Expression of the MTA1 mRNA in thymoma patients

MTA1 expression in human cancers - Clinical and pharmacological significance

Remarkably, majority of the cancer deaths are due to metastasis, not because of primary tumors. Metastasis is one of the important hallmarks of cancer. During metastasis invasion of primary tumor cells from the site of origin to a new organ occurs. Metastasis associated proteins (MTAs) are a small family of transcriptional coregulators that are closely associated with tumor metastasis. These proteins are integral components of nuclear remodeling and deacetylation complex (NuRD). By virtue of being integral components of NuRD, these proteins regulate the gene expression by altering the epigenetic changes such as acetylation and methylation on the target gene chromatin. Among the MTA proteins, MTA1 expression is very closely correlated with the aggressiveness of several cancers that includes breast, liver, colon, pancreas, prostate, blood, esophageal, gastro-intestinal etc. Considering its close association with aggressiveness in human cancers, MTA1 may be considered as a potential therapeutic target for cancer treatment. The recent developments in its crystal structure further strengthened the idea of developing small molecule inhibitors for MTA1. In this review, we discuss the recent trends on the diverse functions of MTA1 and its role in various cancers, with the focus to consider MTA1 as a 'druggable' target in the control of human cancers.

Metastasis-associated protein is a predictive biomarker for metastasis and recurrence in gastric cancer

The metastasis-associated (MTA) gene family is a critical component of the nucleosome remodeling and histone deacetylase complex, and plays an important role in metastatic processes. We systematically evaluated dysregulation of the MTA family to clarify their clinical significance in gastric cancer (GC). One hundred and forty-five patients who underwent surgery for GC were evaluated. We analyzed the expression levels of the MTA family (MTA1, 2 and 3) by qPCR in GC tissue, and the MTA1 protein expression in primary cancer and matched normal mucosa (NM) was measured using immunohistochemical analysis. The expression of all the MTA family members was significantly increased in a stage-dependent manner, and elevated expression of all of the MTA family members was correlated with metastatic factors and prognosis in GC patients. Multivariate analysis revealed that MTA1 overexpression was an independent risk factor for survival. Especially, elevated expression of MTA1 was significantly correlated with recurrence, and was an independent risk factor for lymph node metastasis. Immunohistochemical analysis demonstrated that MTA1 was predominantly expressed in the nuclei of primary GC cells but was not expressed in NM and in the cancer stroma. In conclusion, quantification of MTA expression may support the accurate diagnosis of disease staging and may help predict clinical outcomes.

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.

MTA1--a stress response protein: a master regulator of gene expression and cancer cell behavior

Gene mutation's role in initiating carcinogenesis has been controversial, but it is consensually accepted that both carcinogenesis and cancer metastasis are gene-regulated processes. MTA1, a metastasis-associated protein, has been extensively researched, especially regarding its role in cancer metastasis. In this review, I try to elucidate MTA1's role in both carcinogenesis and metastasis from a different angle. I propose that MTA1 is a stress response protein that is upregulated in various stress-related situations such as heat shock, hypoxia, and ironic radiation. Cancer cells are mostly living in a stressful environment of hypoxia, lack of nutrition, and immune reaction attacks. To cope with all these stresses, MTA1 expression is upregulated, plays a role of master regulator of gene expression, and helps cancer cells to survive and migrate out of their original dwelling.

Molecular functions and significance of the MTA family in hormone-independent cancer

The members of the metastasis-associated protein (MTA) family play pivotal roles in both physiological and pathophysiological processes, especially in cancer development and metastasis, and their role as master regulators has come to light. Due to the fact that they were first identified as crucial factors in estrogen receptor-mediated breast cancer metastasis, most of the early studies focused on their hormone-dependent functions. However, the accumulating evidence shows that the members of MTA family are deregulated in most, if not all, the cancers studied so far. Therefore, the levels as well as the activities of the MTA family members are widely accepted as potential biomarkers for diagnosis, prognosis, and predictors of overall survival. They function differently in different cancers with specific mechanisms. p53 and HIF-1α appear to be the respectively common upstream and downstream regulator of the MTA family in both development and metastasis of a wide spectrum of cancers. Here, we review the expression and clinical significance of the MTA family, focusing on hormone-independent cancers. To illustrate the molecular mechanisms, we analyze the MTA family-related signaling pathways in different cancers. Finally, targeting the MTA family directly or the pathways involved in the MTA family indirectly could be invaluable strategies in the development of cancer therapeutics.

Properties and clinical relevance of MTA1 protein in human cancer

Among the genes that were found to be abundantly overexpressed in highly metastatic rat cell lines compared to poorly metastatic cell lines, we identified a completely novel complementary DNA (cDNA) without any homologous or related genes in the database in 1994. The full-length cDNA of this rat gene was cloned, sequenced, and named metastasis-associated gene 1 (mta1), and eventually, its human cDNA counterpart, MTA1, was also cloned and sequenced by our group. MTA1 has now been identified as one of the members of a gene family (MTA gene family) and the products of the MTA genes, the MTA proteins, are transcriptional co-regulators that function in histone deacetylation and nucleosome remodeling and have been found in nuclear histone remodeling complexes. Furthermore, MTA1 along with its protein product MTA1 has been repeatedly and independently reported to be overexpressed in a vast range of human cancers and cancer cell lines compared to non-cancerous tissues and cell lines. The expression levels of MTA1 correlate well with the malignant properties of human cancers, strongly suggesting that MTA1 and possibly other MTA proteins (and their genes) could be a new class of molecular targets for cancer diagnosis and therapy.

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.

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.

Metastasis-associated gene 1 promotes invasion and migration potential of laryngeal squamous cell carcinoma cells

Overexpression of the metastasis-associated gene 1 (MTA1) has previously been found to be associated with progression of various cancer types to the metastasis stage. The function of MTA1 in laryngeal squamous cell carcinoma (LSCC) remains unclear. To explore the significance of MTA1 in the invasion and migration processes in LSCC, gene transfection and RNA interference (RNAi) were performed to study the biological function of MTA1 in the LSCC cell line, HEP-2. Results showed that MTA1 promoted the invasion, adhesion and migration behavior of LSCC cells. RNAi against MTA1 significantly decreased the malignant phenotypes of cancer cells. MTA1 may be important in the process of LSCC invasion and metastasis.

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

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

Akt mediates metastasis-associated gene 1 (MTA1) regulating the expression of E-cadherin and promoting the invasiveness of prostate cancer cells

Human metastasis-associated gene 1 (MTA1) is highly associated with the metastasis of prostate cancer; however, the molecular functions of MTA1 that facilitate metastasis remain unclear. In this study, we demonstrate that the silencing of MTA1 by siRNA treatment results in the upregulation of E-cadherin expression by the phosphorylation of AKT (p-AKT) and decreases the invasiveness of prostate cancer cells. We show that MTA1 is expressed in over 90% of prostate cancer tissues, especially metastatic prostate cancer tissue, comparing to non-expression in normal prostate tissue. RT-PCR analysis and Western blot assay showed that MTA1 expression is significantly higher in highly metastatic prostate cancer PC-3M-1E8 cells (1E8) than in poorly metastatic prostate cancer PC-3M-2B4 cells (2B4). Silencing MTA1 expression by siRNA treatment in 1E8 cells increased the cellular malignant characters, including the cellular adhesive ability, decreased the cellular invasive ability and changed the polarity of cellular cytoskeleton. 1E8 cells over-expressing MTA1 had a reduced expression of E-cadherin, while 1E8 cells treated with MTA1 siRNA had a higher expression of E-cadherin. The expression of phosphorylated AKT (p-AKT) or the inhibition of p-AKT by wortmannin treatment (100 nM) significantly altered the function of MTA1 in the regulation of E-cadherin expression. Alterations in E-cadherin expression changed the role of p-AKT in cellular malignant characters. All of these results demonstrate that MTA1 plays an important role in controlling the malignant transformation of prostate cancer cells through the p-AKT/E-cadherin pathway. This study also provides a new mechanistic role for MTA1 in the regulation of prostate cancer metastasis.

Involvement of HER-2/neu and metastasis-related proteins in the development of ileal neuroendocrine tumors

HER-2/neu overexpression and/or gene amplification occurs in several human malignancies, frequently correlates with tumor aggressiveness, and provides the basis for treatment with trastuzumab. Among neuroendocrine neoplasms (NEN) of the gastroenteropancreatic (GEP) tract, ileal neuroendocrine tumors show peculiar features of malignancy with frequent metastases at the diagnosis. We investigated the overexpression and/or amplification of HER-2/neu and the involvement of the metastasis-related proteins c-Met, MTA-1, and VEGF in 24 primary ileal NEN by immunohistochemistry and fluorescence in situ hybridization (FISH). Data were compared with those of 43 GEP endocrine tumors of other sites. All primary ileal NEN showed an intense membranous and cytoplasmic immunostaining for HER-2/neu. According to the breast cancer scoring system, 17% of ileal carcinoids showed a score of 3+ and 71% with a score of 2+ with a significant difference respect the non-ileal GEP endocrine tumors (p < 0.0000). FISH analysis revealed chromosome 17 polysomy in 33% of 2+/3+ ileal tumors but not HER-2/neu gene amplification. The c-Met and MTA-1 but not VEGF were overexpressed in almost all ileal NEN, whereas VEGF presented more frequently a normal staining. The comparisons with the other GEP NEN demonstrated significant differences for all the three proteins (p < 0.0000, p < 0.0002, and p < 0.001, respectively). These findings suggest that in ileal NEN, HER-2/neu overexpression plays a role in the carcinogenetic process and by triggering the altered expression of c-Met and MTA-1, may activate the molecular pathway(s) promoting tumor progression and metastasis development. Ileal HER-2/neu overexpressing neuroendrocrine tumors may constitute potential candidates for target therapy with specific humanized monoclonal antibodies.

Targeting prostate cancer angiogenesis through metastasis-associated protein 1 (MTA1)

BACKGROUND

Metastasis-associated protein 1 (MTA1) is overexpressed in many forms of cancer types but its role in prostate cancer (PCa) progression and metastasis has not been explored. In this study, we addressed the functional and biological role of MTA1 in PCa.

METHODS

Gene expression profiling was used to determine MTA1 overexpression during PCa cell-bone interaction. Immunohistochemistry was used to detect MTA1 on tissue microarrays (TMA) and vascular endothelial growth factor (VEGF), CD31, and Ki67 in xenografts. We used retroviral or lentiviral RNAi transduction of PCa cells to establish MTA1 knockdowns. RT-PCR, Western blot, invasion, and endothelial cell migration assays were used to characterize the cells in vitro. The role of MTA1 in PCa tumorigenesis was evaluated in mouse xenografts.

RESULTS

We identified MTA1 as a component of bone metastasis signature in PCa, which suggested a possible role for MTA1 in PCa progression and metastasis. MTA1 was expressed at higher levels in PCa cell lines than in normal prostate epithelial cells. Silencing MTA1 significantly suppressed the invasion and angiogenic activity of the cells in vitro and delayed tumor formation and development in mouse xenografts. Tumors that express MTA1 had higher proliferative indices, secreted higher levels of VEGF and were more vascularized. Analysis of the human TMA showed positive correlation between MTA1 nuclear localization/staining intensity and PCa aggressiveness.

CONCLUSIONS

MTA1 pro-angiogenic and pro-invasive functions create permissive environment for PCa tumor growth and likely support metastasis. Taken together with its predictive values, MTA1 can be utilized both as a prognostic marker and a therapy target in PCa.

Silencing MTA1 by RNAi reverses adhesion, migration and invasiveness of cervical cancer cells (SiHa) via altered expression of p53, and E-cadherin/β-catenin complex

It has been reported that metastasis-associated gene 1 (Mta1) is overexpressed in many malignant tumors with high metastatic potential. In addition, some studies indicated that MTA1 participated in invasion, metastasis, and survival of cancer cells by regulating cell migration, adhesion and proliferation. But the role of MTA1 is unclear in vitro in the development of cervical cancer cells. This study investigated whether and how MTA1 mediated cell proliferation, migration, invasion and adhesion in cervical cancer. MTA1 expression level was detected by Western blot in two cervical cancer cell lines of different invasion potentials. The effects of MTA1 expression on SiHa cell apoptosis, cycle, proliferation, migration, invasion and adhesion were tested by flow cytometry, MTT, wound-healing assay, Transwell assay and adhesion assay, respectively. The expression levels of p53, E-cadherin, and β-catenin activity were evaluated in untreated and treated cells. The results showed that MTA1 protein expression was significantly higher in SiHa than in HeLa, which was correlated well with the potential of migration and invasion in both cell lines. Furthermore, the cell invasion, migration and adhesion capabilities were decreased after inhibition of MTA1 expression mediated by Mta1-siRNA transfection in SiHa. However, no significant differences were found in cell apoptosis, cycle, and proliferation. In addition, E-cadherin and p53 protein levels were significantly up-regulated, while β-catenin was significantly down-regulated in SiHa transfected with the siRNA. These results demonstrated that MTA1 played an important role in the migration and invasion of cervical cancer cells. It was speculated that the decreased migration and invasion capability by inhibiting the MTA1 expression in the SiHa cell line may be mediated through the altered expression of p53, and E-cadherin/β-catenin complex. MTA1 could serve as a potential therapeutic target in cervical cancer.

Metastasis-associated protein 1 nuclear expression is associated with tumor progression and clinical outcome in patients with non-small cell lung cancer

INTRODUCTION

Little research has been done to test the usefulness of metastasis-associated protein 1 (MTA1) as a prognostic marker for non-small cell lung cancer (NSCLC). In this study, we investigated MTA1 expression and its prognostic value for NSCLC.

METHODS

NSCLC surgical tissue samples were taken from 100 patients with NSCLC who had been followed up for more than 2 years. The expression of MTA1 protein was evaluated by immunohistochemistry, and the correlations between the expression of MTA1 and clinical features and the prognosis were analyzed. The difference of MTA1 protein expression between NSCLCs and their adjacent nonneoplastic lung tissues was analyzed in a tissue microarray. The change of MTA1 mRNA expression and protein expression after RNA interference (RNAi) was detected by real-time polymerase chain reaction, Western blot, and immunocytochemistry in NSCLC cell line 95D.

RESULTS

Overexpression of MTA1 (immunoreactivity scoring >4) was shown in 61.0% of the NSCLC cases but only in 9.4% of their adjacent nonneoplastic lung tissues (p < 0.001). The MTA1 expression level was correlated with lymph node metastasis (p = 0.013) and clinical stage (p = 0.002). Survival analysis showed that the MTA1 overexpression group had a significantly shorter overall survival time than the MTA1 downexpression group (p = 0.003). However, multivariate analysis showed that MTA1 expression was not a significant and independent prognostic parameter for patients with NSCLC. After RNAi, the 95D cells exhibit consistent reduction in MTA1 mRNA expression and MTA1 protein expression.

CONCLUSION

MTA1 protein expression is associated with tumor progression and clinical outcome in patients with NSCLC. Further molecular, cellular, and animal model studies on MTA1 gene will provide new clues for exploring the mechanism of carcinogenesis and tumor progression in patients with NSCLC.

Applications of RNA interference in cancer therapeutics as a powerful tool for suppressing gene expression

Cancer poses a tremendous therapeutic challenge worldwide, highlighting the critical need for developing novel therapeutics. A promising cancer treatment modality is gene therapy, which is a form of molecular medicine designed to introduce into target cells genetic material with therapeutic intent. The history of RNA interference (RNAi) has only a dozen years, however, further studies have revealed that it is a potent method of gene silencing that has developed rapidly over the past few years as a result of its extensive importance in the study of genetics, molecular biology and physiology. RNAi is a natural process by which small interfering RNA (siRNA) duplex directs sequence specific post-transcriptional silencing of homologous genes by binding to its complementary mRNA and triggering its elimination. RNAi has been extensively used as a novel and effective gene silencing tool for the fundamental research of cancer therapeutics, and has displayed great potential in clinical treatment.

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.

Overexpression of metastasis-associated MTA1 in oral squamous cell carcinomas: correlation with metastasis and invasion

Metastasis-associated protein 1 (MTA1) is physiologically expressed at low levels in human tissues. Its expression is associated with progression of solid cancers and is common in cancer cell lines. This study investigated whether MTA1 was expressed in squamous cell carcinoma (SCC) and would be a useful metastatic marker. Specimens from 38 patients with oral SCC were stained using the avidin-biotin-peroxidase technique with polyclonal antibodies against MTA1. Human SCC cell lines SAS, HSC2, OSC19 and OSC20 were analysed for MTA1 mRNA expression. MTA1 expression in control tissues was significantly lower than in carcinomas. MTA1 protein expression was detected in 33 of 38 SCC tissues from patients. Histologically, MTA1 protein production was strongly associated with cancer cell invasion, and clinically there was a correlation between lymph node metastasis and MTA1 protein production. Among the cancer cell lines, HSC2 showed the lowest mRNA expression, and OSC20 showed the highest MTA1 mRNA expression. In the Matrigel invasion assay, the HSC2 cell line showed the lowest invasion and the OSC20 cell line showed the highest invasion. RNAi-mediated MTA1 silencing in the OSC20 cells decreased the invasion index. MTA1 expression in oral SCC may be associated with increased invasive ability, which may cause lymph node metastasis.

MTA family of coregulators in nuclear receptor biology and pathology

Nuclear receptors (NRs) rely on coregulators (coactivators and corepressors) to modulate the transcription of target genes. By interacting with nucleosome remodeling complexes, NR coactivators potentiate transcription, whereas corepressors inhibit transcription of the target genes. Metastasis-associated proteins (MTA) represent an emerging family of novel NR coregulators. In general, MTA family members form independent nucleosome remodeling and deacetylation (NuRD) complexes and repress the transcription of different genes by recruiting histone deacetylases onto their target genes. However, MTA1 also acts as a coactivator in a promoter-context dependent manner. Recent findings that repression of estrogen receptor transactivation functions by MTA1, MTA1s, and MTA2 and regulation of MTA3 by estrogen signaling have indicated the significance of these proteins in NR signaling. Here, we highlight the action of MTA proteins on NR signaling and their roles in pathophysiological conditions.

Comprehensive analysis of the expression of the metastasis-associated gene 1 in human neoplastic tissue

CONTEXT

The metastasis-associated gene 1 (MTA1) is overexpressed in several human cancers. Recent reports suggest that MTA1 may play a role in cancer progression either through transcription repression and/or hormone receptor interactions.

OBJECTIVE

To analyze MTA1 expression levels in a wide variety of human tumors.

DESIGN

We used Oncomine, an Internet-based compendium of expression array data, to query more than 90 expression array studies, and we evaluated tissue microarrays composed of more than 3200 samples representing 138 different localized neoplasms.

RESULTS

Both analyses show that MTA1 is ubiquitously expressed in benign and malignant tumors. The highest levels of MTA1 expression were observed in diffuse B-cell lymphoma (mean staining intensity, 3.9/4), basal cell carcinomas (3.7/4), and consistently in tumors of neuroendocrine descent such as paraganglioma (3.7/4) and carcinoid tumor (3.1/4).

CONCLUSIONS

This study characterizes MTA1 expression for the first time across a broad spectrum of primary tumors, demonstrating expression in both benign and malignant neoplasms in addition to showing an association with neuroendocrine differentiation. We also found evidence that MTA1 expression is associated with tissue invasion but may not be sufficient for the progression to metastatic stages.

Expression of metastasis-associated protein 1 (MTA1) in benign endometrium and endometrial adenocarcinomas

Endometrial carcinoma is one of the most common malignancies of the female genital tract. Metastasis-associated protein 1 (MTA1) is a component of the Mi-2/nucleosome remodeling and deacetylating complex and acts as a potent corepressor of estrogen receptor in breast cancer cells. MTA1 expression has been demonstrated in various cancers but has never been explored in endometrial carcinoma. We investigated the expression profile of MTA1 in different stages of benign endometrium as well as in endometrial endometrioid adenocarcinoma using immunohistochemistry and Western blotting. In the proliferative and secretory phases, MTA1 was expressed in both the glandular and the stromal compartments and was localized in nucleus and cytoplasm of these cells. MTA1 expression in secretory phase was less prominent when compared with the proliferative phase. In postmenopausal sections, MTA1 staining was observed in both glandular and stromal compartments and was localized in both nucleus and cytoplasm. Western blot analysis of 6 tumor specimens showed increased expression of MTA1 in all the tumors analyzed. Immunohistochemical staining performed on tumor microarray containing 70 endometrial endometrioid adenocarcinomas of various grades showed increased expression of MTA1 in 53 (75.7%) tumors. In grade 1 and grade 2 tumors, MTA1 was present in both nucleus and cytoplasm. Interestingly, in grade 3 tumors, MTA1 was localized in the cytoplasm only. Our results suggest a potential role of MTA1 in endometrial carcinomas.

Reduced MTA1 expression by RNAi inhibits in vitro invasion and migration of esophageal squamous cell carcinoma cell line

To distinguish aggressive esophageal squamous cell carcinoma from indolent disease is the important clinical challenge. Studies have indicated that metastasis-associated gene 1(Mta1) played a role in the process of metastasis of carcinoma. The overexpression of Mta1 gene has been found in a variety of tumors. To identify the detailed roles of MTA1 protein in the carcinogenesis of esophageal squamous cell carcinoma, this study analyzed the pathological specimens on tissue microarray derived from 72 patients using immunohistochemistry. MTA1 expression increased in the nuclear with the development of esophageal squamous cell carcinoma from normal epithelial cell, dysplasia, to invasive cancer. In biological studies with human esophageal squamous cell carcinoma cell line, MTA1 plays its roles to promote cancer cell invasion, adhesion and movement. RNA interference (RNAi) against MTA1 decreased the malignant phenotypes. Gene microarray analysis revealed some metastasis-associated genes were altered by MTA1 RNAi. This study started an effective beginning to explore metastasis mechanisms and cancer gene therapy strategy targeting MTA1.

MTA1 overexpression correlates significantly with tumor grade and angiogenesis in human breast cancers

Metastasis associated antigen 1 (MTA1) is a recently identified candidate metastasis-associated gene that plays an important role in tumorigenesis and tumor aggressiveness, especially tumor invasiveness and metastasis. We analyzed the relationship between MTA1 expression and variable clinicopathological features and characterized its role in tumor angiogenesis in human breast cancers. Two hundred and sixty-three breast cancer cases that successfully underwent surgery at Hanyang University Hospital (Seoul, Korea) between January 1989 and December 1997 were enrolled. MTA1 expression was observed by immunohistochemical staining and correlated with intratumoral microvessel density (MVD) and other clinicopathological parameters. MTA1 overexpression correlated significantly with higher tumor grade (grades 1 and 2 vs grade 3, P = 0.009). However, MTA1 expression did not correlate with tumor stage, status of estrogen and progesterone receptors, or axillary lymph node metastasis. Interestingly, MTA1 expression was found to correlate significantly with tumor MVD (P = 0.002). Survival analysis did not show a significant difference between MTA1 overexpression and poorer survival. In conclusion, MTA1 overexpression was found to be closely associated with higher tumor grade and increased tumor angiogenesis. These findings suggest MTA1 as a predictor of aggressive phenotype and a possible target molecule for anti-angiogenic drugs in breast cancer treatment.

The role of Snf2-related proteins in cancer

Several HDAC inhibitors that exhibit impressive anti-tumour activity are now in clinical trials. Proteins that function in the same pathways might also serve as valuable therapeutic targets. A subset of histone deacetylase activities are found to be physically associated with ATP-dependent remodelling enzymes and may assist their function. This raises the possibility that ATP-dependent remodelling enzymes should be considered as therapeutic targets. Here some of the links between ATP-dependent chromatin remodelling enzymes and cancer are reviewed.

Breast tumors that overexpress nuclear metastasis-associated 1 (MTA1) protein have high recurrence risks but enhanced responses to systemic therapies

Nuclear metastasis-associated 1(MTA1) protein is an estrogen receptor co-repressor that regulates transcription via chromatin remodeling, and MTA1 messenger ribonucleic acid (mRNA) levels are elevated in several kinds of locally advanced and metastatic tumors relative to non-metastatic tumors. Previous studies in our laboratory mapped MTA1 into a region showing significantly lower LOH (loss of heterozygosity) in primary breast cancers with metastases compared to node-negative tumors, suggesting that epigenetic alterations of MTA1 affect metastatic potential. The present study examined immunohistochemical expression of the MTA1 protein in treated and untreated primary human breast cancers to study the relationship between MTA1 expression and clinical outcome. Node-negative tumors that overexpress MTA1 protein had recurrence risks similar to node-positive tumors. In multivariate analysis of untreated node-negative tumors, highest expression of MTA1 was associated with increased relapse risk (hazard ratio (HR)=2.72, p=0.0003 for multivariate analysis). Tamoxifen and/or anthracylcene-based chemotherapies eliminated all MTA1 associations with clinical outcome, suggesting MTA1 overexpression predicts early disease relapse, but sensitizes breast tumors to systemic therapies.

Overexpression of metastatic tumor antigen in osteosarcoma: comparison between conventional high-grade and central low-grade osteosarcoma

PURPOSE

The metastatic tumor antigen (MTA) gene is a recently identified metastasis-associated gene which has implications in the signal transduction or regulation of gene expression. However, the expression of MTA in osteosarcoma and its potential relationship with metastasis have not been examined, forming the basis of this study.

MATERIALS AND METHODS

We compared the expression levels of the MTA1 protein between 32 cases of high-grade osteosarcomas and 21 cases of low-grade osteosarcomas by immunohistochemistry. In addition, the mRNA expression levels of MTA1, 2, 3 in these osteosarcoma cell lines and control fibroblasts were evaluated by real-time quantitative PCR.

RESULTS

MTA1 immunoreactivity was present in 81.25% of high-grade osteosarcoma specimens. Its expression was predominantly localized to the nucleus or cytoplasm of osteosarcoma cells. Thirteen (86.6%) of 15 patients who died of osteosarcomas displayed strong MTA1 expression. Both primary bone and pulmonary metastatic lesions exhibited MTA1 expression. All low-grade osteosarcomas were negative for MTA1 except for focal weak reactivity in two cases. The tested high-grade osteosarcoma cell lines showed marked amplification of MTA1 and MTA2 mRNA compared to control cells.

CONCLUSION

These results suggest that MTA might be involved in the progression of high-grade osteosarcoma, particularly in hematogenous metastasis of osteosarcoma.

Histone deacetylase 1 mRNA expression in lung cancer

Histone deacetylases (HDACs) play a crucial role in tumorigenesis, however, the expression status of HDACs in lung cancer tissues has not been reported. We have investigated that HIDAC 1 mRNA levels and other clinico-pathological data, including MTA 1 mRNA expression in lung cancer. The study included 102 lung cancer cases. The HDAC1 mRNA levels were quantified by real time reverse transcription-polymerase chain reaction (RT-PCR) using LightCycler (Roche Molecular Biochemicals, Mannheim, Germany). The HDAC1/GAPDH mRNA levels were not significantly different in tumor tissues from lung cancer (30.654 +/- 33.047) and adjacent non-malignant lung tissues (18.953 +/- 56.176 , P = 0.1827). No significant difference in HDAC1/GAPDH mRNA levels was found among age, gender, and lymph node metastasis. The HDAC1/GAPDH mRNA levels were significantly higher in stage III or IV lung cancer (50.929 +/- 120.433) than in stage I lung cancer (11.430 +/- 25.611, P = 0.0472). HDAC1/GAPDH mRNA levels were significantly higher in T3 or T4 lung carcinoma (54.326 +/- 127.018) than in T1 or T2 lung cancers (14.790 +/- 48.670, P = 0.1601). HDAC1/GAPDH mRNA levels were correlated with MTA1/GAPDH mRNA levels (y = 0.0106x + 2.5827 , P = 0.0352 ). HDAC1/GAPDH mRNA levels were also correlated with HDAC1 protein (P = 0.0484) expression by immunohistochemistry. Using the LightCycler RT-PCR assay, the HDAC1 gene expression might correlate with progression of lung cancers. However, further studies are needed to confirm the impact of HDAC1 for the molecular target of the lung cancer.

Coregulators and chromatin remodeling in transcriptional control

Despite many years of investigation by numerous investigators, transcriptional regulatory control remains an intensely investigated and continuously evolving field of research. Transcriptional regulation is dependent not only on transcription factor activation and chromatin remodeling, but also on a host of transcription factor coregulators-coactivators and corepressors. In addition to transcription factor activation and chromatin changes, there is an expanding array of additional modifications that titrate transcriptional regulation for the specific conditions of a particular cell type, organ system, and developmental stage, and such events are likely to be greatly influenced by upstream signaling cascades. Here, we will briefly review the highlights and perspectives of chromatin remodeling and transcription controls as affected by cofactor availability, cellular energy state, relative ratios of reducing equivalents, and upstream signaling. We also present the C-terminal binding protein (CtBP) as a novel nuclear receptor (NR) coregulator, which exemplifies the integration of a number of transcriptional regulatory controls.

[Tissue microarrays. High-throughput procedures to verify potential biomarkers]

High-throughput molecular screening tools have created a need for equally rapid means to verify potential biomarkers. Tissue microarray (TMA) technology facilitates effective analysis on the protein level. Hundreds of 0.6-mm-diameter tissue samples are placed on a single standard glass slide. This approach allows analysis with different in situ methods of all tissue samples in one experiment under standardized conditions. TMAs are not only perfectly suited for molecular epidemiologic studies if applied on multitumor arrays composed of a variety of tumor entities, but they are also used for tumor-specific investigations of molecular markers. In this report the technical aspects of TMAs as a miniaturized high-throughput technology are described. We further demonstrate how the TMA technique will help to accelerate the transition from basic research to clinical application in prostate cancer disease.

Expression of the metastasis-associated MTA1 protein and its relationship to deacetylation of the histone H4 in esophageal squamous cell carcinomas

Metastasis-associated protein MTA1 and histone deacetylase form a protein complex with histone deacetylase activity that plays an important role in histone deacetylation, alteration of chromatin structure and transcriptional control. The precise role of the MTA1 protein in the malignant progression of human cancers remains unknown, however, especially its overexpression and relationship with histone acetylation/deacetylation in experimental and clinical tumors. The expression levels of MTA1 protein and the acetylation levels of histone H4 were examined in 70 cases of surgically resected esophageal squamous cell carcinomas, using immunohistochemistry. The intensities of immunostaining of MTA1 protein and acetylated histone H4 in carcinoma tissues (Ca) were compared to normal epithelium (N) contained in the same section. Thirty of 70 cases (42.9%) displayed overexpression of MTA1 protein (N < Ca). Cancers overexpressing MTA1 protein invaded deeper into the esophageal wall (p < 0.005) and showed significantly higher degrees of lymph node metastasis (p < 0.01), higher pathological stage, more lymphatic involvement and poorer prognosis (p < 0.05) than the remaining cases. The acetylation levels of histone H4 inversely correlated to the depth of cancer invasion and pathological stage (p < 0.05), and the patients with higher level of histone H4 acetylation had a better prognosis (p < 0.05). Furthermore, immunostaining patterns of MTA1 and acetylated histone H4 were inversely correlated (p < 0.001), demonstrating the relationship of deacetylation of histone H4 in MTA1-overexpressing carcinomas. In conclusion, the data suggest that the overexpression of MTA1 protein and acetylation level of histone H4 protein, both of which are closely related, might be useful predictors of malignant potential of esophageal squamous cell carcinomas. Thus, strategies involving inhibition of MTA1 function as well as inhibition of histone deacetylation could be novel approaches for the treatment of esophageal squamous cell carcinomas.

The Role of Metastasis-Associated Protein 1 in Prostate Cancer Progression

Distinguishing aggressive prostate cancer from indolent disease represents an important clinical challenge, as current therapy requires over treating men with prostate cancer to prevent the progression of a few cases. Expression of the metastasis-associated protein 1 (MTA1) has previously been found to be associated with progression to the metastatic state in various cancers. Analyzing DNA microarray data, we found MTA1 to be selectively overexpressed in metastatic prostate cancer compared with clinically localized prostate cancer and benign prostate tissue. These results were validated by demonstrating overexpression of MTA1 in metastatic prostate cancer by immunoblot analysis. MTA1 protein expression was evaluated by immunohistochemistry in a broad spectrum of prostate tumors with tissue microarrays containing 1940 tissue cores from 300 cases. Metastatic prostate cancer demonstrated significantly higher mean MTA1 protein expression intensity (score = 3.4/4) and percentage of tissue cores staining positive for MTA1 (83%) compared with clinically localized prostate cancer (score = 2.8/4, 63% positive cores) or benign prostate tissue (score = 1.5/4, 25% positive cores) with a mean difference of 0.54 and 1.84, respectively (P < 0.00001 for both). Paradoxically, for localized disease, higher MTA1 protein expression was associated with lower rates of prostate specific antigen recurrence after radical prostatectomy for localized disease. In summary, this study identified an association of MTA1 expression and prostate cancer progression.

Expression of MTA1 promotes motility and invasiveness of PANC-1 pancreatic carcinoma cells

The human metastasis-associated protein 1 (MTA1) is a constituent of the nucleosome-remodelling and -deacetylation complex. Its expression has been correlated with the invasion and metastasis of epithelial neoplasms. To address the functional consequences of MTA1 expression in pancreatic carcinoma cells, we have established PANC-1 pancreatic carcinoma cells that stably express MTA1 as an enhanced green fluorescent fusion protein (EGFP-MTA1). Here, we demonstrate that heterologous expression of EGFP-MTA1 markedly enhanced the cellular motility and the invasive penetration of epithelial barriers by the cells. Expression of EGFP-MTA1 had no effect on substrate-independent growth, but reduced substrate-dependent cell proliferation. In addition, the organisation of the cytokeratin filament system and the localisation of the actin cytoskeleton-associated protein IQGAP1 were distinctly altered in EGFP-MTA1-expressing cells. These results indicate that enhanced expression of MTA1 promotes the acquisition of an invasive, metastatic phenotype, and thus enhances the malignancy of pancreatic adenocarcinoma cells by modulation of the cytoskeleton.