Candidate metastasis-associated genes of the rat 13762NF mammary adenocarcinoma

The eEF1A protein in cancer: Clinical significance, oncogenic mechanisms, and targeted therapeutic strategies

Eukaryotic elongation factor 1A (eEF1A) is among the most abundant proteins in eukaryotic cells. Evolutionarily conserved across species, eEF1A is in charge of translation elongation for protein biosynthesis as well as a plethora of non-translational moonlighting functions for cellular homeostasis. In malignant cells, however, eEF1A becomes a pleiotropic driver of cancer progression via a broad diversity of pathways, which are not limited to hyperactive translational output. In the past decades, mounting studies have demonstrated the causal link between eEF1A and carcinogenesis, gaining deeper insights into its multifaceted mechanisms and corroborating its value as a prognostic marker in various cancers. On the other hand, an increasing number of natural and synthetic compounds were discovered as anticancer eEF1A-targeting inhibitors. Among them, plitidepsin was approved for the treatment of multiple myeloma whereas metarrestin was currently under clinical development. Despite significant achievements in these two interrelated fields, hitherto there lacks a systematic examination of the eEF1A protein in the context of cancer research. Therefore, the present work aims to delineate its clinical implications, molecular oncogenic mechanisms, and targeted therapeutic strategies as reflected in the ever expanding body of literature, so as to deepen mechanistic understanding of eEF1A-involved tumorigenesis and inspire the development of eEF1A-targeted chemotherapeutics and biologics.

Mi-2β promotes immune evasion in melanoma by activating EZH2 methylation

Recent development of new immune checkpoint inhibitors has been particularly successfully in cancer treatment, but still the majority patients fail to benefit. Converting resistant tumors to immunotherapy sensitive will provide a significant improvement in patient outcome. Here we identify Mi-2β as a key melanoma-intrinsic effector regulating the adaptive anti-tumor immune response. Studies in genetically engineered mouse melanoma models indicate that loss of Mi-2β rescues the immune response to immunotherapy in vivo. Mechanistically, ATAC-seq analysis shows that Mi-2β controls the accessibility of IFN-γ-stimulated genes (ISGs). Mi-2β binds to EZH2 and promotes K510 methylation of EZH2, subsequently activating the trimethylation of H3K27 to inhibit the transcription of ISGs. Finally, we develop an Mi-2β-targeted inhibitor, Z36-MP5, which reduces Mi-2β ATPase activity and reactivates ISG transcription. Consequently, Z36-MP5 induces a response to immune checkpoint inhibitors in otherwise resistant melanoma models. Our work provides a potential therapeutic strategy to convert immunotherapy resistant melanomas to sensitive ones.

In vivo screening identifies GATAD2B as a metastasis driver in KRAS-driven lung cancer

Genetic aberrations driving pro-oncogenic and pro-metastatic activity remain an elusive target in the quest of precision oncology. To identify such drivers, we use an animal model of KRAS-mutant lung adenocarcinoma to perform an in vivo functional screen of 217 genetic aberrations selected from lung cancer genomics datasets. We identify 28 genes whose expression promoted tumor metastasis to the lung in mice. We employ two tools for examining the KRAS-dependence of genes identified from our screen: 1) a human lung cell model containing a regulatable mutant KRAS allele and 2) a lentiviral system permitting co-expression of DNA-barcoded cDNAs with Cre recombinase to activate a mutant KRAS allele in the lungs of mice. Mechanistic evaluation of one gene, GATAD2B, illuminates its role as a dual activity gene, promoting both pro-tumorigenic and pro-metastatic activities in KRAS-mutant lung cancer through interaction with c-MYC and hyperactivation of the c-MYC pathway.

Overexpression of the metastasis-associated gene MTA3 correlates with tumor progression and poor prognosis in hepatocellular carcinoma

BACKGROUND AND AIM

Hepatocellular carcinoma (HCC) is one of the most common and aggressive cancers in the world. However, there remains a lack of effective diagnostic and treatment markers. We aimed to explore metastasis-associated protein 3 (MTA3) expression and function in HCC and its relationship with clinicopathological factors.

METHODS

We investigated the expression pattern and clinicopathological significance of MTA3 in 90 patients with HCC via immunohistochemistry and explored MTA3 function via gene knockdown of MTA3.

RESULTS

MTA3 was overexpressed in HCC cell nuclei and downregulated in HCC cell cytoplasm. The former finding correlated with metastasis (P = 0.010) and poor prognosis (P = 0.018). In addition, deleting MTA3 inhibited HCC cell growth, invasion, and metastasis in vitro, as shown in the colony formation, migration, and wound-healing assays.

CONCLUSIONS

These results indicate that MTA3 is an oncogene of HCC, predicts poor prognosis of HCC, and may be a future marker of HCC treatment.

CIP2A, an oncoprotein, is associated with cell proliferation, invasion and migration in laryngeal carcinoma cells

Laryngeal carcinoma is one of the most common malignant tumors in otorhinolaryngology. Moreover, experimental investigation showed that cancerous inhibitor of protein phosphatase 2A (CIP2A) expressed highly in various cancers. Therefore, we investigated whether CIP2A can regulate the proliferation, invasion and migration by RNA interference in Hep-2 cells and AMC-NH-8 cells and further affect the activation of phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT) pathway. Overexpression of CIP2A was evaluated in tumor tissue and laryngeal cancer cell lines (Hep-2 and AMC-NH-8 cells) by real-time quantitative polymerase chain reaction (RT-qPCR) and western blot assay. In a follow-up experiment, we confirmed that CIP2A siRNA effectively suppressed the cell proliferation at 48 and 72 h, and arrested cell cycle at G0/G1 in Hep-2 cells and AMC-NH-8 cells. The invasion and migration of cell in siRNA CIP2A group were markedly inhibited. Moreover, the experimental results showed that the expression levels of invasion- and migration-related genes, including E-cadherin, metastasis-associated gene 1 (MTA1) and matrix metalloproteinases-2/9 (MMP-2/9), were regulated by CIP2A siRNA. Phosphorylation levels of PI3K and AKT proteins were reduced by CIP2A siRNA. Importantly, it suggested signaling through PI3K/Akt as a critical mechanism by which CIP2A siRNA may suppress cell proliferation, invasion and migration in laryngeal carcinoma cells.

[Regulation Mechanism of MTA3 in the Apoptosis of NSCLC Cells]

背景与目的

肿瘤转移基因(metastasis associated gene, MTA)是一个肿瘤候选基因家族, 主要包括MTA1、MTA2、MTA3, 已有的研究证实在不同肿瘤中MTA3发挥着相反的作用, 本研究旨在探讨MTA3在肺癌细胞中调控细胞凋亡方面的影响。

方法

应用Western blot方法和Real-time PCR方法检测肺癌细胞系A549和H157中MTA3的转染效率, 流式细胞仪方法检测上调/下调MTA3后肺癌细胞凋亡情况, Western blot方法检测下调MTA3后凋亡相关基因的表达。

结果

在肺癌细胞系A549和H157中干扰MTA3后则促进细胞凋亡, 同时引起凋亡相关蛋白Bax、Cleved-Caspase-3、p-PARP表达上调及Bcl-2表达下调。

结论

MTA3在肺癌细胞系A549和H157细胞中通过抑制凋亡相关基因的表达抑制细胞凋亡。

The milk-derived hexapeptide PGPIPN inhibits the invasion and migration of human ovarian cancer cells by regulating the expression of MTA1 and NM23H1 genes

Some bioactive peptides derived from natural resources or synthesized by rational design have been proved to have very good anticancer effect. We studied the inhibition of PGPIPN, a hexapeptide derived from bovine β-casein, on the invasion and metastasis of human ovarian cancer cells in vitro and its molecular mechanism. The human ovarian cancer cells studied include the cell line SKOV3 as well as the primary ovarian cancer cells from ovarian tumor tissues of 37 patients at initial debulking surgery, diagnosed as serous ovarian adenocarcinoma. We showed that PGPIPN inhibited the invasion of ovarian cancer cells with Transwell chamber assay, the migration of ovarian cancer cells with cell scratch assay and colony formation of ovarian cancer cells. The expression (mRNAs and proteins) of genes relevant to invasion and metastasis, MTA1, and NM23H1 were analyzed by real-time PCR and western blotting. PGPIPN repressed the expression of MTA1, and promoted NM23H1. The effects of PGPIPN were dose-dependent. Thus, our study suggests that PGPIPN is a potential therapeutic agent for adjuvant therapy of human malignant ovarian tumors.

Structure and function insights into the NuRD chromatin remodeling complex

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

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Identification and characterization of metastasis-associated gene/protein 1 (MTA1)

Metastasis is a complex series of sequential events involving several gene products and the regulated expression of several tumor cell genes. Using rat mammary adenocarcinoma cell lines of differing metastatic potentials and a differential complementary DNA (cDNA) hybridization method, our laboratory embarked in 1992 on a project to identify candidate metastasis-associated genes. 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 gene without any homologous or related genes in the database in 1994. The full-length cDNA of this gene was cloned, sequenced, and named mta1 (metastasis-associated gene 1), 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). The products of the MTA genes, the MTA proteins, are transcriptional co-regulators that function in histone deacetylation and nucleosome remodeling. In this review, we will briefly discuss the researches for the identification and characterization of the mta1 gene, its human counterpart MTA1, and their protein products.

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.

The subcellular distribution and function of MTA1 in cancer differentiation

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

Analysis of MAT3 gene expression in NSCLC

Background

Many studies have suggested different roles of Metastasis-associated protein 3 (MAT3) in different types of human cancers. However, expression of MAT3 in primary lung cancer and its relationship with clinicopathological factors have not been examined and the biological roles of MTA3 in lung cancer cells are still unclear.

Methods

The expression of MAT3 mRNA and protein were detected with quantitative real-time RT-PCR and immunohistochemical methods in 118 NSCLC samples and corresponding non-neoplastic samples. Survival curves were made with follow-up data. The relations of the prognosis with clinical and pathological characteristics were analyzed.

Results

The expression level of MAT3 mRNA and the positive rate of MAT3 protein were significantly higher in NSCLC samples than that in non-neoplastic samples, and in NSCLC samples with lymph node metastasis than that in NSCLC samples without lymph node metastasis (P < 0.01). MAT3 mRNA expression level was a risk factor of lymph node metastasis in patients with NSCLC (P = 0.006). There were significant differences in survival curves between lymph node metastatic group and non-metastatic group (P = 0.000), among groups of MAT3 positive and negative (P = 0.000), among groups of TNM stage I, II and III (P = 0.000) and among groups of tumor status T1, T2 and T3T4 (P = 0.000); but no statistical significance between male patients and female patients (P = 0.516), between ≥60 years old patients and <60 years old patients (P = 0.133), between histology types adenocarcinoma and squamous cell carcinoma (P = 0.865) and between well differentiation and moderate-poor differentiation (P = 0.134). The level of MAT3 mRNA (P = 0.000) and protein (P = 0.000) were risk factors of survival.

Conclusion

Our study showed that MAT3 over-expression in NSCLC tissue, and MAT3 mRNA level is a risk factor of lymph node metastasis. The level of MAT3 mRNA and protein were risk factors of survival in patients with NSCLC. It suggested that this antigen could be used as a simple and efficient parameter with which to identify high-risk patients.

Virtual slides

The virtual slides for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/5585901065503943.

Expression of USP22, MTA1 and Ki-67 in esophageal squamous cell carcinoma

AIM: To investigate the expression of ubiquitin specific peptidase 22 (USP22), metastasis associated gene 1 (MTA1) and nuclear associated antigen (Ki-67) in esophageal squamous cell carcinoma (ESCC) and to analyze their relationship with clinicopathologic features of ESCC.

METHODS: Immunohistochemistry was used to detect the expression of USP22, MTA1 and Ki-67 proteins in ESCC, matched tumor-adjacent tissue and normal esophageal tissue. The correlation between the expression of these proteins and clinicopathologic features of ESCC was analyzed.

RESULTS: The positive rate of USP22 expression in ESCC was significantly higher than that in tumor-adjacent tissue and normal esophageal tissue (68.18% vs 36.36%, 15.91%, both P < 0.05). Expression of USP22 was significantly associated with tumor invasion depth and histological grade, but not with age, sex or lymph node metastasis. The positive rate of MTA1 expression was also significantly higher in ESCC than in tumor-adjacent tissue and normal esophageal tissue (61.36% vs 31.82%, 6.82%, both P < 0.05). MTA1 expression was significantly associated with lymph node metastasis, tumor invasion depth and histological grade, but not with age or sex. The positive rate of Ki-67 expression was also significantly higher in ESCC than in tumor-adjacent tissue and normal esophageal tissue (70.45% vs 43.18%, 11.36%, both P < 0.05). Expression of Ki-67 was significantly associated with lymph node metastasis, tumor invasion depth and histological grade, but not with age or sex. USP22 protein expression was positively correlated with the expression of MTA1 and Ki-67 proteins; however, the expression of MTA1 protein was not significantly correlated with that of Ki-67 protein.

CONCLUSION: USP22, MTA1 and Ki-67 may participate in the occurrence and metastasis of esophageal carcinoma. Combined detection of the expression of these proteins will be helpful to the diagnosis of esophageal carcinoma and accurate determination of the biological behavior of this malignancy. USP22, MTA1 and Ki-67 may become new targets for gene therapy of esophageal carcinoma.

Overexpression of MTA3 Correlates with Tumor Progression in Non-Small Cell Lung Cancer

The objective of the current study was to investigate the expression pattern and clinicopathological significance of MTA3 in patients with non-small cell lung cancer (NSCLC). The expression profile of MTA3 in NSCLC tissues and adjacent noncancerous lung tissues was detected by immunohistochemistry. MTA3 was overexpressed in 62 of 108 (57.4%) human lung cancer samples and correlated with p-TNM stage (p<0.0001), nodal metastasis (p = 0.0009) and poor prognosis (p<0.05). In addition, the depletion of MTA3 expression with small interfering RNAs inhibited cell growth and colony formation in the A549 and H157 lung cancer cell lines. Moreover, MTA3 depletion induced cell cycle arrest at the G1/S boundary. Western blotting analysis revealed that the knockdown of MTA3 decreased the protein levels of cyclin A, cyclin D1 and p-Rb. These results indicate that MTA3 plays an important role in NSCLC progression.

eEF1A2 promotes cell migration, invasion and metastasis in pancreatic cancer by upregulating MMP-9 expression through Akt activation

eEF1A2 is a protein translation factor involved in protein synthesis that is overexpressed in various cancers, with important functions in tumor genesis and progression. We have previously showed that the ectopic expression of eEF1A2 is correlated with lymph node metastasis and perineural invasion in pancreatic cancer. In this study, we investigated the functional role of eEF1A2 in the regulation of cell migration, invasion, and metastasis in pancreatic cancer. Furthermore, we investigated the potential molecular mechanisms involved. By evaluating the invasive ability of a panel of pancreatic cancer cell lines with different metastatic potentials, eEF1A2 expression in cells was positively associated with their invasive ability. The knockdown of eEF1A2 by siRNA decreased the migration and invasion of PANC-1 cells. By contrast, the ectopic expression of exogenous eEF1A2 significantly promoted the migration and invasion of SW1990 cells. Stable eEF1A2 overexpression in a nude mouse model of peritoneal metastasis likewise dramatically enhanced the intraperitoneal metastatic ability of SW1990 cells. In addition, eEF1A2 overexpression could upregulate MMP-9 expression and activity. A significant positive correlation between the overexpression of both eEF1A2 and MMP-9 was observed in pancreatic cancer tissues. The inhibition of MMP-9 activity reduced the promoting effect of eEF1A2 on cell migration and invasion. Furthermore, eEF1A2-mediated cell migration and invasion, as well as MMP-9 expression and upregulation, were largely dependent on the eEF1A2-induced Akt activation. The findings suggested the potentially important role of eEF1A2 in pancreatic cancer migration, invasion, and metastasis. Thus, the results provide evidence of eEF1A2 as a potential therapeutic target in the treatment of aggressive pancreatic cancer.

Cancer biology and NuRD: a multifaceted chromatin remodelling complex

The nucleosome remodelling and histone deacetylase (NuRD; also known as Mi-2) complex regulates gene expression at the level of chromatin. The NuRD complex has been identified - using both genetic and molecular analyses - as a key determinant of differentiation in mouse embryonic stem cells and during development in various model systems. Similar to other chromatin remodellers, such as SWI/SNF and Polycomb complexes, NuRD has also been implicated in the regulation of transcriptional events that are integral to oncogenesis and cancer progression. Emerging molecular details regarding the recruitment of NuRD to specific loci during development, and the modulation of these events in cancer, are used to illustrate how the inappropriate localization of the complex could contribute to tumour biology.

Insights into association of the NuRD complex with FOG-1 from the crystal structure of an RbAp48·FOG-1 complex

Chromatin-modifying complexes such as the NuRD complex are recruited to particular genomic sites by gene-specific nuclear factors. Overall, however, little is known about the molecular basis for these interactions. Here, we present the 1.9 Å resolution crystal structure of the NuRD subunit RbAp48 bound to the 15 N-terminal amino acids of the GATA-1 cofactor FOG-1. The FOG-1 peptide contacts a negatively charged binding pocket on top of the RbAp48 β-propeller that is distinct from the binding surface used by RpAp48 to contact histone H4. We further show that RbAp48 interacts with the NuRD subunit MTA-1 via a surface that is distinct from its FOG-binding pocket, providing a first glimpse into the way in which NuRD assembly facilitates interactions with cofactors. Our RbAp48·FOG-1 structure provides insight into the molecular determinants of FOG-1-dependent association with the NuRD complex and into the links between transcription regulation and nucleosome remodeling.

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

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

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

背景与目的

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

方法

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

结果

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

结论

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

Increased expression of elongation factor-1α is significantly correlated with poor prognosis of human prostate cancer

OBJECTIVE

Overexpression of elongation factor-1α (EF-1α) has been demonstrated to be related to increased cell proliferation, oncogenic transformation and delayed cell senescence. The purpose of this study was to determine whether EF-1α expression affects the progression of prostate cancer (PCa), and whether it can be used as a prognostic marker for PCa.

MATERIAL AND METHODS

EF-1α was evaluated by immunostaining in paraffin-embedded specimens of prostates obtained from 80 patients with PCa. Correlations of EF-1α with patients' ages, Gleason scores, American Joint Committee on Cancer (AJCC) stages, International Union Against Cancer (UICC) stages, preoperative prostate-specific antigen (PSA) concentrations and PSA failure were evaluated. Survival in all patients was analysed to evaluate the influence of EF-1α expression in cancer progression using Kaplan-Meier and multivariate Cox regression analysis.

RESULTS

The positive expression rate of EF-1α in PCa tissues [64/80 (80.0%)] was significantly higher than that in normal prostate tissues [1/20 (5.0%)] (p < 0.001). Increased immunostaining of EF-1α was a significant predictor of distant metastasis-free survival [hazard ratio (HR) 0.386, 95% confidence interval (CI) 0.032-2.519, p = 0.003] and overall survival (HR 0.305, 95% CI 0.091-0.872, p = 0.005). In multivariate analysis including competing biological variables, EF-1α expression was still significantly linked to distant metastasis-free survival (HR 0.216, 95% CI 0.042-0.876, p = 0.015) and overall survival (HR 0.395, 95% CI 0.116-0.798, p = 0.008).

CONCLUSION

These findings provide convincing evidence for the first time that EF-1α correlates closely with the survival of patients with PCa and may be a novel prognostic marker.

Elongation Factor 1 alpha interacts with phospho-Akt in breast cancer cells and regulates their proliferation, survival and motility

Background

Akt/PKB is a serine/threonine kinase that has attracted much attention because of its central role in regulating cell proliferation, survival, motility and angiogenesis. Activation of Akt in breast cancer portends aggressive tumour behaviour, resistance to hormone-, chemo-, and radiotherapy-induced apoptosis and it is correlated with decreased overall survival. Recent studies have identified novel tumor-specific substrates of Akt that may provide new diagnostic and prognostic markers and serve as therapeutic targets. This study was undertaken to identify pAkt-interacting proteins and to assess their biological roles in breast cancer cells.

Results

We confirmed that one of the pAkt interacting proteins is the Elongation Factor EF1α. EF1α contains a putative Akt phosphorylation site, but is not phosphorylated by pAkt1 or pAkt2, suggesting that it may function as a modulator of pAkt activity. Indeed, downregulation of EF1α expression by siRNAs led to markedly decreased expression of pAkt1 and to less extent of pAkt2 and was associated with reduced proliferation, survival and invasion of HCC1937 cells. Proliferation and survival was further reduced by combining EF1α siRNAs with specific pAkt inhibitors whereas EF1α downregulation slightly attenuated the decreased invasion induced by Akt inhibitors.

Conclusion

We show here that EF1α is a pAkt-interacting protein which regulates pAkt levels. Since EF1α is often overexpressed in breast cancer, the consequences of EF1α increased levels for proliferation, survival and invasion will likely depend on the relative concentration of Akt1 and Akt2.

S100A4 overexpression proves to be independent marker for breast cancer progression

BACKGROUND

Breast cancer is the most common cancer and cause of deaths in women around the world. Oncogene amplification usually occurs late in tumor progression and correlates well with aggressiveness of tumor. In fact the function of the S100A4 protein and its role in metastasis is unclear at present. The purpose of the study was to determine the expression of S100A4 protein in the invasion status and metastatic potential of breast cancer by using tissue microarray and to determine its role in breast cancer based on the expression of S100A4 gene product.

METHODS

S100A4 protein expression was examined by immunohistochemistry (IHC) using commercially available tissue microarray containing malignant and normal breast tissue cores from 216 patients.

RESULTS

S100A4 was absent in normal breast tissues while positive in 45.1% of infiltrating ductal carcinoma (IDC) node negative and 48.8% of infiltrating lobular carcinoma node negative. In paired samples, S100A4 protein was expressed in 13.5% of IDC node positive cases and 35.1% of matched lymph node metastasis.

CONCLUSION

S100A4 protein expression appears widely expressed in early and advanced breast cancer stages compared with normal breast. Our study suggests S100A4 may play a role in breast cancer progression and may prove to be an independent marker of breast cancer which appears to be down regulated in more advanced stages of breast cancer.

Identification of Metastasis Associated Antigen 1 (MTA1) by Serological Screening of Prostate Cancer cDNA Libraries

Over the past 10 years the serological analysis of recombinant cDNA expression libraries (SEREX) has proved to be an effective method for the identification of tumour antigens. In the present study, two prostate cancer libraries were constructed and screened using autologous sera. Fifty five genes were isolated, including 46 known genes and 9 previously uncharacterised genes. Among the known genes, a metastasis-associated gene, MTA1, previously identified by differential cDNA hybridisation, was preferentially expressed in a panel of malignant tissues compared with normal tissues, as analysed by reverse transcriptase-polymerase chain reaction (RT-PCR). MTA1 transcripts were observed to be over-expressed in normal human testes as well as various cancer tissues when compared to the panel of normal tissues. MTA1 antigen reacted with 2 of 13 allogeneic prostate cancer patient sera tested, but no sera reactivity was observed to any of the normal adult sera tested. Furthermore, a similar distribution and expression level of MTA-1 was observed in murine tissues and cancer cell lines. Based on these findings and previous reports on the literature on this gene, MTA-1 can be considered not only as a “biomarker” of aggressive disease but also as a potential therapeutic target.

The human Mi-2/NuRD complex and gene regulation

The Mi-2/nucleosome remodeling and deacetylase (NuRD) complex is an abundant deacetylase complex with a broad cellular and tissue distribution. It is unique in that it couples histone deacetylation and chromatin remodeling ATPase activities in the same complex. A decade of research has uncovered a number of interesting connections between Mi-2/NuRD and gene regulation. The subunit composition of the enzyme appears to vary with cell type and in response to physiologic signals within a tissue. Here, we review the known subunits of the complex, their connections to signaling networks, and their association with cancer. In addition, we propose a working model that integrates the known biochemical properties of the enzyme with emerging models on how chromatin structure and modification relate to gene activity.

MTA family of transcriptional metaregulators in mammary gland morphogenesis and breast cancer

Since breast cancer and its associated metastasis are a global health problem and a major cause of mortality among women, research efforts to understand the development, morphogenesis, and functioning of the mammary gland are a high priority. Myriad signaling pathways, transcription factors, and associated transcriptional coregulators have been identified in both normal functioning and neoplastic transformation of the mammary gland. The discovery of the metastasis tumor antigen 1 (MTA1) gene, its overexpression in cancer and metastasis and its subsequent identification as an integral part of the chromatin remodeling complex heralded extensive research on its physiological role. Subsequent identification of additional gene family members, namely MTA1s, MTA2, and MTA3, and their functions in the cell has resulted in the establishment of the significance of the MTA family. The role of these proteins in modulating hormonal responses in normal mammary glands and in breast cancer has resulted in their identification as important molecular markers and potential therapeutic targets.

Expression of metastasis-associated gene 1, PTEN and E-cadherin in gastric carcinoma and their correlations

AIM: To investigate the expression of metastasis-associated gene 1 (MTA1), PTEN and E-cadherin in gastric carcinoma and normal gastric mucosa and their relationships with the invasion, metastasis and biological behavior of gastric carcinoma.

METHODS: Immunohistochemistry was used to examine the expression of MTA1, PTEN and E-cadherin proteins in gastric carcinoma (n = 54) and normal gastric mucosa (n = 15). The data were processed by chi-square test and the correlation was analyzed by Spearman test.

RESULTS: In comparison with those in normal gastric mucosa, the expression of MTA1 in gastric carcinoma was significantly higher (46.3% vs 6.7%, P < 0.01), and the expression of PTEN and E-cadherin in gastric carcinoma were down-regulated or even disappeared (51.9% vs 100%, 42.6% vs 100%; both P < 0.01). The expression of MTA1 and PTEN were correlated with the invasion depth (P = 0.003, P = 0.001), pathological grades (P = 0.004, P = 0.008), lymph node metastasis (P = 0.000, P = 0.001), distant metastasis (P = 0.004, P = 0.006) and clinical classification (P = 0.001, P = 0.000), and the normal expression of E-cadherin had relationship with the invasion depth (P = 0.027), pathological grades (P = 0.006), lymph node metastasis (P = 0.044), and clinical classification (P = 0.000). There was a negative correlation between the expression of MTA1 and PTEN as well as between the expression of MTA1 and E-cadherin (r = -0.518, r = -0.424; both P < 0.05), but there was a positive correlation between the expression of PTEN and E-cadherin (r = 0.53, P < 0.05).

CONCLUSION: High expression of MTA1 and low expression of PTEN and E-cadherin may be associated with the invasion and metastasis of gastric carcinoma. Combined examination of three indexes may be used to evaluate the biological behavior of gastric carcinoma.

Expression of metastasis-associated gene 1 and its correlation with invasion and metastasis of human gastric carcinoma

AIM: To investigate the expression of metastasis-associated gene 1 (MTA1) in human gastric carcinoma and its correlation with tumor metastasis.

METHODS: Real time polymerase chain reaction (PCR) and Western blot were employed to detect the expression of MTA1 in gastric carcinoma and its adjacent gastric mucosa obtained from the surgical specimens of 42 patients, and the correlation between the expression of MTA1 and the differentiation and metastasis of gastric carcinoma were investigated.

RESULTS: The expression of MTA1 mRNA in gastric carcinoma was significantly higher than that in the adjacent gastric mucosa (0.6711 vs 0.3940, P < 0.01), and the expression of MTA1 protein was in accordance with that of MTA1 mRNA. MTA1 mRNA expression was markedly higher in the poorly-differentiated gastric carcinomas than that in the well- or moderately-differentiated ones (0.7475 vs 0.3460, P < 0.01). Moreover, the expression of MTA1 mRNA was dramatically increased in the gastric carcinomas with metastasis as compared with that in the ones without metastasis (0.8128 vs 0.4933, P < 0.01).

CONCLUSION: MTA1 expression is up-regulated in gastric carcinoma, which is closely correlated with the differentiation and metastasis, MTA1 may serve as a marker in predicting the biological behavior and prognosis of gastric carcinoma.

eEF1A2 activates Akt and stimulates Akt-dependent actin remodeling, invasion and migration

eEF1A2 (eukaryotic protein elongation factor 1 alpha 2) is a protein translation factor that is likely a human oncogene by virtue of its capacity to transform mammalian cells and its high expression in tumors of the ovary, breast and lung. Here, we show that expression of eEF1A2 is sufficient to stimulate the formation of filopodia in BT549 human breast cancer cells and non-transformed Rat2 cells. Filopodia formation in eEF1A2-expressing cells is dependent on the activity of phosphatidylinositol-3 kinase (PI3K), and the ROCK and Akt kinases. Furthermore, eEF1A2 expression is sufficient to activate Akt in a PI3K-dependent fashion and inactivation of eEF1A2 by short interfering RNA reduces Akt activity. Using breast cancer cell line BT 549, we show that eEF1A2 expression stimulates cell migration and invasion in a largely PI3K- and Akt-dependent manner. These results suggest that eEF1A2 regulates oncogenesis through Akt and PI3K-dependent cytoskeletal remodeling.

Metastatic tumor antigen 3 is a direct corepressor of the Wnt4 pathway

Here we show that expression of MTA3 inhibits ductal branching in virgin and pregnant murine transgenic mammary glands. MTA3 also suppresses the Wnt4 pathway and, thus, these findings parallel phenotypic changes in Wnt4-null mice. MTA3 represses Wnt4 transcription and Wnt4 secretion, inhibiting Wnt-target genes in mammary epithelial cells. Accordingly, knockdown of endogenous MTA3 stimulates Wnt4 expression and Wnt cellular targets. The MTA3-NuRD (nucleosome remodeling and deacetylase) complex physically interacts with the Wnt4 chromatin in an HDAC-dependent manner, leading to suppression of the Wnt4 gene and Wnt4-dependent morphogenesis. These findings identify MTA3 as an upstream physiologic repressor of Wnt4 in mammary epithelial cells.

Hepatitis C virus NS4A inhibits cap-dependent and the viral IRES-mediated translation through interacting with eukaryotic elongation factor 1A

The genomic RNA of hepatitis C virus (HCV) encodes the viral polyprotein precursor that undergoes proteolytic cleavage into structural and nonstructural proteins by cellular and the viral NS3 and NS2-3 proteases. Nonstructural protein 4A (NS4A) is a cofactor of the NS3 serine protease and has been demonstrated to inhibit protein synthesis. In this study, GST pull-down assay was performed to examine potential cellular factors that interact with the NS4A protein and are involved in the pathogenesis of HCV. A trypsin digestion followed by LC-MS/MS analysis revealed that one of the GST-NS4A-interacting proteins to be eukaryotic elongation factor 1A (eEF1A). Both the N-terminal domain of NS4A from amino acid residues 1-20, and the central domain from residues 21-34 interacted with eEF1A, but the central domain was the key player involved in the NS4A-mediated translation inhibition. NS4A(21-34) diminished both cap-dependent and HCV IRES-mediated translation in a dose-dependent manner. The translation inhibitory effect of NS4A(21-34) was relieved by the addition of purified recombinant eEF1A in an in vitro translation system. Taken together, NS4A inhibits host and viral translation through interacting with eEF1A, implying a possible mechanism by which NS4A is involved in the pathogenesis and chronic infection of HCV.

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.

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

Estrogen receptor (ER)alpha activity is controlled by the balance of coactivators and corepressors contained within cells that are recruited into transcriptional complexes. The metastasis-associated protein (MTA) family has been demonstrated to be associated with breast tumor cell progression and ERalpha activity. We demonstrate that MTA2 expression is correlated with ERalpha protein expression in invasive breast tumors. We show that the MTA2 family member can bind to ERalpha and repress its activity in human breast cancer cells. Furthermore, it can inhibit ERalpha-mediated colony formation and render breast cancer cells resistant to estradiol and the growth-inhibitory effects of the antiestrogen tamoxifen. MTA2 participates in the deacetylation of ERalpha protein, potentially through its associated histone deacetylase complex 1 activity. We hypothesize that MTA2 is a repressor of ERalpha activity and that it could represent a new therapeutic target of ERalpha action in human breast tumors.

Proteomics profiling of nuclear proteins for kidney fibroblasts suggests hypoxia, meiosis, and cancer may meet in the nucleus

Proteomics methods were used to characterize proteins that change their form or abundance in the nucleus of NRK49F rat kidney fibroblasts during prolonged hypoxia (1% O(2), 12 h). Of the 791 proteins that were monitored, about 20% showed detectable changes. The 51 most abundant proteins were identified by mass spectrometry. Changes in nuclear receptor transcription factors (THRalpha1, RORalpha4, HNF4alpha, NUR77), other transcription factors (GATA1, AP-2alpha, OCT1, ATF6alpha, ZFP161, ZNF354A, PDCD2), and transcription cofactors (PC4, PCAF, MTA1, TCEA1, JMY) are indicative of major, co-ordinated changes in transcription. Proteins involved in DNA repair/recombination, ribosomal RNA synthesis, RNA processing, nuclear transport, nuclear organization, protein translation, glycolysis, lipid metabolism, several protein kinases (PKCdelta, MAP3K4, GRK3), as well as proteins with no established functional role were also observed. The observed proteins suggest nuclear regulatory roles for proteins involved in cytosolic processes such as glycolysis and fatty acid metabolism, and roles in overall nuclear structure/organization for proteins previously associated with meiosis and/or spermatogenesis (synaptonemal complex proteins 1 and 2 (SYCP1, SYCP2), meiosis-specific nuclear structural protein 1 (MNS1), LMNC2, zinc finger protein 99 (ZFP99)). Proteins associated with cytoplasmic membrane functions (ACTN4, hyaluronan mediated motility receptor (RHAMM), VLDLR, GRK3) and/or endocytosis (DNM2) were also seen. For 30% of the identified proteins, new isoforms indicative of alternative transcription were detected (e.g., GATA1, ATF6alpha, MTA1, MLH1, MYO1C, UBF, SYCP2, EIF3S10, MAP3K4, ZFP99). Comparison with proteins involved in cell death, cancer, and testis/meiosis/spermatogenesis suggests commonalities, which may reflect fundamental mechanisms for down-regulation of cellular function.

Hormonal regulation of metastasis-associated protein 3 transcription in breast cancer cells

Metastasis-associated protein 3 (MTA3) is a cell type-specific subunit of the Mi-2/NuRD transcriptional corepressor complex. In breast cancer cells, MTA3 and the Mi-2/NuRD complex mediate repression of Snail, a transcription factor that promotes epithelial to mesenchymal transitions. Thus, MTA3 functions to maintain a differentiated, epithelial status in breast cancer. Interestingly, in mammary epithelial cells, MTA3 biosynthesis requires both functional estrogen receptor (ER) and estradiol. Here we have investigated the molecular basis for estrogen and ER-dependent expression of MTA3 in breast cancer cells. Molecular dissection of the MTA3 promoter using transient transfection assays identified a composite element required for high-level transcription consisting of an SP1 site in close proximity to a consensus estrogen response element half-site. Depletion of either SP1 or ER-alpha by RNA interference led to loss of MTA3 transcript in multiple breast cancer cell lines, indicating a requirement for both transcription factors in expression of endogenous MTA3. The MTA3 gene thus joins a growing list of loci regulated by both SP1 and ER.

Mi-2/NuRD: multiple complexes for many purposes

The vertebrate Mi-2/NuRD complex is a multi-subunit protein complex containing both histone deacetylase and nucleosome-dependent ATPase subunits. Current models predict that this complex functions primarily in transcriptional repression. Surprisingly, every subunit of this complex presents heterogeneity at the protein and gene level. This raises the intriguing possibility of functional specialization resulting from incorporation of unique gene products into the complex. The MTA (metastasis-associated) proteins represent one class of alternative subunits of the human Mi-2/NuRD complex. The members of this family in human cells are differentially expressed depending on cell type and on physiologic parameters. We summarize evidence supporting the view that the alternative subunits of the complex that have arisen during vertebrate evolution endow unique functional properties.

Identification of differentially expressed genes in isogenic highly metastatic and poorly metastatic cell lines of R3230AC rat mammary adenocarcinoma

Tumour metastasis occurs as a result of a cascade of events including alterations in the expression of various genes. The identification of such genes is essential to understanding formation of metastasis. In a previous study, highly metastatic (LN4.D6) and poorly metastatic (CAb.D5) cell lines were obtained from the rat mammary adenocarcinoma cell line R3230AC. Subtractive hybridization was used to identify differentially expressed genes between these two cell lines. We identified eight cDNA clones in CAb.D5 and six cDNA clones in LN4.D6 that were differentially expressed. One of the cDNA clones in each cell line had no homology with known sequences. Expression patterns of these differentially expressed genes were examined in a pair of rat mammary and prostate adenocarcinoma cell lines. Compared with cell lines examined, cDNA FF-10 was only expressed in CAb.D5; however, cDNA RB-8, RE-1, RF-5 were only expressed in the highly metastatic LN4.D6. No correlation was observed between expression patterns of the differentially expressed genes and metastatic potential of these cells. However, differential expression of genes, especially cytokeratins (CK8 and CK5) and collagens (III and IV) between highly metastatic and low metastatic rat mammary adenocarcinoma cell lines might initiate further investigation of these genes in metastatic process.

The metastasis-associated proteins 1 and 2 form distinct protein complexes with histone deacetylase activity

The metastasis-associated protein MTA1 has been shown to express differentially to high levels in metastatic cells. MTA2, which is homologous to MTA1, is a component of the NuRD ATP-dependent chromatin remodeling and histone deacetylase complex. Here we report evidence that although both human MTA1 and MTA2 repress transcription specifically, are located in the nucleus, and contain associated histone deacetylase activity, they exist in two biochemically distinct protein complexes and may perform different functions pertaining to tumor metastasis. Specifically, both MTA1 and MTA2 complexes exert histone deacetylase activity. However, the MTA1 complex contained HDAC1/2, RbAp46/48, and MBD3, but not Sin3 or Mi2, two important components of the MTA2 complex. Moreover, the MTA2 complex is similar to the HDAC1 complex, suggesting a housekeeping role of the MTA2 complex. The MTA1 complex could be further separated, resulting in a core MTA1-HDAC complex, showing that the histone deacetylase activity and transcriptional repression activity were integral properties of the MTA1 complex. Finally, MTA1, unlike MTA2, did not interact with the pleotropic transcription factor YY1 or the immunophilin FKBP25. We suggest that MTA1 associates with a different set of transcription factors from MTA2 and that this property may contribute to the metastatic potential of cells overexpressing MTA1. We also report the finding of human MTA3, which is highly homologous to both MTA1 and MTA2. However, MTA3 does not repress transcription to a significant level and appears to have a diffused pattern of subcellular localization, suggesting a biological role distinct from that of the other two MTA proteins.

MTA3, a Mi-2/NuRD complex subunit, regulates an invasive growth pathway in breast cancer

Estrogen receptor is a key regulator of proliferation and differentiation in mammary epithelia and represents a crucial prognostic indicator and therapeutic target in breast cancer. Mechanistically, estrogen receptor induces changes in gene expression through direct gene activation and also through the biological functions of target loci. Here, we identify the product of human MTA3 as an estrogen-dependent component of the Mi-2/NuRD transcriptional corepressor in breast epithelial cells and demonstrate that MTA3 constitutes a key component of an estrogen-dependent pathway regulating growth and differentiation. The absence of estrogen receptor or of MTA3 leads to aberrant expression of the transcriptional repressor Snail, a master regulator of epithelial to mesenchymal transitions. Aberrant Snail expression results in loss of expression of the cell adhesion molecule E-cadherin, an event associated with changes in epithelial architecture and invasive growth. These results establish a mechanistic link between estrogen receptor status and invasive growth of breast cancers.

Tumor metastasis-associated human MTA1 gene and its MTA1 protein product: role in epithelial cancer cell invasion, proliferation and nuclear regulation

Using differential cDNA library screening techniques based on metastatic and nonmetastatic rat mammary adenocarcinoma cell lines, we previously cloned and sequenced the metastasis-associated gene mta1. Using homology to the rat mta1 gene, we cloned the human MTA1 gene and found it to be over-expressed in a variety of human cell lines (breast, ovarian, lung, gastric and colorectal cancer but not melanoma or sarcoma) and cancerous tissues (breast, esophageal, colorectal, gastric and pancreatic cancer). We found a close similarity between the human MTA1 and rat mta1 genes (88% and 96% identities of the nucleotide and predicted amino acid sequences, respectively). Both genes encode novel proteins that contain a proline rich region (SH3-binding motif), a putative zinc finger motif, a leucine zipper motif and 5 copies of the SPXX motif found in gene regulatory proteins. Using Southern blot analysis the MTA1 gene was highly conserved, and using Northern blot analysis MTA1 transcripts were found in virtually all human cell lines (melanoma, breast, cervix and ovarian carcinoma cells and normal breast epithelial cells). However, the expression level of the MTA1 gene in normal breast epithelial cells was approximately 50% of that found in rapidly growing adenocarcinoma and atypical epithelial cell lines. Experimental inhibition of MTA1 protein expression using antisense phosphorothioate oligonucleotides resulted in inhibition of growth and invasion of human MDA-MB-231 breast cancer cells with relatively high MTA1 expression. Furthermore, the MTA1 protein was localized in the nuclei of cells transfected with a mammalian expression vector containing a full-length MTA1 gene. Although some MTA1 protein was found in the cytoplasm, the vast majority of MTA1 protein was localized in the nucleus. Examination of recombinate MTA1 and related MTA2 proteins suggests that MTA1 protein is a histone deacetylase. It also appears to behave like a GATA-element transcription factor, since transfection of a GATA-element reporter into MTA1-expressing cells resulted in 10-20-fold increase in reporter expression over poorly MTA1-expressing cells. Since it was reported that nucleosome remodeling histone deacetylase complex (NuRD complex) involved in chromatin remodeling contains MTA1 protein and a MTA1-related protein (MTA2), we examined NuRD complexes for the presence of MTA1 protein and found an association of this protein with histone deacetylase. The results suggest that the MTA1 protein may serve multiple functions in cellular signaling, chromosome remodeling and transcription processes that are important in the progression, invasion and growth of metastatic epithelial cells.

Tumor metastasis-associated human MTA1 gene and its MTA1 protein product: role in epithelial cancer cell invasion, proliferation and nuclear regulation

Using differential cDNA library screening techniques based on metastatic and nonmetastatic rat mammary adenocarcinoma cell lines, we previously cloned and sequenced the metastasis-associated gene mta1. Using homology to the rat mta1 gene, we cloned the human MTA1 gene and found it to be over-expressed in a variety of human cell lines (breast, ovarian, lung, gastric and colorectal cancer but not melanoma or sarcoma) and cancerous tissues (breast, esophageal, colorectal, gastric and pancreatic cancer). We found a close similarity between the human MTA1 and rat mta1 genes (88% and 96% identities of the nucleotide and predicted amino acid sequences, respectively). Both genes encode novel proteins that contain a proline rich region (SH3-binding motif), a putative zinc finger motif, a leucine zipper motif and 5 copies of the SPXX motif found in gene regulatory proteins. Using Southern blot analysis the MTA1 gene was highly conserved, and using Northern blot analysis MTA1 transcripts were found in virtually all human cell lines (melanoma, breast, cervix and ovarian carcinoma cells and normal breast epithelial cells). However, the expression level of the MTA1 gene in normal breast epithelial cells was approximately 50% of that found in rapidly growing adenocarcinoma and atypical epithelial cell lines. Experimental inhibition of MTA1 protein expression using antisense phosphorothioate oligonucleotides resulted in inhibition of growth and invasion of human MDA-MB-231 breast cancer cells with relatively high MTA1 expression. Furthermore, the MTA1 protein was localized in the nuclei of cells transfected with a mammalian expression vector containing a full-length MTA1 gene. Although some MTA1 protein was found in the cytoplasm, the vast majority of MTA1 protein was localized in the nucleus. Examination of recombinate MTA1 and related MTA2 proteins suggests that MTA1 protein is a histone deacetylase. It also appears to behave like a GATA-element transcription factor, since transfection of a GATA-element reporter into MTA1-expressing cells resulted in 10-20-fold increase in reporter expression over poorly MTA1-expressing cells. Since it was reported that nucleosome remodeling histone deacetylase complex (NuRD complex) involved in chromatin remodeling contains MTA1 protein and a MTA1-related protein (MTA2), we examined NuRD complexes for the presence of MTA1 protein and found an association of this protein with histone deacetylase. The results suggest that the MTA1 protein may serve multiple functions in cellular signaling, chromosome remodeling and transcription processes that are important in the progression, invasion and growth of metastatic epithelial cells.

Identification and validation of metastasis-associated proteins in head and neck cancer cell lines by two-dimensional electrophoresis and mass spectrometry

Despite improvements in treatment of patients with head and neck squamous cell carcinoma (HNSCC) over the last two decades, the survival rate of these patients has not increased significantly. One of the major factors in the poor outcome of the disease is regional metastasis. To better understand the mechanisms of this process at the protein level, we performed two-dimensional electrophoresis (2-DE) and mass spectrometry using SELDI ProteinChip technology to identify proteins differentially expressed in two HNSCC cell lines, UMSCC10A and UMSCC10B, from the same patient. UMSCC10A was derived from the primary tumor and UMSCC10B from a metastatic lymph node. The differentially expressed proteins were excised from the gels. Following in-gel digestion by trypsin, mass profiles of the peptides were generated. Proteins were identified by submitting the peptide mass profiles to a public available NCBInr databases (www.proteometrics.com). Two membrane-associated proteins, annexin I and annexin II and glycolytic protein enolase-alpha were found to be upregulated, and calumenin precursor down-regulated, in metastatic cell line UMSCC10B. The identity of these proteins was confirmed by analyzing additional peptide mass fingerprints obtained by endoproteinase lysine-C digestion. The results were also validated by Western blotting analysis. Our results showed that enolase-alpha, annexin-I and annexin-II might be important molecules in head and neck cancer invasion and metastasis. The results also suggest an important complementary role for proteomics in identification of molecular abnormalities important in cancer development and progression.

Down-regulation of annexin A10 in hepatocellular carcinoma is associated with vascular invasion, early recurrence, and poor prognosis in synergy with p53 mutation

Annexins (ANXs) are a large group of calcium-binding proteins participating in diverse important biological processes. ANXA10 is the least expressed new member of unknown function. We showed that ANXA10 mRNA was expressed in adult liver and hepatocellular carcinoma (HCC), but not in multiple adult and fetal tissues, cholangiocarcinoma, and several other common carcinomas. Of 182 unifocal primary HCCs, ANXA10 mRNA was dramatically reduced in 121 (66%), and the down-regulation correlated with p53 mutation (P = 0.024), early intrahepatic tumor recurrence (P = 0.0007), and lower 4-year survival (P = 0.0014). Down-regulation of ANXA10 was twofold more frequent in large than small HCCs (P = 0.0012), in grade II to III than grade I HCC (P < 0.00001), and in stage IIIA to IV than stage I to II HCC (P < 0.00001). Moreover, ANXA10 down-regulation and p53 mutation acted synergistically toward high-grade (P < 0.00001), high-stage HCC (P < 0.00001), and poorer prognosis (P = 0.0025). Our results indicate that the expression of the tissue- and tumor-restricted ANXA10 is a marker of liver cell differentiation and growth arrest, and its down-regulation associated with malignant phenotype of hepatocytes, vascular invasion, and progression of HCC, leading to poor prognosis. Thus, ANXA10 might serve as a new potential target of gene therapy for HCC.

Expression of the MTA1 mRNA in advanced lung cancer

The MTA1 gene is a recently identified metastasis-associated gene which has been implicated in the signal transduction or regulation of gene expression. We examined the mRNA expression levels of the MTA1, the human homologue of the rat mta1 gene in non-small cell lung cancer (NSCLC). Expression of MTA1 messenger RNA was evaluated by reverse transcription polymerase chain reaction (RT-PCR) in 74 non-small cell lung carcinoma samples using LightCycler. The data was analyzed in reference to clinicopathological data. There was no relationship between MTA1 gene expression and age and gender. MTA1/GAPDH mRNA level in stage II-IV NSCLC (3.465+/-3.675) was significantly higher than the level in stage I NSCLC (1.614+/-2.434, P=0.0153). MTA1/GAPDH mRNA levels in T4 NSCLC (4.377+/-4.169) was significantly higher than the level in T1 NSCLC (1.966+/-2.148, P=0.0351) and in T2 NSCLC (2.048+/-1.899, P=0.0269), respectively. MTA1/GAPDH mRNA level in NSCLC with lymph node metastasis (4.242+/-3.758) was significantly higher in NSCLC without lymph node metastasis (P=0.0169). Our results show that the expression of the MTA1 gene is closely related to invasiveness and metastasis in NSCLC. The gene MTA1 could thus potentially provide information on the mechanism of cancer invasion and metastasis.

Differential expression and subcellular distribution of the mouse metastasis-associated proteins Mta1 and Mta3

The human metastasis-associated gene (MTA1) is overexpressed in cell lines and tissues representing metastatic tumors. Here we report cloning of the mouse Mta1 as well as a novel structurally related mouse gene, Mta3. The mouse Mta1 protein shares 94 and 59% homology to the human MTA1 and mouse Mta3 proteins, respectively. Northern blotting analysis using an Mta1 cDNA probe revealed a prevalent 3 kb hybridization signal in all mouse tissues except the skeletal muscle while a smaller approximately 1.0 kb mRNA product was also detected in the heart. Mta3 transcripts (approximately 2 kb) were detected in most tissues with an additional approximately 6.2 kb signal detected in the brain. In vitro transcription/translation of the full-length Mta1 and Mta3 cDNAs generated products of the expected molecular masses, i.e. 80 and 60 kDa, respectively. To assess subcellular localization, green fluorescence protein (GFP)-tagged expression constructs of Mta1 and Mta3 and various deletion constructs of GFP-Mta1 were transiently expressed in Balb/MK keratinocytes. GFP-Mta1 was found exclusively in the nucleus while GFP-Mta3 was present in both the nucleus and cytoplasm. Compared to Mta3, the carboxy terminal end of Mta1 contains an additional nuclear localization signal (NLS) and a proline-rich Src homology 3 (SH3) ligand. The results of transient expression experiments of various Mta1 fragments containing these domains in different combinations indicated that nuclear localization of Mta1 depended on the presence of at least one NLS and one SH3 binding site. These SH3 ligands appeared to be functional as they facilitated interaction with the adaptor protein, Grb2, and the Src-family tyrosine kinase, Fyn.

Activated leukocyte cell adhesion molecule (ALCAM) and annexin II are involved in the metastatic progression of tumor cells after chemotherapy with Adriamycin

Metastasis frequently occurs during and/or after chemotherapy resulting in failure. This suggests that inadequate chemotherapy promotes the emergence of more malignant tumor cells with metastatic potential. However, it is not determined how chemotherapy could promote the metastatic progression of tumor cells. In this study, we isolated highly metastatic clones from the tumors treated with ADR using an in vivo experimental model, in which non-metastatic tumor cells were inoculated s.c. in mice, treated with or without Adriamycin and then culture lines were re-established from the tumors. Then we isolated cDNAs for activated leukocyte cell adhesion molecule (ALCAM), osteopontin, and annexin II as candidates for metastasis-promoting genes with the use of a PCR-based subtraction method. Further we examined the metastatic potential of transfectants over-expressing ALCAM, osteopontin, or annexin II and combinations of them. Metastasis to the lung was observed in the mice where transfectants over-expressing ALCAM plus annexin II had been inoculated via tail vein. These results suggest that the over-expression of ALCAM and annexin II play a role in the metastatic progression after chemotherapy with ADR.