Nuclear Y-box Binding Protein-1 Expression Research Articles

Loss of YB-1 alleviates liver fibrosis by suppressing epithelial-mesenchymal transition in hepatic progenitor cells

Previously, we reported that the nuclear translocation of Y-box binding protein 1 (YB-1) is induced by transforming growth factor-β (TGF-β) and promotes hepatic progenitor cells (HPCs) expansion. Here, we explored the mechanisms underlying YB-1 translocation and the impact of YB-1 on the epithelial–mesenchymal transition (EMT) in HPCs. YB-1flox/floxcre+/− (YB-1f/fcre+/−) mice and YB-1f/fcre−/− mice were fed with a 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC) or a choline-deficient, ethionine-supplemented (CDE) diet. Liver injury and fibrosis were assessed by performing hematoxylin and eosin (HE) and Masson staining. The expression of collagen and EMT-related markers (E-cadherin, N-cadherin, and Snail) was detected by reverse transcription-polymerase chain reaction (RT-PCR), western blotting, and immunofluorescence analyses. Protein kinase B (AKT) expression in HPCs was silenced via RNA interference. Nuclear YB-1 expression in HPCs was detected via western blotting and immunofluorescence analyses. HPC proliferation was detected by immunofluorescence. Our results indicate that YB-1 transcriptionally regulated the biological behavior of HPCs. HPC-specific YB-1 knockout alleviated liver fibrosis in mice fed with DDC or CDE diet. YB-1 nuclear translocation promoted matrix metallopeptidase 9 transcription. YB-1 depletion in HPCs significantly dampened the EMT and inhibited AKT phosphorylation in vitro and in vivo. AKT knockdown compromised TGF-β-induced YB-1 nuclear translocation, thereby inhibiting the EMT and HPC proliferation. EMT and AKT were highly activated in HPCs in cirrhotic livers. Collectively, our findings indicate that the loss of YB-1 suppressed EMT in HPCs and alleviated liver fibrosis in mice, and that AKT was essential for TGF-β-induced YB-1 nuclear translocation and HPC proliferation.

DDRE-37. YB-1 AS A BIOMARKER FOR DRUG RESISTANCE AND TUMOUR PROGRESSION IN MEDULLOBLASTOMA

Abstract Medulloblastoma (MB) relapse is the most significant unmet clinical challenge in childhood cancer. Recently it has become evident that MBs display altered biology at relapse, indicative of the emergence and expansion of a minor, therapy resistant cancer cell population. Thus, the examination of mechanisms underlying therapy resistance is of critical importance. Y-box binding protein 1 (YB-1) is a multi-functional oncoprotein whose elevated expression and nuclear accumulation correlate with drug resistance, metastasis and disease progression in numerous cancers, although little is known about the functional role of YB-1 in MB. Genomic analysis of large-scale publicly available patient datasets revealed YB-1 expression is significantly elevated across MB molecular subgroups and high expression correlates with poor overall survival. Immunohistochemical analysis of YB-1 localisation in patient TMAs revealed significant YB-1 nuclear accumulation, suggestive of elevated YB-1 nuclear activity in these patients. Treatment of Group 3 MB cell lines (D283MED and HDMB-03) with cisplatin and subsequent analysis by nuclear/cytoplasmic fractionation and confocal microscopy revealed significantly increased nuclear and overall YB-1 expression, indicating a role for YB-1 in cellular stress response. In support of this, ChIP analysis in D283MED and HDMB-03 cell lines confirmed YB-1 interaction with multi-drug transporter gene ABCB1, while stable YB-1 knockdown resulted in significantly reduced ABCB1 expression. Likewise, knockdown of YB-1 expression in D283MED cells results in increased susceptibility of cells to vincristine, supporting a role for YB-1 in the acquisition of drug resistance in MB cell lines. Finally, whole transcriptome sequencing of YB-1-knockdown HDMB-03 and D283MED cell lines indicated YB-1 regulation of a variety of cell death, survival and metabolic pathways. We are currently using ChIP-Seq analysis to identify targetable YB-1 downstream “hits” which drive these processes. Ultimately, we aim to identify druggable targets of YB-1 allowing us to establish more effective therapeutic options for the treatment of high-risk MB.

AB094. C1QBP negatively regulates the activation of oncoprotein YBX1 in the renal cell carcinoma as revealed by interactomics analysis

BackgroundThe Y-box-binding protein 1 (YBX1) plays a critical role in tumorigenesis by promoting cell proliferation, overriding cell cycle check points, and enhancing genomic instability.MethodsThe interactome of YBX1 in renal cell carcinoma (RCC) was analyzed by coimmunoprecipitation and mass spectrometry. The interaction between C1QBPand YBX1 was confirmed by immunoprecipitation and Western blotting. The clinical significance of these two proteins by IHC.ResultsA total of 129 proteins were identified as potential YBX1 binding partners. Knockdown of C1QBP enhanced the phosphorylation of YBX1 and its nuclear translocation. Expression of YBX1 was markedly elevated. Meanwhile, the level of C1QBP in the carcinoma tissues was significantly lower.ConclusionsThese data suggest that C1QBP is a novel regulator of YBX1, and the expression of C1QBP and the nuclear expression of YBX1 could both be used as independent prognostic makers for cancer progression in the RCC patients.

Nuclear expression of Y-box binding protein-1 is associated with poor prognosis in patients with pancreatic cancer and its knockdown inhibits tumor growth and metastasis in mice tumor models.

The objective of this study was to examine the implication of Y-box-binding protein-1 (YB-1) for the aggressive phenotypes, prognosis and therapeutic target in pancreatic ductal adenocarcinoma (PDAC). YB-1 expression in PDAC, pancreatic intraepithelial neoplasia (PanIN) and normal pancreas specimens was evaluated by immunohistochemistry, and its correlation with clinicopathological features was assessed in patients with PDAC. The effects of YB-1 on proliferation, invasion and expressions of cell cycle-related proteins and matrix metalloproteinases (MMPs) were analyzed by WST-8, cell cycle and Matrigel invasion assays, Western blotting and quantitative RT-PCR in PDAC cells transfected with YB-1-siRNAs. To verify the significance of YB-1 for tumor progression in vivo, the growth and metastasis were monitored after intrasplenic implantation of ex vivo YB-1 siRNA-transfected PDAC cells, and YB-1-targeting antisense oligonucleotides were intravenously administered in nude mice harboring subcutaneous tumor. The intensity of YB-1 expression and positivity of nuclear YB-1 expression were higher in PDAC than PanIN and normal pancreatic tissues. Nuclear YB-1 expression was significantly associated with dedifferentiation, lymphatic/venous invasion and unfavorable prognosis. YB-1 knockdown inhibited cell proliferation via cell cycle arrest by S-phase kinase-associated protein 2 downregulation and consequent p27 accumulation, and decreased the invasion due to downregulated membranous-type 2 MMP expression in PDAC cells. Tumor growth and liver metastasis formation were significantly suppressed in nude mice after implantation of YB-1-silenced PDAC cells, and the YB-1 targeting antisense oligonucleotide significantly inhibited the growth of subcutaneous tumors. In conclusion, YB-1 may be involved in aggressive natures of PDAC and a promising therapeutic target.

唾液腺癌におけるYB-1発現の病理組織学的研究

唾液腺癌におけるYB-1発現の病理組織学的研究

Histopathological Investigation of Nuclear Y-box Binding Protein-1 Expression in Salivary Gland Carcinoma

Histopathological Investigation of Nuclear Y-box Binding Protein-1 Expression in Salivary Gland Carcinoma

Overexpression of YB1 and EZH2 are associated with cancer metastasis and poor prognosis in renal cell carcinomas.

Renal cell carcinoma (RCC) is the most common type of kidney cancers in adults, and metastasis represents the major cause of mortality of RCC patients. The Y-box binding protein 1 (YB1) is a multifunctional oncoprotein in various malignancies. Enhancer of zeste homolog 2 (EZH2), a polycomb histone methyltransferase, is a key epigenetic modifier implicated in various cancer metastasis. However, the expression patterns and clinical correlations of both YB1 and EZH2 in RCC remain largely unclear. In this study, the expression of YB1 and EZH2 were examined using immunohistochemistry staining in a study cohort including 165 RCC and 80 tumor adjacent normal tissues. RCC tissues showed a significant higher nuclear expression of YB1 (p < 0.001) and EZH2 (p < 0.001) as compared with the normal counterparts. In addition, YB1 and EZH2 nuclear overexpression were found to be positively associated with RCC stage (p < 0.001 and p = 0.005), Fuhrman tumor grade (p = 0.022 and p = 0.044), and metastasis (p < 0.001 and p = 0.009). Overall survival analysis indicated patients with YB1 (p = 0.004, HR 5.656 (2.006-10.944)) and/or EZH2 (p = 0.006, HR 4.551 (2.124-9.438)) nuclear overexpression correlated with poor survival. More interestingly, YB1 and EZH2 nuclear expression was correlated (p = 0.005). Further studies demonstrated that EZH2 expression was significantly downregulated in YB1 knockdown RCC cell lines. Functionally, YB1 knockdown inhibited RCC invasion in vitro. In conclusion, YB1 and EZH2 expression was correlated and associated with RCC incidence, tumor stage, grade, metastasis, and survival.

GOLPH3 and YB-1 Are Novel Markers Correlating With Poor Prognosis in Prostate Cancer

BackgroundProstate cancer is a common and aggressive cancer among men. Despite advances in the treatment, the mechanisms involved in progression are still unclear. New prognostic markers should be explored for better design of patient-specific therapeutic regimens.MethodsThis study was performed on 120 patients stratified as 76 with prostatic carcinoma, 12 with low-grade prostate intraepithelial lesion, 12 with high-grade prostate intraepithelial lesion and 20 with benign prostate hyperplasia. Immunohistochemical study was done for Golgi phosphoprotein 3 (GOLPH3) and Y-box binding protein-1 (YB-1) analysis. Correlation with clinicopathological data and overall survival was analyzed.ResultsBoth GOLPH3 and YB-1 showed increased expression from benign to malignant tumors. In prostatic carcinoma, cytoplasmic GOLPH3 was associated with Gleason score, stage and androgen receptor (P = 0.034, P < 0.001, and P = 0.008 respectively). Nuclear YB-1 expression was associated with Gleason score and androgen receptor (P = 0.018 and P = 0.024 respectively). Cytoplasmic YB-1 expression was associated with Gleason score, stage and androgen receptor (P = 0.008, P = 0.027, and P < 0.001 respectively). High Gleason score (P = 0.004), high stage (P < 0.001) and androgen receptor (P = 0.006) were the only detected adverse prognostic clinicopathological factors. Moderate/intense GOLPH3 and high nuclear and cytoplasmic YB-1 expression were correlated with shorter overall survival (P < 0.001, P = 0.020, and P < 0.001 respectively). In the multivariate analysis, moderate/intense GOLPH3 expression was the only predictor of overall survival (P = 0.025).ConclusionsHigh GOLPH3 and nuclear/cytoplasmic YB-1 expression correlated with poor prognosis in prostate cancer. Both markers can be promising targets for new treatment strategies.

C1QBP negatively regulates the activation of oncoprotein YBX1 in the renal cell carcinoma as revealed by interactomics analysis.

The Y-box-binding protein 1 (YBX1) plays a critical role in tumorigenesis by promoting cell proliferation, overriding cell-cycle check points, and enhancing genomic instability. In this study, the interactome of YBX1 in renal cell carcinoma (RCC) was analyzed by coimmunoprecipitation and mass spectrometry to better understand its function and regulatory mechanism. A total of 129 proteins were identified as potential YBX1 binding partners. The interaction between the complement component 1, q subcomponent binding protein (C1QBP), and YBX1 was further confirmed by immunoprecipitation and Western blotting. Knockdown of C1QBP enhanced the phosphorylation of YBX1and its nuclear translocation, indicating that C1QBP negatively regulated YBX1 activation. The clinical significance of these two proteins was analyzed in the tissues from 52 RCC patients by immunohistochemistry. Expression of YBX1 was markedly elevated in the carcinoma tissues, and its nuclear expression was associated with histological T stage and metastasis. Meanwhile, the level of C1QBP in the carcinoma tissues was significantly lower than that in the adjacent healthy tissues, which was negatively correlated with the nuclear localization of YBX1 in the RCC tissues (P = 0.011). These data suggest that C1QBP is a novel regulator of YBX1, and the expression of C1QBP and the nuclear expression of YBX1 could both be used as independent prognostic makers for cancer progression in the RCC patients. The proteomics data have been deposited to the ProteomeXchange with identifier PXD001493.

Y-box Binding Protein-1 Contributes to Both HER2/ErbB2 Expression and Lapatinib Sensitivity in Human Gastric Cancer Cells

Gene amplification of HER2/ErbB2 occurs in gastric cancer and the therapeutic efficacy of the HER2-targeted antibody, trastuzumab, has recently been improved against HER2-positive advanced stomach cancer. Here, we examined whether Y-box-binding protein-1 (YB-1) could selectively control HER2 gene expression and cellular sensitivity to EGF receptor (EGFR) family protein-targeted drugs in human gastric cancer cells. HER2 expression was specifically downregulated by YB-1 silencing using its cognate siRNA, whereas there was less change in the expression of EGFR and HER3. A chromatin immunoprecipitation assay revealed the specific binding of YB-1 to its consensus sequence on the 5'-regulatory region of HER2. YB-1 knockdown induced drug resistance to lapatinib, a dual EGFR and HER2 kinase inhibitor, and also to erlotinib, an EGFR kinase inhibitor. Moreover, phosphorylation of protein kinase B (Akt) was not markedly affected by lapatinib or erlotinib when YB-1 was silenced. Nuclear YB-1 expression was significantly (P = 0.026) associated with HER2 expression, but not with EGFR or HER3, in patients with gastric cancer (n = 111). The YB-1-HER2 axis may therefore be useful for the further development of personalized therapeutics against gastric cancer by HER2-targeted drugs.

Y-box binding protein-1 regulates cell proliferation and is associated with clinical outcomes of osteosarcoma

Background:Prognosis of osteosarcoma (OS) with distant metastasis and local recurrence is still poor. Y-box binding protein-1 (YB-1) is a multifunctional protein that can act as a regulator of transcription and translation and its high expression of YB-1 protein was observed in OS, however, the role of YB-1 in OS remains unclear.Methods:Y-box binding protein-1 expression in OS cells was inhibited by specific small interfering RNAs to YB-1 (si-YB-1). The effects of si-YB-1 in cell proliferation and cell cycle transition in OS cells were analysed in vitro and in vivo. The association of nuclear expression of YB-1 and clinical prognosis was also investigated by immunohistochemistry.Results:Proliferation of OS cell was suppressed by si-YB-1 in vivo and in vitro. The expression of cyclin D1 and cyclin A were also decreased by si-YB-1. In addition, si-YB-1 induced G1/S arrest with decreased cyclin D1 and cyclin A in OS cell lines. Direct binding of YB-1 in OS cell lines was also observed. Finally, the nuclear expression of YB-1 was significantly related to the poorer overall survival in OS patients.Conclusion:Y-box binding protein-1 would regulate cell cycle progression at G1/S and tumour growth in human OS cells in vitro and in vivo. Nuclear expression of YB-1 was closely associated with the prognosis of OS, thus, YB-1 simultaneously could be a potent molecular target and prognostic biomarker for OS.

Nuclear Y-box binding protein-1 expression as a prognostic marker and correlation with epidermal growth factor receptor expression in cervical cancer.

5085 Background: Y-box binding protein-1 (YB-1) is a member of the cold shock protein family and functions in transcription and translation. Many reports indicate that YB-1 is highly expressed in tumor cells and is a marker of tumor aggressiveness and clinical prognosis. Overexpression of epidermal growth factor receptor (EGFR) has been associated with poor outcomes in cervical cancer (CC). Clinical trials have shown that EGFR inhibitors are effective against CC (JCO 2011). Nuclear YB-1 expression correlates with EGFR expression in various types of cancer. Methods: Nuclear YB-1 expression was immunohistochemically analyzed in tissue specimens obtained from 204 CC patients who underwent surgery. Associations of nuclear YB-1 expression with clinicopathological factors such as survival and EGFR (HER1 and HER2) expression were investigated. Results: Nuclear YB-1 expression was observed in 41 (20%) of 204 cases and correlated with stage, tumor diameter, stromal invasion, and lymph-node metastasis. Nuclear YB-1 expression also correlated with both HER1 expression (p=0.0114) and HER2 expression (p=0.0053). Kaplan-Meier survival analysis showed that nuclear YB-1 expression was significantly associated with poor outcomes in terms of progression-free survival (p=0.0033) and overall survival (p=0.0003). On multivariate analysis, stromal invasion, parametrial invasion, and nuclear YB-1 expression were independent predictors of survival. Conclusions: Nuclear YB-1 expression is a prognostic marker and correlates with EGFR expression in CC.

Expression of Y-Box-binding protein 1 in Chinese patients with breast cancer

The purpose of this study was to investigate the expression of Y-Box-binding protein 1 (YB-1) in breast cancer and its correlation with clinicopathological characteristics and prognosis. Paraffin sections were retrospectively collected from 239 cases of stage I-III breast cancer patients and 30 healthy females who received surgery between January 2000 and December 2004 in the Chinese People's Liberation Army General Hospital. The protein expression of YB-1 was detected by immunohistochemistry. The expression difference between the two groups and the correlation between YB-1 expression and clinicopathological characteristics and breast cancer prognosis were analyzed. Within the breast cancer group, YB-1 was expressed in the cytoplasm in 100.0% (239/239) of cases and in the nucleus in 36.8% (88/239) of cases. Within the control group of normal breast tissue, YB-1 was expressed in the cytoplasm in 100.0% (30/30) of cases and in the nucleus in 16.7% (5/30) of cases. The expression of YB-1 in the nucleus of breast cancer cells was significantly higher than that in normal breast tissue (P = 0.029). The expression of YB-1 in the nucleus of breast cancer cells positively correlated with the Scarff-Bloom-Richardson grade (P = 0.007) and HER-2 expression (P = 0.005), negatively correlated with ER expression (P = 0.004), and was independent of the age, menstrual status, pathological type, tumor size, lymph node status, presence of thrombosis, PR expression, and EGFR expression. The 5-year disease-free survival (DFS) and overall survival (OS) of patients with positive YB-1 expression in the nucleus were significantly lower than those of patients who were negative for nuclear YB-1 expression, and the difference was statistically significant (DFS 65.9% vs. 82.1%, P = 0.000; OS 79.5% vs. 92.1%, P = 0.000). Multivariate analysis suggested that the expression of YB-1 in the nucleus is an independent prognostic factor that affects DFS and OS in breast cancer patients (DFS P = 0.015; OS P = 0.035). In conclusion, the expression of YB-1 in the nucleus is related to carcinogenesis and the development of breast cancer. Therefore, YB-1 is an important molecular marker that can be used to predict breast cancer prognosis.

8042 POSTER Nuclear Y-box Binding Protein-1 Expression, a Predictive Marker of Prognosis, Is Correlated With Activated Signal Transducer and Activator of Transcription-3 Expression and Survival in Cervical Squamous-cell Carcinoma

8042 POSTER Nuclear Y-box Binding Protein-1 Expression, a Predictive Marker of Prognosis, Is Correlated With Activated Signal Transducer and Activator of Transcription-3 Expression and Survival in Cervical Squamous-cell Carcinoma

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.

The close correlation between 8-hydroxy-2′-deoxyguanosine and epidermal growth factor receptor activating mutation in non–small cell lung cancer

Patients with non-small cell lung cancer harboring mutations in the epidermal growth factor receptor gene, including delE746-A750 and L858R, are highly sensitive to therapy with epidermal growth factor receptor-targeting drugs, such as gefitinib and erlotinib, in comparison with those harboring wild-type epidermal growth factor receptor. It remains unclear how such epidermal growth factor receptor mutations are induced. In this study, we examined whether 8-hydroxy-2'-deoxyguanosine, a representative oxygen nucleotide of DNA, could play a role in activating mutations of the epidermal growth factor receptor gene and also whether Y-box binding protein-1 and 8-oxoguanine DNA glycosylase that are involved in repair of oxidative stimuli-induced DNA damages could play any role in epidermal growth factor receptor activating mutations. Immunohistochemistry was used to evaluate the expression of 8-hydroxy-2'-deoxyguanosine, Y-box binding protein-1, and 8-oxoguanine DNA glycosylase in patients with non-small cell lung cancer (N = 170). We analyzed mutations of delE746-A750 and L858R in the epidermal growth factor receptor gene using peptide nucleic acid-locked nucleic acid polymerase chain reaction clamping. In non-small cell lung cancer patients, nuclear 8-hydroxy-2'-deoxyguanosine expression was strongly associated with these epidermal growth factor receptor mutations. Furthermore, nuclear expression of Y-box binding protein-1 was inversely associated with epidermal growth factor receptor mutations; but nuclear expression of 8-oxoguanine DNA glycosylase was not. Among 51 patients who were treated with gefitinib, progression-free survival was substantially better when 8-hydroxy-2'-deoxyguanosine expression was positive, when epidermal growth factor receptor mutations were present, and when nuclear Y-box binding protein-1 expression was negative. Thus, activating mutations of the epidermal growth factor receptor gene in non-small cell lung cancer were closely associated with a decrease in the damage repair process for 8-hydroxy-2'-deoxyguanosine in oxidized DNA.

Y-box binding protein-1 (YB-1) promotes cell cycle progression through CDC6-dependent pathway in human cancer cells

Y-box binding protein-1 (YB-1) plays pivotal roles in acquisition of global drug resistance and cell growth promotion through transcriptional activation of genes for both drug resistance and growth factor receptors. In this study, we investigated whether YB-1 is involved in regulation of the cell cycle and cell proliferation of human cancer cells. Treatment with YB-1 siRNA caused a marked suppression of cell proliferation and expression of a cell cycle related gene, CDC6 by cancer cells. Of cell cycle of cancer cells, S phase content was specifically reduced by knockdown of YB-1. The overexpression of CDC6 abrogated this inhibition of both cell proliferation and S phase entry. ChIP assay demonstrated that YB-1 binds to a Y-box located in the promoter region of the CDC6 gene. Expression of cyclin D1, CDK1 and CDK2 was also reduced with increased expression of p21 Cip1 and p16 INK4A when treated with YB-1 siRNA. Furthermore, the nuclear YB-1 expression was significantly associated with the level of CDC6 nuclear expression in patients with breast cancer. In conclusion, YB-1 plays an important role in cell cycle progression at G1/S of human cancer cells. YB-1 thus could be a potent biomarker for tumour growth and cell cycle in its close association with CDC6.

Nuclear expression of YB‐1 in diffuse large B‐cell lymphoma: correlation with disease activity and patient outcome

The aim of this study is to investigate the correlations among Y-box binding protein-1 (YB-1) and P-glycoprotein(P-gp) and their prognostic significance in diffuse large B-cell lymphoma (DLBCL). The expression of YB-1 and P-gp was examined immunohistochemically on 68 patients with DLBCL who were treated from 2003 to 2005. Samples were paraffin-embedded newly diagnosed DLBCL tissues taken from the surgical specimens before adjuvant chemotherapy. We determined the prognostic significance of YB-1 and its relationship with P-gp in patients with DLBCL. Of the 68 tumors examined, 42 (61.8%) were positive for YB-1 expression in the nucleus. The nuclear expression of YB-1 was significantly associated with clinical stages, bone marrow involvement, extra nodal involvement, and poor response to chemotherapy. No associations were observed between P-gp and clinical features, in context of the poor response to chemotherapy. Nuclear expression of YB-1 was correlated significantly with increased expression of P-gp patients with a nuclear YB-1 tumor had a poorer prognosis than did those with a cytoplasmic YB-1 tumor in all of the DLBCL patients (P = 0.035). Thus, correlation of YB-1 and P-gp emerged as a possible biomarker for unfavorable prognosis in DLBCL. It may provide useful information for clinicians to determine the appropriate therapy for each type of DLBCL.

Nuclear Y-Box Binding Protein-1, a Predictive Marker of Prognosis, Is Correlated with Expression of HER2/ErbB2 and HER3/ErbB3 in Non-small Cell Lung Cancer

Nuclear expression of Y-box binding protein-1 (YB-1) is closely associated not only with global drug resistance and expression of several growth factor receptors in various human malignancies but also with overall patient survival. The effect of YB-1 knockdown on expression of epidermal growth factor receptor (EGFR) family proteins was examined by Western blot using human lung cancer cell lines. Immunohistochemistry was used to evaluate the expression of nuclear YB-1 and EGFR family proteins in patients with non-small cell lung cancer (NSCLC) (n = 104). In the five NSCLC cell lines, expressions of EGFR, human epidermal growth factor receptor 2 (HER2), HER3, and hepatocyte growth factor receptor (c-Met) in PC-9 cells; of HER2 and c-Met in EBC-1 cells; and of HER3 in QG56 cells were down-regulated by YB-1 knockdown. By immunohistochemical analysis, we observed that HER3 expression was significantly negatively correlated with nuclear YB-1 expression in squamous cell carcinoma (p = 0.038). HER2 expression was positively correlated with nuclear YB-1 expression in adenocarcinoma (p = 0.052). Nuclear expression of YB-1 correlated with overall survival of all patients (p = 0.028) and of patients with adenocarcinoma (p = 0.007). Furthermore, there was a significant difference in therapeutic efficacies of gefitinib between patients with nuclear YB-1 expression and those with non-nuclear YB-1 expression in patients with NSCLC (p = 0.004, n = 26) but not between those with high and those with low expression of EGFR, HER2, HER3, and c-Met. Nuclear YB-1 expression might be essential for the malignant phenotype in lung cancer patients and might be an important biomarker for the development of therapeutic strategy against NSCLC.

Programmed Cell Death Protein 4 Down-regulates Y-Box Binding Protein-1 Expression via a Direct Interaction with Twist1 to Suppress Cancer Cell Growth

Programmed cell death protein 4 (PDCD4) has recently been shown to be involved in both transcription and translation, and to regulate cell growth. However, the mechanisms underlying PDCD4 function are not well understood. In this study, we show that PDCD4 interacts directly with the transcription factor Twist1 and leads to reduced cell growth through the down-regulation of the Twist1 target gene Y-box binding protein-1 (YB-1). PDCD4 interacts with the DNA binding domain of Twist1, inhibiting its DNA binding ability and YB-1 expression. Immunohistochemical analysis showed that an inverse correlation between nuclear PDCD4 and YB-1 expression levels was observed in 37 clinical prostate cancer specimens. Growth suppression by PDCD4 expression was completely recovered by either Twist1 or YB-1 expression. Moreover, PDCD4-overexpressing cells are sensitive to cisplatin and paclitaxel but not to etoposide or 5-fluorouracil. In summary, PDCD4 negatively regulates YB-1 expression via its interaction with Twist1 and is involved in cancer cell growth and chemoresistance.