TBLR1 as an androgen receptor (AR) coactivator selectively activates AR target genes to inhibit prostate cancer growth

Multi-Omics Characterization of E3 Regulatory Patterns in Different Cancer Types

Ubiquitination, a post-translational modification, refers to the covalent attachment of ubiquitin molecules to substrates. This modification plays a critical role in diverse cellular processes such as protein degradation. The specificity of ubiquitination for substrates is regulated by E3 ubiquitin ligases. Dysregulation of ubiquitination has been associated with numerous diseases, including cancers. In our study, we first investigated the protein expression patterns of E3 ligases across 12 cancer types. Our findings indicated that E3 ligases tend to be up-regulated and exhibit reduced tissue specificity in tumors. Moreover, the correlation of protein expression between E3 ligases and substrates demonstrated significant changes in cancers, suggesting that E3-substrate specificity alters in tumors compared to normal tissues. By integrating transcriptome, proteome, and ubiquitylome data, we further characterized the E3-substrate regulatory patterns in lung squamous cell carcinoma. Our analysis revealed that the upregulation of the SKP2 E3 ligase leads to excessive degradation of BRCA2, potentially promoting tumor cell proliferation and metastasis. Furthermore, the upregulation of E3 ubiquitin-protein ligase TRIM33 was identified as a biomarker associated with a favorable prognosis by inhibiting the cell cycle. This work exemplifies how leveraging multi-omics data to analyze E3 ligases across various cancers can unveil prognosis biomarkers and facilitate the identification of potential drug targets for cancer therapy.

iIMPACT: integrating image and molecular profiles for spatial transcriptomics analysis

Current clustering analysis of spatial transcriptomics data primarily relies on molecular information and fails to fully exploit the morphological features present in histology images, leading to compromised accuracy and interpretability. To overcome these limitations, we have developed a multi-stage statistical method called iIMPACT. It identifies and defines histology-based spatial domains based on AI-reconstructed histology images and spatial context of gene expression measurements, and detects domain-specific differentially expressed genes. Through multiple case studies, we demonstrate iIMPACT outperforms existing methods in accuracy and interpretability and provides insights into the cellular spatial organization and landscape of functional genes within spatial transcriptomics data.

Androgen Receptor-Interacting Proteins in Prostate Cancer Development and Therapy Resistance

Endocrine therapy for prostate cancer is based on the use of drugs that diminish androgen concentration and androgen receptor (AR) signaling inhibitors and is limited by the functional consequences of AR point mutations and increased expression of constitutively active receptors. Many coactivators (>280) interact with different AR regions. Most studies have determined the expression of coactivators and their effects in the presence of increasing concentrations of androgen or the antiandrogen enzalutamide. The p160 group of coactivators (SRC-1, SRC-2, and SRC-3) is highly expressed in prostate cancer and contributes to ligand-dependent activation of the receptor in models that represent therapy-sensitive and therapy-resistant cell lines. The transcriptional coactivators p300 and CREB-binding protein (CBP) are implicated in the regulation of a large number of cellular events, such as proliferation, apoptosis, migration, and invasion. AR coactivators also may predict biochemical and clinical recurrence. The AR coactivator expression, which is enhanced in enzalutamide resistance, includes growth regulating estrogen receptor binding 1 (GREB1) and GATA-binding protein 2 (GATA2). Several coactivators also activate AR-unrelated signaling pathways, such as those of insulin-like growth factors, which inhibit apoptosis in cancer cells. They are expressed in multiple models of resistance to therapy and can be targeted by various inhibitors in vitro and in vivo. The role of the glucocorticoid receptor in endocrine therapy-resistant prostate cancer has been documented previously. Specific coactivators may interact with the glucocorticoid receptor, thus contributing to therapy failure.

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.

Research Progress of DUB Enzyme in Hepatocellular Carcinoma

According to GLOBOCAN 2021 cancer incidence and mortality statistics compiled by the International Agency for Research on Cancer, hepatocellular carcinoma (HCC) is the most common malignancy in the human liver and one of the leading causes of cancer death worldwide. Although there have been great advances in the treatment of HCC, such as regofenib, sorafenib, and lomvatinib, which have been developed and approved for the clinical treatment of advanced or metastatic HCC. However, they only prolong survival by a few months, and patients with advanced liver cancer are susceptible to tumor invasion metastasis and drug resistance. Ubiquitination modification is a type of post-translational modification of proteins. It can affect the physiological activity of cells by regulating the localization, stability and activity of proteins, such as: gene transcription, DNA damage signaling and other pathways. The reversible process of ubiquitination is called de-ubiquitination: it is the process of re-releasing ubiquitinated substrates with the participation of de-ubiquitinases (DUBs) and other active substances. There is growing evidence that many dysregulations of DUBs are associated with tumorigenesis. Although dysregulation of deuquitinase function is often found in HCC and other cancers, The mechanisms of action of many DUBs in HCC have not been elucidated. In this review, we focused on several deubiquitinases (DUBs) associated with hepatocellular carcinoma, including their structure, function, and relationship to hepatocellular carcinoma. hepatocellular carcinoma was highlighted, as well as the latest research reports. Among them, we focus on the USP family and OTU family which are more studied in the HCC. In addition, we discussed the prospects and significance of targeting DUBs as a new strategy for the treatment of hepatocellular carcinoma. It also briefly summarizes the research progress of some DUB-related small molecule inhibitors and their clinical application significance as a treatment for HCC in the future.

Oncogenic role of PinX1 in prostate cancer cells through androgen receptor dependent and independent mechanisms

Coregulators play an important role in prostate cancer (PCa), modulating androgen receptor (AR) action and representing a possible cause of androgen deprivation therapy failure. Pin2-interacting protein X1 (PinX1) is a nucleolar protein described as a steroid hormone receptor coregulator in breast cancer cell lines. In this work, we studied the effect of PinX1 on AR action in PCa. Our results demonstrate that PinX1 acts as an AR coactivator, increasing its transcriptional activity and target gene expression, as well as proliferation, migration and colony formation in PCa cell lines. These effects are observed in the presence and absence of AR agonist and antagonists, suggesting a possible androgen independent pathway for PinX1. We present the first oncogenic roles described for PinX1, acting as a coactivator of the AR.

Deficiency of TBL1XR1 causes asthenozoospermia

Transducin (β)-like 1 X-linked receptor 1 (TBL1XR1) is an evolutionarily conserved protein related to spermatozoa. To clarify its role and mechanism of action in spermatozoa, qRT-PCR was used to analyse the expression of TBL1XR1 in human spermatozoa and mouse testes. The mice were established as an animal model by injecting the mice testes with small interfering RNA against TBL1XR1 or control siRNA. Our results indicated that deficiency of TBL1XR1 in mice reduced the motility of spermatozoa and disrupted the histone-to-protamine transition. We also found the decreased expression of TBL1XR1 in the spermatozoa of human patients with asthenozoospermia (AZ) compared with that in the spermatozoa of healthy males. Moreover, we carried out chromatin immunoprecipitation analyses and found that genes downstream of TBL1XR1 were related to sperm motility. Thus, TBL1XR1 might be related to sperm motility and might function through its downstream genes. Our data highlight the role of TBL1XR1 involved in spermatozoa and provide new molecular insights into the intricate systems required for male fertility.

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.

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.

The COSMIC Cancer Gene Census: describing genetic dysfunction across all human cancers

The Catalogue of Somatic Mutations in Cancer (COSMIC) Cancer Gene Census (CGC) is an expert-curated description of the genes driving human cancer that is used as a standard in cancer genetics across basic research, medical reporting and pharmaceutical development. After a major expansion and complete re-evaluation, the 2018 CGC describes in detail the effect of 719 cancer-driving genes. The recent expansion includes functional and mechanistic descriptions of how each gene contributes to disease generation in terms of the key cancer hallmarks and the impact of mutations on gene and protein function. These functional characteristics depict the extraordinary complexity of cancer biology and suggest multiple cancer-related functions for many genes, which are often highly tissue-dependent or tumour stage-dependent. The 2018 CGC encompasses a second tier, describing an expanding list of genes (currently 145) from more recent cancer studies that show supportive but less detailed indications of a role in cancer.

Sequencing of prostate cancers identifies new cancer genes, routes of progression and drug targets

Prostate cancer represents a substantial clinical challenge because it is difficult to predict outcome and advanced disease is often fatal. We sequenced the whole genomes of 112 primary and metastatic prostate cancer samples. From joint analysis of these cancers with those from previous studies (930 cancers in total), we found evidence for 22 previously unidentified putative driver genes harboring coding mutations, as well as evidence for NEAT1 and FOXA1 acting as drivers through noncoding mutations. Through the temporal dissection of aberrations, we identified driver mutations specifically associated with steps in the progression of prostate cancer, establishing, for example, loss of CHD1 and BRCA2 as early events in cancer development of ETS fusion-negative cancers. Computational chemogenomic (canSAR) analysis of prostate cancer mutations identified 11 targets of approved drugs, 7 targets of investigational drugs, and 62 targets of compounds that may be active and should be considered candidates for future clinical trials.

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.

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.

The mutational landscape of ocular marginal zone lymphoma identifies frequent alterations in TNFAIP3 followed by mutations in TBL1XR1 and CREBBP

Ocular marginal zone lymphoma is a common type of low-grade B-cell lymphoma. To investigate the genomic changes that occur in ocular marginal zone lymphoma, we analyzed 10 cases of ocular marginal zone lymphoma using whole-genome and RNA sequencing and an additional 38 cases using targeted sequencing. Major genetic alterations affecting genes involved in nuclear factor (NF)-κB pathway activation (60%), chromatin modification and transcriptional regulation (44%), and B-cell differentiation (23%) were identified. In whole-genome sequencing, the 6q23.3 region containing TNFAIP3 was deleted in 5 samples (50%). In addition, 5 structural variation breakpoints in the first intron of IL20RA located in the 6q23.3 region was found in 3 samples (30%). In targeted sequencing, a disruptive mutation of TNFAIP3 was the most common alteration (54%), followed by mutations of TBL1XR1 (18%), cAMP response element binding proteins (CREBBP) (17%) and KMT2D (6%). All TBL1XR1 mutations were located within the WD40 domain, and TBL1XR1 mutants transfected into 293T cells increased TBL1XR1 binding with nuclear receptor corepressor (NCoR), leading to increased degradation of NCoR and the activation of NF-κB and JUN target genes. This study confirms genes involving in the activation of the NF-kB signaling pathway is the major driver in the oncogenesis of ocular MZL.

Dissecting the roles of the androgen receptor in prostate cancer from molecular perspectives

Androgen receptor plays a pivotal role in prostate cancer progression, and androgen deprivation therapy to intercept androgen receptor signal pathway is an indispensable treatment for most advanced prostate cancer patients to delay cancer progression. However, the emerging of castration-resistant prostate cancer reminds us the alteration of androgen receptor, which includes androgen receptor mutation, the formation of androgen receptor variants, and androgen receptor distribution in cancer cells. In this review, we introduce the process of androgen receptor and also its variants' formation, translocation, and function alteration by protein modification or interaction with other pathways. We dissect the roles of androgen receptor in prostate cancer from molecular perspective to provide clues for battling prostate cancer, especially castration-resistant prostate cancer.

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.

Androgen Receptor Coactivators in Regulation of Growth and Differentiation in Prostate Cancer

Androgen receptor (AR) is a key factor in regulation of growth and differentiation in normal and malignant prostate. Endocrine therapies for prostate cancer include inhibition of androgen production either by analogs of luteinizing hormone releasing hormone or abiraterone acetate and/or use of anti-androgens such as hydroxyflutamide, bicalutamide, and enzalutamide. Castration therapy-resistant cancer develops inevitably in patients who undergo treatment. AR coactivators are proteins which interact with one or more regions of the AR thus enhancing its function. Although several functions of AR coactivators may be redundant, specific functions have been identified and analyzed. The p160 group of coactivators, SRC-1, -2, and -3 not only potentiate the activation of the AR, but are also implicated in potentiation of function of insulin-like growth factor-I and activation of the Akt pathway. Transcriptional integrators p300 and CBP are up-regulated by androgen ablation and may influence antagonist/agonist balance of non-steroidal anti-androgens. A therapy approach designed to target p300 in prostate cancer revealed its role in regulation of proliferation of migration of androgen-sensitive and -insensitive prostate cancer cells. Coactivators p300 and SRC-1 are required for AR activation by interleukin-6 (IL-6), a cytokine that is overexpressed in castration therapy-resistant prostate cancer. Some coactivators, such as Vav3, are involved in regulation of transcriptional activity of truncated AR, which emerge during endocrine thrapy. Stimulation of cellular migration and invasion by AR coactivators has also been described. Translational studies with aim to introduce anti-AR coactivator therapy have not been successfully implemented in the clinic so far.

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.

MDC1 functionally identified as an androgen receptor co-activator participates in suppression of prostate cancer

Mediator of DNA damage checkpoint protein 1 (MDC1) is essential for DNA damage response. However, the role of MDC1 in modulating gene transcription independently of DNA damage and the underlying mechanisms have not been fully defined. Androgen receptor (AR) is the central signaling pathway in prostate cancer (PCa) and its target genes are involved in both promotion and suppression of PCa. Here, we functionally identified MDC1 as a co-activator of AR. We demonstrate that MDC1 facilitates the association between AR and histone acetyltransferase GCN5, thereby increasing histone H3 acetylation level on cis-regulatory elements of AR target genes. MDC1 knockdown promotes PCa cells growth and migration. Moreover, depletion of MDC1 results in decreased expression of a subset of the endogenous androgen-induced target genes, including cell cycle negative regulator p21 and PCa metastasis inhibitor Vinculin, in AR positive PCa cell lines. Finally, the expression of MDC1 and p21 correlates negatively with aggressive phenotype of clinical PCa. These studies suggest that MDC1 as an epigenetic modifier regulates AR transcriptional activity and MDC1 may function as a tumor suppressor of PCa, and provide new insight into co-factor-AR-signaling pathway mechanism and a better understanding of the function of MDC1 on PCa.

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.

Nuclear receptor corepressor complexes in cancer: mechanism, function and regulation

Nuclear receptor corepressor (NCoR) and silencing mediator for retinoid and thyroid hormone receptors (SMRT) function as corepressors for diverse transcription factors including nuclear receptors such as estrogen receptors and androgen receptors. Deregulated functions of NCoR and SMRT have been observed in many types of cancers and leukemias. NCoR and SMRT directly bind to transcription factors and nucleate the formation of stable complexes that include histone deacetylase 3, transducin b-like protein 1/TBL1-related protein 1, and G-protein pathway suppressor 2. These NCoR/SMRT-interacting proteins also show deregulated functions in cancers. In this review, we summarize the literature on the mechanism, regulation, and function of the core components of NCoR/SMRT complexes in the context of their involvement in cancers and leukemias. While the current studies support the view that the corepressors are promising targets for cancer treatment, elucidation of the mechanisms of corepressors involved in individual types of cancers is likely required for effective therapy.

Androgen receptor coactivators that inhibit prostate cancer growth

It is well documented that androgen receptor (AR), a steroid hormone receptor, is important for prostate cancer (PCa) growth. Conversely, however, there is increasing evidence that activation of AR by androgens can also lead to growth suppression in prostate cells. AR mediated transcription is regulated by a number of different transcriptional coactivators. Changes in expression level or cellular localization of specific coactivators may play a crucial role in this switch between proliferative and anti- proliferative processes regulated by AR target gene programs. In this review, we discuss the expression and function of several AR coactivators exhibiting growth suppressive function in PCa, including ARA70/ELE1/NCOA4, androgen receptor coactivator p44/MEP50/WDR77, TBLR1, and ART-27. In luciferase reporter assays, they all have been shown to activate AR mediated transcriptional activation. ARA70 exists in two forms, the full length nuclear ARA70α and internally spliced cytoplasmic ARA70β. For p44 and TBLR1, we identified nuclear and cytoplasmic forms with distinct expression and function. In comparison of their expression (ARA70α, p44, TBLR1 and ART-27) in prostate, these coactivators are expressed in the nucleus of benign prostate epithelial cells while they are more predominantly expressed in cytoplasmic form (ARA70β, cytoplasmic p44 and TBLR1) in PCa. Consistent with their nuclear expression in benign prostate, the nuclear form of these coactivators inhibit PCa growth targeting a subset of AR target genes. In contrast, the cytoplasmic versions of these proteins enhance PCa growth and invasion. Interestingly, first characterized as an AR coactivator in luciferase assays, ART-27 functions as corepressor for endogenous AR target genes. Importantly, the growth inhibitions by these nuclear proteins are androgen-dependent processes and the regulation of invasion is androgen-independent. Understanding the molecular switches involved in the transition from AR dependent growth promotion to growth suppression and dysregulation of these coactivator proteins promoting androgen-independent invasion may lead to identification of novel therapeutic targets for PCa.