The RNA-binding protein Musashi-1 (MSI1) exerts essential roles in multiple cellular functions, such as maintenance of self-renewal and pluripotency of stem cells. MSI1 overexpression has been observed in several tumor tissues, including glioblastoma (GBM), and is considered as a well-established marker for tumor metastasis and recurrence. However, the molecular mechanisms by which MSI1 regulates cell migration are still undetermined. Here we reported that MSI1 alters cell morphology, promotes cell migration, and increases viscoelasticity of GBM cells. We also found that MSI1 directly binds to the 3′UTR of Tensin 3 (TNS3) mRNA, a negative regulator of cell migration, to inhibit its translation. Additionally, we identified that RhoA-GTP could be a potential regulator in MSI1/TNS3-mediated cell migration and morphological changes. In a xenograft animal model, high expression ratio of MSI1 to TNS3 enhanced GBM tumor migration. We also confirmed that MSI1 and TNS3 expressions are mutually exclusive in migratory tumor lesions, and GBM patients with MSI1high/TNS3low pattern tend to have poor clinical outcome. Taken together, our findings suggested a critical role of MSI1-TNS3 axis in regulating GBM migration and highlighted that the ratio of MSI1/TNS3 could predict metastatic and survival outcome of GBM patients.

BackgroundOveractivated microglia that cluster at neuritic plaques constantly release neurotoxins, which actively contribute to progressive neurodegeneration in Alzheimer's disease (AD). Therefore, attenuating microglial clustering can reduce focal neuroinflammation at neuritic plaques. Previously, we identified CCL5 and CCL2 as prominent chemokines that mediate the chemotaxis of microglia toward beta-amyloid (Aβ)aggregates. Although transforming growth factor-β1 (TGF-β1) has been shown to down-regulate the expression of chemokines in activated microglia, whether TGF-β1 can reduce the chemotaxis of microglia toward neuritic plaques in AD remains unclear.MethodsIn the present study, we investigated the effects of TGF-β1 on Aβ-induced chemotactic migration of BV-2 microglia using time-lapse recording, transwell assay, real-time PCR, ELISA, and western blotting.ResultsThe cell tracing results suggest that the morphological characteristics and migratory patterns of BV-2 microglia resemble those of microglia in slice cultures. Using this model system, we discovered that TGF-β1 reduces Aβ-induced BV-2 microglial clustering in a dose-dependent manner. Chemotactic migration of these microglial cells toward Aβ aggregates was significantly attenuated by TGF-β1. However, these microglia remained actively moving without any reduction in migration speed. Pharmacological blockade of TGF-β1 receptor I (ALK5) by SB431542 treatment reduced the inhibitory effects of TGF-β1 on Aβ-induced BV-2 microglial clustering, while preventing TGF-β1-mediated cellular events, including SMAD2 phosphorylation and CCL5 down-regulation.ConclusionsOur results suggest that TGF-β1 reduces Aβ-induced microglial chemotaxis via the SMAD2 pathway. The down-regulation of CCL5 by TGF-β1 at least partially contributes to the clustering of microglia at Aβ aggregates. The attenuating effects of SB431542 upon TGF-β1-suppressed microglial clustering may be mediated by restoration of CCL5 to normal levels. TGF-β1 may ameliorate microglia-mediated neuroinflammation in AD by preventing activated microglial clustering at neuritic plaques.

Mesenchymal stem cells (MSC) are strongly associated with tumor progression and have been used as novel cell-based agents to deliver anticancer drugs to tumors. However, controversies about the direct involvement of MSCs in tumor progression suggest that MSCs mediate tumor progression in a cancer type-dependent manner. In this report, we analyzed the functional interactions between human MSCs and lung adenocarcinoma (LAC) cells to determine the therapeutic potential of MSCs in lung cancer. We showed that MSCs effectively inhibited the migration, invasion, and cell-cycle progression of several LAC cell lines. MSCs also enhanced the mesenchymalepithelial transition (MET) pathway, as evidenced by the reduction of several epithelial-mesenchymal transitionrelated markers in LAC cells cocultured with MSCs or in MSC-conditioned medium (MSC-CM). By cytokine array analysis, we determined that Oncostatin M (OSM), a differentiation-promoting cytokine, was elevated in the MSC-CM derived from primary MSC cultures. Furthermore, OSM treatment had the same effects as MSC-CM on LAC, whereas neutralizing antibodies to OSM reversed them. Notably, short hairpin RNAs against STAT1, an important downstream target of OSM, hindered the OSM-dependent induction of MET. In vivo xenograft tumor studies indicated that OSM inhibited tumor formation and metastasis of LAC cells, whereas neutralizing OSM in the MSC-CM hampered its inhibitory effects. In conclusion, this study showed that OSM is a paracrine mediator of MSC-dependent inhibition of tumorigenicity and activation of MET in LAC cells. These effects of OSM may serve as a basis for the development of new drugs and therapeutic interventions targeting cancer cells. Cancer Res; 72(22); 6051-64. Ó2012 AACR.