Decreased expression of 14-3-3 σ, an early event of malignant transformation of respiratory epithelium, also facilitates progression of squamous cell lung cancer

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.

Novel biomarkers for the diagnosis and prognosis of gallbladder cancer

Gallbladder cancer (GBC) is the most common form of biliary tract malignancy with a dismal prognosis. A poor outcome in patients with GBC is related to the aggressive nature of the tumor, delayed diagnosis, and a lack of reliable biomarkers and effective treatment. Therefore, early diagnosis and accurate disease assessment are crucial to prolonging the patient survival. Identification of novel prognostic and diagnostic biomarkers may help improve the early diagnostic rate and develop specific targeted treatments for patients with GBC. We herein review the novel biomarkers that may be associated with the diagnosis and prognosis in GBC and their potential clinical significance in the management of GBC.

Overexpression of 14-3-3σ Modulates Cholangiocarcinoma Cell Survival by PI3K/Akt Signaling

The protein 14-3-3σ is involved in numerous cellular processes through its ability to bind phosphorylated serine/threonine residues. It is a key regulator of the cell cycle involving in G2 arrest by p53. Deregulation of 14-3-3σ expression has been associated with a large variety of human cancers. However, its physiological function and therapeutic significance have rarely been investigated in cholangiocarcinoma. Using immunohistochemistry (IHC), we evaluated 14-3-3σ expression in 65 human extrahepatic cholangiocarcinomas. As a result, we found that 14-3-3σ is expressed in the tissue of 56 patients (86.2%), and its expression is positively correlated with tumor size, lymph node metastasis, and tumor stage. We also explored the significance of 14-3-3σ and found that 14-3-3σ exerts cell type-dependent effects on cell proliferation through PI3K/Akt signaling in both in vitro and in vivo xenograft models. These results suggest that 14-3-3σ assumes a constitutive role in tumorigenesis rather than acting as a cell cycle regulator in cholangiocarcinoma, which makes 14-3-3σ a new potential target for therapeutic intervention.

Role of stratifin (14-3-3 sigma) in adenocarcinoma of gallbladder: A novel prognostic biomarker

BACKGROUND

Gallbladder cancer (GBC) is a rare and fatal biliary tract malignancy. Genetic derangements are one of many factors that determine the prognosis of GBC. In this study, the expression of the stratifin (SFN) gene encoding 14-3-3 sigma protein, which is reported to be associated with the metastatic property of cholangiocarcinoma cells, was investigated in GBC.

MATERIAL AND METHODS

Formalin-fixed paraffin-embedded cancer (n = 37) and non-cancer control tissues (n = 14) of gallbladders from patients who underwent surgical resection from January 2006 to May 2015 were retrieved. The expression of SFN normalized with that of ACTB was determined using RT-qPCR. Multivariate analysis of factors affecting disease-free survival (DFS) and overall survival (OS) including the type of SFN expression was performed.

RESULT

The average expression level of SFN in cancer was higher than that in control tissues (p = 0.002). The relative SFN expression in cancer tissue was classified as overexpression (n = 14) and control level expression (n = 23) according to the receiver operating characteristic (ROC) curves for discriminating early GBC recurrence or metastasis after surgery. The SFN overexpression group was associated with lower rates of distant metastasis and early tumor recurrence following resection. The univariate analysis demonstrated factors affecting DFS, including resection margin (p < 0.001), lymphovascular invasion (p = 0.040), perineural invasion (p = 0.046), and SFN expression (p < 0.001). The multivariate analysis revealed that the resection margin (p = 0.019) and SFN expression (P = 0.040) were independent prognostic factors of DFS.

CONCLUSION

To achieve the longest survival, margin-free resection is recommended. The overexpression of SFN in GBC is associated with better prognosis, lower rates of early cancer recurrence, and distant metastasis following resection. SFN expression might be a novel prognostic biomarker in GBC treatment. Further studies to elucidate the role of SFN might unveil its clinical benefit in cancer treatment regimens.

Intrinsic disorder associated with 14-3-3 proteins and their partners

Protein-protein interactions (PPIs) mediate a variety of cellular processes and form complex networks, where connectivity is achieved owing to the "hub" proteins whose interaction with multiple protein partners is facilitated by the intrinsically disordered protein regions (IDPRs) and posttranslational modifications (PTMs). Universal regulatory proteins of the eukaryotic 14-3-3 family nicely exemplify these concepts and are the focus of this chapter. The extremely wide interactome of 14-3-3 proteins is characterized by high levels of intrinsic disorder (ID) enabling protein phosphorylation and consequent specific binding to the well-structured 14-3-3 dimers, one of the first phosphoserine/phosphothreonine binding modules discovered. However, high ID enrichment also challenges structural studies, thereby limiting the progress in the development of small molecule modulators of the key 14-3-3 PPIs of increased medical importance. Besides the well-known structural flexibility of their variable C-terminal tails, recent studies revealed the strong and conserved ID propensity hidden in the N-terminal segment of 14-3-3 proteins (~40 residues), normally forming the α-helical dimerization region, that may have a potential role for the dimer/monomer dynamics and recently reported moonlighting chaperone-like activity of these proteins. We review the role of ID in the 14-3-3 structure, their interactome, and also in selected 14-3-3 complexes. In addition, we discuss approaches that, in the future, may help minimize the disproportion between the large amount of known 14-3-3 partners and the small number of 14-3-3 complexes characterized with atomic precision, to unleash the whole potential of 14-3-3 PPIs as drug targets.

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.

Downregulation of 14-3-3β inhibits proliferation and migration in osteosarcoma cells

The 14-3-3 protein isoform β (14‑3‑3β), which is an intracellular adaptor protein that exists in all eukaryotic organisms, is highly expressed in many cancer tissues, including glioma, lung carcinoma and breast cancer. However, 14‑3‑3β expression and function in osteosarcoma progression remain unknown. In the present study, the endogenous expression of 14‑3‑3β was assessed in osteosarcoma samples and the effect of 14‑3‑3β knockdown was examined in human osteosarcoma MG63 cells using small interfering RNA (siRNA). mRNA and protein expression levels for 14‑3‑3β were detected by reverse transcription‑quantitative polymerase reaction and western blotting, respectively. The results demonstrated that endogenous 14‑3‑3β mRNA and protein were highly expressed in human osteosarcoma tissues and osteosarcoma cell lines (U2OS, MG63 and SaOs‑2), but not in normal bone tissues or normal osteoblast hFOB1.19 cells. These data suggested that increased expression of 14‑3‑3β may be significantly associated with the development and progression of osteosarcoma. Therefore, the effect of 14‑3‑3β knockdown in MG63 cells was further examined in vitro. Knockdown of 14‑3‑3β by siRNA significantly decreased cell viability, and inhibited cell proliferation and invasion. In addition, 14‑3‑3β knockdown significantly decreased the protein expression levels of β‑catenin, cyclin D1, v‑myc avian myelocytomatosis viral oncogene homolog and matrix metallopeptidase 9 in osteosarcoma MG63 cells. These results suggested that the anticancer effects of 14‑3‑3β knockdown in MG63 cells might be mediated by the inhibition of the Wnt/β‑catenin signaling pathway. In summary, 14‑3‑3β knockdown decreased proliferation and invasion in MG63 cells, which suggests a potential therapeutic application for 14‑3‑3β as a novel target for the treatment of osteosarcoma patients.

Identification of microRNA differentially expressed in three subtypes of non-small cell lung cancer and in silico functional analysis

Emerging studies demonstrated that miRNAs played fundamental roles in lung cancer. In this study, we attempted to explore the clinical significance of the miRNA signature in different histological subtypes of non-small cell lung cancer (NSCLC). Three miRNome profiling datasets (GSE19945, GSE25508 and GSE51853) containing lung squamous cell carcinoma (SCC), lung adenocarcinoma (ADC) and large cell lung cancer (LCLC) samples were obtained for bioinformatics and survival analysis. Moreover, pathway enrichment and coexpression network were performed to explore underlying molecular mechanism. MicroRNA-375 (miR-375), miR-203 and miR-205 were identified as differentially expressed miRNAs (DEmiRNAs) which distinguished SCC from other NSCLC subtypes. Pathway enrichment analysis suggested that Hippo signaling pathway was combinatorically affected by above mentioned three miRNAs. Coexpression analysis of three miRNAs and the Hippo signaling pathway related genes were conducted based on another dataset, GSE51852. Four hub genes (TP63, RERE, TJP1 and YWHAE) were identified as the candidate targets of three miRNAs, and three of them (TP63, TJP1 and YWHAE) were validated to be downregulated by miR-203 and miR-375, respectively. Finally, survival analysis further suggested the prognostic value of three-miRNA signature in SCC patients. Taken together, our study compared the miRNA profiles among three histological subtypes of NSCLC, and suggested that a three-miRNA signature might be potential diagnostic and prognostic biomarkers for SCC patients.

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.