Metastasis suppressor pathways--an evolving paradigm

Metastasis suppressor genes in clinical practice: are they druggable?

Since the identification of NM23 (now called NME1) as the first metastasis suppressor gene (MSG), a small number of other gene products and non-coding RNAs have been identified that suppress specific parameters of the metastatic cascade, yet which have little or no ability to regulate primary tumor initiation or maintenance. MSG can regulate various pathways or cell biological functions such as those controlling mitogen-activated protein kinase pathway mediators, cell-cell and cell-extracellular matrix protein adhesion, cytoskeletal architecture, G-protein-coupled receptors, apoptosis, and transcriptional complexes. One defining facet of this gene class is that their expression is typically downregulated, not mutated, in metastasis, such that any effective therapeutic intervention would involve their re-expression. This review will address the therapeutic targeting of MSG, once thought to be a daunting task only facilitated by ectopically re-expressing MSG in metastatic cells in vivo. Examples will be cited of attempts to identify actionable oncogenic pathways that might suppress the formation or progression of metastases through the re-expression of specific metastasis suppressors.

Antiproliferative, Antiangiogenic, and Antimigrastatic Effects of Oroxylum indicum (L.) Kurz Extract on Breast Cancer Cell

Breast cancer recurrence continues to pose a major clinical problem, despite significant advancements in early diagnosis and an aggressive mode of treatment. This study aimed at investigating the anticancer activity of Oroxylum indicum extract (OIE) by assessing cell proliferation, cell migration, and angiogenesis in metastatic breast cancer MDA-MB-231 cell lines. This study also estimated the phytochemical profiles of OIE by LC-QTOF-MS. The extract was found to contain six identified flavonoid substances, and baicalein was the most abundant substance in the extract. Cell proliferation capacity was performed by cell counting kit-8 (CCK-8) and colony formation assays. The effect of OIE on cell migration was determined using wound healing and transwell assays. Meanwhile, MDA-MB-231-induced angiogenesis on chick chorioallantoic membrane (CAM) was applied to investigate the ex vivo antiangiogenesis activity of the extracts. OIE at concentrations lower than 600 μg/mL had no cytotoxic effects against MDA-MB-231 cells. OIE was found to inhibit the long-term colony formation ability of MDA-MB-231 cells in a concentration-dependent manner. Antimigration and antiangiogenesis activities were further investigated using noncytotoxic concentrations of OIE ranging from 25 to 150 μg/mL. OIE greatly reduced the migration of MDA-MB-231 breast cancer cells in a dose-dependent manner. OIE significantly suppressed the MDA-MB-231-induced angiogenesis, and there was no substantial toxic effect on natural angiogenesis. Interestingly, the concentration of OIE at 150 μg/mL was as practically potent as pazopanib, the positive anticancer drug, at 4.37 μg/mL in inhibiting MDA-MB-231 cell migration and angiogenesis induced by these cells. Therefore, the inhibitory effects of OIE in cell proliferation and cell migration, together with antiangiogenesis in MDA-MB-231 breast cancer cells, suggesting that OIE has the potential to be a novel adjunct candidate for breast cancer chemotherapeutic agents.

Molecular principles of metastasis: a hallmark of cancer revisited

Metastasis is the hallmark of cancer that is responsible for the greatest number of cancer-related deaths. Yet, it remains poorly understood. The continuous evolution of cancer biology research and the emergence of new paradigms in the study of metastasis have revealed some of the molecular underpinnings of this dissemination process. The invading tumor cell, on its way to the target site, interacts with other proteins and cells. Recognition of these interactions improved the understanding of some of the biological principles of the metastatic cell that govern its mobility and plasticity. Communication with the tumor microenvironment allows invading cancer cells to overcome stromal challenges, settle, and colonize. These characteristics of cancer cells are driven by genetic and epigenetic modifications within the tumor cell itself and its microenvironment. Establishing the biological mechanisms of the metastatic process is crucial in finding open therapeutic windows for successful interventions. In this review, the authors explore the recent advancements in the field of metastasis and highlight the latest insights that contribute to shaping this hallmark of cancer.

Metastasis Suppressors NME1 and NME2 Promote Dynamin 2 Oligomerization and Regulate Tumor Cell Endocytosis, Motility, and Metastasis

NM23 (NME) is a metastasis suppressor that significantly reduces metastasis without affecting primary tumor size, however, the precise molecular mechanisms are not completely understood. We examined the role of dynamin (DNM2), a GTPase regulating membrane scission of vesicles in endocytosis, in NME1 and NME2 regulation of tumor cell motility and metastasis. Overexpression of NMEs in MDA-MB-231T and MDA-MB-435 cancer cell lines increased endocytosis of transferrin and EGF receptors (TfR and EGFR) concurrent with motility and migration suppression. The internalized vesicles, costained with Rab5, had AP2 depleted from the cell surface and exhibited increased Rab5-GTP levels, consistent with endocytosis. Dynamin inhibitors Iminodyn-22 and Dynole-34-2, or shRNA-mediated downregulation of DNM2, impaired NME's ability to augment endocytosis or suppress tumor cell motility. In a lung metastasis assay, NME1 overexpression failed to significantly suppress metastasis in the DNM2 knockdown MDA-MB-231T cells. Using the EGF-EGFR signaling axis as a model in MDA-MB-231T cells, NME1 decreased pEGFR and pAkt expression in a DNM2-dependent manner, indicating the relevance of this interaction for downstream signaling. NME-DNM2 interaction was confirmed in two-way coimmunoprecipitations. Transfection of a NME1 site-directed mutant lacking histidine protein kinase activity but retaining nucleoside diphosphate kinase (NDPK) activity showed that the NDPK activity of NME was insufficient to promote endocytosis or inhibit EGFR signaling. We show that addition of NME1 or NME2 to DNM2 facilitates DNM2 oligomerization and increases GTPase activity, both required for vesicle scission. NME-DNM2 interaction may contribute to metastasis suppression by altering tumor endocytic and motility phenotypes. SIGNIFICANCE: NME1 suppresses metastasis via changes in tumor endocytosis and motility, mediated by dynamin (DNM2) GTPase activity.

Identification of a gene expression signature associated with the metastasis suppressor function of NME1: prognostic value in human melanoma

Although NME1 is well known for its ability to suppress metastasis of melanoma, the molecular mechanisms underlying this activity are not completely understood. Herein, we utilized a bioinformatics approach to systematically identify genes whose expression is correlated with the metastasis suppressor function of NME1. This was accomplished through a search for genes that were regulated by NME1, but not by NME1 variants lacking metastasis suppressor activity. This approach identified a number of novel genes, such as ALDOC, CXCL11, LRP1b, and XAGE1 as well as known targets such as NETO2, which were collectively designated as an NME1-Regulated Metastasis Suppressor Signature (MSS). The MSS was associated with prolonged overall survival in a large cohort of melanoma patients in The Cancer Genome Atlas (TCGA). The median overall survival of melanoma patients with elevated expression of the MSS genes was >5.6 years longer compared with that of patients with lower expression of the MSS genes. These data demonstrate that NMEl represents a powerful tool for identifying genes whose expression is associated with metastasis and survival of melanoma patients, suggesting their potential applications as prognostic markers and therapeutic targets in advanced forms of this lethal cancer.

A core program of gene expression characterizes cancer metastases

While aberrant expression or splicing of metastasis genes conveys to cancers the ability to break through tissue barriers and disseminate, the genetic basis for organ preference in metastasis formation has remained incompletely understood. Utilizing the gene expression profiles from 653 GEO datasets, we investigate whether the signatures by diverse cancers in various metastatic sites display common features. We corroborate the meta-analysis in a murine model. Metastases are generally characterized by a core program of gene expression that induces the oxidative metabolism, activates vascularization/tissue remodeling, silences extracellular matrix interactions, and alters ion homeostasis. This program distinguishes metastases from their originating primary tumors as well as from their target host tissues. Site-selectivity is accomplished through specific components that adjust to the target micro-environment. The same functional groups of gene expression programs are activated in the metastases of B16-F10 cells to various target organs. It remains to be investigated whether these genetic signatures precede implantation and thus determine organ preference or are shaped by the target site and are thus a consequence of implantation. Conceivably, chemotherapy of disseminated cancer might be more efficacious if selected to match the genetic makeup of the metastases rather than the organ of origin by the primary tumor.

Metastasis suppressor proteins in cutaneous squamous cell carcinoma

Cutaneous squamous cell carcinomas (cSCCs) are common human carcinomas. Despite having metastasizing capacities, they usually show less aggressive progression compared to squamous cell carcinoma (SCC) of other organs. Metastasis suppressor proteins (MSPs) are a group of proteins that control and slow-down the metastatic process. In this study, we established the importance of seven well-defined MSPs including NDRG1, NM23-H1, RhoGDI2, E-cadherin, CD82/KAI1, MKK4, and AKAP12 in cSCCs. Protein expression levels of the selected MSPs were detected in 32 cSCCs, 6 in situ SCCs, and two skin cell lines (HaCaT, A-431) by immunohistochemistry. The results were evaluated semi-quantitatively using the HSCORE system. In addition, mRNA expression levels were detected by qRT-PCR in the cell lines. The HSCOREs of NM23-H1 were similar in cSCCs and normal skin tissues, while RGHOGDI2, E-cadherin and AKAP12 were significantly downregulated in cSCCs compared to normal skin. The levels of MKK4, NDRG1 and CD82 were partially conserved in cSCCs. In stage I SCCs, nuclear staining of NM23-H1 (NM23-H1nuc) was significantly lower than in stage II/III SCCs. Only nuclear staining of MKK4 (MKK4nuc) showed significantly higher scores in in situ carcinomas compared to invasive SCCs. In conclusion, similar to other human tumors, we have demonstrated complex differential expression patterns for the MSPs in in-situ and invasive cSCCs. This complex MSP signature warrants further biological and experimental pathway research.

Innate and adoptive immune cells contribute to natural resistance to systemic metastasis of B16 melanoma

The greatest hurdle in cancer treatment is the metastasis of primary tumors to distant organs. Our knowledge on how different immune cells, in the absence of exogenous stimulation, prevent tumor metastasis in distant organs is poorly understood. Using a highly metastatic murine lung B16 melanoma cell line BL6-10, we employed naive mice that genetically lack CD4(+) or CD8(+) T cells, or are depleted of dendritic cells (DCs) or natural killer (NK) cells to understand the relative importance of these cells in metastasis prevention. Irrespective of the presence of naïve CD4(+) T, CD8(+) T, DCs, or NK cells, lungs, which act as primary site of predilection for B16 melanoma, readily developed numerous lung BL6-10 melanoma colonies. However, their absence led to B16 melanoma metastasis in variable proportions to distant organs, particularly livers, kidneys, adrenals, ovaries, and hearts. NK cells mediate prevention of BL6-10 metastasis to various organs, especially to livers. Mechanistically, CD40L signaling, a critical factor required for DC licensing and CD8(+) cytotoxic T lymphocyte (CTL) responses, was required for CD4(+) T cell-mediated prevention of systemic BL6-10 metastasis. These results suggest that the composition and functions of different immune cells in distant tissue microenvironments (distant organs other than primary sites of predilection) robustly mediate natural resistance against melanoma metastasis. Thus, harnessing these immune cells' responses in immunotherapeutics would considerably limit organ metastasis.

Kisspeptins (KiSS-1): essential players in suppressing tumor metastasis

Kisspeptins (KPs) encoded by the KiSS-1 gene are C-terminally amidated peptide products, including KP- 10, KP-13, KP-14 and KP-54, which are endogenous agonists for the G-protein coupled receptor-54 (GPR54). Functional analyses have demonstrated fundamental roles of KiSS-1 in whole body homeostasis including sexual differentiation of brain, action on sex steroids and metabolic regulation of fertility essential for human puberty and maintenance of adult reproduction. In addition, intensive recent investigations have provided substantial evidence suggesting roles of Kisspeptin signalling via its receptor GPR54 in the suppression of metastasis with a variety of cancers. The present review highlights the latest studies regarding the role of Kisspeptins and the KiSS-1 gene in tumor progression and also suggests targeting the KiSS-1/GPR54 system may represent a novel therapeutic approach for cancers. Further investigations are essential to elucidate the complex pathways regulated by the Kisspeptins and how these pathways might be involved in the suppression of metastasis across a range of cancers.

Targeting MAPK pathway in melanoma therapy

New drugs targeting the mitogen-activated protein kinase (MAPK) pathway have generated striking clinical response in melanoma therapy. From the discovery of BRAF mutation in melanoma in 2002, to the approval of first BRAF inhibitor vemurafenib for melanoma treatment by the US Food and Drug Administration in 2011, therapies targeting the MAPK pathway have been proven effective in less than a decade. The success of vemurafenib stimulated more intensive investigation of the molecular mechanisms of melanoma pathogenesis and development of new treatment strategies targeting specific molecules in MAPK pathway. Although selective BRAF inhibitors and MEK inhibitors demonstrated improved overall survival of metastatic melanoma patients, limited duration or development of resistance to BRAF inhibitors have been reported. Patients with metastatic melanoma still face very poor prognosis and lack of clarified therapies. Studies and multiple clinical trials on more potent and selective small molecule inhibitory compounds to further improve the clinical effects and overcome drug resistance are underway. In this review, we analyzed the therapeutic potentials of each member of the MAPK signaling pathway, summarized important MAPK-inhibiting drugs, and discussed the promising combination treatment targeting multiple targets in melanoma therapy, which may overcome the drawbacks of current drugs treatment.

Metastatic breast cancer: mechanisms and opportunities for cytology

Despite significant advances in diagnosis, surgical techniques, general patient care, and local and systemic adjuvant therapies, metastatic disease remains the most critical condition limiting the survival of patients with breast cancer. Therefore, the development of effective treatment against late-arising metastasis has become the centre of clinical attention and is one of the current challenges in cancer research. A deeper understanding of the metastatic cascade is fundamental, and the need for repetitive tumour assessments for the evaluation of tumour evolution is a relatively new practice in routine medical care. As such, fine needle aspiration cytology (FNAC) is ideally placed to monitor biological changes in metastasis that may affect treatment and response. As FNAC is a minimally invasive method, it can be performed repeatedly with relatively little trauma, and selective ancillary tests can be applied to FNAC specimens, including for tumour whose primary nature is known. Herein, we review how the linear and parallel models explain metastatic dissemination, thus influencing therapeutic and clinical decisions, and how cytology, together with immunocytochemistry and molecular analysis, can be a tool for routine clinical practice and clinical trials aimed at metastatic disease with a special emphasis on breast cancer.

Functional genomic analysis of cancer metastasis: biologic insights and clinical implications

Metastasis, the spread of cancer from primary tumors to distant vital organs, has devastating consequences. Lack of effective tools to study this complex problem has hindered the development of accurate prognostic methods and effective treatments for metastatic cancer. In the postgenomic era, the application of genomic profiling methods to the analysis of clinical metastasis samples and animal metastasis models has revolutionized the field of metastasis research. This article reviews recent breakthroughs in the functional genomic analysis of metastasis. In addition, its impacts on our understanding of the molecular basis of metastasis and on clinical practice are discussed.

CD82/KAI expression prevents IL-8-mediated endothelial gap formation in late-stage melanomas

Melanoma cells facilitate endothelial gap formation, the first step during tumor transendothelial migration, which is mediated by both adhesion and endogenously produced chemokines (in particular, interleukin-8 (IL-8)). Tetraspanins are localized to the cell surface in cancer and participate in various functions including invasion of tissues mediated by secretion of cytokines and matrix metalloproteinases. However, little is known about the role of CD82 tetraspanins in malignant melanomas during cancer cell invasion. In this study, we investigated the functional importance of CD82 expression in melanoma-mediated gap formation by using cDNAs to induce CD82 expression in highly invasive melanoma cell lines. Results showed that CD82 expression inhibited melanoma cell-induced gap formation, melanoma cell extravasation in vitro and subsequent lung metastasis development in vivo. Mechanistic studies showed that inducible expression of CD82 in highly metastatic melanoma cells significantly increased p21 expression upon binding of Duffy antigen receptor group (DARC), inducing tumor cell senescence and interrupting IL-8-mediated vascular endothelial (VE)-cadherin disassembly. Taken together, these studies provide a rationale for using drug therapies that restore CD82 expression and inhibit IL-8 production to inhibit late-stage melanoma cell extravasation and subsequent metastasis development.

Epigenetic regulation and role of metastasis suppressor genes in pancreatic ductal adenocarcinoma

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) is distinguished by rapid dissemination. Thus, genetic and/or epigenetic deregulation of metastasis suppressor genes (MSG) is a likely event during early pancreatic carcinogenesis and a potential diagnostic marker for the disease. We investigated 9 known MSGs for their role in the dissemination of PDAC and examined their promoters for methylation and its use in PDAC detection.

METHODS

MRNA expression of 9 MSGs was determined in 18 PDAC cell lines by quantitative RT-PCR and promoter methylation was analyzed by Methylation Specific PCR and validated by Bisulfite Sequencing PCR. These data were compared to the cell lines' in vivo metastatic and invasive potential that had been previously established. Statistical analysis was performed with SPSS 20 using 2-tailed Spearman's correlation with P < 0.05 being considered significant.

RESULTS

Complete downregulation of MSG-mRNA expression in PDAC cell lines vs. normal pancreatic RNA occurred in only 1 of 9 investigated genes. 3 MSGs (CDH1, TIMP3 and KiSS-1) were significantly methylated. Methylation only correlated to loss of mRNA expression in CDH1 (P < 0.05). Bisulfite Sequencing PCR showed distinct methylation patterns, termed constant and variable methylation, which could distinguish methylation-regulated from non methylation-regulated genes. Higher MSG mRNA-expression did not correlate to less aggressive PDAC-phenotypes (P > 0.14).

CONCLUSIONS

Genes with metastasis suppressing functions in other tumor entities did not show evidence of assuming the same role in PDAC. Inactivation of MSGs by promoter methylation was an infrequent event and unsuitable as a diagnostic marker of PDAC. A distinct methylation pattern was identified, that resulted in reduced mRNA expression in all cases. Thus, constant methylation patterns could predict regulatory significance of a promoter's methylation prior to expression analysis and hence present an additional tool during target gene selection.

Bone marrow-derived Gr1+ cells can generate a metastasis-resistant microenvironment via induced secretion of thrombospondin-1

Metastatic tumors have been shown to establish permissive microenvironments for metastases via recruitment of bone marrow-derived cells. Here, we show that metastasis-incompetent tumors are also capable of generating such microenvironments. However, in these situations, the otherwise prometastatic Gr1(+) myeloid cells create a metastasis-refractory microenvironment via the induction of thrombospondin-1 (Tsp-1) by tumor-secreted prosaposin. Bone marrow-specific genetic deletion of Tsp-1 abolished the inhibition of metastasis, which was restored by bone marrow transplant from Tsp-1(+) donors. We also developed a 5-amino acid peptide from prosaposin as a pharmacologic inducer of Tsp-1 in Gr1(+) bone marrow cells, which dramatically suppressed metastasis. These results provide mechanistic insights into why certain tumors are deficient in metastatic potential and implicate recruited Gr1(+) myeloid cells as the main source of Tsp-1. The results underscore the plasticity of Gr1(+) cells, which, depending on the context, promote or inhibit metastasis, and suggest that the peptide could be a potential therapeutic agent against metastatic cancer.

SIGNIFICANCE

The mechanisms of metastasis suppression are poorly understood. Here, we have identified a novel mechanism whereby metastasis-incompetent tumors generate metastasis-suppressive microenvironments in distant organs by inducing Tsp-1 expression in the bone marrow–derived Gr1+myeloid cells. A 5-amino acid peptide with Tsp-1–inducing activity was identified as a therapeutic agent against metastatic cancer.

Therapeutic upregulation of Class A scavenger receptor member 5 inhibits tumor growth and metastasis

Class A scavenger receptor member 5 (SCARA5) is a new member of the Class A scavenger receptors that has been proposed recently as a novel candidate tumor suppressor gene in human hepatocellular carcinoma. In the present study, we found that SCARA5 expression was frequently downregulated in various cancer cell lines and tumor samples. In addition, upregulation of SCARA5 expression in human cancer cell line (U251) led to a significant decrease in cell proliferation, clone formation, migration, and invasion in vitro. Furthermore, systemic treatment of tumor-bearing mice with SCARA5-cationic liposome complex not only reduced the growth of subcutaneous human glioma tumors, but also markedly suppressed the spontaneous formation of lung metastases. Similar results were obtained in another experiment using mice bearing experimental A549 lung metastases. Compared with the untreated control group, mice treated with SCARA5 exhibited reductions in both spontaneous U251 and experimental A549 lung metastases rates of 77.3% and 70.2%, respectively. Western blot analysis was used to explore the molecular mechanisms involved and revealed that SCARA5 physically associated with focal adhesion kinase. Interestingly, upregulation of SCARA5 inactivated signal transducer and activator of transcription 3, as well as downstream signaling including cyclinB1, cyclinD1, AKT, survivin, matrix metalloproteinase-9 and vascular endothelial growth factor-A. Overall, the findings of the present study provide the first evidence that SCARA5 might be a promising target for the development of new antimetastatic agents for the gene therapy of cancer.

Recognition and reactivity in the binding between Raf kinase inhibitor protein and its small-molecule inhibitor locostatin

The present work is aimed to provide detail on the binding process between Raf kinase inhibitor protein (RKIP) and locostatin, the only exogenous compound known to alter the function of RKIP. Understanding the basis of RKIP inhibition for use in pharmacological applications is of considerable interest, as dysregulated RKIP expression has the potential to contribute to pathophysiological processes. Herein, we report a series of atomistic models to describe the protein-ligand recognition step and the subsequent reactivity steps. Modeling approaches include ligand docking, molecular dynamics, and quantum mechanics/molecular mechanics calculations. We expect that such a computational assay will serve to study similar complexes in which potency is associated with recognition and reactivity. Although previous data suggested a single amino acid residue (His86) to be involved in the binding of locostatin, the actual ligand conformation and the steps involved in the reactivity process remain elusive from a detailed atomistic description. We show that the first reaction step, consisting of a nucleophilic attack of the nitrogen (Nε) of His86 at the sp(2)-hybridized carbon (C2) of locostatin, presents a late transition state (almost identical to the product). The reaction is followed by a hydrogen abstraction and hydrolysis. The theoretically predicted overall rate constant (6 M(-1) s(-1)) is in a very good agreement with the experimentally determined rate constant (13 M(-1) s(-1)).

Highly invasive melanoma cells activate the vascular endothelium via an MMP-2/integrin αvβ5-induced secretion of VEGF-A

Tumor cell extravasation is a critical step in the metastatic cascade and requires interaction between the tumor cell and the endothelium. Although cancer progression depends on a complex network of mechanisms, including inflammation and coagulation, the involvement of tumor-induced endothelium activation and the subsequent release of procoagulatory factors in this process are not well understood. Using tissue sections from patients with malignant melanoma, immunofluorescence studies for the presence of von Willebrand factor (VWF) clearly demonstrated endothelium activation and the formation of ultra-large VWF fibers in these patients. In vitro analyses revealed that supernatants from highly invasive melanoma cells induced an acute endothelium activation measured by VWF, P-selectin, and angiopoietin-2 release. Proteome profiling identified vascular endothelial growth factor A (VEGF-A) as the main mediator of endothelium activation. Inhibition and knock-down of VEGF-A in melanoma cells led to a rigorous decrease in VWF exocytosis. Selective small-interfering RNA to matrix metalloproteinase-2 (MMP-2) inhibited endothelium activation, and this effect correlated with reduced VEGF-A content in the supernatants of melanoma cells. Further experiments showed that active MMP-2 regulates VEGF-A in melanoma cells on a transcriptional level via an integrin αvβ5/phosphoinositide-3-kinase-dependent pathway. In conclusion, these results indicate an important role of VEGF-A in acute endothelium activation and provide clear evidence that MMP-2 plays a pivotal role in the autocrine regulation of VEGF-A expression in melanoma cells.

A Low Molecular Weight Polysaccharide Isolated from Agaricus blazei Murill (LMPAB) Exhibits Its Anti-Metastatic Effect by Down-Regulating Metalloproteinase-9 and Up-Regulating Nm23-H1

The components of Agaricus blazei Murill (AbM) have been shown to possess antitumor potentials. Herein, we attempted to explore the anti-metastatic effect and underlying mechanism of a low molecular weight polysaccharide isolated from AbM (LMPAB). Matrigel invasion assay was applied to evaluate the effect of LMPAB on migration of BEL-7402 hepatic cancer cells in vitro. In vivo, the anti-metastatic effect of LMPAB was investigated in mouse B16 melanoma and a double-grafted SW180 tumor models. mRNA and protein levels of metalloproteinase-9 (MMP-9) or nm23-H1 upon LMPAB treatment were detected by real-time PCR and immunohistochemistry assays. LMPAB significantly reduced the invasion of BEL-7402 cells. In vivo, LMPAB was revealed to decrease lung metastatic foci in mouse B16 melanoma model. In the double-grafted SW180 mouse tumor model, we further demonstrated that intratumoral treatment of LMPAB inhibited the growth of tumor on treated side but also suppresses the regression of metastatic tumors on the non-treated side. Moreover, LMPAB reduced MMP-9 but enhanced nm23-H1 mRNA and protein expression. LMPAB displays anti-metastatic activities, indicating the potential of its clinical application for the prevention and treatment of cancer metastasis. Its anti-metastatic effect may relate to the modulation on MMP-9 and nm23-H1.

N-myc downstream regulated gene 1 modulates Wnt-β-catenin signalling and pleiotropically suppresses metastasis

Wnt signalling has pivotal roles in tumour progression and metastasis; however, the exact molecular mechanism of Wnt signalling in the metastatic process is as yet poorly defined. Here we demonstrate that the tumour metastasis suppressor gene, NDRG1, interacts with the Wnt receptor, LRP6, followed by blocking of the Wnt signalling, and therefore, orchestrates a cellular network that impairs the metastatic progression of tumour cells. Importantly, restoring NDRG1 expression by a small molecule compound significantly suppressed the capability of otherwise highly metastatic tumour cells to thrive in circulation and distant organs in animal models. In addition, our analysis of clinical cohorts data indicate that Wnt+/NDRG−/LRP+ signature has a strong predictable value for recurrence-free survival of cancer patients. Collectively, we have identified NDRG1 as a novel negative master regulator of Wnt signalling during the metastatic progression, which opens an opportunity to define a potential therapeutic target for metastatic disease.

Three interrelated themes in current breast cancer research: gene addiction, phenotypic plasticity, and cancer stem cells

Recent efforts to understand breast cancer biology involve three interrelated themes that are founded on a combination of clinical and experimental observations. The central concept is gene addiction. The clinical dilemma is the escape from gene addiction, which is mediated, in part, by phenotypic plasticity as exemplified by epithelial-to-mesenchymal transition and mesenchymal-to-epithelial transition. Finally, cancer stem cells are now recognized as the basis for minimal residual disease and malignant progression over time. These themes cooperate in breast cancer, as induction of epithelial-to-mesenchymal transition enhances self-renewal and expression of cancer stem cells, which are believed to facilitate tumor resistance.

Immunohistochemical detection of Raf kinase inhibitor protein in normal cervical tissue and cervical cancer tissue

Raf kinase inhibitor protein (RKIP) may be a suppressor of metastasis: RKIP levels are high in normal tissues, low in primary cancers and lowest or absent in metastatic cancers. This immunohisto chemistry study investigated RKIP protein levels in 250 clinical specimens of human cervical tissue and lymph node metastases (LNM) from 210 patients with normal cervical tissue, cervical intra-epithelial neoplasia (CIN), or cervical cancer with/without LNM. Thirty-nine (86.7%) of the 45 normal-tissue samples were RKIP-positive, six (13.3%) were RKIP-negative; 48/60 (80.0%) CIN samples were positive, 12 (20.0%) were negative; 47/105 (44.8%) cervical cancer tissue samples were positive, 58 (55.2%) were negative; only 7/40 (17.5%) LNM tissue samples were positive, 33 (82.5%) were negative. There was no significant correlation between RKIP positivity and clinical stage, microscopic subtype or pathological differentiation grade. RKIP positivity correlated inversely with LNM. RKIP may play a role in cervical-cancer genesis and metastasis; RKIP down-regulation was associated with metastatic disease in human cervical cancer.

Epigenetic deregulation of TCF21 inhibits metastasis suppressor KISS1 in metastatic melanoma

Metastatic melanoma is a fatal disease due to the lack of successful therapies and biomarkers for early detection and its incidence has been increasing. Genetic studies have defined recurrent chromosomal aberrations, suggesting the location of either tumor suppressor genes or oncogenes. Transcription factor 21 (TCF21) belongs to the class A of the basic helix-loop-helix family with reported functions in early lung and kidney development as well as tumor suppressor function in the malignancies of the lung and head and neck. In this study, we combined quantitative DNA methylation analysis in patient biopsies and in their derived cell lines to demonstrate that TCF21 expression is downregulated in metastatic melanoma by promoter hypermethylation and TCF21 promoter DNA methylation is correlated with decreased survival in metastatic skin melanoma patients. In addition, the chromosomal location of TCF21 on 6q23-q24 coincides with the location of a postulated metastasis suppressor in melanoma. Functionally, TCF21 binds the promoter of the melanoma metastasis-suppressing gene, KiSS1, and enhances its gene expression through interaction with E12, a TCF3 isoform and with TCF12. Loss of TCF21 expression results in loss of KISS1 expression through loss of direct interaction of TCF21 at the KISS1 promoter. Finally, overexpression of TCF21 inhibits motility of C8161 melanoma cells. These data suggest that epigenetic downregulation of TCF21 is functionally involved in melanoma progression and that it may serve as a biomarker for aggressive tumor behavior.

Expression and prognostic significance of a new tumor metastasis suppressor gene LASS2 in human bladder carcinoma

The LASS2 gene has been identified as a new tumor metastasis suppressor gene and has been seen to correlate with the degree of invasion and recurrence in carcinomas of prostate, breast, liver, ovarian, and pancreas. However, expression and prognostic significance of LASS2 in human bladder carcinoma are largely unknown. In this study, the protein expression of LASS2 in 80 patients with different stages was detected by immunohistochemical staining. The prognostic value of LASS2 in bladder cancers can also be assessed by a long-term follow-up investigation. The mRNA expression level of the LASS2 gene was examined using real-time quantitative PCR (qPCR) in human bladder carcinoma and paired non-tumor bladder tissues, which were obtained from 30 patients who underwent total cystectomy. We found that patients with LASS2-negative bladder cancer were linked to poor clinical prognosis. The expression of LASS2 mRNA was significantly correlated with clinical stage (P < 0.001), depth of tumor invasion (P < 0.001), and recurrence (P < 0.001). Thus, LASS2 expression may be correlated with the development and progression of human bladder carcinoma and may be a prognostic indicator for this carcinoma.

Meta-analysis of multiple microarray datasets reveals a common gene signature of metastasis in solid tumors

Background

Metastasis is the number one cause of cancer deaths. Expression microarrays have been widely used to study metastasis in various types of cancer. We hypothesize that a meta-analysis of publicly available gene expression datasets in various tumor types can identify a signature of metastasis that is common to multiple tumor types. This common signature of metastasis may help us to understand the shared steps in the metastatic process and identify useful biomarkers that could predict metastatic risk.

Methods

We identified 18 publicly available gene expression datasets in the Oncomine database comparing distant metastases to primary tumors in various solid tumors which met our eligibility criteria. We performed a meta-analysis using a modified permutation counting method in order to obtain a common gene signature of metastasis. We then validated this signature in independent datasets using gene set expression comparison analysis with the LS-statistic.

Results

A common metastatic signature of 79 genes was identified in the metastatic lesions compared with primaries with a False Discovery Proportion of less than 0.1. Interestingly, all the genes in the signature, except one, were significantly down-regulated, suggesting that overcoming metastatic suppression may be a key feature common to all metastatic tumors. Pathway analysis of the significant genes showed that the genes were involved in known metastasis-associated pathways, such as integrin signaling, calcium signaling, and VEGF signaling. To validate the signature, we used an additional six expression datasets that were not used in the discovery study. Our results showed that the signature was significantly enriched in four validation sets with p-values less than 0.05.

Conclusions

We have modified a previously published meta-analysis method and identified a common metastatic signature by comparing primary tumors versus metastases in various tumor types. This approach, as well as the gene signature identified, provides important insights to the common metastatic process and a foundation for future discoveries that could have broad application, such as drug discovery, metastasis prediction, and mechanistic studies.

KAI1 gene is engaged in NDRG1 gene-mediated metastasis suppression through the ATF3-NFkappaB complex in human prostate cancer

NDRG1 and KAI1 belong to metastasis suppressor genes, which impede the dissemination of tumor cells from primary tumors to distant organs. Previously, we identified the metastasis promoting transcription factor, ATF3, as a downstream target of NDRG1. Further analysis revealed that the KAI1 promoter contained a consensus binding motif of ATF3, suggesting a possibility that NDRG1 suppresses metastasis through inhibition of ATF3 expression followed by activation of the KAI1 gene. In this report, we found that ectopic expression of NDRG1 was able to augment endogenous KAI1 gene expression in prostate cancer cell lines, whereas silencing NDRG1 was accompanied with significant decrease in KAI1 expression in vitro and in vivo. In addition, our results of ChIP analysis indicate that ATF3 indeed bound to the promoter of the KAI1 gene. Importantly, our promoter-based analysis revealed that ATF3 modulated KAI1 transcription through cooperation with other endogenous transcription factor as co-activator (ATF3-JunB) or co-repressor (ATF3-NFκB). Moreover, loss of KAI1 expression significantly abrogated NDRG1-mediated metastatic suppression in vitro as well as in a spontaneous metastasis animal model, indicating that KA11 is a functional downstream target of the NDRG1 pathway. Our result of immunohistochemical analysis showed that loss of NDRG1 and KAI1 occurs in parallel as prostate cancer progresses. We also found that a combined expression status of these two genes serves as a strong independent prognostic marker to predict metastasis-free survival of prostate cancer patients. Taken together, our result revealed a novel regulatory network of two metastasis suppressor genes, NDRG1 and KAI1, which together concerted metastasis-suppressive activities through an intrinsic transcriptional cascade.

SERPINB5 and AKAP12 - expression and promoter methylation of metastasis suppressor genes in pancreatic ductal adenocarcinoma

BACKGROUND

Early metastasis and infiltration are survival limiting characteristics of pancreatic ductal adenocarcinoma (PDAC). Thus, PDAC is likely to harbor alterations in metastasis suppressor genes that may provide novel diagnostic and therapeutic opportunities. This study investigates a panel of metastasis suppressor genes in correlation to PDAC phenotype and examines promoter methylation for regulatory influence on metastasis suppressor gene expression and for its potential as a diagnostic tool.

METHODS

Metastatic and invasive potential of 16 PDAC cell lines were quantified in an orthotopic mouse model and mRNA expression of 11 metastasis suppressor genes determined by quantitative RT-PCR. Analysis for promoter methylation was performed using methylation specific PCR and bisulfite sequencing PCR. Protein expression was determined by Western blot.

RESULTS

In general, higher metastasis suppressor gene mRNA expression was not consistent with less aggressive phenotypes of PDAC. Instead, mRNA overexpression of several metastasis suppressor genes was found in PDAC cell lines vs. normal pancreatic RNA. Of the investigated metastasis suppressor genes, only higher AKAP12 mRNA expression was correlated with decreased metastasis (P < 0.05) and invasion scores (P < 0.01) while higher SERPINB5 mRNA expression was correlated with increased metastasis scores (P < 0.05). Both genes' promoters showed methylation, but only increased SERPINB5 methylation was associated with loss of mRNA and protein expression (P < 0.05). SERPINB5 methylation was also directly correlated to decreased metastasis scores (P < 0.05).

CONCLUSIONS

AKAP12 mRNA expression was correlated to attenuated invasive and metastatic potential and may be associated with less aggressive phenotypes of PDAC while no such evidence was obtained for the remaining metastasis suppressor genes. Increased SERPINB5 mRNA expression was correlated to increased metastasis and mRNA expression was regulated by methylation. Thus, SERPINB5 methylation was directly correlated to metastasis scores and may provide a diagnostic tool for PDAC.

Inactivation of the WASF3 gene in prostate cancer cells leads to suppression of tumorigenicity and metastases

Background:

The WASF3 protein is involved in cell movement and invasion, and to investigate its role in prostate cancer progression we studied the phenotypic effects of knockdown in primary tumors and cell lines.

Methods:

ShRNA was used to knockdown WASF3 function in prostate cell lines. Cell motility (scratch wound assay), anchorage independent growth and in vivo tumorigenicity and metastasis were then compared between knockdown and wild-type cells.

Results:

Increased levels of expression were seen in high-grade human prostate cancer and in the PC3 and DU145 cell lines. Inactivation of WASF3 using shRNAs reduced cell motility and invasion in these cells and reduced anchorage independent growth in vitro. The loss of motility was accompanied by an associated increase in stress fiber formation and focal adhesions. When injected subcutaneously into severe combined immunodeficiency (SCID) mice, tumor formation was significantly reduced for PC3 and DU145 cells with WASF3 knockdown and in vivo metastasis assays using tail vain injection showed a significant reduction for PC3 and DU145 cells. The loss of the invasion phenotype was accompanied by down-regulation of matrix metalloproteinase 9.

Conclusions:

Overall, these observations demonstrate a critical role for WASF3 in the progression of prostate cancer and identify a potential target to control tumorigenicity and metastasis.

Transiently entrapped circulating tumor cells interact with neutrophils to facilitate lung metastasis development

It is unknown why only a minority of circulating tumor cells trapped in lung capillaries form metastases and involvement of immune cells remains uncertain. A novel model has been developed in this study showing that neutrophils regulate lung metastasis development through physical interaction and anchoring of circulating tumor cells to endothelium. Human melanoma cells were i.v. injected into nude mice leading to the entrapment of many cancer cells; however, 24 hours later, very few remained in the lungs. In contrast, injection of human neutrophils an hour after tumor cell injection increased cancer cell retention by approximately 3-fold. Entrapped melanoma cells produced and secreted high levels of a cytokine called interleukin-8 (IL-8), attracting neutrophils and increasing tethering beta(2) integrin expression by 75% to 100%. Intercellular adhesion molecule-1 on melanoma cells and beta(2) integrin on neutrophils interacted, promoting anchoring to vascular endothelium. Decreasing IL-8 secretion from melanoma cells lowered extracellular levels by 20% to 50%, decreased beta(2) integrin on neutrophils by approximately 50%, and reduced neutrophil-mediated extravasation by 25% to 60%, resulting in approximately 50% fewer melanoma cells being tethered to endothelium and retained in lungs. Thus, transendothelial migration and lung metastasis development decreased by approximately 50%, showing that targeting IL-8 in melanoma cells has the potential to decrease metastasis development by disrupting interaction with neutrophils.

The Expression Patterns of ER, PR, HER2, CK5/6, EGFR, Ki-67 and AR by Immunohistochemical Analysis in Breast Cancer Cell Lines

The molecular classification for breast carcinomas has been used in clinical studies with a simple surrogate panel of immunohistochemistry (IHC) markers. The objective of this current project was to study the molecular classification of commonly used breast cancer cell lines by IHC analysis. Seventeen breast cancer cell lines were harvested, fixed in formalin and made into cell blocks. IHC analyses were performed on each cell block with antibodies to estrogen receptor (ER), progesterone receptor (PR), HER2, EGFR, CK5/6, Ki-67 and androgen receptor (AR). Among the 17 cell lines, MCF-7 and ZR-75-1 fell to Luminal A subtype; BT-474 to Luminal B subtype; SKBR-3, MDA-MD-435 and AU 565 to HER2 over-expression subtype; MDA-MB-231, MCF-12A, HBL 101, HS 598 T, MCF-10A, MCF-10F, BT-20, 468 and BT-483 to basal subtype. MDA-MB-453 belonged to Unclassified subtype. Since each subtype defined by this IHC-based molecular classification does show a distinct clinical outcome, attention should be paid when choosing a cell line for any study.

Disrupting ovarian cancer metastatic colonization: insights from metastasis suppressor studies

Ovarian cancer affects approximately 25,000 women in the United States each year and remains one of the most lethal female malignancies. A standard approach to therapy is surgical cytoreduction, after which the remaining microscopic residual disease is treated with chemotherapy. The vast majority of patients have disease recurrence, underscoring the crucial need for approaches to control the regrowth, or colonization, of tissues after local treatment. Improved therapies require mechanistic information about the process of metastatic colonization, the final step in metastasis, in which cancer cells undergo progressive growth at secondary sites. Studies of metastasis suppressors are providing insights into events controlling metastatic colonization. This paper reviews our laboratory's approach to the identification, characterization, and functional testing of the JNKK1/MKK4 metastasis suppressor in ovarian cancer metastatic colonization. Specifically, we demonstrate that interaction of ovarian caner cells with the omental microenvironment activates JNKK1/MKK4 resulting in decreased proliferation without affecting apoptosis. The potential role of the omental microenvironment, specifically milky spot structures, is also described. It is our goal to provide this work as a usable paradigm that will enable others to study metastasis suppressors in clinical and experimental ovarian cancer metastases.

BRMS1 expression alters the ultrastructural, biomechanical and biochemical properties of MDA-MB-435 human breast carcinoma cells: an AFM and Raman microspectroscopy study

Restoring BReast cancer Metastasis Suppressor 1 (BRMS1) expression suppresses metastasis in MDA-MB-435 human breast carcinoma cells at ectopic sites without affecting tumor formation at orthotopic site in the body. BRMS1 expression induces many phenotypic alterations in 435 cells such as cell adhesion, cytoskeleton rearrangement, and the down regulation of epidermal growth factor receptor (EGFR) expression. In order to better understand the role of cellular biomechanics in breast cancer metastasis, the qualitative and quantitative detection of cellular biomechanics and biochemical composition is urgently needed. In the present work, using atomic force microscopy (AFM) and fluorescent microscopy we revealed that BRMS1 expression in 435 cells induced reorganization of F-actin and caused alteration in cytoarchitectures (cell topography and ultrastructure). Results from AFM observed increase in biomechanical properties which include cell adhesion, cellular spring constant, and Young's modulus in 435/BRMS1 cells. Raman microspectroscopy showed weaker vibrational spectroscopic bands in 435/BRMS1 cells, implying decrease in concentration of cellular biochemical components in these cells. This was despite the similar spectral patterns observed between 435 and 435/BRMS1 cells. This work demonstrated the feasibility of applying AFM and Raman techniques for in situ measurements of the cellular biomechanics and biochemical components of breast carcinoma cells. It provides vital clues in understanding of the role of cellular biomechanics in cancer metastasis, and further the development of new techniques for early diagnosis of breast cancer.

RVB1/RVB2: running rings around molecular biology

RVB1/RVB2 (also known as Pontin/Reptin, TIP49/TIP48, RuvbL1/RuvbL2, ECP54/ECP51, INO80H/INO80J, TIH1/TIH2, and TIP49A/TIP49B) are two highly conserved members of the AAA+ family that are present in different protein and nucleoprotein complexes. Recent studies implicate the RVB-containing complexes in many cellular processes such as transcription, DNA damage response, snoRNP assembly, cellular transformation, and cancer metastasis. In this review, we discuss recent advances in our understanding of RVB-containing complexes and their role in these pathways.

The role of YY1 in reduced HP1alpha gene expression in invasive human breast cancer cells

INTRODUCTION

Heterochromatin protein 1 (HP1) associates with chromatin by binding to histone H3 and contributes to gene silencing. There are three isoforms of HP1 in mammals: HP1alpha, beta, and gamma. Studies have shown that the level of HP1alpha is reduced in invasive human breast cancer cell lines such as MDA-MB-231 and HS578T compared with non-invasive cell lines such as MCF7 and T47D. It is hypothesized that reduced HP1alpha expression may lead to impaired epigenetic silencing of genes that are important in the acquisition of an invasive phenotype. We set out to determine whether reduced expression of HP1alpha in invasive breast cancer cell lines occurs at the level of transcription.

METHODS

We used transient transfection assays to investigate the mechanism of differential transcriptional activity of the human HP1alpha gene promoter in different cell lines. Mutational analysis of putative transcription factor binding sites in an HP1alpha gene reporter construct was performed to identify transcription factors responsible for the differential activity. SiRNA-mediated knockdown and chromatin immunoprecipitation experiments were performed to determine the role of a specific transcription factor in regulating the HP1alpha gene.

RESULTS

The transcription factor yin yang 1 (YY1) was found to play a role in differential transcriptional activity of the HP1alpha gene. Examination of the YY1 protein and mRNA levels revealed that both were reduced in the invasive cell line HS578T compared with MCF7 cells. YY1 knockdown in MCF7 cells resulted in a decreased level of HP1alpha mRNA, indicating that YY1 positively regulates HP1alpha expression. Chromatin immunoprecipitation experiments verified YY1 occupancy at the HP1alpha gene promoter in MCF7 cells but not HS578T cells. Overexpression of YY1 in HS578T cells decreased cell migration in a manner independent of HP1alpha overexpression.

CONCLUSIONS

Our data suggests that a reduction of YY1 expression in breast cancer cells could contribute to the acquisition of an invasive phenotype through increased cell migration as well as by reduced expression of HP1alpha.

Multi-faceted role of HSP40 in cancer

HSP40 (DNAJ) is an understudied family of co-chaperones. The human genome codes for over 41 members of HSP40 family that reside at distinct intracellular locations. Despite their large numbers, little is known about their physiologic roles. Recent research has revealed involvement of some of the DNAJ family members in various types of cancers. In this article we summarize the information about the involvement of human DNAJ family members in various aspects of cancer biology. Furthermore we discuss the potential role of the J domain of DNAJ proteins in cancer biology.

Regulator of calcineurin 1 modulates cancer cell migration in vitro

Metastasis suppressors and other regulators of cell motility play an important role in tumor invasion and metastases. We previously identified that activation of the G protein coupled receptor 54 (GPR54) by the metastasis suppressor metastin inhibits cell migration in association with overexpression of Regulator of calcineurin 1 (RCAN1), an endogenous regulator of calcineurin. Calcineurin inhibitors also blocked cell migration in vitro and RCAN1 protein levels were reduced in nodal metastases in thyroid cancer. The purpose of the current study was to determine directly if RCAN1 functions as a motility suppressor in vitro. Several cancer cell lines derived from different cancer types with different motility rates were evaluated for RCAN1 expression levels. Using these systems we determined that reduction of endogenous RCAN1 using siRNA resulted in an increase in cancer cell motility while expression of exogenous RCAN1 reduced cell motility. In one cell line with a high migratory rate, the stability of exogenously expressed RCAN1 protein was reduced and was rescued by treatment with a proteasome inhibitor. Finally, overexpression of RCAN1 was associated with an increase in cell adhesion to collagen IV and reduced calcineurin activity. In summary, we have demonstrated that the expression of exogenous RCAN1 reduces migration and alters adhesion; and that the loss of endogenous RCAN1 leads to an increase in migration in the examined cancer cell lines. These results are consistent with a regulatory role for RCAN1 in cancer cell motility in vitro.

Immunohistochemical detection of the Raf kinase inhibitor protein in nonneoplastic gastric tissue and gastric cancer tissue

Expression of the Raf kinase inhibitor protein (RKIP), a metastasis suppressor, is high in normal tissues, low in primary cancers, and lowest or absent in metastatic cancers. Here, we studied the expression of RKIP in nonneoplastic gastric tissue and gastric cancer tissue by immunohistochemistry (IHC) and evaluated its role in the genesis and metastasis of gastric cancer. RKIP immunoreactivity was evaluated in 40 samples of nonneoplastic gastric tissues and 75 samples of gastric cancer tissues. Among the 40 samples of nonneoplastic gastric tissue, 35 (87.5%) were positive for RKIP expression and 5 (12.5%) were negative; in the 75 samples of primary gastric cancer tissue, 39 (52%) were positive for RKIP expression and 36 (48%) were negative. Among 26 samples of metastatic lymph node tissues, 5 (19.2%) were positive for RKIP expression and 21 (80.8%) were negative. RKIP expression level was highest in nonneoplastic gastric tissue, low in primary gastric cancer tissue, and lowest or undetectable in metastatic gastric cancer tissue. Our data suggest that RKIP may play a role in the genesis and metastasis of gastric cancer.

BRMS1 contributes to the negative regulation of uPA gene expression through recruitment of HDAC1 to the NF-kappaB binding site of the uPA promoter

The BRMS1 metastasis suppressor was recently shown to negatively regulate NF-kappaB signaling and down regulate NF-kappaB-dependent uPA expression. Here we confirm that BRMS1 expression correlates with reduced NF-kappaB DNA binding activity in independently derived human melanoma C8161.9 cells stably expressing BRMS1. We show that knockdown of BRMS1 expression in these cells using small interfering RNA (siRNA) leads to the reactivation of NF-kappaB DNA binding activity and re-expression of uPA. Further, we confirm that BRMS1 expression does not alter IKKbeta kinase activity suggesting that BRMS1-dependent uPA regulation does not occur through inhibition of the classical upstream activators of NF-kappaB. BRMS1 has been implicated as a corepressor of HDAC1 and consistent with this, we show that BRMS1 promotes HDAC1 recruitment to the NF-kappaB binding site of the uPA promoter and is associated with reduced H3 acetylation. We also confirm that BRMS1 expression stimulates disassociation of p65 from the NF-kappaB binding site of the uPA promoter consistent with its reduced DNA binding activity. These data suggest that BRMS1 recruits HDAC1 to the NF-kappaB binding site of the uPA promoter, modulates histone acetylation of p65 on the uPA promoter, leading to reduced NF-kappaB binding activity on its consensus sequence, and reduced transactivation of uPA expression.

Breast cancer metastasis suppressor 1 (BRMS1) suppresses metastasis and correlates with improved patient survival in non-small cell lung cancer

Breast cancer metastasis suppressor 1 (BRMS1) is a metastasis suppressor gene in several solid tumors. The role of BRMS1 in non-small cell lung cancer (NSCLC) is not well established. To assess in vitro and in vivo metastatic behavior H1299 NSCLC cells stably expressing BRMS1 or a vector control were created. BRMS1 expression significantly decreases both migration and invasion of NSCLC cells in vitro. Importantly, in flank xenografts, BRMS1 suppresses the formation of pulmonary and hepatic metastases but does not significantly affect primary tumor growth. To evaluate whether BRMS1 is related to the progression of NSCLC, we examined BRMS1 expression in human NSCLC. Both BRMS1 mRNA and protein levels are diminished in NSCLC compared to adjacent non-cancerous lung. BRMS1 expression is also lower in squamous cell carcinoma compared to adenocarcinoma. Moreover, preservation of tumor BRMS1 expression is associated with improved patient survival. Thus, BRMS1 functions as a metastasis suppressor and may be a prognostic indicator for human NSCLC.

Cyclophosphamide promotes pulmonary metastasis on mouse lung adenocarcinoma

Cyclophosphamide (CTX), as a common use of chemotherapeutic agent, has some side effects in clinical treatment. In our experiments, we studied CTX-treated T739 mice using histopathology, immunohistochemistry, reverse transcription polymerase chain reaction and Western blot for markers of proliferation, angiogenesis, tumor progression and distant metastasis. As a result, CTX increased the number and area of metastases and tumor embolus in lungs by effecting on the expression of matrix metalloproteinase-2, intercellular adhesion molecule-1 and tissue inhibitor of metalloproteinase-2. Taken together, it indicated that CTX enhanced the process of pulmonary metastasis by the synergistic effect of matrix-degrading proteases and adhesion proteins.

Effects of raf kinase inhibitor protein expression on metastasis and progression of human epithelial ovarian cancer

Loss of function of metastasis suppressor genes is an important step in the progression to a malignant tumor type. Studies in cell culture and animal models have suggested a role of Raf kinase inhibitor protein (RKIP) in suppressing the metastatic spread of prostate cancer, breast cancer, and melanoma cells. However, the function of RKIP in ovarian cancer (OVCA) has not been reported. To explore the potential role of RKIP in epithelial OVCA metastasis, we detected the expression levels of RKIP protein in tissue samples from patients with epithelial OVCA. Consequently, the expression of RKIP is reduced in the poorly differentiated OVCA than in the well-differentiated and moderately differentiated OVCA. In addition, in vitro cell invasion assay indicated that the RKIP expression was inversely associated with the invasiveness of five OVCA cell lines. Consistent with this result, the cell proliferation, anchorage-independent growth, cell adhesion, and invasion were decreased in RKIP overexpressed cells but increased in RKIP down-regulated cells. Further investigation indicated that RKIP inhibited OVCA cell proliferation by altering cell cycle progression rather than promoting apoptosis. Furthermore, the overexpression of RKIP suppressed the ability of human OVCA cells to metastasize when the tumor cells were transplanted into nude mice. Our data show the effect of RKIP on the proliferation, migration, or adhesion of OVCA cells. These results indicate that RKIP is also a metastasis suppressor gene of human epithelial OVCA.

Effects of the Tumor-Leukocyte Microenvironment on Melanoma-Neutrophil Adhesion to the Endothelium in a Shear Flow

The primary cause of cancer mortality is not attributed to primary tumor formation, but rather to the growth of metastases at distant organ sites. Tumor cell adhesion to blood vessel endothelium (EC) and subsequent transendothelial migration within the circulation are critical components of the metastasis cascade. Previous studies have shown polymorphonuclear neutrophils (PMNs) may facilitate melanoma cell adhesion to the EC and subsequent extravasation under flow conditions. The melanoma cell-PMN interactions are found to be mediated by the binding between intercellular adhesion molecule-1 (ICAM-1) on melanoma cells and β(2) integrin on PMNs and by endogenously secreted interleukin 8 (IL-8) within the tumor-leukocyte microenvironment. In this study, the effects of fluid convection on the IL-8-mediated activation of PMNs and the binding kinetics between PMNs and melanoma cells were investigated. Results indicate that the shear rate dependence of PMN-melanoma cell adhesion and melanoma cell extravasation is due, at least partly, to the convection of tumor-secreted proinflammatory cytokine IL-8.

Functional and clinical evidence for NDRG2 as a candidate suppressor of liver cancer metastasis

We searched for potential suppressors of tumor metastasis by identifying the genes that are frequently down-regulated in hepatocellular carcinomas (HCC) while being negatively correlated with clinical parameters relevant to tumor metastasis, and we report here on the identification of N-myc downstream regulated gene 2 (NDRG2) as a promising candidate. NDRG2 expression was significantly reduced in HCC compared with nontumor or normal liver tissues [87.5% (35 of 40) and 62% (62 of 100) at RNA and protein levels, respectively]. Reduction of NDRG2 expression was intimately associated with promoter hypermethylation because its promoter region was found to carry extensively methylated CpG sites in HCC cell lines and primary tumors. Immunohistochemical analysis of NDRG2 protein in 100 HCC patient tissues indicated that NDRG2 expression loss is significantly correlated with aggressive tumor behaviors such as late tumor-node-metastasis (TNM) stage (P = 0.012), differentiation grade (P = 0.024), portal vein thrombi (P = 0.011), infiltrative growth pattern (P = 0.015), nodal/distant metastasis (P = 0.027), and recurrent tumor (P = 0.021), as well as shorter patient survival rates. Ectopically expressed NDRG2 suppressed invasion and migration of a highly invasive cell line, SK-Hep-1, and experimental tumor metastasis in vivo, whereas small interfering RNA-mediated knockdown resulted in increased invasion and migration of a weakly invasive cell line, PLC/PRF/5. In addition, NDRG2 could antagonize transforming growth factor beta1-mediated tumor cell invasion by specifically down-regulating the expression of matrix metalloproteinase 2 and laminin 332 pathway components, with concomitant suppression of Rho GTPase activity. These results suggest that NDRG2 can inhibit extracellular matrix-based, Rho-driven tumor cell invasion and migration and thereby play important roles in suppressing tumor metastasis in HCC.

Epigenetic silencing contributes to the loss of BRMS1 expression in breast cancer

Breast Cancer Metastasis Suppressor 1 (BRMS1) suppresses metastasis of human breast cancer, ovarian cancer and melanoma in athymic mice. Studies have also shown that BRMS1 is significantly downregulated in some breast tumors, especially in metastatic disease. However, the mechanisms which regulate BRMS1 expression are currently unknown. Upon examination of the BRMS1 promoter region by methylation specific PCR (MSP) analysis, we discovered a CpG island (-3477 to -2214), which was found to be hypermethylated across breast cancer cell lines. A panel of 20 patient samples analyzed showed that 45% of the primary tumors and 60% of the matched lymph node metastases, displayed hypermethylation of BRMS1 promoter. Furthermore, we found a direct correlation between the methylation status of the BRMS1 promoter in the DNA isolated from tissues, with the loss of BRMS1 expression assessed by immunohistochemistry. There are several studies investigating the mechanism by which BRMS1 suppresses metastasis; however thus far there is no study that reports the cause(s) of loss of BRMS1 expression in aggressive breast cancer. Here we report for the first time that BRMS1 is a novel target of epigenetic silencing; and aberrant methylation in the BRMS1 promoter may serve as a cause of loss of its expression.