Metastasis suppressors genes in cancer

Bin1 is linked to metastatic potential and chemosensitivity in neuroblastoma

BACKGROUND

Neuroblastoma (NB) is the most common extracranial solid tumor in children. At the time of diagnosis, the tumor has metastasized in as many as 7 of 10 cases, and survival in high-risk patients remains poor. Accurate classification of high-risk patients is very important since this determines treatment plan, and although a consensus risk classification system has been established for NB, it contains few specific molecular markers that account for aggressive nature and metastatic potential of the tumor. Bin1 expression is reduced in breast, NB, and other cancer types and the reduction correlates with high-risk clinical features. Here we hypothesize that Bin1 has an inhibitory role in metastasis, and therefore decrease in its expression may be a marker of high-risk NB.

PROCEDURE

Initially, breast cancer and NB cell lines derived from metastasis were examined for Bin1 expression. Then, a stable Bin1-overexpressing NB cell line was created and evaluated for in vitro metastatic behaviors using anoikis, invasion, and migration assays, and chemoresponsiveness using MTT assay.

RESULTS

Reduced Bin1 was detected in all cancer cell lines examined, and forced Bin1 overexpression increased NB cell anoikis and enhanced the cell killing by doxorubicin. However, Bin1 overexpression did not significantly affect cell invasion, motility, or proliferation.

CONCLUSIONS

Bin1 appears to function as a metastasis suppressor and chemosensitizer in NB, and resistance to anoikis may be an important metastatic mechanism. Thus, Bin1 expression status could serve as a marker for metastatic potential and chemosensitivity thereby allowing for more accurate classifications of high-risk NB patients.

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

BACKGROUND/AIMS

To determine breast cancer metastasis suppressor 1 (BRMS1) expression in breast cancers and the efficacy of BRMS1 as a prognostic indicator, BRMS1 expression was assessed in two sets of breast cancer tissues.

METHODS

Epithelial cells from 36 frozen samples of breast cancers and corresponding normal breast were collected by laser capture microdissection and assessed for BRMS1 by quantitative RT-PCR and immunohistochemistry. BRMS1 was also evaluated by immunohistochemistry in a tissue microarray of 209 breast cancers and correlated with indicators of prognosis [estrogen receptor (ER), progesterone receptor (PR), ErbB2, p53, p27(Kip1), Bcl2 and Ki-67].

RESULTS

BRMS1 mRNA and protein were higher in 94 and 81%, respectively, of breast cancers than in corresponding normal epithelium. BRMS1 localization was predominantly nuclear, but 60-70% of cancers also exhibited cytoplasmic immunostaining. Breast cancers with lower nuclear than cytoplasmic BRMS1 (nuclear score - cytoplasmic score < or =0; 11% of cancers) had lower ER, lower PR and higher Ki-67 expression. There was also a trend toward poorer overall survival in this group of cancers, but this was only of borderline significance (p = 0.073). In Cox proportional hazards models, loss of nuclear BRMS1 was not a significant predictor of overall survival.

CONCLUSIONS

Loss of nuclear BRMS1 was associated with ER-negative cancers and a high rate of proliferation, but was not an independent indicator of prognosis.

Expression of the Breast Cancer Metastasis Suppressor 1 (BRMS1) maintains in vitro chemosensitivity of breast cancer cells

The Breast Cancer Metastasis Suppressor 1 (BRMS1) belongs to an expanding category of proteins called metastasis suppressors that demonstrate in vivo metastasis suppression while still allowing growth of the orthotopic tumor. Since BRMS1 decreases either the expression or function of multiple mediators implicated in resistance to chemotherapy (NF-kappaB, AKT, EGFR), we asked whether breast carcinoma cells expressing BRMS1 could be sensitized upon exposure to commonly used therapeutic agents that inhibit some of these same cellular mediators as BRMS1. In this report, we demonstrate that chemosensitivity of breast cancer cells is preserved in the presence of BRMS1. Further, BRMS1 does not change expression of AKT isoforms or PTEN, implicated in chemoresistance to common drug agents. Overall, our data with two different metastatic breast cancer cell lines indicates that BRMS1 expression status may not interfere with the response to commonly used chemotherapeutic agents in the management of solid tumors such as breast cancer. Since tumor protein expression analysis increasingly guides therapy decisions, our data may be of clinical benefit in disease management including profiling for BRMS1 expression before start of therapy.

Activation of Rho and Rho-associated kinase by GPR54 and KiSS1 metastasis suppressor gene product induces changes of cell morphology and contributes to apoptosis

The mechanism of action of the metastasis suppressor KiSS1 and its receptor GPR54 is still incompletely characterized. Although the loss of KiSS1 expression by tumor cells has been associated with a metastatic phenotype, the nature of the cellular target of the secreted kisspeptins is unknown. Although an autocrine model of action has been generally assumed, metastasis suppression by KiSS1 has also been shown in cells that do not express GPR54, suggesting a paracrine mechanism in which kisspeptins affect cells in the metastatic niche. Activation of GPR54 was shown to inhibit cell motility and invasion of tumor cells, induce the formation of stress fibers, and reduce the expression of matrix metalloproteinase 9. We showed previously that the activation of GPR54 by kisspeptin-10 suppressed CXCR4-mediated chemotaxis in response to stromal cell-derived factor 1/CXCL12 and abolished the phosphorylation of Akt by CXCR4. We also demonstrated that activation of GPR54 inhibited Akt phosphorylation after the activation of epidermal growth factor receptor and the insulin receptor and triggered apoptosis in epithelial and lymphoid cell lines through a mechanism involving extracellular signal-regulated kinase (ERK) mitogen-activated protein kinase. We show here that the activation of GPR54 induced immediate and profound changes of cell morphology, including cytoplasmic condensation and formation of unpolarized plasma membrane protrusions. These events were dependent on Rho and Rho-Associated Kinase (ROCK) activation. The activation of ROCK also contributed to GPR54-mediated apoptosis in 293 cells, and its effect was additive to and independent of ERK activation. These results suggest that RhoA and ROCK are additional key components of the antimetastatic effect of kisspeptins.

KiSS1 metastasis suppressor gene product induces suppression of tyrosine kinase receptor signaling to Akt, tumor necrosis factor family ligand expression, and apoptosis

The powerful metastasis suppressor function of KiSS1 gene products has been demonstrated in both clinical studies and experimental models, but its mechanism is still incompletely understood. Studies on the antimetastatic function of KiSS1 and GPR54 largely focused on the autocrine inhibition of cell motility, despite experimental evidence of an alternative post-migratory effect. We showed previously that the activation of its cognate receptor GPR54 by kisspeptin-10 suppressed the capacity of the prometastatic chemokine receptor CXCR4 to induce chemotaxis in response to stromal cell derived factor 1 and abolished the activation of Akt by CXCR4. We demonstrate here that activation of GPR54 can also abolish the activation of Akt by the tyrosine kinase receptors for epidermal growth factor and insulin. The signaling of GPR54 was sufficient to trigger apoptosis in epithelial and lymphoid cell lines. Surprisingly, this phenomenon depended largely on the activation of extracellular signal-regulated kinase (ERK) rather than the inhibition of Akt. Activation of GPR54 resulted in the ERK-dependent expression of tumor necrosis factor-alpha and FasL in a lymphoid cell line, the latter being the main trigger of apoptosis. These data provide novel mechanisms relevant to a potential autocrine metastasis suppression effect of KiSS1 on GPR54-positive tumor cells. More importantly, they also establish an experimental basis for a paracrine mode of action by which kisspeptins suppress the metastatic potential of tumor cells lacking expression of the receptor, as observed in several animal models of metastasis. The action on stromal cells significantly broadens the clinical relevance of this metastasis suppressor.

Learning therapeutic lessons from metastasis suppressor proteins

Metastasis suppressor proteins regulate multiple steps in the metastatic cascade, including cancer cell invasion, survival in the vascular and lymphatic circulation, and colonization of distant organ sites. Understanding the biology of metastasis suppressors provides valuable mechanistic insights that may translate to therapeutic opportunities. Several reports have explored novel strategies for restoring metastasis suppressor function, including gene transfer, induction of previously suppressed gene expression and exogenous administration of gene product. Pathways activated downstream of metastasis suppressor loss can also be targeted. Although none of these strategies are yet in routine clinical use, several are being tested preclinically and in clinical trials.

Metastasis suppressor 1 (MTSS1) demonstrates prognostic value and anti-metastatic properties in breast cancer

Metastasis suppressor 1 (MTSS1) may play an important role in cancer metastasis. Firstly, this study assessed MTSS1 expression levels within breast cancer patients to reveal any clinical relevance. Secondly, we aimed to clarify the cellular function of MTSS1 in breast cancer cells. MTSS1 expression levels were assessed in a cohort of breast cancer specimens (normal n=33; cancer n=127), through quantitative PCR analysis and immuno-histochemical techniques. The influence of MTSS1 was further examined via biological overexpression and knockdown within breast cancer cell lines. We report that patients with tumours expressing reduced levels of MTSS1 had a poorer prognosis (p=0.042). High levels of MTSS1 correlated with an increased patient overall survival (p=0.0108) and disease-free survival (p=0.012). Furthermore, overexpression of MTSS1 significantly suppressed (p<0.01) the invasive, migratory, growth and adherence properties of a human breast cancer cell line. In contrast, knockdown of MTSS1 dramatically enhanced these properties. We conclude that MTSS1 is a prognostic indicator of disease-free survival in breast cancer patients and demonstrates the ability to play a role in governing the metastatic nature of breast cancer cells.

Nuclear magnetic resonance and circular dichroism study of metastin (Kisspeptin-54) structure in solution

KISS1 was first discovered as a metastasis suppressor, but also plays crucial roles in the onset of puberty. The KISS1 gene encodes a secreted protein of 145 amino acids that exhibits no sequence similarity with any known proteins. KISS1 protein is proteolytically processed to generate a number of so-called kisspeptins (KP), the most well characterized is known as KP-54 or metastin. KP-54 is carboxy-terminally amidated and binds to and activates the KISS1 receptor (KISS1R). The current studies were undertaken in order to determine structure of KP-54 using nuclear magnetic resonance and circular dichroism. KP-54 is mostly disordered both in water and in trifluoroethanol/water mixed solvent, with no structural motifs. In sodium dodecyl sulfate micelles, KP-54 remains mostly disordered except for a small increase in helical propensity (from 3.7% in water to 9.9% in micelles). Despite this apparent lack of structure, KP-54 is biologically active. The intrinsic disorder of KP-54 may confer advantages in its ability to recognize and bind a wide range of target proteins.

A genome-wide shRNA screen identifies GAS1 as a novel melanoma metastasis suppressor gene

Metastasis suppressor genes inhibit one or more steps required for metastasis without affecting primary tumor formation. Due to the complexity of the metastatic process, the development of experimental approaches for identifying genes involved in metastasis prevention has been challenging. Here we describe a genome-wide RNAi screening strategy to identify candidate metastasis suppressor genes. Following expression in weakly metastatic B16-F0 mouse melanoma cells, shRNAs were selected based upon enhanced satellite colony formation in a three-dimensional cell culture system and confirmed in a mouse experimental metastasis assay. Using this approach we discovered 22 genes whose knockdown increased metastasis without affecting primary tumor growth. We focused on one of these genes, Gas1 (Growth arrest-specific 1), because we found that it was substantially down-regulated in highly metastatic B16-F10 melanoma cells, which contributed to the high metastatic potential of this mouse cell line. We further demonstrated that Gas1 has all the expected properties of a melanoma tumor suppressor including: suppression of metastasis in a spontaneous metastasis assay, promotion of apoptosis following dissemination of cells to secondary sites, and frequent down-regulation in human melanoma metastasis-derived cell lines and metastatic tumor samples. Thus, we developed a genome-wide shRNA screening strategy that enables the discovery of new metastasis suppressor genes.

Prognostic value of metastin expression in human pancreatic cancer

BACKGROUND

KiSS-1 was identified as a metastasis-suppressing gene in melanoma cells. The KiSS-1 gene product (metastin) was isolated from human placenta as the ligand of GPR54, a G-protein-coupled receptor. The role of metastin and GPR54 in tumor progression is not fully understood.

METHODS

We investigated the clinical significance of metastin and GPR54 expression in pancreatic cancer. We evaluated immunohistochemical expression of metastin and GPR54 in pancreatic ductal adenocarcinoma tissues obtained from 53 consecutive patients who underwent resection between July 2003 and May 2007 at Kyoto University Hospital. In 23 consecutive patients, the plasma metastin level was measured before surgery by enzyme immunoassay.

RESULTS

Strong immunohistochemical expression of metastin was detected in 13 tumors (24.5%), while strong expression of GPR54 was detected in 30 tumors (56.6%). Tumors that were negative for both metastin and GPR54 expression were significantly larger than tumors that were positive for either metastin or GPR54 (p = 0.047). Recurrence was less frequent in patients who had metastin-positive tumors compared with those who had metastin-negative tumors (38.5% versus 70.0%, p = 0.04). Strong expression of metastin and GPR54 was significantly correlated with longer survival (p = 0.02). Metastin expression by pancreatic cancer was an independent prognostic factor for longer survival (hazard ratio, 2.1; 95% confidence interval, 1.1-4.7; p = 0.03), and the patients with a high plasma metastin level (n = 6) did not die after surgical resection.

CONCLUSION

Strong expression of metastin and GPR54 by pancreatic cancer is associated with longer survival. Metastin expression is an independent prognostic factor for the survival of pancreatic cancer patients. The plasma metastin level could become a noninvasive prognostic factor for the assessment of pancreatic cancer.

Tetraspanins: push and pull in suppressing and promoting metastasis

Tumours progress through a cascade of events that enable the formation of metastases. Some of the components that are required for this fatal process are well established. Tetraspanins, however, have only recently received attention as both metastasis suppressors and metastasis promoters. This late appreciation is probably due to their capacity to associate with various molecules, which they recruit into special membrane microdomains, and their abundant presence in tumour-derived small vesicles that aid intercellular communication. It is reasonable to assume that differences in the membrane and vesicular web components that associate with individual tetraspanins account for their differing abilities to promote and suppress metastasis.

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

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

Adaptive history of single copy genes highly expressed in the term human placenta

The chorioallantoic placenta is a shared derived feature of "placental" mammals essential for the success of eutherian reproduction. Identifying the genes involved in the emergence of the placenta may provide clues for understanding the biology of this organ. Here we identify among 4960 single copy genes in mammals, 222 that show high expression levels in human placentas at term. Further, we present evidence that 94 of these 222 genes evolved adaptively during human evolutionary history since the time of the last common ancestor of eutherian mammals. Remarkably, the majority of positive selection occurred on the eutherian stem lineage suggesting that ancient adaptations have been retained in the human placenta. Of these positively selected genes, 28 have been shown to play a role in human pregnancy and placental biology, and at least 26 have important pregnancy-related phenotypes in mice. Adaptations in genes highly expressed in human placenta are attractive candidates for functional and clinical studies.

IFN-induced protein with tetratricopeptide repeats 2 inhibits migration activity and increases survival of oral squamous cell carcinoma

The function of the IFN-stimulated gene family protein, IFN-induced protein with tetratricopeptide repeats 2 (IFIT2), is poorly understood. Here, we report that IFIT2 colocalizes with cytokeratin 18 in oral squamous cell carcinoma (OSCC) cells. Treatment of OSCC cells with IFN-beta significantly increased the expression of IFIT2 and remarkably inhibited cell migration. To further explore the effect of IFIT2 on cell migration, IFIT2 expression was either silenced with a small interfering RNA or increased by ectopic expression. IFIT2 knockdown in OSCC cells led to a significantly higher level of migration in vitro (P < 0.05) compared with control cells; by contrast, IFIT2 overexpression led to a significantly lower level of migration in vitro (P < 0.05). Immunohistochemically, 71.4% of OSCC tissues had elevated IFIT2 protein levels compared with noncancerous matched tissues. Elevated IFIT2 protein expression was positively associated with tumor differentiation status and inversely associated with nodal stage in OSCC specimens (P < 0.05). Higher IFIT2 protein levels in tumor tissues were also associated with better patient survival (P < 0.01). Our present study shows an inverse correlation between IFIT2 expression and cell migration, suggesting that IFIT2 plays an important role in inhibiting this process and that its expression may be associated with better prognosis in patients with OSCC.

Diallyl trisulfide increases the effectiveness of TRAIL and inhibits prostate cancer growth in an orthotopic model: molecular mechanisms

Recent studies have shown that naturally occurring compounds can enhance the efficacy of chemotherapeutic drugs. The objectives of this study were to investigate the molecular mechanisms by which diallyl trisulfide (DATS) enhanced the therapeutic potential of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) in prostate cancer cells in vitro and on orthotopically transplanted PC-3 prostate carcinoma in nude mice. DATS inhibited cell viability and colony formation and induced apoptosis in PC-3 and LNCaP cells. DATS enhanced the apoptosis-inducing potential of TRAIL in PC-3 cells and sensitized TRAIL-resistant LNCaP cells. Dominant-negative FADD inhibited the synergistic interaction between DATS and TRAIL on apoptosis. DATS induced the expression of DR4, DR5, Bax, Bak, Bim, Noxa, and PUMA and inhibited expression of Mcl-1, Bcl-2, Bcl-X(L), survivin, XIAP, cIAP1, and cIAP2. Oral administration of DATS significantly inhibited growth of orthotopically implanted prostate carcinoma in BALB/c nude mice compared with the control group, without causing weight loss. Cotreatment of mice with DATS and TRAIL was more effective in inhibiting prostate tumor growth and inducing DR4 and DR5 expression, caspase-8 activity, and apoptosis than either agent alone. DATS inhibited angiogenesis (as measured by CD31-positive and factor VIII-positive blood vessels and hypoxia-inducible factor-1alpha, vascular endothelial growth factor, and interleukin-6 expression) and metastasis [matrix metalloproteinase (MMP)-2, MMP-7, MMP-9, and MT-1 MMP expression], which were correlated with inhibition in AKT and nuclear factor-kappaB activation. The combination of DATS and TRAIL was more effective in inhibiting markers of angiogenesis and metastasis than either agent alone. These data suggest that DATS can be combined with TRAIL for the prevention and/or treatment of prostate cancer.

DLC1 tumor suppressor gene inhibits migration and invasion of multiple myeloma cells through RhoA GTPase pathway

DLC1 (deleted in liver cancer 1), a tumor suppressor gene that encodes a RhoGTPase-activating protein, is recurrently downregulated or silenced in various solid tumors and hematological malignancies because of epigenetic modifications or genomic deletion. Here, we identified DLC1 promoter hypermethylation in 43 out of 44 multiple myeloma (MM) cell lines, which resulted in downregulation or silencing of DLC1 in 41 samples. High frequency of tumor-specific methylation and attenuation or silencing of DLC1 expression could serve as an independent diagnostic marker for MM. Combined treatment with demethylating and acetylating agents significantly elevated the expression of DLC1 and suppressed MM cell proliferation. Two cell lines exhibiting complete promoter methylation and the absence of DLC1 expression were transduced by an adenoviral vector containing DLC1 cDNA. In both cell lines, the reexpression of DLC1 inhibited myeloma cell invasion and migration, reduced RhoA activity and resulted in the reorganization of actin cytoskeleton. These results provide the first evidence for the antiproliferative effect of DLC1 in a hematological cancer and implicate RhoA pathway in suppression of MM migration and invasion. Given the myeloma cells sensitivity to the reactivation of DLC1 function, the potential for molecular targeted therapy of DLC1-mediated pathways as well as epigenetic therapies hold prospects.

Controlling cell surface dynamics and signaling: how CD82/KAI1 suppresses metastasis

The recent identification of metastasis suppressor genes, uniquely responsible for negatively controlling cancer metastasis, are providing inroads into the molecular machinery involved in metastasis. While the normal function of a few of these genes is known; the molecular events associated with their loss that promotes tumor metastasis is largely not understood. KAI1/CD82, whose loss is associated with a wide variety of metastatic cancers, belongs to the tetraspanin family. Despite intense scrutiny, many aspects of how CD82 specifically functions as a metastasis suppressor and its role in normal biology remain to be determined. This review will focus on the molecular events associated with CD82 loss, the potential impact on signaling pathways that regulate cellular processes associated with metastasis, and its relationship with other metastasis suppressor genes.