Beta 1 integrin is essential for teratoma growth and angiogenesis.

Teratomas are benign tumors that form after ectopic injection of embryonic stem (ES) cells into mice and contain derivatives of all primitive germ layers. To study the role of beta 1 integrin during teratoma formation, we compared teratomas induced by normal and beta1-null ES cells. Injection of normal ES cells gave rise to large teratomas. In contrast, beta 1-null ES cells either did not grow or formed small teratomas with an average weight of <5% of that of normal teratomas. Histological analysis of beta 1-null teratomas revealed the presence of various differentiated cells, however, a much lower number of host-derived stromal cells than in normal teratomas. Fibronectin, collagen I, and nidogen were expressed but, in contrast to normal teratomas, diffusely deposited in beta1-null teratomas. Basement membranes were present but with irregular shape and detached from the cell surface. Normal teratomas had large blood vessels with a smooth inner surface, containing both host- and ES cell-derived endothelial cells. In contrast, beta 1-null teratomas had small vessels that were loosely embedded into the connective tissue. Furthermore, endothelial cells were always of host-derived origin and formed blood vessels with an irregular inner surface. Although beta 1- deficient endothelial cells were absent in teratomas, beta 1-null ES cells could differentiate in vitro into endothelial cells. The formation of a complex vasculature, however, was significantly delayed and of poor quality in beta1-null embryoid bodies. Moreover, while vascular endothelial growth factor induced proliferation of endothelial cells as well as an extensive branching of blood vessels in normal embryoid bodies, it had no effect in beta 1-null embryoid bodies.

BCL-xL: time-dependent dissociation between modulation of apoptosis and invasiveness in human malignant glioma cells.

Conditionally BCL-xL-overexpressing LNT-229 Tet-On glioma cell clones were generated to investigate whether the 'antiapoptosis phenotype' and the 'motility phenotype' mediated by BCL-2 family proteins in glioma cells could be separated. BCL-xL induction led to an immediate and concentration-dependent protection of LNT-229 cells from apoptosis. BCL-xL induction for up to 3 days did not result in altered invasiveness. In contrast, long-term BCL-xL induction for 21 days resulted in increased transforming growth factor-beta2 expression, and in metalloproteinase-2 and -14 dependent, but integrin independent, increased invasiveness. Withdrawal of doxycycline (Dox) abolished the protection from apoptosis whereas the 'invasion phenotype' remained stable. Dox stimulation of BCL-xL-inducible LNT-229 cells conferred infiltrative growth to BCL-xL-positive glioma cells in vivo and reduced the survival of tumor-bearing mice. These data allow to dissect a direct antiapoptotic action of BCL-xL from an indirect effect, presumably mediated by altered gene expression, which modifies tumor cell invasiveness in vitro and in vivo.

Beta1 integrin promotes but is not essential for metastasis of ras-myc transformed fibroblasts.

To investigate the role of beta1 integrin during tumor metastasis, we established a ras-myc transformed fibroblastoid cell line with a disrupted beta1 integrin gene on both alleles (GERM 11). Stable transfection of this cell line with an expression vector encoding beta1A integrin resulted in beta1A integrin-expressing sublines. Tumors were induced by subcutaneous injection of GERM 11 cells and 3 independent beta1 integrin expressing sublines (GERM 116, 1A10, 2F2) into syngeneic mice. After 10 days tumors were surgically removed. While average weights of GERM 11 and GERM 116 tumors were similar, tumors induced by the high expressing clones 1A10 and 2F2 were markedly smaller, suggesting an inverse correlation of tumor growth and beta1 integrin expression. The metastasis potential of all three beta1 integrin-expressing GERM 11 sublines tested was significantly higher than that of the beta1-deficient GERM 11 cells. GERM 116 tumors led in all animals to severe metastasis in lung and liver, while GERM 11 tumors induced only a few metastatic foci in the lung. Stroma of both tumors contained nidogen and high amounts of tenascin C, but only a few very low levels of fibronectin, laminin-1, and collagen type I. Beta1 integrin, therefore, increases but is not essential for metastasis of ras-myc transformed fibroblasts.

Involvement of PA/plasmin system in the processing of pro-MMP-9 and in the second step of pro-MMP-2 activation.

Pro-MMP2 activation is a two-step process resulting in (1) an intermediate 64 kDa form generated by the MT1-MMP activity, and (2) a mature 62 kDa form. Addition of plasminogen to HT1080 cells cultured under various conditions, or to their membrane preparation, induced a complete conversion of the intermediate MMP-2 form to the mature one, and processing of pro-MMP-9. The pro-MMP-2 activation was inhibited by plasmin inhibitors and anti-uPA antibody. These results provide evidence for involvement of the PA/plasmin system in the second step of MMP-2 activation.

Matrix metalloproteinase-9 is elevated in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced parkinsonism in mice.

Matrix metalloproteinases (MMPs) are proteolytic enzymes capable of degrading components of the extracellular matrix. Recent evidence has implicated MMPs in the pathogenesis of neurodegenerative diseases as Alzheimer's disease and amyotrophic lateral sclerosis. In this study, we investigated the involvement of MMP-9 (gelatinase B) in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model of Parkinson's disease using zymography, immunohistochemistry, and Western blot analysis. The activity of MMP-9 was upregulated at 3 h after MPTP injection in the striatum and after 24 h in the substantia nigra. Although MMP-9 expression decreased in the striatum by 72 h, it remained elevated in the substantia nigra compared to controls up to 7 d after MPTP administration. Immunohistochemistry showed that neurons and microglia are the source of MMP-9 expression after MPTP administration to mice. Treatment with a hydroxamate-based MMP inhibitor, Ro 28-2653 significantly reduced dopamine depletion and loss of tyrosine hydroxylase immunoreactive neurons in the substantia nigra pars compacta. MMP-9 expression as measured via zymography in the substantia nigra was reduced by the MMP inhibitor. These results indicate that MMP-9 is induced after MPTP application in mice and that pharmacologic inhibition of MMPs protects against MPTP neurotoxicity.

Combined treatment with serine protease inhibitor aprotinin and matrix metalloproteinase inhibitor Batimastat (BB-94) does not prevent invasion of human esophageal and ovarian carcinoma cells in vivo.

Many studies have highlighted the role played by matrix metalloproteinases MMP-2 and -9, by serine proteases uPA and plasmin in tumor cell invasion. This study investigates the impact of the MMP-inhibitor Batimastat and/or the serine protease inhibitor Aprotinin on the in vitro proteolytic activity and in vivo invasive behavior the of esophageal (OC1) and ovarian (OVCAR-3) carcinoma cells. In presence and absence of inhibitors, proteolytic activity of the tumor cells was determined by caseinolytic and collagenolytic in vitro assays and tumor cell invasion by intraperitoneal inoculation of the tumor cells into nude mice. In vitro, Aprotinin, tested alone or in combination with Batimastat, efficiently inhibited degradation of collagen IV and casein by the tumor cells. Batimastat alone had no effect on caseinolytic activities and only partially blocked collagen-type-IV-degradation by the tumor cells. In vivo, Aprotinin tested alone or in combination with Batimastat did not prevent tumor cell invasion. Treatment of tumor bearing mice with Batimastat significantly inhibited tumor growth but promoted tumor cell invasion into the liver. Our findings demonstrate that the inhibition pattern of cellular proteolytic activity achieved in vitro by a serine protease and an MMP inhibitor may lead to predictions that are not necessarily verified in vivo and may even have adverse effects.

Selective gelatinase blockage ameliorates acute DSS colitis.

In the experimental models of intestinal inflammation and humans with inflammatory bowel diseases (IBD), increased levels of the matrix metalloproteinases (MMPs), MMP-2 and -9 (also referred to as gelatinase A and B, respectively), in inflamed tissue sites can be detected. In the presented study, we investigated potential beneficial effects exerted by doxycycline nonselectively blocking MMPs and the selective gelatinase inhibitor RO28-2653 in acute DSS colitis. Treatment with either compound for 8 days ameliorated clinical colitis pathology with a superior outcome in RO28-2653-treated animals. As compared to placebo controls, histopathological changes in the colon were less distinct following MMP blockage and IL-6 secretion in ex vivo biopsies was downregulated, paralleled by a diminished influx of pro-inflammatory immune cells and lack of overgrowth of the colonic lumen by potentially pro-inflammatory Escherichia coli of the commensal colon flora. We conclude that selective gelatinase inhibition not only exerts beneficial effects by disrupting the vicious cycle of positive feedback between immune cell stimulation and MMP induction but also prevents overgrowth of the colonic lumen by pro-inflammatory E. coli despite a lack of direct anti-bacterial properties, thus unaffecting the commensal gut microbiota. These findings put RO28-2653 into a center stage for development of intervention strategies in human IBD.

TNF-alpha-converting enzyme (TACE/ADAM17)-dependent loss of CD30 induced by proteasome inhibition through reactive oxygen species.

Combinations with proteasome inhibitors are currently being investigated to improve the therapy of hematological malignancies. We previously found that proteasome inhibition by bortezomib failed to sensitize anti-CD30 antibody (Ab)-based lymphoma cell killing. In this study, we demonstrate in L540 Hodgkin's lymphoma cells that proteasome inhibition not only communicates apoptosis but also more rapidly causes a loss of CD30 antigen from cell membrane and a simultaneous release of soluble CD30, a targeting competitor. This shedding was catalyzed by the tumor necrosis factor (TNF)-alpha-converting enzyme (TACE, ADAM17) and blocked by the ADAM17-selective inhibitor, Ro32-7315. In parallel with CD30 shedding, bortezomib caused the generation of reactive oxygen species (ROS). As apoptosis and shedding were inhibited by the radical scavenger, N-acetyl-L-cysteine, ROS might have a pivotal function in both effects. In contrast, the pan-caspase inhibitor, zVAD-fmk, blocked bortezomib-induced apoptosis but not CD30 shedding, and Ro32-7315 blocked shedding but allowed apoptosis. This suggests independent terminal signaling pathways that are conflicting in Ab-based immunotherapy. Consequently, shedding inhibition substantially improved the synergistic antitumor efficacy of the human anti-CD30 Ab, MDX-060, and bortezomib. As proteasome inhibition also stimulated loss of TNF receptors, interleukin-6 receptor and syndecan-1 in different leukemia and lymphoma cell lines, we concluded that proteasome inhibition might impede targeted therapy against antigens susceptible to shedding.

Plant biochemistry of xenobiotics. Purification and properties of a wheat esterase hydrolyzing the plasticizer chemical, bis(2-ethylhexyl)phthalate.

A soluble wheat esterase, catalyzing a cleavage of the mass-produced plasticizer chemical, bis(2-ethylhexyl)phthalate (DEHP), has been discovered. Although wheat plants and seeds as well as cultured wheat cells contained more than 12 non-specific esterase activities, only a single protein with a marked preference for a substrate chain-length of 6-8 carbon atoms was active with DEHP. This enzyme is shown to differ from all previously characterized plant lipases and esterases. The enzyme was purified 10-fold from wheat plants and 280-fold, to electrophoretic homogeneity, from cultured wheat cells. An apparent functional molecular mass of 38 000 Da and an apparent subunit molecular mass of 22 000 Da were determined. Inhibitor experiments pointed to the catalytic involvement of a serine residue. Cleavage of DEHP by the purified enzyme was about 10(4) times slower than cleavage of 4-nitrophenyl octanoate. This was consistent with previous evidence for a rate-limiting role of the esterase reaction in DEHP metabolism by intact wheat cells.

Matrix metalloproteinases 2 and 9 mediate epidermal growth factor receptor transactivation by gonadotropin-releasing hormone.

Rapid engagement of the extracellular signal-regulated kinase (ERK) cascade via the Gq/11-coupled GnRH receptor (GnRHR) is mediated by transactivation of the epidermal growth factor receptor (EGFR). Here we show that the cross-talk between GnRHR and EGFR in gonadotropic cells is accomplished via gelatinases A and B (matrix metalloproteinases (MMPs) 2 and 9), identifying gelatinases as the first distinct members of the MMP family mediating EGFR transactivation by G protein-coupled receptors. Using a specific MMP2 and MMP9 inhibitor, Ro28-2653, GnRH-dependent EGFR transactivation was abrogated. Proving the specificity of the effect, transient transfection of alphaT3-1 cells with ribozymes directed against MMP2 or MMP9 specifically blocked EGFR tyrosine phosphorylation in response to GnRH stimulation. GnRH challenge of alphaT3-1 cells furthered the release of active MMP2 and MMP9 and increased their gelatinolytic activities within 5 min. Rapid release of activated MMP2 or MMP9 was inhibited by ribozyme-targeted down-regulation of MT1-MMP or MMP2, respectively. We found that GnRH-induced Src, Ras, and ERK activation were also gelatinase-dependent. Thus, gelatinase-induced EGFR transactivation was required to engage the extracellular-signal regulated kinase cascade. Activation of c-Jun N-terminal kinase and p38 MAPK by GnRH was unaffected by EGFR or gelatinase inhibition that, however, suppressed GnRH induction of c-Jun and c-Fos. Our findings suggest a novel role for gelatinases in the endocrine regulation of pituitary gonadotropes.

Type IV collagen induces matrix metalloproteinase 2 activation in HT1080 fibrosarcoma cells.

Matrix metalloproteinase 2 (MMP-2) activation has been described as a "master switch" which triggers tumor spread and metastatic progression. We show here that type IV collagen, a major component of basement membranes, promotes MMP-2 activation by HT1080 cells. When plated on plastic, HT1080 cells constitutively processed the 66-kDa pro-MMP-2 into a 62-kDa intermediate activated form, most probably through a membrane type (MT) 1 MMP-dependent mechanism. In the presence of type IV collagen, part of this intermediate form was further processed to fully activated 59-kDa MMP-2. This activation was prevented by tissue inhibitor of MMP (TIMP)-2 and a broad-spectrum hydroxamic acid-based synthetic MMP inhibitor (GI129471). Type IV collagen-mediated pro-MMP-2 activation did not involve either a transcriptional modulation of MMP-2, MT1-MMP, or TIMP-2 expression nor any alteration of MT1-MMP protein synthesis or processing. An inverse relationship between MMP-2 activation and the concentration of secreted TIMP-2 was observed. This is consistent with our previous report that TIMP-2 degradation is probably linked to the MT1-MMP-dependent MMP-2 activation mechanism. Because invasive tumor cells must breach basement membranes at different steps of the metastatic dissemination, the ability of HT1080 cells to activate pro-MMP-2 in the presence of type IV collagen might represent a key regulatory mechanism for the acquisition of an invasive potential.

Modulation of the expression of interstitial and type-IV collagenases in coculture of HT1080 fibrosarcoma cells and fibroblasts.

Members of the metalloproteinase family (MMPs) are known to play a crucial role in the metastatic cascade. Here, we report some investigations about the synthesis of interstitial and type-IV collagenases (gelatinases A and B) in a model of coculture of human fibroblasts and HT 1080 fibrosarcoma cells. The interstitial collagenase activity, mainly found in the conditioned medium of fibroblasts, and its mRNA level were increased in the in vitro coculture model. In contrast, gelatinase A was produced by both cell types. The HT 1080 cells additionally synthesised gelatinase B. In coculture, an enhancement of gelatinase A and the presence of its activated form were observed. Northern blot analysis demonstrated that this enzymatic enhancement occurred at a pretranslational level. The stimulation of the interstitial collagenase activity was partially mediated through soluble factor(s), whereas increased gelatinase A appeared to require direct cell-cell interactions. The extracellular matrix component, type-I collagen, stimulated the enzymatic activities released by the individual cells, but it did not modulate the synthesis of interstitial collagenase in coculture. Our results demonstrate that distinct MMPs are modulated by distinct mechanisms, all depending on specific interactions between tumour cells and host fibroblasts.

The 1.8-A crystal structure of a matrix metalloproteinase 8-barbiturate inhibitor complex reveals a previously unobserved mechanism for collagenase substrate recognition.

The individual zinc endoproteinases of the tissue degrading matrix metalloproteinase (MMP) family share a common catalytic architecture but are differentiated with respect to substrate specificity, localization, and activation. Variation in domain structure and more subtle structural differences control their characteristic specificity profiles for substrates from among four distinct classes (Nagase, H., and Woessner, J. F. J. (1999) J. Biol. Chem. 274, 21491-21494). Exploitation of these differences may be decisive for the design of anticancer or other drugs, which should be highly selective for their particular MMP targets. Based on the 1.8-A crystal structure of human neutrophil collagenase (MMP-8) in complex with an active site-directed inhibitor (RO200-1770), we identify and describe new structural determinants for substrate and inhibitor recognition in addition to the primary substrate recognition sites. RO200-1770 induces a major rearrangement at a position relevant to substrate recognition near the MMP-8 active site (Ala206-Asn218). In stromelysin (MMP-3), competing stabilizing interactions at the analogous segment hinder a similar rearrangement, consistent with kinetic profiling of several MMPs. Despite the apparent dissimilarity of the inhibitors, the central 2-hydroxypyrimidine-4,6-dione (barbiturate) ring of the inhibitor RO200-1770 mimics the interactions of the hydroxamate-derived inhibitor batimastat (Grams, F., Reinemer, P., Powers, J. C., Kleine, T., Pieper, M., Tschesche, H., Huber, R., and Bode, W. (1995) Eur. J. Biochem. 228, 830-841) for binding to MMP-8. The two additional phenyl and piperidyl ring substituents of the inhibitor bind into the S1' and S2' pockets of MMP-8, respectively. The crystal lattice contains a hydrogen bond between the O(gamma) group of Ser209 and N(delta)1 of His207 of a symmetry related molecule; this interaction suggests a model for recognition of hydroxyprolines present in physiological substrates. We also identify a collagenase-characteristic cis-peptide bond, Asn188-Tyr189, on a loop essential for collagenolytic activity. The sequence conservation pattern at this position marks this cis-peptide bond as a determinant for triple-helical collagen recognition and processing.

The novel synthetic inhibitor of matrix metalloproteinases Ro 28-2653 induces apoptosis in Dunning tumor cells.

The effect of synthetic inhibitors of matrix metalloproteinases (MMP) has been shown against a variety of tumors in preclinical models. Ro 28-2653, a novel synthetic MMP inhibitor, is able to reduce tumor growth in orthotopic prostatic cancer in rats (R3327 Dunning tumor). However, at present this inhibitory mechanism in tumor inhibition in vivo can only be partly explained by the inhibition of the catalytic activity of MMPs overexpressed in cancereous tissue. Using the flow cytometric method, we have investigated the effect of various concentrations of Ro 28-2653 on the Dunning tumor cells with regard to the staining of F-actin and DNA as markers of apoptosis. In combination with fluorescence microscopy we detected the loss of F-actin and the degradation of internucleosomal DNA. This effect of Ro 28-2653 on apoptosis was dose- and time-dependent increasing with concentration between 10 and 100 microg/ml as well as with time of treatment between 24 and 48 h.

Purification of progelatinases A and B by continuous-elution electrophoresis.

Progelatinases A and B were purified from HT1080-conditioned culture medium using a continuous-elution electrophoresis. Initially cell culture medium was ammonium sulfate precipitated. The concentrated proteins were affinity chromatographed on gelatin-Sepharose column. The bound gelatinases were eluted with electrophoresis sample buffer and subjected to continuous-elution electrophoresis. In a single run, under the standardized working conditions, the obtained fractions contained four purified enzymes--progelatinase A (M(r) 72,000), its activated forms (M(r) 62,000 and M(r) 59,000), and progelatinase B (M(r) 92,000). Moreover, the continuous-elution electrophoresis allowed the enzymes separation from their respective inhibitors--TIMP-1 (M(r) 28,500) and TIMP-2 (M(r) 21,000). The purified progelatinases A and B demonstrated high specific activities (150-200 U/micrograms).

Preparation of thieno[3,2-h]cinnolinones as matrix metalloproteinase inhibitors.

A new series of thieno[3,2-h]cinnolinone analogues was synthesized which is structurally related to 2,3,4,4a,5,6-hexahydrothieno [3,2-h]cinnolin-3-one 1, a weak inhibitor of the matrix metalloproteinase MMP-8 (human neutrophil collagenase). Preliminary SAR studies have shown that while C4a-methyl, C7-acetylamino, C7 and C8-nitro substitution, and C4-C4a olefination provided no increase in activity relative to 1, C8-acetylamino substitution as in 5 and 8 was favourable. Moreover, to predict how the thieno[3,2-h]cinnolinone inhibitors might bind to MMP-8, the unsubstituted compound 9 was docked into the MMP-8 crystal structure. These studies revealed that inhibitor 9 does not seem to be able to coordinate the catalytically-active zinc ion but preferably interact with the peptide-binding region of the active site.

Pyrimidine-2,4,6-Triones: a new effective and selective class of matrix metalloproteinase inhibitors.

Matrix metalloproteinases (MMPs) are a family of zinc endopeptidases that have been implicated in various disease processes. Different classes of MMP inhibitors, including hydroxamic acids, phosphinic acids and thiols, have been previously described. Most of these mimic peptides and most likely bind in a similar way to the corresponding peptide substrates. Here we describe pyrimidine-triones as a completely new class of metalloprotease inhibitors. While the pyrimidine-trione template is used as the zinc-chelating moiety, the substituents have been optimized to yield inhibitors comparable in their inhibition efficiency of matrix metalloproteinases to hydroxamic acid derivatives such as batimastat. However, they are much more specific for a small subgroup of MMPs, namely the gelatinases (MMP-2 and MMP-9).