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

The Therapeutic Efficacy and Mechanism of Action of Gnetin C, a Natural Compound from the Melinjo Plant, in a Preclinical Mouse Model of Advanced Prostate Cancer

The metastasis-associated protein 1/protein kinase B (MTA1/AKT) signaling pathway has been shown to cooperate in promoting prostate tumor growth. Targeted interception strategies by plant-based polyphenols, specifically stilbenes, have shown great promise against MTA1-mediated prostate cancer progression. In this study, we employed a prostate-specific transgenic mouse model with MTA1 overexpression on the background of phosphatase and tensin homolog (Pten) null (R26MTA1; Ptenf/f) and PC3M prostate cancer cells which recapitulate altered molecular pathways in advanced prostate cancer. Mechanistically, the MTA1 knockdown or pharmacological inhibition of MTA1 by gnetin C (dimer resveratrol) in cultured PC3M cells resulted in the marked inactivation of mammalian target of rapamycin (mTOR) signaling. In vivo, mice tolerated a daily intraperitoneal treatment of gnetin C (7 mg/kg bw) for 12 weeks without any sign of toxicity. Treatment with gnetin C markedly reduced cell proliferation and angiogenesis and promoted apoptosis in mice with advanced prostate cancer. Further, in addition to decreasing MTA1 levels in prostate epithelial cells, gnetin C significantly reduced mTOR signaling activity in prostate tissues, including the activity of mTOR-target proteins: p70 ribosomal protein S6 kinase (S6K) and eukaryotic translational initiation factor 4E (elF4E)-binding protein 1 (4EBP1). Collectively, these findings established gnetin C as a new natural compound with anticancer properties against MTA1/AKT/mTOR-activated prostate cancer, with potential as monotherapy and as a possible adjunct to clinically approved mTOR pathway inhibitors in the future.

Molecular Efficacy of Gnetin C as Dual-Targeted Therapy for Castrate-Resistant Prostate Cancer

SCOPE

Resistance of castrate-resistant prostate cancer (CRPC) to enzalutamide (Enz) involves the expression of constitutively active androgen receptor splice variant (AR-V7). In addition to altered AR pathways, CRPC is characterized by "non-AR-driven" signaling, which includes an overexpression of metastasis-associated protein 1 (MTA1). Combining natural compounds with anticancer drugs may enhance drug effectiveness while reducing adverse effects. In this study, the in vitro and in vivo anticancer effects of Gnetin C (GnC) alone and in combination with Enz against CRPC are examined.

METHODS AND RESULTS

The effects of GnC alone and in combination with Enz are assessed by cell viability, clonogenic survival, cell migration, and AR and MTA1 expression using 22Rv1 cells. The tumor growth in vivo is assessed by bioluminescent imaging, western blots, RT-PCR, and IHC. GnC alone and in combined treatment inhibit cell viability, clonogenic survival and migration, and AR and MTA1 expression in 22Rv1 cells. The underlying AR- and MTA1-targeted anticancer mechanisms of treatments in vivo involve inhibition of proliferation and angiogenesis, and induction of apoptosis.

CONCLUSION

The findings demonstrate that GnC alone and GnC combined with Enz effectively inhibits AR- and MTA1-promoted tumor-progression in advanced CRPC, which indicates its potential as a novel therapeutic approach for CRPC.

Gnetin C Intercepts MTA1-Associated Neoplastic Progression in Prostate Cancer

Nutritional chemoprevention is particularly suitable for prostate cancer. Gnetin C, a resveratrol dimer found abundantly in the melinjo plant (Gnetum gnemon), may possess more potent biological properties compared to other stilbenes. We examined the effects of gnetin C in a high-risk premalignant transgenic mouse model overexpressing tumor-promoting metastasis-associated protein 1 (MTA1) on the background of Pten heterozygosity (R26^MTA1; Pten^+/f; Pb-Cre⁺). Mice were fed diets supplemented with the following compounds: pterostilbene (70 mg/kg diet); gnetin C, high dose (70 mg/kg diet); and gnetin C, low dose (35 mg/kg diet). Prostate tissues were isolated after 17 weeks and examined for histopathology and molecular markers. Serum was analyzed for cytokine expression. Gnetin C-supplemented diets substantially delayed the progression of preneoplastic lesions compared to other groups. Prostate tissues from gnetin C-fed mice showed favorable histopathology, with decreased severity and number of prostatic intraepithelial neoplasia (PIN) foci, reduced proliferation, and angiogenesis. A decreased level of MTA1, concurrent with the trend of increasing phosphatase and tensin homolog expression and reduced interleukin 2 (IL-2) levels in sera, were also detected in gnetin C-fed mice. Importantly, gnetin C did not exert any visible toxicity in mice. Our findings demonstrate that a gnetin C-supplemented diet effectively blocks MTA1-promoted tumor progression activity in high-risk premalignant prostate cancer, which indicates its potential as a novel form of nutritional interception for prostate cancer chemoprevention.

LINC00491 Facilitates Tumor Progression of Lung Adenocarcinoma via Wnt/β-Catenin-Signaling Pathway by Regulating MTSS1 Ubiquitination

Background: Long non-coding RNAs have been reported to be involved in tumorigenesis and progression through different regulatory mechanisms. It has been reported that aberrantly expressed long non-coding RNA LINC00491 promotes malignancy in multiple tumors, while the role of LINC00491 in lung adenocarcinoma (LUAD) is little reported and the mechanism for regulating tumor progression has not been elucidated. Methods: RNA sequencing and the TCGA database were combined to screen differentially expressed lncRNAs that facilitate tumor progression. The expression level of LINC00491 was examined in LUAD clinical samples and in cell lines using RT-qPCR. In vitro experiments including colony formation assay, EdU assay, cell migration and invasion assay and wound healing assay, and in vivo experiments including xenografting subcutaneous tumors and lung metastasis models were performed to investigate the function of LINC00491 in LUAD tumor progressions. RNA pull-down, mass spectrometry, RIP assays and truncation experiments were carried out to explore the proteins binding to LINC00491 and the specific interactions between the RNA-protein complex. Results: Our results showed that LINC0491 was significantly upregulated in LUAD and positively correlated with poor survival. High LINC00491 expression promoted proliferation, migration and invasion, and resulted in a high metastatic burden in LUAD. Using pull-down assay and mass spectrometry, MTSS1 was found binding to LINC00491, and the conducted experiments verified the direct interaction between LINC00491 and MTSS1. Meanwhile, LINC00491 was found to regulate MTSS1 degradation by promoting the MTSS1 ubiquitination level and then activating the Wnt/β-catenin-signaling pathway. LINC00491/MTSS1/β-catenin may act as a complex to facilitate tumor progression. Conclusions: In summary, our results found a novel mechanism in which LINC00491 directly interacts with MTSS1 by affecting its ubiquitination modification to promote LUAD proliferation, migration and invasion, then activating the Wnt/β-catenin-signaling pathway, demonstrating its significant role in tumor progression and suggesting that the LINC00491/MTSS1/Wnt/β-catenin-signaling pathway could serve as a potential therapeutic target for lung adenocarcinoma in the future.

Dietary stilbenes as modulators of specific miRNAs in prostate cancer

Accumulated experimental data have suggested that natural plant products may be effective miRNA-modulating chemopreventive and therapeutic agents. Dietary polyphenols such as flavonoids, stilbenes, and lignans, among others, have been intensively studied for their miRNA-mediated cardioprotective, antioxidant, anti-inflammatory and anticancer properties. The aim of this review is to outline known stilbene-regulated miRNAs in cancer, with a special focus on the interplay between various miRNAs and MTA1 signaling in prostate cancer. MTA1 is an epigenetic reader and an oncogenic transcription factor that is overexpressed in advanced prostate cancer and metastasis. Not surprisingly, miRNAs that are linked to MTA1 affect cancer progression and the metastatic potential of cells. Studies led to the identification of MTA1-associated pro-oncogenic miRNAs, which are regulated by stilbenes such as resveratrol and pterostilbene. Specifically, it has been shown that inhibition of the activity of the MTA1 regulated oncogenic miR-17 family of miRNAs, miR-22, and miR-34a by stilbenes leads to inhibition of prostatic hyperplasia and tumor progression in mice and reduction of proliferation, survival and invasion of prostate cancer cells in vitro. Taken together, these findings implicate the use of resveratrol and its analogs as an attractive miRNA-mediated chemopreventive and therapeutic strategy in prostate cancer and the use of circulating miRNAs as potential predictive biomarkers for clinical development.

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

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

Dietary Pterostilbene for MTA1-Targeted Interception in High-Risk Premalignant Prostate Cancer

Prostate cancer remains one of the most prevalent cancers in aging men. Active surveillance subpopulation of patients with prostate cancer includes men with varying cancer risk categories of precancerous disease due to prostatic intraepithelial neoplasia (PIN) heterogeneity. Identifying molecular alterations associated with PIN can provide preventable measures through finding novel pharmacologic targets for cancer interception. Targeted nutritional interception may prove to be the most appropriate chemoprevention for intermediate- and high-risk active surveillance patients. Here, we have generated two prostate-specific transgenic mouse models, one overexpressing MTA1 (R26MTA1 ) and the other overexpressing MTA1 on the background of Pten heterozygosity (R26MTA1 ; Pten+/f ), in which we examined the potential chemopreventive efficacy of dietary pterostilbene. We show that MTA1 promotes neoplastic transformation of prostate epithelial cells by activating cell proliferation and survival, leading to PIN development. Moreover, MTA1 cooperates with PTEN deficiency to accelerate PIN development by increasing cell proliferation and MTA1-associated signaling. Further, we show that mice fed with a pterostilbene-supplemented diet exhibited more favorable histopathology with decreased severity and number of PIN foci accompanied by reduced proliferation, angiogenesis, and inflammation concomitant to reduction in MTA1 and MTA1-associated CyclinD1, Notch2, and oncogenic miR-34a and miR-22 levels. PREVENTION RELEVANCE: Developing novel interceptive strategies for prostate cancer chemoprevention is a paramount goal in clinical oncology. We offer preclinical evidence for the potential of pterostilbene as a promising natural agent for MTA1-targeted interceptive strategy in future cancer prevention trials towards protecting select patients with prostate cancer under active surveillance from developing cancer.

MTA1: A Vital Modulator in Prostate Cancer

Prostate cancer (PCa) is the most frequent cancer of the male genitourinary system and the second most common cancer in men worldwide. PCa has become one of the leading diseases endangering men's health in Asia in recent years, with a large increase in morbidity and mortality. MTA1 (metastasis-associated antigen-1), a transcriptional coregulator involved in histone deacetylation and nucleosome remodeling, is a member of the MTA family. MTA1 is involved in cell signaling, chromosomal remodeling, and transcriptional activities, all of which are important for epithelial cell progression, invasion, and growth. MTA1 has been demonstrated to play a significant role in the formation, progression, and metastasis of PCa, and MTA1 expression is specifically linked to PCa bone metastases. Therefore, MTA1 may be a potential target for PCa prevention and treatment. Here, we reviewed the structure, function, and expression of MTA1 in PCa as well as drugs that target MTA1 to highlight a potential new treatment for PCa.

Role of specialized composition of SWI/SNF complexes in prostate cancer lineage plasticity

Advanced prostate cancer initially responds to hormonal treatment, but ultimately becomes resistant and requires more potent therapies. One mechanism of resistance observed in around 10–20% of these patients is lineage plasticity, which manifests in a partial or complete small cell or neuroendocrine prostate cancer (NEPC) phenotype. Here, we investigate the role of the mammalian SWI/SNF (mSWI/SNF) chromatin remodeling complex in NEPC. Using large patient datasets, patient-derived organoids and cancer cell lines, we identify mSWI/SNF subunits that are deregulated in NEPC and demonstrate that SMARCA4 (BRG1) overexpression is associated with aggressive disease. We also show that SWI/SNF complexes interact with different lineage-specific factors in NEPC compared to prostate adenocarcinoma. These data point to a role for mSWI/SNF complexes in therapy-related lineage plasticity, which may also be relevant for other solid tumors.

The differentiation of prostate adenocarcinoma to neuroendocrine prostate cancer (CRPC-NE) is a mechanism of resistance to androgen deprivation therapy. Here the authors show that SWI/SNF chromatin-remodeling complex is deregulated in CRPC-NE and that the complex interacts with different lineage specific factors throughout prostate cancer transdifferentiation.

MTA1 promotes the invasion and migration of pancreatic cancer cells potentially through the HIF-α/VEGF pathway

The metastasis-associated gene 1 (MTA1) has previously been recognized as an oncogene, and abnormal MTA1 expression has been related to progression of numerous cancer types to the metastasis stage. However, the function of MTA1 in the regulation of pancreatic cancer progression and metastasis remains unclear. Western blot analysis was adopted to determine the expression of MTA1 in pancreatic cancer tissues and corresponding near normal tissues. Steady clone with MTA1-overexpression and MTA1-inhibitionweregenerated via lentivirus technology in BxPc-3 cells. Transwell assay was carried out for detecting the invasion of pancreatic cancer cells. The migration activity was assessed using the wound scratch assay. The effect of MTA1 in pancreatic cancer was evaluated in the mice xenografts. Western blot analysis was employed to determine the expression of hypoxia inducible factor-α (HIF-α) and vascular endothelial growth factor (VEGF) in vitro and in vivo. We observed that MTA1 overexpression enhanced migration and invasion ability of pancreatic cancer cells in vitro and increased HIF-α and VEGF protein levels in vitro and in vivo. MTA1 inhibition had the opposite effects. MTA1 protein level was positively related to HIF-α and VEGF protein levels. These results indicated that MTA1 potentially promoted pancreatic cancer metastasis via HIF-α/VEGF pathway. This research supplies a new molecular mechanism for MTA1 in the pancreatic cancer progression and metastasis. MTA1 may be an effective therapy target in pancreatic cancer.

Metastasis-associated protein 1 (MTA1) in gastric cancer tissues is positively associated with poorer prognosis

BACKGROUND

The present study examined the clinical significance of metastasis-associated protein 1 (MTA1) in the progression and patient survival of gastric cancer.

METHODS

Paraffin-embedded resected tissues of gastric cancer mucosa (n = 436) and adjacent normal mucosa (n = 92) were assessed immunohistochemically for MTA1 protein, and scored according to the percentage of cells positively stained for MTA1 combined with stain intensity. Associations between MTA1 staining scores and clinicopathological factors, including survival time, were evaluated.

RESULTS

The staining scores for MTA1 were significantly higher in gastric cancer tissues than in matched normal tissues. MTA1 scores positively correlated with tumor size, depth of invasion, presence of lymph node metastasis, lymphatic involvement, venous invasion, distal metastasis, and advanced clinical staging. Patients with high MTA1 scores in gastric cancer tissues had a significantly lower five-year survival rate compared with patients with low MTA1 scores. The multivariate analysis indicated that MTA1 protein levels in resected gastric cancer tissues, as reflected by immunohistochemical staining, are an independent prognostic index of gastric carcinoma (P < 0.01).

CONCLUSION

MTA1 immunopositivity was significantly associated with progression of gastric cancer, and may be helpful in gastric cancer prognosis.

MTSS1 and SCAMP1 cooperate to prevent invasion in breast cancer

Cell-cell adhesions constitute the structural "glue" that retains cells together and contributes to tissue organisation and physiological function. The integrity of these structures is regulated by extracellular and intracellular signals and pathways that act on the functional units of cell adhesion such as the cell adhesion molecules/adhesion receptors, the extracellular matrix (ECM) proteins and the cytoplasmic plaque/peripheral membrane proteins. In advanced cancer, these regulatory pathways are dysregulated and lead to cell-cell adhesion disassembly, increased invasion and metastasis. The Metastasis suppressor protein 1 (MTSS1) plays a key role in the maintenance of cell-cell adhesions and its loss correlates with tumour progression in a variety of cancers. However, the mechanisms that regulate its function are not well-known. Using a system biology approach, we unravelled potential interacting partners of MTSS1. We found that the secretory carrier-associated membrane protein 1 (SCAMP1), a molecule involved in post-Golgi recycling pathways and in endosome cell membrane recycling, enhances Mtss1 anti-invasive function in HER2+/ER-/PR- breast cancer, by promoting its protein trafficking leading to elevated levels of RAC1-GTP and increased cell-cell adhesions. This was clinically tested in HER2 breast cancer tissue and shown that loss of MTSS1 and SCAMP1 correlates with reduced disease-specific survival. In summary, we provide evidence of the cooperative roles of MTSS1 and SCAMP1 in preventing HER2+/ER-/PR- breast cancer invasion and we show that the loss of Mtss1 and Scamp1 results in a more aggressive cancer cell phenotype.

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.

The Role and Mechanism of Epithelial-to-Mesenchymal Transition in Prostate Cancer Progression

In prostate cancer (PCa), similar to many other cancers, distant organ metastasis symbolizes the beginning of the end disease, which eventually leads to cancer death. Many mechanisms have been identified in this process that can be rationalized into targeted therapy. Among them, epithelial-to-mesenchymal transition (EMT) is originally characterized as a critical step for cell trans-differentiation during embryo development and now recognized in promoting cancer cells invasiveness because of high mobility and migratory abilities of mesenchymal cells once converted from carcinoma cells. Nevertheless, the underlying pathways leading to EMT appear to be very diverse in different cancer types, which certainly represent a challenge for developing effective intervention. In this article, we have carefully reviewed the key factors involved in EMT of PCa with clinical correlation in hope to facilitate the development of new therapeutic strategy that is expected to reduce the disease mortality.

Associations between the expression of MTA1 and VEGF-C in esophageal squamous cell carcinoma with lymph angiogenesis and lymph node metastasis

The aim of the present study was to investigate the association between the expression levels of metastasis-related gene 1 (MTA1) and vascular endothelial growth factor C (VEGF-C) in esophageal squamous cell carcinoma (ESCC) with lymph angiogenesis and lymph node metastasis. The paraffin-embedded tissue samples of 107 cases of ESCC and 56 cases of normal esophageal tissues were collected from the Department of Cardiothoracic Surgery, Suining Central Hospital from March 2013 to January 2014. Immunohistochemical assays were performed to detect the expression levels of MTA1, VEGF-C and D2-40 in ESCC, and the micro-lymphatic vessel density (LVD) was evaluated. Their associations with various clinicopathological parameters were also analyzed. The protein expression levels of MTA1 and VEGF-C in ESCC were significantly higher compared with those in normal esophageal tissues (P<0.05); the high protein expression levels of MTA1 and VEGF-C in ESCC tissues at various tumor-node-metastasis stages exhibited statistically significant differences, as revealed by the Kruskal-Wallis test (P<0.05). The protein expression levels of MTA1 and VEGF-C in ESCC exhibited positive correlations (Spearman's ρ, r=0.512; P=0.000); the LVD level in the group with high expression of MTA1 and VEGF-C was significantly higher compared with in the low expression group (P<0.05). The comparison between MTA1 and VEGF-C protein expression levels in the group with a high rate of lymph node metastasis demonstrated statistically significant differences when compared with in the low lymph node metastasis group (P<0.05). The expression levels of MTA1 and VEGF-C in ESCC exhibited a positive correlation in ESCC, which may co-promote lymph angiogenesis and lymph node metastasis in ESCC; therefore, they may be used as biomarkers for determining the prognosis of ESCC.

Dietary pterostilbene is a novel MTA1-targeted chemopreventive and therapeutic agent in prostate cancer

Overexpression of the epigenetic modifier metastasis-associated protein 1 (MTA1) is associated with aggressive human prostate cancer. The purpose of this study was to determine MTA1- targeted chemopreventive and therapeutic efficacy of pterostilbene, a natural potent analog of resveratrol, in pre-clinical models of prostate cancer. Here, we show that high levels of MTA1 expression in Pten-loss prostate cooperate with key oncogenes, including c-Myc and Akt among others, to promote prostate cancer progression. Loss-of-function studies using human prostate cancer cells indicated direct involvement of MTA1 in inducing inflammation and epithelial-to-mesenchymal transition. Importantly, pharmacological inhibition of MTA1 by pterostilbene resulted in decreased proliferation and angiogenesis and increased apoptosis. This restrained prostatic intraepithelial neoplasia (PIN) formation in prostate-specific Pten heterozygous mice and reduced tumor development and progression in prostate-specific Pten-null mice. Our findings highlight MTA1 as a key upstream regulator of prostate tumorigenesis and cancer progression. More significantly, it offers pre-clinical proof for pterostilbene as a promising lead natural agent for MTA1-targeted chemopreventive and therapeutic strategy to curb prostate cancer.

Epigenomic regulation of oncogenesis by chromatin remodeling

Disruption of the intricate gene expression program represents one of major driving factors for the development, progression and maintenance of human cancer, and is often associated with acquired therapeutic resistance. At the molecular level, cancerous phenotypes are the outcome of cellular functions of critical genes, regulatory interactions of histones and chromatin remodeling complexes in response to dynamic and persistent upstream signals. A large body of genetic and biochemical evidence suggests that the chromatin remodelers integrate the extracellular and cytoplasmic signals to control gene activity. Consequently, widespread dysregulation of chromatin remodelers and the resulting inappropriate expression of regulatory genes, together, lead to oncogenesis. We summarize the recent developments and current state of the dysregulation of the chromatin remodeling components as the driving mechanism underlying the growth and progression of human tumors. Because chromatin remodelers, modifying enzymes and protein-protein interactions participate in interpreting the epigenetic code, selective chromatin remodelers and bromodomains have emerged as new frontiers for pharmacological intervention to develop future anti-cancer strategies to be used either as single-agent or in combination therapies with chemotherapeutics or radiotherapy.

Portulacerebroside A inhibits adhesion, migration, and invasion of human leukemia HL60 cells and U937 cells through the regulation of p38/JNK signaling pathway

Acute myeloid leukemia (AML) is a highly malignant hematopoietic tumor. This study aimed to explore the effect of portulacerebroside A (PCA) on the adhesion, migration, and invasion in human leukemia HL60 cells and U937 cells and clarify the possible mechanisms involved, which could provide potential strategies for the treatment of AML. By methyl thiazolyl tetrazolium analysis, it was found that PCA (1-10 μM) suppressed the cell viability in a time- and dose-dependent manner. A total of 1, 2, and 5 μM of PCA dramatically inhibited the adhesion, migration, and invasion of HL60 cells and U937 cells in a dose-dependent manner. Phosphorylation level of JNK and P38 protein level was measured by Western blot. After the real-time quantification polymerase chain reaction and Western blot detection of the total RNA and protein, messenger RNA, and protein expression levels of Ras homologous C (RhoC), metastasis-associated gene 1 (MTA1) and matrix metalloproteinase-2/9 (MMP-2/9) were decreased significantly in a dose-dependent manner. The phosphorylation level of c-Jun N-terminal kinase (JNK) and P38 mitogen-activated protein kinase (P38) was decreased dramatically in HL60 cells and U937 cells after PCA treatment. In conclusion, PCA significantly inhibits the adhesion, migration, and invasion of HL60 cells and U937 cells by suppressing the p38/JNK pathway and regulating the expressions of related genes.

MTA1 promotes metastasis of MPM via suppression of E-cadherin

BACKGROUND

Metastasis-associated gene 1(MTA1) has been identified as an oncogene in many tumors, and aberrant MTA1 expression has been linked to carcinogenesis and metastasis. We aim to investigate the mechanism of MTA1 and metastasis in malignant pleural mesothelioma (MPM).

METHODS

Real-time polymerase chain reaction (PCR) and immunohistochemical staining were employed to detect MTA1 and E-cadherin expression in MPM tissues and corresponding adjacent tissues. Stable clone with knock-down of MTA1 was generated with shRNA via lentivirus technology in MPM cell lines. Wound-healing assay, transwell assay and PCR array were carried out for detecting invasion and migration of MPM cells. Luciferase reporter assay was performed to validate the effect of MTA1 on E-cadherin.

RESULTS

MTA1 expression is up-regulated in MPM and shown a negative correlation with E-cadherin expression. MTA1 could enhance the invasion and migration of MPM cells via suppressing the expression of E-cadherin. MTA1 overexpression is associated with pathology, metastasis and survival rate of MPM patients.

CONCLUSIONS

MTA1 plays an important role in Epithelial-to-mesenchymal transition (EMT) to promote metastasis via suppressing E-cadherin expression, resulting in a poor prognosis in MPM. MTA1 is a novel biomarker and indicative of a poor prognosis in MPM patients.

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.

Inhibition of invasion and metastasis of human liver cancer HCCLM3 cells by portulacerebroside A

CONTEXT

Portulacerebroside A (PCA) is a novel cerebroside compound isolated from Portulaca oleracea L. (Portulacaceae), an edible and medicinal plant distributed in the temperate and tropical zones worldwide.

OBJECTIVE

This study investigates the effects of PCA in human liver cancer HCCLM3 cells on metastasis and invasion.

MATERIALS AND METHODS

After the cells were treated with PCA (2.5, 5, and 10 μg/ml) for 6, 12, 24, or 48 h, adhesion, transwell invasion, and scratch tests were conducted and cell functions were evaluated. Western blot and FQ-RT-PCR assays explored the mechanism of PCA-inhibited invasion and metastasis in the cells.

RESULTS

The adhesion rate of the cells was suppressed at 0.5 h (79.4 ± 1.0, 68.7 ± 1.3, and 58.1 ± 1.3%, versus 100 ± 1.5% in the control), 1 h (78.2 ± 1.2, 70.9 ± 1.6, and 55.4 ± 1.9%, versus 100 ± 1.2% in the control), and 1.5 h (71.6 ± 1.1, 62.3 ± 0.9, and 50.4 ± 0.9%, versus 100 ± 1.1% in the control). The 24 h invasion ability was decreased (356.6 ± 11.2, 204.0 ± 17.6, and 113.0 ± 9.5%, versus 443.6 ± 15.4% in the control). The migration capability was also restrained by PCA for 24 h (324.8 ± 25.4, 250.4 ± 21.0, and 126.3 ± 10.1, versus 381.6 ± 30.6 in the control) and 48 h (470.3 ± 34.3, 404.0 ± 19.7, and 201.0 ± 15.4, versus 752.0 ± 63.6 in the control). There was an increase in the mRNA and protein expression levels of TIMP-2 and nm23-H1, inhibition in the mRNA expression of MTA1, MMP-2, and MMP-9, and suppression in the protein expression of MTA1, RhoA, Rac1/Cdc42, MMP-2, but not RhoC and MMP-9.

CONCLUSION

PCA suppresses the invasion and metastasis of HCCLM3 cells possibly by modulation of the mRNA and protein expression of related parameters. This is the first study to reveal a new potential therapeutic application of PCA in antimetastatic therapy for liver cancer.

Resveratrol regulates PTEN/Akt pathway through inhibition of MTA1/HDAC unit of the NuRD complex in prostate cancer

Metastasis associated protein 1 (MTA1) is a component of the nucleosome remodeling and deacetylating (NuRD) complex which mediates gene silencing and is overexpressed in several cancers. We reported earlier that resveratrol, a dietary stilbene found in grapes, can down-regulate MTA1. In the present study, we show that PTEN is inactivated by MTA1 in prostate cancer cells. Further, we show that resveratrol promotes acetylation and reactivation of PTEN via inhibition of the MTA1/HDAC complex, resulting in inhibition of the Akt pathway. In addition, we show that MTA1 knockdown is sufficient to augment acetylation of PTEN indicating a crucial role of MTA1 itself in the regulation of PTEN acetylation contributing to its lipid phosphatase activity. Acetylated PTEN preferentially accumulates in the nucleus where it binds to MTA1. We also show that MTA1 interacts exclusively with PTEN acetylated on Lys¹²⁵ and Lys¹²⁸, resulting in diminished p-Akt levels. Finally, using orthotopic prostate cancer xenografts, we demonstrate that both resveratrol treatment and MTA1 knockdown enhance PTEN levels leading to a decreased p-Akt expression and proliferation index. Taken together, our results indicate that MTA1/HDAC unit is a negative regulator of PTEN which facilitates survival pathways and progression of prostate cancer and that resveratrol can reverse this process through its MTA1 inhibitory function.

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.

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.

Significance of MTA1 in the molecular characterization of osteosarcoma

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

Metastatic tumor antigen in hepatocellular carcinoma: golden roads toward personalized medicine

Hepatocellular carcinoma (HCC), a prototype of hypervascular tumors, is one of the most common malignancies in the world, especially hyperendemic in the Far East where chronic hepatitis B virus (HBV) infection is highly prevalent. It is characterized by the clinical feature of a poor prognosis or a high mortality due to its already far advanced stages at diagnosis. It is so multifactorial that hepatocarcinogenesis cannot be explained by a single molecular mechanism. To date, a number of pathways have been known to contribute to the development, growth, angiogenesis, and even metastasis of HCC. Among the various factors, metastatic tumor antigens (MTAs) or metastasis-associated proteins have been vigorously investigated as an intriguing target in the field of hepatocarcinogenesis. According to recent studies including ours, MTAs are not only involved in the HCC development and growth (molecular carcinogenesis), but also closely associated with the post-operative recurrence and a poor prognosis or a worse response to post-operative anti-cancer therapy (clinical significance). Herein, we review MTAs in light of their essential structure, functions, and molecular mechanism in hepatocarcinogenesis. We will also focus in detail on the interaction between hepatitis B x protein (HBx) of HBV and MTA in order to clarify the HBV-associated HCC development. Finally, we will discuss the prognostic significance and clinical application of MTA in HCC. We believe that this review will help clinicians to understand the meaning and use of the detection of MTA in order to more effectively manage their HCC patients.

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.

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

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

Impact of histone deacetylase 1 and metastasis-associated gene 1 expression in esophageal carcinogenesis

Animal models are important for the development of novel therapies for esophageal cancer. Histone deacetylase 1 (HDAC1)/metastasis-associated gene (MTA1) complexes inhibit p53 acetylation and thus, inhibit p53-induced apoptosis. The aim of the present study was to evaluate HDAC1 and MTA1 expression in esophageal carcinogenesis in rats. The rats underwent a total gastrectomy followed by esophagojejunostomy to induce chronic duodenal content reflux esophagitis. The rats were sacrificed sequentially at 20, 30, 40 and 50 weeks post-surgery and the esophagi were examined. Immunohistochemical analysis was conducted to assess the expression and localization of HDAC1 and MTA1. At 20 weeks post-surgery, squamous proliferative hyperplasia and Barrett’s metaplasia (BM) were observed. While, adenocarcinoma-associated BM and squamous cell carcinoma were observed at 30–50 weeks post-surgery. The nuclear expression of HDAC1 and MTA1 was observed in all of the stages of squamous carcinogenesis and adenocarcinogenesis, although not in the normal esophageal epithelium. The expression of HDAC1 and MTA1 may be involved in duodenoesophageal reflux-induced neoplastic transformation of the esophageal mucosa into cancer cells with squamous and adeno differentiation.

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.

MiR-495 regulates proliferation and migration in NSCLC by targeting MTA3

Our previous studies have showed that metastasis-associated protein 3 (MTA 3) is overexpressed in non-small cell lung cancer (NSCLC) tissue, and increased MTA3 mRNA levels is a risk factor of lymph node metastasis. Using bioinformatics analyses, we found that MTA3 was a potential target of miR-495. However, the pathophysiological role of miR-495 and its relevance to the growth and development of NSCLC have yet to be investigated. The purpose of this study was to elucidate the molecular mechanisms by which miR-495 acts as a tumor suppressor in NSCLC. qRT-PCR data showed significant downregulation of miR-495 in 56 NSCLC tissue samples and 5 lung cancer cell lines, compared with their adjacent normal tissue; furthermore, western blotting analysis revealed MTA3 protein was overexpressed in the tumor samples compared with the matched adjacent normal tissue. MiR-495 was shown to not only inhibit the proliferation of lung cancer cells (A549 and Calu-3) but also to inhibit cell migration in vitro. Using western blotting and luciferase assays, MTA3 was identified as a target of miR-495. These findings suggest the importance of miR-495 targeting of MTA3 in the regulation of lung cancer growth and migration.

Metastasis-associated protein 1 is a novel marker predicting survival and lymph nodes metastasis in cervical cancer

Metastasis-associated gene 1 (MTA1), which is involved in tumor progression, metastasis, and angiogenesis, has been examined in several malignant tumors. However, the expression and the effect of MTA1 on human cervical cancer remain unknown. In this study, we investigated the level of MTA1 expression in cervical carcinoma and its clinical significance. By immunohistochemical staining, the correlation of MTA1 overexpression with clinical features and patient outcome was analyzed in 132 formalin-fixed, paraffin-embedded cervical cancer tissues. MTA1 protein overexpression was detected in 73 (55.3%) of 132 patients. High levels of MTA1 protein were clearly correlated with histologic grade (P = .006), lymph node metastasis (P = .001), and recurrence (P = .016). Multivariate Cox analysis showed that MTA1 was an independent factor for overall survival (hazard ratio, 3.486; 95% confidence interval [CI], 1.274-9.537; P = .015) and disease-free survival (hazard ratio, 3.373; 95% CI, 1.212-9.387; P = .020). Multivariate logistic regression analysis indicated that elevated MTA1 was strongly associated with lymph node metastasis (odds ratio, 3.879; 95% CI, 1.391-10.816; P = .010). Sensitivity and specificity were calculated as 81.25% and 53.0%, respectively. These findings suggest that MTA1 nuclear overexpression is associated with tumor progression and metastasis and thus support its clinical significance in future gene-targeted therapies, particularly the management of patients with cervical cancer.

Repression of NR4A1 by a chromatin modifier promotes docetaxel resistance in PC-3 human prostate cancer cells

Epigenetic silencing mechanisms play an important role in chemoresistance of human cancer. Here we report the upregulated expression of metastasis-associated protein 1 (MTA1), a component of the nucleosome remodeling deacetylation (NuRD) complex, in chemoresistant prostate cancer (PCa). MTA1 knockdown in PC-3 cells inhibited cell proliferation and enhanced docetaxel (DTX)-induced cell death. Conversely, overexpression of MTA1 promotes DTX chemoresistance in PC-3 cells. MTA1 acted as a potent corepressor of the nuclear receptor NR4A1 transcription by interacting with histone deacetylase 2 (HDAC2). These findings suggest that MTA1 may serve as a novel DTX-resistance promoter in PC-3 cells.

Pterostilbene acts through metastasis-associated protein 1 to inhibit tumor growth, progression and metastasis in prostate cancer

The development of natural product agents with targeted strategies holds promise for enhanced anticancer therapy with reduced drug-associated side effects. Resveratrol found in red wine, has anticancer activity in various tumor types. We reported earlier on a new molecular target of resveratrol, the metastasis-associated protein 1 (MTA1), which is a part of nucleosome remodeling and deacetylation (NuRD) co-repressor complex that mediates gene silencing. We identified resveratrol as a regulator of MTA1/NuRD complex and re-activator of p53 acetylation in prostate cancer (PCa). In the current study, we addressed whether resveratrol analogues also possess the ability to inhibit MTA1 and to reverse p53 deacetylation. We demonstrated that pterostilbene (PTER), found in blueberries, had greater increase in MTA1-mediated p53 acetylation, confirming superior potency over resveratrol as dietary epigenetic agent. In orthotopic PCa xenografts, resveratrol and PTER significantly inhibited tumor growth, progression, local invasion and spontaneous metastasis. Furthermore, MTA1-knockdown sensitized cells to these agents resulting in additional reduction of tumor progression and metastasis. The reduction was dependent on MTA1 signaling showing increased p53 acetylation, higher apoptotic index and less angiogenesis in vivo in all xenografts treated with the compounds, and particularly with PTER. Altogether, our results indicate MTA1 as a major contributor in prostate tumor malignant progression, and support the use of strategies targeting MTA1. Our strong pre-clinical data indicate PTER as a potent, selective and pharmacologically safe natural product that may be tested in advanced PCa.

Nuclear MTA1 overexpression is associated with aggressive prostate cancer, recurrence and metastasis in African Americans

Metastasis-associated protein 1 (MTA1), a negative epigenetic modifier, plays a critical role in prostate cancer (PCa) progression. We hypothesized that MTA1 overexpression in primary tumor tissues can predict PCa aggressiveness and metastasis. Immunohistochemical staining of MTA1 was done on archival PCa specimens from University of Mississippi Medical Center and University of Iowa. We found that nuclear MTA1 overexpression was positively correlated with the severity of disease progression reaching its highest levels in metastatic PCa. Nuclear MTA1 overexpression was significantly associated with Gleason > 7 tumors in African Americans but not in Caucasians. It was also a predictor of recurrent disease. We concluded that MTA1 nuclear overexpression may be a prognostic indicator and a future therapeutic target for aggressive PCa in African American men. Our findings may be useful for categorizing African American patients with a higher probability of recurrent disease and metastasis from those who are likely to remain metastasis-free.

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.

False-positive and false-negative sentinel node findings in 473 breast cancers

We reviewed lymph node samples from 473 consecutive breast cancer cases with either negative sentinel nodes or isolated tumor cells to evaluate the rate of false-positive sentinel node findings. Nuclear morphometry was applied to compare nuclear atypia between the primary tumor and metastases classified as isolated tumor cells by size. In addition, the role of the diagnostic preoperative biopsy method, either core needle biopsy or fine needle aspiration cytology, on the prevalence of isolated tumor cells was investigated. In addition, we studied the expression of metastasis-associated protein 1 in the primary tumor and corresponding metastases in 95 cases, including 52 isolated tumor cell cases, to distinguish a true metastasis from a benign epithelial displacement. Our review revealed 4 false positives and 7 false negatives from 473 sentinel node cases. In addition, 5 true-positive cases were upstaged from isolated tumor cells to micrometastases. No association was found between the preoperative biopsy method and the sentinel node status (P=.859). There was no difference in nuclear atypia, when the cells in isolated tumor cells and primary tumor were compared. Therefore, small metastases do not represent benign epithelial displacement. Isolated tumor cell findings did not correlate with preoperative biopsy methods. The metastasis-associated protein 1 staining score sum was lower in the metastases than in the primary tumor in 72% of cases, including all sizes of metastases. These data suggest that metastasis-associated protein 1 staining is not ideal for investigating the possible malignant nature of smaller metastases because of the relatively low concordance between the primary tumor and metastases, even macrometastases.

Factors predisposing metastatic tumor antigen 1 overexpression in hepatitis B virus associated hepatocellular carcinoma

BACKGROUND/AIM

Overexpression of metastatic tumor antigen-1 (MTA-1) is suggested to be associated with frequent postoperative recurrence and poor survival of hepatocellular carcinoma (HCC) patients. In this study, we intended to determine clinical factors predisposing the overexpression of MTA-1 in patients with hepatitis B virus (HBV)-associated HCC and also examine whether MTA-1 overexpression affects the survival periods of these patients treated with curative surgical resection.

METHODS

A total of 303 patients with HBV-associated HCC who underwent curative surgical resection were subjected. The expressions of MTA-1 in HCC and surrounding non-tumor liver tissues were evaluated using the immunohistochemical method. The clinical, radiological and histological characteristics of the patients were analyzed in relation to the expression of MTA-1 to find predisposing factors of MTA-1 overexpression.

RESULTS

MTA-1 was overexpressed in 104 HCC tissues (34.3 %) and none of the surrounding non-tumor tissues. Clinically, MTA-1 overexpression was significantly associated with younger age, female gender, higher serum alpha-fetoprotein level, and Child-Turcotte-Pugh class A. Also, portal vein thrombosis, microvascular invasion, capsular invasion and poorly histological differentiation were associated with overexpression of MTA-1. The cumulative survival rates were significantly lower in patients with MTA-1 overexpression compared with those in the MTA-1 negative group (P = 0.03). In addition to the overexpression of MTA-1, the presence of microvascular or capsular invasion was a significant factor determining the poor survival of the patients with HBV-associated HCC after curative resection.

CONCLUSIONS

MTA-1 is overexpressed in patients with HBV-associated HCC of invasive nature. MTA-1 overexpression is associated with shorter survival periods of patients with HBV-associated HCC after curative resection.

Loss of E-cadherin promotes prostate cancer metastasis via upregulation of metastasis-associated gene 1 expression

E-cadherin is a key cell-to-cell adhesion molecule associated with the invasion and metastasis of tumor cells; however, the molecular mechanisms are not entirely understood. In this study, we investigated whether downregulation of E-cadherin by E-cadherin-specific small intefering RNA (siRNA) was able to promote malignant phenotypes of prostate cancer cells through upregulating the metastasis-associated gene 1 (MTA1) in vitro. The expression levels of E-cadherin in human paired prostate adenocarcinoma cell lines, PC-3M-2B4 (2B4) and PC-3M-1E8 (1E8), were investigated using western blot analysis. The alteration of malignant phenotypes associated with decreasing E-cadherin expression were assessed in 2B4 cells using wound-healing assays, solid-phase adhesion assays, invasion assays and cytoskeletal staining. The expression of E-cadherin and MTA1 in normal, localized and metastatic prostate cancer cells was analyzed using immunohistochemistry. Downregulation of E-cadherin using an RNA interference approach led to the upregulation of MTA1 expression, decreased tumor cell adhesion ability as well as enhanced cell mobility, invasion and cellular polarity compared with the controls (P<0.05). E-cadherin regulated MTA1 in a time-dependent manner. The correlation between E-cadherin and MTA1 was inversed in the prostate cancer group (P<0.05; r(s)=-0.434). The data suggest that E-cadherin plays an important role in prostate cancer metastasis, which is likely to be due to the regulation of MTA1 expression. E-cadherin may combine with MTA1 and alter the malignant phenotype of prostate cancer cells. A combined testing strategy for detecting MTA1 and E-cadherin may be sufficient for selecting high-risk patients with metastasis. Therefore, E-cadherin and MTA1 may be potential powerful factors for the treatment of various types of cancer.

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.

Nuclear overexpression of metastasis-associated protein 1 correlates significantly with poor survival in nasopharyngeal carcinoma

BACKGROUND

Metastasis-associated protein 1 (MTA1) has been associated with poor prognosis in several malignant carcinomas. The purpose of this study was to investigate the expression and prognostic value of MTA1 in nasopharyngeal carcinoma (NPC).

METHODS

MTA1 expression was assessed using immunohistochemistry in paraffin-embedded tumor specimens from 208 untreated NPC patients. Cox regression analysis was used to calculate the hazard ratio (HR), 95% confidence interval (CI) and identify independent prognostic factors, and recursive partitioning analysis was used to create a decision tree.

RESULTS

Nuclear overexpression of MTA1 was observed in 48.6% (101/208) of the NPC tissues. Nuclear overexpression of MTA1 correlated positively with N classification (P = 0.02), clinical stage (P = 0.04), distant metastasis (P < 0.01) and death (P = 0.01). Additionally, nuclear overexpression of MTA1 correlated significantly with poorer distant metastasis-free survival (DMFS; P <0.01) and poorer overall survival (OS; P < 0.01). MTA1 had prognostic significance in NPC patients with stage II disease, but not stage III or IV disease. Multivariate analysis demonstrated that nuclear overexpression of MTA1 was independently associated with poorer DMFS (HR, 2.05; 95% CI, 1.13-3.72; P = 0.02) and poorer OS (HR, 1.98; 95% CI, 1.09-3.59; P = 0.03). Using recursive partitioning analysis, the NPC patients could be classified with a low, intermediate or high risk of distant metastasis and death, on the basis of clinical stage, age and MTA1 expression.

CONCLUSION

The results of this study suggest that nuclear overexpression of MTA1 correlates significantly with poorer DMFS and poorer OS in NPC. MTA1 has potential as a novel prognostic biomarker in NPC.

Single nucleotide polymorphisms associated with metastatic tumour antigen 1 overexpression in patients with hepatocellular carcinoma

BACKGROUNDS/AIMS

Metastatic tumour antigen 1 (MTA1) promotes angiogenesis by stabilizing hypoxia-inducible factor-1α (HIF-1α), which is closely associated with frequent postoperative recurrence and poor survival in patients with HCC. In this study, we determined single nucleotide polymorphisms (SNPs) in angiogenesis-related genes that are associated with MTA1 overexpression in HCC tissues.

METHODS

A total of 376 patients with HCC who had received curative surgical resection or liver transplantation were enrolled (312/21/43; HBV/HCV/NBNC). MTA1 expression was determined via immunohistochemistry. Thirty-three common SNPs sites (frequency ≥5%) in the angiogenic protein gene that are closely connected to one another were selected, including MTA1, VEGF, HIF-1α, FGF-2, and IGF-II.

RESULTS

Expression of MTA1 was detected in 120 HCC tissues (31%). An A allele at position IVS4-81G/A of the MTA1 gene (P = 0.016) and the TT genotype at position +12916C of the VEGF gene (P = 0.023) were significantly associated with MTA1 overexpression. However, the TT genotype at position -13021C (P = 0.011) and the haplotypes CT-CT (-11228C; -13021C) of the IGF-II gene (P(cor) = 0.033) were more common in patients with MTA1-negative HCC. Using multivariate analysis, the A allele at IVS4-81G/A in MTA1 gene (P = 0.015) and a T allele (TT+CT genotype) at -13021C in IGF-II (P = 0.002) were independent risk factors in HCC recurrence after curative surgical resection.

CONCLUSIONS

The genetic polymorphisms IVS4-81G/A in MTA1 and +12916C in VEGF genes were correlated with MTA1 overexpression. The SNPs in MTA1 and IGF-II genes may be important risk factors for the recurrence of HCC.

Metastasis-associated protein 1 nuclear expression is closely associated with tumor progression and angiogenesis in patients with esophageal squamous cell cancer

BACKGROUND

The purposes of the present study were to detect the expression of metastasis-associated protein 1 (MTA1) in patients with esophageal squamous cell cancer (ESCC), and to evaluate the relevance of MTA1 protein expression to the tumor progression, angiogenesis, and prognosis.

METHODS

Both MTA1 protein and intratumoral microvessels were examined by immunohistochemical staining in 131 ESCC patients who successfully underwent subtotal esophagectomy and esophagogastric anastomosis at Qilu Hospital between Jan 2004 and Dec 2005. Intratumoral microvessel density (MVD) was recorded by counting CD-34 positive immunostained endothelial cells. All statistical analyses were performed with SPSS 13.0 statistical software.

RESULTS

High expression of MTA1 protein was detected in 57 cases and significantly correlated with tumor invasion depth (P = 0.041), lymph node metastasis (P = 0.021), pathologic stage (P = 0.003), and MVD (P = 0.044). Survival analysis showed that patients with MTA1 protein high expression had significantly poor overall 5-year survival (P = 0.002), and the factor found on multivariate analysis to significantly affect overall survival was only pathologic stage (P = 0.040). Further stratified survival analysis split by pathologic stage demonstrated that MTA1 protein high expression significantly predicted unfavorable prognosis among patients with pathologic stage II disease (P = 0.006).

CONCLUSIONS

High expression of the MTA1 protein is common in ESCC, and is closely associated with tumor progression, increased tumor angiogenesis, and poor survival. These findings indicate that MTA1 protein has clinical potentials as a useful indicator of progressive phenotype, a promising prognostic predictor to identify patients with poor prognosis, and a potential novel therapeutic target of antiangiogenesis for patients with ESCC.

The translational landscape of mTOR signalling steers cancer initiation and metastasis

The mammalian target of rapamycin (mTOR) kinase is a master regulator of protein synthesis that couples nutrient sensing to cell growth and cancer. However, the downstream translationally regulated nodes of gene expression that may direct cancer development are poorly characterized. Using ribosome profiling, we uncover specialized translation of the prostate cancer genome by oncogenic mTOR signalling, revealing a remarkably specific repertoire of genes involved in cell proliferation, metabolism and invasion. We extend these findings by functionally characterizing a class of translationally controlled pro-invasion messenger RNAs that we show direct prostate cancer invasion and metastasis downstream of oncogenic mTOR signalling. Furthermore, we develop a clinically relevant ATP site inhibitor of mTOR, INK128, which reprograms this gene expression signature with therapeutic benefit for prostate cancer metastasis, for which there is presently no cure. Together, these findings extend our understanding of how the 'cancerous' translation machinery steers specific cancer cell behaviours, including metastasis, and may be therapeutically targeted.

MTA1 expression correlates significantly with cigarette smoke in non-small cell lung cancer

Metastasis tumor antigen 1 (MTA1), a novel candidate metastasis-associated gene, is known to increase the migration and invasion of various tumor cells in vitro. Expression of MTA1 has been shown to be closely correlated with aggressiveness in a variety of human cancers including non-small cell lung cancer (NSCLC). Cigarette smoke is the most established risk for lung carcinogenesis; however, its effects on the progression of NSCLC are still unclear. In this study, we investigated MTA1 expression and analyzed its association with cigarette smoke in NSCLC by immunohistochemistry. To gain a deeper insight into the molecular mechanism underlying the relation between MTA1 and cigarette smoke, we treated the NSCLC cell lines with cigarette smoke extract (CSE). MTA1 mRNA levels and proteins were detected in NSCLC cell lines via reverse transcriptase-polymerase chain reaction (RT-PCR) and western blot analysis. Matrigel invasion assay was performed to evaluate cell invasive ability with the treatment of CSE. Immunohistochemical analysis showed MTA1 expression in NSCLC (61/96, 63.5%) was higher than that in adjacent normal lung tissues (15/96, 15.6%; p < 0.05). Moreover, it was significantly associated with smoking history (p < 0.05). The results of RT-PCR and western blotting showed the upregulation of MTA1 after the treatment of CSE in NSCLC cell lines. Matrigel invasion assays showed that MTA1 upregulation and cell invasion was accompanied with the treatment of CSE in the NSCLC cell lines. MTA1 expression correlated with cigarette smoke in NSCLC and suggested that it may play an important role in the smoked-related progress of NSCLC.

Construction of tissue micro array from prostate needle biopsies using the vertical clustering re-arrangement technique

BACKGROUND

Tissue microarray (TMA) allows for simultaneous rapid expression analysis of multiple molecular targets in many tissue specimens. TMA's are specifically in demand for the screening for diagnostic and prognostic markers in prostate cancer (PC). Consequently, TMAs from prostate needle biopsy (PNB) material taken at diagnosis before any treatment commenced are in demand. However, since PNB contain only limited amount of tumor arranged within a very thin tissue core, TMA construction from PNB is problematic.

METHODS

Archival PNB from 30 PC patients with variable Gleason scores (6-10) and % of cores involvement (30-90%) were used. Following selection of representative cores, the paraffin blocks were melted. Each core was sectioned into equal parts of 3-4 mm in length. For each case, a group of fragments was then re-embedded in a vertical orientation. Using Manual TMA Apparatus, 2 mm cores from each of the vertically rearranged fragments were harvested. Sections (4 µm) were stained with H&E and with high-molecular weight cytokeratin (HMWCK), PIN-cocktail (p63 + p504S), and PSA immunohistochemical stains.

RESULTS

A TMA from PNB with a capacity of 80 serial 4 µm sections was constructed. In all cases, identical tumor and neighboring tissue morphology (atrophic changes and high-grade prostatic intra-epithelial neoplasia) with no loss of tissue was evident.

CONCLUSIONS

The vertical clustering re-arrangement (VCR) technique is suitable for large scale construction of TMA blocks from PNB maintaining the morphological and immunohistochemical characteristics of the original samples. This method is promising both in terms of archival tissue preservation and biomarkers research.

Relationships between metastasis-associated protein (MTA) 1 and lymphatic metastasis in tonsil cancer

We evaluated immunohistochemically the expression profiles of metastasis-associated protein (MTA) 1 and their associations with lymph node metastasis in tonsil cancer. Immunohistochemical analysis of 43 tonsillar neoplasm tissues was performed using antibodies raised to MTA1. Depth of tumor invasion, lymph node metastasis, and clinical outcomes were assessed. Clinical N0 patients were divided into two groups: N0a, negative for MTA1; N0b, positive for MTA1. Occult node metastasis was reevaluated according to the revised clinical N staging system taking account of MTA1 expression. The expression rate of MTA1 was 41.9%. There was a significant correlation between the expression of MTA1 and lymph node metastasis (P = 0.034*). MTA1 had a sensitivity of 53.3% and a specificity of 84.6% for identification of cervical metastases. When cN0b patients were considered to be N+, the recalculated rate of occult metastasis fell from 50% to 7.6% (the false-positive rate remained unchanged). MTA1 was found to be a useful molecular marker to predict lymphatic metastasis in tonsil cancer.