A chemorepellent inhibits local Ras activation to inhibit pseudopod formation to bias cell movement away from the chemorepellent.

The ability of cells to sense chemical gradients is essential during development, morphogenesis, and immune responses. Although much is known about chemoattraction, chemorepulsion remains poorly understood. Proliferating Dictyostelium cells secrete a chemorepellent protein called AprA. AprA prevents pseudopod formation at the region of the cell closest to the source of AprA, causing the random movement of cells to be biased away from the AprA. Activation of Ras proteins in a localized sector of a cell cortex helps to induce pseudopod formation, and Ras proteins are needed for AprA chemorepulsion. Here we show that AprA locally inhibits Ras cortical activation through the G protein-coupled receptor GrlH, the G protein subunits Gß and Gα8, Ras protein RasG, protein kinase B, the p21-activated kinase PakD, and the extracellular signal-regulated kinase Erk1. Diffusion calculations and experiments indicate that in a colony of cells, high extracellular concentrations of AprA in the center can globally inhibit Ras activation, while a gradient of AprA that naturally forms at the edge of the colony allows cells to activate Ras at sectors of the cell other than the sector of the cell closest to the center of the colony, effectively inducing both repulsion from the colony and cell differentiation. Together, these results suggest that a pathway that inhibits local Ras activation can mediate chemorepulsion.

Sputum from chronic obstructive pulmonary disease patients inhibits T cell migration in a microfluidic device.

Chronic obstructive pulmonary disease (COPD) is a common lung disease characterized by narrowed airways, resulting in serious breathing difficulty. Previous studies have demonstrated that inflammatory infiltration of leukocytes in the airway is associated with the pathogenesis of COPD. In the present study, we employed a microfluidic approach to assess the effect of COPD sputum on activated human peripheral blood T cell migration and chemotaxis under well-controlled gradient conditions. Our results showed considerable basal migration of T cells derived from peripheral blood of COPD patients and healthy controls in the medium control groups. By contrast, the migration of T cells from COPD patients and healthy controls was significantly inhibited in the presence of a gradient of sputum supernatant from COPD patients. Furthermore, chemotaxis of T cells from COPD patients or healthy subjects toward an SDF-1α gradient was clearly inhibited by sputum samples from the COPD patients. The inhibition effect revealed by the microfluidic cell migration experiments provides new information about the complex involvement of T cell trafficking in COPD.

CML/CD36 accelerates atherosclerotic progression via inhibiting foam cell migration.

Among the various complications of type 2 diabetes mellitus, atherosclerosis causes the highest disability and morbidity. A multitude of macrophage-derived foam cells are retained in atherosclerotic plaques resulting not only from recruitment of monocytes into lesions but also from a reduced rate of macrophage migration from lesions. Nε-carboxymethyl-Lysine (CML), an advanced glycation end product, is responsible for most complications of diabetes. This study was designed to investigate the mechanism of CML/CD36 accelerating atherosclerotic progression via inhibiting foam cell migration. In vivo study and in vitro study were performed. For the in vivo investigation, CML/CD36 accelerated atherosclerotic progression via promoting the accumulation of macrophage-derived foam cells in aorta and inhibited macrophage-derived foam cells in aorta migrating to the para-aorta lymph node of diabetic apoE-/- mice. For the in vitro investigation, CML/CD36 inhibited RAW264.7-derived foam cell migration through NOX-derived ROS, FAK phosphorylation, Arp2/3 complex activation and F-actin polymerization. Thus, we concluded that CML/CD36 inhibited foam cells of plaque migrating to para-aorta lymph nodes, accelerating atherosclerotic progression. The corresponding mechanism may be via free cholesterol, ROS generation, p-FAK, Arp2/3, F-actin polymerization.

Dual roles of calpain in facilitating Coxsackievirus B3 replication and prompting inflammation in acute myocarditis.

BACKGROUND: Viral myocarditis (VMC) treatment has long been lacking of effective methods. Our former studies indicated roles of calpain in VMC pathogenesis. This study aimed at verifying the potential of calpain in Coxsackievirus B3 (CVB3)-induced myocarditis treatment. METHODS: A transgenic mouse overexpressing the endogenous calpain inhibitor, calpastatin, was introduced in the study. VMC mouse model was established via intraperitoneal injection of CVB3 in transgenic and wild mouse respectively. Myocardial injury was assayed histologically (HE staining and pathology grading) and serologically (myocardial damage markers of CK-MB and cTnI). CVB3 replication was observed in vivo and in vitro via the capsid protein VP1 detection or virus titration. Inflammation/fibrotic factors of MPO, perforin, IFNγ, IL17, Smad3 and MMP2 were evaluated using western blot or immunohistology stain. Role of calpain in regulating fibroblast migration was studied in scratch assays. RESULTS: Calpastatin overexpression ameliorated myocardial injury induced by CVB3 infection significantly in transgenic mouse indicated by reduced peripheral CK-MB and cTnI levels and improved histology injury. Comparing with CVB3-infected wild type mouse, the transgenic mouse heart tissue carried lower virus load. The inflammation factors of MPO, perforin, IFNγ and IL17 were down-regulated accompanied with fibrotic agents of Smad3 and MMP2 inhibition. And calpain participated in the migration of fibroblasts in vitro, which further proves its role in regulating fibrosis. CONCLUSION: Calpain plays dual roles of facilitating CVB3 replication and inflammation promotion. Calpain inhibition in CVB3-induced myocarditis showed significant treatment effect. Calpain might be a novel target for VMC treatment in clinical practices.

Inhibition of α-smooth muscle actin expression and migration of pterygium fibroblasts by coculture with amniotic mesenchymal stem cells.

PURPOSE: Epithelial-mesenchymal transition (EMT) of normal conjunctival tissues is a major reason of pterygium generation; α-smooth muscle actin (α-SMA) is a maker in EMT. In this study, we investigated if human amniotic mesenchymal stem cells (hAMSCs) can inhibit α-SMA expression and migration of human pterygium fibroblasts (hPFs) in vitro. MATERIALS AND METHODS: Coculture of hAMSCs and hPFs was completed by using a Transwell coculture system. The α-SMA expression of hPFs was detected by immunocytochemistry and western blot analysis. The migration ability of hPFs was measured by means of a migration assay. Immunoreactivity for α-SMA was detected in all pterygium fibroblasts examined. RESULTS: The expression of α-SMA in cocultured hPFs was significantly lower than in hPFs. Similar result was demonstrated in western blot analysis. In addition, migration assay showed that hAMSCs reduce the migration of hPFs. CONCLUSIONS: These results suggested that hAMSCs have the potential to inhibit the generation and invasiveness of pterygium in vitro.

Tactile interactions lead to coherent motion and enhanced chemotaxis of migrating cells.

When motile cells come into contact with one another their motion is often considerably altered. In a process termed contact inhibition of locomotion (CIL) cells reshape and redirect their movement as a result of cell-cell contact. Here we describe a mathematical model that demonstrates that CIL alone is sufficient to produce coherent, collective cell migration. Our model illustrates a possible mechanism behind collective cell migration that is observed, for example, in neural crest cells during development, and in metastasizing cancer cells. We analyse the effects of varying cell density and shape on the alignment patterns produced and the transition to coherent motion. Finally, we demonstrate that this process may have important functional consequences by enhancing the accuracy and robustness of the chemotactic response, and factors such as cell shape and cell density are more significant determinants of migration accuracy than the individual capacity to detect environmental gradients.

Matrine inhibits the adhesion and migration of BCG823 gastric cancer cells by affecting the structure and function of the vasodilator-stimulated phosphoprotein (VASP).

AIM: Vasodilator-stimulated phosphoprotein (VASP) expression is upregulated in human cancers and correlates with more invasive advanced tumor stages. The aim of this study was to elucidate the mechanisms by which matrine, an alkaloid derived from Sophora species plants, acted on the VASP protein in human gastric cancer cells in vitro. METHODS: VASP was expressed and purified. Intrinsic fluorescence spectroscopy was used to study the binding of matrine to VASP. CD spectroscopy was used to examine the changes in the VASP protein secondary structure. Human gastric carcinoma cell line BGC823 was tested. Scratch wound and cell adhesion assays were used to detect the cell migration and adhesion, respectively. Real-time PCR and Western blotting assays were used to measure mRNA and protein expression of VASP. RESULTS: In the fluorescence assay, the dissociation constant for binding of matrine to VASP protein was 0.86 mmol/L, thus the direct binding between the two molecules was weak. However, matrine (50 µg/mL) caused obvious change in the secondary structure of VASP protein shown in CD spectrum. Treatments of BGC823 cells with matrine (50 µg/mL) significantly inhibited the cell migration and adhesion. The alkaloid changed the subcellular distribution of VASP and formation of actin stress fibers in BGC823 cells. The alkaloid caused small but statistically significant decreases in VASP protein expression and phosphorylation, but had no significant effect on VASP mRNA expression. CONCLUSION: Matrine modulates the structure, subcellular distribution, expression and phosphorylation of VASP in human gastric cancer cells, thus inhibiting the cancer cell adhesion and migration.

Exogenous SPARC suppresses proliferation and migration of prostate cancer by interacting with integrin ß1.

BACKGROUND: The matricellular protein secreted protein acidic and rich in cysteine (SPARC) plays an important role on tumor metastasis and progression in several cancers. However, the roles of SPARC in prostate cancer (PCa) remain unclear. METHODS: To identify SPARC protein in prostate tissue, immunohistochemical analysis of SPARC was conducted using human prostate tissue microarray. To detect SPARC expression in prostate cancer (LNCaP, DU145, and PC-3) and stromal cells, RT-PCR, western blot analysis, and ELISA was conducted. To reveal the function of exogenous SPARC in PCa cells, AKT phosphorylation was confirmed by western blot analysis after coculture with stromal cells. Proliferation and migration of PCa cells were examined by addition of SPARC. The interaction between SPARC and integrin ß1 was confirmed by western blot analysis after immunoprecipitation. RESULTS: SPARC protein was expressed well in normal tissue compared with PCa tissue. ELISA showed high secreted SPARC protein in normal prostate-derived stromal cell (PrSC) compared with PCa-derived stromal cell (PCaSC) and PCa. PCa cells cocultured with PrSC showed reduced AKT phosphorylation more than with PCaSC. PCa cells cocultured with PrSC whose SPARC was knocked-down restored AKT phosphorylation. Moreover, PCa cells treated with SPARC led to reduced AKT phosphorylation. Immunoprecipitation with SPARC revealed interaction of SPARC and integrin ß1 in PCa cells. Inhibited proliferation and migration of PCa cells by SPARC was restored by integrin ß1 neutralizing antibody. CONCLUSIONS: Reduced SPARC secretion from stromal cells might affect PCa progression mediating through limiting AKT phosphorylation after interaction with integrin ß1.

Repulsive migration of Schwann cells induced by Slit-2 through Ca2+-dependent RhoA-myosin signaling.

Schwann cells migrate along axons before initiating myelination during development and their migration facilitates peripheral nerve regeneration after injury. Axon guidance molecule Slit-2 is highly expressed during peripheral development and nerve regeneration; however, whether Slit-2 regulates the migration of Schwann cells remains a mystery. Here we show that Slit-2 receptor Robo-1 and Robo-2 were highly expressed in Schwann cells in vitro and in vivo. Using three distinct migration assays, we found that Slit-2 repelled the migration of cultured Schwann cells. Furthermore, frontal application of a Slit-2 gradient to migrating Schwann cells first caused the collapse of leading front, and then reversed soma translocation of Schwann cells. The repulsive effects of Slit-2 on Schwann cell migration depended on a Ca(2+) signaling release from internal stores. Interestingly, in response to Slit-2 stimulation, the collapse of leading front required the loss of F-actin and focal adhesion, whereas the subsequent reversal of soma translocation depended on RhoA-Rock-Myosin signaling pathways. Taken together, we demonstrate that Slit-2 repels the migration of cultured Schwann cells through RhoA-Myosin signaling pathways in a Ca(2+)-dependent manner.

CXCR6 deficiency ameliorated myocardial ischemia/reperfusion injury by inhibiting infiltration of monocytes and IFN-γ-dependent autophagy.

BACKGROUND: Emerging evidence shows that the chemokine CXCL16 plays an important role in the pathogenesis of myocardial remodeling and development of heart failure following ischemia/reperfusion (I/R) injury. CXCR6, the receptor for CXCL16, is also critically involved. However, the underlying mechanism remained uncertain, and the aim of this research was to investigate this mechanism in CXCR6 knockout (KO) mice. METHODS AND RESULTS: CXCR6 KO mice and wild type (WT) mice had no overt phenotype at baseline in the absence of injury, but difference was shown in response to I/R induction. Compared with WT mice, CXCR6 KO mice exhibited a lower infarction size (31.86 ± 1.808% vs. 43.09 ± 1.519%), and better cardiac function (measured by LVEF, LVFS, +dp/dt, LVEDP, and LVSP) following I/R. Moreover, cardiac levels of IFN-γ and IFN-γ-dependent autophagy were found to be significantly attenuated in CXCR6 KO mice. Further data showed that cardiac-enhanced IFN-γ secretion was not induced by cardiomyocytes, but by infiltrated monocytes in the myocardium in response to I/R injury. In vivo injection of IFN-γ and in vitro co-cultured cardiomyocytes with CD11b+ monocytes confirmed IFN-γ activated autophagic response, and induced cardiac dysfunction in a paracrine manner. CONCLUSIONS: The study suggested that since disruption of the CXCL16/CXCR6 signaling cascade had a cardio-protective effect against I/R injury, the underlying mechanism might be that I/R triggered the infiltration of monocytes into the myocardium, and induced cardiac autophagy through CXCL16/CXCR6-dependent paracrine secretion of IFN-γ.

Beneficial effects of αB-crystallin in spinal cord contusion injury.

αB-crystallin is a member of the heat shock protein family that exerts cell protection under several stress-related conditions. Recent studies have revealed that αB-crystallin plays a beneficial role in a mouse model of multiple sclerosis, brain ischemia, and Alexander disease. Whether αB-crystallin plays a role in modulating the secondary damage after CNS trauma is not known. We report here that αB-crystallin mediates protective effects after spinal cord injury. The levels of αB-crystallin are reduced in spinal cord tissue following contusion lesion. In addition, administration of recombinant human αB-crystallin for the first week after contusion injury leads to sustained improvement in locomotor skills and amelioration of secondary tissue damage. We also provide evidence that recombinant human αB-crystallin modulates the inflammatory response in the injured spinal cord, leading to increased infiltration of granulocytes and reduced recruitment of inflammatory macrophages. Furthermore, the delivery of recombinant human αB-crystallin promotes greater locomotor recovery even when the treatment is initiated 6 h after spinal cord injury. Our findings suggest that administration of recombinant human αB-crystallin may be a good therapeutic approach for treating acute spinal cord injury, for which there is currently no effective treatment.

Emerging roles of endothelial cells in multiple sclerosis pathophysiology and therapy.

Although multiple sclerosis (MS) has traditionally been viewed and researched as an immune-mediated demyelinating and neurodegenerative disease of the human central nervous system (CNS), its highly complex pathogenesis clearly includes a significant vascular inflammatory component and many therapeutic approaches achieve benefit by direct or indirect effects on cerebrovascular endothelial cells. Cerebral endothelial cells create and separate the compartments of the peripheral circulation and CNS creating the blood-brain barrier (BBB), a selectively permeable boundary layer between these spaces. Interactions between activated leukocytes and cerebral endothelium play essential roles in mediating their trans-BBB diapedesis during normal immune surveillance and during pathogenesis of neuroinflammatory diseases like MS. Extravasation of activated and committed leukocytes from the peripheral circulation through the endothelial layer of the BBB into the CNS milieu is the most fundamental step in formation of MS lesions. During MS pathogenesis, once the activated leukocytes enter the CNS environment, they propagate a massive wave of destruction which culminates in the loss of both myelin/oligodendrocyte complex and neurodegeneration. Multiple clinical and basic scientific observations support endothelial cell 'stress' and apoptosis as a hallmark characteristic of MS. The manipulation of the endothelial biology aiming to block trans-endothelial migration of activated immune cells into the CNS is a potent form of treatment for MS achieving significant reductions in disease activity and new lesion formation. In particular, endothelial microparticles are now well-recognized as important biomarkers and mediators of this type of stress. In this review, we discuss recent findings and new advances in our knowledge regarding leukocyte migration through the endothelial frontier of the BBB and how this can be exploited toward treating MS patients.

CXCL1 regulation of oligodendrocyte progenitor cell migration is independent of calcium signaling.

Cell migration is an indispensable aspect of tissue patterning during embryonic development. Oligodendrocytes, the myelinating cells of the central nervous system, migrate significantly during development of the brain. Several growth factors have been identified as being critical regulators of oligodendrocyte progenitor migration, including platelet derived growth factor-A (PDGFA), and fibroblast growth factor-2 (FGF2). Further, the chemokine CXCL1 has been shown to play a critical role in regulating the dispersal of oligodendrocyte progenitors during development, although the mechanisms underlying this regulation are unknown. Previous studies have also shown that calcium flux is required for oligodendrocyte progenitor migration. CXCL1 induces calcium flux in cells; therefore, we hypothesized that CXCL1 inhibition of oligodendrocyte progenitor migration is regulated via changes in intracellular calcium flux. The current study shows that CXCL1 inhibition of oligodendrocyte progenitor migration is independent of calcium signaling. Further, we show that CXCL1 inhibition of oligodendrocyte progenitor migration is specific to PDGFA induced migration. Finally, we show that CXCL1 inhibition of oligodendrocyte progenitor migration is independent of activation of the cell cycle. Our results provide intriguing results relevant to specific aspects of patterning of white matter tracts in the central nervous system, and may further the understanding of tissue remodeling seen during disease-related processes.

Role of lipoxin A4 in the cell-to-cell interaction between all-trans retinoic acid-treated acute promyelocytic leukemic cells and alveolar macrophages.

Differentiation therapy with all-trans retinoic acid (ATRA) has been used successfully to treat acute promyelocytic leukemia (APL), but such treatment also causes differentiation syndrome (DS) by inducing APL cell infiltration into alveolar spaces. The mechanism underlying the clearance of infiltrated APL cells has not been investigated in detail. Lipoxin A(4) (LXA(4)) is an important anti-inflammatory mediator during the resolution of inflammation. In this study, the role of LXA(4) in the cell-cell interaction between alveolar macrophages (AMφ; NR8383 cells) and APL NB4 cells was investigated and found that conditioned medium (CM) harvested from ATRA-treated NR8383 (ATRA-NR8383) cells was able to induce the transmigration of ATRA-NB4 cells. However, the pro-migratory activity of CM was attenuated progressively when ATRA-NR8383 cells were co-cultured with increased cell dosages of apoptotic NB4 cells. A significantly higher amount of LXA(4) was released into the CM by ATRA-NR8383 cells when they were co-cultured with apoptotic ATRA-NB4 cells. Expression of a receptor for LXA(4) (ALX/FPR2) was enhanced in both ATRA-NB4 cells and ATRA-NR8383 cells. Exogenous LXA(4) treatment was able to inhibit the transmigration of ATRA-NB4 cells and induce the phagocytic clearance of apoptotic cells by ATRA-NR8383 cells. The anti-migratory activity of exogenous LXA(4) was attenuated by pre-treating ATRA-NB4 cells with an ALX/FPR2 inhibitor. We conclude that AMφ-derived LXA(4) plays an important role in the interaction between AMφ and APL cells and that this contributes to clearance of apoptotic APL cells.

Natalizumab and impedance of the homing of CD34+ hematopoietic progenitors.

BACKGROUND: Treatment with natalizumab, an antibody blocking the α4-integrin, is associated with increased numbers of circulating CD34+ cells in the peripheral blood of patients with multiple sclerosis. OBJECTIVE: To determine whether natalizumab mobilizes CD34+ cells from or inhibits homing to the bone marrow (BM). DESIGN: Fifty-two patients with relapsing-remitting multiple sclerosis treated with natalizumab were included. Flow cytometric analyses; polymerase chain reaction assays for JC (John Cunningham) virus DNA detection; and adhesion, migration, and apoptosis assays of immunomagnetically enriched peripheral blood and BM CD34+ cells were conducted. A comparison was made with CD34+ cells from granulocyte colony-stimulating factor-mobilized peripheral blood or steady-state BM of age- and sex-matched healthy donors. RESULTS: We found adhesion and migration of peripheral blood-derived CD34+ cells to be reduced. In BM aspirates from natalizumab-treated patients, the cellularity, the proportion, and the adhesive capacity of CD34+ cells were normal. The JC virus was undetectable. CONCLUSIONS: Natalizumab mediates an increase in circulating CD34+ cells by interfering with homing to the BM. Thus, CD34+ cells appear unlikely to represent a source mobilizing JC virus out of the BM in patients treated with natalizumab.

Baicalein inhibits the migration and invasive properties of human hepatoma cells.

Flavonoids have been demonstrated to exert health benefits in humans. We investigated whether the flavonoid baicalein would inhibit the adhesion, migration, invasion, and growth of human hepatoma cell lines, and we also investigated its mechanism of action. The separate effects of baicalein and baicalin on the viability of HA22T/VGH and SK-Hep1 cells were investigated for 24h. To evaluate their invasive properties, cells were incubated on matrigel-coated transwell membranes in the presence or absence of baicalein. We examined the effect of baicalein on the adhesion of cells, on the activation of matrix metalloproteinases (MMPs), protein kinase C (PKC), and p38 mitogen-activated protein kinase (MAPK), and on tumor growth in vivo. We observed that baicalein suppresses hepatoma cell growth by 55%, baicalein-treated cells showed lower levels of migration than untreated cells, and cell invasion was significantly reduced to 28%. Incubation of hepatoma cells with baicalein also significantly inhibited cell adhesion to matrigel, collagen I, and gelatin-coated substrate. Baicalein also decreased the gelatinolytic activities of the matrix metalloproteinases MMP-2, MMP-9, and uPA, decreased p50 and p65 nuclear translocation, and decreased phosphorylated I-kappa-B (IKB)-ß. In addition, baicalein reduced the phosphorylation levels of PKCα and p38 proteins, which regulate invasion in poorly differentiated hepatoma cells. Finally, when SK-Hep1 cells were grown as xenografts in nude mice, intraperitoneal (i.p.) injection of baicalein induced a significant dose-dependent decrease in tumor growth. These results demonstrate the anticancer properties of baicalein, which include the inhibition of adhesion, invasion, migration, and proliferation of human hepatoma cells in vivo.

Decorin and chondroitin-6 sulfate inhibit B16V melanoma cell migration and invasion by cellular acidification.

In vivo, cells are embedded in an environment generated and maintained by multiple cell-cell and cell-matrix interactions. While transiting the dermis metastasizing melanoma cells interact with the extracellular matrix (ECM) and fibroblasts. To study the roles of ECM components and fibroblasts in melanoma (B16V) cell migration and invasion, we established a co-culture system consisting of fibroblasts, their collagen-rich matrix and B16V cells. The crosstalk between B16V cells and fibroblasts was indicated by a clear increase in release and activity of matrix-metallo-protease-2. Time-lapse microscopy revealed that in B16V cells exposed to either decorin or chondroitin sulfates migration and invasion decreased by more than 50%. Decorin led to a reversible, chondroitin-6-sulfate to an irreversible, cytosolic acidification of B16V cells. Interestingly, decorin lowered NHE1 activity whereas chondroitin-6-sulfate did not. Furthermore, decorin and chondroitin-6-sulfate also acidified the pH at the cell surface which might prevent migration due to strong adhesion. In conclusion, the present co-culture system is an appropriate tool to analyze migration, invasion, and MMP release depending on cell-matrix interactions and the crosstalk between the invasive cells and those surrounded by their self-made matrix. We show a so far unknown function of decorin and chondroitin-6-sulfate: their ability to inhibit B16V cell migration by intracellular acidification.

MicroRNA-21 suppression impedes medulloblastoma cell migration.

Medulloblastoma (MB), the most common malignant brain tumour in children, is characterised by a high risk of leptomeningeal dissemination. But little is known about the molecular mechanisms that promote cancer cell migration in MB. Aberrant expression of miR-21 is recognised to be causatively linked to metastasis in a variety of human neoplasms including brain tumours; however its function in MB is still unknown. In this study we investigated the expression level and the role of miR-21 in MB cell migration. miR-21 was found to be up-regulated, compared to normal cerebellum, in 29/29 MB primary samples and 6/6 MB-derived cell lines. Inverse correlation was observed between miR-21 expression and the metastasis suppressor PDCD4, while miR-21 repression increased the release of PDCD4 protein, suggesting negative regulation of PDCD4 by miR-21 in MB cells. Anti-miR-21 decreased protein expression of the tumour cell invasion mediators MAP4K1 and JNK, which are also known to be negatively regulated by PDCD4, and down-regulated integrin protein that is essential for MB leptomeningeal dissemination. Moreover miR-21 knockdown in MB cells increased the expression of two eminent negative modulators of cancer cell migration, E-Cadherin and TIMP2 proteins that are known to be positively regulated by PDCD4. Finally and importantly, suppression of miR-21 decreased the motility of MB cells and reduced their migration across basement membranes in vitro. Together, these compelling data propose miR-21 pathway as a novel mechanism impacting MB cell dissemination and raises the possibility that curability of selected MB may be improved by pharmaceutical strategies directed towards microRNA-21.

Mouse MCP1 C-terminus inhibits human MCP1-induced chemotaxis and BBB compromise.

Compared to the rodent monocyte chemoattractant protein 1 (MCP1/CCL2), the human MCP1 lacks a C-terminal extension. Although the function of this C-extension is not entirely defined, in previous work we reported that it decreases the chemotactic properties of mouse MCP1. To determine if this function is specific to the rodent chemokine, or if the C-terminal extension has the ability to regulate chemotactic potency to MCP1 in general, we generated a chimeric protein consisting of human MCP1 fused to the mouse MCP1 C-terminal fragment. We found that mouse MCP1 C-terminus significantly decreased the chemotactic potency of human MCP1 and diminished the blood brain barrier compromise normally induced by the human protein. Not only did mouse MCP1 C-terminus inhibit human MCP1-induced Rac1 activation and formation of lamellipodia, it also disrupted the staining pattern of ZO-1 at cell-cell borders and prevented human MCP1-induced F-actin formation in brain microvascular endothelial cells. Additionally, the MCP1 C-terminus dramatically decreased human MCP1-induced activation of ERM proteins in endothelial cells. These findings confirm that the rodent C-terminal MCP1 extension acts as a rheostat for MCP1 functions and suggest that potentially in humans another protein or protein complex may assume a similar regulatory function.