called non-progressors), and 22 developed metastases (henceforth called progressors). For the 22 progressors, we obtained two samples: one collected within a year of diagnosis, and the other collected within a year before the diagnosis of metastatic disease. MS data were analyzed using intensity-based absolute quantification and normalized before differential expression analysis. Significantly differentially expressed proteins (DEPs; absolute fold-change ≥ 1.5, P-value < 0.05 and 30% abundance per clinical group) were subjected to pathway analyses.

RESULTS

We identified 967 proteins among 73 serum samples from patients with BC. Among these, 39 proteins were altered in serum samples at diagnosis, between progressors and non-progressors. Among these, 4 proteins were further altered when the progressors developed distant metastasis. In addition, within progressors, 20 proteins were altered in serum collected at diagnosis versus at the onset of metastasis. Pathway analysis showed that these proteins encoded pathways that describe metastasis, including epithelial-mesenchymal transition and focal adhesion that are hallmarks of metastatic cascade.

CONCLUSIONS

Our results highlight the importance of examining matched samples from distant metastasis with primary BC samples collected at diagnosis to unravel subset of proteins that could be involved in BC progression in serum. This study sets the foundation for additional future investigations that could position these proteins as non-invasive markers for clinically monitoring breast cancer progression in patients.

YWHAG promotes colorectal cancer progression by regulating the CTTN-Wnt/β-catenin signaling axis

Colorectal cancer (CRC) ranks as the third most prevalent cancer type globally. Nevertheless, the fundamental mechanisms driving CRC progression remain ambiguous, and the prognosis for the majority of patients diagnosed at an advanced stage is dismal. YWHA/14-3-3 proteins serve as central nodes in several signaling pathways and are closely related to tumorigenesis and progression. However, their exact roles in CRC are still poorly elucidated. In this study, we revealed that YWHAG was the most significantly upregulated member of the YWHA/14-3-3 family in CRC tissues and was associated with a poor prognosis. Subsequent phenotypic experiments showed that YWHAG promoted the proliferation, migration, and invasion of CRC cells. Mechanistically, RNA-seq data showed that multiple signaling pathways, including Wnt and epithelial-mesenchymal transition, were potentially regulated by YWHAG. CTTN was identified as a YWHAG-associated protein, and mediated its tumor-promoting functions by activating the Wnt/β-catenin signaling in CRC cells. In summary, our data indicate that YWHAG facilitates the proliferation, migration, and invasion of CRC cells by modulating the CTTN-Wnt/β-catenin signaling pathway, which offers a novel perspective for the treatment of CRC.

YWHAG Deficiency Disrupts the EMT-Associated Network to Induce Oxidative Cell Death and Prevent Metastasis

Metastasis involves epithelial-to-mesenchymal transition (EMT), a process that is regulated by complex gene networks, where their deliberate disruption may yield a promising outcome. However, little is known about mechanisms that coordinate these metastasis-associated networks. To address this gap, hub genes with broad engagement across various human cancers by analyzing the transcriptomes of different cancer cell types undergoing EMT are identified. The oncogenic signaling adaptor protein tyrosine 3-monooxygenase/tryptophan 5-monooxygenase activation protein gamma (YWHAG) is ranked top for its clinical relevance and impact. The cellular kinome and transcriptome data are surveyed to construct the regulome of YWHAG, revealing stress responses and metabolic processes during cancer EMT. It is demonstrated that a YWHAG-dependent cytoprotective mechanism in the regulome is embedded in EMT-associated networks to protect cancer cells from oxidative catastrophe through enhanced autophagy during EMT. YWHAG deficiency results in a rapid accumulation of reactive oxygen species (ROS), delayed EMT, and cell death. Tumor allografts show that metastasis potential and overall survival time are correlated with the YWHAG expression level of cancer cell lines. Metastasized tumors have higher expression of YWHAG and autophagy-related genes than primary tumors. Silencing YWHAG diminishes primary tumor volumes, prevents metastasis, and prolongs the median survival period of the mice.

Analyzing the Impact of Diesel Exhaust Particles on Lung Fibrosis Using Dual PCR Array and Proteomics: YWHAZ Signaling

Air pollutants are associated with exacerbations of asthma, chronic bronchitis, and airway inflammation. Diesel exhaust particles (DEPs) can induce and worsen lung diseases. However, there are insufficient data to guide polymerase chain reaction (PCR) array proteomics studies regarding the impacts of DEPs on respiratory diseases. This study was performed to identify genes and proteins expressed in normal human bronchial epithelial (NHBE) cells. MicroRNAs (miRNAs) and proteins expressed in NHBE cells exposed to DEPs at 1 μg/cm2 for 8 h and 24 h were identified using PCR array analysis and 2D PAGE/LC-MS/MS, respectively. YWHAZ gene expression was estimated using PCR, immunoblotting, and immunohistochemical analyses. Genes discovered through an overlap analysis were validated in DEP-exposed mice. Proteomics approaches showed that exposing NHBE cells to DEPs led to changes in 32 protein spots. A transcriptomics PCR array analysis showed that 6 of 84 miRNAs were downregulated in the DEP exposure groups compared to controls. The mRNA and protein expression levels of YWHAZ, β-catenin, vimentin, and TGF-β were increased in DEP-treated NHBE cells and DEP-exposed mice. Lung fibrosis was increased in mice exposed to DEPs. Our combined PCR array-omics analysis demonstrated that DEPs can induce airway inflammation and lead to lung fibrosis through changes in the expression levels of YWHAZ, β-catenin, vimentin, and TGF-β. These findings suggest that dual approaches can help to identify biomarkers and therapeutic targets involved in pollutant-related respiratory diseases.

Streptococcus pneumoniae promotes lung cancer development and progression

Streptococcus pneumoniae (SP) is associated with lung cancer, yet its role in the tumorigenesis remains uncertain. Herein we find that SP attaches to lung cancer cells via binding pneumococcal surface protein C (PspC) to platelet-activating factor receptor (PAFR). Interaction between PspC and PAFR stimulates cell proliferation and activates PI3K/AKT and nuclear factor kB (NF-kB) signaling pathways, which trigger a pro-inflammatory response. Lung cancer cells infected with SP form larger tumors in BALB/C mice compared to untreated cells. Mice treated with tobacco carcinogen and SP develop more lung tumors and had shorter survival period than mice treated with the carcinogen alone. Mutating PspC or PAFR abolishes tumor-promoting effects of SP. Overabundance of SP is associated with the survival. SP may play a driving role in lung tumorigenesis by activating PI3K/AKT and NF-kB pathways via binding PspC to PAFR and provide a microbial target for diagnosis and treatment of the disease.

Single-cell RNA analysis to identify five cytokines signaling in immune-related genes for melanoma survival prognosis

Melanoma is one of the deadliest skin cancers. Recently, developed single-cell sequencing has revealed fresh insights into melanoma. Cytokine signaling in the immune system is crucial for tumor development in melanoma. To evaluate melanoma patient diagnosis and treatment, the prediction value of cytokine signaling in immune-related genes (CSIRGs) is needed. In this study, the machine learning method of least absolute selection and shrinkage operator (LASSO) regression was used to establish a CSIRG prognostic signature of melanoma at the single-cell level. We discovered a 5-CSIRG signature that was substantially related to the overall survival of melanoma patients. We also constructed a nomogram that combined CSIRGs and clinical features. Overall survival of melanoma patients can be consistently predicted with good performance as well as accuracy by both the 5-CSIRG signature and nomograms. We compared the melanoma patients in the CSIRG high- and low-risk groups in terms of tumor mutation burden, infiltration of the immune system, and gene enrichment. High CSIRG-risk patients had a lower tumor mutational burden than low CSIRG-risk patients. The CSIRG high-risk patients had a higher infiltration of monocytes. Signaling pathways including oxidative phosphorylation, DNA replication, and aminoacyl tRNA biosynthesis were enriched in the high-risk group. For the first time, we constructed and validated a machine-learning model by single-cell RNA-sequencing datasets that have the potential to be a novel treatment target and might serve as a prognostic biomarker panel for melanoma. The 5-CSIRG signature may assist in predicting melanoma patient prognosis, biological characteristics, and appropriate therapy.

Interactions between 14-3-3 Proteins and Actin Cytoskeleton and Its Regulation by microRNAs and Long Non-Coding RNAs in Cancer

14-3-3s are a family of structurally similar proteins that bind to phosphoserine or phosphothreonine residues, forming the central signaling hub that coordinates or integrates various cellular functions, thereby controlling many pathways important in cancer, cell motility, cell death, cytoskeletal remodeling, neuro-degenerative disorders and many more. Their targets are present in all cellular compartments, and when they bind to proteins they alter their subcellular localization, stability, and molecular interactions with other proteins. Changes in environmental conditions that result in altered homeostasis trigger the interaction between 14-3-3 and other proteins to retrieve or rescue homeostasis. In circumstances where these regulatory proteins are dysregulated, it leads to pathological conditions. Therefore, deeper understanding is needed on how 14-3-3 proteins bind, and how these proteins are regulated or modified. This will help to detect disease in early stages or design inhibitors to block certain pathways. Recently, more research has been devoted to identifying the role of MicroRNAs, and long non-coding RNAs, which play an important role in regulating gene expression. Although there are many reviews on the role of 14-3-3 proteins in cancer, they do not provide a holistic view of the changes in the cell, which is the focus of this review. The unique feature of the review is that it not only focuses on how the 14-3-3 subunits associate and dissociate with their binding and regulatory proteins, but also includes the role of micro-RNAs and long non-coding RNAs and how they regulate 14-3-3 isoforms. The highlight of the review is that it focuses on the role of 14-3-3, actin, actin binding proteins and Rho GTPases in cancer, and how this complex is important for cell migration and invasion. Finally, the reader is provided with super-resolution high-clarity images of each subunit of the 14-3-3 protein family, further depicting their distribution in HeLa cells to illustrate their interactions in a cancer cell.

Overexpression of 14-3-3ζ primes disease recurrence, metastasis and resistance to chemotherapy by inducing epithelial-mesenchymal transition in NSCLC

The prognosis of non-small cell lung cancer (NSCLC) is disappointing because disease recurrence and distant metastasis inevitably occurred. The aim of the present study is to identify novel biomarkers predicting tumor recurrence and metastasis. The 14-3-3ζ protein has been extensively described as a tumor promoter in a panel of solid tumors, including NSCLC. However, there is a big gap regarding the knowledge between 14-3-3ζ and NSCLC recurrence. In this study, we found that overexpression of 14-3-3ζ was more frequent in NSCLC tumor tissues with tumor recurrence. By using scratch healing assay and transwell assay, we demonstrated that NSCLC cells with high expression of 14-3-3ζ gained increased motile and invasive capacity, whereas siRNA-mediated knockdown of endogenous 14-3-3ζ abrogated cancer cell dissemination. Intriguingly, we found that NSCLC cells underwent epithelial-mesenchymal transition (EMT) after the induction of 14-3-3ζ in vitro and in vivo. These findings could be readily recaptured in clinical setting since we showed that NSCLC tumor specimen with high expression of 14-3-3ζ revealed biological features of EMT. Overexpression of 14-3-3ζ also enhanced the phosphorylation of Akt and promoted the proliferation of NSCLC cell lines. In agreement with this notion, we reported that NSCLC cells with high expression of 14-3-3ζ became resistant to chemotherapy-induced apoptosis. These findings strongly suggested that 14-3-3ζ as a novel biomarker predicting risks of disease recurrence and screening 14-3-3ζ status may be a promising approach to select patients who experienced high risks of cancer recurrence and resistance to chemotherapy.

YWHAE/14-3-3ε expression impacts the protein load, contributing to proteasome inhibitor sensitivity in multiple myeloma

High protein load is a feature of multiple myeloma (MM), making the disease exquisitely sensitive to proteasome inhibitor (PIs). Despite the success of PIs in improving patient outcome, the majority of patients develop resistance leading to progressive disease; thus, the need to investigate the mechanisms driving the drug sensitivity vs resistance. With the well-recognized chaperone function of 14-3-3 proteins, we evaluated their role in affecting proteasome activity and sensitivity to PIs by correlating expression of individual 14-3-3 gene and their sensitivity to PIs (bortezomib and carfilzomib) across a large panel of MM cell lines. We observed a significant positive correlation between 14-3-3ε expression and PI response in addition to a role for 14-3-3ε in promoting translation initiation and protein synthesis in MM cells through binding and inhibition of the TSC1/TSC2 complex, as well as directly interacting with and promoting phosphorylation of mTORC1. 14-3-3ε depletion caused up to a 50% reduction in protein synthesis, including a decrease in the intracellular abundance and secretion of the light chains in MM cells, whereas 14-3-3ε overexpression or addback in knockout cells resulted in a marked upregulation of protein synthesis and protein load. Importantly, the correlation among 14-3-3ε expression, PI sensitivity, and protein load was observed in primary MM cells from 2 independent data sets, and its lower expression was associated with poor outcome in patients with MM receiving a bortezomib-based therapy. Altogether, these observations suggest that 14-3-3ε is a predictor of clinical outcome and may serve as a potential target to modulate PI sensitivity in MM.

Microenvironmental Th9 and Th17 lymphocytes induce metastatic spreading in lung cancer

Immune microenvironment plays a critical role in lung cancer control versus progression and metastasis. In this investigation, we explored the effect of tumor-infiltrating lymphocyte subpopulations on lung cancer biology by studying in vitro cocultures, in vivo mouse models, and human lung cancer tissue. Lymphocyte conditioned media (CM) induced epithelial-mesenchymal transition (EMT) and migration in both primary human lung cancer cells and cell lines. Correspondingly, major accumulation of Th9 and Th17 cells was detected in human lung cancer tissue and correlated with poor survival. Coculturing lung cancer cells with Th9/Th17 cells or exposing them to the respective CM induced EMT in cancer cells and modulated the expression profile of genes implicated in EMT and metastasis. These features were reproduced by the signatory cytokines IL-9 and IL-17, with gene regulatory profiles evoked by these cytokines partly overlapping and partly complementary. Coinjection of Th9/Th17 cells with tumor cells in WT, Rag1-/-, Il9r-/-, and Il17ra-/- mice altered tumor growth and metastasis. Accordingly, inhibition of IL-9 or IL-17 cytokines by neutralizing antibodies decreased EMT and slowed lung cancer progression and metastasis. In conclusion, Th9 and Th17 lymphocytes induce lung cancer cell EMT, thereby promoting migration and metastatic spreading and offering potentially novel therapeutic strategies.

Autoantibodies against tumor-associated antigens in sputum as biomarkers for lung cancer

Tumor antigens (TAs) can initiate host immune responses and produce TA-associated autoantibody (TAAbs), potential cancer biomarkers. Sputum is directly generated from the upper and lower airways, and thus can be used as a surrogate sample for the diagnosis of lung cancer based on molecular analysis. To develop sputum TAAb biomarkers for the early detection of lung cancer, the leading cause of cancer death, we probed a protein microarray containing more than 9,000 antigens with sputum supernatants of a discovery set of 30 lung cancer patients and 30 cancer-free smokers. Twenty-eight TAs with higher reactivity in sputum of lung cancer cases vs. controls were identified. The diagnostic significance of TAAbs against the TAs was determined by enzyme-linked immunosorbent assays (ELISAs) in sputum of the discovery set and additional 166 lung cancer patients and 213 cancer-free smokers (validation set). Three sputum TAAbs against DDX6, ENO1, and 14-3-3ζ were developed as a biomarker panel with 81% sensitivity and 83% specificity for diagnosis of lung cancer, regardless of stages, locations, and histological types of lung tumors. This study provides the first evidence that sputum TAAbs could be used as biomarkers for the early detection of lung cancer.

Targeting 14-3-3ζ Overcomes Resistance to Epidermal Growth Factor Receptor-Tyrosine Kinase Inhibitors in Lung Adenocarcinoma via BMP2/Smad/ID1 Signaling

Background: The 14-3-3ζ protein, which acts as a putative oncoprotein, has been found to promote the proliferation, metastasis, and chemoresistance of cancer cells in several cancers including lung adenocarcinoma (LUAD); however, its significance in epidermal growth factor receptor–tyrosine kinase inhibitor (EGFR-TKI) resistance remains unknown.

Methods: The Cancer Genome Atlas (TCGA) database was used to determine 14-3-3ζ expression in pancancer and LUAD. 14-3-3ζ and ID1 expression was then examined in clinical LUAD samples by immunohistochemistry (IHC). Lentiviral transfection with 14-3-3ζ-specific small hairpin RNA (shRNA) was used to establish stable 14-3-3ζ knockdown gefitinib-resistant PC9 (PC9/GR) and H1975 cell lines. The effect of 14-3-3ζ knockdown on reversing EGFR-TKI resistance was determined in vitro by Cell Counting Kit-8 (CCK-8), wound healing, Transwell assays, and flow cytometry. A xenograft tumor model was established to evaluate the role of 14-3-3ζ in EGFR-TKI resistance. Microarray analysis results showed multiple pathways regulated by 14-3-3ζ-shRNA.

Results: In the present study, we demonstrated that based on the TCGA, pancancer and LUAD 14-3-3ζ expression was elevated and predicted unfavorable prognosis. In addition, high 14-3-3ζ expression was associated with advanced T stage, TNM stage, presence of lymph node metastasis and, importantly, poor treatment response to EGFR-TKIs in LUAD patients with EGFR-activating mutations. 14-3-3ζ shRNA sensitized EGFR-TKI-resistant human LUAD cells to gefitinib and reversed epithelial-to-mesenchymal transition (EMT). After 14-3-3ζ depletion, bone morphogenetic protein (BMP) signaling activation was decreased in EGFR-TKI-resistant cells in microarray analysis, which was further validated by Western blot analysis. Furthermore, the expression of 14-3-3ζ positively correlates with ID1 expression in human EGFR-mutant LUAD patient samples. In vivo, there was a reduction in the tumor burden in mice treated with 14-3-3ζ shRNA and gefitinib compared to mice treated with gefitinib alone.

Conclusion: Our work uncovers a hitherto unappreciated role of 14-3-3ζ in EGFR-TKI resistance. This study might provide a potential therapeutic approach for treating LUAD patients harboring EGFR mutations.

Curcumin induces apoptosis in lung cancer cells by 14-3-3 protein-mediated activation of Bad

The anticancer effects of curcumin are based on the induction of apoptosis, but the specific mechanisms have not yet been fully elucidated. To address this issue, we investigated the effects of curcumin on the intrinsic apoptosis pathway using mitochondria from A549 cells. Curcumin decreased the levels of 14-3-3 proteins, key molecules that inhibit the activation of proapoptotic factors known as BH3-only proteins (e.g. Bad). Curcumin-induced suppression of 14-3-3 protein levels was associated with reduced cytosolic Bad and elevation of mitochondrial Bad, leading to a drop in the mitochondrial membrane potential. 14-3-3 proteins generally interact with Bad phosphorylated by AKT, thus preventing its translocation to the mitochondria where it can promote cell death. Curcumin not only decreased the expression of 14-3-3 proteins but also promoted Bad dephosphorylation in an AKT-dependent fashion. Our results provide novel evidence for the induction of apoptosis by curcumin at multiple stages of the mitochondrial cascade.

Overexpression of 14-3-3δ Predicts Poor Prognosis in Extrahepatic Cholangiocarcinoma Patients

The protein 14-3-3δ interacts with Trp53 to maintain G2 arrest and thus regulates the cell cycle. Though dysfunction of 14-3-3δ caused by hyper-methylation of CpG islands was reported in several carcinomas, the exact role of this protein in the development of extrahepatic cholangiocarcinoma has not been fully elucidated. Here, we aim at investigating the clinical relevance between 14-3-3δ and human extrahepatic cholangiocarcinoma. We collected extrahepatic cholangiocarcinoma specimens of 65 patients in Beijing Chao Yang Hospital and evaluated their 14-3-3δ expression using immunohistochemistry. We categorized the patients into different subgroups according to clinic pathological factors, such as sex, age, tumor size, pathological classification, lymph node metastasis status, tumor stage, and serum markers including CEA, CA-242, or CA19-9, and further evaluated the correlation between 14-3-3δ expression and these potential prognostic factors. As a result, we detected 14-3-3δ expression in 53 out of 65 specimens (81.5%), and the expression was positively correlated with TNM stage, lymph node metastasis, and overall survival. Our results suggest that 14-3-3δ serves as an oncogenic driver in extrahepatic cholangiocarcinoma tumorigenesis rather than a cell cycle regulator; the overexpression of 14-3-3δ might be frequently acquired by tumor cells to escape appropriate cell cycle regulation. Thus, 14-3-3δ could be a potential target for extrahepatic cholangiocarcinoma diagnosis and therapy.

Integrated analysis of miRNAs and DNA methylation identifies miR-132-3p as a tumor suppressor in lung adenocarcinoma

BACKGROUND

Aberrant miRNA expression and DNA methylation are two major epigenetic events in lung adenocarcinoma (LUAD). We conducted a combined analysis of the molecular changes in LUAD.

METHODS

We analyzed differentially expressed miRNAs and methylated CpG loci in 489 LUAD tissues versus 49 normal lung tissues of the Cancer Genome Atlas (TCGA). The results were validated in cell lines and xenograft mouse models and additional pairs of 36 LUAD and 36 normal lung tissues.

RESULTS

A total of 125 differentially expressed miRNAs and 145 differentially methylated CpG loci were identified in the LUAD versus normal lung tissues of TCGA data. Expression of the 22 miRNAs was inversely correlated with the 47 differentially methylated sites located in the miRNAs. Molecular and cellular function analysis showed that the abnormally methylated miRNAs were mainly involved in cell-to-cell signaling and interaction in airway cells. The DNA methylation status and altered expressions of miRNAs and their target genes were confirmed in 36 pairs of lung tumor and noncancerous lung tissues. Furthermore, aberrant miRNA expressions or DNA methylations alone could be involved in tumorigenesis of LUAD via different pathways. In addition, elevated miR-132-3p expression, reduced expression of its targeted gene (ZEB2), and decreased cell proliferation was observed in lung cancer cells treated with DNA methyltransferase inhibitor. Moreover, in vitro and in vivo analyses showed that miR-132-3p-3p downregulation via DNA methylation promoted tumorigenicity of lung cancer by directly regulating ZEB2.

CONCLUSIONS

The interaction between two epigenetic aberrations could have important functions in LUAD. miR-132-3p might act as a tumor suppressor in the tumorigenicity of LUAD.

KEY POINTS

SIGNIFICANT FINDINGS OF THE STUDY: Systemically investigating relationship between aberrant miRNA expression and DNA methylation in lung cancer could improve understanding of lung tumorigenesis and develop diagnostic and therapeutic targets.

WHAT THIS STUDY ADDS

Three forms of relationships between the two epigenetic changes are defined. miR-132-3p is further identified as a tumor suppressor in lung cancer.

Wnt-regulating microRNAs role in gastric cancer malignancy

Gastric cancer (GC) is responsible for high morbidity and mortality worldwide. This cancer claims fifth place among other cancers. There are a number of factors associated with GC development such as alcohol consumption and tobacco smoking. It seems that genetic factors play significant role in GC malignancy and progression. MicroRNAs (miRs) are short non-coding RNA molecules with negative impact on the expression of target genes. A variety of studies have elucidated the potential role of miRs in GC growth. Investigation of molecular pathways has revealed that miRs function as upstream modulators of Wnt signaling pathway. This signaling pathway involves in important biological processes such as cell proliferation and differentiation, and its dysregulation is associated with GC invasion. At the present review, we demonstrate that how miRs regulate Wnt signaling pathway in GC malignancy.

The role of YWHAZ in cancer: A maze of opportunities and challenges

YWHAZ (also named 14-3-3ζ) is a central hub protein for many signal transduction pathways and plays a significant role in tumor progression. Accumulating evidences have demonstrated that YWHAZ is frequently up-regulated in multiple types of cancers and acts as an oncogene in a wide range of cell activities including cell growth, cell cycle, apoptosis, migration, and invasion. Moreover, YWHAZ was reported to be regulated by microRNAs (miRNAs) or long non-coding RNAs and exerted its malignant functions by targeting downstream molecules like protein kinase, apoptosis proteins, and metastasis-related molecules. Additionally, YWHAZ may be a potential biomarker of diagnosis, prognosis and chemoresistance in several cancers. Targeting YWHAZ by siRNA, shRNA or miRNA was reported to have great help in suppressing malignant properties of cancer cells. In this review, we perform literature and bioinformatics analysis to reveal the oncogenic role and molecular mechanism of YWHAZ in cancer, and discuss the potential clinical applications of YWHAZ concerning diagnosis, prognosis, and therapy in malignant tumors.

Two-hybrid screening of FAM13A protein partners in lung epithelial cells

OBJECTIVES

Family with sequence similarity 13 member A (FAM13A) genetic variants have been associated with several chronic respiratory diseases including chronic obstructive pulmonary disease (COPD), cystic fibrosis (CF), idiopathic pulmonary fibrosis (IPF) and lung cancer. The FAM13A protein includes a RhoGTPase activating protein (RhoGAP) domain known to participate in various cellular mechanisms including cell proliferation. While intensive genomic studies have been performed to reveal its involvement in lung diseases, the biological role of FAM13A protein is still not completely elucidated.

RESULTS

We therefore performed a two-hybrid screening to identify protein partners of FAM13A using a human lung cancer cDNA library. We identified several protein partners with a high confidence score. Researchers in the field of chronic lung diseases may benefit from this two-hybrid screening data which may reveal new research pathways to decipher.

[14-3-3ζ protein mediates gemcitabine resistance in NK/T-cell lymphoma]

Objective: To explore the molecular mechanisms of 14-3-3ζ in gemcitabine resistance in extranodal NK/T-cell lymphoma, nasal type (ENKTL) . Methods: The effects of cell proliferation and invasion were detected by cell counting kit-8 (CCK-8) assay and transwell assay. YTS cells were exposed to gradually increased concentrations of gemcitabine to establish gemcitabine-resistant YTS cells (YTS-gem) in vitro. 14-3-3ζ specific siRNA lentiviral vector was transfected into YTS and YTS-gem cells to downregulate 14-3-3ζ expression, and stable transfected cell clones were screened. The protein expression was determined by Western blot. Results: ①14-3-3ζ expression was significantly up-regulated in gemcitabine resistant YTS-gem cells, comparing with that of YTS cells (P<0.05) . ②The results of CCK-8 and transwell assay showed that downregulation of 14-3-3ζ significantly reduced the cell proliferation and invasion abilities (P<0.05) . ③Downregulation of 14-3-3ζ could restore gemcitabine sensitivity in gemcitabine resistant YTS-gem cells (P<0.05) . ④Western blotting results showed that knockdown of 14-3-3ζ significantly upregulated pro-apoptotic Bax, and downregulated anti-apoptotic Bcl-2, Caspase-3, cleaved caspase-3, Cyclin D1 in gemcitabine-resistant YTS-gem cells (P<0.05) . There was no significant difference in p53 ang P-gp expression levels. Conclusions: 14-3-3ζ was upregulated in gemcitabine resistant YTS cells. Overexpression of 14-3-3ζ promoted cell proliferation and enhanced cell migration. 14-3-3ζ contributed to gemcitabine resistance to ENKTL through anti-apoptosis.

14-3-3ζ binds to and stabilizes phospho-beclin 1S295 and induces autophagy in hepatocellular carcinoma cells

Data from The Cancer Genome Atlas (TCGA) indicate that the expression levels of 14‐3‐3ζ and beclin 1 (a key molecule involved in cellular autophagy) are up‐regulated and positively correlated with each other (R = .5, P < .05) in HCC tissues. Chemoresistance developed in hepatoma cancer cells is associated with autophagy initiation. This study aimed to explore 14‐3‐3ζ’s role in regulating autophagy in HCC cells, with a focus on beclin 1. The co‐localization of 14‐3‐3ζ and beclin 1 was detectable in primary HCC tissues. To simulate in vivo tumour microenvironment (hypoxia), CSQT‐2 and HCC‐LM3 cells were exposed to 2% oxygen for 24 hours. The protein levels of 14‐3‐3ζ and phospho‐beclin 1^S295 peaked at 12 hours following hypoxia. Meanwhile, the strongest autophagy flux occurred: LC3II was increased, and p62 was decreased significantly. By sequencing the coding area of BECN 1 gene of CSQT‐2 and HCC‐LM3 cells, we found that the predicted translational products of BECN 1 gene contained RLPS²⁹⁵VP (R, arginine; L, leucine; P, proline; S, serine; V, valine), a classic 14‐3‐3ζ binding motif. CO‐IP results confirmed that 14‐3‐3ζ bound to beclin 1, and this connection was markedly weakened when S²⁹⁵ was mutated into A²⁹⁵ (alanine). Further, 14‐3‐3ζ overexpression prevented phospho‐beclin 1^S295 from degradation and enhanced its binding to VPS34, whilst its knockdown accelerated the degradation. Additionally, 14‐3‐3ζ enhanced the chemoresistance of HCC cells to cis‐diammined dichloridoplatium by activating autophagy. Our work reveals that 14‐3‐3ζ binds to and stabilizes phospho‐beclin 1^S295 and induces autophagy in HCC cells to resist chemotherapy.

YWHAZ amplification/overexpression defines aggressive bladder cancer and contributes to chemo-/radio-resistance by suppressing caspase-mediated apoptosis

The objective of this study was to characterize the oncogenic actions of a recently identified cancer‐associated gene YWHAZ (also named as 14‐3‐3 ζ/δ) in urothelial carcinomas of the urinary bladder (UCUB). A genome‐wide study revealed YWHAZ to be involved in the amplicon at 8q22.3, and its genetic amplification was detected predominantly in muscle‐invasive bladder cancer (MIBC). Immunohistochemical staining confirmed the association of YWHAZ overexpression with higher tumor stages, lymph node/vascular invasion, and mitotic activity. Univariate and multivariate analyses further indicated the prognostic potential of YWHAZ for more aggressive cancer types. Both gene set enrichment analysis and STRING network studies suggested involvement of YWHAZ in regulating caspase‐mediated apoptosis. Ectopic expression of YWHAZ in bladder cells with low endogenous YWHAZ levels boosted cell resistance to doxorubicin and cisplatin, as well as to ionizing radiation. Conversely, YWHAZ‐knockdown using specific shRNA in cells with high endogenous YWHAZ levels diminished survival activity, suppressing cell growth and increasing cell death. Our findings confirm the essential role played by YWHAZ in sustaining cell proliferation during chemo/radiotherapy. Treatments based on anti‐YWHAZ strategies may thus be beneficial for UCUB patients overexpressing YWHAZ. © 2019 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

miR-375-3p/YWHAZ/β-catenin axis regulates migration, invasion, EMT in gastric cancer cells

YWHAZ (14-3-3ζ) plays crucial roles in regulating proliferation, apoptosis, migration, and invasion of gastric cancer (GC) cells. However, its extensive roles and potential mechanisms in GC cells remain unknown, and need to be researched deeply. In this study, we focus on the role of miR-375/YWHAZ axis in migration, invasion and epithelial-to-mesenchymal transition (EMT) of GC cells. YWHAZ level was assessed by western blot and qPCR assays in GC cells. Scratch and transwell assays were used to determine the migration and invasion of GC cells. The protein levels of correlative molecules were detected by western blot. The regulation of miR-375 on the expression of its target gene YWHAZ was verified by dual-luciferase report system. According to the results, knockdown of YWHAZ inhibited the migration, invasion and EMT of GC cells. Moreover, silencing of YWHAZ restrained the activation of wnt/β-catenin signalling pathway. YWHAZ was confirmed to be a target gene of miR-375, and its expression was regulated by miR-375 in GC cells. Transfection of miR-375 inhibitor promoted the migration, invasion, EMT and activation of wnt/β-catenin pathway in GC cells, which was suppressed by inhibition of YWHAZ. Taken together, this study suggests that miR-375/YWHAZ axis may be served as a novel therapeutic target for GC patients.

The dynamic and stress-adaptive signaling hub of 14-3-3: emerging mechanisms of regulation and context-dependent protein-protein interactions

14-3-3 proteins are a family of structurally similar phospho-binding proteins that regulate essentially every major cellular function. Decades of research on 14-3-3s have revealed a remarkable network of interacting proteins that demonstrate how 14-3-3s integrate and control multiple signaling pathways. In particular, these interactions place 14-3-3 at the center of the signaling hub that governs critical processes in cancer, including apoptosis, cell cycle progression, autophagy, glucose metabolism, and cell motility. Historically, the majority of 14-3-3 interactions have been identified and studied under nutrient-replete cell culture conditions, which has revealed important nutrient driven interactions. However, this underestimates the reach of 14-3-3s. Indeed, the loss of nutrients, growth factors, or changes in other environmental conditions (e.g., genotoxic stress) will not only lead to the loss of homeostatic 14-3-3 interactions, but also trigger new interactions, many of which are likely stress adaptive. This dynamic nature of the 14-3-3 interactome is beginning to come into focus as advancements in mass spectrometry are helping to probe deeper and identify context-dependent 14-3-3 interactions-providing a window into adaptive phosphorylation-driven cellular mechanisms that orchestrate the tumor cell's response to a variety of environmental conditions including hypoxia and chemotherapy. In this review, we discuss emerging 14-3-3 regulatory mechanisms with a focus on post-translational regulation of 14-3-3 and dynamic protein-protein interactions that illustrate 14-3-3's role as a stress-adaptive signaling hub in cancer.

Effect of cytokine-induced killer cells combined with dendritic cells on the survival rate and expression of 14-3-3ζ and p-Bad proteins in Lewis lung cancer cell lines

In the present study, the function and mechanism of cytokine-induced killer cells (CIK) combined with dendritic cells (DC-CIK) were examined in Lewis lung cancer (LLC) cells. Co-culture of CIK dendritic cells (DC) in vitro was used to investigate their proliferation and the antitumor effects on LLC cells. DC and CIK cells were collected from healthy human peripheral blood mononuclear cells and co-cultured as an experimental group, while LLC cells were cultured alone as a control group. Cell morphology was observed by an inverted microscope and an MTT assay was utilized to detect the proliferation of LLC cells. Expression of 14-3-3ζ and p-Bad were measured by western blot analysis. Compared with the control group, treatment of LLC cells with DC-CIK resulted in decreased cell adherence, reduced cell proliferation and abnormal morphological changes. Additionally, DC-CIK treatment of LLC cells resulted in the decreased expression of 14-3-3ζ and p-Bad protein in LLC cells, which may provide important information pertaining to the possible mechanism of DC-CIK-induced antitumor activity against LLC cells. The present study provides a theoretical and experimental basis for the clinical treatment of DC-CIK cell co-culture.

Overexpression of 14-3-3ζ in lung tissue predicts an improved outcome in patients with lung adenocarcinoma

One of the factors limiting the survival rate of patients with lung cancer is the high risk for recurrence following surgical resection. Previous studies indicate that 14-3-3ζ is a central cellular hub protein that regulates multiple signaling pathways involved in cancer progression. The present study evaluated the prognostic significance of 14-3-3ζ in patients with lung adenocarcinoma. The expression of 14-3-3ζ and E-cadherin, an important protein involved in the epithelial-mesenchymal transition, was evaluated by immunohistochemistry in lung tumor tissues and adjacent normal lung tissues resected from 123 patients with lung adenocarcinoma. The correlation between the two proteins, their association with clinicopathological features and their prognostic significance were subsequently analyzed. Within these parameters, an overall survival (OS) prediction model was constructed using multivariate Cox proportional hazards regression. The expression of 14-3-3ζ was upregulated in lung adenocarcinoma, in contrast to E-cadherin, which was downregulated in lung adenocarcinoma tissues compared with normal tissues. In addition, the expression of 14-3-3ζ was positively correlated with that of E-cadherin (r=0.256, P=0.012) and differentiation (P<0.001). Increased E-cadherin expression was indicative of smaller tumor size and greater differentiation, and the overexpression of 14-3-3ζ and E-cadherin were associated with longer OS (P=0.010 and P=0.006, respectively). Finally, a multivariate analysis revealed that TNM stage and 14-3-3ζ were independent prognostic indicators (P<0.001 and P=0.026, respectively). 14-3-3ζ may function as a tumor suppressor associated with E-cadherin upregulation and could be used as a prognostic biomarker for resected lung adenocarcinoma. These findings provide a novel insight on potential intervention strategies for patients with lung cancer.

The ASH1-miR-375-YWHAZ Signaling Axis Regulates Tumor Properties in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is a worldwide malignance, and the underlying mechanisms of this disease are not fully elucidated. In this study, the existence and function of achaete-scute homolog-1 (ASH1)-miR-375-YWHAZ signaling axis in HCC were determined. Our experiments and the Cancer Genome Atlas (TCGA) sequencing data analyses showed that ASH1 and miR-375 were significantly downregulated, whereas YWHAZ was significantly upregulated in HCC. Furthermore, we found that ASH1 positively regulates miR-375, and miR-375 directly downregulates its target YWHAZ. Gain- and loss-of-function study demonstrated ASH1 and miR-375 function as tumor suppressors, whereas YWHAZ acts as an oncogene in HCC. Animal experiment indicated that YWHAZ small interfering RNAs (siRNAs) (si-YWHAZ) delivered by nanoliposomes could suppress the growth of hepatoma xenografts and was well tolerant by nude mice. Further studies revealed that YWHAZ was involved in several protein networks, such as cell autophagy, epithelial-mesenchymal transition (EMT), apoptosis, cell cycle, invasion, and migration. In addition, the patient group with ASH1-high-expression-miR-375-high-expression-YWHAZ-low-expression was correlated with a better clinical prognosis compared with the opposite expression group. In conclusion, we proved the existence of ASH1-miR-375-YWHAZ signaling axis and interpreted its important role in driving HCC tumor progression.

A 16-gene expression signature to distinguish stage I from stage II lung squamous carcinoma

The present study aimed to perform screening of a gene signature for the discrimination and prognostic prediction of stage I and II lung squamous carcinoma. A microarray meta‑analysis was performed to identify differentially expressed genes (DEGs) between stage I and II lung squamous carcinoma samples in seven microarray datasets collected from the Gene Expression Omnibus database via the MetaQC and MetaDE package in R. The important DEGs were selected according to the betweenness centrality value of the protein‑protein interaction (PPI) network. Support vector machine (SVM) analysis was performed to screen the feature genes for discrimination and prognosis. One independent dataset downloaded from The Cancer Genome Atlas was used to validate the reliability. Pathway enrichment analysis was also performed for the feature genes. A total of 924 DEGs were identified to construct a PPI network consisting of 392 nodes and 686 edges. The top 100 of the 392 nodes were selected as crucial genes to construct an SVM classifier, and a 16‑gene signature (caveolin 1, eukaryotic translation elongation factor 1γ, casein kinase 2α1, tyrosine 3-monooxygenase/tryptophan 5-monooxygenase activation η, tyrosine 3‑monooxygenase/tryptophan 5‑monooxygenase activation θ, pleiotrophin, insulin receptor, insulin receptor substrate 1, 3‑phosphoinositide‑dependent protein kinase‑1, specificity protein 1, COP9 signalosome subunit 6, N‑myc downstream regulated gene 1, retinoid X receptor α, heat shock protein 90α A1, karyopherin subunit β1 and erythrocyte membrane protein band 4.1) with high discrimination accuracy was identified. This 16‑gene signature had significant prognostic value, and patients with stage II lung squamous carcinoma exhibited shorter survival rates, compared with those with stage I disease. Seven DEGs of the 16-gene signature were significantly involved in the phosphoinositide 3‑kinase‑Akt signaling pathway. The 16‑gene signature identified in the present study may be useful for stratifying the patients with stage I or II lung squamous carcinoma and predicting prognosis.

14-3-3ζ/TGFβR1 promotes tumor metastasis in lung squamous cell carcinoma

14-3-3ζ is involved in tumor cell growth and apoptosis. However, the mechanism of 14-3-3ζ in lung squamous cell carcinoma (SCC) metastasis has not been illuminated. In our studies, we found that the expression of 14-3-3ζ was highly expressed in lung SCC compared to normal lung tissues. High expression of 14-3-3ζ was associated with pTNM stage (p<0.05) and lymph node metastasis (p<0.05). Furthermore, the expression of 14-3-3ζ protein was associated with high levels of TGFβR1 protein (p=0.005), and pSMAD3 (p=0.033). Lung SCC patients with high 14-3-3ζ expression have significantly shorter OS and DFS compared to patients with low 14-3-3ζ expression. Additionally, 14-3-3ζ knockdown inhibited cell proliferation, migratory and invasive properties of human lung SCC cells. TGFβR1 was involved in 14-3-3ζ-mediated cell proliferation and metastasis of lung SCC cells. Additionally, sh-14-3-3ζ can suppress tumor growth and metastasis in vivo. Thus, these data provide the evidence that 14-3-3ζ promote tumor metastasis and might be a prognostic biomarker and target for therapeutic strategy in lung SCC.

14-3-3ζ and aPKC-ι synergistically facilitate epithelial-mesenchymal transition of cholangiocarcinoma via GSK-3β/Snail signaling pathway

Cholangiocarcinoma (CCA) invasion and metastasis are the primary causes of poor survival rates in patients. The epithelial-mesenchymal transition (EMT) is a crucial step in cancer invasion and metastasis. However, it is still unclear of the molecular mechanism. In this study, the expression of 14-3-3ζ and atypical protein kinase C-ι (aPKC-ι) was further detected in CCA tissues and cell lines. Meanwhile, we established the EMT model of CCA cells and investigated 14-3-3ζ and aPKC-ι co-regulatory effect on the EMT in vitro and in vivo. Further, we identified the downstream molecular glycogen synthase kinase 3 beta (GSK-3β)/Snail signalling pathway that contribute to regulating the EMT. Our data showed that the expression of 14-3-3ζ and aPKC-ι was synergistically increased in CCA tissues compared with adjacent noncancerous tissues and was intimately associated with differentiation and the tumour-node-metastasis (TNM) stage. Multivariate Cox regression analysis indicated that high 14-3-3ζ and aPKC-ι expression separately predicted a poor prognosis and were independent prognostic indicators in patients with CCA. The CO-IP experiment confirmed that the mutual binding relationship between 14-3-3ζ and aPKC-ι. Small interfering RNAs and siRNA rescue experiment demonstrated that 14-3-3ζ and aPKC-ι regulated each other. In addition, 14-3-3ζ and aPKC-ι pretreatment by si-RNA inhibit the phosphorylated GSK-3β and Snail expression during EMT. Meanwhile, silence of 14-3-3ζ or aPKC-ι suppressed CCA cells migration, metastasis and proliferation in vitro and in vivo. Our study demonstrates that 14-3-3ζ and aPKC-ι synergistically facilitate EMT of CCA via GSK-3β/Snail signalling pathway, and may be potential therapeutic target for CCA.

Suppression of 14-3-3ζ in cholangiocarcinoma cells inhibits proliferation through attenuated Akt activity, enhancing chemosensitivity to gemcitabine

The protein 14-3-3ζ contributes important regulatory functions in several cellular processes via binding to phosphorylated serine/threonine residues, which promotes cell cycle progression, cell proliferation and anti-apoptosis in multiple types of cancer. The aim of the present study was to investigate the functions of 14-3-3ζ in cholangiocarcinoma (CCA) progression and elucidate the molecular mechanism of 14-3-3ζ expression-mediated protein kinase B (Akt) phosphorylation and chemosensitivity in CCA cells. In the present study, 14-3-3ζ expression was investigated in clinical specimens using immunohistochemistry and compared with the clinicopathological features of patients with CCA. The association between 14-3-3ζ and phosphorylated Akt (pAkt) was determined among the tissues of the same patients using bivariate correlation analysis. The effects of 14-3-3ζ suppression on CCA cell function and gemcitabine sensitivity were investigated using small interfering RNA (siRNA). It was identified that 14-3-3ζ expression was positively correlated with pAkt (P=0.013) and that increased expression of 14-3-3ζ and pAkt were significantly associated with poor overall survival rate and metastasis (P=0.025 and 0.006, respectively). Downregulation of 14-3-3ζ using siRNA in CCA cell lines decreased cell proliferation, resulting in the inhibition of pAkt activity and increasing the protein level of the cell cycle inhibitor p27. The suppression of 14-3-3ζ enhanced the inhibitory effect of gemcitabine on CCA cell proliferation by inducing apoptotic cell death. Taken together, the results of the present study indicated that 14-3-3ζ is a potential target for CCA and may serve as a novel therapeutic approach to enhance chemosensitivity in the treatment of CCA.

14-3-3ζ Overexpression is Associated with Poor Prognosis in Ovarian Cancer

PURPOSE

14-3-3ζregulates cell signaling, cell cycle progression, and apoptosis, and its overexpression is associated with disease recurrence and poor clinical outcomes in some solid tumors. However, its clinicopathological role in ovarian cancer is unknown. Our goal was to investigate whether 14-3-3ζis associated with ovarian cancer prognosis.

MATERIALS AND METHODS

We examined 14-3-3ζexpression by immunohistochemistry in ovarian cancer tissues obtained from 88 ovarian cancer patients. The examined tissues were of various histologies and stages. 14-3-3ζexpression was also analyzed by western blot in seven ovarian cancer cell lines and a primary ovary epithelial cell line. Cell viability was measured using an MTS-based assay following cisplatin treatment.

RESULTS

Among the ovarian cancer samples, 53.4% (47/88) showed high 14-3-3ζexpression, and 14-3-3ζoverexpression was positively correlated with more advanced pathologic stages and grades. 14-3-3ζoverexpression was also significantly associated with poor disease-free survival (DFS) and overall survival (OS) of ovarian cancer patients. Median DFS and OS were 1088 and 3905 days, respectively, in the high 14-3-3ζexpression group, but not reached in the low 14-3-3ζexpression group (p=0.004 and p=0.033, log-rank test, respectively). Downregulating 14-3-3ζby RNA interference in ovarian cancer cells led to enhanced sensitivity to cisplatin-induced cell death.

CONCLUSION

14-3-3ζoverexpression might be a potential prognostic biomarker for ovarian cancer, and the inhibition of 14-3-3ζcould be a therapeutic option that enhances the antitumor activity of cisplatin.

Identification of 14‑3‑3ζ as a potential biomarker in gastric cancer by proteomics‑based analysis

The identification of tumor biomarkers to support early diagnosis and tumor progression monitoring may potentially reduce the mortality of gastric cancer (GC). The present study aimed to detect novel tumor‑associated antigens from the AGS GC cell line, and to identify their associated autoantibodies in sera from patients with GC by proteomics‑based approaches. Proteins from AGS cell lysates were isolated using two‑dimensional polyacrylamide gel electrophoresis, and western blotting was subsequently performed, to determine autoantibody responses in sera derived from patients with GC and healthy individuals. Positive protein spots were removed from gels stained with Coomassie blue, and were then evaluated by liquid chromatography‑tandem mass spectrometry. Sera from patients with GC produced numerous spots, one of which was identified as 14‑3‑3ζ. Autoantibody frequency to 14‑3‑3ζ was 17.6% (15/85) in patients with GC, which was significantly higher than that in healthy control individuals (2.4%; 2/85; P<0.01). These results suggested that the autoantibody against 14‑3‑3ζ may be a potential serological biomarker for the detection and diagnosis of GC.

The functional significance of 14-3-3 proteins in cancer: focus on lung cancer

The 14-3-3 family proteins are phosphoserine/phosphothreonine binding proteins constituting a conserved class of proteins which are detected in all eukaryotic cells. In mammalians, 14-3-3 proteins have seven distinct isoforms (β, γ, ε, η, ζ, σ and τ/θ) which are involved in various cellular processes including signal transduction, cell cycle, cell proliferation, apoptosis, differentiation and survival. 14-3-3 proteins do not have a distinct catalytic activity and often regulate the activity, stability, subcellular localization and interactions of other proteins. The 14-3-3 family proteins function through interacting with their client proteins or facilitating the interaction of other proteins likely as adaptor proteins. The versatile functions of these proteins in the regulation of cell growth, cell division, cell death and cell migration make them candidate proteins for which an important role in cancer development could be envisioned. Indeed, analysis of cancer cell lines and tumor-derived tissues have indicated the differential abundance or post-translational modification of some 14-3-3 isoforms. In this review, we aimed to show how deregulation of 14-3-3 proteins contributes to initiation, establishment and progression of cancers with a particular emphasis on lung cancer. The role of these proteins in cancer-relevant processes including cell cycle, cell migration, cell-cell communication and programmed cell death will be discussed in detail.

14-3-3β Depletion Drives a Senescence Program in Glioblastoma Cells Through the ERK/SKP2/p27 Pathway

The induction of senescence in cancer cells has recently been implicated as a mechanism of tumor regression in response to various modes of stress. 14-3-3 proteins are conserved scaffolding molecules that are involved in various cellular functions. Among the seven isoforms, 14-3-3β is specifically expressed in astrocytoma in correlation with the malignancy grade. We investigated the possible role of 14-3-3β in the regulation of senescence induction in A172 glioblastoma cells. The knockdown of 14-3-3β by specific small interfering RNA resulted in a significant change in cellular phenotypes and an increase in cells staining positive for senescence-associated β-galactosidase. Western blotting of the 14-3-3β-depleted A172 cells revealed increased p27 expression and decreased SKP2 expression, while the expression of p53 and p21 was not altered. Subsequently, we demonstrated that ERK is a key modulator of SKP2/p27 axis activity in 14-3-3β-mediated senescence based on the following: (1) 14-3-3β knockdown decreased p-ERK levels; (2) treatment with U0126, an MEK inhibitor, completely reproduced the senescence morphology as well as the expression profiles of p27 and SKP2; and (3) the senescence phenotypes induced by 14-3-3β depletion were considerably recovered by constitutively active ERK expression. Our results indicate that 14-3-3β negatively regulates senescence in glioblastoma cells via the ERK/SKP2/p27 pathway. Furthermore, 14-3-3β depletion also resulted in senescence phenotypes in U87 glioblastoma cells, suggesting that 14-3-3β could be targeted to induce premature senescence as a therapeutic strategy against glioblastoma progression.

MicroRNA-206 attenuates the growth and angiogenesis in non-small cell lung cancer cells by blocking the 14-3-3ζ/STAT3/HIF-1α/VEGF signaling

Non-small cell lung cancer (NSCLC) is the leading cause of cancer-related mortality worldwide. Angiogenesis is the major hallmark in NSCLC. So, further elucidation of molecular mechanisms underlying the angiogenesis of NSCLC is urgently needed. Here, we found that microRNA-206 (miR-206) decreased the angiogenic ability in NSCLC via inhibiting the 14-3-3ζ/STAT3/HIF-1α/VEGF pathway. Briefly, 14-3-3ζ bond with phosphorylated-STAT3, and in turn, elevated the expression of HIF-1α. Then, by enhancing the recruitment of HIF-1α to VEGF promoter, 14-3-3ζ increased the angiogenesis. However, miR-206 decreased the angiogenesis by targeting 14-3-3ζ, and inhibiting the STAT3/HIF-1α/VEGF pathway. In NSCLC cell xenograft model, either overexpression of miR-206 or inhibition of 14-3-3ζ inhibited the STAT3/HIF-1α/VEGF pathway and decreased the tumor growth and angiogenesis. Furthermore, there was a negative correlation between miR-206 and 14-3-3ζ in NSCLC specimens. NSCLC patients with low expressions of miR-206 but high expressions of 14-3-3ζ had the worst survival. Collectively, our findings provided the underlying mechanisms of miR-206/14-3-3ζ in tumor growth and angiogenesis, and implicated miR-206 and 14-3-3ζ as potential therapeutic targets for NSCLC.

Identification of 14-3-3zeta associated protein networks in oral cancer

Advancements in genomics, proteomics, and bioinformatics have improved our understanding of gene/protein networks involved in intra- and intercellular communication and tumor-host interactions. Using proteomics integrated with bioinformatics, previously we reported overexpression of 14-3-3ζ in premalignant oral lesions and oral squamous cell carcinoma tissues in comparison with normal oral epithelium. 14-3-3ζ emerged as a novel molecular target for therapeutics and a potential prognostic marker in oral squamous cell carcinoma patients. However, the role of 14-3-3ζ in development and progression of oral cancer is not known yet. This study aimed to identify the 14-3-3ζ associated protein networks in oral cancer cell lines using IP-MS/MS and bioinformatics. A total of 287 binding partners of 14-3-3ζ were identified in metastatic (MDA1986) and nonmetastatic (SCC4) oral cancer cell lines including other 14-3-3 isoforms (2%), proteins involved in apoptosis (2%), cytoskeleton (9%), metabolism (16%), and maintenance of redox potential (2%). Our bioinformatics analysis revealed involvement of 14-3-3ζ in protein networks regulating cell cycle, proliferation, apoptosis, cellular trafficking, and endocytosis in oral cancer. In conclusion, our data revealed several novel protein interaction networks involving 14-3-3ζ in oral cancer progression and metastasis.

14-3-3ζ reduces DNA damage by interacting with and stabilizing proliferating cell nuclear antigen

Proliferating cell nuclear antigen (PCNA) is a processivity factor of DNA replication which plays critical roles in the regulation of DNA replication and repair. In this study, we show that PCNA interacts directly in vitro and in cells with 14-3-3ζ, an adaptor protein that regulates cell growth and response to DNA damage in eukaryotes. The interaction is mediated by at least two PCNA-binding sites on 14-3-3ζ, one of which is a novel non-canonical PIP (PCNA interacting protein) box. We find that DNA damages induced by UVC irradiation and MMS (methyl methanesulfonate) can enhance both the interaction of these two proteins and their co-localization with chromatin. Functional analyses suggest that 14-3-3ζ stabilizes PCNA possibly by regulating its ubiquitination, which impacts on DNA damage repair and cell viability.

Destabilisation of dimeric 14-3-3 proteins as a novel approach to anti-cancer therapeutics

14-3-3 proteins play a pivotal role in controlling cell proliferation and survival, two commonly dysregulated hallmarks of cancers. 14-3-3 protein expression is enhanced in many human cancers and correlates with more aggressive tumors and poor prognosis, suggesting a role for 14-3-3 proteins in tumorigenesis and/or progression. We showed previously that the dimeric state of 14-3-3 proteins is regulated by the lipid sphingosine, a physiological inducer of apoptosis. As the functions of 14-3-3 proteins are dependent on their dimeric state, this sphingosine-mediated 14-3-3 regulation provides a possible means to target dimeric 14-3-3 for therapeutic effect. However, sphingosine mimics are needed that are not susceptible to sphingolipid metabolism. We show here the identification and optimization of sphingosine mimetics that render dimeric 14-3-3 susceptible to phosphorylation at a site buried in the dimer interface and induce mitochondrial-mediated apoptosis. Two such compounds, RB-011 and RB-012, disrupt 14-3-3 dimers at low micromolar concentrations and induce rapid down-regulation of Raf-MAPK and PI3K-Akt signaling in Jurkat cells. Importantly, both RB-011 and RB-012 induce apoptosis of human A549 lung cancer cells and RB-012, through disruption of MAPK signaling, reduces xenograft growth in mice. Thus, these compounds provide proof-of-principle for this novel 14-3-3-targeting approach for anti-cancer drug discovery.

14-3-3 isoforms bind directly exon B of the 5'-UTR of human surfactant protein A2 mRNA

Human surfactant protein (SP) A (SP-A), an innate immunity molecule, is encoded by two genes, SFTPA1 and SFTPA2. The 5'-untranslated splice variant of SP-A2 (ABD), but not SP-A1 (AD), contains exon B (eB). eB is an enhancer for transcription and translation and contains cis-regulatory elements. Specific trans-acting factors, including 14-3-3, bind eB. The 14-3-3 protein family contains seven isoforms that have been found by mass spectrometry in eB electromobility shift assays (Noutsios et al. Am J Physiol Lung Cell Mol Physiol 304: L722-L735, 2013). We used four different approaches to investigate whether 14-3-3 isoforms bind directly to eB. 1) eB RNA pulldown assays showed that 14-3-3 isoforms specifically bind eB. 2) RNA electromobility shift assay complexes were formed using purified 14-3-3 isoforms β, γ, ε, η, σ, and τ, but not isoform ζ, with wild-type eB RNA. 3 and 4) RNA affinity chromatography assays and surface plasmon resonance analysis showed that 14-3-3 isoforms β, γ, ε, η, σ, and τ, but not isoform ζ, specifically and directly bind eB. Inhibition of 14-3-3 isoforms γ, ε, η, and τ/θ with shRNAs in NCI-H441 cells resulted in downregulation of SP-A2 levels but did not affect SP-A1 levels. However, inhibition of 14-3-3 isoform σ was correlated with lower levels of SP-A1 and SP-A2. Inhibition of 14-3-3 isoform ζ/δ, which does not bind eB, had no effect on expression levels of SP-A1 and SP-A2. In conclusion, the 14-3-3 protein family affects differential regulation of SP-A1 and SP-A2 by binding directly to SP-A2 5'-UTR mRNA.

Up-regulation of 14-3-3ζ expression in intrahepatic cholangiocarcinoma and its clinical implications

The 14-3-3 proteins are highly conserved molecules that are involved in many vital biologic processes and are associated with the progression of cancer. The role of 14-3-3ζ, a dimeric isoform of 14-3-3, in intrahepatic cholangiocarcinoma (ICC) was investigated in this study. The expression of 14-3-3ζ in tumour samples from patients with ICC was examined by Western blot and immunohistochemistry, and the correlation between its expression and various clinicopathological features was determined. Then, the capacity for invasion, migration and proliferation as well as the expression of epithelial-mesenchymal transition (EMT)-related markers in ICC cells were assessed after 14-3-3ζ depletion. Finally, the prognostic significance of 14-3-3ζ in patients with ICC was further evaluated by Kaplan-Meier and Cox regression analyses. The expression of 14-3-3ζ was significantly higher in ICC tissues compared to peritumoural tissues. High expression of 14-3-3ζ positively correlated with lymphatic metastasis and tumour-node-metastasis (TNM) stage. The inhibition of 14-3-3ζ expression was able to impair the invasion, migration and proliferation of ICC cells in vitro. The expression of 14-3-3ζ was significantly correlated with the expression of the EMT-related markers snail and E-cadherin in ICC samples. Moreover, the down-regulation of 14-3-3ζ also decreased the phosphorylation of extracellular signal-regulated kinase (ERK) in ICC cells. Clinically, patients with ICC with high 14-3-3ζ expression demonstrated a poor prognosis in terms of a short overall survival and a high recurrence rate of the disease. A multivariate analysis revealed that 14-3-3ζ overexpression was an independent prognostic indicator for patients with ICC. 14-3-3ζ may enhance the invasive and proliferative capacity of tumour cells and thus prompt the progression of ICC via the activation of ERK signalling and the induction of EMT. The overexpression of 14-3-3ζ may be used as a prognostic biomarker and therapeutic target in patients with ICC.

p53 suppresses 14-3-3γ by stimulating proteasome-mediated 14-3-3γ protein degradation

14-3-3 proteins are a family of highly conserved polypeptides that interact with a large number of proteins and play a role in a wide variety of cellular processes. 14-3-3 proteins have been demonstrated overexpressed in several cancers and serving as potential oncogenes. In a previous study we showed one isoform of the 14-3-3 family, 14-3-3γ was negatively regulated by p53 through binding to its promoter and inhibiting its transcription. In the present study we investigated both p53 and 14-3-3γ protein levels in human lung cancerous tissues and normal lung tissues. We found 14-3-3γ expression correlated to p53 overexpression in lung cancer tissues. Ecotopic expression of wild-type p53, but not mutant p53 (R175H) suppressed both endogenous and exogenous 14-3-3γ in colon and lung cancer cell lines. Further examination demonstrated that p53 interacted with C-terminal domain of 14-3-3γ and induced 14-3-3γ ubiquitination. MG132, a specific inhibitor of the 26S proteasome, could block the effect of p53 on 14-3-3γ protein levels, suggesting that p53 suppressed 14-3-3γ by stimulating the process of proteasome-mediated degradation of 14-3-3γ. These results indicate that the inhibitory effect of p53 on 14-3-3γ is mediated also by a post-transcriptional mechanism. Loss of p53 function may result in upregulation of 14-3-3γ in lung cancers.

Prognostic significance of YWHAZ expression in localized prostate cancer

BACKGROUND

Prostate cancer (PCa) patients are often over-treated because of the lack of biomarkers needed to distinguish the lethal from the indolent form of PCa. YWHAZ was recently identified as a potential therapeutic target in castration-resistant PCa (CRPC). Therefore, this study focused on determining the prognostic significance of YWHAZ in localized PCa.

METHODS

YWHAZ expression was assessed by immunohistochemistry on formalin-fixed paraffin-embedded tissue from 213 men who underwent radical prostatectomy. Kaplan-Meier analysis and Cox proportional-hazards models were used to assess the prognostic value of YWHAZ intensity.

RESULTS

High YWHAZ expression was strongly associated with high Gleason score at the time of diagnosis (P < 0.001) and PSA relapse (P = 0.001). Importantly, patients with high expression of YWHAZ had a higher risk of CRPC development (P = 0.002) and reduced survival time (P = 0.002).

CONCLUSIONS

Our findings indicate that YWHAZ could serve as a promising prognostic biomarker in localized PCa to predict poor prognosis and to identify a subgroup of tumors, which might benefit from earlier adjuvant or YWHAZ-targeted therapy.

Direct interaction of 14-3-3ζ with ezrin promotes cell migration by regulating the formation of membrane ruffle

14-3-3 proteins have been shown to regulate the actin cytoskeleton remodeling, cell adhesion and migration. In this study, we identified ezrin, a cross-linker between plasma membrane and actin cytoskeleton, as a novel 14-3-3ζ interacting partner. The direct interaction between 14-3-3ζ and ezrin was validated in the cells and by in vitro assays. We showed that the 14-3-3ζ binding region in ezrin was located within the N-terminal and central α-helical domains and that the αG-to-αI helices of 14-3-3ζ are responsible for the binding to ezrin. Functional analyses revealed that the regulation of cell migration and membrane ruffling by 14-3-3ζ is ezrin dependent, for which the integrity of ezrin protein was required. Conversely, the knockdown of 14-3-3ζ abrogates also the stimulatory effect of ezrin on cell migration and membrane ruffling. Moreover, we found that the phosphorylation of Thr567 in ezrin facilitates the 14-3-3ζ-ezrin interaction and the formation of membrane ruffles. Taken together, these results suggest strongly that the functions of these two proteins in cell migration are linked and might be mediated by their direct physical interaction, which is important for the formation of membrane ruffles.

Small nucleolar RNA signatures of lung tumor-initiating cells

Background

Non-small cell lung cancer (NSCLC) is the number one cancer killer. Tumor-initiating cells (TICs) are responsible for tumor progression and recurrence. Emerging evidences suggest that small nucleolar RNAs (snoRNAs) play malfunctioning roles in lung tumorigenesis. This study aims to determine if snoRNAs have important function in lung TICs by: 1) profiling and comparing snoRNA expression patterns in lung ALDH1+/- cells of 28 primary NSCLC tissues to identify new signatures of TICs; 2) determining prognostic significance of the snoRNA signatures by analyzing the expression in 82 NSCLC tissues with different stages and histological types using quantitative PCR; 3) functionally investigating if the snoRNAs contribute to stemness of lung TICs using in vitro and in vivo assays.

Results

Twenty-two snoRNAs were identified whose changes were specific to the TICs. The expression of two snoRNAs (snoRA3 and snoRA42) was inversely associated with survival of NSCLC patients (P = 0.002, p = 0.001, respectively). Functional analysis indicated that snoRA42 was upregulated in CD133+ cells isolated from NSCLC cell lines compared with the CD133- counterparts. snoRA42 knockdown reduced the proliferation and self-renewal of TICs in vitro. However, ectopic expression of snoRA42 in non-TICs enhanced the potentials of cell proliferation and self-renewal. snoRA42 expression was associated with expression of stem cell-core transcription factors in lung TICs. Blocking snoRA42 expression in TIC xenografts decreased tumorigenesis in mice.

Conclusions

The snoRNA signatures of lung TICs provide potential biomarkers for predicting outcome of NSCLC. snoRA42 is one of the important snoRNAs in regulating features of lung TICs, and thus contributes to lung tumorigenesis.

Gene cloning, expression, and function analysis of SpL14-3-3ζ in Spodoptera litura and its response to the entomopathogenic fungus Nomuraea rileyi

The 14-3-3 proteins, a highly evolutionarily conserved and ubiquitous protein family in eukaryotic cells, have a range of biological functions including regulation of signal transduction, stress response, apoptosis, and control of the cell cycle. To investigate the function of 14-3-3 in Spodoptera litura, the full length of 14-3-3ζ was cloned from S. litura on the basis of an expressed sequence tag of 14-3-3ζ from the S. litura fat body suppression subtractive hybridization library, and named SpL14-3-3ζ. SpL14-3-3ζ cDNA was 1196 bp with an open reading frame of 744 bp, encoding 247 amino acids. Multiple alignment analysis revealed the putative amino acids shared >80% homology with 14-3-3ζ from other organisms and shared typical conservative structures. Phylogenetic analysis confirmed SpL14-3-3ζ was closely related to other available Lepidoptera 14-3-3ζ. Real-time PCR analysis indicated SpL14-3-3ζ was expressed throughout the developmental stages of S. litura, with a relatively high expression level in pre-pupa, and was expressed constitutively in all examined tissues with relatively high levels in hemocytes and midgut. Moreover, the transcription level of SpL14-3-3ζ could be induced by Nomuraea rileyi infection, up-regulated in hemocytes, followed by head, fat body and midgut. Knocking down SpL14-3-3ζ transcripts by RNAi significantly increased S. litura sensitivity to fungal infection, and resulted in higher mortality of S. litura during the larval development. These results provide novel insights into the 14-3-3ζ signal regulation which may be related to host defense as well as larval development in S. litura.

Transcriptional regulation of YWHAZ, the gene encoding 14-3-3ζ

Aberrant expression of oncogenic 14-3-3 proteins is correlated with poor survival of cancer patients. While the underlying mechanism of the abnormal expression in tumors remains elusive for the six oncogenic 14-3-3 isoforms; the potential involvement of a transcriptional component has been suggested. Unfortunately, little experimental data has been reported to support this hypothesis. In this study we describe the genetic structure of YWHAZ, the gene encoding 14-3-3ζ, including the identification of previously unreported transcript variants. In total, five transcript variants were revealed and their expressions confirmed in a panel of cell lines. Expressed sequence tag (EST) database mining and in vitro rapid-amplification of cDNA ends (RACE) confirmed that one variant, 1c, represents >80% of the expressed transcripts, which is also the most efficiently translated. An analysis of the proximal promoter of this variant revealed a functional Cyclic-AMP Response Element (CRE). Factors that bound to the CRE element were recognized through fractionation and subsequent EMSAs. This analysis identified CREB and ATF-1 as the trans-interacting factors. Cell-based assays confirm that ATF-1, and to a lesser extent CREB, bind the endogenous YWHAZ promoter especially under TNF-α stimulating conditions. In support of a role of ATF-1 in the regulation of YWHAZ, silencing of ATF-1 resulted in a marked reduction in two of the five YWHAZ transcripts. These data suggest a novel mechanism for the transcriptional regulation of a major pro-survival gene, YWHAZ, by ATF-1.