Critical role of phosphorylation of serine 165 of YBX1 on the activation of NF-κB in colon cancer

Y-Box Binding Protein 1: Unraveling the Multifaceted Role in Cancer Development and Therapeutic Potential

Y-box binding protein 1 (YBX1), a member of the Cold Shock Domain protein family, is overexpressed in various human cancers and is recognized as an oncogenic gene associated with poor prognosis. YBX1's functional diversity arises from its capacity to interact with a broad range of DNA and RNA molecules, implicating its involvement in diverse cellular processes. Independent investigations have unveiled specific facets of YBX1's contribution to cancer development. This comprehensive review elucidates YBX1's multifaceted role in cancer across cancer hallmarks, both in cancer cell itself and the tumor microenvironment. Based on this, we proposed YBX1 as a potential target for cancer treatment. Notably, ongoing clinical trials addressing YBX1 as a target in breast cancer and lung cancer have showcased its promise for cancer therapy. The ramp up in in vitro research on targeting YBX1 compounds also underscores its growing appeal. Moreover, the emerging role of YBX1 as a neural input is also proposed where the high level of YBX1 was strongly associated with nerve cancer and neurodegenerative diseases. This review also summarized the up-to-date advanced research on the involvement of YBX1 in pancreatic cancer.

YB-1 activating cascades as potential targets in KRAS-mutated tumors

Y‑box binding protein‑1 (YB-1) is a multifunctional protein that is highly expressed in human solid tumors of various entities. Several cellular processes, e.g. cell cycle progression, cancer stemness and DNA damage signaling that are involved in the response to chemoradiotherapy (CRT) are tightly governed by YB‑1. KRAS gene with about 30% mutations in all cancers, is considered the most commonly mutated oncogene in human cancers. Accumulating evidence indicates that oncogenic KRAS mediates CRT resistance. AKT and p90 ribosomal S6 kinase are downstream of KRAS and are the major kinases that stimulate YB‑1 phosphorylation. Thus, there is a close link between the KRAS mutation status and YB‑1 activity. In this review paper, we highlight the importance of the KRAS/YB‑1 cascade in the response of KRAS-mutated solid tumors to CRT. Likewise, the opportunities to interfere with this pathway to improve CRT outcome are discussed in light of the current literature.

Fisetin overcomes non-targetability of mutated KRAS induced YB-1 signaling in colorectal cancer cells and improves radiosensitivity by blocking repair of radiation-induced DNA double-strand breaks

BACKGROUND AND PURPOSE

KRAS is frequently mutated, and the Y-box binding protein 1 (YB-1) is overexpressed in colorectal cancer (CRC). Mutant KRAS (KRASmut) stimulates YB-1 through MAPK/RSK and PI3K/AKT, independent of epidermal growth factor receptor (EGFR). The p21-activated kinase (PAK) family is a switch-site upstream of AKT and RSK. The flavonoid compound fisetin inhibits RSK-mediated YB-1 signaling. We sought the most effective molecular targeting approach that interferes with DNA double strand break (DSB) repair and induces radiosensitivity of CRC cells, independent of KRAS mutation status.

MATERIALS AND METHODS

KRAS activity and KRAS mutation were analyzed by Ras-GTP assay and NGS. Effect of dual targeting of RSK and AKT (DT), the effect of fisetin as well as targeting PAK by FRAX486 and EGFR by erlotinib on YB-1 activity was tested by Western blotting after irradiation in vitro and ex vivo. Additionally, the effect of DT and FRAX486 on DSB repair pathways was tested in cells expressing reporter constructs for the DSB repair pathways by flow cytometry analysis. Residual DSBs and clonogenicity were examined by γH2AX- and clonogenic assays, respectively.

RESULTS

Erlotinib neither blocked DSB repair nor inhibited YB-1 phosphorylation under KRAS mutation condition in vitro and ex vivo. DT and FRAX486 effectively inhibited YB-1 phosphorylation independent of KRAS mutation status and diminished homologous recombination (HR) and alternative non-homologous end joining (NHEJ) repair. DT and FRAX486 inhibited DSB repair in CaCo2 but not in isogenic KRASG12V cells. Fisetin inhibited YB-1 phosphorylation, blocked DSB repair and increased radiosensitivity, independent of KRAS mutation status.

CONCLUSION

Combination of fisetin with radiotherapy may improve CRC radiation response, regardless of KRASmut status.

The arginine methyltransferase PRMT5 promotes mucosal defense in the intestine

PRMT5 is a type II arginine methyltransferase abundantly expressed in the colonic epithelium. It is up-regulated in inflammatory bowel disease and colorectal cancer. However, its role in mucosal defense against enteric infection has not been studied. Here, we report that Prmt5 in the murine colon is up-regulated in response to Citrobacter rodentium infection. Pathogen clearance in mice with haploinsufficient expression of Prmt5 is significantly delayed compared with wildtype littermate controls. Transcriptomic analyses further reveal that PRMT5 regulates the expression of canonical crypt goblet cell genes involved in mucus production, assembly, and anti-microbial responses via methyltransferase activity-dependent and -independent mechanisms. Together, these findings uncover PRMT5 as a novel regulator of mucosal defense and a potential therapeutic target for treating intestinal diseases.

PLK1 inhibition promotes apoptosis and DNA damage in glioma stem cells by regulating the nuclear translocation of YBX1

Glioma stem cells (GSCs) are the important cause of tumorigenesis, recurrence, and chemo(radio)resistance in glioma. Targeting GSCs helps improve the outcomes of glioma treatment. Polo-like kinase 1 (PLK1) is a member of the serine/threonine protein kinase family, which is highly conserved. In recent years, it has been suggested that increased levels of PLK1 and its activity are associated with tumor progression and poor prognosis. We aimed to identify whether PLK1 plays a critical role in stemness maintenance and apoptosis regulation in GSCs. Here we identify that PLK1 inhibition can induce apoptosis and DNA damage of GSCs, we have also delineat the possible underlying molecular mechanisms: PLK1 interacts with YBX1 and directly phosphorylates serine 174 and serine 176 of YBX1. Inhibition of PLK1 reduces the phosphorylation level of YBX1, and decreased phosphorylation of YBX1 prevents its nuclear translocation, thereby inducing apoptosis and DNA damage of GSCs. We confirmed that YBX1 knockdown resulted in the apoptosis and DNA damage of GSCs. These findings uncover that PLK1 inhibition induces cell apoptosis and DNA damage in GSCs through YBX1 phosphorylation, providing new insights into the mechanism by which PLK1 inhibition contributes to the apoptosis of and DNA damage in gliomas.

Circular RNA hsa_circ_0062682 Binds to YBX1 and Promotes Oncogenesis in Hepatocellular Carcinoma

Simple Summary

Circular RNA (circRNA) have a role in carcinogenesis in different cancers, also in hepatocellular carcinoma (HCC). The transcriptome analyses of HCC tumours identified an upregulated circRNA hsa_circ_0062682. We show that this circRNA affects several aspects of oncogenesis, which are cell proliferation, migration, and invasion. Using transcriptome analyses we identified modulated signalling pathways and transcription factors, confirming the observed phenotype in cells. We identified Y-box-binding protein 1 (YBX1), a known oncogene and RNA-binding protein, as a binding partner, which was in line with transcriptome analyses. We also identified a cell-specific response to sorafenib after circRNA modulation, which is in line with a heterogeneous molecular pathology of HCC subtypes.

Abstract

Circular RNAs (circRNAs) have been shown to play an important role in the pathogenesis of hepatocellular carcinoma (HCC). By implementing available transcriptomic analyses of HCC patients, we identified an upregulated circRNA hsa_circ_0062682. Stable perturbations of hsa_circ_0062682 in Huh-7 and SNU-449 cell lines influenced colony formation, migration, cell proliferation, sorafenib sensitivity, and additionally induced morphological changes in cell lines, indicating an important role of hsa_circ_0062682 in oncogenesis. Pathway enrichment analysis and gene set enrichment analysis of the transcriptome data from hsa_circ_0062682 knockdown explained the observed phenotypes and exposed transcription factors E2F1, Sp1, HIF-1α, and NFκB1 as potential downstream targets. Biotinylated oligonucleotide pulldown combined with proteomic analyses identified protein interaction partners of which YBX1, a known oncogene, was confirmed by RNA immunoprecipitation. Furthermore, we discovered a complex cell-type-specific phenotype in response to the oncogenic potential of hsa_circ_0062682. This finding is in line with different classes of HCC tumours, and more studies are needed to shed a light on the molecular complexity of liver cancer.

Proteomics of post-translational modifications in colorectal cancer: Discovery of new biomarkers

Colorectal cancer (CRC) is one of the costliest health problems and ranks second in cancer-related mortality in developed countries. With the aid of proteomics, many protein biomarkers for the diagnosis, prognosis, and precise management of CRC have been identified. Furthermore, some protein biomarkers exhibit structural diversity after modifications. Post-translational modifications (PTMs), most of which are catalyzed by a variety of enzymes, extensively increase protein diversity and are involved in many complex and dynamic cellular processes through the regulation of protein function. Accumulating evidence suggests that abnormal PTM events are associated with a variety of human diseases, such as CRC, thus highlighting the need for studying PTMs to discover both the molecular mechanisms and therapeutic targets of CRC. In this review, we begin with a brief overview of the importance of protein PTMs, discuss the general strategies for proteomic profiling of several key PTMs (including phosphorylation, acetylation, glycosylation, ubiquitination, methylation, and citrullination), shift the emphasis to describing the specific methods used for delineating the global landscapes of each of these PTMs, and summarize the recent applications of these methods to explore the potential roles of the PTMs in CRC. Finally, we discuss the current status of PTM research on CRC and provide future perspectives on how PTM regulation can play an essential role in translational medicine for early diagnosis, prognosis stratification, and therapeutic intervention in CRC.

YB-1 as an Oncoprotein: Functions, Regulation, Post-Translational Modifications, and Targeted Therapy

Y box binding protein 1 (YB-1) is a protein with a highly conserved cold shock domain (CSD) that also belongs to the family of DNA- and RNA-binding proteins. YB-1 is present in both the nucleus and cytoplasm and plays versatile roles in gene transcription, RNA splicing, DNA damage repair, cell cycle progression, and immunity. Cumulative evidence suggests that YB-1 promotes the progression of multiple tumor types and serves as a potential tumor biomarker and therapeutic target. This review comprehensively summarizes the emerging functions, mechanisms, and regulation of YB-1 in cancers, and further discusses targeted strategies.

Diverse Regulation of YB-1 and YB-3 Abundance in Mammals

YB proteins are DNA/RNA binding proteins, members of the family of proteins with cold shock domain. Role of YB proteins in the life of cells, tissues, and whole organisms is extremely important. They are involved in transcription regulation, pre-mRNA splicing, mRNA translation and stability, mRNA packaging into mRNPs, including stress granules, DNA repair, and many other cellular events. Many processes, from embryonic development to aging, depend on when and how much of these proteins have been synthesized. Here we discuss regulation of the levels of YB-1 and, in part, of its homologs in the cell. Because the amount of YB-1 is immediately associated with its functioning, understanding the mechanisms of regulation of the protein amount invariably reveals the events where YB-1 is involved. Control over the YB-1 abundance may allow using this gene/protein as a therapeutic target in cancers, where an increased expression of the YBX1 gene often correlates with the disease severity and poor prognosis.

YB-1 Phosphorylation at Serine 209 Inhibits Its Nuclear Translocation

YB-1 is a multifunctional DNA- and RNA-binding protein involved in cell proliferation, differentiation, and migration. YB-1 is a predominantly cytoplasmic protein that is transported to the nucleus in certain conditions, including DNA-damaging stress, transcription inhibition, and viral infection. In tumors, YB-1 nuclear localization correlates with high aggressiveness, multidrug resistance, and a poor prognosis. It is known that posttranslational modifications can regulate the nuclear translocation of YB-1. In particular, well-studied phosphorylation at serine 102 (S102) activates YB-1 nuclear import. Here, we report that Akt kinase phosphorylates YB-1 in vitro at serine 209 (S209), which is located in the vicinity of the YB-1 nuclear localization signal. Using phosphomimetic substitutions, we showed that S209 phosphorylation inhibits YB-1 nuclear translocation and prevents p-S102-mediated YB-1 nuclear import.

Protein arginine N-methyltransferase 5 in colorectal carcinoma: Insights into mechanisms of pathogenesis and therapeutic strategies

Protein arginine N-methyltransferase 5 (PRMT5) enzyme is one of the eight canonical PRMTs, classified as a type II PRMT, induces arginine monomethylation and symmetric dimethylation. PRMT5 is known to be overexpressed in multiple cancer types, including colorectal cancer (CRC), where its overexpression is associated with poor survival. Recent studies have shown that upregulation of PRMT5 induces tumor growth and metastasis in CRC. Moreover, various novel PRMT5 inhibitors tested on CRC cell lines showed promising anticancer effects. Also, it was suggested that PRMT5 could be a valid biomarker for CRC diagnosis and prognosis. Hence, a deeper understanding of PRMT5-mediated CRC carcinogenesis could provide new avenues towards developing a targeted therapy. In this study, we started with in silico analysis correlating PRMT5 expression in CRC patients as a prelude to further our investigation of its role in CRC. We then carried out a comprehensive review of the scientific literature that dealt with the role(s) of PRMT5 in CRC pathogenesis, diagnosis, and prognosis. Also, we have summarized key findings from in vitro research using various therapeutic agents and strategies directly targeting PRMT5 or disrupting its function. In conclusion, PRMT5 seems to play a significant role in the pathogenesis of CRC; therefore, its prognostic and therapeutic potential merits further investigation.

Potential therapeutic strategies for targeting Y-box-binding protein 1 in cancers

As one of the most conservative proteins in evolution, Y-box-binding protein 1 (YB-1) has long been considered as a potential cancer target. YB-1 is usually poorly expressed in normal cells and exerts cellular physiological functions such as DNA repair, pre-mRNA splicing and mRNA stabilizing. In cancer cells, the expression of YB-1 is up-regulated and undergoes nuclear translocation and contributes to tumorigenesis, angiogenesis, tumor proliferation, invasion, migration and chemotherapy drug resistance. During the past decades, a variety of pharmacological tools such as siRNA, shRNA, microRNA, circular RNA, lncRNA and various compounds have been developed to target YB-1 for cancer therapy. In this review, we describe the physiological characteristics of YB-1 in detail, highlight the role of YB-1 in tumors and summarize the current therapeutic methods for targeting YB-1 in cancer.

A comprehensive review of the functions of YB-1 in cancer stemness, metastasis and drug resistance

The Y Box binding protein 1 (YB-1) is a member of the highly conserved Cold Shock Domain protein family with multifunctional properties both in the cytoplasm and inside the nucleus. YB-1 is also involved in various cellular functions, including regulation of transcription, mRNA stability, and splicing. Recent studies have associated YB-1 with the regulation of the malignant phenotypes in several tumor types. In this review article, we provide an in-depth and expansive review of the literature pertaining to the multiple physiological functions of YB-1. We will also review the role of YB-1 in cancer development, progression, metastasis, and drug resistance in various malignancies, with more weight on literature published in the last decade. The methodology included querying databases PubMed, Embase, and Google Scholar for Y box binding protein 1, YB-1, YBX1, and Y-box-1.

Novel Insights into YB-1 Signaling and Cell Death Decisions

YB-1 belongs to the evolutionarily conserved cold-shock domain protein family of RNA binding proteins. YB-1 is a well-known transcriptional and translational regulator, involved in cell cycle progression, DNA damage repair, RNA splicing, and stress responses. Cell stress occurs in many forms, e.g., radiation, hyperthermia, lipopolysaccharide (LPS) produced by bacteria, and interferons released in response to viral infection. Binding of the latter factors to their receptors induces kinase activation, which results in the phosphorylation of YB-1. These pathways also activate the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), a well-known transcription factor. NF-κB is upregulated following cellular stress and orchestrates inflammatory responses, cell proliferation, and differentiation. Inflammation and cancer are known to share common mechanisms, such as the recruitment of infiltrating macrophages and development of an inflammatory microenvironment. Several recent papers elaborate the role of YB-1 in activating NF-κB and signaling cell survival. Depleting YB-1 may tip the balance from survival to enhanced apoptosis. Therefore, strategies that target YB-1 might be a viable therapeutic option to treat inflammatory diseases and improve tumor therapy.

Y-Box Binding Protein 1 Regulates Angiogenesis in Bladder Cancer via miR-29b-3p-VEGFA Pathway

Angiogenesis plays a vital role in the development of bladder cancer (BC). The Y-box-binding protein 1 (YB-1) is a well-known oncoprotein which is closely related to angiogenesis of tumors, but the relationship and mechanism of YB-1 and angiogenesis in BC remain unclear. Based on 56 clinical BC specimens, this study found that high expression of YB-1 samples demonstrated a higher expression of vascular endothelial growth factor A (VEGFA) than those of YB-1 low expression. Subsequently, the expression of YB-1 and miR-29b-3p was regulated in the BC cell lines where we noted that YB-1 promoted VEGFA expression by downregulating the expression of miR- 29b-3p. The ability of BC cells to induce angiogenesis decreased after YB-1 was knocked down. Moreover, the in vivo study further confirmed that YB-1 promotes angiogenesis in BC. Our findings enhance the understanding of how YB-1 promotes angiogenesis in BC and provide evidence for YB-1 as a therapeutic target of BC. Moreover, this may provide new inspiration for miRNAs replacement therapies.

Targeting the Y-box Binding Protein-1 Axis to Overcome Radiochemotherapy Resistance in Solid Tumors

Multifunctional Y-box binding protein-1 (YB-1) is highly expressed in different human solid tumors and is involved in various cellular processes. DNA damage is the major mechanism by which radiochemotherapy (RCT) induces cell death. On induction of DNA damage, a multicomponent signal transduction network, known as the DNA damage response, is activated to induce cell cycle arrest and initiate DNA repair, which protects cells against damage. YB-1 regulates nearly all cancer hallmarks described to date by participating in DNA damage response, gene transcription, mRNA splicing, translation, and tumor stemness. YB-1 lacks kinase activity, and p90 ribosomal S6 kinase and AKT are the key kinases within the RAS/mitogen-activated protein kinase and phosphoinositide 3-kinase pathways that directly activate YB-1. Thus, the molecular targeting of ribosomal S6 kinase and AKT is thought to be the most effective strategy for blocking the cellular function of YB-1 in human solid tumors. In this review, after describing the prosurvival effect of YB-1 with a focus on DNA damage repair and cancer cell stemness, clinical evidence will be provided indicating an inverse correlation between YB-1 expression and the treatment outcome of solid tumors after RCT. In the interest of being concise, YB-1 signaling cascades will be briefly discussed and the current literature on YB-1 posttranslational modifications will be summarized. Finally, the current status of targeting the YB-1 axis, especially in combination with RCT, will be highlighted.

The long non-coding RNA MIR31HG regulates the senescence associated secretory phenotype

Oncogene-induced senescence provides a barrier against malignant transformation. However, it can also promote cancer through the secretion of a plethora of factors released by senescent cells, called the senescence associated secretory phenotype (SASP). We have previously shown that in proliferating cells, nuclear lncRNA MIR31HG inhibits p16/CDKN2A expression through interaction with polycomb repressor complexes and that during BRAF-induced senescence, MIR31HG is overexpressed and translocates to the cytoplasm. Here, we show that MIR31HG regulates the expression and secretion of a subset of SASP components during BRAF-induced senescence. The SASP secreted from senescent cells depleted for MIR31HG fails to induce paracrine invasion without affecting the growth inhibitory effect. Mechanistically, MIR31HG interacts with YBX1 facilitating its phosphorylation at serine 102 (p-YBX1^S102) by the kinase RSK. p-YBX1^S102 induces IL1A translation which activates the transcription of the other SASP mRNAs. Our results suggest a dual role for MIR31HG in senescence depending on its localization and points to the lncRNA as a potential therapeutic target in the treatment of senescence-related pathologies.

Senescence-associated secretory phenotype (SASP) involves secretion of factors such as pro-inflammatory cytokines. Here the authors show that MIR31HG regulates the expression and secretion of a subset of SASP components that induce paracrine invasion, through interaction with YBX1 and induction of IL1A translation.

Phosphorylation of the Regulators, a Complex Facet of NF-κB Signaling in Cancer

The nuclear factor kappa B (NF-κB) is a ubiquitous transcription factor central to inflammation and various malignant diseases in humans. The regulation of NF-κB can be influenced by a myriad of post-translational modifications (PTMs), including phosphorylation, one of the most popular PTM formats in NF-κB signaling. The regulation by phosphorylation modification is not limited to NF-κB subunits, but it also encompasses the diverse regulators of NF-κB signaling. The differential site-specific phosphorylation of NF-κB itself or some NF-κB regulators can result in dysregulated NF-κB signaling, often culminating in events that induce cancer progression and other hyper NF-κB related diseases, such as inflammation, cardiovascular diseases, diabetes, as well as neurodegenerative diseases, etc. In this review, we discuss the regulatory role of phosphorylation in NF-κB signaling and the mechanisms through which they aid cancer progression. Additionally, we highlight some of the known and novel NF-κB regulators that are frequently subjected to phosphorylation. Finally, we provide some future perspectives in terms of drug development to target kinases that regulate NF-κB signaling for cancer therapeutic purposes.

Blocking Y-Box Binding Protein-1 through Simultaneous Targeting of PI3K and MAPK in Triple Negative Breast Cancers

Simple Summary

Triple-negative breast cancer (TNBC) is associated with the high rates of relapse and metastasis and poor survival. YB-1 is overexpressed in TNBC tumor tissues. In the present study, we demonstrated that S102 phosphorylation of YB-1 in TNBC cell lines depend on the mutation status of the components of the MAPK/ERK and PI3K/Akt pathways. Simultaneous targeting of MEK and PI3K was found to be the most effective approach to block YB-1 phosphorylation and to inhibit YB-1 dependent cell proliferation. YBX1 knockout was sufficient to block TNBC tumor growth.

Abstract

The multifunctional protein Y-box binding protein-1 (YB-1) regulates all the so far described cancer hallmarks including cell proliferation and survival. The MAPK/ERK and PI3K/Akt pathways are also the major pathways involved in cell growth, proliferation, and survival, and are the frequently hyperactivated pathways in human cancers. A gain of function mutation in KRAS mainly leads to the constitutive activation of the MAPK pathway, while the activation of the PI3K/Akt pathway occurs either through the loss of PTEN or a gain of function mutation of the catalytic subunit alpha of PI3K (PIK3CA). In this study, we investigated the underlying signaling pathway involved in YB-1 phosphorylation at serine 102 (S102) in KRAS(G13D)-mutated triple-negative breast cancer (TNBC) MDA-MB-231 cells versus PIK3CA(H1047R)/PTEN(E307K) mutated TNBC MDA-MB-453 cells. Our data demonstrate that S102 phosphorylation of YB-1 in KRAS-mutated cells is mainly dependent on the MAPK/ERK pathway, while in PIK3CA/PTEN-mutated cells, YB-1 S102 phosphorylation is entirely dependent on the PI3K/Akt pathway. Independent of the individual dominant pathway regulating YB-1 phosphorylation, dual targeting of MEK and PI3K efficiently inhibited YB-1 phosphorylation and blocked cell proliferation. This represents functional crosstalk between the two pathways. Our data obtained from the experiments, applying pharmacological inhibitors and genetic approaches, shows that YB-1 is a key player in cell proliferation, clonogenic activity, and tumor growth of TNBC cells through the MAPK and PI3K pathways. Therefore, dual inhibition of these two pathways or single targeting of YB-1 may be an effective strategy to treat TNBC.

PRMT5-mediated methylation of YBX1 regulates NF-κB activity in colorectal cancer

The multifunctional protein Y-box binding protein 1 (YBX1), is a critical regulator of transcription and translation, and is widely recognized as an oncogenic driver in several solid tumors, including colorectal cancer (CRC). However, very little is known about the upstream or downstream factors that underlie YBX1′s regulation and involvement in CRC. Previously, we demonstrated that YBX1 overexpression correlated with potent activation of nuclear factor κB (NF-κB), a well-known transcription factor believed to be crucial in CRC progression. Here, we report a novel interaction between NF-κB, YBX1 and protein arginine methyltransferase 5 (PRMT5). Our findings reveal for the first time that PRMT5 catalyzes methylation of YBX1 at arginine 205 (YBX1-R205me2), an event that is critical for YBX1-mediated NF-κB activation and its downstream target gene expression. Importantly, when WT-YBX1 is overexpressed, this methylation exists under basal (unstimulated) conditions and is further augmented upon interleukin-1β (IL-1β) stimulation. Mechanistically, co-immunoprecipitation studies reveal that the R205 to alanine (A) mutant of YBX1 (YBX1-R205A) interacted less well with the p65 subunit of NF-κB and attenuated the DNA binding ability of p65. Importantly, overexpression of YBX1-R205A significantly reduced cell growth, migration and anchorage-independent growth of CRC cells. Collectively, our findings shed important light on the regulation of a novel PRMT5/YBX1/NF-κB axis through PRMT5-mediated YBX1-R205 methylation. Given the fact that PRMT5, YBX1 and NF-κB are all among top crucial factors in cancer progression, pharmacological disruption of this pivotal axis could serve as the basis for new therapeutics for CRC and other PRMT5/YBX1/NF-κB-associated cancers.

YB-1 Interferes with TNFα-TNFR Binding and Modulates Progranulin-Mediated Inhibition of TNFα Signaling

Inflammation and an influx of macrophages are common elements in many diseases. Among pro-inflammatory cytokines, tumor necrosis factor α (TNFα) plays a central role by amplifying the cytokine network. Progranulin (PGRN) is a growth factor that binds to TNF receptors and interferes with TNFα-mediated signaling. Extracellular PGRN is processed into granulins by proteases released from immune cells. PGRN exerts anti-inflammatory effects, whereas granulins are pro-inflammatory. The factors coordinating these ambivalent functions remain unclear. In our study, we identify Y-box binding protein-1 (YB-1) as a candidate for this immune-modulating activity. Using a yeast-2-hybrid assay with YB-1 protein as bait, clones encoding for progranulin were selected using stringent criteria for strong interaction. We demonstrate that at physiological concentrations, YB-1 interferes with the binding of TNFα to its receptors in a dose-dependent manner using a flow cytometry-based binding assay. We show that YB-1 in combination with progranulin interferes with TNFα-mediated signaling, supporting the functionality with an NF-κB luciferase reporter assay. Together, we show that YB-1 displays immunomodulating functions by affecting the binding of TNFα to its receptors and influencing TNFα-mediated signaling via its interaction with progranulin.

Role of Inflammation in the Development of Colorectal Cancer

Chronic inflammation can lead to the development of many diseases, including cancer. Inflammatory bowel disease (IBD) that includes both ulcerative colitis (UC) and Crohnmp's disease (CD) are risk factors for the development of colorectal cancer (CRC). Many cytokines produced primarily by the gut immune cells either during or in response to localized inflammation in the colon and rectum are known to stimulate the complex interactions between the different cell types in the gut environment resulting in acute inflammation. Subsequently, chronic inflammation, together with genetic and epigenetic changes, have been shown to lead to the development and progression of CRC. Various cell types present in the colon, such as enterocytes, Paneth cells, goblet cells, and macrophages, express receptors for inflammatory cytokines and respond to tumor necrosis factor-alpha (TNF-α), interleukin-1 beta (IL-1β), IL-6, and other cytokines. Among the several cytokines produced, TNF-α and IL-1β are the key pro-inflammatory molecules that play critical roles in the development of CRC. The current review is intended to consolidate the published findings to focus on the role of pro-inflammatory cytokines, namely TNF-α and IL-1β, on inflammation (and the altered immune response) in the gut, to better understand the development of CRC in IBD, using various experimental model systems, preclinical and clinical studies. Moreover, this review also highlights the current therapeutic strategies available (monotherapy and combination therapy) to alleviate the symptoms or treat inflammation-associated CRC by using monoclonal antibodies or aptamers to block pro-inflammatory molecules, inhibitors of tyrosine kinases in the inflammatory signaling cascade, competitive inhibitors of pro-inflammatory molecules, and the nucleic acid drugs like small activating RNAs (saRNAs) or microRNA (miRNA) mimics to activate tumor suppressor or repress oncogene/pro-inflammatory cytokine gene expression.

Critical Role for Cold Shock Protein YB-1 in Cytokinesis

Simple Summary

Y-box-binding protein-1, YB-1, plays an important role in regulating the cell cycle, although precisely how it does the is unknown. Using live cell imaging, we show that YB-1 is essential for initiating the last step of cell division (cytokinesis), required for creation of two daughter cells. Using confocal microscopy we showed that YB-1 regulates the spatial distribution of key proteins essential for cytokinesis to occur and that this required YB-1 to be phosphorylated on several residues. In-silico modeling demonstrated that modifications at these residues resulted in conformational changes in YB-1 protein allowing it to interact with proteins essential for cytokinesis. As many cancers have high levels YB-1 and these are associated with poor prognosis, our data suggest developing small molecule inhibitors to block YB-1 phosphorylation could be a novel approach to cancer therapy.

Abstract

High levels of the cold shock protein Y-box-binding protein-1, YB-1, are tightly correlated with increased cell proliferation and progression. However, the precise mechanism by which YB-1 regulates proliferation is unknown. Here, we found that YB-1 depletion in several cancer cell lines and in immortalized fibroblasts resulted in cytokinesis failure and consequent multinucleation. Rescue experiments indicated that YB-1 was required for completion of cytokinesis. Using confocal imaging we found that YB-1 was essential for orchestrating the spatio-temporal distribution of the microtubules, β-actin and the chromosome passenger complex (CPC) to define the cleavage plane. We show that phosphorylation at six serine residues was essential for cytokinesis, of which novel sites were identified using mass spectrometry. Using atomistic modelling we show how phosphorylation at multiple sites alters YB-1 conformation, allowing it to interact with protein partners. Our results establish phosphorylated YB-1 as a critical regulator of cytokinesis, defining precisely how YB-1 regulates cell division.

YB-1 Mediates TNF-Induced Pro-Survival Signaling by Regulating NF-κB Activation

Cell fate decisions regulating survival and death are essential for maintaining tissue homeostasis; dysregulation thereof can lead to tumor development. In some cases, survival and death are triggered by the same receptor, e.g., tumor necrosis factor (TNF)-receptor 1 (TNFR1). We identified a prominent role for the cold shock Y-box binding protein-1 (YB-1) in the TNF-induced activation and nuclear translocation of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) p65. In the absence of YB-1, the expression of TNF receptor-associated factor 2 (TRAF2), a central component of the TNF receptor signaling complex required for NF-κB activation, is significantly reduced. Therefore, we hypothesized that the loss of YB-1 results in a destabilization of TRAF2. Consistent with this hypothesis, we observed that YB-1-deficient cells were more prone to TNF-induced apoptotic cell death. We observed enhanced effector caspase-3 activation and could successfully rescue the cells using the pan-caspase inhibitor zVAD-fmk, but not necrostatin-1. Taken together, our results indicate that YB-1 plays a central role in promoting cell survival through NF-κB activation and identifies a novel mechanism by which enhanced YB-1 expression may contribute to tumor development.

Integrin β8 facilitates tumor growth and drug resistance through a Y-box binding protein 1-dependent signaling pathway in bladder cancer

The transmembrane receptors integrins are the bridges for cell-cell or cell-ECM interaction, which is strictly correlated to cancer development in several tumor types. Here, we revealed that integrin β8 serves as a driver to mediate sustained growth of bladder cancer and development of drug resistance. The elevated expression of integrin β8 was observed in highly malignant bladder tumor tissues from patients. The in vitro and in vivo results further indicated that integrin β8 overexpression in Biu87/T24 bladder cancer could mediate and strengthen cell proliferation and resistance to mitomycin C and hydroxycamptothecin. Mechanistically, integrin β8 on the cellular surface might recruit phosphorylated Y-box binding protein 1, leading to the activation of c-Myc and nuclear factor-κB signals. Pharmacological targeting of integrin β8 by Arg-Gly-Asp-Ser efficiently suppressed sustained growth and drug resistance in bladder cancer cells. Our findings identified integrin β8 as a marker of bladder cancer diagnosis and development, and provides an innovative approach for clinical bladder cancer therapy.

Oligomeric amyloid-β induces early and widespread changes to the proteome in human iPSC-derived neurons

Alzheimer's disease (AD) is the most common form of dementia globally and is characterized by aberrant accumulations of amyloid-beta (Aβ) and tau proteins. Oligomeric forms of these proteins are believed to be most relevant to disease progression, with oligomeric amyloid-β (oAβ) particularly implicated in AD. oAβ pathology spreads among interconnected brain regions, but how oAβ induces pathology in these previously unaffected neurons requires further study. Here, we use well characterized iPSC-derived human neurons to study the early changes to the proteome and phosphoproteome after 24 h exposure to oAβ 1-42. Using nLC-MS/MS and label-free quantification, we identified several proteins that are differentially regulated in response to acute oAβ challenge. At this early timepoint, oAβ induced the decrease of TDP-43, heterogeneous nuclear ribonucleoproteins (hnRNPs), and coatomer complex I (COPI) proteins. Conversely, increases were observed in 20 S proteasome subunits and vesicle associated proteins VAMP1/2, as well as the differential phosphorylation of tau at serine 208. These changes show that there are widespread alterations to the neuronal proteome within 24 h of oAβ uptake, including proteins previously not shown to be related to neurodegeneration. This study provides new targets for the further study of early mediators of AD pathogenesis.

Y-Box Binding Proteins in mRNP Assembly, Translation, and Stability Control

Y-box binding proteins (YB proteins) are DNA/RNA-binding proteins belonging to a large family of proteins with the cold shock domain. Functionally, these proteins are known to be the most diverse, although the literature hardly offers any molecular mechanisms governing their activities in the cell, tissue, or the whole organism. This review describes the involvement of YB proteins in RNA-dependent processes, such as mRNA packaging into mRNPs, mRNA translation, and mRNA stabilization. In addition, recent data on the structural peculiarities of YB proteins underlying their interactions with nucleic acids are discussed.

Aurora Kinase A-YBX1 Synergy Fuels Aggressive Oncogenic Phenotypes and Chemoresistance in Castration-Resistant Prostate Cancer

Multifunctional protein YBX1 upregulation promotes castration-resistant prostate cancer (CRPC). However, YBX1 protein abundance, but not its DNA status or mRNA levels, predicts CRPC recurrence, although the mechanism remains unknown. Similarly, the mechanism by which YBX1 regulates androgen receptor (AR) signaling remains unclear. We uncovered the first molecular mechanism of YBX1 upregulation at a post-translational level. YBX1 was identified as an Aurora Kinase-A (AURKA) substrate using a chemical screen. AURKA phosphorylates YBX1 at two key residues, which stabilizes it and promotes its nuclear translocation. YBX1 reciprocates and stabilizes AURKA, thereby initiating a synergistic loop. Notably, phospho-resistant YBX1 is dominant-negative and fully inhibits epithelial to mesenchymal transition, chemoresistance, drug-resistance and tumorigenesis in vivo. Unexpectedly, we further observed that YBX1 upregulates AR post-translationally by preventing its ubiquitylation, but not by increasing its transcription as reported before. Uncovering YBX1-mediated AR stabilization is highly significant due to AR's critical role in both androgen-sensitive prostate cancer and CRPC. As YBX1 inhibitors are unknown, AURKA inhibitors provide a potent tool to degrade both YBX1 and AR simultaneously. Finally, this is the first study to show a reciprocal loop between YBX1 and its kinase, indicating that their concomitant inhibition will be act synergistically for CRPC therapy.

Dephosphorylation of YB-1 is Required for Nuclear Localisation During G2 Phase of the Cell Cycle

Elevated levels of nuclear Y-box binding protein 1 (YB-1) are linked to poor prognosis in cancer. It has been proposed that entry into the nucleus requires specific proteasomal cleavage. However, evidence for cleavage is contradictory and high YB-1 levels are prognostic regardless of cellular location. Here, using confocal microscopy and mass spectrometry, we find no evidence of specific proteolytic cleavage. Doxorubicin treatment, and the resultant G₂ arrest, leads to a significant increase in the number of cells where YB-1 is not found in the cytoplasm, suggesting that its cellular localisation is variable during the cell cycle. Live cell imaging reveals that the location of YB-1 is linked to progression through the cell cycle. Primarily perinuclear during G₁ and S phases, YB-1 enters the nucleus as cells transition through late G₂/M and exits at the completion of mitosis. Atomistic modelling and molecular dynamics simulations show that dephosphorylation of YB-1 at serine residues 102, 165 and 176 increases the accessibility of the nuclear localisation signal (NLS). We propose that this conformational change facilitates nuclear entry during late G₂/M. Thus, the phosphorylation status of YB-1 determines its cellular location.

Inhibition of Transcription Induces Phosphorylation of YB-1 at Ser102 and Its Accumulation in the Nucleus

The Y-box binding protein 1 (YB-1) is an RNA/DNA-binding protein regulating gene expression in the cytoplasm and the nucleus. Although mostly cytoplasmic, YB-1 accumulates in the nucleus under stress conditions. Its nuclear localization is associated with aggressiveness and multidrug resistance of cancer cells, which makes the understanding of the regulatory mechanisms of YB-1 subcellular distribution essential. Here, we report that inhibition of RNA polymerase II (RNAPII) activity results in the nuclear accumulation of YB-1 accompanied by its phosphorylation at Ser102. The inhibition of kinase activity reduces YB-1 phosphorylation and its accumulation in the nucleus. The presence of RNA in the nucleus is shown to be required for the nuclear retention of YB-1. Thus, the subcellular localization of YB-1 depends on its post-translational modifications (PTMs) and intracellular RNA distribution.

Co-targeting CK2α and YBX1 suppresses tumor progression by coordinated inhibition of the PI3K/AKT signaling pathway

Protein kinase CK2 alpha (CK2α) is involved in the development of multiple malignancies. Overexpression of Y-box binding protein 1 (YBX1) is related to tumor proliferation, drug resistance, and poor prognosis. Studies have demonstrated that both CK2 and YBX1 could regulate the PI3K/AKT pathway. In addition, we predicted that CK2 might be the upstream kinase of YBX1 through the Human Protein Reference Database (HPRD). Herein, we hypothesize that CK2 may interact with YBX1 and they regulate the PI3K/AKT signaling pathway together. Expressions of CK2α and YBX1 in cancer cell lines were evaluated by immunoblotting. The results showed that CK2α could regulate the expression of YBX1 at the transcriptional level, which is dependent on its enzymatic activity. Synergistic effects of PI3K/AKT pathway inactivation could be observed through combined inhibition of CK2α and YBX1, and YBX1 was required for CK2α-induced PI3K/AKT pathway activation. Further results demonstrated that CK2α could interact with YBX1 and PI3K/AKT antagonist decreased cell resistance to doxorubicin induced by co-activation of CK2α and YBX1. These results indicated that combined inhibition of CK2α and YBX1 showed synergistic effects in inactivating the PI3K/AKT signaling pathway and may be one of the mechanisms involved in tumor growth and migration.

Why Be One Protein When You Can Affect Many? The Multiple Roles of YB-1 in Lung Cancer and Mesothelioma

Lung cancers and malignant pleural mesothelioma (MPM) have some of the worst 5-year survival rates of all cancer types, primarily due to a lack of effective treatment options for most patients. Targeted therapies have shown some promise in thoracic cancers, although efficacy is limited only to patients harboring specific mutations or target expression. Although a number of actionable mutations have now been identified, a large population of thoracic cancer patients have no therapeutic options outside of first-line chemotherapy. It is therefore crucial to identify alternative targets that might lead to the development of new ways of treating patients diagnosed with these diseases. The multifunctional oncoprotein Y-box binding protein-1 (YB-1) could serve as one such target. Recent studies also link this protein to many inherent behaviors of thoracic cancer cells such as proliferation, invasion, metastasis and involvement in cancer stem-like cells. Here, we review the regulation of YB-1 at the transcriptional, translational, post-translational and sub-cellular levels in thoracic cancer and discuss its potential use as a biomarker and therapeutic target.

Identification of Prognostic Biomarker Signatures and Candidate Drugs in Colorectal Cancer: Insights from Systems Biology Analysis

Background and objectives: Colorectal cancer (CRC) is the second most common cause of cancer-related death in the world, but early diagnosis ameliorates the survival of CRC. This report aimed to identify molecular biomarker signatures in CRC. Materials and Methods: We analyzed two microarray datasets (GSE35279 and GSE21815) from the Gene Expression Omnibus (GEO) to identify mutual differentially expressed genes (DEGs). We integrated DEGs with protein–protein interaction and transcriptional/post-transcriptional regulatory networks to identify reporter signaling and regulatory molecules; utilized functional overrepresentation and pathway enrichment analyses to elucidate their roles in biological processes and molecular pathways; performed survival analyses to evaluate their prognostic performance; and applied drug repositioning analyses through Connectivity Map (CMap) and geneXpharma tools to hypothesize possible drug candidates targeting reporter molecules. Results: A total of 727 upregulated and 99 downregulated DEGs were detected. The PI3K/Akt signaling, Wnt signaling, extracellular matrix (ECM) interaction, and cell cycle were identified as significantly enriched pathways. Ten hub proteins (ADNP, CCND1, CD44, CDK4, CEBPB, CENPA, CENPH, CENPN, MYC, and RFC2), 10 transcription factors (ETS1, ESR1, GATA1, GATA2, GATA3, AR, YBX1, FOXP3, E2F4, and PRDM14) and two microRNAs (miRNAs) (miR-193b-3p and miR-615-3p) were detected as reporter molecules. The survival analyses through Kaplan–Meier curves indicated remarkable performance of reporter molecules in the estimation of survival probability in CRC patients. In addition, several drug candidates including anti-neoplastic and immunomodulating agents were repositioned. Conclusions: This study presents biomarker signatures at protein and RNA levels with prognostic capability in CRC. We think that the molecular signatures and candidate drugs presented in this study might be useful in future studies indenting the development of accurate diagnostic and/or prognostic biomarker screens and efficient therapeutic strategies in CRC.

Cold shock proteins: from cellular mechanisms to pathophysiology and disease

Cold shock proteins are multifunctional RNA/DNA binding proteins, characterized by the presence of one or more cold shock domains. In humans, the best characterized members of this family are denoted Y-box binding proteins, such as Y-box binding protein-1 (YB-1). Biological activities range from the regulation of transcription, splicing and translation, to the orchestration of exosomal RNA content. Indeed, the secretion of YB-1 from cells via exosomes has opened the door to further potent activities. Evidence links a skewed cold shock protein expression pattern with cancer and inflammatory diseases. In this review the evidence for a causative involvement of cold shock proteins in disease development and progression is summarized. Furthermore, the potential application of cold shock proteins for diagnostics and as targets for therapy is elucidated.

Stress-Induced Phosphorylation of Nuclear YB-1 Depends on Nuclear Trafficking of p90 Ribosomal S6 Kinase

Ionizing radiation (IR) and epidermal growth factor (EGF) stimulate Y-box binding protein-1 (YB-1) phosphorylation at Ser-102 in KRAS wild-type (KRASwt) cells, whereas in KRAS mutated (KRASmut) cells, YB-1 is constitutively phosphorylated, independent of IR or EGF. YB-1 activity stimulates the repair of IR-induced DNA double-strand breaks (DSBs) in the nucleus. Thus far, the YB-1 nuclear translocation pattern after cell exposure to various cellular stressors is not clear. In the present study, we investigated the pattern of YB-1 phosphorylation and its possible translocation to the nucleus in KRASwt cells after exposure to IR, EGF treatment, and conditional expression of mutated KRAS(G12V). IR, EGF, and conditional KRAS(G12V) expression induced YB-1 phosphorylation in both the cytoplasmic and nuclear fractions of KRASwt cells. None of the stimuli induced YB-1 nuclear translocation, while p90 ribosomal s6 kinase (RSK) translocation was enhanced in KRASwt cells after any of the stimuli. EGF-induced RSK translocation to the nucleus and nuclear YB-1 phosphorylation were completely blocked by the EGF receptor kinase inhibitor erlotinib. Likewise, RSK inhibition blocked RSK nuclear translocation and nuclear YB-1 phosphorylation after irradiation and KRAS(G12V) overexpression. In summary, acute stimulation of YB-1 phosphorylation does not lead to YB-1 translocation from the cytoplasm to the nucleus. Rather, irradiation, EGF treatment, or KRAS(G12V) overexpression induces RSK activation, leading to its translocation to the nucleus, where it activates already-existing nuclear YB-1. Our novel finding illuminates the signaling pathways involved in nuclear YB-1 phosphorylation and provides a rationale for designing appropriate targeting strategies to block YB-1 in oncology as well as in radiation oncology.

Crosstalk between Akt signaling and cold shock proteins in mediating invasive cell phenotypes

Cold shock proteins are up-regulated by cellular stress and orchestrate inflammatory responses, cell proliferation, and differentiation. Enhanced cold shock protein expression promotes malignant cell transformation; up-regulation is detected in most cancers and associated with poor prognosis. Akt1, a serine/threonine kinase, is a potent oncogene, which activates pro-proliferative and anti-apoptotic signaling pathways, and phosphorylates the cold shock domain. Unexpectedly, chicken-YB-1 abrogates PI3K-Akt-dependent oncogenic cell transformation in embryonic fibroblasts. Here, we addressed the question whether chicken and human Y-box binding protein-1 (YB-1) act differently on cell transformation, and how a related protein, DNA-binding protein-A (DbpA) behaves in comparison. NIH3T3 cells were transduced with lentiviral vectors encoding for myristoylated (constitutive active) Akt1, YB-1, DbpA, or shRNA targeting YB-1 expression. Colony formation assays showed that human YB-1 acts similar to chicken on Akt-dependent cell transformation. This activity was not titratable. Given the correlation of nuclear YB-1 and upregulated DbpA expression in a series of clear cell renal cell carcinomas (n = 40) the colony formation assay was extended to include ectopic DbpA expression. DbpA alone prominently induced cell transformation, which was enhanced when constitutive active Akt1 or concomitant YB-1 expression was present. Notably, co-expression of DbpA together with YB-1 abrogated the repressive effect on Akt1 signaling observed with YB-1 alone. Macroscopically, some colonies yielded a remarkable “invasive” phenotype. Thus, cold shock proteins may convey profound anti- and pro-oncogenic effects on Akt-dependent cell transformation. DbpA is able to overcome the anti-oncogenic effects seen with combined YB-1 and Akt signaling in an in vitro model of colonial growth.

Targeting microenvironment in cancer therapeutics

During development of a novel treatment for cancer patients, the tumor microenvironment and its interaction with the tumor cells must be considered. Aspects such as the extracellular matrix (ECM), the epithelial-mesenchymal transition (EMT), secreted factors, cancer-associated fibroblasts (CAFs), the host immune response, and tumor-associated microphages (TAM) are critical for cancer progression and metastasis. Additionally, signaling pathways such as the nuclear factor κB (NF-κB), transforming growth factor β (TGFβ), and tumor necrosis factor α (TNFα) can promote further cytokine release in the tumor environment, and impact tumor progression greatly. Importantly, cytokine overexpression has been linked to drug resistance in cancers and is therefore an attractive target for combinational therapies. Specific inhibitors of cytokines involved in signaling between tumor cells and the microenvironment have not been studied in depth and have great potential for use in personalized medicines. Together, the interactions between the microenvironment and tumors are critical for tumor growth and promotion and should be taken into serious consideration for future novel therapeutic approaches.

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-β (TGF-β) 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-β activation. Conclusion: Our study demonstrated that YB1 modulated the adhesion ability of renal cell carcinoma cells by regulating ITGB8 and TGF-β.

High YBX1 expression indicates poor prognosis and promotes cell migration and invasion in nasopharyngeal carcinoma

Y-box binding protein-1 (YBX1) is a multifunctional protein and often acts as an indicator of poor prognosis in cancers. Increasing evidence has shown that the levels of YBX1 protein were closely associated with multidrug resistance, relapse, metastasis and poor prognosis in cancers. However, its role in nasopharyngeal carcinoma (NPC) metastasis remains unknown. In our study, we discovered that the expression of YBX1 was increased in nasopharyngeal carcinoma tissues. YBX1 protein levels positively correlated with T stage and metastasis of NPC patients. Moreover, expression of YBX1 was negatively correlated with membrane E-cadherin levels and positively correlated with Vimentin expression. In vitro, the expression of YBX1 was closely related to the invasive and migratory ability of nasopharyngeal carcinoma cells. Knockdown of YBX1 inhibited migration and invasion in 5-8F cells, and over-expression of YBX1 promoted CNE1 cells migration and invasion. Transforming growth factor-β1 (TGF-β1) treatment led to epithelial-to-mesenchymal transition (EMT) in CNE1 cells accompanied by elevated YBX1 expression. On the contrary, knockdown of YBX1 partially inhibited the TGF-β1-induced CNE1 cell migration, together with changes of EMT-associated markers. Our study revealed that TGF-β1/YBX1 signaling might be one of novel mechanisms mediating EMT in NPC, providing a new target for the treatment of nasopharyngeal carcinoma.

Silencing of Y-box binding protein-1 by RNA interference inhibits proliferation, invasion, and metastasis, and enhances sensitivity to cisplatin through NF-κB signaling pathway in human neuroblastoma SH-SY5Y cells

Y-box binding protein-1 (YB-1), a member of Y-box protein family binding DNA and RNA, has been proposed as a novel marker in multiple malignant tumors and found to be associated with tumor malignancy. Neuroblastoma is an embryonal tumor arising from neuroblast cells of the autonomic nervous system, which is the most common cancer diagnosed in infants. It has been reported that YB-1 is highly expressing in various human tumors including nasopharynx, thyroid, lung, breast, colon, ovary, and prostate cancers. This study aimed to investigate the functional role of YB-1 in neuroblastoma by silencing YB-1 using RNA interference (shRNA) in neuroblastoma SH-SY5Y cells. We found that silencing of YB-1 decreased the proliferation, migration, and invasion of SH-SY5Y cells. At molecular level, inhibition of YB-1 decreased the expression level of PCNA as well as MMP-2 in neuroblastoma SH-SY5Y cells. Also, we discovered that YB-1 silencing sensitized SH-SY5Y cells to cisplatin and promoted the apoptosis induced by cisplatin due to down-regulation of multidrug resistance (MDR) 1 protein via NF-κB signaling pathway. Therefore, we consider that targeting YB-1 is promising for neuroblastoma treatment and for overcoming its cisplatin resistance in the development of new neuroblastoma therapeutic strategies.

Novel Serine 176 Phosphorylation of YBX1 Activates NF-κB in Colon Cancer

Y box protein 1 (YBX1) is a well known oncoprotein that has tumor-promoting functions. YBX1 is widely considered to be an attractive therapeutic target in cancer. To develop novel therapeutics to target YBX1, it is of great importance to understand how YBX1 is finely regulated in cancer. Previously, we have shown that YBX1 could function as a tumor promoter through phosphorylation of its Ser-165 residue, leading to the activation of the NF-κB signaling pathway (1). In this study, using mass spectrometry analysis, we discovered a distinct phosphorylation site, Ser-176, on YBX1. Overexpression of the YBX1-S176A (serine-to-alanine) mutant in either HEK293 cells or colon cancer HT29 cells showed dramatically reduced NF-κB-activating ability compared with that of WT-YBX1, confirming that Ser-176 phosphorylation is critical for the activation of NF-κB by YBX1. Importantly, the mutant of Ser-176 and the previously reported Ser-165 sites regulate distinct groups of NF-κB target genes, suggesting the unique and irreplaceable function of each of these two phosphorylated serine residues. Our important findings could provide a novel cancer therapy strategy by blocking either Ser-176 or Ser-165 phosphorylation or both of YBX1 in colon cancer.

Role of post-translational modification of the Y box binding protein 1 in human cancers

Y box binding protein-1 (YBX1) belongs to a DNA- and RNA-binding family of transcription factors, containing the highly conserved cold shock domain (CSD). YBX1 is involved in a number of cellular functions including transcription, translation, DNA damage repair etc., and it is upregulated during times of environmental stress. YBX1 is localized in both the cytoplasm and the nucleus. There, its nuclear translocation is observed in a number of cancers and is associated with poor prognosis and disease progression. Additionally, YBX1 expression is upregulated in a variety of cancers, pointing towards its role as a potential oncogene. Under certain circumstances, YBX1 also promotes the expression of multidrug resistance 1 (MDR1) gene, which is involved in the development of drug resistance. Thus, it is critical to understand the mechanism of YBX1 regulation and its downstream effects on promoting cancer development. A number of recent studies have highlighted the mechanisms of YBX1 regulation. Mass spectrometric analyses have reported several post-translational modifications that possibly play an important role in modulating YBX1 function. Phosphorylation is the most widely occurring post-translational modification in YBX1. In vivo analyses of sites like S102 and more recently, S165 illustrate the relationship of post-translational regulation of YBX1 in promoting cell proliferation and tumor growth. This review provides a comprehensive and up-to-date account of post-translational modifications identified in YBX1. This knowledge is a key in allowing us to better understand the mechanism of YBX1 regulation, which will aid in development of novel therapeutic strategies to target YBX1 in many types of cancer in the future.