A shift from nuclear to cytoplasmic breast cancer metastasis suppressor 1 expression is associated with highly proliferative estrogen receptor-negative breast cancers

Molecular interaction of metastasis suppressor genes and tumor microenvironment in breast cancer

Breast cancer (BC) is a leading cause of cancer-related deaths in women worldwide where the process of metastasis is a major contributor to the mortality associated with this disease. Metastasis suppressor genes are a group of genes that play a crucial role in preventing or inhibiting the spread of cancer cells. They suppress the metastasis process by inhibiting colonization and by inducing dormancy. These genes function by regulating various cellular processes in the tumor microenvironment (TME), such as cell adhesion, invasion, migration, and angiogenesis. Dysregulation of metastasis suppressor genes can lead to the acquisition of an invasive and metastatic phenotype and lead to poor prognostic outcomes. The components of the TME generally play a necessary in the metastasis progression of tumor cells. This review has identified and elaborated on the role of a few metastatic suppressors associated with the TME that have been shown to inhibit metastasis in BC by different mechanisms, such as blocking certain cell signaling molecules involved in cancer cell migration, invasion, enhancing immune surveillance of cancer cells, and promoting the formation of a protective extracellular matrix (ECM). Understanding the interaction of metastatic suppressor genes and the components of TME has important implications for the development of novel therapeutic strategies to target the metastatic cascade. Targeting these genes or their downstream signaling pathways offers a promising approach to inhibiting the spread of cancer cells and improves patient outcomes.

Normalizing glucose levels reconfigures the mammary tumor immune and metabolic microenvironment and decreases metastatic seeding

Obesity and diabetes cumulatively create a distinct systemic metabolic pathophysiological syndrome that predisposes patients to several diseases including breast cancer. Moreover, diabetic and obese women with breast cancer show a significant increase in mortality compared to non-obese and/or non-diabetic women. We hypothesized that these metabolic conditions incite an aggressive tumor phenotype by way of impacting tumor cell-autonomous and tumor cell non-autonomous events. In this study, we established a type 2 diabetic mouse model of triple-negative mammary carcinoma and investigated the effect of a glucose lowering therapy, metformin, on the overall tumor characteristics and immune/metabolic microenvironment. Diabetic mice exhibited larger mammary tumors that had increased adiposity with high levels of O-GlcNAc protein post-translational modification. These tumors also presented with a distinct stromal profile characterized by altered collagen architecture, increased infiltration by tumor-permissive M2 macrophages, and early metastatic seeding compared to non-diabetic/lean mice. Metformin treatment of the diabetic/obese mice effectively normalized glucose levels, reconfigured the mammary tumor milieu, and decreased metastatic seeding. Our results highlight the impact of two metabolic complications of obesity and diabetes on tumor cell attributes and showcase metformin's ability to revert tumor cell and stromal changes induced by an obese and diabetic host environment.

Merlin deficiency alters the redox management program in breast cancer

The expression of Merlin tumor suppressor protein encoded by Neurofibromin 2 (NF2) gene is remarkably decreased in metastatic breast cancer tissues. In order to recapitulate clinical evidence, we generated a unique, conditional Nf2‐knockout (Nf2^−/−) mouse mammary tumor model. Merlin‐deficient breast tumor cells and Nf2^−/− mouse embryonic fibroblasts (MEFs) displayed a robustly invasive phenotype. Moreover, Nf2^−/− MEFs presented with notable alterations in redox management networks, implicating a role for Merlin in redox homeostasis. This programmatic alteration resonated with pathways that emerged from breast tumor cells engineered for Merlin deficiency. Further investigations revealed that NF2‐silenced cells supported reduced activity of the Nuclear factor, erythroid 2 like 2 antioxidant transcription factor, concomitant with elevated expression of NADPH oxidase enzymes. Importantly, mammary‐specific Nf2^−/− in an Mouse mammary tumor virus Neu + murine breast cancer model demonstrated accelerated mammary carcinogenesis in vivo. Tumor‐derived primary organoids and cell lines were characteristically invasive with evidence of a dysregulated cellular redox management system. As such, Merlin deficiency programmatically influences redox imbalance that orchestrates malignant attributes of mammary/breast cancer.

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.

DYSF expression in clear cell renal cell carcinoma: A retrospective study of 2 independent cohorts

OBJECTIVE

Renal cell carcinoma (RCC) is the most typical type of kidney cancer in adults. Hypercalcemia is a well known paraneoplastic syndrome associated with RCC and recent studies have reported that hypercalcemia is closely related to the poor prognosis of RCC patients. Clear cell RCC (ccRCC) is the most common and aggressive subtype of RCC. Although the histological classification of RCC is important for determination of appropriate treatment strategies, effective biomarkers for predicting prognosis of ccRCC have not yet been identified. Since calcium levels affect the prognosis of RCC patients, we evaluated whether the calcium-sensing genes on the plasma membrane, including those encoding calcium channels, CaSR, GPRC6a, and DYSF, could be used as biomarkers to predict the prognosis of ccRCC patients.

METHODS

Information from 537 patients from The Cancer Genome Atlas (TCGA; n = 446) and International Cancer Genome Consortium (ICGC; n = 91) was used in this study. Among these genes, DYSF was the only gene whose expression correlated with overall survival of both TGCA and ICGC patients.

RESULTS

Although DYSF gene expression was higher in ccRCC tissue than in normal kidney tissue, Kaplan-Meier curves showed that the survival rate of ccRCC patients with high DYSF expression was significantly higher than that of patients with low DYSF expression (TCGA, P < 0.0001; ICGC, P = 0.0011). We also validated the potential of DYSF as a prognostic biomarker for ccRCC by conducting a time-dependent area under the curve (AUC) analysis and 5-years receiver operating characteristic curve analysis. Finally, multivariate regression analysis revealed that the expression of DYSF is independent of other prognostic parameters (TCGA, P = 0.017; ICGC, P = 0.006).

CONCLUSIONS

These results suggested that DYSF may play a suppressive role in the progression of ccRCC and could act as a promising prognostic biomarker for predicting the survival of ccRCC patients.

Fascin expression is inversely correlated with breast cancer metastasis suppressor 1 and predicts a worse survival outcome in node-negative breast cancer patients

Background: Fascin is an actin-bundling protein that promotes cancer cell migration and invasion. By contrast, breast cancer metastasis suppressor 1 (BRMS1) inhibits cancer metastasis by targeting multiple steps of the metastatic cascade. We evaluated whether expression patterns of fascin and BRMS1 correlate with clinicopathological features and patient outcome. Methods: Immunohistochemistry for fascin and BRMS1 was performed using a tissue microarray constructed from 183 human breast cancer tissues. Fascin expression determined by the proportion of stained tumor cells (0: 0-5%, 1: 6-25%, 2: 26-50%, 3: 51-75%, or 4: >75%) and staining intensity (0: negative, 1: weak, 2: moderate, or 3: strong) were multiplied and defined as negative (0-3) or positive (4-12). BRMS1 expression was scored separately based on nuclear and cytoplasmic staining intensity (0: negative, 1: weak, 2: moderate, 3: strong). We obtained the BRMS1 H score by summing the nuclear and cytoplasmic scores and defined it as negative (0-2) or positive (3-6). Results: Expression of BRMS1 showed a significant inverse correlation with that of fascin. Fascin+ tumors were significantly associated with no lymph node metastasis, higher histological and higher nuclear grade, ER/PR/HER2 negativity, and triple-negative subtype (all ps < 0.05). These clinicopathological differences showed the same trend in a comparison of fascin-/BRMS1+ and fascin+/BRMS1- tumors. Negative or weak BRMS1 cytoplasmic expression was significantly associated with shorter disease-free survival (DFS; p = 0.043). Fascin positivity was significantly associated with shorter DFS (p = 0.005) and overall survival (p = 0.020) when analyses were confined to node-negative patients. Conclusions: This study confirms an inverse correlation between expression of fascin and expression of BRMS1 using a quite large cohort of human breast cancer tissues. Fascin alone or combined with BRMS1 was a worse prognostic marker, particularly in node-negative breast cancer patients.

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.

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.

CK2α' Drives Lung Cancer Metastasis by Targeting BRMS1 Nuclear Export and Degradation

Breast cancer metastasis suppressor 1 (BRMS1) is decreased in non-small cell lung cancer (NSCLC) and other solid tumors, and its loss correlates with increased metastases. We show that BRMS1 is posttranslationally regulated by TNF-induced casein kinase 2 catalytic subunit (CK2α') phosphorylation of nuclear BRMS1 on serine 30 (S30), resulting in 14-3-3ε-mediated nuclear exportation, increased BRMS1 cytosolic expression, and ubiquitin-proteasome-induced BRMS1 degradation. Using our in vivo orthotopic mouse model of lung cancer metastases, we found that mutation of S30 in BRMS1 or the use of the CK2-specific small-molecule inhibitor CX4945 abrogates CK2α'-induced cell migration and invasion and decreases NSCLC metastasis by 60-fold. Analysis of 160 human NSCLC specimens confirmed that tumor CK2α' and cytoplasmic BRMS1 expression levels are associated with increased tumor recurrence, metastatic foci, and reduced disease-free survival. Collectively, we identify a therapeutically exploitable posttranslational mechanism by which CK2α-mediated degradation of BRMS1 promotes metastases in lung cancer. Cancer Res; 76(9); 2675-86. ©2016 AACR.

ERα Mediates Estrogen-Induced Expression of the Breast Cancer Metastasis Suppressor Gene BRMS1

Recently, estrogen has been reported as putatively inhibiting cancer cell invasion and motility. This information is in direct contrast to the paradigm of estrogen as a tumor promoter. However, data suggests that the effects of estrogen are modulated by the receptor isoform with which it interacts. In order to gain a clearer understanding of the role of estrogen in potentially suppressing breast cancer metastasis, we investigated the regulation of estrogen and its receptor on the downstream target gene, breast cancer metastasis suppressor 1 (BRMS1) in MCF-7, SKBR3, TTU-1 and MDA-MB-231 breast cancer cells. Our results showed that estrogen increased the transcription and expression of BRMS1 in the ERα positive breast cancer cell line, MCF-7. Additionally, the ERα specific agonist PPT also induced the transcription and expression of BRMS1. However, the two remaining estrogen receptor (ER) subtype agonists had no effect on BRMS1 expression. In order to further examine the influence of ERα on BRMS1 expression, ERα expression was knocked down using siRNA (siERα). Western blot analysis showed that siERα reduced estrogen-induced and PPT-induced BRMS1 expression. In summary, this study demonstrates estrogen, via its α receptor, positively regulates the expression of BRMS1, providing new insight into a potential inhibitory effect of estrogen on metastasis suppression.

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.

In vitro biophysical, microspectroscopic and cytotoxic evaluation of metastatic and non-metastatic cancer cells in responses to anti-cancer drug

The Breast Cancer Metastasis Suppressor 1 (BRMS1) is a nucleo-cytoplasmic protein that suppresses cancer metastasis without affecting the growth of the primary tumor. Previous work has shown that it decreases the expression of protein mediators involved in chemoresistance. This study measured the biomechanical and biochemical changes in BRMS1 expression and the responses of BRMS1 to drug treatments on cancer cells in vitro. The results show that BRMS1 expression affects biomechanical properties by decreasing the Young's modulus and adhesion force of breast cancer cells after doxorubicin (DOX) exposure. Raman spectral bands corresponding to DNA/RNA, lipids and proteins were similar for all cells after DOX treatment. The expression of cytokines were similar for cancer cells after DOX exposure, although BRMS1 expression had different effects on the secretion of cytokines for breast cancer cells. The absence of significant changes on apoptosis, reactive oxygen species (ROS) expression and cell viability after BRMS1 expression shows that BRMS1 has little effect on cellular chemoresistance. Analyzing cancer protein expression is critical in evaluating therapeutics. Our study may provide evidence of the benefit of metastatic suppressor expression before chemotherapy.

Polymorphisms in the DNA repair gene ERCC2/XPD and breast cancer risk: a HapMap-based case-control study among Han Women in a Chinese less-developed area

AIMS

Genetic variations in DNA repair genes may impact repair functions, DNA damage, and breast cancer risk. This study is aimed to assess the associations of genetic polymorphisms in excision repair cross-complementing group 2 (ERCC2) with the risk of developing breast cancer.

MATERIALS AND METHODS

In total, 101 histopathologically confirmed breast cancer cases and 101 age/region-matched healthy controls were genotyped for rs 3916840, rs 1799793, and rs 238416 in ERCC2 by polymerase chain reaction-restriction fragment length polymorphism.

RESULTS

The rs 238416 heterozygous GA genotype combined with the rs 238416 genotypes (GA+AA) showed a significant association with breast cancer susceptibility (corrected p<0.01, odds ratio [OR]=0.29, 95% confidence interval [CI]=0.15-0.54; corrected p<0.01, OR=0.31, 95% CI=0.17-0.56, respectively). The rs 238416 GA genotype carriers had a decreased risk of breast cancer. However, we observed no significant association between the rs 3916840 and rs 1799793 polymorphisms in ERCC2 and breast cancer risk. Moreover, haplotype analysis showed that the ACG haplotype was associated with a significantly decreased risk of breast cancer, whereas the GCG haplotype was associated with a significantly increased risk of breast cancer (corrected p=0.004 and p=0.002, respectively). Multifactor dimensionality reduction analysis demonstrated that the interactions between rs 3916840 and rs 238416 were significantly synergistic.

CONCLUSION

To the best of our knowledge, this study is the first to demonstrate that the rs 238416 heterozygous genotype likely has a higher DNA repair capacity and, thus, can be protective against breast cancer in Chinese Han women.

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.

Metastasis suppressor genes

Metastasis is a major cause of cancer mortality. Metastasis is a complex process that requires the regulation of both metastasis-promoting and metastasis suppressor genes. The discovery of metastasis suppressor genes contributes significantly to our understanding of metastasis mechanisms and provides prognostic markers and therapeutic targets in clinical cancer management. In this review, we summarize the methods that have been used to identify metastasis suppressors and the potential clinical impact of these genes.

Genomics screens for metastasis genes

Metastasis is responsible for most cancer mortality. The process of metastasis is complex, requiring the coordinated expression and fine regulation of many genes in multiple pathways in both the tumor and host tissues. Identification and characterization of the genetic programs that regulate metastasis is critical to understanding the metastatic process and discovering molecular targets for the prevention and treatment of metastasis. Genomic approaches and functional genomic analyses can systemically discover metastasis genes. In this review, we summarize the genetic tools and methods that have been used to identify and characterize the genes that play critical roles in 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.

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.

BRMS151-98 and BRMS151-84 are crystal oligomeric coiled coils with different oligomerization states, which behave as disordered protein fragments in solution

The breast cancer metastasis suppressor 1 (BRMS1) gene suppresses metastasis without affecting the primary tumor growth. Cellular localization of BRMS1 appears to be important for exerting its effects on metastasis inhibition. We recently described a nucleo-cytoplasmic shuttling for BRMS1 and identified a nuclear export signal within the N-terminal coiled coil. The structure of these regions shows an antiparallel coiled coil capable of oligomerizing, which compromises the accessibility to the nuclear export signal consensus residues. We have studied the structural and biophysical features of this region to further understand the contribution of the N-terminal coiled coil to the biological function of BRMS1. We have observed that residues 85 to 98 might be important in defining the oligomerization state of the BRMS1 N-terminal coiled coil. The fragments are mainly disordered in solution, with evidence of residual structure. In addition, we report the presence of a conformational dynamic equilibrium (oligomeric folded species ↔ oligomeric unfolded) in solution in the BRMS1 N-terminal coiled coil that might facilitate the nuclear export of BRMS1 to the cytoplasm.

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.

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.

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

Ubiquitous Brms1 expression is critical for mammary carcinoma metastasis suppression via promotion of apoptosis

Morbidity and mortality of breast cancer patients are drastically increased when primary tumor cells are able to spread to distant sites and proliferate to become secondary lesions. Effective treatment of metastatic disease has been limited; therefore, an increased molecular understanding to identify biomarkers and therapeutic targets is needed. Breast cancer metastasis suppressor 1 (BRMS1) suppresses development of pulmonary metastases when expressed in a variety of cancer types, including metastatic mammary carcinoma. Little is known of Brms1 function throughout the initiation and progression of mammary carcinoma. The goal of this study was to investigate mechanisms of Brms1-mediated metastasis suppression in transgenic mice that express Brms1 using polyoma middle T oncogene-induced models. Brms1 expression did not significantly alter growth of the primary tumors. When expressed ubiquitously using a β-actin promoter, Brms1 suppressed pulmonary metastasis and promoted apoptosis of tumor cells located in the lungs but not in the mammary glands. Surprisingly, selective expression of Brms1 in the mammary gland using the MMTV promoter did not significantly block metastasis nor did it promote apoptosis in the mammary glands or lung, despite MMTV-induced expression within the lungs. These results strongly suggest that cell type-specific over-expression of Brms1 is important for Brms1-mediated metastasis suppression.

Fascin is a key regulator of breast cancer invasion that acts via the modification of metastasis-associated molecules

The actin-bundling protein, fascin, is a member of the cytoskeletal protein family that has restricted expression in specialized normal cells. However, many studies have reported the induction of this protein in various transformed cells including breast cancer cells. While the role of fascin in the regulation of breast cancer cell migration has been previously shown, the underlying molecular mechanism remained poorly defined. We have used variety of immunological and functional assays to study whether fascin regulates breast cancer metastasis-associated molecules. In this report we found a direct relationship between fascin expression in breast cancer patients and; metastasis and shorter disease-free survival. Most importantly, in vitro interference with fascin expression by loss or gain of function demonstrates a central role for this protein in regulating the cell morphology, migration and invasion potential. Our results show that fascin regulation of invasion is mediated via modulating several metastasis-associated genes. We show for the first time that fascin down-regulates the expression and nuclear translocation of a key metastasis suppressor protein known as breast cancer metastasis suppressor-1 (BRMS1). In addition, fascin up-regulates NF-kappa B activity, which is essential for metastasis. Importantly, fascin up-regulates other proteins that are known to be critical for the execution of metastasis such as urokinase-type plasminogen activator (uPA) and the matrix metalloproteases (MMP)-2 and MMP-9. This study demonstrates that fascin expression in breast cancer cells establishes a gene expression profile consistent with metastatic tumors and offers a potential therapeutic intervention in metastatic breast cancer treatment through fascin targeting.

Recent advances in breast cancer metastasis suppressor 1

Metastasis is a complex process divided into a number of steps including detachment of tumor cells from the primary tumor, invasion, migration, intravasation, survival in the vasculature, extravasation, and colonization of the secondary site. Proteins that block metastasis without inhibiting primary tumor formation are known as metastasis suppressors; examples are NM23, Maspin, KAI1, KISS1, and MKK4. Breast cancer metastasis suppressor 1 (BRMS1) was identified as a suppressor of breast cancer metastasis in the late 1990s. In vitro and in vivo studies have confirmed that BRMS1 is a potent metastasis suppressor not limited to breast cancer. However, conflicting clinical observations regarding its role as a metastasis suppressor and its validity as a diagnostic biomarker warrant more in-depth clinical study. In this review, the authors provide an overview of its biology, function, action mechanism and pathological significance.

Unraveling the enigmatic complexities of BRMS1-mediated metastasis suppression

Expression of BRMS1 causes dramatic suppression of metastasis in multiple in vivo model systems. As we gain further insight into the biochemical mechanisms of BRMS1, we appreciate the importance of both molecular and cellular context for functional metastasis suppression. BRMS1 associates with large chromatin remodeling complexes including SIN3:HDAC which are powerful epigenetic regulators of gene expression. Additionally, BRMS1 inhibits the activity of NFκB, a well-known transcription factor that plays significant roles in tumor progression. Moreover, BRMS1 coordinately regulates the expression of metastasis-associated microRNA known as metastamir. How these biochemical mechanisms and biological pathways are linked, either directly or indirectly, and the influence of molecular and cellular context, are critical considerations for the discovery of novel therapeutic targets for the most deadly aspect of tumor progression-metastasis.

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.

Metastasis suppressor genes at the interface between the environment and tumor cell growth

The molecular mechanisms and genetic programs required for cancer metastasis are sometimes overlapping, but components are clearly distinct from those promoting growth of a primary tumor. Every sequential, rate-limiting step in the sequence of events leading to metastasis requires coordinated expression of multiple genes, necessary signaling events, and favorable environmental conditions or the ability to escape negative selection pressures. Metastasis suppressors are molecules that inhibit the process of metastasis without preventing growth of the primary tumor. The cellular processes regulated by metastasis suppressors are diverse and function at every step in the metastatic cascade. As we gain knowledge into the molecular mechanisms of metastasis suppressors and cofactors with which they interact, we learn more about the process, including appreciation that some are potential targets for therapy of metastasis, the most lethal aspect of cancer. Until now, metastasis suppressors have been described largely by their function. With greater appreciation of their biochemical mechanisms of action, the importance of context is increasingly recognized especially since tumor cells exist in myriad microenvironments. In this chapter, we assemble the evidence that selected molecules are indeed suppressors of metastasis, collate the data defining the biochemical mechanisms of action, and glean insights regarding how metastasis suppressors regulate tumor cell communication to-from microenvironments.

C10ORF97 is a novel tumor-suppressor gene of non-small-cell lung cancer and a functional variant of this gene increases the risk of non-small-cell lung cancer

In an earlier study we showed that C10ORF97 (chromosome-10, open reading frame-97) was expressed in almost all of the tissues and cell lines tested, and that it inhibited the growth of seven tumor cell lines, including two lung carcinoma cell lines (A549 and PG). Here, we show that C10ORF97 is downregulated in non-small-cell lung cancer (NSCLC) tissue compared with normal lung tissue. Overexpression of C10ORF97 significantly suppressed human lung carcinoma A549 cell growth (proliferation and anchorage-independent growth in soft agar) and motility (migration and adhesion). This tumor-suppressive function of C10ORF97 was also verified in vivo. We further found that C10ORF97 caused G(1) arrest of A549 cells and modulated the expression level of several cell-cycle regulators (such as CDK2, cyclin-E and p27). These effects of C10ORF97 were mediated by physical association between C10ORF97 and Jun-activating domain-binding protein-1 (JAB1), and blocking of JAB1-mediated translocation of p27 from the nucleus to the cytoplasm. Together, these results indicated that C10ORF97 functions as a novel tumor suppressor by modulating several key G(1)/S-regulatory proteins by interacting with JAB1. These findings led us to hypothesize that a single-nucleotide polymorphism (SNP) in the C10ORF97 gene that affects its expression might be associated with susceptibility to NSCLC. SNP216 C>T (rs2297882) in the C10ORF97 Kozak sequence was identified, and allele T of SNP216 suppressed C10ORF97 expression in vitro and in vivo. Furthermore, the TT genotype of SNP216 was associated with an increased risk of NSCLC (adjusted odds ratio=1.73 (95% confidence interval: 1.33-2.25), P=4.6 × 10(-5)). These data indicated that C10ORF97 is a tumor suppressor of NSCLC progression and C10ORF97-SNP216 may serve as a predictor of NSCLC.

Laser capture microdissection (LCM) and whole genome amplification (WGA) of DNA from normal breast tissue --- optimization for genome wide array analyses

Background

Laser capture microdissection (LCM) can be applied to tissues where cells of interest are distinguishable from surrounding cell populations. Here, we have optimized LCM for fresh frozen normal breast tissue where large amounts of fat can cause problems during microdissection. Since the amount of DNA needed for genome wide analyses, such as single nucleotide polymorphism (SNP) arrays, is often greater than what can be obtained from the dissected tissue, we have compared three different whole genome amplification (WGA) kits for amplification of DNA from LCM material. In addition, the genome wide profiling methods commonly used today require extremely high DNA quality compared to PCR based techniques and DNA quality is thus critical for successful downstream analyses.

Findings

We found that by using FrameSlides without glass backing for LCM and treating the slides with acetone after staining, the problems caused by excessive fat could be significantly decreased. The amount of DNA obtained after extraction from LCM tissue was not sufficient for direct SNP array analysis in our material. However, the two WGA kits based on Phi29 polymerase technology (Repli-g^® (Qiagen) and GenomiPhi (GE Healthcare)) gave relatively long amplification products, and amplified DNA from Repli-g^® gave call rates in the subsequent SNP analysis close to those from non-amplified DNA. Furthermore, the quality of the input DNA for WGA was found to be essential for successful SNP array results and initial DNA fragmentation problems could be reduced by switching from a regular halogen lamp to a VIS-LED lamp during LCM.

Conclusions

LCM must be optimized to work satisfactorily in difficult tissues. We describe a work flow for fresh frozen normal breast tissue where fat is inclined to cause problems if sample treatment is not adapted to this tissue. We also show that the Phi29-based Repli-g^® WGA kit (Qiagen) is a feasible approach to amplify DNA of high quality prior to genome wide analyses such as SNP profiling.

Polyomavirus enhancer activator 3 protein promotes breast cancer metastatic progression through Snail-induced epithelial-mesenchymal transition

Polyomavirus enhancer activator 3 protein (Pea3), also known as ETV4, is a member of the Ets-transcription factor family, which promotes metastatic progression in various types of solid cancer. Pea3-driven epithelial-mesenchymal transition (EMT) has been described in lung and ovarian cancers. The mechanisms of Pea3-induced EMT, however, are largely unknown. Here we show that Pea3 overexpression promotes EMT in human breast epithelial cells through transactivation of Snail (SNAI1), an activator of EMT. Pea3 binds to the human Snail promoter through the two proximal Pea3 binding sites and enhances Snail expression. In addition, knockdown of Pea3 in invasive breast cancer cells results in down-regulation of Snail, partial reversal of EMT, and reduced invasiveness in vitro. Moreover, knockdown of Snail partially rescues the phenotype induced by Pea3 overexpression, suggesting that Snail is one of the mediators bridging Pea3 and EMT, and thereby metastatic progression of the cancer cells. In four breast cancer patient cohorts whose microarray and survival data were obtained from the Gene Expression Omnibus database, Pea3 and Snail expression are significantly correlated with each other and with overall survival of breast cancer patients. We further demonstrate that nuclear localization of Pea3 is associated with Snail expression in breast cancer cell lines and is an independent predictor of overall survival in a Chinese breast cancer patient cohort. In conclusion, our results suggest that Pea3 may be an important prognostic marker and a therapeutic target for metastatic progression of human breast cancer.

BRMS1 transcriptional repression correlates with CpG island methylation and advanced pathological stage in non-small cell lung cancer

Breast cancer metastasis suppressor gene-1 (BRMS1) mRNA and protein expression are significantly decreased in non-small cell lung cancer (NSCLC) and this is a poor prognostic indicator. Given that the BRMS1 promoter region contains a promoter-associated CpG island (CGI) that encompasses the transcriptional start site, we hypothesized that decreased BRMS1 mRNA and protein levels in NSCLC was secondary to increased BRMS1 promoter methylation. Methylation-specific PCR (MSP) of the two known CGIs (-3477 to - 2214 and - 531 to + 608) in the BRMS1 genome was performed in NSCLC cells. This demonstrated a robust increase in methylation of the promoter-associated CGI (-531 to + 608) but not of the upstream CGI (-3477 to - 2214). To experimentally verify that methylation contributes to BRMS1 transcriptional repression, we cloned the BRMS1 promoter region, including the promoter-associated CGI, into a luciferase reporter gene and found that BRMS1 promoter activity was dramatically inhibited under methylated conditions. We then assessed the BRMS1 methylation profile with MSP and bisulphite-sequencing PCR in human NSCLC adenocarcinoma (n = 20) and squamous cell carcinoma (n = 20) relative to adjacent non-cancerous bronchial epithelium. There was a significant increase in BRMS1 promoter methylation in all NSCLC specimens relative to non-cancerous tissues, with the most dramatic difference in squamous cell cancer histology. Subsequent immunostaining demonstrated that nuclear BRMS1 expression is reduced in lung cancer specimens compared to normal bronchial epithelium. The association between BRMS1 promoter methylation and specific clinical and histopathological variables was examined using a general linear model. Pathological tumour stage was associated with increased BRMS1 methylation in squamous cell cancers. These observations demonstrate that methylation of the promoter-associated CGI in BRMS1 results in its transcriptional repression, and highlight the potential clinical relevance of this methylation event with respect to NSCLC tumour histology and pathological stage.