Metastasis Suppressor 1 Research Articles

SNHG15 Mediates MTSS1 Gene Expression via Interacting with the Gene Promoter and Regulating Transcription Pausing.

Metastasis suppressor 1 (MTSS1) has been reported to play important roles in suppressing cancer progression. In this study, we investigated the underlying mechanism that regulates MTSS1 expression. We showed that in breast cancer cells, lncRNA-SNHG15-induced cell invasion and proliferation was accompanied with the decreased expression of MTSS1 mRNA. Further study revealed that SNHG15 mediated MTSS1 repression through blocking its promoter activity. Mechanistically, SNHG15 complexes with DDX5 and RTF1 and interacts with the core promoter of the MTSS1 gene to interfere with RNA-Pol-II-directed transcriptional initiation. Association with DDX5 stabilizes SNHG15 while binding to RTF1 allows SNHG15 to carry RTF1 to the core promoter, where RTF1 forms a complex with PNA pl II to enhance transcriptional pausing. Our findings revealed a molecular mechanism by which SNHG15 serves as a regulator to suppresses MTSS1 transcription via interaction with the gene core promoter.

MTSS1 is downregulated in nasopharyngeal carcinoma (NPC) which disrupts adherens junctions leading to enhanced cell migration and invasion.

Loss of cell-cell adhesions is the indispensable first step for cancer cells to depart from the primary tumor mass to metastasize. Metastasis suppressor 1 (MTSS1) is frequently lost in metastatic tissues, correlating to advanced tumor stages and poor prognosis across a variety of cancers. Here we explore the anti-metastatic mechanisms of MTSS1, which have not been well understood. We found that MTSS1 is downregulated in NPC tissues. Lower levels of MTSS1 expression correlate to worse prognosis. We show that MTSS1 suppresses NPC cell migration and invasion in vitro through cytoskeletal remodeling at cell-cell borders and assembly of E-cadherin/β-catenin/F-actin in adherens junctions. The I-BAR domain of MTSS1 was both necessary and sufficient to restore this formation of E-cadherin/β-catenin/F-actin-mediated cell adherens junctions.

Metastasis suppressor 1 interacts with protein tyrosine phosphatase receptor-δ to regulate adipogenesis.

Adipogenesis is a finely controlled process and its dysfunction may contribute to metabolic disorders such as obesity. Metastasis suppressor 1 (MTSS1) is a player in tumorigenesis and metastasis of various types of cancers. To date, it is not known whether and how MTSS1 plays a role in adipocyte differentiation. In the current study, we found that MTSS1 was upregulated during adipogenic differentiation of established mesenchymal cell lines and primary cultured bone marrow stromal cells. Gain-of-function and loss-of-function experiments uncovered that MTSS1 facilitated adipocyte differentiation from mesenchymal progenitor cells. Mechanistic explorations revealed that MTSS1 bound and interacted with FYN, a member of Src family of tyrosine kinases (SFKs), and protein tyrosine phosphatase receptor-δ (PTPRD). We demonstrated that PTPRD was capable of inducing the differentiation of adipocytes. Overexpression of PTPRD attenuated the impaired adipogenesis induced by the siRNA targeting MTSS1. Both MTSS1 and PTPRD activated SFKs by suppressing the phosphorylation of SFKs at Tyr530 and inducing the phosphorylation of FYN at Tyr419. Further investigation showed that MTSS1 and PTPRD were able to activate FYN. Collectively, our study has for the first time unraveled that MTSS1 plays a role in adipocyte differentiation in vitro through interacting with PTPRD and thereby activating SFKs such as FYN tyrosine kinase.

Actin-rich lamellipodia-like protrusions contribute to the integrity of epithelial cell–cell junctions

Metastasis-suppressor 1 (MTSS1) is a membrane-interacting scaffolding protein that regulates the integrity of epithelial cell-cell junctions and functions as a tumor suppressor in a wide range of carcinomas. MTSS1 binds phosphoinositide-rich membranes through its I-BAR domain and is capable of sensing and generating negative membrane curvature invitro. However, the mechanisms by which MTSS1 localizes to intercellular junctions in epithelial cells and contributes to their integrity and maintenance have remained elusive. By carrying out EM and live-cell imaging on cultured Madin-Darby canine kidney cell monolayers, we provide evidence that adherens junctions of epithelial cells harbor lamellipodia-like, dynamic actin-driven membrane folds, which exhibit high negative membrane curvature at their distal edges. BioID proteomics and imaging experiments demonstrated that MTSS1 associates with an Arp2/3 complex activator, the WAVE-2 complex, in dynamic actin-rich protrusions at cell-cell junctions. Inhibition of Arp2/3 or WAVE-2 suppressed actin filament assembly at adherens junctions, decreased the dynamics of junctional membrane protrusions, and led to defects in epithelial integrity. Together, these results support a model in which membrane-associated MTSS1, together with the WAVE-2 and Arp2/3 complexes, promotes the formation of dynamic lamellipodia-like actin protrusions that contribute to the integrity of cell-cell junctions in epithelial monolayers.

Alternagin-C, an alpha2beta1 integrin ligand, attenuates collagen-based adhesion, stimulating the metastasis suppressor 1 expression in triple-negative breast tumor cells

Triple-negative breast cancer has an aggressive clinical course and its treatment has been challenging due to high metastatic risk. Molecular targets have been sought to provide better strategies for this type of cancer. Integrins are cell adhesion receptors involved in tumor progression and α2β1 integrin, a collagen receptor, has a key role in breast metastasis. Disintegrins, a family of proteins from snake venoms, selectively block the function of integrin receptors. Alternagin-C (ALT-C), a disintegrin-like protein purified from Bothrops alternatus venom, binds to α2β1 integrin, attenuating inflammation and angiogenesis, and decreasing metalloprotease levels in the tumor microenvironment, which suggests anti-metastatic effects. However, its mechanisms of action in metastatic tumor cells have not been fully explored. Here, we investigated ALT-C effects in a triple-negative breast cancer cell line (MDA-MB-231) to elucidate how α2β1 integrin affects cellular adhesion, migration and gene expression related to metastasis. We observed that ALT-C attenuated cell adhesion of MDA-MB-231 cells to collagen I. α2 integrin subunit silencing in MDA-MB-231 cells did not inhibit cell adhesion and migration to collagen I, indicating that other integrins play a crucial role in cell motility for this cell line. ALT-C also stimulated the metastasis suppressor 1 (MTSS1) expression and decreased metalloproteases MMP9 and MMP2. Therefore, we suggest that ALT-C contributes to impair metastasis, preventing extracellular matrix degradation and tumor attachment to collagen I, increasing MTSS1. This study is the first to elucidate the anti-metastatic mechanism involving a disintegrin-like protein from snake venom targeting α2β1 integrin and stimulating a metastasis suppressor.

Metastasis suppressor 1 controls osteoblast differentiation and bone homeostasis through regulating Src-Wnt/β-catenin signaling.

Metastasis suppressor 1 (MTSS1) plays an inhibitory role in tumorigenesis and metastasis of a variety of cancers. To date, the function of MTSS1 in the differentiation of marrow stromal progenitor cells remains to be explored. In the current study, we investigated whether and how MTSS1 has a role in osteoblast differentiation and bone homeostasis. Our data showed that MTSS1 mRNA was upregulated during osteoblast differentiation and downregulated in the osteoblastic lineage cells of ovariectomized and aged mice. Functional studies revealed that MTSS1 promoted the osteogenic differentiation from marrow stromal progenitor cells. Mechanistic explorations uncovered that the inactivation of Src and afterward activation of canonical Wnt signaling were involved in osteoblast differentiation induced by MTSS1. The enhanced osteogenic differentiation induced by MTSS1 overexpression was attenuated when Src was simultaneously overexpressed, and conversely, the inhibition of osteogenic differentiation by MTSS1 siRNA was rescued when the Src inhibitor was supplemented to the culture. Finally, the in vivo transfection of MTSS1 siRNA to the marrow of mice significantly reduced the trabecular bone mass, along with the reduction of trabecular osteoblasts, the accumulation of marrow adipocytes, and the increase of phospho-Src-positive cells on the trabeculae. No change in the number of osteoclasts was observed. This study has unraveled that MTSS1 contributes to osteoblast differentiation and bone homeostasis through regulating Src-Wnt/β-catenin signaling. It also suggests the potential of MTSS1 as a new target for the treatment of osteoporosis.

Metastasis suppressor 1 interacts with α-actinin 4 to affect its localization and regulate formation of membrane ruffling.

Membrane ruffling plays an important role in the directed cell migration and escape of tumor cells from the monolayer. Metastasis suppressor 1 (MTSS1), also known as missing in metastasis, has been implicated in cell morphology, motility, metastasis, and development. Here, the dynamic interaction proteins associated with MTSS1 and involved in membrane ruffling were determined by cross-linking and mass spectrometry analysis. We identified α-actinin 4 (ACTN4) as an interacting protein and confirmed a direct interaction between MTSS1 and ACTN4. Moreover, co-expression of MTSS1 in fibroblasts recruited cytoplasmic ACTN4 to the cell periphery, at which point ruffling became thick and rigid. In MCF-7 cells, MTSS1 knockdown did not show an obvious effect on the cell shape or the distribution of endogenous ACTN4; however, ACTN4 overexpression transformed cell morphology from an epidermal- to a fibroblast-like shape, and further MTSS1 depletion significantly increased the ratio of fibroblast cells exhibiting prominent ruffling. Furthermore, biochemical data suggested that MTSS1 cross-linking with ACTN4 induced the formation of actin fiber bundles into more organized structures in vitro. These data indicated that MTSS1 might recruit cytoplasmic ACTN4 to the cell periphery and regulate cytoskeleton dynamics to restrict its performance in membrane ruffling.

Circ_002059 suppresses cell proliferation and migration of gastric cancer via miR-182/MTSS1 axis.

Circular RNAs (circRNAs) play either oncogenic or tumor suppressive roles in gastric cancer (GC). A previous study demonstrated that circ_002059, a typical circRNA, was downregulated in GC tissues. However, the role and mechanism of circ_002059 in GC development are still unknown. In this study, the levels of circ_002059, miR-182, and metastasis suppressor-1 (MTSS1) were examined by real-time quantitative polymerase chain reaction and western blot analysis. Cell proliferation and migration were evaluated by MTT assay and Transwell migration assay, respectively. The interactions between miR-182 and circ_002059 or MTSS1 were analyzed by dual-luciferase reporter assay. A GC xenograft model was established to validate the role of circ_002059 in GC progression in vivo. Overexpression of circ_002059 significantly inhibited, whereas knockdown of circ_002059 notably facilitated, cell proliferation and migration in GC cells. MTSS1 was found to be a direct target of miR-182 and circ_002059 upregulated MTSS1 expression by competitively sponging miR-182. Transfection with miR-182 mimic and MTSS1 silencing abated the inhibitory effect of circ_002059 on GC progression. Circ_002059 inhibited GC cell xenograft tumor growth by regulating miR-182 and MTSS1 expression. Collectively, Circ_002059 inhibited GC cell proliferation and migration in vitro and xenograft tumor growth in mice, by regulating the miR-182/MTSS1 axis.

MTSS1 inhibits colorectal cancer metastasis byregulating the CXCR4/CXCL12 signaling axis.

The liver is the most common site of metastasis for colorectal cancer (CRC). Metastasis suppressor 1 (MTSS1), a potential tumor suppressor gene associated with tumor metastasis, has been reported to play an important role in cancer development. The present study aimed to investigate the effects and underlying mechanisms of MTSS1 on the biological behavior of CRC cells both in vitro and in vivo. A CRC mouse model with a high liver metastatic potential was established by injecting mice with SW1116 cells, and the association between MTSS1 expression levels and the metastatic potential of forming liver metastasis lesions was subsequently analyzed. MTSS1 gain- and loss-of-function experiments were performed by transfecting the CRC cell lines, SW1116 and DLD-1, with Plvx-IRES-ZsGreen1-MTSS1 plasmid and short hairpin RNA, respectively. Cell proliferation, migration, invasion and cell cycle distribution were analyzed by MTT, Transwell and flow cytometric assays, respectively. To further determine the underlying mechanisms of MTSS1 in CRC, the expression levels of cell surface chemokine C-X-C receptor 4 (CXCR4) and its downstream signaling factors, Rac and cell division cycle 42 (CDC42), were analyzed with or without C-X-C motif chemokine ligand 12 (CXCL12) stimulation. The results revealed that as the CRC metastatic potential increased, the expression levels of MTSS1 decreased. The overexpression of MTSS1 exerted an inhibitory effect on cell proliferation, migration and invasion, while the knockdown of MTSS1 exerted the opposite effects in vitro. Flow cytometric analysis and western blot analysis demonstrated that MTSS1 negatively regulated the expression levels of cell surface CXCR4 and its downstream signaling pathway activation. On the whole, the results of the present study indicate that MTSS1 may play an important negative role in CRC metastasis and the underlying mechanisms may involve the downregulation of the CXCR4/CXCL12 signaling axis.

MiR-28-5p targets MTSS1 to regulate cell proliferation and apoptosis in esophageal cancer.

Esophageal cancer (EC) is one of the most common aggressive malignant diseases worldwide. miR-28-5p plays important regulatory roles in many cancers including human EC. However, the molecular mechanism and potential role of miR-28-5p in EC remain uncertain. In this study, qRT-PCR and western blot analysis revealed that miR-28-5p expression was up-regulated and metastasis suppressor-1 (MTSS1) was down-regulated in EC tissues relative to matched para-cancer tissues. Cell counting kit-8 (CCK-8) assay demonstrated that miR-28-5p mimics increased cell viability, and miR-28-5p inhibitor decreased it. Flow cytometry (FCM) assay indicated that miR-28-5p mimics promoted cell cycle entry, while miR-28-5p inhibitor reduced it and induced cell apoptosis. Moreover, miR-28-5p mimics up-regulated the expressions of cyclin A, cyclin dependent kinase 2 (CDK2), cyclin D1, and cyclin E but down-regulated the expressions of cleaved caspase-3 and cleaved caspase-9, which was abolished by miR-28-5p inhibitor. Furthermore, luciferase reporter assay verified that miR-28-5p directly targeted MTSS1 3'UTR and down-regulated its expression. MTSS1 overexpression in TE-1 cells inhibited cell proliferation and promoted apoptosis induced by miR-28-5p mimics, whereas silencing of MTSS1 reversed cell progression induced by miR-28-5p inhibitor. We also demonstrated that miR-28-5p could promote esophageal tumor formation in vivo. Hematoxylin-eosin staining, immunohistochemistry, and TUNEL assays confirmed that miR-28-5p antagomir inhibited cell growth and accelerated apoptosis. Our results suggest that miR-28-5p may induce cell proliferation and suppress apoptosis to promote EC tumor formation via decreasing MTSS1 expression. Thus, miR-28-5p may be a potential target for human EC therapy.

LncRNA Mtss1 promotes inflammatory responses and secondary brain injury after intracerebral hemorrhage by targeting miR-709 in mice

Secondary brain injuries following intracerebral hemorrhage (ICH) are mediated by inflammatory pathway activation. The present study aimed to characterize long noncoding RNAs (lncRNAs) that are differentially expressed in cerebral tissues during ICH pathogenesis and to investigate their pathogenic functions. An ICH mouse model established by collagenase injection was used to obtain differentially expressed lncRNAs for deep sequencing. A cellular inflammation model was established by treating mouse microglia with lipopolysaccharide. Expression of lncRNA and miRNA was assessed by quantitative RT-PCR, and protein abundance was measured by western blot. Cytokine levels in mouse serum and cell culture supernatants were analyzed using enzyme-linked immunosorbent assay. Cerebral injury was evaluated by hematoxylin-eosin and Nissl staining, the ratio of brain dry weight/brain wet weight, and neurobehavior scoring. Ionized calcium-binding adaptor molecule 1 (IBA1) expression in the brain sections was assessed using immunohistochemistry. A total of 3681 lncRNAs were differentially expressed in the brain tissue of the ICH mice group compared with the Sham group. Of these, lncRNA metastasis suppressor-1 (Mtss1) expression was increased. Mtss1 knockdown by siRNA in the cellular model strongly suppressed TIR-domain-containing adapter-inducing interferon-β (TRIF) expression, P65 phosphorylation, and tumor necrosis factor (TNF)-α and interleukin (IL)-1β secretion. Mtss1 knockdown in ICH mice inhibited secondary brain injury and decreased IBA1, TNF-α, and IL-1β. Mtss1 was predicted to bind miR-709, and Mtss1 knockdown elevated miR-709 expression in the cellular inflammation model and ICH mice. High expression of Mtss1 promoted inflammatory brain injuries after ICH by enhancing inflammatory cytokine secretion and targeting miR-709 expression.

Missing-in-Metastasis/Metastasis Suppressor 1 Regulates B Cell Receptor Signaling, B Cell Metabolic Potential, and T Cell-Independent Immune Responses.

Efficient generation of antibodies by B cells is one of the prerequisites of protective immunity. B cell activation by cognate antigens via B cell receptors (BCRs), or pathogen-associated molecules through pattern-recognition receptors, such as Toll-like receptors (TLRs), leads to transcriptional and metabolic changes that ultimately transform B cells into antibody-producing plasma cells or memory cells. BCR signaling and a number of steps downstream of it rely on coordinated action of cellular membranes and the actin cytoskeleton, tightly controlled by concerted action of multiple regulatory proteins, some of them exclusive to B cells. Here, we dissect the role of Missing-In-Metastasis (MIM), or Metastasis suppressor 1 (MTSS1), a cancer-associated membrane and actin cytoskeleton regulating protein, in B cell-mediated immunity by taking advantage of MIM knockout mouse strain. We show undisturbed B cell development and largely normal composition of B cell compartments in the periphery. Interestingly, we found that MIM−/− B cells are defected in BCR signaling in response to surface-bound antigens but, on the other hand, show increased metabolic activity after stimulation with LPS or CpG. In vivo, MIM knockout animals exhibit impaired IgM antibody responses to immunization with T cell-independent antigen. This study provides the first comprehensive characterization of MIM in B cells, demonstrates its regulatory role for B cell-mediated immunity, as well as proposes new functions for MIM in tuning receptor signaling and cellular metabolism, processes, which may also contribute to the poorly understood functions of MIM in cancer.

Exosomal miR-29b from cancer-associated fibroblasts inhibits the migration and invasion of hepatocellular carcinoma cells.

BackgroundHepatocellular carcinoma (HCC) is often characterized by poor prognosis, high invasiveness and chemotherapeutic resistance, and its migration is strongly dependent on the specific tumor microenvironment. Fibroblasts, such as cancer-associated stromal fibroblasts (CAFs), are the main supporting cells in the tumor microenvironment. Thus, an understanding of how these cells communicate is required for HCC treatment.MethodsCAFs and paracancerous fibroblasts (PAFs) were isolated from patients’ surgical specimens, followed by exosome isolation and miRNA sequencing. The expression levels of miR-29b in different cell groups were detected by qPCR assay. Cell transfection with exogenous miRNAs was used to study whether the stromal cells could transfer miRNAs to HCC cells. Based on the preliminary results, a miR-29b mimic, inhibitor or miR-nonspecific mimic (miR-NSM) was further transfected into HepG2 and Huh7 cells prior to scratch wound healing and cell invasion experiments. Finally, the transfected cells were stained with Hoechst 33348.ResultsThe direct transfer of miR-29b from CAFs to HCC cells through an exosome was observed in this study. DNA methyltransferase 3b (DNMT3b) expression was directly inhibited by miR-29b, while metastasis suppressor 1 (MTSS1) expression was upregulated in HCC cells. Such changes further induced growth arrest and inhibited HCC cell invasion.ConclusionsExosomal miR-29b from CAFs can play a crucial role in the development, progression and metastasis of HCC. By functioning as a tumor suppressor that targets DNMT3b, miR-29b may serve as a potential therapeutic agent.

Metastasis suppressor 1 acts as a tumor suppressor by inhibiting epithelial-to-mesenchymal transition in triple-negative breast cancer.

This study aimed to analyze the function of metastasis suppressor 1 (MTSS1) in triple negative breast cancer (TNBC). MTSS1 expression in 30 TNBC and paracancerous tissues was measured by quantitative reverse transcriptase polymerase chain reaction. The prognostic value of MTSS1 was assessed by Kaplan-Meier analysis followed by the log-rank test. MCF7 cells were transfected with si-MTSS1, while MDA-MB-231 cells were transfected with pcDNA3.1-MTSS1. Cell proliferation assay and transwell assay were performed to investigate the effects of MTSS1 on the biological behavior of breast cancer cells. Immunofluorescence and western blot were used to detect the influence of MTSS1 on epithelial-mesenchymal transition (EMT) markers. MTSS1 expression was significantly lower in TNBC tissues compared with that in paracancerous tissues (0.012 vs. 0.370; P = 0.006). A lower MTSS1 expression level was also found in tumor tissues of patients with lymph node metastasis (P = 0.002) or tumor node metastasis stage (P = 0.010). Patients with low expression of MTSS1 (⩽ 0.009) had shorter disease-free survival (47.4 vs. 56.0 months; P = 0.012). The knockdown of MTSS1 in MCF7 cells inhibited cell proliferation, enhanced cell migration and invasion capacities, decreased the E-cadherin level, and increased the vimentin level, whereas overexpression of MTSS1 in MDA-MB-231 cells had the opposite effects (P < 0.05). Our findings demonstrated that MTSS1 regulates proliferation, invasion, migration, and EMT in TNBC, and that decreased MTSS1 is associated with shorter disease-free survival.

Overexpression of microRNA-96 is associated with poor prognosis and promotes proliferation, migration and invasion in cholangiocarcinoma cells via MTSS1.

MicroRNA-96 (miR-96) has been revealed serve an oncogenic role in various types of cancer. However, the role of miR-96 in cholangiocarcinoma (CCA) development and progression is yet to be elucidated. Thus, the aim of the present study was to investigate the role of miR-96 in CCA. The expression pattern of miR-96 in CCA tissues and cell lines was evaluated using reverse transcription-quantitative PCR analysis. Kaplan-Meier curves and Cox regression analyses were conducted to investigate the prognostic significance of miR-96 in CCA. Cell Counting Kit-8 and Transwell assays were performed to identify the functions of miR-96. The association between miR-96 and metastasis suppressor-1 (MTSS1) was verified using a dual-luciferase assay. The results demonstrated that miR-96 expression levels were increased in CCA tissues and cell lines compared with those in adjacent normal tissues and normal human intrahepatic biliary epithelial cell lines, respectively. High expression levels of miR-96 were significantly associated with lymph node metastasis, differentiation and TNM stage. In addition, upregulated expression of miR-96 was associated with a poorer prognosis and was predicted to be a prognostic factor in patients with CCA. Overexpression of miR-96 in vitro promoted CCA cell proliferation, migration and invasion. Additionally, MTSS1 was identified as a direct target of miR-96. The results of the present study indicated the clinical and biological importance of miR-96 as an oncogene in CCA. miR-96 may represent an independent prognostic biomarker and may promote CCA cell proliferation, migration and invasion by targeting MTSS1.

Metastasis inhibition by BRMS1 and miR-31 replacement therapy in claudin-low cell lines.

Objective(s):The growing trend of research demonstrates that dynamic expression of two metastasis repressor classes (metastasis suppressor genes and anti-metastatic miRNA) has a close relationship with tumor invasion and metastasis. Using different strategies, it was revealed that cellular levels of miR-31 and Breast cancer Metastasis Suppressor1 (BRMS1) protein, which are among the most significant modulators of metastasis, have a correlation with the cell’s capability for invading and metastasizing; cells containing higher levels of miR-31 or BRMS1 were less metastatic. This project was carried out to determine whether the combinations of miR-31 and BRMS1 genes are able to enhance the capability of repressing the claudin-low breast cancer cell (MDA-MB-231) invasion. Materials and Methods:This study used a restoration-based approach by miR-31 mimic and optimized BRMS1 gene sequences, which were cloned into a chimeric construct and transfected to the MDA-M231cells. Results:Our data revealed that the simultaneous expression of anti-metastasis miR and metastasis suppressor might inhibit migration and invasion in MDA-MB-231 cells efficiently.Conclusion:This combinatorial use of anti-metastatic miR and gene suggests a new therapeutic intervention for metastasis inhibition in MDA-MB-231.

A reciprocal feedback of Myc and lncRNA MTSS1-AS contributes to extracellular acidity-promoted metastasis of pancreatic cancer.

Rationale: Previous studies have reported on the role of extracellular acidity in the metastasis of numerous cancers. However, the involvement of long noncoding RNA (lncRNA) in the extracellular acidity-induced cancer metastasis of pancreatic cancer (PC) remains unclear.Methods: Different expression levels of lncRNAs in PC cells under normal and acidic conditions were compared by RNA sequencing (RNA-seq). The effects of antisense lncRNA of metastasis suppressor 1 (MTSS1-AS) on acidic PC cells were assessed by gain- and loss-of-function experiments. Fluorescence in situ hybridization, RNA immunoprecipitation, RNA pull-down, Western blot, luciferase reporter, and Chromatin immunoprecipitation assays were employed to determine the regulatory mechanisms of MTSS1-AS in the acidity-induced metastasis of PC cells. The expression of MTSS1-AS and associated pathways were compared in PC samples and peritumoral normal tissues.Results: RNA-seq demonstrated that MTSS1-AS was significantly downregulated in pancreatic cells cultured with the acidic medium. The overexpression of MTSS1-AS remarkably inhibited the acidity-promoted metastasis of PC cells by upregulating the expression of its sense gene metastasis suppressor 1 (MTSS1). Mechanistically, MTSS1-AS scaffolded the interaction between E3 ubiquitin-protein ligase STIP1 homology and U-box containing protein 1 (STUB1) and transcription regulator myeloid zinc finger 1 (MZF1), leading to ubiquitination-mediated degradation of MZF1. Further, MZF1 inhibited the expression of MTSS1 by binding to the MTSS1 promoter. Thus, the acidity-reduced MTSS1-AS facilitated the stability of MZF1 and its inhibitory effect on MTSS1 transcription, thereby promoting the metastasis of PC cells under acidic conditions. Moreover, MTSS1-AS was transcriptionally repressed by the binding of MYC proto-oncogene (Myc) with initiator (Inr) elements of the MTSS1-AS promoter. Meanwhile, MTSS1-AS mutually repressed the expression of Myc by impairing the MZF1-mediated transcription activation of Myc, thereby forming a negative feedback loop between MTSS1-AS and Myc in acidic PC cells. In accordance with the experimental results, MTSS1-AS and MTSS1 were downregulated in PC and correlated with poor overall survival.Conclusions: The results implicated that a reciprocal feedback loop between Myc and MTSS1-AS contributed to the extracellular acidity-promoted metastasis of PC, and indicated that MTSS1-AS was a valuable biomarker and therapeutic target for PC.

MTSS1 hypermethylation is associated with prostate cancer progression.

This study was conducted to evaluate the influence of DNA methylation of metastasis suppressor 1 (MTSS1) on prostate cancer (PCa) progression. Forty-nine paired PCa tissue samples and normal tissue samples from The Cancer Genome Atlas were analyzed. Methylome analysis, CpG island arrays and Hierarchical clustering were used to analyze methylation profiles of PCa tissues. MTSS1 methylation level was detected by methylation-specific PCR. Relative messenger RNA and the expression level of MTSS1 protein were identified by quantitative real-time PCR (qRT-PCR) and western blot analysis. The migration, invasion, proliferation, and cell cycle were detected separately by wound-healing assay, transwell chamber assay, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay and flow cytometry. The roles of MTSS1 in PCa progression were demonstrated in vivo by tumor formation assays in nude mice. MTSS1 expression was decreased in PCa tissues in comparison with paired adjacent normal prostate tissues. Compared to the methylation of MTSS1 in normal prostate tissues based on the MethHC website, the MTSS1 in PCa tissues was hypermethylated. The expression of MTSS1 detected by qRT-PCR and western blot analysis was found to be downregulated in PCa cells and tissues. The reduced expression of MTSS1 by small interfering RNA-MTSS1 was recovered by 5-aza-2'-deoxycytidine treatment. Besides, MTSS1 demethylation inhibited migration, invasion, and proliferation of PCa cells, and induced cell cycle to be arrested at G0/G1 phase. Furthermore, it was shown by tumor xenograft assay that MTSS1 inhibited the growth of tumor in vivo. Hypermethylated MTSS1 promoted PCa cells migration, invasion, and proliferation, and suppressed cell cycle arrest at the G0/G1 phase.

Long non‑coding RNA MEG3 suppresses the growth of glioma cells by regulating the miR‑96‑5p/MTSS1 signaling pathway

Glioma is one of the most common types of tumor of the central nervous system with high mobility and mortality. The prognosis of patients with high-grade glioma is poor. Therefore, it is urgent to develop the therapeutic strategies for the treatment of glioma. Long non-coding RNAs (lncRNAs) have been reported as potential inducers or suppressors of numerous types of tumors including glioma. Previous studies have revealed that lncRNA maternally expressed gene 3 (MEG3) is involved in the initiation and progression of cancer; however, the underlying mechanisms remain unclear. In the present study, MEG3 was downregulated in glioma tissue. In addition, downregulation of MEG3 was observed in human glioma cell lines compared with normal astrocyte cells. Furthermore, overexpressed MEG3 inhibited the proliferation, migration and invasion of glioma cells. Additionally, microRNA-96-5p (miR-96-5p) was a promising target of MEG3, and the promoting effects of miR-96-5p on cell growth and metastasis could be reversed by upregulated MEG3. Metastasis suppressor 1 (MTSS1) was predicted as the putative target of miR-96-5p, and its expression was restored by MEG3. In summary, the present data provided novel insight into the roles of MEG3 in glioma, and MEG3/miR-96-5p/MTSS1 signaling could be a promising therapeutic target for the treatment of patients with glioma.

MTSS1 inhibits metastatic potential and induces G2/M phase cell cycle arrest in gastric cancer.

Background: Metastasis suppressor 1 (MTSS1), a potential metastasis suppressor gene associated with tumor progression, may play an important role in cancer development. Our previous study demonstrated that MTSS1 was downregulated significantly when gastric cancer (GC) progressed and metastasized, suggesting that MTSS1 may be involved in the physiopathologic mechanism of GC.Purpose: The objective of this study was to evaluate the effect of MTSS1 expression on the biological behavior of gastric cancer cell both in vitro and in vivo.Materials and methods: The gain-and-loss function of MTSS1 in GC cells were analyzed after transfection with pEGFP-N1-MTSS1 and ShRNA431. Proliferation and invasion abilities were measured by means of plate clone formation assay and transwell assay. To further explore the underlying mechanism of MTSS1-induced tumor restrain, cell cycle distribution was analyzed using flow cytometry.Results: The results revealed that overexpression of MTSS1 significantly reduced proliferation, migration and invasion of GC cells in vivo and in vitro, while downregulation of MTSS1 had the opposite biological manifestations. Moreover, overexpression of MTSS1 induced accumulation of GC cells in G2/M phase, increased phosphorylated Cdc2 expression and decreased Cdc25C and cyclinB1 levels, suggesting MTSS1 could cause G2/M cell cycle arrest.Conclusion: Our data provided insight into an important role for MTSS1 in suppressing tumor cell proliferation, invasion and migration, indicating that MTSS, as a functional tumor suppressor in GC, could be a potential therapeutic target to prevent GC metastasis.