Transducin (β)-like 1 X-linked receptor 1 promotes proliferation and tumorigenicity in human breast cancer via activation of beta-catenin signaling

Two decades of a protooncogene TBL1XR1: from a transcription modulator to cancer therapeutic target

Transducin beta-like 1X-related protein 1 (TBL1XR1) was discovered two decades ago and was implicated as part of the nuclear transcription corepressor complex. Over the past 20 years, the emerging oncogenic function of TBL1XR1 in cancer development has been discovered. Recent studies have highlighted that the genetic aberrations of TBL1XR1 in cancers, especially in hematologic tumors, are closely associated with tumorigenesis. In solid tumors, TBL1XR1 is proposed to be a promising prognostic biomarker due to the correlation between abnormal expression and clinicopathological parameters. Post-transcriptional and post-translational modification are responsible for the expression and function of TBL1XR1 in cancer. TBL1XR1 exerts its functional role in various processes that involves cell cycle and apoptosis, cell proliferation, resistance to chemotherapy and radiotherapy, cell migration and invasion, stemness and angiogenesis. Multitude of cancer-related signaling cascades like Wnt-β-catenin, PI3K/AKT, ERK, VEGF, NF-κB, STAT3 and gonadal hormone signaling pathways are tightly modulated by TBL1XR1. This review provided a comprehensive overview of TBL1XR1 in tumorigenesis, shedding new light on TBL1XR1 as a promising diagnostic biomarker and druggable target in cancer.

Lymphatic metastasis-related TBL1XR1 enhances stemness and metastasis in gastric cancer stem-like cells by activating ERK1/2-SOX2 signaling

The poor prognosis of gastric cancer (GC) results largely from metastasis and chemotherapy resistance. Toward novel therapeutic strategies that target or evade these phenomena, we evaluated the function of the transcriptional regulator transducin (β)-like 1 X-linked receptor 1 (TBL1XR1) in GC cells, including stem-like cells. In this study, the correlation of expression of TBL1XR1 and clinical features and GC patients' outcomes was evaluated. Knockdown or exogenous expression of TBL1XR1 was combined with in vitro (2D and 3D cultures) and in vivo (mouse lung and lymphatic metastasis models) assays to evaluate the function of TBL1XR1. TBL1XR1's downstream signaling was delineated by phospho-kinase array and knockdown of candidate mediators. Analysis of clinical data showed that TBL1XR1 overexpression was correlated with worse prognosis. Functional assays showed that TBL1XR1 promoted stemness, epithelial-mesenchymal transition (EMT), and lung and lymphatic metastasis in GC cells. TBL1XR1 activated ERK1/2-Sox2 signaling and was dependent on signaling via PI3K/AKT, in GC stem-like cells distinguished by CD44 expression. Moreover, inhibition of these signaling proteins reversed chemoresistance in in vitro and in vivo models. Taken together, our results indicate that TBL1XR1 promotes stemness and metastasis in GC, making it a potential prognostic indicator. The PI3K/AKT-TBL1XR1-ERK1/2-Sox2 axis may represent a target for the treatment of GC.

Genetic alterations in the 3q26.31-32 locus confer an aggressive prostate cancer phenotype

Large-scale genetic aberrations that underpin prostate cancer development and progression, such as copy-number alterations (CNAs), have been described but the consequences of specific changes in many identified loci is limited. Germline SNPs in the 3q26.31 locus are associated with aggressive prostate cancer, and is the location of NAALADL2, a gene overexpressed in aggressive disease. The closest gene to NAALADL2 is TBL1XR1, which is implicated in tumour development and progression. Using publicly-available cancer genomic data we report that NAALADL2 and TBL1XR1 gains/amplifications are more prevalent in aggressive sub-types of prostate cancer when compared to primary cohorts. In primary disease, gains/amplifications occurred in 15.99% (95% CI: 13.02–18.95) and 14.96% (95% CI: 12.08–17.84%) for NAALADL2 and TBL1XR1 respectively, increasing in frequency in higher Gleason grade and stage tumours. Gains/amplifications result in transcriptional changes and the development of a pro-proliferative and aggressive phenotype. These results support a pivotal role for copy-number gains in this genetic region.

Benjamin Simpson et al. use publicly available cancer genomic data to investigate copy number changes at the 3q26.31–32 locus, which has been associated with aggressive prostate cancer based on single-nucleotide polymorphisms. They find that gains of NAALADL2 and TBL1XR1 in this locus are associated with more aggressive subtypes of prostate cancer and the transcription of pro-proliferative signalling processes.

TBL1XR1 induces cell proliferation and inhibit cell apoptosis by the PI3K/AKT pathway in pancreatic ductal adenocarcinoma

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) is one of the deadliest solid tumors. Identification of diagnostic and therapeutic biomarkers for PDAC is urgently needed. Transducin (β)-like 1 X-linked receptor 1 (TBL1XR1) has been linked to the progression of various human cancers. Nevertheless, the function and role of TBL1XR1 in pancreatic cancers are unclear.

AIM

To elucidate the function and potential mechanism of TBL1XR1 in the development of PDAC.

METHODS

Ninety patients with histologically-confirmed PDAC were included in this study. PDAC tumor samples and cell lines were used to determine the expression of TBL1XR1. CCK-8 assays and colony formation assays were carried out to assess PDAC cell viability. Flow cytometry was performed to measure the changes in the cell cycle and cell apoptosis. Changes in related protein expression were measured by western blot analysis. Animal analysis was conducted to confirm the impact of TBL1XR1 in vivo.

RESULTS

Patients with TBL1XR1-positive tumors had worse overall survival than those with TBL1XR1-negative tumors. Moreover, we found that TBL1XR1 strongly promoted PDAC cell proliferation and inhibited PDAC cell apoptosis. Moreover, knockdown of TBL1XR1 induced G0/G1 phase arrest. In vivo animal studies confirmed that TBL1XR1 accelerated tumor cell growth. The results of western blot analysis showed that TBL1XR1 might play a key role in regulating PDAC cell proliferation and apoptosis via the PI3K/AKT pathway.

CONCLUSION

TBL1XR1 promoted PDAC cell progression and might be an effective diagnostic and therapeutic marker for pancreatic cancer.

Aberrant methylation of WD-repeat protein 41 contributes to tumour progression in triple-negative breast cancer

WD-repeat proteins are implicated in a variety of biological functions, most recently in oncogenesis. However, the underlying function of WD-repeat protein 41 (WDR41) in tumorigenesis remains elusive. The present study was aimed to explore the role of WDR41 in breast cancer. Combined with Western blotting and immunohistochemistry, the results showed that WDR41 was expressed at low levels in breast cancer, especially in triple-negative breast cancer (TNBC). Using methylation-specific PCR (MSP), we observed that WDR41 presented hypermethylation in MDA-MB-231 cells. Methylation inhibitor 5-aza-2'-deoxycytidine (5-aza-dC) management increased the expression of WDR41 in MDA-MB-231 cells, but not in MCF-10A (normal mammary epithelial cells) or oestrogen receptor-positive MCF-7 breast cancer cells. WDR41-down-regulation promoted, while WDR41-up-regulation inhibited the tumour characteristics of TNBC cells including cell viability, cell cycle and migration. Further, WDR41-up-regulation dramatically suppressed tumour growth in vivo. Mechanistically, WDR41 protein ablation activated, while WDR41-up-regulation repressed the AKT/GSK-3β pathway and the subsequent nuclear activation of β-catenin in MDA-MB-231 cells, and 5-aza-dC treatment enhanced this effect. After treatment with the AKT inhibitor MK-2206, WDR41-down-regulation-mediated activation of the GSK-3β/β-catenin signalling was robustly abolished. Collectively, methylated WDR41 in MDA-MB-231 cells promotes tumorigenesis through positively regulating the AKT/GSK-3β/β-catenin pathway, thus providing an important foundation for treating TNBC.

TBL1XR1 promotes migration and invasion in osteosarcoma cells and is negatively regulated by miR-186-5p

TBL1XR1 has been reported to play promoting roles in various malignances, yet little is known about its role in osteosarcoma, and the up-stream molecules regulating TBL1XR1 are also unclear. In the present study, we investigated the clinical significance of TBL1XR1 and its biological role in osteosarcoma, and further explored up-stream miRNAs regulating its expression. The results showed that TBL1XR1 was significantly up-regulated in osteosarcoma cells and tissues by using western blot and immunohistochemical staining. Overexpression of TBL1XR1 was positively related to adverse clinicopathological features and poor prognosis, and which may be an independent prognostic marker for osteosarcoma patients. Functional experiments revealed that down-regulation of TBL1XR1 inhibited proliferation, migration and invasion of osteosarcoma cells. Further studies indicated that TBL1XR1 was a direct target of miR-186-5p, and miR-186-5p negatively regulated TBL1XR1 expression. Moreover, TBL1XR1 was involved in miR-186-5p-repressed migration and invasion in osteosarcoma cells. Taken together, miR-186-5p/TBL1XR1 may be a novel therapeutic candidate target in osteosarcoma treatment.

TBL1XR1 as a potential therapeutic target that promotes epithelial-mesenchymal transition in lung squamous cell carcinoma

Transducin (β)-like 1 X-linked receptor 1 (TBL1XR1) has been demonstrated to serve a vital role in tumor progression. However, the biological role and molecular mechanisms of TBL1XR1 in lung squamous cell carcinoma (SCC) remain largely unknown. The purpose of the present study was to investigate the biological role of TBL1XR1 and its mechanism in lung SCC. TBL1XR1 was expressed in a human bronchial epithelial cell line and in lung SCC cell lines. The present study analyzed TBL1XR1-induced proliferation, invasion and migration abilities in vitro using the cell counting kit-8 assay, cell invasion assay and wound healing assay, respectively. This study examined the effects of TBL1XR1 on epithelial-mesenchymal transition (EMT) in lung SCC cells and activation of the transforming growth factor (TGF)-β/mothers against decapentaplegic homolog (Smad) signaling pathway by western blotting. The results indicated that TBL1XR1 was upregulated in lung SCC cells. Overexpression of TBL1XR1 increased the rate of cell proliferation compared with the control group. In vitro, overexpression of TBL1XR1 promoted cell invasion and migration ability compared with the control group. In addition, overexpression of TBL1XR1 produced a mesenchymal phenotype, while cells with downregulated TBL1XR1 produced an epithelial phenotype. Overexpression of TBL1XR1 significantly increased E-cadherin protein expression whilst snail family transcriptional repressor 1 (SNAI1), zinc finger E-box binding homebox 1 (ZEB1), p-Smad2/3, Smad2 and Smad3 protein expression was significantly reduced, compared with the control group. Downregulation of TBL1XR1 produced the opposite results. The present study indicated that TBL1XR1 contributed to lung SCC development and progression, and therefore TBL1XR1 may be a potential therapeutic target. TBL1XR1 may induce EMT of lung SCC cells through activation of the TGF-β/Smad signaling pathway.

REPA: Applying Pathway Analysis to Genome-Wide Transcription Factor Binding Data

Pathway analysis has been extensively applied to aid in the interpretation of the results of genome-wide transcription profiling studies, and has been shown to successfully find associations between the biological phenomena under study and biological pathways. There are two widely used approaches of pathway analysis: over-representation analysis, and gene set analysis. Recently genome-wide transcription factor binding data has become widely available allowing for the application of pathway analysis to this type of data. In this work, we developed regulatory enrichment pathway analysis (REPA) to apply gene set analysis to genome-wide transcription factor binding data to infer associations between transcription factors and biological pathways. We used the transcription factor binding data generated by the ENCODE project, and gene sets from the Molecular Signatures and KEGG databases. Our results showed that 54 percent of the predictions examined have literature support and that REPA's recall is roughly 54 percent. This level of precision is promising as several of REPA's predictions are expected to be novel and can be used to guide new research avenues. In addition, the results of our case studies showed that REPA enhances the interpretation of genome-wide transcription profiling studies by suggesting putative regulators behind the observed transcriptional responses.

Upregulation of E2F8 promotes cell proliferation and tumorigenicity in breast cancer by modulating G1/S phase transition

E2F transcription factors are involved in cell cycle regulation and synthesis of DNA in mammalian cells, and simultaneously play important roles in the development and progression of cancer when dysregulated. E2F8, a novel identified E2F family member, was found to be associated with the progression of several human cancers; however, the biological role and clinical significance of E2F8 in breast cancer remain to be further elucidated. Herein, we report that E2F8 is robustly elevated in breast cancer cell lines and clinical breast cancer tissue samples, respectively. The high expression level of E2F8 significantly correlates with clinical progression (P = 0.001), poor patient survival (P < 0.001) and a high Ki67 staining index (P = 0.008) in 187 human breast cancer specimens. Furthermore, we find that overexpressing E2F8 promotes, whereas silencing E2F8 suppresses, the proliferation and tumorigenicity of breast cancer cells both in vitro and in vivo. We further demonstrate that E2F8 transcriptionally upregulates CCNE1 and CCNE2 via directly interacting with their respective gene promoter, which accelerates the transition of G1 to S phase of breast cancer cells. Taken together, these findings uncover a novel biologic role and regulatory mechanism of E2F8 responsible for the progression of breast cancer, indicating E2F8 may represent a novel prognostic biomarker and therapeutic target against breast cancer.

Cytoplasmic, full length and novel cleaved variant, TBLR1 reduces apoptosis in prostate cancer under androgen deprivation

TBLR1/TBL1XR1, a core component of the nuclear receptor corepressor (NCoR) complex critical for the regulation of multiple nuclear receptors, is a transcriptional coactivator of androgen receptor (AR) and functions as a tumor suppressor when expressed in the nucleus in prostate. Subcellular localization of a protein is critical for its function, and although TBLR1, as a transcriptional cofactor, has been primarily viewed as a nuclear protein, many cells also express variable levels of cytoplasmic TBLR1 and its cytoplasmic specific functions have not been studied. Prostate cancer (PCa) cells express moderately higher level of cytoplasmic TBLR1 compared to benign prostate cells. When comparing androgen-dependent (AD) to androgen-independent (AI) PCa, AI cells contain very high levels of TBLR1 cytoplasmic expression and low levels of nuclear expression. Overexpression of cytoplasmic TBLR1 in AD cells inhibits apoptosis induced by androgen deprivation therapy, either in an androgen free condition or in the presence of bicalutamide. Additionally, we identified a cytoplasmic specific isoform of TBLR1 (cvTBLR1) approximately 5 kDa lower in molecular weight, that is expressed at higher levels in AI PCa cells. By immunoprecipitation, we purified cvTBLR1 and using mass spectrometry analysis combined with N-terminal TMPP labeling and Edman degradation, we identified the cleavage site of cvTBLR1 at amino acid 89, truncating the first 88 amino acids of the N-terminus of the full length protein. Functionally, cvTBLR1 expressed in the cytoplasm reduced apoptosis in PCa cells and promoted growth, migration, and invasion. Finally, we identified a nuclear export signal sequence for TBLR1 cellular localization by deletion and site-directed mutagenesis. The roles of TBLR1 and cvTBLR1 provide novel insights into the mechanism of castration resistance and new strategies for PCa therapy.

Targeting the p53-MDM2 interaction by the small-molecule MDM2 antagonist Nutlin-3a: a new challenged target therapy in adult Philadelphia positive acute lymphoblastic leukemia patients

MDM2 is an important negative regulator of p53 tumor suppressor. In this study, we sought to investigate the preclinical activity of the MDM2 antagonist, Nutlin-3a, in Philadelphia positive (Ph+) and negative (Ph-) leukemic cell line models, and primary B-acute lymphoblastic leukemia (ALL) patient samples. We demonstrated that Nutlin-3a treatment reduced viability and induced p53-mediated apoptosis in ALL cells with wild-type p53 protein, in a time and dose-dependent manner, resulting in the increased expression of pro-apoptotic proteins and key regulators of cell cycle arrest. The dose-dependent reduction in cell viability was confirmed in primary blast cells from B-ALL patients, including Ph+ ALL resistant patients carrying the T315I BCR-ABL1 mutation. Our findings provide a strong rational for further clinical investigation of Nutlin-3a in Ph+ and Ph- ALL.

USP44 Is an Integral Component of N-CoR that Contributes to Gene Repression by Deubiquitinating Histone H2B

Decreased expression of the USP44 deubiquitinase has been associated with global increases in H2Bub1 levels during mouse embryonic stem cell (mESC) differentiation. However, whether USP44 directly deubiquitinates histone H2B or how its activity is targeted to chromatin is not known. We identified USP44 as an integral subunit of the nuclear receptor co-repressor (N-CoR) complex. USP44 within N-CoR deubiquitinates H2B in vitro and in vivo, and ablation of USP44 impairs the repressive activity of the N-CoR complex. Chromatin immunoprecipitation (ChIP) experiments confirmed that USP44 recruitment reduces H2Bub1 levels at N-CoR target loci. Furthermore, high expression of USP44 correlates with reduced levels of H2Bub1 in the breast cancer cell line MDA-MB-231. Depletion of either USP44 or TBL1XR1 impairs the invasiveness of MDA-MB-231 cells in vitro and causes an increase of global H2Bub1 levels. Our findings indicate that USP44 contributes to N-CoR functions in regulating gene expression and is required for efficient invasiveness of triple-negative breast cancer cells.

Transducin (β)-like 1 X-linked receptor 1 correlates with clinical prognosis and clinicopathological characteristics in human solid carcinomas

Transducin (β)-like 1 X-linked receptor 1(TBL1XR1) has been reported to be overexpressed in various human cancers, as well as contributing to carcinogenesis and progression. This synthetic analysis was performed to assess whether TBL1XR1 protein could act as a potential prognostic molecular marker for human cancers. Several online databases (PubMed, Web of Science, Embase together with Wanfang and China National Knowledge Internet database) were retrieved to identify TBL1XR1-related publications. A total of ten studies with 1837 cancer patients were included in this meta-analysis. Hazard ratios (HR) with 95% confidence intervals (CI) were applied to assess the association between TBL1XR1 expression and cancer prognosis. Odds ratios (OR) were calculated to determine the relationship between TBL1XR1 expression and clinicopathological characteristics. The overall results revealed that the overexpression of TBL1XR1 was correlated with poorer overall survival (OS) (HR: 1.77, 95% CI: 1.49–2.06, p < 0.001) and worse disease-free survival (DFS) (HR: 1.51, 95% CI: 1.19–1.84, p < 0.001) in human solid cancers. Statistical significance for OS was also found in subgroup analysis stratified by the cancer type, analysis method and follow-up time. Furthermore, elevated TBL1XR1 was associated with unfavorable clinicopathological characteristics including tumor size, depth of invasion, lymph node metastasis and TNM stage. Our meta-analysis suggested that TBL1XR1 might be served as a novel and promising biomarker to predict prognosis and clinicopathologic characteristic for cancer patients.

TBL1XR1 predicts isolated tumor cells and micrometastasis in patients with TNM stage I/II colorectal cancer

BACKGROUND AND AIM

A considerable number of early-stage colorectal cancer (CRC) patients may develop cancer relapse or metastasis after curative surgery. Isolated tumor cells (ITC) and micrometastasis in lymph nodes (LNMM), which are undetectable by conventional pathological examination, may be one primary reason. Detection of ITC/LNMM is time-consuming and cost-ineffective; we aimed to find biomarkers in primary CRC tissues to help predicting ITC/LNMM status.

METHODS

We enrolled 137 node-negative patients with early-stage CRC in this study. Existence of ITC/LNMM was identified by immunohistological staining with cytokeratin 20 in resected lymph nodes. Expression of transducin (β)-like 1 X-linked receptor 1 (TBL1XR1) in primary CRC tissues was also investigated. Chi-squared test was performed to reveal the correlations between ITC/LNMM and clinicopathological characteristics. Univariate and multivariate analyses were used to determine independent prognostic factors. Knockdown experiment together with proliferation and invasion assays were carried out to explore molecular mechanisms between TBL1XR1 and ITC/LNMM.

RESULTS

About 29.2% (40/137) patients were identified as ITC/LNMM positive, and most of them (32/40 cases, 80%) showed high TBL1XR1 expression in primary CRC tissues. Both ITC/LNMM and TBL1XR1 expression were independent prognostic factors for disease relapse or metastasis. In vitro experiments demonstrated that TBL1XR1 can regulate the expression of vascular endothelial growth factor C and epithelial-mesenchymal transition proteins, thus mediate the process of lymph node metastasis.

CONCLUSIONS

Identification of ITC/LNMM is significant in evaluating clinical outcome and guiding adjuvant chemotherapy for early-stage CRC patients. TBL1XR1 overexpression in CRC tissues can serve as an efficient biomarker to predict the status of ITC/LNMM.

PHF21B overexpression promotes cancer stem cell-like traits in prostate cancer cells by activating the Wnt/β-catenin signaling pathway

Background

PHF21B is newly identified to be involved in the tumor progression; however, its biological role and molecular mechanism in prostate cancer have not been defined. This study is aimed to study the role of PHF21B in the progression of prostate cancer.

Methods

Real-time PCR, immunohistochemistry and western blotting analysis were used to determine PHF21B expression in prostate cancer cell lines and clinical specimens. The role of PHF21B in maintaining prostate cancer stem cell-like phenotype was examined by tumor-sphere formation assay and expression levels of stem cell markers. Luciferase reporter assay, western blot analysis, enzyme-linked immunosorbent assay and ChIP assay were used to determine whether PHF21B activates the Wnt/β-catenin signaling by transcriptionally downregulating SFRP1 and SFRP2.

Results

Our results revealed that PHF21B was markedly upregulated in prostate cancer cell lines and tissues. High PHF21B levels predicted poorer recurrence-free survival in prostate cancer patients. Gain-of-function and loss-of-function studies showed that overexpression of PHF21B enhanced, while downregulation suppressed, the cancer stem cell-like phenotype in prostate cancer cells. Xenograft tumor model showed that silencing PHF21B decreased the ability of tumorigenicity in vivo. Notably, Wnt/β-catenin signaling was hyperactivated in prostate cancer cells overexpressing PHF21B, and mediated PHF21B-induced cancer stem cell-like phenotype. Furthermore, PHF21B suppressed repressors of the Wnt/β-catenin signaling cascade, including SFRP1 and SFRP2. These results demonstrated that PHF21B constitutively activated wnt/β-catenin signaling by transcriptionally downregulating SFRP1 and SFRP2, which promotes prostate cancer stem cell-like phenotype.

Conclusions

Our results revealed that PHF21B functions as an oncogene in prostate cancer, and may represent a promising prognostic biomarker and an attractive candidate for target therapy of prostate cancer.

Electronic supplementary material

The online version of this article (doi:10.1186/s13046-017-0560-y) contains supplementary material, which is available to authorized users.

Triple-negative breast cancer: New therapeutic options via signalling transduction cascades

Triple-negative breast cancer is a highly aggressive type of mammalian carcinoma. It is defined by a rather weak expression of estrogen-, progesterone- and Her2-receptor, and is thus difficult to treat, resulting in low disease-free and overall survival rates of the affected patients. Hence it is important to find new therapeutic options. To this aim we analysed the incidence of some molecules from different signal transduction cascades by immunohistochemistry, which are known to correlate with triple-negative breast cancer, and correlated the expression of these molecules to different tumour traits, such as size, grading, menopausal stage, histology, lymph node affection, remote metastasis formation, and to the incidence of local and lymph node recurrence and metastasis by statistical analysis. Statistically significant correlations were found for a number of tumour characteristics and signalling molecules: HIF1α is correlated to tumour grading, β-catenin to the menopausal state of the patient, and for Notch1 a relation to lymph node affection is seen. In terms of different recurrences, a correlation of β-catenin to metastasis formation and lymph node affection could be shown, as well as coherences between XBP1 and lymph node recurrence, Notch1 and metastasis formation and FOXP3 and the occurrence of local recurrence. The presented results are in accordance with formerly published studies and therefore might comprise opportunities to develop new therapeutical strategies, which could help to handle this aggressive form of breast cancer in a manner, by which side effects would be reduced and therapeutical efficiency is increased.

Correlations between TBL1XR1 and recurrence of colorectal cancer

More than 25% localized CRC patients died from post-operative metastasis, and risk of metastasis varies among individuals due to the high heterogeneity of CRC. Therefore, figuring out potential biomarkers for disease recurrence would be invaluable to improve the follow-up efficiency and clinical treatment. Transducin (β)-like 1 X-linked receptor 1 (TBL1XR1) is a core component of the nuclear receptor corepressor complex, which functions as a repressive coregulatory factor for multiple transcription factors. The clinical significance of TBL1XR1 in CRC hasn’t been fully elucidated. In this study, we investigated the expression of TBL1XR1 in primary CRC tissues and liver metastases from TNM stage IV CRC patients, and found that its expression in primary tumor tissues was an independent prognostic factor for tumor recurrence. Thus, we enrolled another cohort including TNM stage I-III patients to further evaluate the relationship between TBL1XR1 expression and disease recurrence. Accordingly, high TBL1XR1 expression indicates poor disease-free survival of stage I-III CRC patients. Furthermore, we confirmed the importance of β-catenin signaling pathways in TBL1XR1-mediated CRC cell oncogenicity by clinical and cellular results. Our results emphasize the necessity of individual therapy decisions based on clinical biomarkers, especially for localized CRC patients who are not routinely treated with adjunctive chemotherapy.

Rab14 Suppression Mediated by MiR-320a Inhibits Cell Proliferation, Migration and Invasion in Breast Cancer

We found that microRNA-320a (miR-320a) was an attractive prognostic biomarker in breast cancer (BC) previously, whereas its regulatory mechanism in BC was not well understood. Our aim was to identify miR-320a target gene, examine the clinical relationship between miR-320a and its target, and further explore the functions of its target in BC. In this study, miR-320a downstream target gene was determined in HEK-293T cells by dual luciferase reporter assay. Then western blotting and immunohistochemistry were used to assess miR-320a target gene expression in fresh frozen (n=19, breast cancer and matched non-malignant adjacent tissue samples) and formalin-fixed paraffin-embedded (FFPE) (n=130, invasive BC tissues, the same panel detected for miR-320a expression previously) breast tissues, respectively. The results suggested that miR-320a could significantly suppressed Rab14 3'-untranslated region luciferase-reporter activity, and thus Rab14 was first identified as miR-320a target in BC. In 19 matched breast tissues, 12 (63%) breast cancer tissues showed high expression of Rab14 compared with the corresponding normal tissues. Rab14 immunoreactivity was mainly detected in the cytoplasm, 77/130 (59.2%) showed high expression. Furthermore, Rab14 expression was found to be inversely correlated with miR-320a expression in fresh-frozen breast tissues as well as in FFPE invasive breast cancer samples. In addition, Rab14 expression levels were positively related to tumor size (P = 0.034), lymph node metastasis (P < 0.001), distant metastasis (P = 0.001), histological grade (P = 0.035) and clinical tumor lymph-node metastasis stage (P = 0.001). Patients with higher Rab14 expression showed shorter overall survival time. Moreover, silencing of Rab14 could suppress proliferation, migration and invasion in breast cancer cell lines. Collectively, our results indicate that miR-320a could target Rab14 and that they could interact biologically in BC.

Transducin (β)-like 1 X-linked receptor 1 promotes gastric cancer progression via the ERK1/2 pathway

Gastric cancer (GC) is one of the most common types of cancer worldwide, and it involves extensive local tumour invasion, metastasis and poor prognosis. Understanding the mechanisms regulating the progression of GC is necessary for the development of effective therapeutic strategies. Transducin (β)-like 1 X-linked receptor 1 (TBL1XR1) is an important regulator controlling gene activation and repression, which has been thought to be involved in tumorigenesis. However, the role of TBL1XR1 in human GC remains largely unknown. Here, we find that TBL1XR1 is aberrantly expressed in human GC tissues, and TBL1XR1 levels are highly correlated with local tumour invasion, late tumor, lymph node, metastasis (TNM) stage and poor prognosis. Knockdown of TBL1XR1 by shRNA inhibits GC cell proliferation, migration, invasion, epithelial-mesenchymal transition (EMT) in vitro, as well as tumorigenesis and peritoneal metastasis in vivo, whereas overexpression of TBL1XR1 produces the opposite effects. These effects are mediated by activation of the ERK1/2 signalling pathway, and inhibition of this pathway with a specific ERK1/2 inhibitor (U0126) significantly impairs the tumour-promoting effects induced by TBL1XR1. Moreover, TBL1XR1 mediated ERK1/2 activation is dependent on the β-catenin/MMP7/EGFR signalling pathway. In conclusion, TBL1XR1 contributes to GC tumorigenesis and progression through the activation of the β-catenin/MMP7/EGFR/ERK signalling pathway and may act as a new therapeutic target for GC.

Nuclear TBLR1 as an ER corepressor promotes cell proliferation, migration and invasion in breast and ovarian cancer

Estrogen receptors (ER) play important roles in the development and progression of breast and ovarian cancers. ERs mediate transcriptional regulation through interaction with cofactors and binding to response elements within the regulatory elements of target genes. Here, we examined the expression and function of TBLR1/TBL1XR1, a core component of NCoR (nuclear receptor corepressor) and SMRT (silencing mediator of retinoic acid and thyroid receptor) corepressor complexes, in breast and ovarian cancers. We found that although TBLR1 is present in both the nucleus and cytoplasm of normal and neoplastic breast and ovarian cells, it is expressed at significantly higher levels in the nucleus of malignant breast and ovarian cells compared to benign cells. TBLR1 functions as an ER corepressor to inhibit ER-mediated transcriptional activation in both breast and ovarian cell lines, but it has no effect on androgen receptor (AR) mediated transcriptional activation in these cells. Furthermore, ectopic expression of nuclear TBLR1 in breast and ovarian cancer cells stimulates cell proliferation. The increased cell proliferation by nuclear TBLR1 is through both ER-independent and ER-dependent mechanisms as evidenced by increased growth in hormone-free medium and estrogen medium, as well as reduced growth with ER knockdown by siRNA. Nuclear TBLR1 overexpression also increased migration and invasion in both breast and ovarian cancer cells. Determining the functional relationship between TBLR1 and ER may provide insights to develop novel treatment strategies and improve response to hormonal therapy in breast and ovarian cancers.

TBL1XR1 Is Highly Expressed in Gastric Cancer and Predicts Poor Prognosis

Objective. To investigate the expression of transducin- (β-) like 1 X-linked receptor 1 (TBL1XR1) in human gastric cancer (GC) and its correlation with prognostic and biologic significance. Methods. TBL1XR1 mRNA expression was analyzed in gastric cancer using a microarray dataset (GSE2701) from the Gene Expression Omnibus (GEO). Immunohistochemistry (IHC) analysis of TBL1XR1 was performed on GC tissue microarray (TMA) to assess its prognostic and biological significance in 334 patients of GC. Results. Analysis of GSE2701 showed that the mRNA levels of TBL1XR1 were significantly elevated in primary gastric tumor and lymph node tissues than normal gastric tissues (P < 0.05). The same results of TBL1XR1 protein level were observed by IHC staining in 334 GC tissues. 204 of 334 (60.1%) primary gastric cancer tissues showed high expression of TBL1XR1 protein. TBL1XR1 overexpression was significantly correlated with lymph node metastasis (P = 0.000) and advanced TNM stage (P = 0.001). Moreover, high levels of TBL1XR1 predicted worse overall survival (P = 0.015). Multivariate Cox regression analysis indicated that high expression of TBL1XR1 was an independent prognostic factor for poor overall survival (HR, 0.525; 95% confidence interval, 0.367–0.752; P = 0.005). Conclusion. This present study demonstrates that TBL1XR1 is overexpressed in gastric cancer and may be a potential predictor and therapeutic target for GC patients.

Transducin (Beta)-Like 1 X-Linked Receptor 1 Correlates with Clinical Prognosis and Epithelial-Mesenchymal Transition in Hepatocellular Carcinoma

BACKGROUND

Recent studies have demonstrated that transducin (beta)-like 1 X-linked receptor 1 (TBLR1) is involved in tumor progression. However, the exact role and clinical significance of TBLR1 in hepatocellular carcinoma (HCC) are poorly understood.

AIM

In this study, we aimed to investigate the expression and clinical significance of TBLR1 in HCC.

METHODS

Quantitative polymerase chain reaction and immunohistochemical staining were performed to detect the expression levels of TBLR1 in HCC tissue and adjacent noncancerous tissue (ANT). The relationships between TBLR1 expression and clinicopathological factors were examined in this study. The effects of TBLR1 on epithelial-mesenchymal transition (EMT) of HCC cells were investigated in vitro.

RESULTS

The expression levels of TBLR1 were elevated in HCC cell lines. TBLR1 mRNA in HCC tissue was markedly higher (P < 0.001) than that in ANT. High expression of TBLR1 is closely related to serum alpha fetoprotein (P = 0.047), BCLC stage (P < 0.001), maximum size of tumors (P < 0.001), tumor embolus (P < 0.001), and histological grade (P < 0.001). The disease-free survival and overall survival of HCC patients with high expression of TBLR1 were significantly shorter. Furthermore, we found that EMT of HCC cells could be induced by up-regulating TBLR1 and be inhibited by down-regulating TBLR1. ICG-001, the inhibitor of Wnt/β-catenin signaling, could suppress induction of EMT mediated by TBLR1.

CONCLUSIONS

Our finding suggested that TBLR1 is likely to be a potential prognostic indicator and therapeutic target for HCC and that TBLR1 may be implicated in EMT of HCC cells.

The chromosome 3q26 OncCassette: A multigenic driver of human cancer

Recurrent copy number variations (CNVs) are genetic alterations commonly observed in human tumors. One of the most frequent CNVs in human tumors involves copy number gains (CNGs) at chromosome 3q26, which is estimated to occur in >20% of human tumors. The high prevalence and frequent occurrence of 3q26 CNG suggest that it drives the biology of tumors harboring this genetic alteration. The chromosomal region subject to CNG (the 3q26 amplicon) spans from chromosome 3q26 to q29, a region containing ∼200 protein-encoding genes. The large number of genes within the amplicon makes it difficult to identify relevant oncogenic target(s). Whereas a number of genes in this region have been linked to the transformed phenotype, recent studies indicate a high level of cooperativity among a subset of frequently amplified 3q26 genes. Here we use a novel bioinformatics approach to identify potential driver genes within the recurrent 3q26 amplicon in lung squamous cell carcinoma (LSCC). Our analysis reveals a set of 35 3q26 amplicon genes that are coordinately amplified and overexpressed in human LSCC tumors, and that also map to a major LSCC susceptibility locus identified on mouse chromosome 3 that is syntenic with human chromosome 3q26. Pathway analysis reveals that 21 of these genes exist within a single predicted network module. Four 3q26 genes, SOX2, ECT2, PRKCI and PI3KCA occupy the hub of this network module and serve as nodal genes around which the network is organized. Integration of available genetic, genomic, biochemical and functional data demonstrates that SOX2, ECT2, PRKCI and PIK3CA are cooperating oncogenes that function within an integrated cell signaling network that drives a highly aggressive, stem-like phenotype in LSCC tumors harboring 3q26 amplification. Based on the high level of genomic, genetic, biochemical and functional integration amongst these 4 3q26 nodal genes, we propose that they are the key oncogenic targets of the 3q26 amplicon and together define a "3q26 OncCassette" that mediates 3q26 CNG-driven tumorigenesis. Genomic analysis indicates that the 3q26 OncCassette also operates in other major tumor types that exhibit frequent 3q26 CNGs, including head and neck squamous cell carcinoma (HNSCC), ovarian serous cancer and cervical cancer. Finally, we discuss how the 3q26 OncCassette represents a tractable target for development of novel therapeutic intervention strategies that hold promise for improving treatment of 3q26-driven cancers.

TBL1XR1 in physiological and pathological states

Transducin (beta)-like 1X related protein 1 (TBL1XR1/TBLR1) is an integral subunit of the NCoR (nuclear receptor corepressor) and SMRT (silencing mediator of retinoic acid and thyroid hormone receptors) repressor complexes. It is an evolutionally conserved protein that shares high similarity across all species. TBL1XR1 is essential for transcriptional repression mediated by unliganded nuclear receptors (NRs) and othe regulated transcription factors (TFs). However, it can also act as a transcription activator through the recruitment of the ubiquitin-conjugating/19S proteasome complex that mediates the exchange of corepressors for coactivators. TBL1XR1 is required for the activation of multiple intracellular signaling pathways. TBL1XR1 germline mutations and recurrent mutations are linked to intellectual disability. Upregulation of TBL1XR1 is observed in a variety of solid tumors, which is associated with advanced tumor stage, metastasis and poor prognosis. A variety of genomic alterations, such as translocation, deletion and mutation have been identified in many types of neoplasms. Loss of TBL1XR1 in B-lymphoblastic leukemia disrupts glucocorticoid receptor recruitment to chromatin and results in glucocorticoid resistance. However, the mechanisms of other types of genomic changes in tumorogenesis are still not clear. A pre-clinical study has shown that the disruption of the interaction between TBL1X and β-catenin using a small molecule can inhibit the growth of AML stem and blast cells both in vitro and in vivo. These findings shed light on the therapeutic potentials of targeting TBL1XR1 related proteins in cancer treatment.