Metastasis-associated protein 2 is a repressor of estrogen receptor alpha whose overexpression leads to estrogen-independent growth of human breast cancer cells

Identification of PIMREG as a novel prognostic signature in breast cancer via integrated bioinformatics analysis and experimental validation

Background

Phosphatidylinositol binding clathrin assembly protein interacting mitotic regulator (PIMREG) expression is upregulated in a variety of cancers. However, its potential role in breast cancer (BC) remains uncertain.

Methods

The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) databases were used to gather relevant information. The expression of PIMREG and its clinical implication in BC were assessed by using Wilcoxon rank-sum test. The prognostic value of PIMREG in BC was evaluated through the Cox regression model and nomogram, and visualized by Kaplan-Meier survival curves. Genes/proteins that interact with PIMREG in BC were also identified through GeneMANIA and MaxLink. Gene set enrichment analysis (GSEA) was then performed. The correlations of the immune cell infiltration and immune checkpoints with the expression of PIMREG in BC were explored via TIMER, TISIDB, and GEPIA. Potential drugs that interact with PIMREG in BC were explored via Q-omic. The siRNA transfection, CCK-8, and transwell migration assay were conducted to explore the function of PIMREG in cell proliferation and migration.

Results

PIMREG expression was significantly higher in infiltrating ductal carcinoma, estrogen receptor negative BC, and progestin receptor negative BC. High expression of PIMREG was associated with poor overall survival, disease-specific survival, and progression-free interval. A nomogram based on PIMREG was developed with a satisfactory prognostic value. PIMREG also had a high diagnostic ability, with an area under the curve of 0.940. Its correlations with several immunomodulators were also observed. Immune checkpoint CTLA-4 was significantly positively associated with PIMREG. HDAC2 was found as a potentially critical link between PIMREG and BRCA1/2. In addition, PIMREG knockdown could inhibit cell proliferation and migration in BC.

Conclusions

The high expression of PIMREG is associated with poor prognosis and immune checkpoints in BC. HDAC2 may be a critical link between PIMREG and BRCA1/2, potentially a therapeutic target.

Identification of potential inhibitory analogs of metastasis tumor antigens (MTAs) using bioactive compounds: revealing therapeutic option to prevent malignancy

The deeper understanding of metastasis phenomenon and detection of drug targets could be a potential approach to minimize cancer mortality. In this study, attempts were taken to unmask novel therapeutics to prevent metastasis and cancer progression. Initially, we explored the physiochemical, structural and functional insights of three metastasis tumor antigens (MTAs) and evaluated some plant-based bioactive compounds as potent MTA inhibitors. From 50 plant metabolites screened, isoflavone, gingerol, citronellal and asiatic acid showed maximum binding affinity with all three MTA proteins. The ADME analysis detected no undesirable toxicity that could reduce the drug likeness properties of top plant metabolites. Moreover, molecular dynamics studies revealed that the complexes were stable and showed minimum fluctuation at molecular level. We further performed ligand-based virtual screening to identify similar drug molecules using a large collection of 376,342 compounds from DrugBank. The results suggested that several structural analogs (e.g., tramadol, nabumetone, DGLA and hydrocortisone) may act as agonist to block the MTA proteins and inhibit cancer progression at early stage. The study could be useful to develop effective medications against cancer metastasis in future. Due to encouraging results, we highly recommend further in vitro and in vivo trials for the experimental validation of the findings.

Long Noncoding RNA TTC39A-AS1 Promotes Breast Cancer Tumorigenicity by Sponging MicroRNA-483-3p and Thereby Upregulating MTA2

INTRODUCTION

In recent years, the regulatory activities of long noncoding RNAs have received increasing attention as an important research focus. This study aimed to characterize the expression and detailed roles of TTC39A antisense RNA 1 (TTC39A-AS1) in breast cancer (BC), in addition to concentrating on its downstream mechanisms.

METHODS

Quantitative RT-PCR was performed to determine the expression levels of TTC39A-AS1, microRNA-483-3p (miR-483-3p), and metastasis-associated gene 2 (MTA2). Further, the detailed functions of TTC39A-AS1 in BC cells were confirmed using the Cell Counting Kit 8 assay, flow cytometric analysis, and Transwell cell migration and invasion assays. The targeting relationship between TTC39A-AS1, miR-483-3p, and MTA2 in BC was predicted via bioinformatics analysis and further confirmed by performing the luciferase reporter assay and RNA immunoprecipitation.

RESULTS

TTC39A-AS1 was present in high levels in BC; this result was confirmed in our sample cohort and The Cancer Genome Atlas database. Patients with BC with a high level of TTC39A-AS1 had a shorter overall survival than those with a low level of TTC39A-AS1. Functionally, the absence of TTC39A-AS1 accelerated cell apo-ptosis but retained cell proliferation, migration, and invasion. Mechanistically, TTC39A-AS1 functioned as a competing endogenous RNA in BC by sponging miR-483-3p and thereby indirectly increasing MTA2 expression. Finally, rescue experiments revealed that the tumor-inhibiting actions of TTC39A-AS1 knockdown on the malignant characteristics of BC cells could be reversed by inhibiting miR-483-3p or upregulating MTA2.

CONCLUSION

The newly identified TTC39A-AS1/miR-483-3p/MTA2 pathway was revealed to be a critical regulator in the tumorigenicity of BC, possibly offering a novel therapeutic direction for the anticancer treatment of BC.

Identification of potential inhibitory analogs of metastasis tumor antigens (MTAs) using bioactive compounds: revealing therapeutic option to prevent malignancy.. [DOI: 10.1101/2020.10.19.345975]

The deeper understanding of metastasis phenomenon and detection of drug targets could be a potential approach to minimize cancer mortality. In this study, attempts were taken to unmask novel therapeutics to prevent metastasis and cancer progression. Initially, we explored the physiochemical, structural and functional insights of three metastasis tumor antigens (MTAs) and evaluated some plant based bioactive compounds as potent MTA inhibitors. From 50 plant metabolites screened, isoflavone, gingerol, citronellal and asiatic acid showed maximum binding affinity with all three MTA proteins. The ADME analysis detected no undesirable toxicity that could reduce the drug likeness properties of top plant metabolites. Moreover, molecular dynamics studies revealed that the complexes were stable and showed minimum fluctuation at molecular level. We further performed ligand based virtual screening to identify similar drug molecules using a large collection of 3,76,342 compounds from DrugBank. The results suggested that several structural analogs (e.g. Tramadol, Nabumetone, DGLA, Hydrocortisone) may act as agonist to block the MTA proteins and inhibit cancer progression at early stage. The study could be useful to develop effective medications against cancer metastasis in future. Due to encouraging results, we highly recommend furtherin vitroandin vivotrials for the experimental validation of the findings.

Scaffold attachment factor B: distribution and interaction with ERα in the rat brain

Scaffold attachment factor (SAFB) 1 and its homologue SAFB2 are multifunctional proteins that are involved in various cellular mechanisms, including chromatin organization and transcriptional regulation, and are also corepressors of estrogen receptor alpha (ERα). Both SAFBs are expressed at high levels in the brain. However, the distributions of SAFB1 and SAFB2 have yet to be characterized in detail and it is unclear whether both proteins interact with ERα in the brain. In this study, we investigated the expression and distribution of both SAFBs and their interaction with ERα in adult male rat brain. Immunohistochemical staining showed that SAFB1 and SAFB2 have a similar distribution pattern and are widely expressed throughout the brain. Double-fluorescence immunohistochemical and immunocytochemical analyses in primary cultures showed that the two SAFB proteins are localized in nuclei of neurons, astrocytes, and oligodendrocytes. Of note, SAFB2 was also found in cytoplasmic regions in these cell lineages. Both SAFB proteins were also expressed in ERα-positive cells in the medial preoptic area (MPOA) and arcuate and ventromedial hypothalamic nuclei. Co-immunoprecipitation experiments revealed that both SAFB proteins from the MPOA reciprocally interact with endogenous ERα. These results indicate that, in addition to a role in basal cellular function in the brain, the SAFB proteins may serve as ERα corepressors in hormone-sensitive regions.

LncRNA-MTA2TR functions as a promoter in pancreatic cancer via driving deacetylation-dependent accumulation of HIF-1α

Rationale: Hypoxia has been proved to contribute to aggressive phenotype of cancers, while functional and regulatory mechanism of long noncoding RNA (lncRNA) in the contribution of hypoxia on pancreatic cancer (PC) tumorigenesis is incompletely understood. The aim of this study was to uncover the regulatory and functional roles for hypoxia-induced lncRNA-MTA2TR (MTA2 transcriptional regulator RNA, AF083120.1) in the regulation of PC tumorigenesis. Methods: A lncRNA microarray confirmed MTA2TR expression in tissues of PC patients. The effects of MTA2TR on proliferation and metastasis of PC cells and xenograft models were determined, and the key mechanisms by which MTA2TR promotes PC were further dissected. Furthermore, the expression and regulation of MTA2TR under hypoxic conditions in PC cells were assessed. We also assessed the correlation between MTA2TR expression and PC patient clinical outcomes. Results: We found that metastasis associated protein 2 (MTA2) transcriptional regulator lncRNA (MTA2TR) was overexpressed in PC patient tissues relative to paired noncancerous tissues. Furthermore, we found that depletion of MTA2TR significantly inhibited PC cell proliferation and invasion both in vitro and in vivo. We further demonstrated that MTA2TR transcriptionally upregulates MTA2 expression by recruiting activating transcription factor 3 (ATF3) to the promoter area of MTA2. Consequentially, MTA2 can stabilize the HIF-1α protein via deacetylation, which further activates HIF-1α transcriptional activity. Interestingly, our results revealed that MTA2TR is transcriptionally regulated by HIF-1α under hypoxic conditions. Our clinical samples further indicated that the overexpression of MTA2TR was correlated with MTA2 upregulation, as well as with reduced overall survival (OS) in PC patients. Conclusions: These results suggest that feedback between MTA2TR and HIF-1α may play a key role in regulating PC tumorigenesis, thus potentially highlighting novel avenues PC treatment.

Reciprocal loop of hypoxia-inducible factor-1α (HIF-1α) and metastasis-associated protein 2 (MTA2) contributes to the progression of pancreatic carcinoma by suppressing E-cadherin transcription

Metastasis-associated protein 2 (MTA2) is overexpressed in certain malignancies, and plays important roles in tumour metastasis and progression. The present study highlights the function of MTA2 in pancreatic carcinoma through its role as a deacetylator of hypoxia-inducible factor-1α (HIF-1α) and a cotranscriptional factor for E-cadherin expression. We found that overexpression of MTA2 promoted, and knockdown of MTA2 inhibited, the invasion and proliferation of pancreatic carcinoma cells both in vitro and in xenograft models in vivo. We also found that MTA2 is transcriptionally upregulated by HIF-1α through a hypoxia response element (HRE) of the MTA2 promoter in response to hypoxia. Reciprocally, MTA2 deacetylates HIF-1α and enhances its stability through interacting with histone deacetylase 1 (HDAC1). Consequently, HIF-1α recruits MTA2 and HDAC1 to the HRE of the E-cadherin promoter, by which E-cadherin transcription is repressed. In agreement with these experimental results, MTA2 is positively associated with HIF-1α, but inversely correlated with E-cadherin, in pancreatic carcinoma samples. Moreover, data from The Cancer Genome Atlas on 172 pancreatic carcinomas indicate an association between high expression of MTA2 and short overall survival. Taken together, our study identifies MTA2 as a critical hub and potential therapeutic target to inhibit the progression and metastasis of pancreatic carcinoma. Copyright © 2018 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

miR-1236-3p inhibits invasion and metastasis in gastric cancer by targeting MTA2

Background

MicroRNAs deregulation are common in human tumor progression. miR-1236-3p has been reported to function as tumor suppressor microRNA in various malignancies. The aim of this study was to demonstrate the downregulated expression of miR-1236-3p in gastric cancer (GC) tissues and cell lines, and clarify its biological function in GC.

Methods

Real-time polymerase chain reaction was used to measure the mRNA level of miR-1236-3p in GC. Dual luciferase assay was used to demonstrate that MTA2 was one of the candidate target genes of miR-1236-3p. Western blots were utilized to detect the protein levels. Cell function assays were also performed to determine the function of miR-1236-3p in GC.

Results

miR-1236-3p expression, which was associated with lymph node metastasis, differentiation and clinical stage, was significantly reduced in GC tissues and cell lines. miR-1236-3p over-expression could inhibit GC cell proliferation, migration and invasion, and inhibition of miR-1236-3p expression had opposite effects. Furthermore, we demonstrated that MTA2 was a candidate target of miR-1236-3p, and miR-1236-3p over-expression significantly inhibited the process of epithelial-mesenchymal transition. We also found that miR-1236-3p could suppress the PI3K/Akt signaling pathway in GC cells.

Conclusions

Our results suggest that miR-1236-3p functions as a tumor suppressor in GC and could be a promising therapeutic target for GC.

Colocalization of metastasis-associated proteins 1/2 and estrogen receptor alpha in rat epididymis

It has been suggested that metastasis-associated proteins 1 and 2 (MTA1 and MTA2) are capable of suppressing estrogen receptor alpha (ERα) transactivation activity in breast cancer cells. ERα, which is present in the epididymis, is a crucial mediator of maintaining the luminal environment necessary for proper sperm maturation and function. The present study was undertaken to analyze the expression profile of both MTA1 and MTA2 in the epididymis of rats and to ascertain whether MTA1/2 colocalizes with ERα in the epididymis and primary cultured epididymal epithelial cells. Reverse transcription polymerase chain reaction (RT-PCR), Western blotting and immunohistochemistry analyses were utilized to demonstrate that MTA1 and MTA2 are expressed in the epididymis. Furthermore, these analyses revealed that MTA1 and MTA2 are predominantly localized in the nuclei of almost all epididymal epithelial cells. Immunofluorescence staining revealed that MTA1/2 colocalizes with ERα in epididymal epithelial cells. In conclusion, MTA1 and MTA2 are expressed in the epididymis of rats; these proteins colocalize with ERα in epididymal epithelial cells, suggesting that MTA1 and MTA2 may be involved in the regulation of ERα transactivation activity in the epididymis of rats to facilitate a stable environment in the lumen.

UTX promotes hormonally responsive breast carcinogenesis through feed-forward transcription regulation with estrogen receptor

UTX is implicated in embryonic development and lineage specification. However, how this X-linked histone demethylase contributes to the occurrence and progression of breast cancer remains to be clarified. Here we report that UTX is physically associated with estrogen receptor (ER) and functions in ER-regulated transcription. We showed that UTX coordinates with JHDM1D and CBP to direct H3K27 methylation-acetylation transition and to create a permissive chromatin state on ER targets. Genome-wide analysis of the transcriptional targets of UTX by ChIP-seq identified a set of genes such as chemokine receptor CXCR4 that are intimately involved in breast cancer tumorigenesis and metastasis. We demonstrated that UTX promotes the proliferation and migration of ER⁺ breast cancer cells. Interestingly, UTX itself is transactivated by ER, forming a feed-forward loop in the regulation of hormone response. Indeed, UTX is upregulated during ER⁺ breast cancer progression, and the expression level of UTX is positively correlated with that of CXCR4 and negatively correlated with the overall survival of ER⁺ breast cancer patients. Our study identified a feed-forward loop between UTX and ER in the regulation of hormonally responsive breast carcinogenesis, supporting the pursuit of UTX as an emerging therapeutic target for the intervention of certain ER⁺ breast cancer with specific epigenetic vulnerability.

Single nucleotide variants in metastasis-related genes are associated with breast cancer risk, by lymph node involvement and estrogen receptor status, in women with European and African ancestry

Single nucleotide polymorphisms (SNPs) in pathways influencing lymph node (LN) metastasis and estrogen receptor (ER) status in breast cancer may partially explain inter-patient variability in prognosis. We examined 154 SNPs in 12 metastasis-related genes for associations with breast cancer risk, stratified by LN and ER status, in European-American (EA) and African-American (AA) women. Two-thousand six hundred and seventy-one women enrolled in the Women's Circle of Health Study were genotyped. Pathway analyses were conducted using the adaptive rank truncated product (ARTP) method, with pARTP  ≤ 0.10 as significant. Multi-allelic risk scores were created for the ARTP-significant gene(s). Single-SNP and risk score associations were modeled using logistic regression, with false discovery rate (FDR) P-value adjustment. Although single-SNP associations were not significant at pFDR  < 0.05, several genes were significant in the ARTP analyses. In AA women, significant ARTP gene-level associations included CDH1 with LN+ (pARTP  = 0.10; multi-allelic OR = 1.13, 95%CI 1.07-1.19, pFDR  = 0.0003) and SIPA1 with ER- breast cancer (pARTP  = 0.10; multi-allelic OR = 1.16, 95%CI 1.02-1.31, pFDR  = 0.03). In EA women, MTA2 was associated with overall breast cancer risk (pARTP  = 0.004), regardless of ER status, and with LN- disease (pARTP  = 0.01). Also significant were SATB1 in ER- (pARTP  = 0.03; multi-allelic OR = 1.12, 95%CI 1.05-1.20, pFDR  = 0.003) and KISS1 in LN- (pARTP  = 0.10; multi-allelic OR = 1.18, 95%CI 1.08-1.29, pFDR  = 0.002) analyses. Among LN+ cases, significant ARTP associations were observed for SNAI1, CD82, NME1, and CTNNB1 (multi-allelic OR = 1.09, 95%CI 1.04-1.14, pFDR  = 0.001). Our findings suggest that variants in several metastasis genes may affect breast cancer risk by LN or ER status, although verification in larger studies is required. © 2016 Wiley Periodicals, Inc.

Dexamethasone-Induced Intrauterine Growth Restriction Is Associated With Altered Expressions of Metastasis Tumor Antigens and Cell Cycle Control Proteins in Rat Placentas

Molecular mechanisms affecting placental formation in intrauterine growth-restricted (IUGR) pregnancies are not clearly understood. Since metastasis tumor antigens (MTAs) MTA1 and MTA2 promote cell proliferation and MTA3 suppresses it, we hypothesized that IUGR alters cell survival/cell death programs driven by placental MTAs. To induce IUGR, pregnant Sprague Dawley rats were given daily intraperitoneal injections of either saline or dexamethasone (0.4 mg/kg) starting from 14 days of gestation (dg) to either 19 dg or 21 dg. Gene and protein expressions of MTA1-3 in the placental basal and labyrinth zones were investigated by real-time polymerase chain reaction, Western blotting, and immunohistochemistry. We also explored the expressions of proliferating cell nuclear antigen (PCNA), caspase-3, p53, p21, and β-catenin. Dexamethasone-induced IUGR resulted in decreased expression of MTA1 in the nuclei of cells in the basal zone. The expression of p21 was increased and that of PCNA was reduced in both placental zones of IUGR rats. Cytoplasmic expression of MTA1 and p53 increased in the labyrinth zone of IUGR placentas in association with an increase in cell death as indicated by an increased caspase-3 expression. The labyrinth zone of IUGR placentas showed a significant reduction in MTA2-MTA3 gene expression and an increase in p53 protein levels. Total MTA3 level increased and β-catenin level decreased in the labyrinth zone of IUGR placentas associated with a reduction in cell proliferation. Taken together, these results strongly suggest that dexamethasone-induced IUGR is associated with changes in MTA expression, decreased cell proliferation, and increased cell death in placentas.

Germacrone Inhibits Estrogen Receptor α-Mediated Transcription in MCF-7 Breast Cancer Cells

Estrogen receptor (ER)α-positive breast cancer cells regulate the expression of estrogen-responsive genes, which are involved in cell proliferation, differentiation, and cell cycle progression. Clinically, the inhibition of ERα-mediated gene expression in breast cancer cells has long been considered an effective way to prevent the development and progression of cancer. Germacrone, a terpenoid compound isolated from Rhizoma curcuma, has been known to have antitumor activity in various human cancer cell lines. However, the mechanism by which germacrone inhibits the proliferation of breast cancer cells is still unclear. Here, we demonstrated that germacrone inhibits ERα-mediated gene expression at the transcriptional level in MCF-7 cells. Germacrone inhibits the recruitment of ERα to the estrogen response element on chromatin and consequently compromises the binding of switch/sucrose non-fermentable chromatin remodeling complex and RNA polymerase II to target gene promoter, thereby inhibiting the estrogen-induced chromatin accessibility. In addition, germacrone efficiently potentiates the antitumor activity of methotrexate and 5-fluorouracil. Our results not only provide substantial molecular mechanism of germacrone on ERα-mediated signaling in breast cancer cells but also demonstrate the benefits of germacrone as a combination therapy with other drugs for the treatment of breast cancer. Copyright © 2016 John Wiley & Sons, Ltd.

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.

Role of MTA2 in human cancer

Metastasis is the ultimate cause of death for most cancer patients. While many mechanisms have been delineated for regulation of growth and tumor initiation of the primary tumor, very little is known about the process of metastasis. Metastasis requires dynamic alteration of cellular processes in order for cells to disseminate from the primary tumor to distant sites. These alterations often involve dramatic changes in the regulation of cytoskeletal and cell-environment interactions. Furthermore, controlled refinement of these interactions requires feedback to regulatory networks in the nucleus. MTA2 is a member of the metastasis tumor-associated family of transcriptional regulators and is a central component of the nucleosome remodeling and histone deacetylation complex. MTA2 acts as a central hub for cytoskeletal organization and transcription and provides a link between nuclear and cytoskeletal organization. We will focus on MTA2 in this chapter, especially its role in breast cancer metastasis.

Structure and function insights into the NuRD chromatin remodeling complex

Transcription regulation through chromatin compaction and decompaction is regulated through various chromatin-remodeling complexes such as nucleosome remodeling and histone deacetylation (NuRD) complex. NuRD is a 1 MDa multi-subunit protein complex which comprises many different subunits, among which histone deacetylases HDAC1/2, ATP-dependent remodeling enzymes CHD3/4, histone chaperones RbAp46/48, CpG-binding proteins MBD2/3, the GATAD2a (p66α) and/or GATAD2b (p66β) and specific DNA-binding proteins MTA1/2/3. Here, we review the currently known crystal and NMR structures of these subunits, the functional data and their relevance for biomedical research considering the implication of NuRD subunits in cancer and various other diseases. The complexity of this macromolecular assembly, and its poorly understood mode of interaction with the nucleosome, the repeating unit of chromatin, illustrate that this complex is a major challenge for structure-function relationship studies which will be tackled best by an integrated biology approach.

Prognostic correlation between MTA2 expression level and colorectal cancer

OBJECTIVES

Association of MTA2 expression with presence, development, metastasis and prognosis of colorectal cancer (CRC) was investigated.

METHODS

90 CRC-related cases with follow-up information were made into tissue microarrays according to the paired principle of cancer tissues and the adjacent tissues. Subsequently, the expression of MAT2 was detected with immunohistochemical analysis and SPSS software was finally utilized to analyze the relationships between experimental data and clinical indicatives.

RESULTS

Expression of MTA2 in CRC tissues were notably higher than their adjacent tissues (P < 0.001) and showed significant positive correlation with tumor grade (r(2) > 0, P < 0.01). Moreover, survival analysis indicated that MTA2 expression in cancer tissues, serving as an independent correlation factor, was significantly correlated with poor prognosis (P = 0.004).

CONCLUSIONS

MTA2 is a crucial biomarker that is closely related with prognosis of CRC and also a potential molecular target for evaluating the prognosis and treatment of 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.

Metastasis-associated protein 2 (MTA2) promotes the metastasis of non-small-cell lung cancer through the inhibition of the cell adhesion molecule Ep-CAM and E-cadherin

OBJECTIVE

Metastasis-associated protein 2 is considered as an intrinsic subunit of the nucleosome remodelling and histone deacetylase complex, which contributes to the epigenetic silencing genes. More and more evidence suggests that metastasis-associated protein 2 is required to maintain the malignant phenotype, but the role of metastasis-associated protein 2 function in mediating tumour metastasis in non-small-cell lung cancer has not been explored.

METHODS

Bioinformatics was used to detect the GEO 3141 database, the online tool of Kmplot was used to confirm the high expression of metastasis-associated protein 2 in influencing 5-year overall survival. Wound-healing assay, Transwell invasion assay and Living imaging assay together showed that MTA2 shRNA inhibited cell migration and invasion in vitro and in vivo. Chromatin immunoprecipitation, quantitative chromatin immunoprecipitation and luciferase reporter assays showed metastasis-associated protein 2 binding on the promoter of the epithelial transmembrane glycoprotein (Ep-CAM) and cell adhesion molecule E-cadherin.

RESULTS

The patient samples collected in our hospital show that metastasis-associated protein 2 was expressed in aggressive lung cancer cells, and its higher expression is correlated with poor prognosis. Metastasis-associated protein 2 promoted cell migration and invasion in vitro and in vivo through binding on the promoter of Ep-CAM and E-cadherin. Luciferase reporter assays showed repressed or enhanced E-cadherin or Ep-CAM promoter-driven luciferase reporter under metastasis-associated protein 2 overexpression or depletion. The changes in the level of protein and RNA implied that suppression of downstream E-cadherin or Ep-CAM was an important mechanism by which metastasis-associated protein 2 triggered epithelial-mesenchymal transition and metastasis.

CONCLUSIONS

Together, our experiments reveal the mechanism for metastasis-associated protein 2 in facilitating invasive potential of non-small-cell lung cancer cells, suggesting that metastasis-associated protein 2 might be a potential therapeutic target for treating the metastasis of non-small-cell lung cancer.

MTA2 enhances colony formation and tumor growth of gastric cancer cells through IL-11

Background

We have preliminarily reported MTA2 expression in gastric cancer and its biological functions by using knockdown cell models, while the molecular mechanisms of MTA2 in regulating malignant behaviors are still unclear.

Methods

MTA2 overexpression models were established by transfection assay in gastric cancer cells BGC-823 and MKN28. Cell proliferation assay, colony formation in soft agar, wound-healing assay and transwell migration assay were performed with MTA2 overexpression and negative control (NC) cells. Subcutaneous xenografts and pulmonary metastasis models by BGC-823/MTA2 and BGC-823/NC cells were used to observe the capacity of growth and metastasis in vivo. Differential gene expression in MTA2 knockdown and overexpression cells was analyzed by microarrays. IL-11, which demonstrated as differential expression in microarray, was detected by real-time PCR, western blot, ELISA and immunohistochemistry staining. Recombinant human IL-11 (rhIL-11) was administrated in cell proliferation and colony formation as rescue assay.

Results

The numbers of colonies in soft agar were significantly more in BGC-823/MTA2 and MKN28/MTA2 cells, comparing with those in their NC cells. Capabilities of cell proliferation, wound-healing and cell migration were not significantly changed in MTA2 overexpression cells. The sizes of subcutaneous xenografts and pulmonary metastases of BGC-832/MTA2 cells were significantly larger than those in BGC-823/NC group. Differential expression of IL-11 was identified by genome expression microarray both in MTA2 knockdown and overexpression cells. IL-11 expression was elevated in BGC-823/MTA2 cells, whereas reduced in SGC-7901/shMTA2 cells. Administration of rhIL-11 recovered colony formation capacity of SGC-7901/shMTA2 cells.

Conclusions

MTA2 overexpression enhances colony formation and tumor growth of gastric cancer cells, but not plays important role in cancer cell migration and metastasis. IL-11 is one of the downstream effectors of MTA2 in regulating gastric cancer cells growth.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-015-1366-y) contains supplementary material, which is available to authorized users.

Clinical implications of MTA proteins in human cancer

Metastasis-associated gene or metastasis tumor antigen 1 (MTA1) is a new member of cancer progression-related gene family. It was first identified in rat mammary adenocarcinoma and later recognized as an important constituent of nucleosomal remodeling complex (NuRD), displaying dual regulatory functions as a co-repressor and co-activator for a large number of genes. Chromatin remodelers are ATP-dependent multi-protein chromatin modifying machines. These complexes alter the nucleosome positioning regulating the accessibility of genomic DNA to various transcription factors and thus modulate eukaryotic gene transcription. Since its identification two decades ago, MTA1 has been reported to be overexpressed in many cancers. Moreover, its overexpression has also been correlated with transformation and tumor progression. Furthermore, MTA1 has been shown to modulate the response of several tumor suppressor genes like p53 and oncogenes like c-myc. Taken together, current literature suggests that MTA proteins, especially MTA1, act as a master co-regulatory molecule involved in the carcinogenesis and progression of various malignant tumors. The primary focus of this review is to provide an overview of the MTA proteins with special emphasis on its role in cancer and use as a marker for cancer progression and potential target for therapy.

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.

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.

Expression and subcellular localization of metastasis-associated protein 1, its short form, and estrogen receptors in rat placenta

Metastasis-associated protein 1 (MTA1) and its short form (MTA1s) regulate the function of estrogen receptors (ERs). Estrogens, via ERs, affect placental growth and fetal development, a process that may involve MTA1 signaling. Expression of MTA1, MTA1s, ERα, and ERβ genes and proteins in rat placentas was studied on 16, 19, and 21 days of gestation (dg). The ERβ messenger RNA decreased significantly toward the end of gestation, whereas its protein level increased in the nuclear fraction on 21 dg. Both MTA1 and MTA1s increased with gestation. Decidual, trophoblast giant, glycogen, and villous trophoblast cells expressed MTA1, ERα, and ERβ proteins on all dg with colocalization of MTA1 with ERα and ERβ in the nucleus and cytoplasm. Expression of MTA1 suggests a possible role in regulating placental functions; considering the repressive function of MTA1 on ERs, the expression of MTA1 suggests that placental cells may be less sensitive to estrogens during late pregnancy.

Metastasis tumor-associated protein-2 knockdown suppresses the proliferation and invasion of human glioma cells in vitro and in vivo

Metastasis tumor-associated protein 2 (MTA2) is a member of the MTA family that is closely associated with tumor progression and metastasis. However, the role of MTA2 in glioma cells remains unclear. The expression of MTA2 was measured using immunohistochemistry and western blotting in the human brain tumor tissue array and human glioma cell lines. The impact of MTA2 knockdown on GBM8401 and Hs683 cell growth was evaluated by MTT assay and flow cytometry. Cell migration and invasion were analyzed by cell-migration assay and Matrigel invasion assay. In addition, we used subcutaneous tumor models to study the effect of MTA2 on the growth of glioma cells in vivo. We found that MTA2 protein and mRNA expression are higher in GBM8401 and Hs683 cells than in other glioma cells (M059 J, M059 K and U-87 MG), and glioma tumor tissue correlated significantly with tumor grade (P < 0.001). Knockdown of MTA2 expression significantly inhibited cell growth, cell migration and invasion, and induced G0/G1 phase arrest in human GBM8401 and Hs683 cells in vitro. Moreover, in vivo studies using subcutaneous xenografts in mice models indicate that MTA2 knockdown significantly inhibited tumorigenicity. These results indicate that MTA2 plays an important oncogenic role in the development and progression of gliomas.

SETD6 controls the expression of estrogen-responsive genes and proliferation of breast carcinoma cells

The lysine methyltransferase SETD6 modifies the histone variant H2AZ, a key component of nuclear receptor-dependent transcription. Herein, we report the identification of several factors that associate with SETD6 and are implicated in nuclear hormone receptor signaling. Specifically, SETD6 associates with the estrogen receptor α (ERα), histone deacetylase HDAC1, metastasis protein MTA2, and the transcriptional co-activator TRRAP. Luciferase reporter assays identify SETD6 as a transcriptional repressor, in agreement with its association with HDAC1 and MTA2. However, SETD6 behaves as a co-activator of several estrogen-responsive genes, such as PGR and TFF1. Consistent with these results, silencing of SETD6 in several breast carcinoma cell lines induced cellular proliferation defects accompanied by enhanced expression of the cell cycle inhibitor CDKN1A and induction of apoptosis. Herein, we have identified several chromatin proteins that associate with SETD6 and described SETD6 as an essential factor for nuclear receptor signaling and cellular proliferation.

Human β-defensin-3 inhibits migration of colon cancer cells via downregulation of metastasis-associated 1 family, member 2 expression

The innate immune system plays an important role as the first line of defense against many types of microbes. Accumulating reports suggest that human β-defensins (hBDs) are expressed by and have certain roles in some cancer cells. In this study, we investigated the roles of hBD-3 in colon cancer cells. The expression of hBD-3 was examined by reverse transcriptase-polymerase chain reaction analysis of colon cancer cell lines and immunohistochemical staining of colon cancer tissues. The effect of hBD-3 on proliferation of colon cancer was assessed using the MTT assay and a real-time cell analyzer, and the effect of hBD-3 on the migration of colon cancer cells was also examined. The results showed that hBD-3 is not expressed in colon cancer cells but is produced by tumor-infiltrating monocytes. Migration of colon cancer cells was significantly inhibited by hBD-3 in a dose-dependent manner, although proliferation of colon cancer cells was not affected by administration of hBD-3. Moreover, reduced expression of metastasis-associated 1 family, member 2 (MTA2) mRNA in colon cancer cells was associated with exposure to hBD-3. In conclusion, progression of colon cancer was inhibited by hBD-3 in a paracrine fashion. Therefore, hBD-3 may be a potent new agent for treating colon cancer.

Dual inhibition of EGFR at protein and activity level via combinatorial blocking of PI4KIIα as anti-tumor strategy

Our previous studies indicate that phosphatidylinositol 4-kinase IIα can promote the growth of multi-malignant tumors via HER-2/PI3K and MAPK pathways. However, the molecular mechanisms of this pathway and its potential for clinical application remain unknown. In this study, we found that PI4KIIα could be an ideal combinatorial target for EGFR treatment via regulating EGFR degradation. Results showed that PI4KIIα knockdown reduced EGFR protein level, and the expression of PI4KIIα shows a strong correlation with EGFR in human breast cancer tissues (r = 0.77, P < 0.01). PI4KIIα knockdown greatly prolonged the effects and decreased the effective dosage of AG-1478, a specific inhibitor of EGFR. In addition, it significantly enhanced AG1478-induced inhibition of tumor cell survival and strengthened the effect of the EGFR-targeting anti-cancer drug Iressa in xenograft tumor models. Mechanistically, we found that PI4KIIα suppression increased EGFR ligand-independent degradation. Quantitative proteomic analysis by stable isotope labeling with amino acids in cell culture (SILAC) and LC-MS/MS suggested that HSP90 mediated the effect of PI4KIIα on EGFR. Furthermore, we found that combined inhibition of PI4KIIα and EGFR suppressed both PI3K/AKT and MAPK/ERK pathways, and resulted in downregulation of multiple oncogenes like PRDX2, FASN, MTA2, ultimately leading to suppression of tumor growth. Therefore, we conclude that combined inhibition of PI4KIIα and EGFR exerts a multiple anti-tumor effect. Dual inhibition of EGFR at protein and activity level via combinatorial blocking of PI4KIIα presents a novel strategy to combat EGFR-dependent tumors.

Elicitation of metastasis associated protein 2 expression in the phagocytosis by murine testicular Sertoli cells

Efficient phagocytic clearance of apoptotic spermatogenic cells and residual bodies (RBs) by Sertoli cells (SCs) is crucial for functional mature spermatogenesis. However, little is known about the molecular mechanisms underlying this SCs function. Herein, we reported for the first time that SCs-expressing metastasis associated protein 2 (Mta2), a chromatin modifier playing a critical role in modifying DNA accessibility for transcriptional regulation, was steadily up-regulated when SCs were co-cultured with RBs. The most efficient stimulatory substrates for the inducement of phagocytosis-elicited Mta2 expression were RBs and fragments from apoptotic spermatocytes. Furthermore, one major result of this response is the transcriptional repression of follicle-stimulating hormone receptor gene (Fshr) expression during phagocytosis, which should lead to a low level of circulated FSH because effects of FSH on spermatogenesis is fundamentally regulated by the down-regulation of Fshr after exposure to FSH. Given that high concentration of circulated FSH inhibits SCs phagocytic activity and impairment of MTA2 expression is associated with the abnormal high level of serum FSH, our present results suggest that the FSH/MTA2/Fshr cascade may serve as an indispensable negative feedback mechanism to help to maintain low level of circulated FSH, which is required for the normal occurrence of SCs phagocytosis.

Metastasis tumor-associated protein 2 enhances metastatic behavior and is associated with poor outcomes in estrogen receptor-negative breast cancer

Metastasis remains a major clinical problem in breast cancer. One family of genes previously linked with metastasis is the metastasis tumor-associated (MTA) family, with members MTA1 enhancing and MTA3 inhibiting cancer metastasis. We have previously found that MTA2 enhances anchorage-independent growth in estrogen receptor α (ERα) breast cancers, and, in combination with other genes, performed as a predictive biomarker in ERα-positive breast cancer. We therefore hypothesized that MTA2 enhances breast cancer progression. To test this, cell growth, soft-agar colony formation, migration, and in vivo metastasis were examined in MTA2-overexpressing and Vector control transfected ERα-negative breast cancer cells. Pathways regulating cell-cell interaction, adhesion, and signaling through the Rho pathway were also investigated. Effects of the inhibition of the Rho pathway using a Rho Kinase inhibitor were assessed in soft-agar colony formation and motility assays in MTA2-overexpressing cells. MTA2 expression was associated with poor prognostic markers, and levels of MTA2 were associated with increased risk of early recurrence in retrospective analyses. MTA2 overexpression was associated with enhanced metastasis, and pathways regulating cell-cell interactions in vitro and in vivo. Most critically, MTA2-enhanced motility could be blocked by inhibiting Rho pathway signaling. We present the novel finding that MTA2 defined a subset of ERα-negative patients with a particularly poor outcome.

MTA2 expression is a novel prognostic marker for pancreatic ductal adenocarcinoma

The aim of this study was to detect MTA2 expression in pancreatic ductal adenocarcinoma (PDA) and to analyze its association with prognosis of PDA patients. MTA2 mRNA and protein expression were determined by real-time quantitative reverse transcriptase-polymerase chain reaction and immunohistochemistry in specimens of primary cancer and their adjacent noncancerous tissues in PDA patients. We found that MTA2 mRNA and protein expression levels were both significantly upregulated in PDA lesions compared with adjacent noncancerous tissues. Immunohistochemistry showed that high MTA2 expression was correlated with poor tumor differentiation, TNM stage, and lymph node metastasis. Kaplan-Meier survival analysis showed that patients with high expression levels of MTA2 showed lower overall survival rate than those with low expression levels. Multivariate analysis showed that high MTA2 protein expression was an independent prognostic factor for PDA patients. Our study suggests that overexpression of MTA2 may play an important role in the progression of PDA and MTA2 expression may serve as a biomarker for poor prognosis for PDA.

Sertoli cell-specific expression of metastasis-associated protein 2 (MTA2) is required for transcriptional regulation of the follicle-stimulating hormone receptor (FSHR) gene during spermatogenesis

BACKGROUND

Desensitization of FSH response by down-regulation of FSHR transcription is critical for FSH action.

RESULTS

Chromatin modifier MTA2 participates in the down-regulation of FSHR transcription.

CONCLUSION

The FSH/Ar/MTA2 cascade may serve as an indispensable negative feedback mechanism to modulate FSH transduction events in Sertoli cells.

SIGNIFICANCE

Our findings provide new insights into mechanisms by which FSH is deregulated in male infertile patients. The effect of follicle-stimulating hormone (FSH) on spermatogenesis is modulated at a fundamental level by controlling the number of competent receptors present at the surface of Sertoli cells (SCs). One underlying mechanism is the down-regulation of the expression levels of the FSH receptor (FSHR) gene after exposure to FSH. Here we report that metastasis-associated protein 2 (MTA2), a component of histone deacetylase and nucleosome-remodeling complexes, as a gene product induced directly by testosterone or indirectly by FSH, is exclusively expressed in SCs. Stimulation of SCs with FSH is accompanied by up-regulation of MTA2 expression and enhancement of deacetylase activity. This effect requires the integrity of functional androgen receptor. Furthermore, MTA2 is a potent corepressor of FSHR transcription, because it can recruit histone deacetylase-1 onto the FSHR promoter and participates in the down-regulation of FSHR expression upon FSH treatment. Abolishment of endogenous MTA2 by siRNA treatment disrupted the desensitization of the FSH response and thereafter impaired the FSH-dependent secretory function of SCs. From a clinical standpoint, deregulated expression of MTA2 in SCs of human pathological testes negatively correlates to the deregulated level of serum FSH. Overall, our present results provide the first evidence that the FSH/androgen receptor/MTA2 cascade may serve as an indispensable negative feedback mechanism to modulate the transduction events of SCs in response to FSH. These data also underscore an unexpected reproductive facet of MTA2, which may operate as a novel integrator linking synergistic actions of FSH and androgen signaling in SCs.

Expression of P120 catenin, Kaiso, and metastasis tumor antigen-2 in thymomas

Thymomas of the same histological subtype sometimes manifest different biological behaviors. Metastasis Tumor Antigen-2 (MTA2) is targeted by the transcriptional repressor Kaiso, the distribution which is thought to be modulated by p120catenin (p120ctn). It is currently unclear if expression of p120ctn, Kaiso, and MTA2 relates to the biological behavior of thymoma. P120ctn, Kaiso, and MTA2 expression were examined in 137 cases of thymoma, three cases of thymic carcinoma, and 18 paired autologous normal thymic tissues using immunohistochemistry, and correlation of these proteins with histological subtypes and clinical stages were analyzed. In normal thymic epithelial cells, p120ctn was expressed on the cell membrane but Kaiso and MTA2 were not detected. Membranous p120ctn expression was reduced in thymoma epithelial cells, while ectopic cytoplasmic expression was observed in 76.6 % (105/137) of the cases. Cytoplasmic Kaiso was detected in 69.3 % (95/137) and nuclear MTA2 was detected in 70.8 % (97/137) of the thymomas. There were good consistencies (Kappa = 0.559, 0.512, 0.652; all P < 0.001) and correlations (r = 0.733, 0.652, 0.708; all P < 0.001) between cytoplasmic p120ctn, cytoplasmic Kaiso, and nuclear MTA2 expression in thymomas. All three protein factors correlated with histological type and clinical stage in thymoma (P < 0.05). Specifically, cytoplasmic p120ctn and Kaiso expression and nuclear MTA2 expression were higher in high-risk (types B2 and B3) thymomas and Masaoka stage III/IV thymomas than low-risk (types A, AB, and B1) and stage I/II thymomas (both P < 0.001), respectively. Cytoplasmic p120ctn, cytoplasmic Kaiso, and nuclear MTA2 expression correlated directly with histological type and Masaoka stage and may thus be used as potential biomarkers to predict biological behavior of thymoma.

Expression of metastasis-associated protein 2 (MTA2) might predict proliferation in non-small cell lung cancer

Metastatic tumor antigen 2 (MTA2) is a member of the MTA family that is closely associated with tumor progression and metastasis. In this study, the expression profile of MTA2 in 223 cases of non-small cell lung cancer (NSCLC) tissues and two lung cancer cell lines was investigated. Interestingly, we found MTA2, which was believed to have nuclear distribution only, was distributed in both nucleus and cytoplasm in normal and cancer cells. Nuclear MTA2 expression was detected in 148 cases of NSCLC (66.4%), and was correlated with advanced TNM stages (p=0.023), tumor size (p=0.036), and lymph node metastasis (p=0.004). Besides, the Ki-67 proliferation index was significantly higher in nuclear MTA2-positive tumors than in nuclear MTA2-negative tumors (r=0.538, p=0.006). However, there was no significant difference in cytoplasmic MTA2 status by age, gender, tumor stage, histology, grade, lymph node metastasis, and Ki-67 proliferation index. Univariate analysis revealed nuclear MTA2 expression was correlated with poor overall survival (p=0.035), whereas there was a nonsignificant trend in the same direction for cytoplasmic MTA2 (p=0.134). Multivariate Cox regression analysis revealed the overexpression of nuclear and cytoplasmic MTA2 not to be independent factors predictive of poor disease outcome. Our data suggested that MTA2 might play roles in both the nucleus and cytoplasm in the progression of NSCLC.

Correlation between MTA2 overexpression and tumour progression in esophageal squamous cell carcinoma

The aim of this study was to clarify the clinicopathological outcome and prognostic significance of metastasis-associated gene 2 (MTA2) in esophageal squamous cell carcinoma (ESCC). Immunohistochemical staining for MTA2 was performed on surgical specimens obtained from 162 patients with ESCC. Relationships between MTA2 expression and clinicopathological factors, including prognosis, were analyzed. Significant correlations were noted among MTA2 overexpression and TNM clinical classification staging, depth of invasion, presence of regional lymph node metastasis, presence of distant metastasis, lymphatic invasion, blood-vessel invasion and the 5-year survival rates. The expression of MTA2 protein was correlated with tumour progression. Patients with MTA2 overexpression tended to have poor prognosis compared to patients with MTA2 underexpression.

ARTEMIN synergizes with TWIST1 to promote metastasis and poor survival outcome in patients with ER negative mammary carcinoma

Introduction

ARTEMIN (ARTN) is an estrogen regulated growth factor, the expression of which promotes resistance to antiestrogen therapies and predicts poorer survival outcome of patients with estrogen receptor (ER) positive mammary carcinoma (ER+MC) treated with tamoxifen. ARTN is also expressed in ER negative mammary carcinoma (ER-MC). Herein, we determined the role of ARTN in ER-MC and defined the mechanism of action producing poor patient prognosis.

Methods

We modulated the expression of ARTN in two ER- (mesenchymal/claudin-low) mammary carcinoma cell lines (BT549 and MDA-MB-231) by forced expression or small interfering RNA (siRNA) mediated depletion. The effects of modulation of ARTN expression were examined by various in vitro measures of oncogenicity, including the expression of TWIST1 messenger RNA (mRNA) and protein. In vitro results were correlated to xenograft studies in immunodeficient mice. Co-expression of ARTN and TWIST1 and their association to poor survival outcome were examined in a cohort of patients with ER-MC. Pathway analysis was performed by pharmacological inhibition of phosphorylation of AKT (pAKT-Ser 473) or modulation of TWIST1 expression.

Results

ARTN expression resulted in ER-MC cells with enhanced mesenchymal characteristics, including increased invasion and a gene expression profile consistent with enhanced mesenchymal phenotype. ARTN stimulated ER-MC cell anchorage independent and 3D matrigel growth, endothelial cell adhesion and transmigration of ER-MC cells through an endothelial cell barrier. Forced expression of ARTN produced a larger, locally invasive tumour mass with tumour emboli that produced distant metastasis. ARTN regulated TWIST1 expression in ER-MC cells and ARTN expression was significantly correlated to TWIST1 expression in a panel of mammary carcinoma cell lines and in a cohort of patients with ER-MC. Low expression of both ARTN and TWIST1 predicted 100% relapse free and overall survival in patients with ER-MC, whereas high expression of both ARTN and TWIST1 was associated with a poor survival outcome. ARTN stimulated an increase in TWIST1 expression via increased AKT activity. siRNA mediated depletion of TWIST1 abrogated ARTN stimulated cellular behaviour associated with metastasis, and forced expression of TWIST1 abrogated the functional effects of ARTN depletion.

Conclusions

ARTN and TWIST1 synergize to produce a worse outcome in ER-MC and combined inhibition of ARTN and phosphatidylinositol 3-kinase/protein kinase B (PI3K/AKT) may therefore provide a novel therapeutic strategy in this subtype of mammary carcinoma.

Loss of Rho GDIα and resistance to tamoxifen via effects on estrogen receptor α

BACKGROUND

Estrogen receptor (ER) α is a successful therapeutic target in breast cancer, but patients eventually develop resistance to antiestrogens such as tamoxifen.

METHODS

To identify genes whose expression was associated with the development of tamoxifen resistance and metastasis, we used microarrays to compare gene expression in four primary tumors from tamoxifen-treated patients whose breast cancers did not recur vs five metastatic tumors from patients whose cancers progressed during adjuvant tamoxifen treatment. Because Rho guanine dissociation inhibitor (GDI) α was underexpressed in the tamoxifen-resistant group, we stably transfected ERα-positive MCF-7 breast cancer cells with a plasmid encoding a short hairpin (sh) RNA to silence Rho GDIα expression. We used immunoblots and transcription assays to examine the role of Rho GDIα in ER-related signaling and growth of cells in vitro and as xenografts in treated nude mice (n = 8-9 per group) to examine the effects of Rho GDIα blockade on hormone responsiveness and metastatic behavior. The time to tumor tripling as the time in weeks from randomization to a threefold increase in total tumor volume over baseline was examined in treated mice. The associations of Rho GDIα and MTA2 levels with tamoxifen resistance were examined in microarray data from patients. All statistical tests were two-sided.

RESULTS

Rho GDIα was expressed at lower levels in ERα-positive tumors that recurred during tamoxifen treatment than in ERα-positive tamoxifen-sensitive primary tumors. MCF-7 breast cancer cells in which Rho GDIα expression had been silenced were tamoxifen-resistant, had increased Rho GTPase and p21-activated kinase 1 activity, increased phosphorylation of ERα at serine 305, and enhanced tamoxifen-induced ERα transcriptional activity compared with control cells. MCF-7 cells in which Rho GDIα expression was silenced metastasized with high frequency when grown as tumor xenografts. When mice were treated with estrogen or estrogen withdrawal, tripling times for xenografts from cells with Rho GDIα silencing were similar to those from vector-containing control cells; however, tripling times were statistically significantly faster than control when mice were treated with tamoxifen (median tripling time for tumors with Rho GDIα small interfering RNA = 2.34 weeks; for control tumors = not reached, hazard ratio = 4.13, 95% confidence interval = 1.07 to 15.96, P = .040 [adjusted for multiple comparisons, P = .119]). Levels of the metastasis-associated protein MTA2 were also increased upon Rho GDIα silencing, and combined Rho GDIα and MTA2 levels were associated with recurrence in 250 tamoxifen-treated patients.

CONCLUSION

Loss of Rho GDIα enhances metastasis and resistance to tamoxifen via effects on both ERα and MTA2 in models of ERα-positive breast cancer and in tumors of tamoxifen-treated patients.

Acetylation and nuclear receptor action

Acetylation is an essential post-translational modification featuring an acetyl group that is covalently conjugated to a protein substrate. Histone acetylation was first proposed nearly half a century ago by Dr. Vincent Allfrey. Subsequent studies have shown that the acetylated core histones are often associated with transcriptionally active chromatin. Acetylation at lysine residues of histone tails neutralizes the positive charge, which decreases their binding ability to DNA and increases the accessibility of transcription factors and coactivators to the chromatin template. In addition to histones, a number of non-histone substrates are acetylated. Acetylation of non-histone proteins governs biological processes, such as cellular proliferation and survival, transcriptional activity, and intracellular trafficking. We demonstrated that acetylation of transcription factors can regulate cellular growth. Furthermore, we showed that nuclear receptors (NRs) are acetylated at a phylogenetically conserved motif. Since our initial observations with the estrogen and androgen receptors, more than a dozen NRs have been shown to function as substrates for acetyltransferases with diverse functional consequences. This review focuses on the acetylation of NRs and the effect of acetylation on NR function. We discuss the potential role of acetylation in disease initiation and progression with an emphasis on tumorigenesis.

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.

[Expression and significance of MTA2 in non-small cell lung cancer]

背景与目的

已有研究发现转移相关蛋白2（metastasis-associated protein 2, MTA2）在多种肿瘤细胞系中表达且与肿瘤侵袭转移密切相关。本研究旨在研究MTA2在非小细胞肺癌（non-small cell lung cancer, NSCLC）中的表达，并探讨MTA2表达与临床病理特征的关系。

方法

采用免疫组织化学（SP）方法检测110例非小细胞肺癌标本及34例癌旁肺组织中MTA2蛋白表达，并统计分析其表达与NSCLC临床病理特征关系。

结果

MTA2在癌旁肺支气管上皮和肺泡上皮中无表达，在部分NSCLC中呈阳性表达。110例NSCLC标本中MTA2阳性表达率为58.18%（64/110)，MTA2阳性表达与NSCLC的分化程度呈负相关，与临床分期、淋巴结转移呈正相关（P < 0.05），与年龄、性别、NSCLC的病理分型无明显相关性（P > 0.05）。

结论

MTA2蛋白在部分NSCLC中呈阳性表达且与其分化程度、临床分期、淋巴结转移密切相关，提示肺癌的发生发展可能与MTA2有关，MTA2可能是肺癌新的标志物及治疗靶点。

The TWIST/Mi2/NuRD protein complex and its essential role in cancer metastasis

The epithelial-mesenchymal transition (EMT) converts epithelial tumor cells into invasive and metastatic cancer cells, leading to mortality in cancer patients. Although TWIST is a master regulator of EMT and metastasis for breast and other cancers, the mechanisms responsible for TWIST-mediated gene transcription remain unknown. In this study, purification and characterization of the TWIST protein complex revealed that TWIST interacts with several components of the Mi2/nucleosome remodeling and deacetylase (Mi2/NuRD) complex, MTA2, RbAp46, Mi2 and HDAC2, and recruits them to the proximal regions of the E-cadherin promoter for transcriptional repression. Depletion of these TWIST complex components from cancer cell lines that depend on TWIST for metastasis efficiently suppresses cell migration and invasion in culture and lung metastasis in mice. These findings not only provide novel mechanistic and functional links between TWIST and the Mi2/NuRD complex but also establish new essential roles for the components of Mi2/NuRD complex in cancer metastasis.

GATA-binding protein-3 regulates T helper type 2 cytokine and ifng loci through interaction with metastasis-associated protein 2

GATA-binding protein-3 (GATA-3) regulates the T helper type 2 (Th2) cytokine locus through induction of chromatin remodelling. However, the molecular mechanism for this is poorly understood. To understand this mechanism better, we screened GATA-3 interacting proteins using affinity purification and mass spectrometry. We found that GATA-3 bound to metastasis-associated protein 2 (MTA-2), a component of the NuRD chromatin remodelling complex. GATA-3 and MTA-2 in turn bound to several regulatory regions of the Th2 cytokine locus and the ifng promoter. Cell transfection assay showed that MTA-2 acted as an antagonist with GATA-3 in the expression of Th2 cytokines, but co-operated with GATA-3 in the repression of the ifng gene expression. These results suggest that GATA-3 interacts with MTA-2 to co-ordinately regulate Th2 cytokine and ifng loci during T helper cell differentiation.

A hypersensitive estrogen receptor alpha mutation that alters dynamic protein interactions

Estrogen receptor alpha (ERalpha) is highly regulated through multiple mechanisms including cell signaling, posttranslational modifications, and protein-protein interactions. We have previously identified a K303R ERalpha mutation within the hinge region of ERalpha. This mutation results in an altered posttranslational regulation and increased in vitro growth in the presence of low estrogen concentrations. We sought to determine if cells expressing this mutant ERalpha would display hypersensitive tumor growth in in vivo athymic ovariectomized nude mice. MCF-7 cells, stably expressing the K303R ERalpha, formed tumors in nude mice faster than cells expressing wild-type ERalpha in the presence of low levels of estrogen. When estrogen was withdrawn, all tumors regressed but half of the K303R ERalpha-expressing tumors became estrogen-independent and regrew. We evaluated potential mechanisms for the observed hypersensitivity. The mutant ERalpha did not demonstrate increased estrogen binding affinity, but did exhibit increased interactions with members of the SRC family of coactivators. The mutant ERalpha demonstrated increased levels and occupancy time on the pS2 promoter. In the presence of the K303R ERalpha, the SRC-3 and p300 coactivators also displayed increased levels and time on the pS2 promoter. The K303R ERalpha has, in part, lost critical negative regulation by the F domain. Collectively, these data demonstrate an important role for the K303R ERalpha mutation in hormonal regulation of tumor growth and estrogen-regulated promoter dynamics in human breast cancer.

Overexpression of metastasis-associated protein 2 is associated with hepatocellular carcinoma size and differentiation

BACKGROUND AND AIM

Metastasis is a multistep event in which neoplastic cells detach from the tumor, migrate, disseminate, extravasate, and eventually proliferate at the secondary distant sites. Hepatocellular carcinoma (HCC) is characterized by hypervascularity and frequent metastasis. Recently, metastasis-associated proteins were identified and named metastatic tumor antigens (MTA) 1, 2, and 3. They have been found to be contained in the nucleosome remodeling and histone deacetylase complex. MTA2 has been reported to interact with p53 and inhibit p53-mediated cell growth arrest and apoptosis by deacetylation. Although it has been reported that the expression of MTA1 is related to tumor progression and metastasis, it is still unclear how MTA2 is involved in HCC. In this study, we found that the overexpression of MTA2 is associated with HCC size and differentiation after hepatectomy.

METHODS

The expression of MTA2 was examined in 506 human HCC samples that underwent hepatic resection using tissue microarray. The expression of MTA2 was classified into 0, 1, 2, and 3, based on immunoreactivity.

RESULTS

The expression of MTA2 was predominantly localized to the nucleus. MTA2 was detected in 487 (96.2%) of the 506 human HCC samples. Notably, the MTA2 expression level strongly increased depending on the size and differentiation of HCC.

CONCLUSIONS

These findings indicate a tight correlation between the MTA2 expression level and HCC size and differentiation. Therefore, MTA2 might be a predictor of aggressive phenotypes and a possible target molecule for anticancer drug design in human HCC.

Accelerated mammary maturation and differentiation, and delayed MMTVneu-induced tumorigenesis of K303R mutant ERalpha transgenic mice

We identified a somatic mutation in estrogen receptor-alpha (ERalpha) in breast cancer causing a lysine to arginine transition (K303R) resulting in hypersensitivity to estrogen, altered associations with coactivators and corepressors and altered posttranslational modifications of ERalpha. We have developed a transgenic mouse expressing the K303R mutant ERalpha under control of the mouse mammary tumor virus (MMTV) promoter. At 4 months of age, K303R ERalpha transgenic animals demonstrate precocious alveolar budding compared with wild-type ERalpha transgenic mice or nontransgenic littermates. Despite these morphologic differences, K303R ERalpha transgenic mice displayed no differences in levels of ERalpha, progesterone receptor or proliferation at this time-point. Pregnancy or chronic estrogen plus progesterone exposure in K303R ERalpha transgenic mice also resulted in significantly more alveolar budding, increased beta-casein production and dilated ducts when compared with nontransgenic littermates. To examine the effects of mutant expression on tumorigenesis, mutant ERalpha mice were crossed with FVB-MMTVneu mice and significantly delayed time to neu-mediated tumorigenesis in bigenic animals. In contrast, mutant expression did not affect carcinogen-induced tumorigenesis. Collectively, these data demonstrate that aberrant estrogenic signaling through the K303R ERalpha mutation may lead to precocious alveolar budding in virgin mice, and to an expedited maturation and differentiation phenotype in the mammary glands of hormonally stimulated animals.

The role of the MTA family and their encoded proteins in human cancers: molecular functions and clinical implications

MTA (metastasis-associated gene) is a newly discovered family of cancer progression-related genes and their encoded products. MTA1, the first gene found in this family, has been repeatedly reported to be overexpressed along with its protein product MTA1 in a wide range of human cancers. In addition, the expression of MTA1/MTA1 correlates with the clinicopathological properties (malignant properties) of human cancers. MTA proteins are transcriptional co-repressors that function in histone deacetylation and are involved in the NuRD complex, which contains nucleosome remodeling and histone deacetylating molecules. MTA1 expression correlates with tumor formation in the mammary gland. In addition, MTA1 converts breast cancer cells to a more aggressive phenotype by repression of the estrogen receptor (ER) alpha trans-activation function through deacetylation of the chromatin in the ER-responsive element of ER-responsive genes. Furthermore, MTA1 plays an essential role in c-MYC-mediated cell transformation. Another member of this family, MTA3, is induced by estrogen and represses the expression of the transcriptional repressor Snail, a master regulator of "epithelial to mesenchymal transitions", resulting in the expression of the cell adhesion molecule E-cadherin and maintenance of a differentiated, normal epithelial phenotype in breast cells. In addition, tumor suppressor p53 protein is deacetylated and inactivated by both MTA1 and MTA2, leading to inhibition of growth arrest and apoptosis. Moreover, a hypoxia-inducible factor-1alpha (HIF-1alpha) is also deacetylated and stabilized by MTA1, resulting in angiogenesis. Thus, MTA proteins, especially MTA1, represent a possible set of master co-regulatory molecules involved in the carcinogenesis and progression of various malignant tumors. MTA proteins are proposed to be important new tools for clinical application in cancer diagnosis and treatment.