Expression Of MTSS1 Research Articles

Retraction Note: MicroRNA-411 promoted the osteosarcoma progression by suppressing MTSS1 expression.

Retraction Note: MicroRNA-411 promoted the osteosarcoma progression by suppressing MTSS1 expression.

Repulsive Sema3E-Plexin-D1 signaling coordinates both axonal extension and steering via activating an autoregulatory factor, Mtss1.

Axon guidance molecules are critical for neuronal pathfinding because they regulate directionality and growth pace during nervous system development. However, the molecular mechanisms coordinating proper axonal extension and turning are poorly understood. Here, metastasis suppressor 1 (Mtss1), a membrane protrusion protein, ensured axonal extension while sensitizing axons to the Semaphorin 3E (Sema3E)-Plexin-D1 repulsive cue. Sema3E-Plexin-D1 signaling enhanced Mtss1 expression in projecting striatonigral neurons. Mtss1 localized to the neurite axonal side and regulated neurite outgrowth in cultured neurons. Mtss1 also aided Plexin-D1 trafficking to the growth cone, where it signaled a repulsive cue to Sema3E. Mtss1 ablation reduced neurite extension and growth cone collapse in cultured neurons. Mtss1-knockout mice exhibited fewer striatonigral projections and irregular axonal routes, and these defects were recapitulated in Plxnd1- or Sema3e-knockout mice. These findings demonstrate that repulsive axon guidance activates an exquisite autoregulatory program coordinating both axonal extension and steering during neuronal pathfinding.

Association of rs35006907 Polymorphism with Risk of Dilated Cardiomyopathy in Han Chinese Population.

Several investigations have demonstrated the association of MTSS1 with left ventricular (LV) structure and function. A recently published study has even revealed that rs35006907 was associated with both MTSS1 expression and the risk of dilated cardiomyopathy (DCM). Our study intended to investigate the relationship between rs35006907 and the risk of DCM in the Han Chinese population. A total of 529 DCM and 600 healthy controls were recruited. We conducted genotyping for rs35006907 in all participants. Gene association studies were performed to assess the association between rs35006907 and the risk of DCM. A series of functional assays including western blot, realtime PCR and firefly luciferase reporter gene assays were conducted to illuminate the underlying mechanism. We found that rs35006907-A allele was significantly associated with reduced risk of DCM in additive (p= 0.004; OR=0.78; 95% CI=0.66-0.93) and recessive models (p= 0.0005; OR=0.56; 95%CI=0.41-0.78) when compared with the rs35006907-C allele. There were significant differences in the left ventricular end-diastolic diameter (LVEDD) and left ventricular ejection fraction (LVEF) between rs35006907-CC/AC and AA genotypes. Furthermore, the variant rs35006907-A allele presented lower reporter gene activity, reduced mRNA and protein expression levels when compared with the C allele. Our findings demonstrated that rs35006907-C allele increased the risk of DCM in Han Chinese population. Besides, rs35006907-C displayed higher reporter gene activity and increased MTSS1 expression in human samples.

Genes with dual proto-oncogene and tumor suppressor gene activities are frequently altered by protein losses in colon cancers

Cancer genes are largely categorized into tumor suppressor gene (TSG) and proto-oncogene, but many have dual activities depending on the cellular context. In the present study, we analyzed DYRK1B, ESRP1, MTSS1, ADAMTS1, and INPP5F genes known to possess the dual activities in sporadic colon cancers (CCs). By the mutation analysis, we identified DYRK1B, ESRP1, MTSS1, ADAMTS1, and INPP5F frameshift mutations in 2, 2, 3, 3, and 1 CCs in instability-high (MSI-H) cases (1.1–3.2% of MSI-H CCs), respectively, but not microsatellite stable (MSS) cases. One CC showed regional heterogeneous mutations (RHM) of ESRP1 mutation. Immunohistochemistry identified protein expression of ESRP1, MTSS1, and ADAMTS1 in the CCs, revealing that approximately 30% of CCs lost the protein expression irrespective of the MSI status. Our study showed that dual TSG and proto-oncogene genes DYRK1B, ESRP1, MTSS1, ADAMTS1, and INPP5F harbored low incidences of inactivating mutations, but that the protein losses were frequent in CCs. Our study suggests a possibility that the dual-function genes could be altered mainly at the expression level, which might contribute to CC pathogenesis.

Downregulated M6A modification and expression of circRNA_103239 promoted the progression of glioma by regulating the miR-182-5p/MTSS1 signalling pathway.

Glioma is a common type of tumor in the central nervous system, and the mortality is high. The prognosis of advanced glioma patients remains poor, and the therapeutic strategies need to be developed. The roles of circRNAs in glioma remain largely unknown. The aim of this study was to explore the functions circRNA_103239 in the biological behaviour changes of glioma cells. The expression of circRNA_103239 in clinical samples and glioma cells were examined using RT-qPCR. The targets of circRNA_103239 were predicted using bioinformatics approach. Gain- and loss-of-function study were carried out. The proliferation of transfected cells were evaluated by CCK-8 assay. Migratory and invasive activities of the cells were examined using wound healing, colony formation and transwell assay. Tumor growth was also evaluated in vivo. The results indicated that the expression of circRNA_103239 was predominantly detected in the cytoplasma of glioma cells. In addition, the expression of circRNA_103239 was down-regulated in glioma, and up-regulated circRNA_103239 inhibited the progression of glioma. Furthermore, miR-182-5p was the novel target of circRNA_103239 in glioma, and MTSS1 was the putative downstream molecule of circRNA_103239/miR-182-5p axis. Additionally, circRNA_103239 suppressed the progression of glioma in a miR-182-5p/MTSS1 dependent manner. Moreover, circRNA_103239 inhibited tumour growth in vivo, and the expression of circRNA_103239 was regulated by METTL14-mediated m6A modification. In summary, in normal cells, METTL14 mediated the m6A modification and expression of circRNA_103239, which sponging miR-182-5p and inducing the expression of MTSS1, subsequently inhibiting the EMT; whereas in glioma cells, downregulated METTL14 induced downregulated m6A modification and expression of circRNA_103239, further resulting in the up-regulation of miR-182-5p and down-regulation of MTSS1, consequently promoting the EMT of glioma cells and triggering the progression of tumor.

Abstract 13146: Cardioprotective Effects of Mtss1 Reduction in Dilated Cardiomyopathy

Introduction: MTSS1 is an I-BAR protein that interacts with the actin cytoskeleton and the cell membrane and is speculated to play a role in cell motility, tumor metastasis, and cardiogenesis. Enhancer variants that reduce the expression of MTSS1 in the human left ventricle have been associated with cardioprotective traits in genome-wide association studies. However, the effect of MTSS1 downregulation on the development of heart disease has not been studied in experimental models. Here we tested the hypothesis that reduction of MTSS1 protects against dilated cardiomyopathy (DCM) in vitro and in vivo. Methods: We used CRISPR-Cas9 to knock out MTSS1 in induced pluripotent stem cells (iPSCs) harboring pathogenic variants from patients with severe DCM. DCM iPSC lines with and without MTSS1 were then differentiated into cardiomyocytes and phenotyped in vitro. A DCM mouse model containing a TPM1 D230N transgene was crossed with a mouse model heterozygous for Mtss1 knockout. Progeny from this F1 cross were assessed for differences in cardiac structure and function via echocardiography. Results: MTSS1 deletion restored the beta-adrenergic response in DCM iPSC cardiomyocytes. In parallel, Mtss1 deletion partially rescued DCM-associated phenotypes including left ventricular dilation and reduced ejection fraction in mice. Conclusions: Our initial results suggest a causal link between MTSS1 reduction and cardioprotection in DCM. Inhibiting cardiac MTSS1 may hold therapeutic potential for DCM, though the cellular mechanisms through which MTSS1 affects cardiac phenotypes remain under investigation.

CircFBXO7/miR-96-5p/MTSS1 axis is an important regulator in the Wnt signaling pathway in ovarian cancer

BackgroundCircRNAs are a novel class of evolutionarily conserved noncoding RNA molecules that form covalently closed continuous loop structures without 5′ caps and 3′ poly(A) tails. Accumulating evidence suggests that circRNAs play important regulatory roles in cancer and are promising biomarkers for cancer diagnosis and prognosis, as well as targets for cancer therapy. In this study, we identify and explore the role of a novel circRNA, circFBXO7, in ovarian cancer.MethodsrRNA-depleted RNA-sequencing was performed to identify differentially expressed circRNAs between ovarian cancerous and normal tissues. qRT-PCR and single-molecule RNA in-situ hybridization was used to quantify circFBXO7 expression in tumor tissues. The association of circFBXO7 expression with patient prognosis was evaluated by Kaplan–Meier survival analysis. The biological function of circFBXO7 was also investigated using loss-of-function and gain-of-function assays in vivo and in vitro. Luciferase reporter and TOP/FOP-Flash reporter assays were then conducted together with RNA immunoprecipitation and western blot to assess the circFBXO7/miR-96-5p/MTSS1/Wnt/β-catenin axis.ResultscircFBXO7 was downregulated in ovarian cancer which was associated with poor prognosis. Biologically, circFBXO7 overexpression significantly suppressed ovarian cancer cell proliferation, migration, and invasion in vitro, and inhibited tumor growth and metastasis in vivo, whereas its knockdown exerted an opposite role. Mechanistically, circFBXO7 functioned as a competing endogenous RNA for miR-96-5p to regulate the expression of MTSS1. Consequently, downregulation of MTSS1 led to excessive accumulation of β-catenin and increased phosphorylation of GSK3β, leading to the translocation of β-catenin to the nucleus, thereby activating the Wnt/β-catenin signaling pathway and ultimately promoting ovarian cancer progression.ConclusionsOur findings indicate that circFBXO7 acts as a bone fide tumor suppressor in ovarian cancer and that the circFBXO7/miR-96-5p/MTSS1 axis is an important regulator in the Wnt/β-catenin signaling pathway which may provide a promising target for ovarian cancer therapy.

Downregulation of MTSS1 in acute myeloid leukemia is associated with a poor prognosis, chemotherapy resistance, and disease aggressiveness

Despite recent approval of targeted drugs for acute myeloid leukemia (AML) therapy, chemotherapy with cytosine arabinoside and anthracyclines remains an important pillar of treatment. Both primary and secondary resistance are frequent and associated with poor survival, yet the underlying molecular mechanisms are incompletely understood. In previous work, we identified genes deregulated between diagnosis and relapse of AML, corresponding to therapy naïve and resistant states, respectively. Among them was MTSS1, whose downregulation is known to enhance aggressiveness of solid tumors. Here we show that low MTSS1 expression at diagnosis was associated with a poor prognosis in AML. MTSS1 expression was regulated by promoter methylation, and reduced by cytosine arabinoside and the anthracycline daunorubicin. Experimental downregulation of MTSS1 affected the expression of numerous genes. It induced the DNA damage response kinase WEE1, and rendered human AML cell lines more resistant to cytosine arabinoside, daunorubicin, and other anti-cancer drugs. Mtss1 knockdown in murine MLL-AF9-driven AML substantially decreased disease latency, and increased leukemic burden and ex vivo chemotherapy resistance. In summary, low MTSS1 expression represents a novel factor contributing to disease aggressiveness, therapy resistance, and poor outcome in AML.

93137 Interrogating cardio-protective MTSS1 variants in human populations

ABSTRACT IMPACT: It is our hope that a better understanding of the relationship between genetic variants that influence heart failure precursor traits will not only inform clinical care, but enable better assessment of inherited risk and will identify new biological targets for drug development. OBJECTIVES/GOALS: In this project, using a large-scale human genomic dataset with extensive phenotype data available, we intend to interrogate the known MTSS1 variants that have been associated with heart failure (HF) in previous GWAS studies in order to understand the directionality and mechanisms of their effects. METHODS/STUDY POPULATION: Data was obtained from the UK Biobank, a large prospective cohort of ˜500,000 patients across the United Kingdom with extensive phenotype data, including ˜50,000 patients with cardiac MRI and ˜200,000 with whole exome sequencing. We test for associations between genetic variants at the MTSS1 locus and HF precursor traits using logistic regression or linear regression, adjusting for age, gender, and principal components (PCs) of ancestry. For rare variant analyses we ‘bin’ rare variants (MAF < 0.01) using the software tool BioBin to aggregate low frequency genetic variants into single genetic units. RESULTS/ANTICIPATED RESULTS: Preliminary data have shown that variants in the known MTSS1 enhancer region which reduce MTSS1 expression are associated with smaller, more contractile hearts. We anticipate that common variants known to reduce enhancer activity will attenuate heart failure precursor traits, will be associated with a reduced risk clinical heart failure, and will favorably impact clinical outcomes once HF is established. We also anticipate that rare exonic variants predicted to impair MTSS1 function will attenuate heart failure precursor traits. DISCUSSION/SIGNIFICANCE OF FINDINGS: Through this work, we intend to take advantage of multiple novel approaches to better understand a complex disease process, identify a new potential therapeutic target (namely one that targets cardiac function), and to determine which patient subgroups will benefit from this our therapeutic interventions and why.

Analysis of RPL37A, MTSS1, and HTRA1 expression as potential markers for pathologic complete response and survival.

Non-metastatic locally advanced breast carcinoma (LABC) treatment involves neoadjuvant chemotherapy (NCT). We evaluated the association of clinical-pathological data and immunoexpression of hormone receptors, HER2 and Ki67, and new biomarkers, RPL37A, MTSS1 and HTRA1, with pathological complete response (PCR) or tumour resistance (stable disease or disease progression), disease-free survival (DFS) and cancer-specific survival (CSS). This is a retrospective study of 333 patients with LABC who underwent NCT. Expression of MTSS1, RPL37A and HTRA1/PRSS11 was evaluated by immunohistochemistry in TMA slides. Cutoff values were established for low and high tumour expression. ROC plotter evaluated response to NCT. Chi-square test for factors related to PCR, and Kaplan-Meier test and Cox model for factors related to DFS and CSS were prformed. The mean follow-up was 70.0months and PCR rate was 15.6%. At 120months, DFS rate was 32.5% and CSS rate was 67.1%. In multivariate analysis, there was an association between: (1) necrosis presence, intense inflammatory infiltrate, ER absence, HER2 molecular subtype and high RPL3A expression with increased odds of PCR; (2) lymph node involvement (LNI), high Ki67, low RPL37A and high HTRA1 expression with increased risk for NCT non-response; (3) LNI, high proliferation, necrosis absence, low RPL37A and high HTRA1 expression with increased recurrence risk; (4) advanced LNI, ER negative tumours, high HTRA1, low RPL37A expression and desmoplasia presence with higher risk of cancer death. RPL37A is a potential biomarker for response to NCT and for prognosis. Additional studies evaluating HTRA1 and MTSS1 prognostic value are needed.

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.

MTSS1 is epigenetically regulated in glioma cells and inhibits glioma cell motility

Epigenetic silencing by DNA methylation in brain tumors has been reported for many genes, however, their function on pathogenesis needs to be evaluated. We investigated the MTSS1 gene, identified as hypermethylated by differential methylation hybridization (DMH). Fifty-nine glioma tissue samples and seven glioma cell lines were examined for hypermethylation of the MTSS1 promotor, MTSS1 expression levels and gene dosage. GBM cell lines were treated with demethylating agents and interrogated for functional consequences of MTSS1 expression after transient transfection. Hypermethylation was significantly associated with IDH1/2 mutation. Comparative SNP analysis indicates higher incidence of loss of heterozygosity of MTSS1 in anaplastic astrocytomas and secondary glioblastomas as well as hypermethylation of the remaining allele. Reversal of promoter hypermethylation results in an increased MTSS1 expression. Cell motility was significantly inhibited by MTSS1 overexpression without influencing cell growth or apoptosis. Immunofluorescence analysis of MTSS1 in human astrocytes indicates co-localization with actin filaments. MTSS1 is down-regulated by DNA methylation in glioblastoma cell lines and is part of the G-CIMP phenotype in primary glioma tissues. Our data on normal astrocytes suggest a function of MTSS1 at focal contact structures with an impact on migratory capacity but no influence on apoptosis or cellular proliferation.

TET2 Activity Is Modulated By SIRT1-Mediated Protein Deacetylation: A Potential Therapeutic Target in Myelodysplastic Syndrome

DNA methylation at cytosine position 5 (5mC) is a genetic modification that regulates gene expression and is critical for cancer initiation and development. The methylcytosine dioxygenase TET2 participates in active DNA demethylation by converting 5mC to 5-hydroxymethylcytosine (5hmC) and its subsequent intermediates thereby regulating gene expression. TET2 gene is frequently mutated in hematological disorders, including 15-25% of myelodysplastic syndrome (MDS) cases. Loss of TET2 function leads to DNA hypermethylation and subsequent dysregulated gene expression in hematopoietic stem cells, and has been considered as an initial step of myeloid malignant transformation including MDS and acute myeloid leukemia (AML). While enzymatic activity of TET2 is well studied, little is known about post-translational modifications (PTMs) that regulate its activity in hematopoietic cells.Lysine acetylation, one of the most crucial PTMs, occurs in a variety of proteins and modulates protein-protein or protein-nucleic acids interactions. Here, we first observed that ectopic expression of histone acetyltransferase EP300 or CREB binding protein (CBP) increased the endogenous TET2 acetylation in 293T cells. Mass spectrometry analysis of TET2 identified several conserved acetylated lysine residues located on the exterior surface of its catalytic domain (CD), which is predicted to be essential for the interaction of TET2 with DNA. Modeling of TET2/DNA interaction using x-ray crystal structure (PDB code: 4NM6) indicates acetylated TET2 interferes with DNA binding thereby impairing the catalytic activity of the enzyme. Like other acetylated proteins, TET2 modification is reversible, since ectopic expression of the protein deacetylase Sirtuin1 (SIRT1) significantly decreases acetylation of TET2. A domain mapping analysis revealed that SIRT1 preferentially interacts with TET2 CD, further supporting the regulatory role of SIRT1 on TET2. To explore the role of SIRT1 mediated deacetylaion of TET2 in more physiological condition, SIRT1 knockdown (KD) MDS-L cells as well as SIRT1 knockout (KO) murine hematopoietic c-kit+ cells were used. In MDS-L cells derived from a MDS patient, SIRT1 KD promoted hyperacetylation of endogenous TET2 which is associated with 50% decrease in 5hmC levels compared to control (p=0.03, n=3). Similarly, SIRT1 KO murine c-Kit+ cells showed TET2 hyperacetylation and 62% decrease in 5hmC compared to wildtype (WT) counterpart (p=0.009, n=5). Phenotypically, the transforming ability of SIRT1 shRNA transduced MDS-L cells was evaluated in vitro through serial replating assay. In contrast to first plating which showed no difference between two groups, the number of colonies derived from SIRT1 KD cells was 2.39 fold higher than that from the control shRNA transduced group after two rounds of replating (p=0.0002, n=3). Importantly, we tested the in-vivo effect of SIRT1 KD on MDS-L cells engrafted in immunodeficient NSGS mice. SIRT1 KD significantly enhanced MDS-L cell engraftment compared to control shRNA (50±5% of human CD45+ cells in SIRT1 KD group vs. 19±4% human CD45+ cells in control group, p=0.003, n=6). Interestingly, increased transformation capacity of SIRT1 KD MDS-L cells was associated with decreased expression of TET2 regulated tumor suppressor genes. For example, expression levels of Mtss1 and Dusp6 were significantly decreased in SIRT1 KD MDS-L cells compared to control shRNA counterpart (Mtss1, 49±5% decrease compared to control, p=0.005; Dusp6, 25±2% decrease compared to control, p=0.01). Similar results were observed in SIRT1 KO cells. The validation of physical binding of TET2 to its targets is ongoing. Moreover, the effect of an SIRT1 allosteric activator-SRT1720 in MDS-L cells is similar to that of Vitamin C, a known TET2 activator. Specifically, SRT1720 significantly increased Mtss1 expression in MDSL cells (p=0.0005, n=3), indicating that SIRT1 agonist may lead to activation of TET2 downstream tumor suppressor genes.In summary, our data demonstrate that TET2 activity can be functionally modified by acetylation and may be enhanced in MDS patients that do not harbor loss-of-function mutations through the SIRT1 mediated deacetylation. These results support further exploration of molecular mechanisms inducing TET2 acetylation, and evaluation of SIRT1 activation as a potential therapeutic approach in MDS. DisclosuresNo relevant conflicts of interest to declare.

Differential effects of MTSS1 on invasion and proliferation in subtypes of non-small cell lung cancer cells.

Non-small cell lung cancer (NSCLC) accounts for >80% of all cases of lung cancer and can be divided into lung adenocarcinoma (LAC), large-cell carcinoma (LCC), and squamous cell carcinoma (SCC). Accumulating evidence suggests that MTSS1, which is a newly discovered protein associated with tumor progression and metastasis, may have differential roles in cancer malignancy. As it has been demonstrated that MTSS1 is overexpressed in NSCLC and may be an independent prognostic factor in patients with SCC, the present study explored the differential roles of MTSS1 in the invasion and proliferation of different subtypes of NSCLC. Stable overexpression and knockdown of MTSS1 was performed in human NSCLC H920 (LAC), H1581 (LCC) and SW900 cell lines (SCC), and western blot, cell invasion, proliferation and FAK activity analyses were used to investigate the effects. Overexpression of MTSS1 enhanced the invasion and proliferation abilities of H920 and H1581 cells, and these effects were abolished by treatment with selective FAK inhibitor 14, which did not affect the expression of MTSS1. Notably, overexpression of MTSS1 inhibited invasion and proliferation in SW900 cells, and this effect was enhanced by the selective FAK inhibitor. Knockdown of MTSS1 decreased the invasion and proliferation abilities of H920 and H1581 cells, whereas knockdown increased invasion and proliferation in SW900 cells. Furthermore, while overexpression of MTSS1 induced FAK phosphorylation and activity in H920 and H1581 cells, MTSS1 overexpression inhibited FAK phosphorylation/activity in SW900 cells. Knockdown of MTSS1 decreased FAK phosphorylation/activity in H920 and H1581 cells, whereas knockdown increased these processes in SW900 cells. To the best of our knowledge, the present study was the first to demonstrate that MTSS1 has differential roles in various subtypes of NSCLC, acting via a FAK-dependent mechanism. The results indicated that MTSS1 may enhance invasion and proliferation in LAC and LCC cells, whereas MTS11 inhibits these processes in SCC cells. These findings provide novel insight into the functional role of MTSS1 in cancer and may help elucidate therapeutic strategies for the treatment of various types of cancer.

Mtss1 is a critical epigenetically regulated tumor suppressor in CML.

Chronic myeloid leukemia (CML) is driven by malignant stem cells that can persist despite therapy. We have identified Metastasis suppressor 1 (Mtss1/MIM) to be downregulated in hematopoietic stem and progenitor cells from leukemic transgenic SCLtTA/Bcr-Abl mice and in patients with CML at diagnosis, and Mtss1 was restored when patients achieved complete remission. Forced expression of Mtss1 decreased clonogenic capacity and motility of murine myeloid progenitor cells and reduced tumor growth. Viral transduction of Mtss1 into lineage-depleted SCLtTA/Bcr-Abl bone marrow cells decreased leukemic cell burden in recipients, and leukemogenesis was reduced upon injection of Mtss1-overexpressing murine myeloid 32D cells. Tyrosine kinase inhibitor (TKI) therapy and reversion of Bcr-Abl expression increased Mtss1 expression but failed to restore it to control levels. CML patient samples revealed higher DNA methylation of specific Mtss1 promoter CpG sites that contain binding sites for Kaiso and Rest transcription factors. In summary, we identified a novel tumor suppressor in CML stem cells that is downregulated by both Bcr-Abl kinase-dependent and -independent mechanisms. Restored Mtss1 expression markedly inhibits primitive leukemic cell biology in vivo, providing a therapeutic rationale for the Bcr-Abl-Mtss1 axis to target TKI-resistant CML stem cells in patients.

Abstract 4139: Role of Akt2 in cell survival and metastasis of colorectal cancer (CRC) cells

Abstract Background: Colorectal Cancer (CRC) is the second highest cause of cancer related deaths in United States. Metastatic dissemination of CRC cells to distant organs (primarily to the liver and lungs) makes the disease more lethal and incurable. Inappropriate cell survival signaling mechanisms contribute to successful colonization of cells at metastatic sites. Akt is a major cell survival-signaling node, which undergoes aberrant activation in various types of cancer. The Akt family has three members: Akt1, Akt2 and Akt3 which share structural homology and have similar mechanism of activation; however, differences in the phenotype of Akt1, Akt2 and Akt3 knock out mice suggest that they have non-redundant functional characteristics. Recently Akt2 has been identified as a significant contributor to colon cancer malignancy in addition to Akt1. Earlier reports have shown that knockdown of Akt2 results in reduced liver metastasis of CRC cells, however there are no studies related to the mechanism responsible for the reduction in metastasis. We observed a significant increase in the expression of Akt2 (microarray analysis) in liver metastatic samples formed by highly metastatic IGF1R-dependent CRC cells in comparison to the primary tumor. This was further confirmed by western blot and immunohistochemistry (IHC) analysis. Additionally, correlative studies using human primary colon carcinoma and corresponding liver metastatic samples showed a significant (p<0.001) increase in the expression of Akt2. These preliminary data led us to hypothesize that Akt2 may be playing a role in regulating cell survival and metastasis of CRC cells. Materials and Methods: IGF1R-dependent CRC cells (GEO and CBS) were used for the study. Two doxycycline inducible shRNAs for Akt2 were introduced by lentiviral transfection. Non-Targeting shRNA was used as control. Results: shRNA-mediated knockdown of Akt2 led to reduction in the expression of XIAP and survivin. We and others have shown that these IAPs (XIAP and survivin) are implicated to play an important role in cancer cell survival and metastasis. Furthermore, loss of Akt2 resulted in loss of pBad (S136), which is an essential cell survival marker. Loss of pBad results in increased cell death by PARP activation. Akt2 knockdown also affects cell survival by increasing p21 and decreasing the expression of cyclin E. PCR array analysis for metastatic genes revealed that a metastatic suppressor gene MTSS1 was 9 fold increased on knockdown of Akt2. It has been shown that MTSS1 inhibits metastasis by affecting cell junction assembly and stability. Conclusion: We have shown that loss of Akt2 promotes cell death and inhibits cell proliferation. This is the first study, which suggests the mechanism of Akt2 mediated cell death by XIAP and survivin downregulation. These results suggest that Akt2 inhibits metastasis by increasing the expression of MTSS1. Citation Format: Ekta Agarwal. Role of Akt2 in cell survival and metastasis of colorectal cancer (CRC) cells. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4139. doi:10.1158/1538-7445.AM2015-4139

Identification of the Adapter Molecule MTSS1 as a Potential Oncogene-Specific Tumor Suppressor in Acute Myeloid Leukemia.

The adapter protein metastasis suppressor 1 (MTSS1) is implicated as a tumor suppressor or tumor promoter, depending on the type of solid cancer. Here, we identified Mtss1 expression to be increased in AML subsets with favorable outcome, while suppressed in high risk AML patients. High expression of MTSS1 predicted better clinical outcome of patients with normal-karyotype AML. Mechanistically, MTSS1 expression was negatively regulated by FLT3-ITD signaling but enhanced by the AML1-ETO fusion protein. DNMT3B, a negative regulator of MTSS1, showed strong binding to the MTSS1 promoter in PML-RARA positive but not AML1-ETO positive cells, suggesting that AML1-ETO leads to derepression of MTSS1. Pharmacological treatment of AML cell lines carrying the FLT3-ITD mutation with the specific FLT3 inhibitor PKC-412 caused upregulation of MTSS1. Moreover, treatment of acute promyelocytic cells (APL) with all-trans retinoic acid (ATRA) increased MTSS1 mRNA levels. Taken together, our findings suggest that MTSS1 might have a context-dependent function and could act as a tumor suppressor, which is pharmacologically targetable in AML patients.

MTSS1 is a metastasis driver in a subset of human melanomas

In cancers with a highly altered genome, distinct genetic alterations drive subsets rather than the majority of individual tumours. Here we use a sequential search across human tumour samples for transcript outlier data points with associated gene copy number variations that correlate with patient's survival to identify genes with pro-invasive functionality. Employing loss and gain of function approaches in vitro and in vivo, we show that one such gene, MTSS1, promotes the ability of melanocytic cells to metastasize and engages actin dynamics via Rho-GTPases and cofilin in this process. Indeed, high MTSS1 expression defines a subgroup of primary melanomas with unfavourable prognosis. These data underscore the biological, clinical and potential therapeutic implications of molecular subsets within genetically complex cancers.

Expression of MTSS1 in cholangiocarcinoma tissue and its relationship with the prognosis of patients

Objective To investigate the expression of MTSS1 in cholangiocarcinoma tissue and its relationship with the prognosis of patients.Methods The specimens of bile duct of 49 patients with hilar cholangiocarcinoma who received surgical excision at the Eastern Hepatobiliary Surgery Hospital from January 2003 to December 2005 were collected.Tissue microarrays of the 49 samples of hilar cholangiocarcinomas and the 10samples of adjancent normal bile duct epithelial tissue were constructed.The expression of MTSS1 was detected by the immunohistochemical staining.The pcDNA3.1-MTSS1 was transferred into the RBE cells and the abilities of proliferation of REB cells were measured by MTT assay.The patients were followed up via out-patient examination and telephone till May 2012.The measurement data were analyzed using the t test,and the count data were analyzed using the chi-square test,the survival curve was drawn by the Kaplan-Meier method,the survival was analyzed using the Log-rank test,and multivariate analysis was done using the COX regression model.Results The results of immunohistochemical staining showed that the expression rate of MTSS1 was 10/10 in the adjacent normal epithelial tissue of bile duct,while 59.2％ (29/49) in the cholangiocarcinoma tissues.The proliferative rate of cholangiocarcinoma cells transfected with MTSS1 was 1.55 ±0.05,which was significantly lower than 2.32 ±0.08 of cholangiocarcinoma cells without transfection of MTSS1 (t =4.454,P ＜ 0.05).Gender,age,TNM stage,T stage,differentiation,neural invasion and diameter of tumor did not influence the expression of MTSS1 (x2=0.211,3.471,0.507,0.507,0.368,0.882,0.660,P ＜ 0.05),while lymph node metastasis influenced the expression of MTSS1 (x2=10.436,P ＜ 0.05).All the patients were followed up for 1-59 months,and the median time for follow-up was 16 months.The median tumor-free survival time was 17.9 months in patients with positive expression of MTSSI,and 11.3 months of patients with negative expression of MTSS1,with no significant difference (Log-rank value =3.707,P ＞ 0.05).The median survival time was 34.9 months in patients with positive expression of MTSS1,which was significantly longer than 18.7 months of patients with negative expression of MTSS1 (Log-rank value =5.671,P ＜0.05).Multivariate analysis showed that MTSS1 was not the independent risk factor influencing the prognosis of patients (x2 =0.406,P ＞ 0.05).Conclusions The expression of MTSS1 is decreased in cholangiocarcinoma tissue,which negatively correlates with lymph node metastasis.MTSS1 could be used as a biomarker in predicting the prognosis of patients with cholangiocarcinoma. Key words: Cholangiocarcinoma; MTSS1; Prognosis

MicroRNA-182-5p Promotes Cell Invasion and Proliferation by Down Regulating FOXF2, RECK and MTSS1 Genes in Human Prostate Cancer

Recently miR-182 has been reported to be over-expressed in prostate cancer (PC) tissues, however detailed functional analysis of miR-182-5p has not been carried out. The purpose of this study was to: 1. analyze the function of miR-182-5p in prostate cancer, 2. assess its usefulness as a tumor marker, 3. identify miR-182-5p target genes in PC, 4. investigate the potential for miR-182-5p inhibitor to be used in PC treatment. Initially we found that miR-182-5p expression was significantly higher in prostate cancer tissues and cell lines compared to normal prostate tissues and cells. Moreover high miR-182-5p expression was associated with shorter overall survival in PC patients. To study the functional significance of miR-182-5p, we knocked down miR-182-5p with miR-182-5p inhibitor. After miR-182-5p knock-down, prostate cancer cell proliferation, migration and invasion were decreased. We identified FOXF2, RECK and MTSS1 as potential target genes of miR-182-5p using several algorithms which was confirmed by 3’UTR luciferase assay and Western analysis. Knock-down of miR-182-5p also significantly decreased in vivo prostate tumor growth. In conclusion this is the first report documenting that over-expression of miR-182-5p is associated with prostate cancer progression and potentially useful as a prognostic biomarker. Also knock down of miR-182-5p in order to increase expression of tumor suppressor genes FOXF2, RECK and MTSS1 may be of therapeutic benefit in prostate cancer treatment.