YB-1 interplays with ERα to regulate the stemness and differentiation of ER-positive breast cancer stem cells.

Background: Some stemness-associated transcription factors consistently play essential roles in the maintenance of pluripotency or induce the differentiation of cancer stem cells (CSCs). However, the regulatory mechanism of CSC stemness mediated by transcription factors has not been extensively explored. Here, we show that two transcription factors (YB-1 and ERα), which are simultaneously highly expressed in estrogen receptor (ER)-positive CSCs, interact with each other to regulate the stemness and differentiation of ER-positive CSCs. Methods: The expression of YB-1 was examined in ER-positive CSCs and patient specimens. Western blot, real-time PCR, cell viability analysis, tumorsphere formation assay and subcutaneous tumorigenesis assays were used to study the stemness functions of YB-1 and ERα in CSCs. The relationship between YB-1 and ERα in cells was studied by promoter activity analysis, the electrophoretic mobility shift assay (EMSA) and the Co-IP assay. The mechanisms and functional significance of YB-1 in the sensitivity of CSCs to tamoxifen were further investigated with both in vitro and in vivo models. Results: YB-1 was aberrantly upregulated in the cancerous tissue of ER-positive breast cancer patients and in CSCs. Knockdown of YB-1 in ER-positive CSCs significantly inhibited cell stemness and induced differentiation, and the expression of YB-1 could be regulated by estrogen signaling and ERα in ER-positive breast CSCs. The Co-IP results showed that YB-1 interacted directly with ERα specifically in ER-positive non-CSCs and that YB-1 induced ERα degradation by ubiquitination via direct interaction in differentiated cells. Cell differentiation induced by FBS could inhibit YB-1 phosphorylation and promote YB-1 protein transfer from the nucleus to the cytoplasm. Moreover, cell differentiation induced by targeting inhibited the expression of YB-1 in ER-positive CSCs, which increased the sensitivity of cells to tamoxifen in vitro and in vivo. Conclusion: The ERα/YB-1 axis has an important role in the regulation of ER-positive breast cancer stemness. The dephosphorylation of YB-1 and the interaction between YB-1 and ERα may be the switch that initiates the differentiation of ER-positive CSCs. Targeting YB-1 to sensitize ER-positive CSCs to antiestrogen therapy might represent a new therapeutic strategy that warrants further exploration.

The Role of YB1 in Renal Cell Carcinoma Cell Adhesion.

Background: Y-box binding protein 1 (YB1) is a multifunctional protein involved in many processes related to cancer progression and metastasis. Methods: In this study, we constructed YB1 knockdown stable renal cell carcinoma (RCC) cell line 786-0. The gene expression profile of 786-0 was performed by DNA microarray analysis to identify genes that were regulated by YB1. Real-time PCR and western blotting were used to test the genes and proteins expression. Transforming growth factor-ß (TGF-ß) activity was detected by dual-luciferase reporter assay. Cell adhesion assay was used to determine RCC cell adhesion ability. Results: Pathway analysis revealed that YB1 knockdown influenced cell adhesion molecules (CAMs). We further verified four genes (CLDN4, NRXN3, ITGB8, and VCAN) related to CAMs by real-time PCR, and confirmed that YB1 regulated the expression of ITGB8 in RCC. Functional assays demonstrated that knockdown of YB1 significantly inhibited the cell adhesion of 786-0 cells in vitro. In addition, YB1 affected TGF-ß activation. Conclusion: Our study demonstrated that YB1 modulated the adhesion ability of renal cell carcinoma cells by regulating ITGB8 and TGF-ß.

Developmental characterization and environmental stress responses of Y-box binding protein 1 gene (AccYB-1) from Apis cerana cerana.

Y-box binding protein 1 (YB-1) is a member of the cold shock domain protein superfamily and is involved in development, environmental stresses and DNA oxidative damage in many organisms. However, the precise functions of YB-1 are still not well understood in various insects, including bees. In the current study, we identified a YB-1 gene in Apis cerana cerana (AccYB-1). The predicted cis-acting elements in the promoter sequence of AccYB-1 indicated its possible roles in development and stress responses. AccYB-1 expression was higher in one-day-old larvae and dark-eyed pupae than in other development stages. Tissue-specific expression analysis showed that the mRNA level of AccYB-1 was higher in the thorax and midgut than in other tissues. The results from real-time PCR showed that AccYB-1 was induced by many environmental stresses. Silencing AccYB-1 downregulated the transcriptional level of some growth- and development-related genes and antioxidant genes and decreased the enzyme activities of several antioxidant-related enzymes, further indicating a possible function of AccYB-1 in growth, development and stress responses. Taken together, our findings suggest that AccYB-1 may play an indispensable role in growth and development and environmental stress responses in Apis cerana cerana. To our knowledge, this is the first paper to explore the role of YB-1 in bees.

Investigation of function and regulation of the YB-1 cellular factor in HIV replication.

Y-box binding protein 1 (YB-1) is a member of the cold-shock domain (CSD) protein superfamily. It participates in a wide variety of cellular events, including transcription, RNA splicing, translation, DNA repair, drug resistance, and stress responses. We investigated putative functions of YB-1 in HIV-1 replication. Functional studies using overexpression or knockdown of YB-1 in conjunction with transfection of proviral DNA showed that YB-1 enhances virus production. We found YB-1 regulates HIV-1 production by stimulating viral transcription using HIV-1 LTR sequence U3RU5 with Luciferase assay. We also identified a specific region from amino acids 1 to 324 of YB-1 as necessary for the participation of the protein in the production of virions. [BMB Reports 2018; 51(6): 290-295].

The Role of the Y Box Binding Protein 1 C-Terminal Domain in Vascular Endothelial Cell Proliferation, Apoptosis, and Angiogenesis.

Different domains of the multifunctional transcription factor Y-box binding protein 1 (YB1) regulate proliferation, differentiation, and apoptosis by transactivating or repressing the promoters of various genes. Here we report that the C-terminal domain of YB1 (YB1 CTD) is involved in endothelial cell proliferation, apoptosis, and tube formation. The oligo pull-down assays demonstrated that YB1 directly binds double-stranded GC box sequences in endothelial cells through the 125-220 amino acids. Adenovirus expression vectors harboring green fluorescent protein (GFP) or GFP-tagged YB1 CTD were constructed and used to infect EA.hy926 endothelial cells. Overexpression of the YB1 CTD significantly increased p21 expression, decreased cyclin B1 expression, and inhibited the proliferation of EA.hy926 cells. YB1 CTD overexpression also increased Bax and active caspase 3 expression, decreased Bcl-2 expression, and induced apoptosis in EA.hy926 cells. Furthermore, overexpression of the YB1 CTD significantly suppressed migration and tube formation in EA.hy926 cells. Finally, YB1 CTD decreased ERK1/2 phosphorylation in EA.hy926 cells. These findings demonstrated vital roles for YB1 in endothelial cell proliferation, apoptosis, and tube formation through transcriptional regulation of GC box-related genes.

THE INFLUENCE AND REGULATORY MECHANISM OF Y-BOX BINDING PROTEIN 1 IN OSTEOSARCOMA AND ITS SIGNIFICANCE.

This study quantified the expression of Y-box binding protein 1 (YB-1) by the immunohistochemical method based on pathological paraffin block specimens of aspiration biopsy from patients with osteosarcoma to explore the influence and regulatory mechanism of YB-1 in osteosarcoma and its significance. Patients were divided into two groups with high and low expressed YB-1, and results showed that 7 cases (13.7%) and 18 cases (26.1%) were in level III, and 44 cases (86.3%) and 51 cases (76.9%) were in level IV respectively, and patients with high YB-1 expression quantity had higher malignant tumor degree (p=0.03). Moreover, the tumor necrosis rate induced by chemotherapy in the two groups were 21 cases (41.2%) and 38 cases (51.8%), respectively. By survival analysis, it was found that a 5-year overall survival rate of patients with high YB-1 expression and low YB-1 expression were 61.2% and 76.6%, respectively (p = 0.054), and 5-year event free survival rates were 52.5% and 72.4%, respectively (p = 0.033). Furthermore, metastasis rate of high YB-1 expression and low YB-1 expression were 41.8% and 22.7%, respectively (p = 0.036), indicating that patients with high YB-1 expression had higher pulmonary metastasis rate. Through further study, we discovered that possibly miR-382 plays a regulatory role in YB-1 gene in osteosarcoma.

Translational Activation of HIF1α by YB-1 Promotes Sarcoma Metastasis.

Metastatic dissemination is the leading cause of death in cancer patients, which is particularly evident for high-risk sarcomas such as Ewing sarcoma, osteosarcoma, and rhabdomyosarcoma. Previous research identified a crucial role for YB-1 in the epithelial-to-mesenchymal transition (EMT) and metastasis of epithelial malignancies. Based on clinical data and two distinct animal models, we now report that YB-1 is also a major metastatic driver in high-risk sarcomas. Our data establish YB-1 as a critical regulator of hypoxia-inducible factor 1α (HIF1α) expression in sarcoma cells. YB-1 enhances HIF1α protein expression by directly binding to and activating translation of HIF1A messages. This leads to HIF1α-mediated sarcoma cell invasion and enhanced metastatic capacity in vivo, highlighting a translationally regulated YB-1-HIF1α axis in sarcoma metastasis.

HuR and other turnover- and translation-regulatory RNA-binding proteins: implications for the kidney.

The posttranscriptional regulation of gene expression occurs through cis RNA regulatory elements by the action of trans factors, which are represented by noncoding RNAs (especially microRNAs) and turnover- and translation-regulatory (TTR) RNA-binding proteins (RBPs). These multifactorial proteins are a group of heterogeneous RBPs primarily implicated in controlling the decay and translation rates of target mRNAs. TTR-RBPs usually shuttle between cellular compartments (the nucleus and cytoplasm) in response to various stimuli and undergo posttranslational modifications such as phosphorylation or methylation to ensure their proper subcellular localization and function. TTR-RBPs are emerging as key regulators of a wide variety of genes influencing kidney physiology and pathology. This review summarizes the current knowledge of TTR-RBPs that influence renal metabolism. We will discuss the role of TTR-RBPs as regulators of kidney ischemia, fibrosis and matrix remodeling, angiogenesis, membrane transport, immunity, vascular tone, hypertension, and acid-base balance as well as anemia, bone mineral disease, and vascular calcification.

YB-1: oncoprotein, prognostic marker and therapeutic target?

Hanahan and Weinberg have proposed the 'hallmarks of cancer' to cover the biological changes required for the development and persistence of tumours [Hanahan and Weinberg (2011) Cell 144, 646-674]. We have noted that many of these cancer hallmarks are facilitated by the multifunctional protein YB-1 (Y-box-binding protein 1). In the present review we evaluate the literature and show how YB-1 modulates/regulates cellular signalling pathways within each of these hallmarks. For example, we describe how YB-1 regulates multiple proliferation pathways, overrides cell-cycle check points, promotes replicative immortality and genomic instability, may regulate angiogenesis, has a role in invasion and metastasis, and promotes inflammation. We also argue that there is strong and sufficient evidence to suggest that YB-1 is an excellent molecular marker of cancer progression that could be used in the clinic, and that YB-1 could be a useful target for cancer therapy.

Strong YB-1 expression is associated with liver metastasis progression and predicts shorter disease-free survival in advanced gastric cancer.

BACKGROUND: The most significant cause of gastric cancer (GC) death is metastasis, although the underlying mechanisms remain obscure. Y-box binding protein-1 (YB-1) is associated with tumor aggressiveness and poor prognosis in various cancers. In this study we investigated the relationship between YB-1 expression and the clinicopathologic features and metastasis-associated epithelial-mesenchymal transition (EMT) phenotype in advanced GC patients. PATIENTS AND METHODS: Immunohistochemistry (IHC) was used to analyze YB-1, E-cadherin, and vimentin expression in 98 advanced GC cases. RESULTS: Twenty-nine (29.6%) cases of GC exhibited strong YB-1 immunoreactivity. Strong YB-1 staining occurred more often in patients with intestinal or non-scirrhous cancer, and demonstrated a significant correlation with vascular invasion (VI), liver metastasis, and shorter disease-free survival (DFS). However, we observed no relationship between YB-1 expression and EMT phenotype or overall survival. Logistic regression analysis revealed that strong staining for YB-1 was the only predictive factor for liver metastasis. CONCLUSIONS: Our results indicate that YB-1 plays a role in the process of GC metastasis, and that the immunohistochemical detection of this protein potentially delivers valuable insight regarding the prediction of liver metastasis and shorter DFS in patients undergoing curative resection for advanced GC.

Angiogenin-induced tRNA fragments inhibit translation initiation.

Angiogenin is a stress-activated ribonuclease that cleaves tRNA within anticodon loops to produce tRNA-derived stress-induced fragments (tiRNAs). Transfection of natural or synthetic tiRNAs inhibits protein synthesis and triggers the phospho-eIF2α-independent assembly of stress granules (SGs), essential components of the stress response program. We show that selected tiRNAs inhibit protein synthesis by displacing eIF4G/eIF4A from uncapped > capped RNAs. tiRNAs also displace eIF4F, but not eIF4E:4EBP1, from isolated m(7)G cap. We identify a terminal oligoguanine motif that is required to displace the eIF4F complex, inhibit translation, and induce SG assembly. We show that the tiRNA-associated translational silencer YB-1 contributes to angiogenin-, tiRNA-, and oxidative stress-induced translational repression. Our data reveal some of the mechanisms by which stress-induced tRNA cleavage inhibits protein synthesis and activates a cytoprotective stress response program.

Y-box binding protein-1 promotes castration-resistant prostate cancer growth via androgen receptor expression.

The androgen receptor (AR) is well known to play a central role in the pathogenesis of prostate cancer (PCa). In several studies, AR was overexpressed in castration-resistant PCa (CRPC). However, the mechanism of AR overexpression in CRPC is not fully elucidated. Y-box binding protein-1 (YB-1) is a pleiotropic transcription factor that is upregulated in CPRC. We aimed to elucidate the role of YB-1 in castration resistance of PCa and identify therapeutic potential of targeting YB-1. Using immunohistochemistry, we found that nuclear YB-1 expression significantly correlated with the Gleason score and AR expression in PCa tissues. In PCa cells, YB-1 regulated AR expression at the transcriptional level. Furthermore, YB-1 expression and nuclear localization were upregulated in CRPC cells. Overexpression of AR, as well as YB-1, conferred castration-resistant growth in LNCaP and 22Rv1 cells. Conversely, knocking down YB-1 resulted in suppressed cell growth and induced apoptosis, which was more efficient than knocking down AR in LNCaP cells. In other types of PCa cells, such as CRPC cells, knocking down YB-1 resulted in a significant reduction of cell growth. In conclusion, these findings suggested that YB-1 induces castration resistance in androgen-dependent PCa cells via AR expression. Thus, YB-1 may be a promising therapeutic target for PCa, as well as CRPC.

Y-box binding protein-1 mediates profibrotic effects of calcineurin inhibitors in the kidney.

The immunosuppressive calcineurin inhibitors (CNIs) cyclosporine A (CsA) and tacrolimus are widely used in transplant organ recipients, but in the kidney allograft, they may cause tubulointerstitial as well as mesangial fibrosis, with TGF-ß believed to be a central inductor. In this study, we report that the cold-shock protein Y-box binding protein-1 (YB-1) is a TGF-ß independent downstream effector in CsA- as well as in tacrolimus- but not in rapamycin-mediated activation of rat mesangial cells (rMCs). Intracellular content of YB-1 is several-fold increased in MCs following CNI treatment in vitro and in vivo in mice. This effect ensues in a time-dependent manner, and the operative concentration range encompasses therapeutically relevant doses for CNIs. The effect of CNI on cellular YB-1 content is abrogated by specific blockade of translation, whereas retarding the transcription remains ineffective. The activation of rMCs by CNIs is accomplished by generation of reactive oxygen species. In contrast to TGF-ß-triggered reactive oxygen species generation, hydrogen peroxide especially could be identified as a potent inductor of YB-1 accumulation. In line with this, hindering TGF-ß did not influence CNI-induced YB-1 upregulation, whereas ERK/Akt pathways are involved in CNI-mediated YB-1 expression. CsA-induced YB-1 accumulation results in mRNA stabilization and subsequent generation of collagen. Our results provide strong evidence for a CNI-dependent induction of YB-1 in MCs that contributes to renal fibrosis via regulation of its own and collagen translation.

YB-1 evokes susceptibility to cancer through cytokinesis failure, mitotic dysfunction and HER2 amplification.

Y-box binding protein-1 (YB-1) expression in the mammary gland promotes breast carcinoma that demonstrates a high degree of genomic instability. In the present study, we developed a model of pre-malignancy to characterize the role of this gene during breast cancer initiation and early progression. Antibody microarray technology was used to ascertain global changes in signal transduction following the conditional expression of YB-1 in human mammary epithelial cells (HMEC). Cell cycle-associated proteins were frequently altered with the most dramatic being LIM kinase 1/2 (LIMK1/2). Consequently, the misexpression of LIMK1/2 was associated with cytokinesis failure that acted as a precursor to centrosome amplification. Detailed investigation revealed that YB-1 localized to the centrosome in a phosphorylation-dependent manner, where it complexed with pericentrin and γ-tubulin. This was found to be essential in maintaining the structural integrity and microtubule nucleation capacity of the organelle. Prolonged exposure to YB-1 led to rampant acceleration toward tumorigenesis, with the majority of cells acquiring numerical and structural chromosomal abnormalities. Slippage through the G(1)/S checkpoint due to overexpression of cyclin E promoted continued proliferation of these genomically compromised cells. As malignancy further progressed, we identified a subset of cells harboring HER2 amplification. Our results recognize YB-1 as a cancer susceptibility gene, with the capacity to prime cells for tumorigenesis.

Y-box-binding protein 1 (YB-1) and its functions.

This review describes the structure and functions of Y-box binding protein 1 (YB-1) and its homologs. Interactions of YB-1 with DNA, mRNAs, and proteins are considered. Data on the participation of YB-1 in DNA reparation and transcription, mRNA splicing and translation are systematized. Results on interactions of YB-1 with cytoskeleton components and its possible role in mRNA localization are discussed. Data on intracellular distribution of YB-1, its redistribution between the nucleus and the cytoplasm, and its secretion and extracellular functions are summarized. The effect of YB-1 on cell differentiation, its involvement in extra- and intracellular signaling pathways, and its role in early embryogenesis are described. The mechanisms of regulation of YB-1 expression in the cell are presented. Special attention is paid to the involvement of YB-1 in oncogenic cell transformation, multiple drug resistance, and dissemination of tumors. Both the oncogenic and antioncogenic activities of YB-1 are reviewed. The potential use of YB-1 in diagnostics and therapy as an early cancer marker and a molecular target is discussed.

Foxo3a suppression of urothelial cancer invasiveness through Twist1, Y-box-binding protein 1, and E-cadherin regulation.

PURPOSE: Invasion and metastasis are key steps in the progression of urothelial cancer (UC) into a critical disease. Foxo3a is a member of the Foxo transcription factor family that modulates the expression of various genes. We aimed to elucidate the role of Foxo3a in UC invasion. EXPERIMENTAL DESIGN: Foxo3a mRNA and protein expressions in UC samples were investigated by gene expression assays and immunohistochemistry, respectively. Foxo3a expression was compared with clinicopathologic characteristics and patient prognoses based on UC samples. Quantitative real-time polymerase chain reaction, Western blotting, and migration assays were also conducted in UC cells. RESULTS: Foxo3a expression decreased in invasive UC; patients with low Foxo3a expression had poor disease-free survival, cancer-specific survival, and overall survival; Foxo3a knockdown in UC cells increased cellular motility. Foxo3a negatively regulated Twist1 and Y-box-binding protein 1 (YB-1), and positively regulated E-cadherin in KK47 and TCCsup cells that expressed Twist1, but not in T24 cells that did not express Twist1. Foxo3a-associated acetyltransferase p300 and Foxo3a acetylation status also affected UC motility. CONCLUSION: The results of this study indicate that Foxo3a regulates motility of UC through negative regulation of Twist1 and YB-1, and through positive regulation of E-cadherin. This suggests that Foxo3a could act as an independent prognostic factor in UC and could represent a promising molecular target for cancer therapeutics.

Y-box protein 1 stimulates mesangial cell proliferation via activation of ERK1/2.

AIMS: To investigate the effects of Y-box protein 1 (YB-1) on the mitogen-activated protein kinase pathway to ascertain which signaling pathway is involved in YB-1-induced mesangial cell (MC) proliferation. METHODS: The rat MC line HBZY-1 was transfected with pcDNA3.1-YB-1. Cell proliferation was determined by [(3)H]thymidine incorporation, cell counting and cell-cycle analysis. The expression of cyclins was examined by real-time RT-PCR and immunoblotting analysis. Phosphorylation of c-Raf, MEK1/2, and ERK1/2 was detected by immunoblotting analysis. RESULTS: MCs transfected with YB-1 showed an increased DNA synthesis and number of cells in the S and G2 phases of the cell cycle. The expression of cyclins (cyclin A2, cyclin D1, cyclin E and p27) was increased, while p21 levels were decreased. The expression levels of phosphorylated c-Raf kinase, MEK1/2 and the ERK1/2 proteins were elevated in MCs transfected with YB-1. YB-1-stimulated cell proliferation was blocked by U0126, a specific inhibitor of ERK1/2. ERK1/2 regulated YB-1 expression in MCs stimulated with TGF-beta, an effect that was inhibited by U0126. CONCLUSIONS: YB-1 has an apparent stimulatory effect on c-Raf, MEK1/2, ERK1/2 and cell-cycle progression in MCs, after which activated ERK1/2 goes on to upregulate YB-1 expression and augment the proliferative effect of YB-1.

Differential regulation of chemokine CCL5 expression in monocytes/macrophages and renal cells by Y-box protein-1.

The Y-box protein-1 (YB-1) belongs to the family of cold shock proteins that have pleiotropic functions such as gene transcription, RNA splicing, and mRNA translation. YB-1 has a critical role in atherogenesis due to its regulatory effects on chemokine CCL5 (RANTES) gene transcription in vascular smooth muscle cells. Since CCL5 is a key mediator of kidney transplant rejection, we determined whether YB-1 is involved in allograft rejection by manipulating its expression. In human kidney biopsies, YB-1 transcripts were amplified 17-fold in acute and 21-fold in chronic allograft rejection with a close correlation between CCL5 and YB-1 mRNA expression in both conditions. Among three possible YB-1 binding sites in the CCL5 promoter, a critical element was mapped at -28/-10 bps. This site allowed up-regulation of CCL5 transcription in monocytic THP-1 and HUT78 T-cells and in human primary monocytes; however, it repressed transcription in differentiated macrophages. Conversely, YB-1 knockdown led to decreased CCL5 transcription and secretion in monocytic cells. We show that YB-1 is a cell-type specific regulator of CCL5 expression in infiltrating T-cells and monocytes/macrophages and acts as an adaptive controller of inflammation during kidney allograft rejection.

Development of drug resistance in the population of colon cancer cells under the effect of multifunctional protein YB-1.

The effects of YB-1 gene on the expression level of P-glycoprotein and drug resistance of tumor cells were studied in cultured HCT116 colon cancer cells. Transitory transfection of chimeric YB-1/GFP gene rendered HCT116 cells a selective advantage in a medium with vinblastine, which caused translocation of the chimeric protein into cell nuclei. This was paralleled by an increase in the expression of P-glycoprotein (multiple drug resistance protein).