Regulation of MDR1 gene expression in multidrug-resistant cancer cells is independent from YB-1

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.

Association between ABCB1 (3435C>T) polymorphism and susceptibility of colorectal cancer: A meta-analysis

Studies on the relationship between ABCB1 3435C>T polymorphism (rs1045642) and colorectal cancer (CRC)susceptibility have yielded inconclusive results. To clarify this issue, we undertook a meta-analysis to investigate the relationship between rs1045642 and CRC risk.Three electronic scientific publication databases (Cochrane Library, Pubmed, Embase) were screened using specific search terms. Relevant literature was identified using literature traceability methods. Selected publications were evaluated according to the inclusion and exclusion criteria. Effect size information (odds ratio and the corresponding 95% confidence interval [CI]) was obtained following quality assessment and data extraction from the included publications, and a meta-analysis conducted. Statistical analysis was performed with the Stata sofz (Version 13.0) software.Overall, 17 case-control studies involving 7129 CRC patients and 7710 healthy control subjects satisfied the criteria for inclusion in the meta-analysis. There was no significant association between ABCB1 3435C>T polymorphism and CRC risk in any of the genetic models. In the CC versus CT model (I = 20.9%, Pheterogeneity = .276), CC versus CT + TT model (I = 45.6%, Pheterogeneity = .102) and CT versus CC + TT model (I = 17.8%, Pheterogeneity = .298) analyses, between-study heterogeneities were detected as significant in Asian populations. In the CT versus TT model (I = 24%, Pheterogeneity = .254) and CC + CT versus TT model (I = 0, Pheterogeneity = .55), between-study heterogeneities were found to be significant in groups of different populations.The meta-analysis described here suggests that the ABCB1 3435C>T polymorphism is not related to CRC susceptibility.

Sesquiterpene lactone 6-O-angeloylplenolin reverses vincristine resistance by inhibiting YB-1 nuclear translocation in colon carcinoma cells

Multidrug resistance (MDR) is a major obstacle to cancer chemotherapy efficacy. In the present study, 6-O-angeloylplenolin repressed the overexpression of ATP binding cassette subfamily B member 1 (MDR1) and increasing the intracellular concentration of anticancer drugs. A reduction in P-glycoprotein expression (encoded by MDR1) was observed in parallel with a decline in mRNA expression in vincristine-resistant HCT (HCT-8/VCR) cells treated with 6-O-angeloylplenolin. In addition, 6-O-angeloylplenolin suppressed the activity of the MDR1 gene promoter. Treatment with 6-O-angeloylplenolin also decreased the amount of the specific protein complex that interacted with the MDR1 gene promoter in HCT-8/VCR cells, potentially leading to the suppression of MDR1 expression. Treatment with 6-O-angeloylplenolin inhibited the nuclear translocation of Y-box binding protein-1 in HCT-8/VCR cells treated with 6-O-angeloylplenolin, contributing to the negative regulation of MDR1. Finally, 6-O-angeloylplenolin reversed VCR resistance in an HCT/VCR xenograft model. In conclusion, 6-O-angeloylplenolin exhibited a MDR-reversing effect by downregulating MDR1 expression and could represent a novel adjuvant agent for chemotherapy.

YBX1 at the crossroads of non-coding transcriptome, exosomal, and cytoplasmic granular signaling

YBX1 (Y box binding protein 1) is an RNA-/DNA-binding multifunctional protein harboring the classical cold shock protein (CSD) domain, an A/P domain, and a long C-terminal domain with alternating positively and negatively charged amino acids. It is a well-established oncogenic transcriptional factor, and regulates apoptosis, translation, cell proliferation, mRNA splicing, repair, differentiation, and stress response. The non-coding transcriptome has added yet another layer of complexity to the YBX1-mediated master regulation of cellular functions. Interestingly, YBX1 has been shown to localize to cytoplasmic granules such as P granules and stress granules. These granules regulate the non-coding transcriptome profile as well as mRNA translation and degradation. In this review, we discuss the recent findings on YBX1 signaling as mediated by various classes of non-coding RNAs, and on the functions of YBX1 at P granules, stress granules, exosomes, and mitochondria. YBX1 is a well-established target for cancer therapy and understanding its functions at organelles and ncRNA transcriptomes will shed new insights for devising organelle based anti-cancer therapies.

A novel EGR-1 dependent mechanism for YB-1 modulation of paclitaxel response in a triple negative breast cancer cell line

Chemotherapy with taxanes such as paclitaxel (PTX) is a key component of triple negative breast cancer (TNBC) treatment. PTX is used in combination with other drugs in both the adjuvant setting and in advanced breast cancer. Because a proportion of patients respond poorly to PTX or relapse after its use, a greater understanding of the mechanisms conferring resistance to PTX is required. One protein shown to be involved in drug resistance is Y-box binding protein 1 (YB-1). High levels of YB-1 have previously been associated with resistance to PTX in TNBCs. In this study, we aimed to determine mechanisms by which YB-1 confers PTX resistance. We generated isogenic TNBC cell lines that differed by YB-1 levels and treated these with PTX. Using microarray analysis, we identified EGR1 as a potential target of YB-1. We found that low EGR1 mRNA levels are associated with poor breast cancer patient prognosis, and that EGR1 and YBX1 mRNA expression was inversely correlated in a TNBC line and in a proportion of TNBC tumours. Reducing the levels of EGR1 caused TNBC cells to become more resistant to PTX. Given that PTX targets cycling cells, we propose a model whereby high YB-1 levels in some TNBC cells can lead to reduced levels of EGR1, which in turn promotes slow cell cycling and resistance to PTX. Therefore YB-1 and EGR1 levels are biologically linked and may provide a biomarker for TNBC response to PTX.

Inducible RNAi system and its application in novel therapeutics

RNA interference (RNAi) was discovered as a cellular defense mechanism more than decade ago. It has been exploited as a powerful tool for genetic manipulation. Characterized with specifically silencing target gene expression, it has great potential application for disease treatment. Currently, there are human clinical trials in progress or planned. Despite the excitement regarding this prominent technology, there are many obstacles and concerns that prevent RNAi from being widely used in the therapeutic field. Among them, the non-spatial and non-temporal control is the most difficult challenge, as well as off-target effects and triggering type I immune responses. Inducible RNAi technology can effectively regulate target genes by inducer-mediated small hairpin RNA expression. Combination with inducible regulation systems this makes RNAi technology more sophisticated and may provide a wider application field. This review discusses approaches of inducible RNAi systems, the potential problem areas and solutions and their therapeutic applications. Given the limitations discussed herein being resolved, we believe that inducible RNAi will be a major therapeutic modality within the next several years.

Y-box binding protein 1--a prognostic marker and target in tumour therapy

Y-box binding protein 1 (YB-1) is a multifunctional protein involved in various cellular processes including both transcriptional and translational regulation of target gene expression. Significantly increased YB-1 levels have been reported in a number of human malignancies and shown to be associated with poor prognosis and disease recurrence. Indeed, YB-1 can act as a versatile oncoprotein playing an important role in tumour cell proliferation and progression. Consequently, YB-1 not only proves to be a good prognostic tumour marker, but also may be a promising emerging molecular target for the development of new therapeutical strategies. In this review, we discuss both the role of YB-1 in cancer and specifically in malignant melanoma as well as possible translations into the clinics derived thereof.

YB-1 protein: functions and regulation

The Y-box binding protein 1 (YB-1, YBX1) is a member of the family of DNA- and RNA-binding proteins with an evolutionarily ancient and conserved cold shock domain. It falls into a group of intrinsically disordered proteins that do not follow the classical rule 'one protein-one function' but introduce a novel principle stating that a disordered structure suggests many functions. YB-1 participates in a wide variety of DNA/RNA-dependent events, including DNA reparation, pre-mRNA transcription and splicing, mRNA packaging, and regulation of mRNA stability and translation. At the cell level, the multiple activities of YB-1 are manifested as its involvement in cell proliferation and differentiation, stress response, and malignant cell transformation. WIREs RNA 2014, 5:95-110. doi: 10.1002/wrna.1200 CONFLICT OF INTEREST: The authors have declared no conflicts of interest for this article. For further resources related to this article, please visit the WIREs website.

The proteolytic YB-1 fragment interacts with DNA repair machinery and enhances survival during DNA damaging stress

The Y-box binding protein 1 (YB-1) is a DNA/RNA-binding nucleocytoplasmic shuttling protein whose regulatory effect on many DNA and RNA-dependent events is determined by its localization in the cell. We have shown previously that YB-1 is cleaved by 20S proteasome between E219 and G220, and the truncated N-terminal YB-1 fragment accumulates in the nuclei of cells treated with DNA damaging drugs. We proposed that appearance of truncated YB-1 in the nucleus may predict multiple drug resistance. Here, we compared functional activities of the full-length and truncated YB-1 proteins and showed that the truncated form was more efficient in protecting cells against doxorubicin treatment. Both forms of YB-1 induced changes in expression of various genes without affecting those responsible for drug resistance. Interestingly, although YB-1 cleavage did not significantly affect its DNA binding properties, truncated YB-1 was detected in complexes with Mre11 and Rad50 under genotoxic stress conditions. We conclude that both full-length and truncated YB-1 are capable of protecting cells against DNA damaging agents, and the truncated form may have an additional function in DNA repair.

Targeting the Y/CCAAT box in cancer: YB-1 (YBX1) or NF-Y?

The Y box is an important sequence motif found in promoters and enhancers containing a CCAAT box - one of the few elements enriched in promoters of large sets of genes overexpressed in cancer. The search for the transcription factor(s) acting on it led to the biochemical purification of the nuclear factor Y (NF-Y) heterotrimer, and to the cloning - through the screening of expression libraries - of Y box-binding protein 1 (YB-1), an oncogene, overexpressed in aggressive tumors and associated with drug resistance. These two factors have been associated with Y/CCAAT-dependent activation of numerous growth-related genes, notably multidrug resistance protein 1. We review two decades of data indicating that NF-Y ultimately acts on Y/CCAAT in cancer cells, a notion recently confirmed by genome-wide data. Other features of YB-1, such as post-transcriptional control of mRNA biology, render it important in cancer biology.

Signal transduction pathways and transcriptional mechanisms of ABCB1/Pgp-mediated multiple drug resistance in human cancer cells

Multiple drug resistance (MDR), defined as the ability of tumour cells to survive exposure to many chemotherapeutic agents, is a major cause of treatment failure in human cancers. The membrane transporter P-glycoprotein (Pgp, encoded by the ABCB1 [adenosine triphosphate-binding cassette, subfamily B, member 1] gene) is the main mechanism for decreased intracellular drug accumulation in human MDR cancer. ABCB1/Pgp-mediated MDR involves several signal transduction pathways and transcription factors. Activation of these signal transduction pathways influences the prognosis of MDR human cancer. Signalling pathways involved in ABCB1/Pgp-mediated MDR include the mitogen-activated protein kinase (MAPK), c-Jun NH(2)-terminal kinase (JNK), p38, cyclic adenosine monophosphate-dependent protein kinase, phosphatidylino sitol 3-kinase and protein kinase C signalling pathways. This review summarizes the biological characteristics, target points and signalling cascade mediators of these pathways. Drugs targeted against these pathways may provide new therapies for treatment of ABCB1/Pgp-mediated MDR.

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.

Reversal effect of Raf-1/Mdr-1 siRNAs co-transfection on multidrug resistance in KBv200 cell line

Multidrug resistance (MDR) is a major barrier for chemotherapy of many cancers. Mdr-1 plays a key role in the development of MDR as extensively verified. However, the role of Raf-1 overexpression in the development of multidrug resistance in human squamous carcinoma (KBv200) cells remains largely unknown. The aim of this study was to investigate the correlation of Raf-1 overexpression with the development of multidrug resistance in KBv200 cells. Furthermore, we explored the reversal effect of Raf-1 siRNA transfection and Raf-1/Mdr-1 siRNAs co-transfection on the multidrug resistance of KBv200 cells and potential mechanism of reversing the multidrug resistance. MTT and flow cytometry assay were used to investigate the reversal effect of single transfection with either Raf-1 or Mdr-1 siRNA and double transfection with Raf-1/Mdr-1 siRNAs to vincristine of KBv200 cells. RT-PCR, immunofluorescence and Western Blot were used to detect mRNA and protein expression of Raf-1 and multidrug-resistant gene Mdr-1. The results of gene detection showed that the expression levels of both Raf-1 and Mdr-1 were greatly decreased upon Raf-1 silencing alone or in combination with Mdr-1 silencing. Raf-1 or Mdr-1 siRNA single transfection could reverse the multidrug resistance of KBv200 cells effectively. Compared with single transfection, Raf-1/Mdr-1 siRNAs co-transfection can significantly reduce IC(50) values and increase the apoptotic rates of KBv200 cells. The above results suggested that Raf-1 gene may be a novel target for reversing the multidrug resistance of human squamous carcinoma cells. Raf-1/Mdr-1 siRNAs co-transfection might be a promising approach to abrogate the multidrug resistance of cancer cells. The potential mechanism may be via inhibiting the multidrug-resistant gene Mdr-1 expression efficiently.

Therapeutic potential of RNA interference in drug-resistant cancers

Resistance including multidrug resistance to chemotherapy is a common clinical problem in patients suffering from cancer. Multidrug resistance is often mediated by overexpression of transmembrane xenobiotic transport molecules belonging to the superfamily of ATP-binding cassette (ABC)-transporters. Inhibition of ABC-transporters by low-molecular weight compounds in cancer patients has been extensively investigated in clinical trials, but the results have been disappointing. Thus, alternative experimental therapeutic strategies for overcoming multidrug resistance are under investigation. These include the application of RNA interference (RNAi) technology. Various RNAi strategies were applied to reverse multidrug resistance in different tumor models in vitro and in vivo. Results and conclusions of these RNAi studies as well as their potential impact for the development of potential RNAi therapeutics will be discussed.

[YB-1 as a potential target in cancer therapy]

The 42-kDa multifunctional cellular protein Y-box protein 1 (YB-1) is expressed in various cancers. It is localized in the cytoplasm as well as in the nucleus. In particular, YB-1 is localized in the nuclear compartment following cellular stress, such as radiation, drug treatment, hyperthermia, or viral infection. Within the nucleus, YB-1 can act as a transcription factor, and it is involved in the regulation of important cancer-associated genes. For example, YB-1 triggers the expression of Her-2 and estrogen receptor alpha (ERalpha) in breast cancer. Thus, nuclear YB-1 appears to be a potential target for the inhibition of Her-2- and ERalpha-dependent proliferation signals, particularly with regard to resistance to Her-2-targeting drugs such as trastuzumab. In some cancers, YB-1 may be involved in regulating MDR1/P-glycoprotein, mediating classical multidrug resistance (MDR). Furthermore, YB-1 is involved in the replication of adenovirus type 5, a commonly used vector in gene therapy. Thus, YB-1 can trigger an "oncolytic" effect in YB-1 nuclear positive cancer cells treated with adenoviruses. Besides its impact as a prognostic factor, in the future the diagnostics of cellular YB-1 status may provide the basis for a virotherapy or a gene therapy incorporating adenoviruses.

Impact of radiation therapy on the oncolytic adenovirus dl520: implications on the treatment of glioblastoma

BACKGROUND AND PURPOSE

Viral oncolytic therapy is emerging as a new form of anticancer therapy and has shown promising preclinical results, especially in combination with radio- and chemotherapy. We recently reported that nuclear localization of the human transcription factor YB-1 in multidrug-resistant cells facilitates E1-independent adenoviral replication. The aim of this study was to evaluate the combined treatment of the conditionally-replicating adenovirus dl520 and radiotherapy in glioma cell lines in vitro and in human tumor xenografts. Furthermore, the dependency of YB-1 on dl520 replication was verified by shRNA directed down regulation of YB-1.

METHODS AND MATERIAL

Localization of YB-1 was determined by immunostaining. Glioma cell lines LN-18, U373 and U87 were infected with dl520. Induction of cytopathic effect (CPE), viral replication, viral yield and viral release were determined after viral infection, radiation therapy and the combination of both treatment modalities. The capacity of treatments alone or combined to induce tumor growth inhibition of subcutaneous U373 tumors was tested also in nude mice.

RESULTS

Quantitative real-time PCR demonstrated that the shRNA-mediated down regulation of YB-1 is leading to a dramatic decrease in adenoviral replication of dl520. Immunostaining analysis showed that the YB-1 protein was predominantly located in the cytoplasm in the perinuclear space and less abundant in the nucleus. After irradiation we found an increase of nuclear YB-1. The addition of radiotherapy increased the oncolytic effect of dl520 with enhanced viral replication, viral yield and viral release. The oncolytic activity of dl520 plus radiation inhibited the growth of subcutaneous U373 tumors in a xenograft mouse model.

CONCLUSIONS

Radiation mediated increase of nuclear YB-1 in glioma cells enhanced the oncolytic potential of adenovirus dl520.