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

PHF14 enhances DNA methylation of SMAD7 gene to promote TGF-β-driven lung adenocarcinoma metastasis

Aberrant activation of TGF-β signaling plays a pivotal role in cancer metastasis and progression. However, molecular mechanisms underlying the dysregulation of TGF-β pathway remain to be understood. Here, we found that SMAD7, a direct downstream transcriptional target and also a key antagonist of TGF-β signaling, is transcriptionally suppressed in lung adenocarcinoma (LAD) due to DNA hypermethylation. We further identified that PHF14 binds DNMT3B and serves as a DNA CpG motif reader, recruiting DNMT3B to the SMAD7 gene locus, resulting in DNA methylation and transcriptional suppression of SMAD7. Our in vitro and in vivo experiments showed that PHF14 promotes metastasis through binding DNMT3B to suppress SMAD7 expression. Moreover, our data revealed that PHF14 expression correlates with lowered SMAD7 level and shorter survival of LAD patients, and importantly that SMAD7 methylation level of circulating tumor DNA (ctDNA) can potentially be used for prognosis prediction. Together, our present study illustrates a new epigenetic mechanism, mediated by PHF14 and DNMT3B, in the regulation of SMAD7 transcription and TGF-β-driven LAD metastasis, and suggests potential opportunities for LAD prognosis.

RUNX2 recruits the NuRD(MTA1)/CRL4B complex to promote breast cancer progression and bone metastasis

Runt-related transcription factor 2 (RUNX2) is an osteogenesis-related transcription factor that has emerged as a prominent transcription repressing factor in carcinogenesis. However, the role of RUNX2 in breast cancer metastasis remains poorly understood. Here, we show that RUNX2 recruits the metastasis-associated 1 (MTA1)/NuRD and the Cullin 4B (CUL4B)-Ring E3 ligase (CRL4B) complex to form a transcriptional-repressive complex, which catalyzes the histone deacetylation and ubiquitylation. Genome-wide analysis of the RUNX2/NuRD(MTA1)/CRL4B complex targets identified a cohort of genes including peroxisome proliferator-activated receptor alpha (PPARα) and superoxide dismutase 2 (SOD2), which are critically involved in cell growth, epithelial-to-mesenchymal transition (EMT) and invasion. We demonstrate that the RUNX2/NuRD(MTA1)/CRL4B complex promotes the proliferation, invasion, tumorigenesis, bone metastasis, cancer stemness of breast cancer in vitro and in vivo. Strikingly, RUNX2 expression is upregulated in multiple human carcinomas, including breast cancer. Our study suggests that RUNX2 is a promising potential target for the future treatment strategies of breast cancer.

MTA1-TJP1 interaction and its involvement in non-small cell lung cancer metastasis

•

MTA1 was highly expressed in NSCLC tissues and was associated with tumor progression.

•

MTA1 promoted NSCLC cell invasion and migration in vitro and in vivo.

•

TJP1 was found to be an interacting protein of MTA1 involved in cell adhesion.

•

MTA1 promoted NSCLC invasion and metastasis by inhibiting TJP1 protein expression and attenuating intercellular tight junctions.

•

Targeting the MTA1-TJP1 axis may be a promising strategy for inhibiting NSCLC metastasis.

Distant metastasis is the main cause of death in non-small cell lung cancer (NSCLC) patients. The mechanism of metastasis-associated protein 1(MTA1) in NSCLC has not been fully elucidated. This study aimed to reveal the mechanism of MTA1 in the invasion and metastasis of NSCLC.

Bioinformatics analysis and our previous results showed that MTA1 was highly expressed in NSCLC tissues and correlated with tumor progression. Knockout of MTA1 by CRISPR/Cas9 significantly inhibited the migration and invasion of H1299 cells, but enhanced cell adhesion. Stable overexpression of MTA1 by lentivirus transfection had opposite effects on migration, invasion and adhesion of A549 cells. The results of in vivo experiments in nude mouse lung metastases model confirmed the promotion of MTA1 on invasion and migration. Tight junction protein 1 (TJP1) was identified by immunoprecipitation and mass spectrometry as an interacting protein of MTA1 involved in cell adhesion. MTA1 inhibited the expression level of TJP1 protein and weakened the tight junctions between cells. More importantly, the rescue assays confirmed that the regulation of MTA1 on cell adhesion, migration and invasion was partially attenuated by TJP1.

In Conclusion, MTA1 inhibits the expression level of TJP1 protein co-localized in the cytoplasm and membrane of NSCLC cells, weakens the tight junctions between cells, and changes the adhesion, migration and invasion capabilities of cells, which may be the mechanism of MTA1 promoting the invasion and metastasis of NSCLC. Thus, targeting the MTA1-TJP1 axis may be a promising strategy for inhibiting NSCLC metastasis.

Sulforaphane Enhanced Proliferation of Porcine Satellite Cells via Epigenetic Augmentation of SMAD7

Satellite cells take an indispensable place in skeletal muscle regeneration, maintenance, and growth. However, only limited works have investigated effects of dietary compounds on the proliferation of porcine satellite cells (PSCs) and related mechanisms. Sulforaphane (SFN) at multiple levels was applied to PSCs. The PSCs’ viability and HDAC activity were measured with a WST-1 cell proliferation kit and Color-de-Lys® HDAC colorimetric activity assay kit. Gene expression and epigenetics modification were tested with qRT-PCR, Western blot, bisulfite sequencing, and ChIP-qPCR. This study found that SFN enhanced PSC proliferation and altered mRNA expression levels of myogenic regulatory factors. In addition, SFN inhibited histone deacetylase (HDAC) activity, disturbed mRNA levels of HDAC family members, and elevated acetylated histone H3 and H4 abundance in PSCs. Furthermore, both mRNA and protein levels of the Smad family member 7 (SMAD7) in PSCs were upregulated after SFN treatment. Finally, it was found that SFN increased the acetylation level of histone H4 in the SMAD7 promoter, decreased the expression of microRNAs, including ssc-miR-15a, ssc-miR-15b, ssc-miR-92a, ssc-miR-17-5p, ssc-miR-20a-5p, and ssc-miR-106a, targeting SMAD7, but did not impact on the SMAD7 promoter’s methylation status in PSCs. In summary, SFN was found to boost PSC proliferation and epigenetically increase porcine SMAD7 expression, which indicates a potential application of SFN in modulation of skeletal muscle growth.

Metastasis-associated protein 1-mediated antitumor and anticancer activity of dietary stilbenes for prostate cancer chemoprevention and therapy

Dietary bioactive polyphenols that demonstrate beneficial biological functions including antioxidant, anti-inflammatory, and anticancer activity hold immense promise as effective and safe chemopreventive and chemosensitizing natural anticancer agents. The underlying molecular mechanisms of polyphenols' multiple effects are complex and these molecules are considered promising targets for chemoprevention and therapy. However, the development of novel personalized targeted chemopreventive and therapeutic strategies is essential for successful therapeutic outcomes. In this review, we highlight the potential of metastasis-associated protein 1 (MTA1)-targeted anticancer and antitumor effects of three dietary stilbenes, namely resveratrol, pterostilbene, and gnetin C, for prostate cancer management. MTA1, an epigenetic reader and master transcriptional regulator, plays a key role in all stages of prostate cancer progression and metastasis. Stilbenes inhibit MTA1 expression, disrupt the MTA1/histone deacetylase complex, modulate MTA1-associated Epi-miRNAs and reduce MTA1-dependent inflammation, cell survival, and metastasis in prostate cancer in vitro and in vivo. Overall, the MTA1-targeted strategies involving dietary stilbenes may be valuable for effective chemoprevention in selected subpopulations of early stage prostate cancer patients and for combinatorial strategies with conventional chemotherapeutic drugs against advanced metastatic prostate cancer.

The Role of Epigenetic Modifications in Human Cancers and the Use of Natural Compounds as Epidrugs: Mechanistic Pathways and Pharmacodynamic Actions

Cancer is a complex disease resulting from the genetic and epigenetic disruption of normal cells. The mechanistic understanding of the pathways involved in tumor transformation has implicated a priori predominance of epigenetic perturbations and a posteriori genetic instability. In this work, we aimed to explain the mechanistic involvement of epigenetic pathways in the cancer process, as well as the abilities of natural bioactive compounds isolated from medicinal plants (flavonoids, phenolic acids, stilbenes, and ketones) to specifically target the epigenome of tumor cells. The molecular events leading to transformation, angiogenesis, and dissemination are often complex, stochastic, and take turns. On the other hand, the decisive advances in genomics, epigenomics, transcriptomics, and proteomics have allowed, in recent years, for the mechanistic decryption of the molecular pathways of the cancerization process. This could explain the possibility of specifically targeting this or that mechanism leading to cancerization. With the plasticity and flexibility of epigenetic modifications, some studies have started the pharmacological screening of natural substances against different epigenetic pathways (DNA methylation, histone acetylation, histone methylation, and chromatin remodeling) to restore the cellular memory lost during tumor transformation. These substances can inhibit DNMTs, modify chromatin remodeling, and adjust histone modifications in favor of pre-established cell identity by the differentiation program. Epidrugs are molecules that target the epigenome program and can therefore restore cell memory in cancerous diseases. Natural products isolated from medicinal plants such as flavonoids and phenolic acids have shown their ability to exhibit several actions on epigenetic modifiers, such as the inhibition of DNMT, HMT, and HAT. The mechanisms of these substances are specific and pleiotropic and can sometimes be stochastic, and their use as anticancer epidrugs is currently a remarkable avenue in the fight against human cancers.

TGF-β-MTA1-SMAD7-SMAD3-SOX4-EZH2 Signaling Axis Promotes Viability, Migration, Invasion and EMT of Hepatocellular Carcinoma Cells

Introduction

Enhancer of zeste homolog 2 (EZH2) is implicated in hepatocellular carcinoma (HCC), but whether transforming growth factor-β (TGF-β)-metastasis associated 1 (MTA1)-SMAD7-SMAD3-SRY-Box Transcription Factor 4 (SOX4)-EZH2 signaling axis, in which EZH2 participates, is also involved in HCC remained unknown.

Methods

Data on EZH2 expression in liver hepatocellular carcinoma (LIHC) and its relation with prognosis of HCC patients were predicted and analyzed using online databases. Following transfection with or without TGF-β1, HCC cell viability, migration and invasion were determined with MTT, Scratch and Transwell assays. Relative expressions of epithelial-to-mesenchymal transition (EMT)-related factors (N-Cadherin, Vimentin, and E-Cadherin) and TGF-β-MTA1-SMAD7-SMAD3-SOX4-EZH2 signaling axis factors (TGF-β, MTA1, SMAD7, phosphorylated-SMAD3, SOX4 and EZH2) were calculated via reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and Western blot.

Results

EZH2 was upregulated in HCC, which was related to poor prognosis. Silencing EZH2 suppressed EZH2 expression and HCC cell viability, migration, and invasion, and increased E-Cadherin expression yet decreased N-Cadherin and Vimentin expression, whereas EZH2 overexpression did conversely. Also, silencing EZH2 reversed the effects of TGF-β1 on promoting viability, migration, and invasion, as well as N-Cadherin and Vimentin expressions, yet suppressing E-Cadherin expression in HCC cells. In addition, TGF-β1 promoted TGF-β, MTA1, SOX4 and EZH2 expressions and p-SMAD3/SMAD3 ratio yet suppressed SMAD7, whereas silencing EZH2 solely reversed the effects of TGF-β1 on EZH2 expression in HCC cells.

Conclusion

The present study provides a theoretical basis for TGF-β-MTA1-SMAD7-SMAD3-SOX4-EZH2 signaling cascade in viability, migration, invasion, and EMT of HCC cells. Inhibiting these signals may represent a therapeutic pathway for the treatment of metastatic HCC.

Expression and function of Smad7 in autoimmune and inflammatory diseases

Transforming growth factor-β (TGF-β) plays a critical role in the pathological processes of various diseases. However, the signaling mechanism of TGF-β in the pathological response remains largely unclear. In this review, we discuss advances in research of Smad7, a member of the I-Smads family and a negative regulator of TGF-β signaling, and mainly review the expression and its function in diseases. Smad7 inhibits the activation of the NF-κB and TGF-β signaling pathways and plays a pivotal role in the prevention and treatment of various diseases. Specifically, Smad7 can not only attenuate growth inhibition, fibrosis, apoptosis, inflammation, and inflammatory T cell differentiation, but also promotes epithelial cells migration or disease development. In this review, we aim to summarize the various biological functions of Smad7 in autoimmune diseases, inflammatory diseases, cancers, and kidney diseases, focusing on the molecular mechanisms of the transcriptional and posttranscriptional regulation of Smad7.

Prognostic and clinical significance of metastasis-associated gene 1 overexpression in solid cancers: A meta-analysis

BACKGROUND

In the past 2 decades, metastasis-associated gene 1 (MTA1) has attracted attention for its close association with cancer progression and its roles in chromatin remodeling processes, making it a central gene in cancer. The present meta-analysis was performed to assess MTA1 expression in solid tumors.

MATERIALS AND METHODS

This analysis identified studies that evaluated the relationship between MTA1 expression and clinical characteristics or prognosis of patients with solid tumors via the PubMed, Cochrane Library, and Embase electronic databases. Fixed-effect and random-effect meta-analytical techniques were used to correlate MTA1 expression with outcome measures. The outcome variables are shown as odds ratio (OR) or hazard ratio (HR) with 95% confidence interval (CI).

RESULTS

Analysis of 40 cohort studies involving 4564 cancer patients revealed a significant association of MTA1 overexpression with tumor patient age (>50 vs. <50 years: combined OR 0.73, 95% CI 0.57-0.94), tumor grade (G3/4 vs. G1/2: combined OR 1.94, 95% CI 1.48-2.53), tumor size (>3 cm vs. <3 cm: combined OR 2.35, 95% CI 1.73-3.19), T stage (T3/4 vs. T1/2: combined OR 2.11, 95% CI 1.74-2.56), lymph node metastasis (yes vs. no: combined OR 2.92, 95% CI 2.26-3.75), distant metastasis (yes vs. no: combined OR 2.26, 95% CI 1.42-3.59), TNM stage (III/IV vs. I/II: combined OR 2.50, 95% CI 1.84-3.38), vascular invasion (yes vs. no: combined OR 2.26, 95% CI 1.92-3.56), and poor overall survival time (HR 1.83; 95% CI: 1.53-2.20; P = .000).

CONCLUSIONS

Our analyses demonstrate that MTA1 was an effective predictor of a worse prognosis in tumor patients. Moreover, MTA1 may play important role in tumor progression and outcome, and targeting MTA1 may be a new strategy for anti-cancer therapy.

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.

Androgen receptor and metastasis-associated protein-1 are frequently expressed in estrogen receptor negative/HER2 positive breast cancer

The prognostic value of androgen receptor (AR) and its related molecules in breast cancer is not well characterized. We retrospectively investigated 120 ER(+) and 120 ER(-) invasive breast cancers of 240 women, who were treated at our institution between January 2008 and December 2009. We excluded in situ, recurrent, metastatic, and bilateral carcinomas as well as non-epithelial lesions. Median follow-up was 74 months. Immunohistochemical assessment of expression of AR and metastasis-associated protein-1 (MTA1) resulted in 59.2 % (n = 142) AR(+) and 36.7 % (n = 88) high MTA1 expressing (MTA1(High)) carcinomas. MTA1(High) tumors were significantly more often ER(-), while AR(+) tumors were significantly more often HER2(+) (p < 0.01). MTA1(High)/ER(-) tumors were more often AR(-)/HER2(-) (p < 0.01). Patients with an AR(+)/ER(+) tumor had better disease-free survival (DFS; p = 0.011). Patients with an ER(-)/MTA1(High) tumor had significantly shorter DFS (p = 0.006) as well as patients with an AR(+)/HER2(+) tumor (p < 0.01). In Cox models, AR expression (HR, 0.248; 95 % CI, 0.086-0.716) and lymph node status (HR, 6.401; 95 % CI, 1.428-28.686) were independent predictors for DFS in ER(+) cancers, whereas AR(+)/HER2(+) expression status (HR, 2.927; 95 % CI, 1.256-6.821) and lymph node status (HR, 2.690; 95 % CI, 1.041-7.840) were independent predictors for DFS in ER(-) cancers. We show that AR might be an additional marker for endocrine responsiveness in ER(+) cancers and suggests that blocking MTA1 might be an effective way to inhibit AR/HER2 signaling in ER(-) breast cancer.

Structure, expression and functions of MTA genes

Metastatic associated proteins (MTA) are integrators of upstream regulatory signals with the ability to act as master coregulators for modifying gene transcriptional activity. The MTA family includes three genes and multiple alternatively spliced variants. The MTA proteins neither have their own enzymatic activity nor have been shown to directly interact with DNA. However, MTA proteins interact with a variety of chromatin remodeling factors and complexes with enzymatic activities for modulating the plasticity of nucleosomes, leading to the repression or derepression of target genes or other extra-nuclear and nucleosome remodeling and histone deacetylase (NuRD)-complex independent activities. The functions of MTA family members are driven by the steady state levels and subcellular localization of MTA proteins, the dynamic nature of modifying signals and enzymes, the structural features and post-translational modification of protein domains, interactions with binding proteins, and the nature of the engaged and resulting features of nucleosomes in the proximity of target genes. In general, MTA1 and MTA2 are the most upregulated genes in human cancer and correlate well with aggressive phenotypes, therapeutic resistance, poor prognosis and ultimately, unfavorable survival of cancer patients. Here we will discuss the structure, expression and functions of the MTA family of genes in the context of cancer cells.

Correlation Between CASC8, SMAD7 Polymorphisms and the Susceptibility to Colorectal Cancer: An Updated Meta-Analysis Based on GWAS Results

Genome-wide association studies (GWASs) and a number of case-control studies have suggested that several single nucleotide polymorphisms (SNPs), rs7837328, rs7014346, rs6983267, rs10505477 on CASC8 gene and rs4939827, rs4464148, rs12953717 on SMAD7 gene are significantly correlated with the susceptibility to colorectal cancer (CRC). For the sake of clarifying the association, a meta-analysis was conducted and population heterogeneity was considered in the study.A total of 34 articles including 90 studies (168,471 cases and 163,223 controls) that evaluated the relationship between the CASC8, SMAD7 genes and the risk of CRC under the allelic model were reviewed. Also subgroup analysis was performed by ethnicity (Caucasian, Asian, and African) and all of the analyses were implemented in R 3.2.1 software.Pooled data from the meta-analysis revealed that the A allele of rs7837328, the A allele of rs7014346, the G allele of rs6983267, the A allele of rs10505477, the T allele of rs4939827, the T of rs4464148, and the T of rs12953717 were significantly associated with an increased risk of CRC under the allelic model. Additionally, subgroup analyses of 6 SNPs by ethnicity (rs4464148 excepted) witnessed that the A allele of rs7837328, the G allele of rs6983267, and the T of rs12953717 were notably associated with an increased risk of CRC among Caucasian and Asian. Furthermore, the A allele of rs7014346, the A allele of rs10505477, and the T allele of rs4939827 were significantly related with an elevated risk of CRC only among Caucasian.Our study suggested that for CASC8 gene, SNP of rs7837328 and rs6983267 are risk factors for CRC among both Caucasian and Asian whereas rs7014346 and rs10505477 are risky gene polymorphisms only among Caucasian. For SMAD7 gene, rs4939827 and rs4464148 are risk factors for CRC among Caucasian whereas rs12953717 could elevate the susceptibility to CRC in both Caucasian and Asian.

MTA1 promotes proliferation and invasion in human gastric cancer cells

Although metastasis-associated protein 1 (MTA1) has been widely linked to tumor metastasis, the relevant mechanisms remain to be elucidated, especially in gastric cancer. The aim of this study was to examine whether the MTA1 gene is associated with the process of proliferation and invasion by regulating several molecular targets in gastric cancer. MTA1 expression in 61 gastric cancer tissue and adjacent noncancerous tissues was analyzed by immunohistochemistry. The prognostic value of MTA1 for overall survival and disease-free survival was determined by Kaplan-Meier estimates, and the significance of differences between curves was evaluated by the log-rank test. Furthermore, overexpression of MTA1 in SGC7901 and BGC823 cells promoted cell cycle progression, cell adhesion, and cell invasion. Our study found that MTA1 is overexpressed in gastric cancers, which contributes to malignant cell growth by facilitating cell cycle progression through upregulation of cyclin D1 and accelerates the migration and invasion of human gastric cancer cells by regulating expression of fibronectin and MMP2/MMP9. Taken together, MTA1 was involved in the pathogenesis of gastric cancer and might be a candidate therapeutic target in gastric cancer.

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.

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.

MTA family of proteins in prostate cancer: biology, significance, and therapeutic opportunities

This review summarizes our current understanding of the role of MTA family members, particularly MTA1, with a special emphasis on prostate cancer. The interest for the role of MTA1 in prostate cancer was boosted from our initial findings of MTA1 as a component of "vicious cycle" and a member of bone metastatic signature. Analysis of human prostate tissues, xenograft and transgenic mouse models of prostate cancer, and prostate cancer cell lines has provided support for the role of MTA1 in advanced disease and its potential role in initial stages of prostate tumor progression. Recent discoveries have highlighted a critical role for MTA1 in inflammation-triggered prostate tumorigenesis, epithelial-to-mesenchymal transition, prostate cancer survival pathways, and site metastasis. Evidence for MTA1 as an upstream negative regulator of tumor suppressor genes such as p53 and PTEN has also emerged. MTA1 is involved in prostate tumor angiogenesis by regulating several pro-angiogenic factors. Evidence for MTA1 as a prognostic marker for aggressive prostate cancer and disease recurrence has been described. Importantly, pharmacological dietary agents, namely resveratrol and its analogs, are potentially applicable to prostate cancer prevention, treatment, and control of cancer progression due to their potent inhibitory effects on MTA proteins.

Esophageal cancer in a family with hamartomatous tumors and germline PTEN frameshift and SMAD7 missense mutations

Germline mutations in the PTEN tumor-suppressor gene cause autosomal-dominant conditions such as Cowden and Bannayan-Riley-Ruvalcaba syndromes with variable presentations, including hamartomatous gastrointestinal tumors, dermatologic abnormalities, neurologic symptoms, and elevated cancer risk. We describe a father and son with extensive hamartomatous gastrointestinal polyposis who both developed early-onset esophageal cancer. Exome sequencing identified a novel germline PTEN frameshift mutation (c.568_569insC, p.V191Sfs*11). In addition, a missense mutation of SMAD7 (c.115G>A, p.G39R) with an allele frequency of 0.3% in the Exome Variant Server was detected in both affected individuals. Fluorescence in situ hybridization for PTEN in the resected esophageal cancer specimen demonstrated no PTEN copy loss in malignant cells; however, results of an immunohistochemical analysis demonstrated a loss of PTEN protein expression. While the risks of many cancers are elevated in the PTEN hamartoma tumor syndromes, association between esophageal adenocarcinoma and these syndromes has not been previously reported. Esophageal adenocarcinoma and extensive polyposis/ganglioneuromatosis could represent less common features of these syndromes, potentially correlating with this novel PTEN frameshift and early protein termination genotype. Alternatively, because simultaneous disruption of both the PTEN and TGF-β/SMAD4 pathways is associated with development of esophageal cancer in a mouse model and because SMAD4 mutations cause gastrointestinal hamartomas in juvenile polyposis syndrome, the SMAD7 mutation may represent an additional modifier of these individuals' PTEN-mutant phenotype.

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.

The subcellular distribution and function of MTA1 in cancer differentiation

The functions and mechanisms of metastasis-associated protein 1 (MTA1) in cancer progression are still unclear due to a lagged recognition of the subcellular localization. In the present study, using multiple molecular technologies we confirmed for the first time that MTA1 localizes to the nucleus, cytoplasm and nuclear envelope. MTA1 is primarily localized in the nucleus of normal adult tissues but in the cytoplasm of embryonic tissues. While in colon cancer, both distributions have been described. Further investigation revealed that MTA1 localizes on the nuclear envelope in a translocated promoter region (TPR)-dependent manner, while in the cytoplasm, MTA1 shows an obvious localization on microtubules. Both nuclear and cytoplasmic MTA1 are associated with cancer progression. However, these functions may be associated with different mechanisms because only nuclear MTA1 has been associated with cancer differentiation. Overexpression of MTA1 in HCT116 cells inhibited differentiation and promoted proliferation, whereas MTA1 knockdown resulted in cell differentiation and death. Theses results not only suggest that nuclear MTA1 is a good marker for cancer differentiation diagnosis and a potential target for the treatment of cancers but also reveal the necessity to differentially examine the functions of nuclear and cytoplasmic MTA1.

SMAD7: a timer of tumor progression targeting TGF-β signaling

In the context of cancer, transforming growth factor β (TGF-β) is a cell growth suppressor; however, it is also a critical inducer of invasion and metastasis. SMAD is the important mediator of TGF-β signaling pathway, which includes receptor-regulated SMADs (R-SMADs), common-mediator SMADs (co-SMADs), and inhibitory SMADs (I-SMADs). I-SMADs block the activation of R-SMADs and co-SMADs and thus play important roles especially in the SMAD-dependent signaling. SMAD7 belongs to the I-SMADs. As an inhibitor of TGF-β signaling, SMAD7 is overexpressed in numerous cancer types and its abundance is positively correlated to the malignancy. Emerging evidence has revealed the switch-in-role of SMAD7 in cancer, from a TGF-β inhibiting protein at the early stages that facilitates proliferation to an enhancer of invasion at the late stages. This role change may be accompanied or elicited by the tumor microenvironment and/or somatic mutation. Hence, current knowledge suggests a tumor-favorable timer nature of SMAD7 in cancer progression. In this review, we summarized the advances and recent findings of SMAD7 and TGF-β signaling in cancer, followed by specific discussion on the possible factors that account for the functional changes of SMAD7.