Fragments of SLIT3 inhibit cellular migration

Controlled Delivery of Slit3 Proteins from Alginate Microbeads Inhibits In Vitro Angiogenesis

BACKGROUND

The Slit-Robo pathway is a key regulator of angiogenesis and cellular function in experimental models. Slit3 proteins exhibit both proangiogenic and antiangiogenic properties, but the exact mechanism remains unclear. It is theorized that Slit3 may be a potential treatment for vascular diseases and cancer.

METHODS

Slit3 labeled with I-125 was encapsulated in microbeads composed of low-viscosity alginate of high-glucuronic acid content, first coated with poly-L-ornithine for various durations and finally with low-viscosity high mannuronic acid. Gamma counter was used to measure microbead encapsulation efficiency and Slit3 release. Markers of angiogenesis were assessed with Boyden chamber, scratch wound, and Matrigel tube formation assays using human umbilical vein and mouse endothelial cells.

RESULTS

On incubation of Slit3-loaded microbeads, there was an initial burst phase release of Slit3 for the first 24 h followed by sustained release for 6 to 12 d. Microbead composition determined encapsulation efficiency and rate of release; Slit3 encapsulation was most efficient in microbeads with lower low-viscosity alginate of high-glucuronic acid content concentrations (1.5%) and no poly-L-ornithine coating. Compared with controls (media alone), Slit3 microbeads significantly inhibited in vitro cellular migration, endothelial cell migration for wound closure at 24 and 48 h and endothelial tube formation (P < 0.001, respectively).

CONCLUSIONS

Slit3 can be effectively encapsulated and delivered via a controlled release pattern using alginate microbeads. Microbead encapsulation reduces in vitro endothelial tube formation and inhibits cellular migration to impair angiogenesis. Thus, Slit3 microparticles may be explored as a therapeutic option to mitigate tumor proliferation.

Tissue-specific angiogenic and invasive properties of human neonatal thymus and bone MSCs: Role of SLIT3-ROBO1

Although mesenchymal stem/stromal cells (MSCs) are being explored in numerous clinical trials as proangiogenic and proregenerative agents, the influence of tissue origin on the therapeutic qualities of these cells is poorly understood. Complicating the functional comparison of different types of MSCs are the confounding effects of donor age, genetic background, and health status of the donor. Leveraging a clinical setting where MSCs can be simultaneously isolated from discarded but healthy bone and thymus tissues from the same neonatal patients, thereby controlling for these confounding factors, we performed an in vitro and in vivo paired comparison of these cells. We found that both neonatal thymus (nt)MSCs and neonatal bone (nb)MSCs expressed different pericytic surface marker profiles. Further, ntMSCs were more potent in promoting angiogenesis in vitro and in vivo and they were also more motile and efficient at invading ECM in vitro. These functional differences were in part mediated by an increased ntMSC expression of SLIT3, a factor known to activate endothelial cells. Further, we discovered that SLIT3 stimulated MSC motility and fibrin gel invasion via ROBO1 in an autocrine fashion. Consistent with our findings in human MSCs, we found that SLIT3 and ROBO1 were expressed in the perivascular cells of the neonatal murine thymus gland and that global SLIT3 or ROBO1 deficiency resulted in decreased neonatal murine thymus gland vascular density. In conclusion, ntMSCs possess increased proangiogenic and invasive behaviors, which are in part mediated by the paracrine and autocrine effects of SLIT3.

Suppression of Slit3 induces tumor proliferation and chemoresistance in hepatocellular carcinoma through activation of GSK3β/β-catenin pathway

Background

It is essential to understand the mechanisms responsible for hepatocellular carcinoma (HCC) progression and chemoresistance in order to identify prognostic biomarkers as well as potential therapeutic avenues. Recent findings have shown that SLIT3 appears to function as a novel tumor suppressor gene in various types of cancers, yet its clinical correlation and role in HCC has not been understood clearly.

Methods

We determined the transcript levels of Slit3 in tumor and adjacent normal tissues within two cohorts (N = 40 and 25) of HCC patients, and correlated the gene expression with the clinicopathological data. Subsequently, the functional effects and underlying molecular mechanisms of Slit3 overexpression and/or repression were studied using cell-line and mouse models.

Results

Our results demonstrated a repression in Slit3 expression in nearly 50% of the HCC patients, while the overall expression of Slit3 inversely correlated with the size of the tumor in both cohorts of patients. Stable down-regulation of Slit3 in HCC cell-lines induced cell proliferation in vitro and tumor growth in vivo, while stable Slit3 overexpression repressed these effects. Molecular investigations showed that the stable Slit3 repression-induced cell proliferation was associated with a higher expression of β-catenin and a repressed GSK3β activity. Moreover, Slit3-repression induced chemoresistance to sorafenib, oxaliplatin and 5-FU through impairment of β-catenin degradation and induction of cyclin D3 and survivin levels. The effects induced by stable Slit3-repression were diminished by transient repression of β-catenin by siRNA approach.

Conclusion

This study suggests that Slit3 acts as a tumor suppressor in HCC by repressing the tumor growth and thus tumor progression. Low Slit3 level indicates a poor response of HCC cells to chemotherapy. Restoration or overexpression of Slit3 is a potential therapeutic approach to repress the tumor growth and enhance the efficacy of chemotherapeutic agents.

Electronic supplementary material

The online version of this article (10.1186/s12885-018-4326-5) contains supplementary material, which is available to authorized users.

Robo3A and Robo3B expression is regulated via alternative promoters and mRNA stability

Background

The transmembrane receptor family Roundabout (Robo) was described to have an essential role in the developing nervous system. Recent studies demonstrated that Robo3 shows an altered expression in rheumatoid arthritis as well as in melanoma.

Context and purpose of the study

Until today no detailed studies of the two Robo3 isoforms (Robo3A and Robo3B) and their roles in rheumatoid arthritis synovial fibroblasts, respectively malignant melanoma are available. To get a better understanding regarding the role of Robo3A and Robo3B in the molecular process of rheumatoid arthritis and melanoma the exact characterization of expression and regulation is object of this study.

Results

mRNA and protein expression of the transcriptional variants were analyzed by quantitative RT-PCR respectively western blotting and revealed particularly enhanced expression of Robo3B in rheumatoid arthritis and melanoma. Promoter assays and inhibitor studies also disclosed that there is apparently a cell- and isoform-specific regulation of the Robo3 expression. Finally, dissimilar mRNA stabilities of Robo3A and Robo3B are identified as decisive posttranscriptional gene expression control.

Conclusion

In summary, this study supported an isotype specific role of Robo3B in disease hinting to different functional roles of each isoform.

Slit-miR-218-Robo axis regulates retinal neovascularization

miR-218 is an important intronic microRNA (miRNA or miR) which is known to regulate angiogenesis in tumors. The present study aimed to investigate the effects of miR-218, as well as its host genes, Slit2 and Slit3, on oxygen-induced retinal neovascularization (RNV) and to explore the associated mechanisms of action. For this purpose, a mouse model of oxygen-induced retinopathy (OIR) was established. The expression levels of miR-218-1 and miR-218-2, as well as those of their host genes, Slit2 and Slit3, were determined by RT-qPCR. Fluorescein angiography was performed on the retinas of the mice with OIR, and RNV was quantified by H&E staining in order to evaluate the effect of pCDH-CMV-miR-218 intravitreal injection on RNV in the mouse model of OIR. Roundabout, axon guidance receptor, homolog 1 (Robo1) expression was detected in mouse retinal vascular endothelial cells expressing high or low levels of miR-218 and in retinal tissues from mice with OIR by western blot analysis. Cell migration was evaluated by a scratch wound assay. We noted that in the mice with OIR, the expression level of miR-218 was significantly downregulated. We also noted that Robo1 expression was suppressed by miR-218. Furthermore, in the mice with OIR, the expression level of miR-218 was significantly downregulated, and that of miR-218-1 and its host gene, Slit2, was concomitantly downregulated as well. The restoration of miR-218 inhibited retinal angiogenesis by targeting Robo1. Taken together, our findings suggest that the Slit2-miR-218-Robo1 axis contributes to the inhibition of retinal angiogenesis and that miR-218 may be a new therapeutic target for preventing RNV.

Effects of Slit3 silencing on the invasive ability of lung carcinoma A549 cells

Slit proteins function as chemorepellents in axon guidance and neuronal migration by binding to cognate Robo receptors. The Slit/Robo signaling pathway is also involved in the regulation of tumor cell metastasis. However, whether the Slit/Robo signaling pathway exerts prometastatic or antimetastasis functions remains controversial. To date, most of the research on Slit/Robo has focused on Slit2, and the effects of Slit3 on metastasis remain largely unknown. Based on the Oncomine database, overall expression of Slit3 is low in tumor tissues compared to its level in normal tissues. The underlying mechanism for slit3 silencing in tumor tissues is likely related to hypermethylation of the slit3 promoter. However, lung carcinomas appear to be an exception. Several studies have reported that the frequency of Slit3 methylation in lung cancers is far lower than the frequency of Slit2. In the present study, high Slit3 expression at the mRNA level, yet not at the protein level, was detected in lung adenocarcinoma A549 cells. The function of Slit3 in tumor migration and invasion was examined by silencing of Slit3 expression in A549 cells. Silencing of Slit3 promoted proliferation, migration and invasion of A549 cells and induced epithelial-mesenchymal transition by downregulation of E-cadherin and upregulation of vimentin. The inhibitory effects of Slit3 on tumor migration and invasion are likely related to matrix metalloproteinases (MMPs). Silencing of Slit3 in the A549 cells enhanced MMP2 and MMP9 expression. These results indicate that Slit3 is a potential tumor suppressor in lung adenocarcinoma.

Characterization of differentially expressed genes involved in pathways associated with gastric cancer

To explore the patterns of gene expression in gastric cancer, a total of 26 paired gastric cancer and noncancerous tissues from patients were enrolled for gene expression microarray analyses. Limma methods were applied to analyze the data, and genes were considered to be significantly differentially expressed if the False Discovery Rate (FDR) value was < 0.01, P-value was <0.01 and the fold change (FC) was >2. Subsequently, Gene Ontology (GO) categories were used to analyze the main functions of the differentially expressed genes. According to the Kyoto Encyclopedia of Genes and Genomes (KEGG) database, we found pathways significantly associated with the differential genes. Gene-Act network and co-expression network were built respectively based on the relationships among the genes, proteins and compounds in the database. 2371 mRNAs and 350 lncRNAs considered as significantly differentially expressed genes were selected for the further analysis. The GO categories, pathway analyses and the Gene-Act network showed a consistent result that up-regulated genes were responsible for tumorigenesis, migration, angiogenesis and microenvironment formation, while down-regulated genes were involved in metabolism. These results of this study provide some novel findings on coding RNAs, lncRNAs, pathways and the co-expression network in gastric cancer which will be useful to guide further investigation and target therapy for this disease.

Putative miRNAs for the diagnosis of dyslexia, dyspraxia, and specific language impairment

Disorders of human communication abilities can be classified into speech and language disorders. Speech disorders (e.g., dyspraxia) affect the sound generation and sequencing, while language disorders (e.g., dyslexia and specific language impairment, or SLI) are deficits in the encoding and decoding of language according to its rules (reading, spelling, grammar). The diagnosis of such disorders is often complicated, especially when a patient presents more than one disorder at the same time. The present review focuses on these challenges. We have combined data available from the literature with an in silico approach in an attempt to identify putative miRNAs that may have a key role in dyspraxia, dyslexia and SLI. We suggest the use of new miRNAs, which could have an important impact on the three diseases. Further, we relate those miRNAs to the axon guidance pathway and discuss possible interactions and the role of likely deregulated proteins. In addition, we describe potential differences in expressional deregulation and its role in the improvement of diagnosis. We encourage experimental investigations to test the data obtained in silico.