Sushma L. Jasti

Downregulation of MMP-9 in ERK-mutated stable transfectants inhibits glioma invasion in vitro

We previously showed that enhanced expression of MMP-9, an endopeptidase that digests basement-membrane type IV collagen, is related to tumor progression in vitro and in vivo; antisense-MMP-9 stably transfected clones were less invasive than untransfected parental cells and did not form tumors in nude mice. In this study, we examined the role of ERK-1 in the regulation of MMP-9 production and the invasive behavior of the human glioblastoma cell line SNB19, in which ERK1 is constitutively activated. SNB19 cells were stably transfected with mt-ERK, a vector encoding ERK-1 cDNA in which the conserved lysine at codon 71 was changed to arginine, thus impairing the catalytic efficiency of this enzyme. Gelatin zymography showed reduced levels of MMP-9 in the mt-ERK-transfected cell lines relative to those in vector-transfected and parental control cells. Reductions in MMP-9 protein mRNA levels were also detected in the mt-ERK-transfected cells by Western and Northern blotting. The mt-ERK-transfected cells were much less invasive than parental or vector control cells in a Matrigel invasion assay and in a spheroid coculture assay. Thus an ERK-dependent signaling pathway seems to regulate MMP-9 mediated glioma invasion in SNB19 cells; interfering with this pathway could be developed into a therapeutic approach, which aims at a reduction of cancer cell invasion.

Adenovirus-mediated expression of antisense MMP-9 in glioma cells inhibits tumor growth and invasion

Matrix metalloproteinase 9 (MMP-9) is known to play a major role in cell migration and invasion in both physiological and pathological processes. Our previous work has shown that increased MMP-9 levels are associated with human glioma tumor progression. In this study, we evaluated the ability of an adenovirus containing a 528 bp cDNA sequence in antisense orientation to the 5′ end of the human MMP-9 gene (Ad-MMP-9AS) to inhibit the invasiveness and migratory capacity of the human glioblastoma cell line SBN19 in in vitro and in vivo models. Infection of glioma cells with Ad-MMP-9AS reduced MMP-9 enzyme activity by approximately 90% compared with mock- or Ad-CMV-infected cells. Migration and invasion of glioblastoma cells infected with Ad-MMP-9AS were significantly inhibited relative to Ad-CMV-infected controls in spheroid and Matrigel assays. Intracranial injections of SNB19 cells infected with Ad-MMP-9AS did not produce tumors in nude mice. However, injecting the Ad-MMP-9AS construct into subcutaneous U87MG tumors in nude mice caused regression of tumor growth. These results support the theory that adenoviral-mediated delivery of the MMP-9 gene in the antisense orientation has therapeutic potential for treating gliomas.

Mechanisms underlying PTEN regulation of vascular endothelial growth factor and angiogenesis

Inactivation of the tumor suppressor gene PTEN and overexpression of VEGF are two of the most common events observed in high‐grade malignant gliomas. The purpose of this study was to determine whether PTEN controls VEGF expression in gliomas under normoxic conditions. Transfer of PTEN to human glioma cells resulted in the transduction of a functional PTEN protein as evidenced by the upregulation of p27 and modification of the phosphorylation status of Akt. Under normoxic conditions, enzyme‐linked immunosorbent assay and Northern blot analyses showed downregulation of VEGF in PTEN‐treated cells. Moreover, conditioned media from PTEN‐treated glioma cells significantly diminished the ability of endothelial cells to grow and migrate. Western blot assays demonstrated that, in a normoxic environment, PTEN downregulates HIF‐1α. Finally, promoter activity assays showed that the VEGF promoter region containing the HIF‐1α binding site is necessary and sufficient for PTEN‐mediated downregulation of VEGF. Experiments with PI3‐K inhibitors and kinase assays suggested that PI3‐K is mediating the effect of PTEN on VEGF, and not the p42/p48 or p38 MAP kinases. These results indicate that restoration of PTEN function in gliomas may induce therapeutic effect by downregulating VEGF. Furthermore, this close functional relationship between PTEN and VEGF suggests that a better understanding of the transduction signal regulated by PTEN might enhance the knowledge of the cause and physiology of vascular and inflammatory diseases. Ann Neurol 2003

Down-regulation of cathepsin B expression impairs the invasive and tumorigenic potential of human glioblastoma cells

Increases in abundance of cathepsin B transcript and protein correlate with increases in tumor grade and alterations in subcellular localization and activity of cathepsin B. The enzyme is able to degrade the components of the extracellular matrix (ECM) and activate other proteases capable of degrading ECM. To investigate the role played by this protease in the invasion of brain tumor cells, we transfected SNB19 human glioblastoma cells with a plasmid containing cathepsin B cDNA in antisense orientation. Control cells were transfected with vector alone. Clones expressing antisense cathepsin B cDNA exhibited significant reductions in cathepsin B mRNA, enzyme activity and protein compared to controls. Matrigel Invasion assay showed that the antisense-transfected cells had a markedly diminished invasiveness compared with controls. When tumor spheroids containing antisense transfected SNB19 cells expressing reduced cathepsin B were co-cultured with fetal rat brain aggregates, invasion of fetal rat brain aggregates was significantly reduced. Green Fluorescent Protein (GFP) expressing parental cells and antisense transfectants were generated for detection in mouse brain tissue without any post-chemical treatment. Intracerebral injection of SNB19 stable antisense transfectants resulted in reduced tumor formation in nude mice. These results strongly support a role for cathepsin B in the invasiveness of human glioblastoma cells and suggest cathepsin B antisense may prove useful in cancer therapy.

Regulation of MMP-9 (type IV collagenase) production and invasiveness in gliomas by the extracellular signal-regulated kinase and jun amino-terminal kinase signaling cascades

Our previous studies have shown that MMP-9 levels are significantly elevated during the progression of human gliomas. In the current study, we examined the role of JNK- and ERK-dependent signaling modules in the regulation of MMP-9 production and the invasive behavior of the human glioblastoma cell line SNB19, in which JNK/ERK1 is constitutively activated. SNB19 cells that were transfected with dominant-negative JNK, MEKK, and ERK1 expression vectors showed reduced MMP-9 promoter activity. In addition, conditioned medium collected from SNB19 cells transfected with these expression vectors showed diminished MMP-9 activity in the presence of phorbol myristate acetate, as determined by gelatin zymography. The cotransfection of SNB19 cells with kinase-deficient c-raf also diminished MMP-9 promoter activity. Further, in the presence of a specific inhibitor of MEKK (PD098059), the Matrigel invasion assay showed the invasiveness of dominant-negative SNB19 cells transfected with dominant-negative JNK1 or ERK1 to be remarkably reduced. In conclusion, our studies showed for the first time that MMP-9 production and the invasive behavior of SNB19 cells are regulated by JNK- and ERK-dependent signaling modules and that interfering with either of the pathways reduces invasiveness.

Effects of radiation on the levels of MMP‐2, MMP‐9 and TIMP‐1 during morphogenic glial‐endothelial cell interactions

Radiation‐induced damage to the central nervous system (CNS) is believed to target glial or endothelial cells or both, although the pathophysiology of the process is poorly understood. We therefore used a coculture system, in which glioblastoma SNB19 cells induced bovine retinal endothelial (BRE) cells to form capillary‐like structures, to examine the role of ionizing radiation in modulating the production of matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinase‐1 (TIMP‐1). In particular, we irradiated both BRE cells and cocultures of BRE and SNB19 cells with a single dose of X‐rays and then estimated the levels of MMP‐2, MMP‐9 and TIMP‐1. Gelatin zymography revealed a continuous increase in the levels of MMP‐2 and MMP‐9 during capillary‐like structure formation. Of note, the levels of both MMP‐2 and MMP‐9 were markedly higher in irradiated cocultures at 72 hr after irradiation than in untreated cocultures. Northern blot analysis also demonstrated an increased expression of MMP‐9 mRNA in the irradiated cocultures. In addition, TIMP‐1 mRNA and protein levels increased up to 48 hr in both irradiated and nonirradiated BRE cells and in nonirradiated cocultures, but there was a significant decrease in the TIMP‐1 mRNA and protein levels in irradiated cocultures. It takes about 72 hr for capillaries to form in nonirradiated cocultures, but these capillary networks fail to form in endothelial cells in irradiated cocultures. These findings establish that radiation differentially affects the production of MMP‐2, MMP‐9 and TIMP‐1 during glial‐endothelial morphogenesis and suggest mechanisms by which microvessels in the CNS respond to radiation. Int. J. Cancer 88:766–771, 2000.

Expression and role of matrix metalloproteinases MMP-2 and MMP-9 in human spinal column tumors.

Matrix metalloproteinases (MMPs) have been implicated in the process of tumor invasion and metastasis formation. Thus, we determined the expression of MMPs in various primary and metastatic spinal tumors in order to assess the role of these enzymes in spinal invasion. MMP expression was examined by immuno-histochemical localization, and quantitative evaluation of MMP protein content was determined by enzyme-linked immunosorbant assay (ELISA) and Western blotting. MMP enzyme activity was determined by gelatin zymography. Lung carcinomas and melanomas metastatic to the spine were shown to have higher levels of MMP-9 activity than those of breast, thyroid, renal metastases and primary spinal tumors. Immunohistochemical analysis revealed similar difference in expression of MMP-9 in tissue samples. When the tissue samples were subjected to gelatin zymography for examination of MMP-2 and MMP-9 activity and to ELISA and Western blotting for quantitative estimation of protein content, the most striking results were obtained for lung carcinomas and melanomas relative to the other tumors. Lung carcinomas and melanomas metastatic to the spine had considerably higher levels of MMP-9 activity than those of primary spinal tumor or breast, thyroid, and renal carcinoma metastases. Within the metastatic tumor category, neoplasms that are known to be associated with the shortest overall survival rates and most aggressive behavior, such as lung carcinomas and melanomas, had the highest levels of MMP-2 and MMP-9 activity compared to those less aggressive metastatic tumors such as breast, renal cell, and thyroid carcinomas. Our results suggest that MMPs may contribute to the metastases to the spinal column, and overexpression of these enzymes may correlate with enhanced invasive properties of both primary and metastatic spinal tumors.© Kluwer Academic Publishers 1998

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

The purpose of this study was to investigate the roles of matrix metalloproteinase-9 (MMP-9) and tissue inhibitor of metalloproteinase-1 (TIMP-1) in the formation of capillary structures by human brain microvascular endothelial cells cocultured with SNB19 glioblastoma cells. Unstimulated cocultures did not form capillaries and produce MMP-9 but stimulation with the protein kinase C (PKC) activator 4-phorbol-12-myristate 13-acetate (PMA) produced MMP-9 and capillary networks. Addition of recombinant MMP-9 increased capillary formation. Anti-MMP-9 antibodies, TIMP-1, the synthetic MMPs inhibitor Batimastat (BB-94), and the PKC inhibitor calphostin-C all reduced MMP-9 activity and capillary network formation in these cocultures. Cytochalasin-D in the presence of PMA suppressed MMP-9 expression and capillary formation, but colchicine-B had no such effect. Finally, PMA-induced MMP-9 expression and capillary formation were inhibited by the MEKK-specific inhibitor PD98059. These results suggest that MMP-9 is important in endothelial cell morphogenesis and the formation of capillaries in glial/endothelial cocultures in vitro.

Expression and localization of urokinase-type plasminogen activator in human spinal column tumors.

The Institute for Molecular Medicine, Huntington Beach CA 92649 USA We have sought to determine the production and activity of serine proteases in primary and metastatic spinal tumors and the association of these enzymes with the invasive and metastatic properties of spinal column tumors. Using immunohistochemical techniques, the cellular localization and expression of uroki-nase- type plasminogen activator (uPA) was assessed, whereas its activity was determined by fibrin zymog-raphy, and the amounts of enzyme were measured by an enzyme-linked immunosorbent assay (ELISA) in primary spinal column tumors (chordoma, chondrosarcoma, and giant cell tumor) and metastatic tumors of the spine arising from various malignancies (breast, lung, thyroid, and renal cell carcinomas, and melanomas). Metastatic tumors displayed higher levels of uPA activity than did primary spinal tumors (P < 0.001). Immunohistochemical analysis revealed that uPA expression was highest in metastases from lung and breast carcinomas and melanomas, followed by metastatic tumors from thyr oid and renal cell carcinomas. Similar results were obtained for uPA activity and enzyme level as determined by fibrin zymography and ELISA, respectively. We conclude that metastatic spinal tumors possess higher levels of uPA expression and activity than the primary spinal tumors, which tend to be less aggressive and only locally invasive malignancies. The results suggest that the plasminogen system may participate in the metastasis of tumors to the spinal column.© Kluwer Academic Publishers 1998