Modulation of endothelial cell morphogenesis in vitro by MMP-9 during glial-endothelial cell interactions

Early Abnormal Placentation and Evidence of Vascular Endothelial Growth Factor System Dysregulation at the Feto-Maternal Interface After Periconceptional Alcohol Consumption

Adequate placentation, placental tissue remodeling and vascularization is essential for the success of gestation and optimal fetal growth. Recently, it was suggested that abnormal placenta induced by maternal alcohol consumption may participate in fetal growth restriction and relevant clinical manifestations of the Fetal Alcohol Spectrum Disorders (FASD). Particularly, periconceptional alcohol consumption up to early gestation can alter placentation and angiogenesis that persists in pregnancy beyond the exposure period. Experimental evidence suggests that abnormal placenta following maternal alcohol intake is associated with insufficient vascularization and defective trophoblast development, growth and function in early gestation. Accumulated data indicate that impaired vascular endothelial growth factor (VEGF) system, including their downstream effectors, the nitric oxide (NO) and metalloproteinases (MMPs), is a pivotal spatio-temporal altered mechanism underlying the early placental vascular alterations induced by maternal alcohol consumption. In this review we propose that the periconceptional alcohol intake up to early organogenesis (first trimester) alters the VEGF-NO-MMPs system in trophoblastic-decidual tissues, generating imbalances in the trophoblastic proliferation/apoptosis, insufficient trophoblastic development, differentiation and migration, deficient labyrinthine vascularization, and uncompleted remodelation and transformation of decidual spiral arterioles. Consequently, abnormal placenta with insufficiency blood perfusion, vasoconstriction and reduced labyrinthine blood exchange can be generated. Herein, we review emerging knowledge of abnormal placenta linked to pregnancy complications and FASD produced by gestational alcohol ingestion and provide evidence of the early abnormal placental angiogenesis-vascularization and growth associated to decidual-trophoblastic dysregulation of VEGF system after periconceptional alcohol consumption up to mid-gestation, in a mouse model.

Comparative matrix metalloproteinase-2 and -9 expression and activity during endotheliochorial and hemochorial trophoblastic invasiveness

To establish a functional placenta, its development needs adequate trophoblastic invasiveness. The intricate and complex morphological and molecular aspects regulating trophoblastic invasion during endotheliochorial placentation of domestic carnivores and their similarities and differences with the hemochorial placenta are still poorly understood. During placentation processes, from the time of implantation, trophoblast cells invade the uterine endometrium where they achieve extensive degradation and remodeling of extracellular matrix components; in this process, matrix metalloproteinases (MMPs), particularly MMP-2 and 9, have an essential role in rebuilding, cell migration, and invasiveness. This review provides an overview of comparative trophoblast invasive events and the expression and activity of MMP-2 and 9 during endotheliochorial and hemochorial placentation, emphasizing dog and mouse placental models. Understanding of trophoblastic invasiveness in two models of placentation, the intermediately invasive domestic carnivore endotheliochorial placenta, and the more highly invasive mouse hemochorial placenta, contributes to deepen knowledge of the trophoblast invasive processes and their diverse and complex human placental alterations, such as preeclampsia.

Downregulation of uPA, uPAR and MMP-9 using small, interfering, hairpin RNA (siRNA) inhibits glioma cell invasion, angiogenesis and tumor growth

The diffuse, extensive infiltration of malignant gliomas into the surrounding normal brain is believed to rely on modification of the proteolysis of extracellular matrix components. Our previous results clearly demonstrate that uPA, uPAR and MMP-9 concentrations increase significantly during tumor progression and that tumor growth can be inhibited with antisense stable clones of these molecules. Because antisense-mediated gene silencing does not completely inhibit the translation of target mRNA and high concentrations of antisense molecules are required to achieve gene silencing, we used the RNAi approach to silence uPA, uPAR and MMP-9 in this study. We examined a cytomegalovirus (CMV) promoter-driven DNA-template approach to induce hairpin RNA (hpRNA)-triggered RNAi to inhibit uPA, uPAR and MMP-9 gene expression with a single construct. uPAR protein levels and enzymatic activity of uPA and MMP-9 were found to significantly decrease in cells transfected with a plasmid expressing hairpin siRNA for uPAR, uPA and MMP-9. pU(2)M-transfected SNB19 cells significantly decreased uPA, uPAR and MMP-9 expression compared to mock and EV/SV-transfected cells, determined by immunohistochemical analysis. Furthermore, the effect of the single constructs for these molecules was a specific inhibition of their respective protein levels, as demonstrated by immunohistochemical analysis. After transfection with a plasmid vector expressing dsRNA for uPA, uPAR and MMP-9, glioma-cell invasion was retarded compared with mock and EV/SV-treated groups, demonstrated by Matrigel-invasion assay and spheroid-invasion assay. Downregulation of uPA, uPAR and MMP-9 using RNAi inhibited angiogenesis in an in vitro (co-culture) model. Direct intratumoral injections of plasmid DNA expressing hpRNA for uPA, uPAR and MMP-9 significantly regressed pre-established intracranial tumors in nude mice. In addition, cells treated with RNAi for uPAR, uPA and MMP-9 showed reduced pERK levels compared with parental and EV/SV-treated SNB19 cells. Our results support the therapeutic potential of RNAi as a method for gene therapy in treating gliomas.

Differential effects of photofrin, 5-aminolevulinic acid and calphostin C on glioma cells

The invasive nature of malignant gliomas makes treatment by surgery alone extremely difficult. However, the preferential accumulation of photosensitisers in neoplastic tissues suggests photodynamic therapy (PDT) may be useful as an adjuvant therapy following tumour resection. In this study, the potential use of three different photosensitisers, namely Photofrin, 5-aminolevulinic acid (5-ALA) and calphostin C in the treatment of glioma was investigated. The uptake, cytotoxicity on U87 and GBM6840 glioma cell lines were determined by flow cytometry and MTT assay respectively. Their effect on glioma cell invasiveness was evaluated by (1) measuring the levels of matrix degradation enzymes matrix metalloproteinase (MMP)-2 and -9 using gelatin zymography, and (2) Matrigel invasion assay. The results showed that uptake of calphostin C reached saturation within 2 h, while Photofrin and 5-ALA induced protoporphyrin IX (PpIX) levels elevated steadily up to 24 h. Photocytotoxic effect on the two glioma cell lines was similar with LD50 at optimal uptake: 1 microg/mL Photofrin at 1.5 J/cm(2); 1 mM 5-ALA at 2 J/cm(2) and 100 nM calphostin C at 2 J/cm(2). The inhibition in cell proliferation after Photofrin treatment was similar for both cell lines, which correlated to more cells being arrested in the G0/G1 phase of the cell cycle (P<0.01). By contrast, U87 was more sensitive to calphostin C whereas GBM6840 was more susceptible to 5-ALA treatment. The ability of both cell lines to migrate through the Matrigel artificial basement membrane was significantly reduced after PDT (P<0.001). This might be due to a decreased production in MMP-2 and MMP-9, together with the reduction of adhesion molecule expression. Photofrin was most superior in inhibiting cell invasion and calphostin C was least effective in reducing adhesion molecule expression. Taken together, PDT could be useful in the treatment of gliomas but the choice of photosensitisers must be taken into consideration.

High efficiency transfection of glioma cell lines and primary cells for overexpression and RNAi experiments

In order to investigate the impact of signalling proteins on the phenotype and malignant behavior of glioblastoma cells, we optimized the transfection procedure of human glioblastoma cell lines U251, U373, GaMG and of primary cells obtained from a patient's tumor using nucleofection technology in conjunction with plasmid pmaxGFP. We describe the optimization procedure, show that a high percentage of the cells can be transfected and that nucleofection does not cause phenotypic alterations of the cells. Therefore, we conclude that nucleofection is a highly efficient tool to deliver plasmids for transient protein overexpression and siRNA for specific protein knock-down to different glioblastoma cell lines or primary cells.

Proteases and glioma angiogenesis

Angiogenesis, the process by which new branches sprout from existing vessels, requires the degradation of the vascular basement membrane and remodeling of the ECM in order to allow endothelial cells to migrate and invade into the surrounding tissues. Serine, metallo, and cysteine proteinases are 3 types of a family of enzymes that proteolytically degrade various components of extracellular matrix. These proteases release various growth factors and also increase adhesive molecules and signaling pathway molecules upon their activation, which plays a significant role in angiogenesis. Downregulation of these molecules by antisense/siRNA or synthetic inhibitors decreases the levels of these molecules, inhibits the release of growth factors, and decreases the levels of various signaling pathway molecules, thereby leading to the inhibition of angiogenesis. Furthermore, MMPs degrade specific substrates and release angiogenic inhibitors which inhibit angiogenesis. Downregulation of 2 molecules, such as uPA and uPAR, uPAR and MMP-9, or Cathepsin B and MMP-9, are more effective to inhibit angiogenesis rather than downregulation of single molecules. However, careful testing of these combinations are most important because multiple effects of these combinations play a significant role in angiogenesis.

Fibroblast heterogeneity in collagenolytic response to colchicine

Matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMPs) are important in various physiological and pathological conditions, including those that involve homeostasis of collagen. Drug induced regulation of MMP-1, other MMPs and TIMPs is critical in treatment of various diseases, e.g. the use of the plant alkaloid, colchicine. One possible factor that might explain the failure in colchicine-treatment of some patients is interindividual variability on the cellular level. To investigate the possible individual heterogeneity in response to colchicine, we studied the effect of colchicine-induced synthesis of collagenase from 32 different human skin fibroblast strains derived from both healthy individuals as well as individuals with different skin diseases. We showed that colchicine induced an increased synthesis of collagenase in 22 of 32 cases. This heterogeneity occurred in fibroblasts from healthy as well as diseased individuals. To determine if colchicine also affected the fibroblast synthesis of gelatinase, stromelysin and tissue inhibitors of MMPs, we investigated several individuals from a single family. The results showed that both colchicine responsive and non-responsive fibroblasts with respect to collagenase synthesis responded to colchicine by an increased stromelysin synthesis, while the synthesis of gelatinase and TIMP-1 were unaffected. As a whole, our results indicate that individual heterogeneity in collagenase response to colchicine treatment may partly explain some of the controversial results obtained with colchicine as a drug.

The neurotrophin receptor TrkB cooperates with c-Met in enhancing neuroblastoma invasiveness

Neuroblastoma is the most frequent extracranial solid malignancy of childhood with a high mortality in advanced tumour stages. The hallmark of neuroblastoma is its clinical and biological heterogeneity. The molecular mechanisms leading to favourable or unfavourable tumour behaviour are still speculative. However, amplification of the oncogene MYCN and expression of the neurotrophin receptor TrkB are known to contribute to a highly malignant phenotype. To define the mechanisms through which TrkB may mediate neuroblastoma progression, we stably expressed this receptor in the neuroblastoma cell lines SH-SY5Y and SK-N-AS. The transfectants, but not the controls, had an increased invasive potency both, in vitro and in vivo, as demonstrated by Matrigel-invasion and chorioallantoic membrane assays, respectively. The retinoic acid-induced TrkB expression in parental SH-SY5Y cells was also associated with enhanced cell invasiveness. The TrkB mediated invasiveness involved the upregulation of the hepatocyte growth factor (HGF) and its receptor c-Met, resulting in an autocrine loop. Inhibition of HGF activity by anti-HGF neutralizing antibodies or disabling the function of c-Met by small interfering RNA suppressed the TrkB-induced invasiveness. The enhanced TrkB expression was associated with a significant increase in the secretion of various matrix-degrading proteases. Immunostaining and real-time RT-PCR analysis of tumour specimens demonstrated coordinated expression of TrkB and HGF/c-Met in experimental and primary neuroblastomas. We conclude that TrkB expression in neuroblastoma cells results in an increase in their invasive capability via upregulated expression of HGF/c-Met and enhanced activity of proteolytic networks.

Uveal Melanocytes Produce Matrix Metalloproteinases-2 and -9 In Vitro

The purpose of the present study was to investigate the expression of matrix metalloproteinase (MMP)-2 and MMP-9 by cultured human uveal melanocytes, and to test the effects of 12-O-tetradecanoyl-phorbol-13-acetate on the expression of these MMPs. Gelatin zymography of conditioned culture medium from four cultures of human uveal melanocytes (two cultures of iridal melanocytes and two cultures of choroidal melanocytes) detected MMP-2 (72 kDa) and a relatively small amount of MMP-9 (92 kDa), both in the latent form. RT-PCR analysis revealed the MMP-2 mRNA and MMP-9 mRNA in cultured uveal melanocytes. Addition of 12-O-tetradecanoyl-phorbol-13-acetate (10 ng/ml) to the culture medium caused an increase of production of MMP-2 and MMP-9 by cultured uveal melanocytes, and also stimulated the transcription of MMP-2 and MMP-9 of these cells.

Involvement of metalloprotease-2 in the development of human brain microvessels

The involvement of the metalloprotease-2 (MMP-2) in vessel development was investigated in the human telencephalon by double immunoreactions with antibodies to the enzyme, latent (proMMP-2) and active (aMMP-2) forms, and an antibody against collagen type IV, a constitutive component of the extracellular matrix (ECM) of the vessel basal lamina. MMP-2 is expressed in both 12- and 18-week telencephalic vessels, the proenzyme being mainly localised in endothelial cells and the active form prevailing in alpha-actin-reactive periendothelial cells identified as pericytes. Endothelial cells intensely positive for aMMP-2 were revealed in some microvessels and appeared locally associated with discontinuities of the collagen basal lamina. No detectable expression of MMP-2 was observed in perivascular glial processes revealed by vimentin/glial fibrillary acidic protein immunostainings. Double immunoreactions performed to further investigate telencephalon angiogenesis have demonstrated that both the endothelial cells and pericytes strongly express vascular endothelial growth factor (VEGF). Taken together, the results indicate that MMP-2 is largely involved in human brain angiogenesis and suggest that endothelial cells and pericytes tightly interplay in both angiogenesis mechanisms, by ECM proteolysis, and angiogenesis regulation, by local (autocrine/juxtacrine) VEGF action.

Inhibition of cathepsin B and MMP-9 gene expression in glioblastoma cell line via RNA interference reduces tumor cell invasion, tumor growth and angiogenesis

Extracellular proteases have been shown to cooperatively influence matrix degradation and tumor cell invasion through proteolytic cascades, with individual proteases having distinct roles in tumor growth, invasion, migration and angiogenesis. Matrix metalloproteases (MMP)-9 and cathepsin B have been shown to participate in the processes of tumor growth, vascularization and invasion of gliomas. In the present study, we used a cytomegalovirus promoter-driven DNA template approach to induce hairpin RNA (hpRNA)-triggered RNA interference (RNAi) to block MMP-9 and cathepsin B gene expression with a single construct. Transfection of a plasmid vector-expressing double-stranded RNA (dsRNA) for MMP-9 and cathepsin B significantly inhibited MMP-9 and cathepsin B expression and reduced the invasive behavior of SNB19, glioblastoma cell line in Matrigel and spheroid invasion models. Downregulation of MMP-9 and cathepsin B using RNAi in SNB19 cells reduced cell-cell interaction of human microvascular endothelial cells, resulting in the disruption of capillary network formation in both in vitro and in vivo models. Direct intratumoral injections of plasmid DNA expressing hpRNA for MMP-9 and cathepsin B significantly inhibited established glioma tumor growth and invasion in intracranial tumors in vivo. Further intraperitoneal (i.p.) injections of plasmid DNA expressing hpRNA for MMP-9 and cathepsin B completely regressed pre-established tumors for a long time (4 months) without any indication of these tumor cells. For the first time, these observations demonstrate that the simultaneous RNAi-mediated targeting of MMP-9 and cathepsin B has potential application for the treatment of human gliomas.

Adenovirus-Mediated Expression of Antisense Urokinase Plasminogen Activator Receptor and Antisense Cathepsin B Inhibits Tumor Growth, Invasion, and Angiogenesis in Gliomas

We have shown previously that urokinase plasminogen activator receptor (uPAR) and cathepsin B are overexpressed during glioma progression, particularly at the leading edge of the tumor. In the present study, we simultaneously down-regulated uPAR and cathepsin B in SNB19 glioma cell monolayer or SNB19 spheroids using an adenoviral vector carrying antisense uPAR and antisense cathepsin B and a combination of these genes as determined by Western blot analysis. The Ad-uPAR-Cath B-infected cells revealed a marked reduction in tumor growth and invasiveness as compared with the parental and vector controls. In vitro and in vivo angiogenic assays demonstrated inhibition of capillary-like structure formation and microvessel formation after Ad-uPAR-Cath B infection of SNB19 cells when compared with Ad-cytomegalovirus (CMV)-infected or mock-infected controls. Furthermore, using a near infrared fluorescence probe, in vivo imaging for cathepsin B indicated low/undetectable levels of fluorescence after injection of the Ad-uPAR-Cath B construct into pre-established s.c. tumors as compared with Ad-CMV-treated and untreated tumors. The effect with bicistronic construct (Ad-uPAR-Cath B) was much higher than with single (Ad-uPAR/Ad-Cath B) constructs. These results indicate that the down-regulation of cathepsin B and uPAR plays a significant role in inhibiting tumor growth, invasion, and angiogenesis. Hence, the targeting of these two proteases may be a potential therapy for brain tumors and other cancers.

Blockade of cathepsin B expression in human glioblastoma cells is associated with suppression of angiogenesis

The cysteine proteinase cathepsin B has been implicated in tumor progression by virtue of its increased mRNA and protein levels, as well as its localization at the invading front of the tumor. In this study, we examined whether blocking cathepsin B expression in human glioblastoma SNB19 cells affects angiogenesis. Stable transfectants of human glioblastoma cells with a plasmid containing antisense cathepsin B cDNA showed decreased migration rates in wound- and spheroid-migration assays. Analysis showed a reduction in VEGF protein and MMP-9 activity in the cathepsin B antisense cDNA-transfected cells. Regarding angiogenesis in vitro, we found that the conditioned medium of glioblastoma cells with downregulated cathepsin B expression reduced cell-cell interaction of human microvascular endothelial cells, resulting in the disruption of capillary-like network formation. Furthermore, a marked reduction in microvasculature development was seen in an in vivo dorsal air sac assay of glioblastoma cells with downregulated cathepsin B expression. Taken together, these results provide evidence that inhibition of cathepsin B expression can suppress glioblastoma-induced neovascularization.

Stromal Matrix Metalloproteinase-9 Regulates the Vascular Architecture in Neuroblastoma by Promoting Pericyte Recruitment

Advanced stages of neuroblastoma show increased expression of matrix metalloproteinases MMP-2 and MMP-9, that have been implicated in many steps of tumor progression, suggesting that they play a contributory role. Using pharmacological and genetic approaches, we have examined the role of these MMPs in progression of SK-N-BE (2).10 human neuroblastoma tumors orthotopically xenotransplanted into immunodeficient mice. Mice treated with Prinomastat, a synthetic inhibitor of MMPs, showed an inhibition of tumor cell proliferation in implanted tumors and a prolonged survival (50 versus 39 days in control group, P < 0.035). Treatment with Prinomastat did not affect formation of liver metastases (P = 0.52) but inhibited intravascular colonization by the tumor cells in the lung by 73.8% (P = 0.03) and angiogenesis in both primary tumors and experimental liver metastases. The primary tumors from Prinomastat-treated mice showed a 39.3% reduction in endothelial area detected by PECAM/CD31 staining in tumor sections (P < 0.001), primarily due to the presence of smaller vessels (P = 0.004). MMP-2 is expressed by neuroblastoma tumor cells and stromal cells, whereas MMP-9 is exclusively expressed by stromal cells, particularly vascular cells. To examine the contribution of MMP-9 to tumor angiogenesis, we generated RAG1/MMP-9 double-deficient mice. We observed a significant inhibition of angiogenesis in the immunodeficient RAG1/MMP-9 double-deficient mice orthotopically implanted with tumor cells (P = 0.043) or implanted s.c. with a mixture of tumor cells and Matrigel (P < 0.001). Using an FITC-labeled lectin, we demonstrated an inhibition in the architecture of the tumor vasculature in MMP-9-deficient mice, resulting in fewer and smaller blood vessels. These changes were associated with a 48% decrease in pericytes present along microvessels. Taken together, the data demonstrate that in neuroblastoma, stromally derived MMP-9 contributes to angiogenesis by promoting blood vessel morphogenesis and pericyte recruitment.

Molecular mechanisms of glioma invasiveness: the role of proteases

The invasive nature of brain-tumour cells makes an important contribution to the ineffectiveness of current treatment modalities, as the remaining tumour cells inevitably infiltrate the surrounding normal brain tissue, which leads to tumour recurrence. Such local invasion remains an important cause of mortality and underscores the need to understand in more detail the mechanisms of tumour invasiveness. Several proteases influence the malignant characteristics of gliomas--could their inhibition prove to be a useful therapeutic strategy?