CPEB1 promotes differentiation and suppresses EMT in mammary epithelial cells

Long-term severe hypoxia adaptation induces non-canonical EMT and a novel Wilms Tumor 1 (WT1) isoform

The majority of cancer deaths are caused by solid tumors, where the four most prevalent cancers (breast, lung, colorectal and prostate) account for more than 60% of all cases (1). Tumor cell heterogeneity driven by variable cancer microenvironments, such as hypoxia, is a key determinant of therapeutic outcome. We developed a novel culture protocol, termed the Long-Term Hypoxia (LTHY) time course, to recapitulate the gradual development of severe hypoxia seen in vivo to mimic conditions observed in primary tumors. Cells subjected to LTHY underwent a non-canonical epithelial to mesenchymal transition (EMT) based on miRNA and mRNA signatures as well as displayed EMT-like morphological changes. Concomitant to this, we report production of a novel truncated isoform of WT1 transcription factor (tWt1), a non-canonical EMT driver, with expression driven by a yet undescribed intronic promoter through hypoxia-responsive elements (HREs). We further demonstrated that tWt1 initiates translation from an intron-derived start codon, retains proper subcellular localization and DNA binding. A similar tWt1 is also expressed in LTHY-cultured human cancer cell lines as well as primary cancers and predicts long-term patient survival. Our study not only demonstrates the importance of culture conditions that better mimic those observed in primary cancers, especially with regards to hypoxia, but also identifies a novel isoform of WT1 which correlates with poor long-term survival in ovarian cancer.

Cytoplasmic Polyadenylation Element Binding Protein 1 and Atherosclerosis: Prospective Target and New Insights

The ribonucleic acid (RNA)-binding protein Cytoplasmic Polyadenylation Element Binding Protein 1 (CPEB1), a key member of the CPEB family, is essential in controlling gene expression involved in both healthy physiological and pathological processes. CPEB1 can bind to the 3'- untranslated regions (UTR) of substrate messenger ribonucleic acid (mRNA) and regulate its translation. There is increasing evidence that CPEB1 is closely related to the pathological basis of atherosclerosis. According to recent investigations, many pathological processes, including inflammation, lipid metabolism, endothelial dysfunction, angiogenesis, oxidative stress, cellular senescence, apoptosis, and insulin resistance, are regulated by CPEB1. This review considers the prevention and treatment of atherosclerotic heart disease in relation to the evolution of the physiological function of CPEB1, recent research breakthroughs, and the potential participation of CPEB1 in atherosclerosis.

Re-evaluation of the myoepithelial cells roles in the breast cancer progression

Over the past decades, luminal epithelial cell lineage has gained considerable attraction as the functionally milk-secreting units and as the most fruitful acreage for breast cancer launching. Recognition of the effective involvement of the myoepithelial cells in mammary gland development and in hampering tumorigenesis has renewed the interest in investigating the biological roles of this second main mammary lineage. The human breast is made up of an extensively branching ductal system intervening by copious lobular units. The ductal system is coated by a chain of luminal epithelial cells (LECs) situated on a layer of myoepithelial cells (MECs) and encompassed by a distinguished basement membrane. Ductal contractility during lactation is a well-known function delivered by the MECs however this is not the only assignment mediated by these cellular populations. It has been well appreciated that the MECs exhibit a natural paracrine power in defeating cancer development and advancement. MECs were found to express numerous proteinase inhibitors, anti-angiogenic factors, and tumour suppressors proteins. Additionally, MECs contributed effectively to maintaining the right luminal cells' polarization and further separating them from the adjacent stroma by making an integrated fence. Indeed, disruption of the MECs layer was reported to facilitate the invasion of the cancer cells to the surrounding stroma. Nonetheless, MECs were also found to exhibit cancer-promoting effects and provoke tumour invasion and dissemination by displaying distinct cancer chemokines. Herein in this review, we aimed to address the roles delivered by MECs in breast cancer progression and decipher the molecular mechanisms regulating proper MECs' physiology, integrity, and terminal differentiation.

Identification of the Key Genes Associated with the Yak Hair Follicle Cycle

The development of hair follicles in yak shows significant seasonal cycles. In our previous research, transcriptome data including mRNAs and lncRNAs in five stages during the yak hair follicles (HFs) cycle were detected, but their regulation network and the hub genes in different periods are yet to be explored. This study aimed to screen and identify the hub genes during yak HFs cycle by constructing a mRNA-lncRNA co-expression network. A total of 5000 differently expressed mRNA (DEMs) and 729 differently expressed long noncoding RNA (DELs) were used to construct the co-expression network, based on weighted genes co-expression network analysis (WGCNA). Four temporally specific modules were considered to be significantly associated with the HFs cycle of yak. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis revealed that the modules are enriched into Wnt, EMC-receptor interaction, PI3K-Akt, focal adhesion pathways, and so on. The hub genes, such as FER, ELMO1, PCOLCE, and HOXC13, were screened in different modules. Five hub genes (WNT5A, HOXC13, DLX3, FOXN1, and OVOL1) and part of key lncRNAs were identified for specific expression in skin tissue. Furthermore, immunofluorescence staining and Western blotting results showed that the expression location and abundance of DLX3 and OVOL1 are changed following the process of the HFs cycle, which further demonstrated that these two hub genes may play important roles in HFs development.

Novel lncRNAs Co-Expression Networks Identifies LINC00504 with Oncogenic Role in Luminal A Breast Cancer Cells

Long non-coding RNAs (lncRNAs) are functional transcripts with more than 200 nucleotides. These molecules exhibit great regulatory capacity and may act at different levels of gene expression regulation. Despite this regulatory versatility, the biology of these molecules is still poorly understood. Computational approaches are being increasingly used to elucidate biological mechanisms in which these lncRNAs may be involved. Co-expression networks can serve as great allies in elucidating the possible regulatory contexts in which these molecules are involved. Herein, we propose the use of the pipeline deposited in the RTN package to build lncRNAs co-expression networks using TCGA breast cancer (BC) cohort data. Worldwide, BC is the most common cancer in women and has great molecular heterogeneity. We identified an enriched co-expression network for the validation of relevant cell processes in the context of BC, including LINC00504. This lncRNA has increased expression in luminal subtype A samples, and is associated with prognosis in basal-like subtype. Silencing this lncRNA in luminal A cell lines resulted in decreased cell viability and colony formation. These results highlight the relevance of the proposed method for the identification of lncRNAs in specific biological contexts.

CPEB1 orchestrates a fine-tuning of miR-145-5p tumor-suppressive activity on TWIST1 translation in prostate cancer cells

TWIST1 is a basic helix-loop-helix transcription factor, and one of the master Epithelial-to-Mesenchymal Transition (EMT) regulators. We show that tumor suppressor miR-145-5p controls TWIST1 expression in an immortalized prostate epithelial cell line and in a tumorigenic prostate cancer-derived cell line. Indeed, shRNA-mediated miR-145-5p silencing enhanced TWIST1 expression and induced EMT-associated malignant properties in these cells. However, we discovered that the translational inhibitory effect of miR-145-5p on TWIST1 is lost in 22Rv1, another prostate cancer cell line that intrinsically expresses high levels of the CPEB1 cytoplasmic polyadenylation element binding protein. This translational regulator typically reduces TWIST1 translation efficiency by shortening the TWIST1 mRNA polyA tail. However, our results indicate that the presence of CPEB1 also interferes with the binding of miR-145-5p to the TWIST1 mRNA 3′UTR. Mechanistically, CPEB1 binding to its first cognate site either directly hampers the access to the miR-145-5p response element or redirects the cleavage/polyadenylation machinery to an intermediate polyadenylation site, resulting in the elimination of the miR-145-5p binding site. Taken together, our data support the notion that the tumor suppressive activity of miR-145-5p on TWIST1 translation, consequently on EMT, self-renewal, and migration, depends on the CPEB1 expression status of the cancer cell. A preliminary prospective study using clinical samples suggests that reconsidering the relative status of miR-145-5p/TWIST1 and CPEB1 in the tumors of prostate cancer patients may bear prognostic value.

ASR488, a novel small molecule, activates an mRNA binding protein, CPEB1, and inhibits the growth of bladder cancer

Due to a lack of mechanistic insights, muscle-invasive bladder cancer (MIBC) remains incurable and is one of the most lethal types of cancer in the United States. The present study investigated changes in the molecular signatures of MIBC cells (TCCSUP and HT1376) after treatment with a novel small molecule, ASR488, to gain knowledge of the mechanisms that inhibited MIBC cell growth. ASR488 treatment initiated apoptotic signaling in MIBC cells. Pathway enrichment analysis was used to analyze the changes in function of differentially expressed genes. Gene Ontology analysis, as well as Kyoto Encyclopedia of Genes and Genomes analysis, was also performed. These analyses along with reactome pathway enrichment analyses indicated that the genes upregulated in the ASR488-treated cells are involved in focal adhesion, neurotrophin signaling, p53 signaling, endoplasmic reticulum functioning in terms of protein processing, and pathways related to bladder cancer. The genes downregulated in ASR488-treated MIBC cells were mainly involved in DNA replication, mismatch repair, RNA degradation, nucleotide excision repair and TGFβ signaling (P<0.05). Furthermore, reverse transcription-quantitative PCR analysis revealed an increase in transcripts of the most upregulated genes in ASR 488-treated MIBC cells: CPEB1 (36-fold), IL11 (30-fold), SFN (20.12-fold) and CYP4F11 (15.8-fold). In conclusion, the analysis of biological functions of the most differentially expressed genes revealed possible mechanisms that may be associated with the aggressiveness of MIBC.

Identification of key genes relevant to the prognosis of ER-positive and ER-negative breast cancer based on a prognostic prediction system

Few prognostic indicators with differential expression have been reported among the differing ER statuses. We aimed to screen important breast cancer prognostic genes related to ER status and to construct an efficient prognostic prediction system. mRNA expression profiles were downloaded from TCGA and GSE70947 dataset. Two hundred seventy-one overlapping differentially expressed genes (DEGs) between the ER- and ER+ breast cancer samples were identified. Among the 271 DEGs, 109 prognostically relevant mRNAs were screened. mRNAs such as RASEF, ITM2C, CPEB2, ESR1, ANXA9, and VASN correlated strongly with breast cancer prognosis. Three modules, which contained 28, 9 and 8 enriched DEGs, were obtained from the network, and the DEGs in these modules were enriched in response to hormone stimulus, epithelial cell development, and host cell entry. Using bayes discriminant analysis, 48 signature genes were screened. We constructed a prognostic prediction system using the 48 signature genes and validated this system as relatively accurate and reliable. The DEGs might be closely associated with the prognosis in patients with breast cancer. We validated the effectiveness of our prognostic prediction system by GEO database. Therefore, this system might be a useful tool for preliminary screening and validation of potential prognosis indicators for ER+ breast cancer derived from mechanistic research.

Luminal STAT5 mediates H2AX promoter activity in distinct population of basal mammary epithelial cells

Deregulated STAT5 activity in the mammary gland causes parity-dependent tumorigenesis. Epithelial cell cultures transfected with constitutively active STAT5 express higher levels of the histone H2AX than their non-transfected counterparts. Higher H2AX expression may be involved in tumorigenesis. Here, we aimed to link high STAT5 activity to H2AX–GFP expression by looking for distinct types of mammary cells that express these proteins. In vitro and in transgenic mice, only 0.2 and 0.02%, respectively, of the cells expressed the H2AX–GFP hybrid gene. Its expression correlated with that of the endogenous H2AX gene, suggesting that detectable H2AX–GFP expression marks high levels of H2AX transcript. Methylation of the H2AX promoter characterized non-GFP-expressing H2AX–GFP cells and was inversely correlated with promoter activity. Administration of 5-azacytidine increased H2AX promoter activity in an activated STAT5-dependent manner. In transgenic mice, H2AX–GFP expression peaked at pregnancy. The number of H2AX–GFP-expressing cells and GFP expression decreased in a Stat5a-null background and increased in mice expressing the hyperactivated STAT5. Importantly, H2AX–GFP activity was allocated to basal mammary cells lacking stem-cell properties, whereas STAT5 hyperactivity was detected in the adjacent luminal cells. Knockdown of RANKL by siRNA suggested its involvement in signaling between the two layers. These results suggest paracrine activation of H2AX via promoter demethylation in specific populations of basal mammary cells that is induced by a signal from neighboring luminal cells with hyper STAT5 activity. This pathway provides an alternative route for the luminally confined STAT5 to affect basal mammary cell activity.

Translational Dysregulation in Cancer: Molecular Insights and Potential Clinical Applications in Biomarker Development

Although transcript levels have been traditionally used as a surrogate measure of gene expression, it is increasingly recognized that the latter is extensively and dynamically modulated at the level of translation (messenger RNA to protein). Over the recent years, significant progress has been made in dissecting the complex posttranscriptional mechanisms that regulate gene expression. This advancement in knowledge came hand in hand with the progress made in the methodologies to study translation both at gene-specific as well as global genomic level. The majority of translational control is exerted at the level of initiation; nonetheless, protein synthesis can be modulated at the level of translation elongation, termination, and recycling. Sequence and structural elements and epitranscriptomic modifications of individual transcripts allow for dynamic gene-specific modulation of translation. Cancer cells usurp the regulatory mechanisms that govern translation to carry out translational programs that lead to the phenotypic hallmarks of cancer. Translation is a critical nexus in neoplastic transformation. Multiple oncogenes and signaling pathways that are activated, upregulated, or mutated in cancer converge on translation and their transformative impact "bottlenecks" at the level of translation. Moreover, this translational dysregulation allows cancer cells to adapt to a diverse array of stresses associated with a hostile microenviroment and antitumor therapies. All elements involved in the process of translation, from the transcriptional template, the components of the translational machinery, to the proteins that interact with the transcriptome, have been found to be qualitatively and/or quantitatively perturbed in cancer. This review discusses the regulatory mechanisms that govern translation in normal cells and how translation becomes dysregulated in cancer leading to the phenotypic hallmarks of malignancy. We also discuss how dysregulated mediators or components of translation can be utilized as biomarkers with potential diagnostic, prognostic, or predictive significance. Such biomarkers have the potential advantage of uniform applicability in the face of inherent tumor heterogeneity and deoxyribonucleic acid instability. As translation becomes increasingly recognized as a process gone awry in cancer and agents are developed to target it, the utility and significance of these potential biomarkers is expected to increase.

Role and therapeutic potential of vascular stem/progenitor cells in pathological neovascularisation during chronic portal hypertension

OBJECTIVE

Pathological neovascularisation is intimately involved in portal hypertension (PH). Here, we determined the contribution of vascular stem/progenitor cells (VSPCs) to neovessel growth in PH and whether the RNA-binding protein cytoplasmic polyadenylation element binding protein-4 (CPEB4) was behind the mechanism controlling VSPC function.

DESIGN

To identify and monitor VSPCs in PH rats (portal vein-ligated), we used a combinatorial approach, including sphere-forming assay, assessment of self-renewal, 5-bromo-2'-desoxyuridine label retention technique, in vitro and in vivo stem/progenitor cell (SPC) differentiation and vasculogenic capability, cell sorting, as well as immunohistochemistry, immunofluorescence and confocal microscopy expression analysis. We also determined the role of CPEB4 on VSPC proliferation using genetically engineered mouse models.

RESULTS

We demonstrated the existence in the mesenteric vascular bed of VSPCs displaying capability to form cellular spheres in suspension culture, self-renewal ability, expression of molecules commonly found in SPCs, slow-cycling features, in addition to other cardinal properties exhibited by SPCs, like capacity to differentiate into endothelial cells and pericytes with remarkable vasculogenic activity. Such VSPCs showed, after PH induction, an early switch in proliferation, and differentiated in vivo into endothelial cells and pericytes, contributing, structurally and functionally, to abnormal neovessel formation. Quantification of VSPC-dependent neovessel formation in PH further illustrated the key role played by VSPCs. We also demonstrated that CPEB4 regulates the proliferation of the activated VSPC progeny upon PH induction.

CONCLUSIONS

These findings demonstrate that VSPC-derived neovessel growth (ie, vasculogenesis) and angiogenesis cooperatively stimulate mesenteric neovascularisation in PH and identify VSPC and CPEB4 as potential therapeutic targets.

A Multi-Step miRNA-mRNA Regulatory Network Construction Approach Identifies Gene Signatures Associated with Endometrioid Endometrial Carcinoma

We aimed to identify endometrioid endometrial carcinoma (EEC)-related gene signatures using a multi-step miRNA-mRNA regulatory network construction approach. Pathway analysis showed that 61 genes were enriched on many carcinoma-related pathways. Among the 14 highest scoring gene signatures, six genes had been previously shown to be endometrial carcinoma. By qRT-PCR and next generation sequencing, we found that a gene signature (CPEB1) was significantly down-regulated in EEC tissues, which may be caused by hsa-miR-183-5p up-regulation. In addition, our literature surveys suggested that CPEB1 may play an important role in EEC pathogenesis by regulating the EMT/p53 pathway. The miRNA-mRNA network is worthy of further investigation with respect to the regulatory mechanisms of miRNAs in EEC. CPEB1 appeared to be a tumor suppressor in EEC. Our results provided valuable guidance for the functional study at the cellular level, as well as the EEC mouse models.

CPEB1 restrains proliferation of Glioblastoma cells through the regulation of p27(Kip1) mRNA translation

The cytoplasmic element binding protein 1 (CPEB1) regulates many important biological processes ranging from cell cycle control to learning and memory formation, by controlling mRNA translation efficiency via 3' untranslated regions (3'UTR). In the present study, we show that CPEB1 is significantly downregulated in human Glioblastoma Multiforme (GBM) tissues and that the restoration of its expression impairs glioma cell lines growth. We demonstrate that CPEB1 promotes the expression of the cell cycle inhibitor p27(Kip1) by specifically targeting its 3'UTR, and competes with miR-221/222 binding at an overlapping site in the 3'UTR, thus impairing miR-221/222 inhibitory activity. Upon binding to p27(Kip1) 3'UTR, CPEB1 promotes elongation of poly-A tail and the subsequent translation of p27(Kip1) mRNA. This leads to higher levels of p27(Kip1) in the cell, in turn significantly inhibiting cell proliferation, and confers to CPEB1 a potential value as a tumor suppressor in Glioblastoma.

CPEB1 mediates epithelial-to-mesenchyme transition and breast cancer metastasis

In mouse mammary epithelial cells, CPEB1 mediates the apical localization of ZO-1 mRNA, which encodes a critical tight junction component. In mice lacking CPEB1 and in cultured cells from which CPEB has been depleted, randomly distributed ZO-1 mRNA leads to the loss of cell polarity. We have investigated whether this diminution of polarity results in an epithelial-to-mesenchyme (EMT) transition and possible increased metastatic potential. Here, we show that CPEB1-depleted mammary epithelial cells alter their gene expression profile in a manner consistent with an EMT and also become motile, which are made particularly robust when cells are treated with TGF-β, an enhancer of EMT. CPEB1-depleted mammary cells become metastatic to the lung following injection into mouse fat pads while ectopically-expressed CPEB1 prevents metastasis. Surprisingly, CPEB1 depletion causes some EMT/metastasis-related mRNAs to have shorter poly(A) tails while other mRNAs to have longer poly(A) tails. Matrix metalloproteinase 9 (MMP9) mRNA, which encodes a metastasis-promoting factor, undergoes poly(A) lengthening and enhanced translation upon CPEB reduction. Moreover, in human breast cancer cells that become progressively more metastatic, CPEB1 is reduced while MMP9 becomes more abundant. These data suggest that at least in part, CPEB1 regulation of MMP9 mRNA expression mediates metastasis of breast cancer cells.

CPEB1 modulates differentiation of glioma stem cells via downregulation of HES1 and SIRT1 expression

Glioma stemness has been recognized as the most important reason for glioma relapse and drug resistance. Differentiation of glioma stem cells (GSCs) has been implicated as a novel approach to target recurrent glioma. However, the detailed molecular mechanism involved in the differentiation of GSCs has not yet been elucidated. This study identified CPEB1 as the key modulator that induces the differentiation of GSCs at the post-transcriptional level. Gain and loss of function experiments showed that CPEB1 expression reduced sphere formation ability and the expression of stemness markers such as Nestin and Notch. To elucidate the detailed molecular mechanism underlying the action of CPEB1, we investigated the interacting ribonome of the CPEB1 complex using a Ribonomics approach. CPEB1 specifically suppressed the translation of HES1 and SIRT1 by interacting with a cytoplasmic polyadenylation element. The expression profile of CPEB1 negatively correlated with overall survival in glioma patients. Overexpression of CPEB1 decreased the number of GSCs in an orthotopically implanted glioma animal model. These results suggest that CPEB1-mediated translational control is essential for the differentiation of GSCs and provides novel therapeutic concepts for differentiation therapy.