Metastasis-associated protein 1 short form stimulates Wnt1 pathway in mammary epithelial and cancer cells

Clinicopathological Significance of MTA 1 Expression in Patients with Non-Small Cell Lung Cancer: A Meta-Analysis

Background:

Metastasis associated gene 1(MTA1) is one of the most deregulated molecules in human cancer and leads to cancer progression and metastasis. We performed a meta-analysis to determine the correlations between MTA1 expression and the clinicopathological characteristics of non-small cell lung cancer (NSCLC).

Methods:

We searched PubMed, Springer, Science Direct, Google Scholar and China National Knowledge Infrastructure (CNKI) for relevant articles. For statistical analyses, we used R3.1.1 software. The fixed or random effects model was employed based on the results of the statistical test for homogeneity.

Results:

Seven studies involving 660 NSCLC patients were included. The proportion of MTA1 overexpression with 95% confidence interval (95% CI) was 0.53(95% CI: 0.43-0.62) in NSCLC patients; 0.47(95% CI: 0.40-0.55) in age <60 years and 0.52(95% CI: 0.34-0.70) in age ≥60 years; 0.5(95% CI: 0.41-0.62) in males and 0.51(95% CI: 0.39-0.62) in females; 0.59(95% CI: 0.48-0.69) in squamous cell carcinoma (SC) and 0.57(95% CI: 0.46-0.67) in adenocarcinoma (AC); 0.39(95% CI: 0.23-0.56) in well-differentiated tumors, 0.44(95% CI: 0.37-0.51) in moderately differentiated tumors and 0.55(95% CI: 0.37-0.51) in poorly differentiated tumors; 0.48(95% CI: 0.36-0.60) in clinical grade (III-IV) NSCLC and 0.75 (95% CI: 0.69-0.81) in clinical grade (I-II) NSCLC; 0.58(95% CI: 0.45-0.71) in T Stage (T1/T2) NSCLC; 0.68(95% CI: 0.49-0.82) in NSCLC patients with lymph node positivity and 0.51(95% CI: 0.43-0.58) in NSCLC patients with lymph node negativity.

Conclusions:

These results indicated that MTA1 might be a valuable biomarker in the diagnosis of NSCLC. MTA1 overexpression was significantly associated with age ≥60 years, gender, histopathological type, clinical grade (I-II), T stage (T1/T2) and lymph node positivity in NSCLC patients.

High Prevalence and Clinical Relevance of Genes Affected by Chromosomal Breaks in Colorectal Cancer

Background

Cancer is caused by somatic DNA alterations such as gene point mutations, DNA copy number aberrations (CNA) and structural variants (SVs). Genome-wide analyses of SVs in large sample series with well-documented clinical information are still scarce. Consequently, the impact of SVs on carcinogenesis and patient outcome remains poorly understood. This study aimed to perform a systematic analysis of genes that are affected by CNA-associated chromosomal breaks in colorectal cancer (CRC) and to determine the clinical relevance of recurrent breakpoint genes.

Methods

Primary CRC samples of patients with metastatic disease from CAIRO and CAIRO2 clinical trials were previously characterized by array-comparative genomic hybridization. These data were now used to determine the prevalence of CNA-associated chromosomal breaks within genes across 352 CRC samples. In addition, mutation status of the commonly affected APC, TP53, KRAS, PIK3CA, FBXW7, SMAD4, BRAF and NRAS genes was determined for 204 CRC samples by targeted massive parallel sequencing. Clinical relevance was assessed upon stratification of patients based on gene mutations and gene breakpoints that were observed in >3% of CRC cases.

Results

In total, 748 genes were identified that were recurrently affected by chromosomal breaks (FDR <0.1). MACROD2 was affected in 41% of CRC samples and another 169 genes showed breakpoints in >3% of cases, indicating that prevalence of gene breakpoints is comparable to the prevalence of well-known gene point mutations. Patient stratification based on gene breakpoints and point mutations revealed one CRC subtype with very poor prognosis.

Conclusions

We conclude that CNA-associated chromosomal breaks within genes represent a highly prevalent and clinically relevant subset of SVs in CRC.

Unravelling the Complexity and Functions of MTA Coregulators in Human Cancer

Since the initial recognition of the metastasis-associated protein 1 (MTA1) as a metastasis-relevant gene approximately 20 years ago, our appreciation for the complex role of the MTA family of coregulatory proteins in human cancer has profoundly grown. MTA proteins consist of six family members with similar structural units and act as central signaling nodes for integrating upstream signals into regulatory chromatin-remodeling networks, leading to regulation of gene expression in cancer cells. Substantial experimental and clinical evidence demonstrates that MTA proteins, particularly MTA1, are frequently deregulated in a wide range of human cancers. The MTA family governs cell survival, the invasive and metastatic phenotypes of cancer cells, and the aggressiveness of cancer and the prognosis of patients with MTA1 overexpressing cancers. Our discussion here highlights our current understanding of the regulatory mechanisms and functional roles of MTA proteins in cancer progression and expands upon the potential implications of MTA proteins in cancer biology and cancer therapeutics.

ATP-dependent chromatin remodeling complexes as novel targets for cancer therapy

The progression to advanced stage cancer requires changes in many characteristics of a cell. These changes are usually initiated through spontaneous mutation. As a result of these mutations, gene expression is almost invariably altered allowing the cell to acquire tumor-promoting characteristics. These abnormal gene expression patterns are in part enabled by the posttranslational modification and remodeling of nucleosomes in chromatin. These chromatin modifications are established by a functionally diverse family of enzymes including histone and DNA-modifying complexes, histone deposition pathways, and chromatin remodeling complexes. Because the modifications these enzymes deposit are essential for maintaining tumor-promoting gene expression, they have recently attracted much interest as novel therapeutic targets. One class of enzyme that has not generated much interest is the chromatin remodeling complexes. In this review, we will present evidence from the literature that these enzymes have both causal and enabling roles in the transition to advanced stage cancers; as such, they should be seriously considered as high-value therapeutic targets. Previously published strategies for discovering small molecule regulators to these complexes are described. We close with thoughts on future research, the field should perform to further develop this potentially novel class of therapeutic target.

Significance of MTA1 in the molecular characterization of osteosarcoma

Osteosarcoma is the most common malignant bone tumor in children and characterized by aggressive biologic behavior of metastatic propensity to the lung. Change of treatment paradigm brings survival benefit; however, 5-year survival rate is still low in patients having metastastatic foci at diagnosis for a few decades. Metastasis-associated protein (MTA) family is a group of ubiquitously expressed coregulators, which influences on tumor invasiveness or metastasis. MTA1 has been investigated in various cancers including osteosarcoma, and its overexpression is associated with high-risk features of cancers. In this review, we described various molecular studies of osteosarcoma, especially associated with MTA1.

Expression of MTA1 in nasopharyngeal carcinoma and its correlation with prognosis

Metastasis-associated protein 1 (MTA1) is related to tumour metastasis and poor prognosis in various human cancers. The aim of this study was to investigate the expression of MTA1 in nasopharyngeal carcinoma (NPC) and explore the prognostic value of MTA1 in NPC patients. The expression of MTA1 in 136 human NPC tissues and 20 normal nasopharyngeal tissues was detected using immunohistochemistry, quantified and classified into low or high expression using a 50% cut-off level. The relationships of MTA1 expression with the clinical characteristics and survival of patients were analysed. MTA1-positive staining was observed in the nuclei of NPC cells, and MTA1 expression was significantly correlated with T stage (P = 0.006), clinical stage (P = 0.001) and distant metastasis (P < 0.001). Patients with high MTA1 expression exhibited significantly worse distant metastasis-free survival (DMFS) than those with low MTA1 expression (90.75% vs. 70.81%, P = 0.017). Multivariate survival analysis revealed that MTA1 expression was an independent prognostic factor for DMFS (P = 0.038). In this study, high MTA1 expression was significantly associated with poor DMFS in NPC, indicating that MTA1 could serve as a novel biomarker for assessing the metastatic potential of NPC and could act as a possible therapeutic target for the treatment of metastatic nasopharyngeal carcinoma.

Role of MTA1 in cancer progression and metastasis

The MTA1 protein contributes to the process of cancer progression and metastasis through multiple genes and protein targets and interacting proteins with roles in transformation, anchorage-independent growth, invasion, survival, DNA repair, angiogenesis, hormone independence, metastasis, and therapeutic resistance. Because the roles and clinical significance of MTA proteins in human cancer are discussed by other contributors in this issue, this review will focus on our current understanding of the underlying principles of action behind the biological effects of MTA1. MTA proteins control a spectrum of cancer-promoting processes by modulating the expression of target genes and/or the activity of MTA-interacting proteins. In the case of MTA1, these functions are manifested through posttranslational modifications of MTA1 in response to upstream signals, MTA1 interaction with binding proteins, and the expression of target gene products. Studies delineating the molecular basis of dual functionality of MTA1 reveal that the functions of MTA1-chromatin-modifying complexes in the context of target gene regulation are dynamic in nature. The nature and targets of MTA1-chromatin-modifying complexes are also governed by the dynamic plasticity of the nucleosome landscape as well as kinetics of activation and inactivation of enzymes responsible for posttranslational modifications on the MTA1 protein. These broadly applicable functions also explain why MTA1 may be a "hub" gene in cancer. Because the deregulation of enzymes and their substrates with roles in MTA1 biology is not necessarily limited to cancer, we speculate that the lessons from MTA1 as a prototype dual master coregulator will be relevant for other human diseases. In this context, the concept of the dynamic nature of corepressor versus coactivator complexes and the MTA1 proteome as a function of time to signal is likely to be generally applicable to other multiprotein regulatory complexes in living systems.

Subcellular localization of MTA proteins in normal and cancer cells

The subcellular localization of a protein is closely linked to and indicates its function. The metastatic tumor antigen (MTA) family has been under continuous investigation since its identification two decades ago. MTA1, MTA2, and MTA3 are the main members of the MTA family. MTA1, as the representative member of this family, has been shown to be widely expressed in both embryonic and adult tissues, as well as in normal and cancerous conditions, indicating that MTA1 has functions both in physiological and pathological contexts. MTA1 is expressed at a higher level in most cancers than in their normal tissue counterparts. Even in normal cells, MTA1 levels vary a great deal from tissue to tissue. Importantly, MTA1 shows a multiple localization pattern in the cell, as do MTA2 and MTA3. Different MTA components in different subcellular compartments may exert different molecular functions in the cell. Previous studies revealed that MTA1 and MTA2 are predominately localized to the nucleus, while MTA3 is observed in both the nucleus and cytoplasm. Recent studies have reported that MTA1 is located in the nucleus, cytoplasm, and the nuclear envelope. In the nucleus, MTA1 dynamically interacts with chromatin in a MTA1-K532 methylation-dependent manner, whereas cytoplasmic MTA1 binds to the microtubule skeleton. MTA1 also shows a dynamic distribution during the cell cycle. Further investigations are needed to identify the exact subcellular localizations of MTA proteins. We review the sub-cellular localization patterns of the MTA family members and give a comprehensive overview of their respective molecular activities in multiple contexts.

Epstein-Barr virus-encoded latent membrane protein 2A promotes the epithelial-mesenchymal transition in nasopharyngeal carcinoma via metastatic tumor antigen 1 and mechanistic target of rapamycin signaling induction

Epstein-Barr virus-encoded latent membrane protein 2A (LMP2A) promotes the epithelial-mesenchymal transition (EMT) of nasopharyngeal carcinoma (NPC), thereby increasing tumor invasion. Recently, the dysregulation of metastatic tumor antigen 1 (MTA1) was found to enhance tumor metastasis in a variety of cancers. A molecular connection between these two proteins has been proposed but not firmly established. In this study, we reported the overexpression of MTA1 in 29/60 (48.3%) NPC patients, and the overexpression of MTA1 significantly correlated with tumor metastasis. The overexpression of MTA1 promoted EMT via the Wnt1 pathway and β-catenin activation. We demonstrated that LMP2A reinforces the expression of MTA1 via the mechanistic target of rapamycin (mTOR) pathway to promote EMT in NPC. Furthermore, by knocking down 4EBP1 in combination with the new mTOR inhibitor INK-128 treatment, we discovered that LMP2A expression activates the 4EBP1-eIF4E axis and increases the expression of MTA1 at the translational level partially independent of c-myc. These findings provided novel insights into the correlation between the LMP2A and MTA1 proteins and reveal a novel function of the 4EBP1-eIF4E axis in EMT of nasopharyngeal carcinoma. Importance: Prevention of the recurrence and metastasis of NPC is critical to achieving a successful NPC treatment. As we all know, EMT has a vital role in metastasis of malignancies. LMP2A, an oncoprotein of Epstein-Barr virus, a well-known NPC activator, induces EMT and has been proved to exert a promoting effect in tumor metastasis. Our study demonstrated that LMP2A could induce EMT by activating MTA1 at the translational level via activating mTOR signaling and the 4EBP1-eIF4E axis. Taken together, our findings bridge the gap between the NPC-specific cell surface molecule and the final phenotype of the NPC cells. Additionally, our findings indicate that LMP2A and mTOR will serve as targets for NPC therapy in the future.

MTA1 overexpression induces cisplatin resistance in nasopharyngeal carcinoma by promoting cancer stem cells properties

Themetastasis-associated gene 1 (MTA1) oncogene hasbeen suggested to be involved in the regulation of cancer progression. However, there is still no direct evidence that MTA1 regulates cisplatin (CDDP) resistance, as well as cancer stem cell properties. In this study, we found that MTA1 was enriched in CNE1/CDDP cells. Knock down of MTA1 in CNE1/CDDP cells reversed CSCs properties and CDDP resistance. However, ectopic expression of MTA1 in CNE1 cells induced CSCs phenotypes and CDDP insensitivity. Interestingly, ectopic overexpression of MTA1-induced CSCs properties and CDDP resistance were reversed in CNE1 cells after inhibition of PI3K/Akt by LY294002. In addition, MTA1 expression and Akt activity in CNE1/CDDP cells was much higher than that in CNE1 cells. These results suggested that MTA1 may play a critical role in promoting CDDP resistance in NPC cells by regulatingcancer stem cell properties via thePI3K/Akt signaling pathway. Our findings suggested that MTA1 may be a potential target for overcoming CDDP resistance in NPC therapy.

Estrogen receptor coregulators and pioneer factors: the orchestrators of mammary gland cell fate and development

The steroid hormone, 17β-estradiol (E2), plays critical role in various cellular processes such as cell proliferation, differentiation, migration and apoptosis, and is essential for reproduction and mammary gland development. E2 actions are mediated by two classical nuclear hormone receptors, estrogen receptor α and β (ERs). The activity of ERs depends on the coordinated activity of ligand binding, post-translational modifications (PTMs), and importantly the interaction with their partner proteins called “coregulators.” Because coregulators are proved to be crucial for ER transcriptional activity, and majority of breast cancers are ERα positive, an increased interest in the field has led to the identification of a large number of coregulators. In the last decade, gene knockout studies using mouse models provided impetus to our further understanding of the role of these coregulators in mammary gland development. Several coregulators appear to be critical for terminal end bud (TEB) formation, ductal branching and alveologenesis during mammary gland development. The emerging studies support that, coregulators along with the other ER partner proteins called “pioneer factors” together contribute significantly to E2 signaling and mammary cell fate. This review discusses emerging themes in coregulator and pioneer factor mediated action on ER functions, in particular their role in mammary gland cell fate and development.

MTA1 contributes to actin cytoskeleton reorganization and metastasis of nasopharyngeal carcinoma by modulating Rho GTPases and Hedgehog signaling

Nasopharyngeal carcinoma (NPC) is prone to appearing regional lymph node and distant metastasis. And its underlying mechanism is unclear. Recent study suggests that overexpression of metastasis-associated gene 1 (MTA1) was independently associated with poorer distant metastasis-free survival in NPC. However, it is still lack of direct evidence that MTA1 is responsible for aggressive phenotypes of NPC. Using stably transfected MTA1 knockdown or overexpression cells, we discovered the function of MTA1 in actin cytoskeleton reorganization and metastasis processing of NPC in this study. For the first time, our data demonstrate two tumor relevant molecular mechanisms, i.e. Rho GTPases and Hedgehog signaling both contribute to the effect of MTA1 on the aggressive phenotypes of NPC cells. In summary, the novel findings in this work provide further insight into the function of MTA1 and the molecular mechanism in the progression of NPC. Our results indicate that MTA1 might serve as a potential therapeutic target for advanced NPC.

Identification and characterization of a small-molecule inhibitor of Wnt signaling in glioblastoma cells

Glioblastoma multiforme (GBM) is the most common and prognostically unfavorable form of brain tumor. The aggressive and highly invasive phenotype of these tumors makes them among the most anatomically damaging human cancers with a median survival of less than 1 year. Although canonical Wnt pathway activation in cancers has been historically linked to the presence of mutations involving key components of the pathway (APC, β-catenin, or Axin proteins), an increasing number of studies suggest that elevated Wnt signaling in GBM is initiated by several alternative mechanisms that are involved in different steps of the disease. Therefore, inhibition of Wnt signaling may represent a therapeutically relevant approach for GBM treatment. After the selection of a GBM cell model responsive to Wnt inhibition, we set out to develop a screening approach for the identification of compounds capable of modulating canonical Wnt signaling and associated proliferative responses in GBM cells. Here, we show that the small molecule SEN461 inhibits the canonical Wnt signaling pathway in GBM cells, with relevant effects at both molecular and phenotypic levels in vitro and in vivo. These include SEN461-induced Axin stabilization, increased β-catenin phosphorylation/degradation, and inhibition of anchorage-independent growth of human GBM cell lines and patient-derived primary tumor cells in vitro. Moreover, in vivo administration of SEN461 antagonized Wnt signaling in Xenopus embryos and reduced tumor growth in a GBM xenograft model. These data represent the first demonstration that small-molecule-mediated inhibition of Wnt signaling may be a potential approach for GBM therapeutics.

MTA1 promotes STAT3 transcription and pulmonary metastasis in breast cancer

Overexpression of the prometastatic chromatin modifier protein metastasis tumor antigen 1 (MTA1) in human cancer contributes to tumor aggressiveness, but the role of endogenous MTA1 in cancer has not been explored. Here, we report the effects of selective genetic depletion of MTA1 in a physiologically relevant spontaneous mouse model of breast cancer pulmonary metastasis. We found that MTA1 acts as a mandatory modifier of breast-to-lung metastasis without effects on primary tumor formation. The underlying mechanism involved MTA1-dependent stimulation of STAT3 transcription through action on the MTA1/STAT3/Pol II coactivator complex, and, in turn, on the expression and functions of STAT3 target genes including Twist1. Accordingly, we documented a positive correlation between levels of MTA1 and STAT3 in publicly available breast cancer data sets. Together, our findings reveal an essential modifying role of the physiologic level of MTA1 in supporting pulmonary metastasis of breast cancer.

MTA1-mediated transcriptional repression of SMAD7 in breast cancer cell lines

Metastasis is a complex process facilitated by the action of several genes. Metastasis associated 1 (MTA1) gene is one such gene which assists the process of metastasis by regulating several molecular targets. MTA1 acts as part of a nucleosome remodelling and histone deacetylation complex, which is involved in transcriptional regulation. Expression of MTA1 has been shown to be closely correlated with aggressiveness in several types of cancers, including breast cancer. In the present study we show that MTA1 regulates SMAD7, a component of Transforming growth factor beta (TGFbeta) signalling. TGFbeta signals are transduced to the nucleus by the Smad family of proteins, which includes Smad7, an inhibitory SMAD, which acts as a negative regulator of TGFbeta. On knockdown of MTA1, SMAD7 expression increases. Treating cells with a histone deacetylase inhibitor also increases SMAD7 expression. MTA1 is recruited to SMAD7 promoter region. SMAD7 inhibits activation of SMAD2 and SMAD3 and we show that the levels of these active SMAD proteins are decreased in cells expressing shRNA against MTA1. We further show that on MTA1 knockdown, the expression of downstream targets of SMAD7 is decreased. MTA1 thus appears to regulate a key inhibitor of TGFbeta signalling, SMAD7. By regulating molecules like SMAD7 MTA1 might assist the process of tumourigenesis and metastasis.

Leptin-induced epithelial-mesenchymal transition in breast cancer cells requires β-catenin activation via Akt/GSK3- and MTA1/Wnt1 protein-dependent pathways

Perturbations in the adipocytokine profile, especially higher levels of leptin, are a major cause of breast tumor progression and metastasis; the underlying mechanisms, however, are not well understood. In particular, it remains elusive whether leptin is involved in epithelial-mesenchymal transition (EMT). Here, we provide molecular evidence that leptin induces breast cancer cells to undergo a transition from epithelial to spindle-like mesenchymal morphology. Investigating the downstream mediator(s) that may direct leptin-induced EMT, we found functional interactions between leptin, metastasis-associated protein 1 (MTA1), and Wnt1 signaling components. Leptin increases accumulation and nuclear translocation of β-catenin leading to increased promoter recruitment. Silencing of β-catenin or treatment with the small molecule inhibitor, ICG-001, inhibits leptin-induced EMT, invasion, and tumorsphere formation. Mechanistically, leptin stimulates phosphorylation of glycogen synthase kinase 3β (GSK3β) via Akt activation resulting in a substantial decrease in the formation of the GSK3β-LKB1-Axin complex that leads to increased accumulation of β-catenin. Leptin treatment also increases Wnt1 expression that contributes to GSK3β phosphorylation. Inhibition of Wnt1 abrogates leptin-stimulated GSK3β phosphorylation. We also discovered that leptin increases the expression of an important modifier of Wnt1 signaling, MTA1, which is integral to leptin-mediated regulation of the Wnt/β-catenin pathway as silencing of MTA1 inhibits leptin-induced Wnt1 expression, GSK3β phosphorylation, and β-catenin activation. Furthermore, analysis of leptin-treated breast tumors shows increased expression of Wnt1, pGSK3β, and vimentin along with higher nuclear accumulation of β-catenin and reduced E-cadherin expression providing in vivo evidence for a previously unrecognized cross-talk between leptin and MTA1/Wnt signaling in epithelial-mesenchymal transition of breast cancer cells.

Mechanism of MTA1 protein overexpression-linked invasion: MTA1 regulation of hyaluronan-mediated motility receptor (HMMR) expression and function

Even though the hyaluronan-mediated motility receptor (HMMR), a cell surface oncogenic protein, is widely up-regulated in human cancers and correlates well with cell motility and invasion, the underlying molecular and nature of its putative upstream regulation remain unknown. Here, we found for the first time that MTA1 (metastatic tumor antigen 1), a master chromatin modifier, regulates the expression of HMMR and, consequently, its function in breast cancer cell motility and invasiveness. We recognized a positive correlation between the levels of MTA1 and HMMR in human cancer. Furthermore, MTA1 is required for optimal expression of HMMR. The underlying mechanism includes interaction of the MTA1·RNA polymerase II·c-Jun coactivator complex with the HMMR promoter to stimulates its transcription. Accordingly, selective siRNA-mediated knockdown of HMMR in breast cancer cells substantially reduces the invasion and migration of cells. These findings reveal a regulatory role for MTA1 as an upstream coactivator of HMMR expression and resulting biological phenotypes.

Metastasis-associated protein 1/nucleosome remodeling and histone deacetylase complex in cancer

Cancer cells frequently exhibit deregulation of coregulatory molecules to drive the process of growth and metastasis. One such group of ubiquitously expressed coregulators is the metastasis-associated protein (MTA) family, a critical component of the nucleosome remodeling and histone deacetylase (NuRD) complex. MTA1 occupies a special place in cancer biology because of its dual corepressor or coactivator nature and widespread overexpression in human cancers. Here, we highlight recent advances in our understanding of the vital roles of MTA1 on transformation, epithelial-mesenchymal transition, and the functions of key cancer-relevant molecules such as a nexus of multiple oncogenes and tumor suppressors. In addition to its paramount role in oncogenesis, we reveal several new physiologic functions of MTA1 related to DNA damage, inflammatory responses, and infection, in which MTA1 functions as a permissive "gate keeper" for cancer-causing parasites. Further, these discoveries unraveled the versatile multidimensional modes of action of MTA1, which are independent of the NuRD complex and/or transcription. Given the emerging roles of MTA1 in DNA repair, inflammation, and parasitism, we discuss the possibility of MTA1-targeted therapy for use not only in combating cancer but also in other inflammation and pathogen-driven pathologic conditions.

The anti-progestin RU-486 inhibits viability of MCF-7 breast cancer cells by suppressing WNT1

The Wnt signaling pathway is activated in over 50% of women with breast cancer and contributes to tumor progression. Here, we investigated the effects of RU-486 on Wnt signaling in breast cancer cell lines. RU-486 reduced viability of the progesterone receptor-positive MCF-7 and T-47D cells, but had no effect on the triple-negative MDA-MB-231 cells. Furthermore, RU-486 suppressed WNT1 expression of MCF-7 cells by 99%. The addition of recombinant WNT1 partially reversed the RU-486-dependent inhibition of viability in MCF-7, but not in T-47D cells. In conclusion, we identified WNT1 as a novel mediator of the anti-tumor effects of RU-486 in MCF-7 cells.

The Expanding Mi-2/NuRD Complexes: A Schematic Glance

This mini-review will schematically update the progress of the expanding Mi-2/Nucleosome Remodeling Deacetylase (NuRD) complexes in cancer and in normal development such as stemness, with a focus on mammals and the increasingly popular and powerful model organism Caenorhabditis elegans. The Mi-2/NuRD complexes control gene activity during the development of complex organisms. Every Mi-2/NuRD complex contains many different core polypeptides, which form distinct multifunctional complexes with specific context-dependent regulators. The Mi-2/NuRD complexes have unique ATP-dependent chromatin remodeling, histone deacetylase, demethylase activities and higher order chromatin organization. They can regulate the accessibility of transcription factors or repair proteins to DNA. In this review, we summarize our current knowleges in the composition, interaction and function of the subunits within the Mi-2/NuRD complex, the methodology used for the identification of Mi-2/NuRD complexes, as well as the clinical and therapeutic implications targeting the Mi-2/NuRD subunits.

Manganese induces tau hyperphosphorylation through the activation of ERK MAPK pathway in PC12 cells

Manganese has long been known to induce neurological degenerative disorders. Emerging evidence indicates that hyperphosphorylated tau is associated with neurodegenerative diseases, but whether such hyperphosphorylation plays a role in manganese-induced neurotoxicity remains unclear. To fill this gap, we investigated the effects of manganese on tau phosphorylation in PC12 cells. In our present research, treatment of cells with manganese increased the phosphorylation of tau at Ser199, Ser202, Ser396, and Ser404 as detected by Western blot. Moreover, this manganese-induced tau phosphorylation paralleled the activation of extracellular signal-regulated kinase (ERK) mitogen-activated protein kinase (MAPK). The mitogen-activated protein kinase kinase-1 (MEK1) inhibitor PD98059, which inhibits the activation of ERK MAPK, partially attenuated manganese-induced tau hyperphosphorylation and cytotoxicity. Moreover, the activation of ERK MAPK was involved in the activation of glycogen synthase kinase-3β (GSK-3β) kinase, which also contributed to the hyperphosphorylation of tau and the cytotoxicity in PC12 cells induced by manganese. Taken together, we found for the first time that the exposure to manganese can cause the hyperphosphorylation of tau, which may be connected with the activation of ERK MAPK.

Metastasis-associated protein 1 and its short form variant stimulates Wnt1 transcription through promoting its derepression from Six3 corepressor

Although Wnt1 downstream signaling components have been well studied and activated in human cancer, the pathways that regulate Wnt1 itself have not been explored in depth. Here, we provide gain-of-function, loss-of function, and molecular evidence supporting functional interactions between metastasis-associated protein 1 short-form (MTA1s), metastasis-associated protein 1 (MTA1), and Wnt1 signaling components during mammary gland development and tumorigenesis. Using multiple model systems involving overexpression or knockdown of MTA1s or MTA1, we discovered that MTA1s and MTA1 hyperactivate the Wnt1 pathway due to increased expression of Wnt1 transcription. MTA1s and MTA1 physically interact with Six3 chromatin, a protein product of which is a direct histone deacetylase inhibitor-dependent repressor of Wnt1 transcription. Deletion of the MTA1s and MTA1 allele in murine embryonic fibroblasts resulted in the upregulation of Six3 and downregulation of Wnt signaling. In addition, mammary glands from the MTA1s/MTA1(-/-) mice exhibited increased recruitment of Six3 corepressor complex to the Wnt1 promoter and inhibition of Wnt1 pathway in mammary glands. These findings identify MTA1s and MTA1 as important upstream modifiers of the Wnt1 transcription, and consequently its functions, by directly inhibiting the transcription of Six3, allowing derepression of Wnt1 transcription.