Unraveling the enigmatic complexities of BRMS1-mediated metastasis suppression. FEBS Lett. 2011;585:3185-3190. [PMID: 21827753 DOI: 10.1016/j.febslet.2011.07.045]

DNA methylation markers for risk of metastasis in a cohort of men with localized prostate cancer

Accurately identifying life-threatening prostate cancer (PCa) at time of diagnosis remains an unsolved problem. We evaluated whether DNA methylation status of selected candidate genes can predict the risk of metastasis beyond clinical risk factors in men with untreated PCa. A nested case-control study was conducted among men diagnosed with localized PCa at Kaiser Permanente California between 01/01/1997-12/31/2006 who did not receive curative treatments. Cases were those who developed metastasis within 10 years from diagnosis. Controls were selected using density sampling. Ninety-eight candidate genes were selected from functional categories of cell cycle control, metastasis/tumour suppressors, cell signalling, cell adhesion/motility/invasion, angiogenesis, and immune function, and 41 from pluripotency genes. Cancer DNA from diagnostic biopsy blocks were extracted and analysed. Associations of methylation status were assessed using CpG site level and principal components-based analysis in conditional logistic regressions. In 215 cases and 404 controls, 27 candidate genes were found to be statistically significant in at least one of the two analytical approaches. The agreement between the methods was 25.9% (7 candidate genes, including 2 pluripotency markers). The DNA methylation status of several candidate genes was significantly associated with risk of metastasis in untreated localized PCa patients. These findings may inform future risk prediction models for PCa metastasis beyond clinical characteristics.

A Capped Tudor Domain within a Core Subunit of the Sin3L/Rpd3L Histone Deacetylase Complex Binds to Nucleic Acid G-Quadruplexes

Chromatin-modifying complexes containing histone deacetylase (HDAC) activities play critical roles in the regulation of gene transcription in eukaryotes. These complexes are thought to lack intrinsic DNA-binding activity, but according to a well-established paradigm, they are recruited via protein–protein interactions by gene-specific transcription factors and posttranslational histone modifications to their sites of action on the genome. The mammalian Sin3L/Rpd3L complex, comprising more than a dozen different polypeptides, is an ancient HDAC complex found in diverse eukaryotes. The subunits of this complex harbor conserved domains and motifs of unknown structure and function. Here, we show that Sds3, a constitutively-associated subunit critical for the proper functioning of the Sin3L/Rpd3L complex, harbors a type of Tudor domain that we designate the capped Tudor domain. Unlike canonical Tudor domains that bind modified histones, the Sds3 capped Tudor domain binds to nucleic acids that can form higher-order structures such as G-quadruplexes and shares similarities with the knotted Tudor domain of the Esa1 histone acetyltransferase that was previously shown to bind single-stranded RNA. Our findings expand the range of macromolecules capable of recruiting the Sin3L/Rpd3L complex and draw attention to potentially new biological roles for this HDAC complex.

Perturbation of BRMS1 interactome reveals pathways that impact metastasis

Breast Cancer Metastasis Suppressor 1 (BRMS1) expression is associated with longer patient survival in multiple cancer types. Understanding BRMS1 functionality will provide insights into both mechanism of action and will enhance potential therapeutic development. In this study, we confirmed that the C-terminus of BRMS1 is critical for metastasis suppression and hypothesized that critical protein interactions in this region would explain its function. Phosphorylation status at S237 regulates BRMS1 protein interactions related to a variety of biological processes, phenotypes [cell cycle (e.g., CDKN2A), DNA repair (e.g., BRCA1)], and metastasis [(e.g., TCF2 and POLE2)]. Presence of S237 also directly decreased MDA-MB-231 breast carcinoma migration in vitro and metastases in vivo. The results add significantly to our understanding of how BRMS1 interactions with Sin3/HDAC complexes regulate metastasis and expand insights into BRMS1's molecular role, as they demonstrate BRMS1 C-terminus involvement in distinct protein-protein interactions.

Metastasis Inhibition by Cell Type Specific Expression of BRMS1 Gene under The Regulation of miR200 Family Response Elements

Objective

Specific expression of therapeutic genes in cancer therapy has been per used for many years. One of the innovative strategies that have recently been introduced is employing miRNA response elements (MREs) of microRNAs (whose expression are reduced or inhibited in cancerous cells) into the 3´UTR of the therapeutic genes for their specific expression. Accordingly, MREs of anti-metastatic miRNA family have been used in 3´UTR of the metastasis suppressor gene in the corresponding cells to evaluate the level of metastatic behavior.

Material and Methods

In this experimental study, 3´UTR of the ZEB1 gene with 592 bp length, encompassing multiple MREs of miR-141, miR-429, miR-200b and miR-200c, was employed to replace BRMS1 3´UTR. The obtained vector was then assessed in the context of MCF-10A, MDA-MB231 and MCF-7 cells.

Results

It was shown that the employed MREs are able to up-regulate BRMS expression in the metastatic MDA- MB231 cells (almost 3.5-fold increase), while it was significantly reduced within tumorigenic/non-metastatic MCF-7 cells. Specific expression of BRMS1 in metastatic cells led to a significant reduction in their migratory and invasive characteristics (about 65% and 55%, respectively). Two-tailed student’s t test was utilized for statistical analysis.

Conclusion

It was demonstrated that a chimeric vector containing BRMS1 which is regulated by miR-200 family response element may represent a promising therapeutic tool. This is due to the capability of the chimeric vector for cell type-specific expression of anti-metastatic genes with lowest side-effects. It consequently prohibits the invasive characteristics of metastatic cells.

BRMS1: a multifunctional signaling molecule in metastasis

Despite high mortality rates, molecular understanding of metastasis remains limited. It can be regulated by both pro- and anti-metastasis genes. The metastasis suppressor, breast cancer metastasis suppressor 1 (BRMS1), has been positively correlated with patient outcomes, but molecular functions are still being characterized. BRMS1 has been implicated in focal adhesion kinase (FAK), epidermal growth factor receptor (EGFR), and NF-κB signaling pathways. We review evidence that BRMS1 regulates these vast signaling pathways through chromatin remodeling as a member of mSin3 histone deacetylase complexes.

Nanoparticle-mediated targeted drug delivery for breast cancer treatment

Breast cancer (BC) is the most common malignancy in women worldwide, and one of the deadliest after lung cancer. Currently, standard methods for cancer therapy including BC are surgery followed by chemotherapy or radiotherapy. However, both chemotherapy and radiotherapy often fail to treat BC due to the side effects that these therapies incur in normal tissues and organs. In recent years, various nanoparticles (NPs) have been discovered and synthesized to be able to selectively target tumor cells without causing any harm to the healthy cells or organs. Therefore, NPs-mediated targeted drug delivery systems (DDS) have become a promising technique to treat BC. In addition to their selectivity to target tumor cells and reduce side effects, NPs have other unique properties which make them desirable for cancer treatment such as low toxicity, good compatibility, ease of preparation, high photoluminescence (PL) for bioimaging in vivo, and high loadability of drugs due to their tunable surface functionalities. In this study, we summarize with a critical analysis of the most recent therapeutic studies involving various NPs-mediated DDS as alternatives for the traditional treatment approaches for BC. It will shed light on the significance of NPs-mediated DDS and serve as a guide to seeking for the ideal methodology for future targeted drug delivery for an efficient BC treatment.

The isolated C-terminal nuclear localization sequence of the breast cancer metastasis suppressor 1 is disordered

BRMS1 is a 246-residue-long protein belonging to the family of metastasis suppressors. It is a predominantly nuclear protein, although it can also function in the cytoplasm. At its C terminus, it has a region that is predicted to be a nuclear localization sequence (NLS); this region, NLS2, is necessary for metastasis suppression. We have studied in vitro and in silico the conformational preferences in aqueous solution of a peptide (NLS2-pep) that comprises the NLS2 of BRMS1, to test whether it has a preferred conformation that could be responsible for its function. Our spectroscopic (far-UV circular dichroism, DOSY-NMR and 2D-NMR) and computational (all-atom molecular dynamics) results indicate that NLS2-pep was disordered in aqueous solution. Furthermore, it did not acquire a structure even when experiments were performed in a more hydrophobic environment, such as the one provided by 2,2,2-trifluoroethanol (TFE). The hydrodynamic radius of the peptide in water was identical to that of a random-coil sequence, in agreement with both our molecular simulations and other theoretical predictions. Thus, we suggest that NLS2 is a disordered region, with non pre-formed structure, that participates in metastasis suppression.

The fundamental role of miR-10b in metastatic cancer

Small, non-coding strands of RNA have been identified as a significant player in the pathology of cancer. One of the first miRNAs to be shown as having aberrant expression in cancer was miR-10b. Since the inaugural study on miR-10b, its role as a metastasis promoting factor has been extensively validated. To date, more than 100 studies have been completed on miR-10b and metastasis across 18 cancer types. This immense set of information holds possibilities for novel methods to improve the lives of many. This review outlines what is currently understood of miR-10b's clinical significance, its molecular regulation, and the possible diagnostic and therapeutic methods leveraging miR-10b as a fundamental target in metastatic cancer. Such methods would move us closer to developing a truly individualized therapeutic strategy against cancer and will likely provide unique information about cancer staging, disease outcome, metastatic potential, and ultimately survival.

BRMS1 gene expression may be associated with clinico-pathological features of breast cancer

Our aim is to investigate whether or not the breast cancer metastasis suppressor 1 (BRMS1) gene expression is directly linked to clinico-pathological features of breast cancer. Following a stringent inclusion and exclusion criteria, case–control studies with associations between BRMS1 and breast cancer were selected from articles obtained by way of searches conducted through an electronic database. All statistical analyses were performed with Stata 12.0 (Stata Corp, College Station, TX, U.S.A.). Ultimately, 1,263 patients with breast cancer were found in a meta-analysis retrieved from a total that included 12 studies. Results of our meta-analysis suggested that BRMS1 protein in breast cancer tissues was significantly lower in comparison with normal breast tissues (odds ratio, OR = 0.08, 95% confidence interval (CI) = 0.04–0.15). The BRMS1 protein in metastatic breast cancer tissue was decreased than from that was found in non-metastatic breast cancer tissue (OR = 0.20, 95%CI = 0.13–0.29), and BRMS1 protein in tumor-node-metastasis (TNM) stages 1 and 2 was found to be higher than TNM stages 3 and 4 (OR = 4.62, 95%CI = 2.77–7.70). BRMS1 protein in all three major types of breast cancer was lower than that of control tissues respectively. We also found strong correlations between BRMS1 mRNA levels and TNM stage and tumor size. The results our meta-analysis showed that reduction in BRMS1 expression level was linked directly to clinico-pathological features of breast cancer significantly; therefore, suggesting the loss of expression or reduced levels of BRMS1 is potentially a strong indicator of the metastatic capacity of breast cancer with poor prognosis.

Homeobox‑containing protein 1 loss is associated with clinicopathological performance in glioma

Homeobox-containing protein 1 (HMBOX1) is a novel member of the homeobox family, and abnormal expression of HMBOX1 has been observed in several types of carcinoma. A total of 144 cases of confirmed glioma diagnoses were included in the present study. Grading was performed according to the World Health Organization (WHO) grading system for central nervous system neoplasm. Immunohistochemical staining of HMBOX1, proliferation marker protein Ki‑67 (Ki‑67) and microvessel density (MVD) was performed, and scores were calculated. HMBOX1 mRNA levels were detected using the reverse transcription quantitative polymerase chain reaction. It was identified that the expression of HMBOX1 was reduced in glioma tissue compared with normal brain tissue (P<0.05). The expression of HMBOX1 was downregulated significantly in WHO grade IV tumors compared with WHO grades II and III (P<0.05). HMBOX1 expression was significantly correlated with WHO grade, Karnofsky Performance Score, MVD and Ki‑67 expression; however, not associated with age or gender. Log‑rank testing did not demonstrate that HMBOX1 expression was associated with prognosis. In conclusion, HMBOX1 may be a potential diagnostic marker in glioma.

Gene promoter methylation and protein expression of BRMS1 in uterine cervix in relation to high-risk human papilloma virus infection and cancer

Cervical cancer is strongly related to certain high-risk types of human papilloma virus infection. Breast cancer metastasis suppressor 1 (BRMS1) is a tumor suppressor gene, its expression being regulated by DNA promoter methylation in several types of cancers. This study aims to evaluate the methylation status of BRMS1 promoter in relation to high-risk types of human papilloma virus infection and the development of pre-cancerous lesions and describe the pattern of BRMS1 protein expression in normal, high-risk types of human papilloma virus-infected pre-cancerous and malignant cervical epithelium. We compared the methylation status of BRMS1 in cervical smears of 64 women with no infection by high-risk types of human papilloma virus to 70 women with proven high-risk types of human papilloma virus infection, using real-time methylation-specific polymerase chain reaction. The expression of BRMS1 protein was described by immunohistochemistry in biopsies from cervical cancer, pre-cancerous lesions, and normal cervices. Methylation of BRMS1 promoter was detected in 37.5% of women with no high-risk types of human papilloma virus infection and was less frequent in smears with high-risk types of human papilloma virus (11.4%) and in women with pathological histology (cervical intraepithelial neoplasia) (11.9%). Methylation was detected also in HeLa cervical cancer cells. Immunohistochemistry revealed nuclear BRMS1 protein staining in normal high-risk types of human papilloma virus-free cervix, in cervical intraepithelial neoplasias, and in malignant tissues, where staining was occasionally also cytoplasmic. In cancer, expression was stronger in the more differentiated cancer blasts. In conclusion, BRMS1 promoter methylation and aberrant protein expression seem to be related to high-risk types of human papilloma virus-induced carcinogenesis in uterine cervix and is worthy of further investigation.

Breast Cancer Metastasis Suppressor 1 (BRMS1): Robust Biological and Pathological Data, But Still Enigmatic Mechanism of Action

Metastasis requires coordinated expression of multiple genetic cassettes, often via epigenetic regulation of gene transcription. BRMS1 blocks metastasis, but not orthotopic tumor growth in multiple tumor types, presumably via SIN3 chromatin remodeling complexes. Although there is an abundance of strong data supporting BRMS1 as a metastasis suppressor, the mechanistic data directly connecting molecular pathways with inhibition of particular steps in metastasis are not well defined. In this review, the data for BRMS1-mediated metastasis suppression in multiple tumor types are discussed along with the steps in metastasis that are inhibited.

Breast cancer metastasis suppressor 1 (BRMS1) attenuates TGF-β1-induced breast cancer cell aggressiveness through downregulating HIF-1α expression

Background

Cancer metastasis is a multi-step event including epithelial-to-mesenchymal transition (EMT). Breast cancer metastasis suppressor 1 (BRMS1) is a novel metastasis suppressor protein without anti-proliferating activity. However, a detailed underlying mechanism by which BRMS1 attenuates cancer cell EMT and invasion remained to be answered. In the present study, we report an additional mechanism by which BRMS1 attenuates Transforming growth factor-beta1 (TGF-β1)-induced breast cancer cell EMT and invasion.

Methods

Experimental analysis involving chromosome immunoprecipitation (ChIP) and luciferase reporter assays were used to validate hypoxia inducible factor-1alpha (HIF-1α) as a transcriptional regulator of TWIST1 and Snail. Quantitative RT-PCR was used to analyze transcript expression. Immunoblotting and immunofluorescence were used to analyze protein expression. Matrigel-coated in vitro invasion insert was used to analyze cancer cell invasion.

Results

BRMS1 strongly inhibited TGF-β1-induced breast cancer cell EMT and invasion. Unexpectedly, we observed that BRMS1 downregulates not only TWIST1 but also Snail expression, thereby inhibiting breast cancer cell invasion. In addition, we provide evidence that HIF-1α is required for Snail and TWIST1 expression. Further, BRMS1 reduced TGF-β1-induced HIF-1α transcript expression through inactivation of nuclear factor kappaB (NF-κB).

Conclusion

Collectively, the present study demonstrates a mechanical cascade of BRMS1 suppressing cancer cell invasion through downregulating HIF-1α transcript and consequently reducing Snail and TWIST1 expression.

Unusual Suspects in the Twilight Zone Between the Hsp90 Interactome and Carcinogenesis

The molecular chaperone Hsp90 has attracted a lot of interest in cancer research ever since cancer cells were found to be more sensitive to Hsp90 inhibition than normal cells. Why that is has remained a matter of debate and is still unclear. In addition to increased Hsp90 dependence for some mutant cancer proteins and modifications of the Hsp90 machinery itself, a number of other characteristics of cancer cells probably contribute to this phenomenon; these include aneuploidy and overall increased numbers and levels of defective and mutant proteins, which all contribute to perturbed proteostasis. Work over the last two decades has demonstrated that many cancer-related proteins are Hsp90 clients, and yet only few of them have been extensively investigated, selected either on the basis of their obvious function as cancer drivers or because they proved to be convenient biomarkers for monitoring the effects of Hsp90 inhibitors. The purpose of our review is to go beyond these "usual suspects." We established a workflow to select poorly studied proteins that are related to cancer processes and qualify as Hsp90 clients. By discussing and taking a fresh look at these "unusual suspects," we hope to stimulate others to revisit them as novel therapeutic targets or diagnostic markers.

Structural insights into the assembly of the histone deacetylase-associated Sin3L/Rpd3L corepressor complex

Acetylation is correlated with chromatin decondensation and transcriptional activation, but its regulation by histone deacetylase (HDAC)-bearing corepressor complexes is poorly understood. Here, we describe the mechanism of assembly of the mammalian Sin3L/Rpd3L complex facilitated by Sds3, a conserved subunit deemed critical for proper assembly. Sds3 engages a globular, helical region of the HDAC interaction domain (HID) of the scaffolding protein Sin3A through a bipartite motif comprising a helix and an adjacent extended segment. Sds3 dimerizes through not only one of the predicted coiled-coil motifs but also, the segment preceding it, forming an ∼ 150-Å-long antiparallel dimer. Contrary to previous findings in yeast, Sin3A rather than Sds3 functions in recruiting HDAC1 into the complex by engaging the latter through a highly conserved segment adjacent to the helical HID subdomain. In the resulting model for the ternary complex, the two copies of the HDACs are situated distally and dynamically because of a natively unstructured linker connecting the dimerization domain and the Sin3A interaction domain of Sds3; these features contrast with the static organization described previously for the NuRD (nucleosome remodeling and deacetylase) complex. The Sds3 linker features several conserved basic residues that could potentially maintain the complex on chromatin by nonspecific interactions with DNA after initial recruitment by sequence-specific DNA-binding repressors.

Autocrine/Paracrine Human Growth Hormone-stimulated MicroRNA 96-182-183 Cluster Promotes Epithelial-Mesenchymal Transition and Invasion in Breast Cancer

Human growth hormone (hGH) plays critical roles in pubertal mammary gland growth, development, and sexual maturation. Accumulated studies have reported that autocrine/paracrine hGH is an orthotopically expressed oncoprotein that promotes normal mammary epithelial cell oncogenic transformation. Autocrine/paracrine hGH has also been reported to promote mammary epithelial cell epithelial-mesenchymal transition (EMT) and invasion. However, the underlying mechanism remains largely obscure. MicroRNAs (miRNAs) are reported to be involved in regulation of multiple cellular functions of cancer. To determine whether autocrine/paracrine hGH promotes EMT and invasion through modulation of miRNA expression, we performed microarray profiling using MCF-7 cells stably expressing wild type or a translation-deficient hGH gene and identified miR-96-182-183 as an autocrine/paracrine hGH-regulated miRNA cluster. Forced expression of miR-96-182-183 conferred on epithelioid MCF-7 cells a mesenchymal phenotype and promoted invasive behavior in vitro and dissemination in vivo. Moreover, we observed that miR-96-182-183 promoted EMT and invasion by directly and simultaneously suppressing BRMS1L (breast cancer metastasis suppressor 1-like) gene expression. miR-96 and miR-182 also targeted GHR, providing a potential negative feedback loop in the hGH-GHR signaling pathway. We further demonstrated that autocrine/paracrine hGH stimulated miR-96-182-183 expression and facilitated EMT and invasion via STAT3 and STAT5 signaling. Consistent with elevated expression of autocrine/paracrine hGH in metastatic breast cancer tissue, miR-96-182-183 expression was also remarkably enhanced. Hence, we delineate the roles of the miRNA-96-182-183 cluster and elucidate a novel hGH-GHR-STAT3/STAT5-miR-96-182-183-BRMS1L-ZEB1/E47-EMT/invasion axis, which provides further understanding of the mechanism of autocrine/paracrine hGH-stimulated EMT and invasion in breast cancer.

BRMS1L suppresses breast cancer metastasis by inducing epigenetic silence of FZD10

BRMS1L (breast cancer metastasis suppressor 1 like, BRMS1-like) is a component of Sin3A-histone deacetylase (HDAC) co-repressor complex that suppresses target gene transcription. Here we show that reduced BRMS1L in breast cancer tissues is associated with metastasis and poor patient survival. Functionally, BRMS1L inhibits breast cancer cells migration and invasion by inhibiting epithelial-mesenchymal transition. These effects are mediated by epigenetic silencing of FZD10, a receptor for Wnt signalling, through HDAC1 recruitment and histone H3K9 deacetylation at the promoter. Consequently, BRMS1L-induced FZD10 silencing inhibits aberrant activation of WNT3-FZD10-β-catenin signalling. Furthermore, BRMS1L is a target of miR-106b and miR-106b upregulation leads to BRMS1L reduction in breast cancer cells. RNA interference-mediated silencing of BRMS1L expression promotes metastasis of breast cancer xenografts in immunocompromised mice, whereas ectopic BRMS1L expression inhibits metastasis. Therefore, BRMS1L provides an epigenetic regulation of Wnt signalling in breast cancer cells and acts as a breast cancer metastasis suppressor.

Imaging of epidermal growth factor receptor on single breast cancer cells using surface-enhanced Raman spectroscopy

Epidermal growth factor receptor (EGFR) is widely used as a biomarker for pathological grading and therapeutic targeting of human cancers. This study investigates expression, spatial distribution as well as the endocytosis of EGFR in single breast cancer cells using surface-enhanced Raman spectroscopy (SERS). By incubating anti-EGFR antibody conjugated SERS nanoprobes with an EGFR-over-expressing cancer cell line, A431, EGFR localization was measured over time and found to be located primarily at the cell surface. To further validate the constructed SERS probes, we applied this SERS probes to detect the EGFR expression on breast cancer cells (MDA-MB-435, MDA-MB-231) and their counterpart cell lines in which EGFR expression was down-regulated by breast cancer metastasis suppressor 1 (BRMS1). The results showed that SERS method not only confirms immunoblot data measuring EGFR levels, but also adds new insights regarding EGFR localization and internalization in living cells which is impossible in immunoblot method. Thus, SERS provides a powerful new tool to measure biomarkers in living cancer cells.

Microenvironmental Influences on Metastasis Suppressor Expression and Function during a Metastatic Cell's Journey

Metastasis is the process of primary tumor cells breaking away and colonizing distant secondary sites. In order for a tumor cell growing in one microenvironment to travel to, and flourish in, a secondary environment, it must survive a series of events termed the metastatic cascade. Before departing the primary tumor, cells acquire genetic and epigenetic changes that endow them with properties not usually associated with related normal differentiated cells. Those cells also induce a subset of bone marrow-derived stem cells to mobilize and establish pre-metastatic niches [1]. Many tumor cells undergo epithelial-to-mesenchymal transition (EMT), where they transiently acquire morphologic changes, reduced requirements for cell-cell contact and become more invasive [2]. Invasive tumor cells eventually enter the circulatory (hematogenous) or lymphatic systems or travel across body cavities. In transit, tumor cells must resist anoikis, survive sheer forces and evade detection by the immune system. For blood-borne metastases, surviving cells then arrest or adhere to endothelial linings before either proliferating or extravasating. Eventually, tumor cells complete the process by proliferating to form a macroscopic mass [3].Up to 90 % of all cancer related morbidity and mortality can be attributed to metastasis. Surgery manages to ablate most primary tumors, especially when combined with chemotherapy and radiation. But if cells have disseminated, survival rates drop precipitously. While multiple parameters of the primary tumor are predictive of local or distant relapse, biopsies remain an imperfect science. The introduction of molecular and other biomarkers [4, 5] continue to improve the accuracy of prognosis. However, the invasive procedure introduces new complications for the patient. Likewise, the heterogeneity of any tumor population [3, 6, 7] means that sampling error (i.e., since it is impractical to examine the entire tumor) necessitates further improvements.In the case of breast cancer, for example, women diagnosed with stage I diseases (i.e., no evidence of invasion through a basement membrane) still have a ~30 % likelihood of developing distant metastases [8]. Many physicians and patients opt for additional chemotherapy in order to "mop up" cells that have disseminated and have the potential to grow into macroscopic metastases. This means that ~ 70 % of patients receive unnecessary therapy, which has undesirable side effects. Therefore, improving prognostic capability is highly desirable.Recent advances allow profiling of primary tumor DNA sequences and gene expression patterns to define a so-called metastatic signature [9-11], which can be predictive of patient outcome. However, the genetic changes that a tumor cell must undergo to survive the initial events of the metastatic cascade and colonize a second location belie a plasticity that may not be adequately captured in a sampling of heterogeneous tumors. In order to tailor or personalize patient treatments, a more accurate assessment of the genetic profile in the metastases is needed. Biopsy of each individual metastasis is not practical, safe, nor particularly cost-effective. In recent years, there has been a resurrection of the notion to do a 'liquid biopsy,' which essentially involves sampling of circulating tumor cells (CTC) and/or cell free nucleic acids (cfDNA, including microRNA (miRNA)) present in blood and lymph [12-16].The rationale for liquid biopsy is that tumors shed cells and/or genetic fragments into the circulation, theoretically making the blood representative of not only the primary tumor but also distant metastases. Logically, one would predict that the proportion of CTC and/or cfDNA would be proportionate to the likelihood of developing metastases [14]. While a linear relationship does not exist, the information within CTC or cfDNA is beginning to show great promise for enabling a global snapshot of the disease. However, the CTC and cfDNA are present at extremely low levels. Nonetheless, newer technologies capture enough material to enrich and sequence the patient's DNA or quantification of some biomarkers.Among the biomarkers showing great promise are metastasis suppressors which, by definition, block a tumor cell's ability to complete the metastatic process without prohibiting primary tumor growth [17]. Since the discovery of the first metastasis suppressor, Nm23, more than 30 have been functionally characterized. They function at various stages of the metastatic cascade, but their mechanisms of action, for the most part, remain ill-defined. Deciphering the molecular interactions of functional metastasis suppressors may provide insights for targeted therapies when these regulators cease to function and result in metastatic disease.In this brief review, we summarize what is known about the various metastasis suppressors and their functions at individual steps of the metastatic cascade (Table 1). Some of the subdivisions are rather arbitrary in nature, since many metastasis suppressors affect more than one step in the metastatic cascade. Nonetheless what emerges is a realization that metastasis suppressors are intimately associated with the microenvironments in which cancer cells find themselves [18].

Metastasis suppressors in breast cancers: mechanistic insights and clinical potential

For the most part, normal epithelial cells do not disseminate to other parts of the body and proliferate, as do metastatic cells. Presumably, a class of molecules-termed metastasis suppressors-are involved in this homeostatic control. Metastasis suppressors are, by definition, cellular factors that, when re-expressed in metastatic cells, functionally inhibit metastasis without significantly inhibiting tumor growth. In this brief review, we catalog known metastasis suppressors, what is known about their mechanism(s) of action, and experimental and clinical associations to date.

Expression of metastasis suppressor BRMS1 in breast cancer cells results in a marked delay in cellular adhesion to matrix

Metastatic dissemination is a multi-step process that depends on cancer cells' ability to respond to microenvironmental cues by adapting adhesion abilities and undergoing cytoskeletal rearrangement. Breast Cancer Metastasis Suppressor 1 (BRMS1) affects several steps of the metastatic cascade: it decreases survival in circulation, increases susceptibility to anoikis, and reduces capacity to colonize secondary organs. In this report, BRMS1 expression is shown to not significantly alter expression levels of integrin monomers, while time-lapse and confocal microscopy revealed that BRMS1-expressing cells exhibited reduced activation of both β1 integrin and focal adhesion kinase, and decreased localization of these molecules to sites of focal adhesions. Short-term plating of BRMS1-expressing cells onto collagen or fibronectin markedly decreased cytoskeletal reorganization and formation of cellular adhesion projections. Under 3D culture conditions, BRMS1-expressing cells remained rounded and failed to reorganize their cytoskeleton and form invasive colonies. Taken together, BRMS1-expressing breast cancer cells are greatly attenuated in their ability to respond to microenvironment changes. © 2013 Wiley Periodicals, Inc.

Lung cancer with gastrointestinal metastasis - review of theories of metastasis with three rare case descriptions

Approximately 1 in 14 men and women during their lifetime will be diagnosed with lung cancer, which is the leading cause of cancer-related mortality in the world. As of January 1, 2008, there were about 373,500 men and women living with lung cancer in the United States. Fewer than 60,000 of these are estimated to be alive by January 2013, reflecting a poor overall 5-year relative survival rate of under 16 %. With metastatic cancer, the overall 5-year survival is meager 4 %. On the other hand, the overall five-year survival is over 50 % when the cancer is still in the localized stage. However, unfortunately, more than half of cases of lung cancer are diagnosed at an advanced stage Howlader et al. (2010). Cancer metastasis, the single most critical prognostic factor, is still poorly understood and a highly complex phenomenon. The most common sites of lung cancer metastasis are the lymph nodes, liver, adrenals, brain and bones. The gastrointestinal (GI) tract is an exceptionally rare site of metastasis; with only a handful of cases reported in the literature Centeno et al. (Lung Cancer, 18: 101-105, 1997); Hirasaki et al. (World J Gastroenterol, 14: 5481-5483, 2008); Carr and Boulos (Br J Surg, 83: 647, 1996); Otera et al. (Eur Respir Rev, 19: 248-252, 2010); Antler et al. (Cancer, 49: 170-172, 1982); Fujiwara et al. (Gen Thorac Cardiovasc Surg, 59: 748-752, 2011); Stinchcombe et al. (J Clin Oncol, 24: 4939-4940, 2006); John et al. (J Postgrad Med, 48: 199-200, 2002); Carroll and Rajesh (Eur J Cardiothorac Surg, 19: 719-720, 2001); Brown et al. (Dis Colon Rectum, 23: 343-345, 1980). We report three cases of non-small cell (squamous cell) lung cancer with GI tract metastasis-two in the colon and one in the jejunum. Then we present a review of literature exploring various theories of metastasis, as an attempt to understand the reason of preferential tumor metastasis.

Metastasis suppression by BRMS1 associated with SIN3 chromatin remodeling complexes

Epigenetic regulation of gene transcription by histone modification and chromatin remodeling has been linked to many biological and pathological events including cancer metastasis. Breast cancer metastasis suppressor 1 (BRMS1) interacts with SIN3 chromatin remodeling complexes, and, upon forced expression in metastatic cells, a nearly complete suppression of metastasis is noted without preventing primary tumor growth. The data for BRMS1-mediated metastasis suppression and SIN3 interaction are clear; however, connecting the inhibition directly to the association of BRMS1 with SIN3 complexes is currently not well defined. Considering the recent advancements in developing epigenetic drugs for cancer therapy, an improved understanding of how the interactions between BRMS1 and SIN3 regulate the process of metastasis should lead to novel therapies specifically targeting the most deadly aspect of tumor progression. In this article, the data for BRMS1-mediated metastasis suppression are reviewed with a focus on how the SIN3 chromatin remodeling complexes may be functionally involved.

Breast cancer metastasis suppressor-1 promoter methylation in primary breast tumors and corresponding circulating tumor cells

Breast cancer metastasis suppressor-1 (BRMS1) differentially regulates the expression of multiple genes, leading to metastasis suppression without affecting orthotopic tumor growth. For the first time, BRMS1 promoter methylation was evaluated as a prognostic biomarker in primary breast tumors and a subset of corresponding circulating tumor cells (CTC). Formalin-fixed paraffin embedded samples were analyzed for BRMS1 methylation status using methylation-specific PCR in a human specimen cohort consisting of noncancerous tissues, benign fibroadenomas, and primary breast tumors, including some with adjacent noncancerous tissues. Peripheral blood mononuclear cells from a large subset of these patients were fixed in cytospins and analyzed. In addition, BRMS1 expression in cytospins was examined by double-immunofluorescence using anti-BRMS1 and pan-cytokeratin antibodies. BRMS1 promoter methylation was not detected in noncancerous breast tissues or benign fibroadenomas; however, methylation was observed in more than a third of primary breast tumors. Critically, BRMS1 promoter methylation in primary tumors was significantly associated with reduced disease-free survival with a trend toward reduced overall survival. Similarly, a third of cytospin samples were positive for the presence of CTCs, and the total number of detected CTCs was 41. Although a large fraction of CTCs were negative or maintained low expression of BRSM1, promoter methylation was observed in a small fraction of samples, implying that BRSM1 expression in CTCs was either downregulated or heterogeneous. In summary, these data define BRMS1 promoter methylation in primary breast tumors and associated CTCs.

IMPLICATIONS

This study indicates that BRSM1 promoter methylation status has biomarker potential in breast cancer.

Regulation of breast cancer tumorigenesis and metastasis by miRNAs

miRNAs are a family of 17- to 23-nucleotide noncoding small RNAs that primarily function as gene expression fine regulators. A number of studies have shown that miRNAs play an important role in breast tumorigenesis, metastasis, proliferation and differentiation of breast cancer stem cells. This short review summarizes the progression of miRNA-mediated breast tumorigenesis and metastasis through various signaling pathways associated with drug resistance.

Cloning and characterization of a novel human BRMS1 transcript variant in hepatocellular carcinoma cells

Breast cancer metastasis suppressor 1 (BRMS1) is able to suppress tumor metastasis without affecting primary tumor growth in various cancers. Here, we report a novel transcript variant of human BRMS1, termed BRMS1.vh. BRMS1.vh is identical to the major BRMS1 variant (BRMS1.v1) except for missing base pairs 683-775, encoding a 215-amino acid protein lacking a functional nuclear localization sequence. Expression of BRMS1.vh in hepatocellular carcinoma (HCC) cells suppressed NF-κB signaling pathway, sensitized cells to apoptotic stimuli, leading to suppressed tumor growth. Taken together, our results suggest a potential role for BRMS1.vh in regulating cell apoptosis and tumor growth in HCC.

The C-terminal putative nuclear localization sequence of breast cancer metastasis suppressor 1, BRMS1, is necessary for metastasis suppression

Breast cancer metastasis suppressor 1 (BRMS1) is a predominantly nuclear protein that suppresses metastasis in multiple human and murine carcinoma cell lines. BRMS1 interacts with several nuclear proteins including SIN3:HDAC chromatin remodeling complexes that are involved in repressing transcription. However, recent reports suggest BRMS1 may function in the cytoplasm. BRMS1 has two predicted nuclear localization sequences (NLS) that are located near the C-terminus (amino acids 198–205 and 238–244, NLS1 and NLS2 respectively). We hypothesized that nuclear localization sequences of BRMS1 were essential for BRMS1 mediated metastasis suppression. Replacement of NLS2 with NLS1 (BRMS1^NLS1,1), truncation at 238 (BRMS1^ΔNLS2), or switching the location of NLS1 and NLS2 (BRMS1^NLS2,1) did not affect nuclear localization; but, replacement of NLS1 with NLS2 (BRMS1^NLS2,2) or truncation at 197 (BRMS1^ΔNLS which removes both NLS) promoted cytoplasmic localization. MDA-MB-231 human metastatic breast cancer cells transduced with BRMS1^NLS1,1, BRMS1^NLS2,2 or BRMS1^NLS2,1 were evaluated for metastasis suppression in an experimental xenograft mouse model. Interestingly, while NLS2 was not necessary for nuclear localization, it was found to be important for metastasis suppression since BRMS1^NLS2,2 suppressed metastasis by 85%. In contrast, BRMS1^NLS2,1 and BRMS1^NLS1,1 did not significantly suppress metastasis. Both BRMS1 and BRMS1^NLS2,2 co-immunoprecipitated with SIN3A in the nucleus and cytoplasm; however, BRMS1^NLS1,1 and BRMS1^NLS2,1 were associated with SIN3A in the nucleus only. Moreover, BRMS1 and BRMS1^NLS2,2, but not BRMS1^NLS1,1 and BRMS1^NLS2,1, down-regulated the pro-metastatic microRNA, miR-10b. Together, these data demonstrate an important role for NLS2 in the cytoplasm that is critical for metastasis suppression and is distinct from nuclear localization.

Transcriptional corepressors in cancer: emerging targets for therapeutic intervention

The normal cell transcriptional process entails a high degree of combinatorial effects and time-dependent "flexibility" to translate cellular signaling into differential gene expression levels. Transcriptional corepressors can function as histone-modifying enzymes to regulate epigenetic events, modulate chromatin structure, and hence control transcriptional activity. Various corepressor complexes have been described; qualitative and quantitative alterations of corepressors can crucially influence the transcriptional output of both normal and malignant cells. Because these molecules can exert epigenetic control of tumorigenic signaling pathways, they can be considered potential regulators of cancer cell-related phenomena. Alterations of the expression level and/or function of transcriptional corepressors have been reported in a wide range of human cancers; thus, corepressors may present rational therapeutic targets as well as potential biomarkers of response to selective therapeutic interventions. Deeper insights into the context-specific and time-specific physical connections among transcription factors, coregulators, and gene regulatory elements, as well as epigenetic modifications, and their interactions, can enhance the capacity to interfere with small molecules that may restore the normal transcriptome/interactome in a cancer cell. There are several conceivable mechanisms of corepressor targeting in cancer that create enthusiasm. However, design, discovery, and testing of such innovative treatment approaches require extensive elaboration before they can achieve practical implementation in the clinic.

Role of breast cancer metastasis suppressor 1 in digestive system neoplasms

Breast cancer metastasis suppressor 1 (BRMS1) is a tumor metastasis suppressor discovered in breast carcinoma cells in 2000. It can reduce the metastasis potential of tumor cells without affecting the growth of orthotopic tumor. BRMS1 is lowly expressed or not at all in metastases of melanoma, bladder carcinoma, pheochromocytoma, ovarian cancer, non-small cell lung cancer, endometrial cancer, nasal and paranasal sinus carcinoma. Malignant tumors have become one of the most serious diseases endangering human health, and digestive system neoplasms are the most common malignant tumors in China. Elucidation of the role of BRMS1 will certainly provide a potential theoretical basis for the molecular diagnosis, targeted therapy, and prognosis evaluation of tumor metastases. In this review, we will summarize recent progress in understanding the role of BRMS1 in digestive system neoplasms.

Communication between host organism and cancer cells is transduced by systemic sphingosine kinase 1/sphingosine 1-phosphate signalling to regulate tumour metastasis

Mechanisms by which cancer cells communicate with the host organism to regulate lung colonization/metastasis are unclear. We show that this communication occurs via sphingosine 1-phosphate (S1P) generated systemically by sphingosine kinase 1 (SK1), rather than via tumour-derived S1P. Modulation of systemic, but not tumour SK1, prevented S1P elevation, and inhibited TRAMP-induced prostate cancer growth in TRAMP^+/+SK1^−/− mice, or lung metastasis of multiple cancer cells in SK1^−/− animals. Genetic loss of SK1 activated a master metastasis suppressor, Brms1 (breast carcinoma metastasis suppressor 1), via modulation of S1P receptor 2 (S1PR2) in cancer cells. Alterations of S1PR2 using pharmacologic and genetic tools enhanced Brms1. Moreover, Brms1 in S1PR2^−/− MEFs was modulated by serum S1P alterations. Accordingly, ectopic Brms1 in MB49 bladder cancer cells suppressed lung metastasis, and stable knockdown of Brms1 prevented this process. Importantly, inhibition of systemic S1P signalling using a novel anti-S1P monoclonal antibody (mAb), Sphingomab, attenuated lung metastasis, which was prevented by Brms1 knockdown in MB49 cells. Thus, these data suggest that systemic SK1/S1P regulates metastatic potential via regulation of tumour S1PR2/Brms1 axis.

Targeting transcription factor corepressors in tumor cells

By being the "integration" center of transcriptional control as they move and target transcription factors, corepressors fine-tune the epigenetic status of the nucleus. Many of them utilize enzymatic activities to modulate chromatin through histone modification or chromatin remodeling. The clinical and etiological relevance of the corepressors to neoplastic growth is increasingly being recognized. Aberrant expression or function (both loss and gain of) of corepressors has been associated with malignancy and contribute to the generation of transcriptional "inflexibility" manifested as distorted signaling along certain axes. Understanding and predicting the consequences of corepressor alterations in tumor cells has diagnostic and prognostic value, and also have the capacity to be targeted through selective epigenetic regimens. Here, we evaluate corepressors with the most promising therapeutic potential based on their physiological roles and involvement in malignant development, and also highlight areas that can be exploited for molecular targeting of a large proportion of clinical cancers and their complications.

Cytoplasmic BRMS1 expression in malignant melanoma is associated with increased disease-free survival

Background/aims

Breast cancer metastasis suppressor 1 (BRMS1) blocks metastasis in melanoma xenografts; however, its usefulness as a biomarker in human melanomas has not been widely studied. The goal was to measure BRMS1 expression in benign nevi, primary and metastatic melanomas and evaluate its impact on disease progression and prognosis.

Methods

Paraffin-embedded tissue from 155 primary melanomas, 69 metastases and 15 nevi was examined for BRMS1 expression using immunohistochemistry. siRNA mediated BRMS1 down-regulation was used to study impact on invasion and migration in melanoma cell lines.

Results

A significantly higher percentage of nevi (87%), compared to primary melanomas (20%) and metastases (48%), expressed BRMS1 in the nucelus (p < 0.0001). Strong nuclear staining intensity was observed in 67% of nevi, and in 9% and 24% of the primary and metastatic melanomas, respectively (p < 0.0001). Comparable cytoplasmic expression was observed (nevi; 87%, primaries; 86%, metastases; 72%). However, a decline in cytoplasmic staining intensity was observed in metastases compared to nevi and primary tumors (26%, 47%, and 58%, respectively, p < 0.0001). Score index (percentage immunopositive celles multiplied with staining intensity) revealed that high cytoplasmic score index (≥ 4) was associated with thinner tumors (p = 0.04), lack of ulceration (p = 0.02) and increased disease-free survival (p = 0.036). When intensity and percentage BRMS1 positive cells were analyzed separately, intensity remained associated with tumor thickness (p = 0.024) and ulceration (p = 0.004) but was inversely associated with expression of proliferation markers (cyclin D3 (p = 0.008), cyclin A (p = 0.007), and p21^Waf1/Cip1 (p = 0.009)). Cytoplasmic score index was inversely associated with nuclear p-Akt (p = 0.013) and positively associated with cytoplasmic p-ERK1/2 expression (p = 0.033). Nuclear BRMS1 expression in ≥ 10% of primary melanoma cells was associated with thicker tumors (p = 0.016) and decreased relapse-free period (p = 0.043). Nuclear BRMS1 was associated with expression of fatty acid binding protein 7 (FABP7; p = 0.011), a marker of invasion in melanomas. In line with this, repression of BRMS1 expression reduced the ability of melanoma cells to migrate and invade in vitro.

Conclusion

Our data suggest that BRMS1 is localized in cytoplasm and nucleus of melanocytic cells and that cellular localization determines its in vivo effect. We hypothesize that cytoplasmic BRMS1 restricts melanoma progression while nuclear BRMS1 possibly promotes melanoma cell invasion.

Please see related article: http://www.biomedcentral.com/1741-7015/10/19