Broad antitumor and antiangiogenic activities of AG3340, a potent and selective MMP inhibitor undergoing advanced oncology clinical trials

Age-related macular degeneration: etiology, pathogenesis, and therapeutic strategies

Age-related macular degeneration is the principal cause of registered legal blindness among those aged over 65 in the United States, western Europe, Australia, and Japan. Despite intensive research, the precise etiology of molecular events that underlie age-related macular degeneration is poorly understood. However, investigations on parallel fronts are addressing this prevalent public health problem. Sophisticated biochemical and biophysical techniques have refined our understanding of the pathobiology of drusen, geographic atrophy, and retinal pigment epithelial detachments. Epidemiological identification of risk factors has facilitated an intelligent search for underlying mechanisms and fueled clinical investigation of behavior modification. Gene searches have not only brought us to the cusp of identifying the culpable gene loci in age-related macular degeneration, but also localized genes responsible for other macular dystrophies. Recent and ongoing investigations, often cued by tumor biology, have revealed an important role for various growth factors, particularly in the neovascular form of the condition. Transgenic and knockout studies have provided important mechanistic insights into the development of choroidal neovascularization, the principal cause of vision loss in age-related macular degeneration. This in turn has culminated in preclinical and clinical trials of directed molecular interventions.

Prinomastat, a hydroxamate inhibitor of matrix metalloproteinases, has a complex effect on migration of breast carcinoma cells

Membrane type-1 matrix metalloproteinase (MT1-MMP) and alphavbeta3 integrin have been directly implicated in tumor cell dissemination and metastasis. We have demonstrated that in the case of breast carcinoma MCF7 cells co-expressing MT1-MMP and alphavbeta3 integrin, the proteinase processes the pro-alphav integrin subunit, thus facilitating alphavbeta3 integrin maturation and cell migration on vitronectin. Our findings show that cell surface MT1-MMP is a short-lived protein with a life span in the range of several hours. In contrast, turnover of alphavbeta3 integrin is much slower. The half-life of alphavbeta3 heterodimer is about 24 hr. This large difference in life span allowed us to distinguish between the effects of MT1-MMP on cell migration brought by matrix proteolysis from those imposed through alphavbeta3 integrin maturation. We then modulated the enzyme's activity by a potent hydroxamate MMP inhibitor, Prinomastat (AG3340), to analyze the divergent effects of MT1-MMP on cell migration. Although Prinomastat immediately blocked MT1-MMP-mediated matrix degradation, the pool of MT1-MMP-modified alphavbeta3 integrin molecules was still capable of mediating cell-matrix interactions. To our considerable surprise, inhibition of MT1-MMP-dependent vitronectin proteolysis by Prinomastat allowed a several-fold increase in migration of MCF7 cells co-expressing MT1-MMP and alphavbeta3 integrin. In contrast, long-term Prinomastat inhibition of MT1-MMP-dependent pro-alphav cleavage and thus alphavbeta3 integrin maturation strongly inhibited cell motility. Our studies suggest that MT1-MMP could actually promote cell migration via modification of the cell surface receptors, including alphavbeta3 integrin, rather than facilitate cell migration through direct cleavage of the matrix proteins.

An MMP-2/MMP-9 inhibitor, 5a, enhances apoptosis induced by ligands of the TNF receptor superfamily in cancer cells

Several studies have shown that matrix metalloproteases (MMPs) promote tumor growth, invasion, and metastasis. Consequently, MMP inhibitors have been developed as a new class of anticancer drugs, many of which are in clinical trials. The exact mechanism of the antineoplastic activity of MMP antagonists is unknown. To investigate the mechanism, we hypothesized that MMP inhibitors enhance the actions of apoptosis-inducing agents. To test this hypothesis, we treated breast, melanoma, leukemia, osteosarcoma, and normal breast epithelial cells with (2R)-2-[(4-biphenylsulfonyl)amino]-3-phenylproprionic acid (compound 5a), an organic inhibitor of MMP-2/MMP-9, alone or in combination with TNFalpha or other apoptotic agents. FACS analysis showed that 5a interacted synergistically with ligands of the TNF receptor superfamily, including TNFalpha and TNF receptor-like apoptosis-inducing ligand (TRAIL), and with a Fas-cross-linking antibody (CH11), UV, paclitaxel, thapsigargin, and staurosporin, to induce apoptosis in a cell-type-specific manner. Other MMP inhibitors did not synergize with TNFalpha. Compound 5a did not act directly on the mitochondrion or via changes in protein synthesis. Instead, the mechanism requires ligand-receptor interaction and caspase 8 activation. Investigation of the effect of 5a on tumor growth in vivo revealed that continuous treatment of subcutaneous melanoma with a combination of 5a plus TRAIL reduced tumor growth and angiogenesis in nude mice. Our data demonstrate that 5a possesses a novel proapoptotic function, thus providing an alternative mechanism for its antineoplastic action. These observations have important implications for combination cancer therapy.

Development of a high-throughput screening assay for inhibitors of aggrecan cleavage using luminescent oxygen channeling (AlphaScreen )

Aggrecan is one of the most important structural components of joint cartilage, and members of the metalloprotease (MMP) and ADAM (a disintegrin and metalloproteinase) protease families have been shown to degrade aggrecan in vivo. A robust assay for aggrecan-degrading activity suitable for high-throughput screening (HTS) was set up and measured using AlphaScreen. In this technology, beads brought into proximity through cross-linking and stimulated with laser light generate a signal through luminescent oxygen tunneling, the outcome of which is a time-resolved fluorescent signal. Specific antibodies to the carbohydrate side chains of aggrecan were harnessed to create a scaffold whereby aggrecan could form a cross-link between donor and acceptor AlphaScreen detector beads. Digested aggrecan, which failed to form a cross-link, generated no signal, so that inhibitors of the digestion could be detected as a restoration of signal. The development of this assay and its validation for HTS are described in this report.

Mechanical stretch induces MMP-2 release and activation in lung endothelium: role of EMMPRIN

High-volume mechanical ventilation leads to ventilator-induced lung injury. This type of lung injury is accompanied by an increased release and activation of matrix metalloproteinases (MMPs). To investigate the mechanism leading to the increased MMP release, we systematically studied the effect of mechanical stretch on human microvascular endothelial cells isolated from the lung. We exposed cells grown on collagen 1 BioFlex plates to sinusoidal cyclic stretch at 0.5 Hz using the Flexercell system with 17-18% elongation of cells. After 4 days of cell stretching, conditioned media and cell lysate were collected and analyzed by gelatin, casein, and reverse zymograms as well as Western blotting. RT-PCR of mRNA extracted from stretched cells was performed. Our results show that 1) cyclic stretch led to increased release and activation of MMP-2 and MMP-1; 2) the activation of MMP-2 was accompanied by an increase in membrane type-1 MMP (MT1-MMP) and inhibited by a hydroxamic acid-derived inhibitor of MMPs (Prinomastat, AG3340); and 3) the MMP-2 release and activation were preceded by an increase in production of extracellular MMP inducer (EMMPRIN). These results suggest that cyclic mechanical stretch leads to MMP-2 activation through an MT1-MMP mechanism. EMMPRIN may play an important role in the release and activation of MMPs during lung injury.

A third-generation matrix metalloproteinase (MMP) inhibitor (ONO-4817) combined with docetaxel suppresses progression of lung micrometastasis of MMP-expressing tumor cells in nude mice

The lung is the common target organ of hematogenous metastasis that restricts the prognosis of cancer patients. MMPs play a pivotal role in metastasis by promoting tumor invasion and angiogenesis; therefore, a large number of MMPIs have been developed. Our purpose was to determine the therapeutic efficacy of a selective-spectrum MMPI, ONO-4817 (inhibits MMP-2 and MMP-9 but not MMP-1), against established lung micrometastasis in combination with a cytotoxic anticancer drug, DOC, in a nude mouse model. Human non-small cell lung cancer PC14PE6 (adenocarcinoma) or H226 (squamous cell carcinoma) cells, expressing MMP-2, MMP-9 and/or MMP-1, were injected i.v. into nude mice on day 0. Mice received a single injection of DOC on day 7 (after establishment of micrometastasis) and/or ONO-4817 mixed with food from day 7 to the end of experiments. Monotherapy with ONO-4817 or DOC inhibited formation of lung metastasis by PC14PE6 and H226 cells. In addition, combined use of ONO-4817 with DOC significantly suppressed the tumor burden of H226 and PC14PE6 cells in the lung and prolonged the survival of PC14PE6-bearing mice compared to ONO-4817 or DOC alone. These therapies did not affect the body weight or food intake of tumor-bearing mice. FIZ revealed that lung lesions, but not nontumor parenchyma of the lung, expressed gelatinolytic activity and that treatment with ONO-4817 abrogated the gelatinolytic activity in lung lesions. These results suggest that the combined use of MMPIs with cytotoxic anticancer drugs may be helpful in the control of established lung micrometastasis by tumor cells expressing MMPs.

Rho kinase and matrix metalloproteinase inhibitors cooperate to inhibit angiogenesis and growth of human prostate cancer xenotransplants

The purpose of this study was to determine the effects of inhibitors of Rho kinase (ROK) and matrix metalloproteinases (MMPs) on angiogenesis and tumor growth and to evaluate ROK activity in human prostate cancer PC3 cells and endothelial cells (HUVECs). Vacuolation by endothelial cells and lumen formation, the earliest detectable stages of angiogenesis, were inhibited by the ROK inhibitor Wf-536. Combining Wf-536 with the MMP inhibitor Marimastat greatly enhanced in vitro inhibition of endothelial vacuolation, lumen and cord formation, and VEGF- and HGF-stimulated endothelial sprout formation from aorta. Inhibition of sprout formation by the two inhibitors was synergistic. Both agents inhibited migration of HUVECs. The regulatory subunit (MYPT1) of the myosin phosphatase was phosphorylated in PC3 cells and HUVECs, and phosphorylation of MYPT1 and the myosin regulatory light chain was reduced by Wf-536, providing direct evidence of ROK activity. Early treatment of immuno-incompetent mice bearing xenotransplants of PC3 cells with a combination of Wf-536 plus Marimastat with or without Paclitaxel, significantly inhibited tumor growth, prevented tumor growth escape after discontinuation of Paclitaxel, and increased survival.

Imidazole ring-opened DNA purines and their biological significance

Fragmentation of purine imidazole ring and production of formamidopyrimidines in deoxynucleosides (Fapy lesions) occurs upon DNA oxidation as well as upon spontaneous or alkali-triggered rearrangement of certain alkylated bases. Many chemotherapeutic agents such as cyclophosphamide or thiotepa produce such lesions in DNA. Unsubstituted FapyA and FapyG, formed upon DNA oxidation cause moderate inhibition of DNA synthesis, which is DNA polymerase and sequence dependent. Fapy-7MeG, a methylated counterpart of FapyG-, a efficiently inhibits DNA replication in vitro and in E.coli, however its mutagenic potency is low. This is probably due to preferential incorporation of cytosine opposite Fapy-7MeG and preferential extension of Fapy-7MeG:C pair. In contrast, FapyA and Fapy-7MeA possess miscoding potential. Both lesions in SOS induced E.coli preferentially mispair with cytosine giving rise to A-->G transitions. Fapy lesions substituted with longer chain alkyl groups also show simult aneous lethal and mutagenic properties. Fapy lesions are actively eliminated from DNA by repair glycosylases specific for oxidized purines and pyrimidines both in bacteria and eukaryotic cells. Bacterial enzymes include E.coli formamidopyrimidine-DNA-glycosylase (Fpg protein), endonuclease III (Nth protein) and endonuclease VIII (Nei protein).

Roles of matrix metalloproteinases in tumor metastasis and angiogenesis

Matrix metalloproteinases (MMPs), zinc dependent proteolytic enzymes, cleave extracellular matrix (ECM: collagen, laminin, firbronectin, etc) as well as non-matrix substrates (growth factors, cell surface receptors, etc). The deregulation of MMPs is involved in many diseases, such as tumor metastasis, rheumatoid arthritis, and periodontal disease. Metastasis is the major cause of death among cancer patients. In this review, we will focus on the roles of MMPs in tumor metastasis. The process of metastasis involves a cascade of linked, sequential steps that involve multiple host-tumor interactions. Specifically, MMPs are involved in many steps of tumor metastasis. These include tumor invasion, migration, host immune escape, extravasation, angiogenesis, and tumor growth. Therefore, without MMPs, the tumor cell cannot perform successful metastasis. The activities of MMPs are tightly regulated at the gene transcription levels, zymogen activation by proteolysis, and inhibition of active forms by endogenous inhibitors, tissue inhibitor of metalloproteinase (TIMP), and RECK. The detailed regulations of MMPs are described in this review.

A critical evaluation of DNA adducts as biological markers for human exposure to polycyclic aromatic compounds

The causative role of polycyclic aromatic hydrocarbons (PAH) in human carcinogenesis is undisputed. Measurements of PAH-DNA adduct levels in easily accessible white blood cells therefore represent useful early endpoints in exposure intervention or chemoprevention studies. The successful applicability of DNA adducts as early endpoints depends on several criteria: i. adduct levels in easily accessible surrogate tissues should reflect adduct levels in target-tissues, ii. toxicokinetics and the temporal relevance should be properly defined. iii. sources of interand intra-individual variability must be known and controllable, and finally iv. adduct analyses must have advantages as compared to other markers of PAHexposure. In general, higher DNA adduct levels or a higher proportion of subjects with detectable DNA adduct levels were found in exposed individuals as compared with nonexposed subjects, but saturation may occur at high exposures. Furthermore, DNA adduct levels varied according to changes in exposure, for example smoking cessation resulted in lower DNA adduct levels and adduct levels paralleled seasonal variations of air-pollution. Intraindividual variation during continuous exposure was low over a short period of time (weeks), but varied significantly when longer time periods (months) were investigated. Inter-individual variation is currently only partly explained by genetic polymorphisms in genes involved in PAH-metabolism and deserves further investigation. DNA adduct measurements may have three advantages over traditional exposure assessment: i. they can smooth the extreme variability in exposure which is typical for environmental toxicants and may integrate exposure over a longer period of time. Therefore, DNA adduct assessment may reduce the monitoring effort. ii. biological monitoring of DNA adducts accounts for all exposure routes. iii. DNA adducts may account for inter-individual differences in uptake, elimination, distribution, metabolism and repair amongst exposed individuals. In conclusion, there is now a sufficiently large scientific basis to justify the application of DNA adduct measurements as biomarkers in exposure assessment and intervention studies. Their use in risk-assessment, however, requires further investigation.

Anti-invasive effect of an anti-matrix metalloproteinase agent in a murine brain slice model using the serial monitoring of green fluorescent protein-labeled glioma cells

OBJECTIVE

We aimed to analyze the anti-invasive effect of the anti-matrix metalloproteinase (anti-MMP) agent SI-27 by quantitative tracking of enhanced green fluorescent protein (EGFP)-labeled human malignant glioma cell lines in a brain slice model.

METHODS

Persistent expression of EGFP in human malignant glioma cell clones (U87MG, U251MG, and U373MG) was established with the use of the pEGFP-C1 vector. Tumor spheroid in 1 microl Matrigel was implanted into the caudate nucleus-putamen of a severe combined immunodeficient mouse brain slice. To allow the quantitative assessment of tumor cell invasion, the invasion area index was measured on Days 1, 3, 5, and 7 with a fluorescence stereomicroscope and an image analyzer in the presence of various concentrations of SI-27 (0, 1, 10, 50, or 100 microg/ml).

RESULTS

In the control group (0 microg/ml), all glioma cell lines invaded in a fingerlike fashion and reached the contralateral hemisphere through the corpus callosum. SI-27 at concentrations of 10, 50, and 100 microg/ml significantly suppressed the invasion area index on Days 5 and 7 in a dose-dependent manner, whereas 1 microg/ml had no effect. Transmission electron microscopy and laser confocal microscopy indicated that the tumor cells had penetrated the brain slice and that the normal structural integrity of the brain was maintained until Day 7.

CONCLUSION

This model enabled unequivocal periodic tracking of individual invading tumor cells in normal brain. The significant suppression of glioma cell invasion by noncytotoxic concentrations of SI-27 indicates that anti-MMP treatment may represent an important future therapeutic strategy for malignant cerebral neoplasms.

Matrix metalloproteinase-9 in lung remodeling

Matrix metalloproteinase (MMP)-9 (Gelatinase B, 92-kD type IV collagenase, EC 3.4.24.35) is an MMP that is present in low quantities in the healthy adult lung, but much more abundant in several lung diseases, including asthma, idiopathic pulmonary fibrosis (IPF), and chronic obstructive pulmonary disease (COPD). Despite numerous reports of MMP-9 in these and other lung diseases, whether MMP-9 is causal in lung remodeling or part of the inflammatory and reparative response remains to be determined. Many intrinsic lung cells can be stimulated to produce MMP-9, but much of the information regarding MMP-9 in the lung deals with MMP-9 from inflammatory cells. The multiple locations and cell types producing MMP-9 are consistent with multiple functions in different microenvironments. In addition to digestion of structural proteins and antiproteases, MMP-9 can modify cellular function by regulation of cytokines and matrix-bound growth factors. Determining the role of MMP-9 in health and disease will be important, because broad spectrum and specific inhibitors will soon be available to enable conversion of the bench knowledge to bedside practice. This review addresses the current understanding of MMP-9 in human asthma, IPF, and COPD, and in animal models of these conditions.

NMR-based modification of matrix metalloproteinase inhibitors with improved bioavailability

The NMR-based discovery of biaryl hydroxamate inhibitors of the matrix metalloproteinase stromelysin (MMP-3) has been previously described (Hajduk et al. J. Am. Chem. Soc. 1997, 119, 5818-5827). While potent in vitro, these inhibitors exhibited no in vivo activity due, at least in part, to the poor pharmacokinetic properties of the alkylhydroxamate moiety. To circumvent this liability, NMR-based screening was implemented to identify alternative zinc-chelating groups. Using this technique, 1-naphthyl hydroxamate was found to bind tightly to the protein (K(D) = 50 microM) and was identified as a candidate for incorporation into the lead series. On the basis of NMR-derived structural information, the naphthyl hydroxamate and biaryl fragments were linked together to yield inhibitors of this enzyme that exhibited improved bioavailability. These studies demonstrate that the NMR-based screening of fragments can be effectively applied to improve the physicochemical or pharmacokinetic profile of lead compounds.

Novel therapies for lung cancer

Lung cancer remains the leading cause of cancer mortality in the US. For the majority of patients with advanced non-small cell lung cancer, chemotherapy with or without radiation therapy is the mainstay of treatment. Despite the modest improvement in survival for these patients, prognosis remains dismal. However, the expanding knowledge of tumor biology in recent years has resulted in the promising development of a new class of "molecularly targeted" agents, which selectively target cancer cells at the molecular, biochemical, and genetic level, thus minimizing toxic effects on normal tissues. A wide range of molecularly targeted agents are being actively investigated in lung cancer therapy as single agents or in combination with conventional modalities. In this review, we discuss some of the agents furthest along in development: epidermal growth factor receptor inhibitors, anti-angiogenic agents, inhibitors of biologically important enzymes such as matrix metalloproteinases and farnesyltransferase, gene therapy including gene replacement and antisense therapy, and cell cycle disruptors.

Augmented anti-metastatic efficacy of a selective matrix metalloproteinase inhibitor, MMI-166, in combination with CPT-11

The anti-metastatic efficacy of MMI-166, which is a selective matrix metalloproteinase (MMP) inhibitor, in combination with CPT-11 was examined using two metastasis models of human gastrointestinal cancer cells. In the liver metastasis model, C-IH human colon cancer cells were injected into the spleen of athymic BALB/c nude mice. Daily oral (p.o.) dosing of MMI-166 at 200 mg/kg starting 1 day after tumor inoculation led to a significantly prolonged survival effect by inhibiting liver metastasis of C-1H tumor cells. CPT-11 (5 or 20 mg/kg) was administered intraperitoneally (i.p.) three times on day 3, day 7 and day 11 and also improved the survival of tumor-inoculated mice compared with the vehicle control. When MMI-166 was combined with CPT-11, the anti-metastatic efficacy was significantly augmented. Moreover, long tumor-free survival was noted in two of eight mice that were given the combination therapy but not either MMI-166 or CPT-11 monotherapy. In the peritoneal dissemination model, TMK-1 human gastric cancer cells were injected i.p. into nude mice. While both MMI-166, administered daily p.o. from day 1 at 200 mg/kg, and CPT-11, administered intravenously (i.v.) three times, inhibited the tumor dissemination and growth, the combination therapy of MMI-166 plus CPT-11 showed a greater inhibitory effect than each monotherapy. A hematotoxicity study demonstrated that CPT-11 alone significantly decreased the number of white blood cells (WBC) and bone marrow cells (BMC) in the mice during treatment, while the daily administration of MMI-166 alone had no such effect. More importantly, the combination therapy of MMI-166 with CPT-11 did not augment the hematotoxicity caused by CPT-11. An in vitro cytotoxicity study showed that MMI-166 itself neither has direct cytotoxicity in C-1H and TMK-1 tumor cells, nor does it augment the cytotoxicity of SN-38, an active form of CPT-11. The findings indicate that the augmented anti-metastatic efficacy in combination treatment was not simply due to the augmentation of direct cytotoxic activity, but was rather an additive or synergistic effect of anti-metastatic activities with different mechanisms. In conclusion, we demonstrated that the anti-metastatic efficacy against C-1H colon cancer and TMK-1 gastric cancer were augmented by the combination therapy of MMI-166, an orally active MMP inhibitor, with CPT-11. However, the hematotoxicity caused by CPT-11 was not augmented in the combination with MMI-166. Thus, the combination therapy of MMI-166 and CPT-11 exhibited potent anti-metastatic efficacy without increased hematotoxicity. These results point to the clinical advantage of using MMI-166 in combination with CPT-11.

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.

Anti-angiogenic agents for the treatment of brain tumors

It is accepted that novel therapeutic approaches are needed for the majority of patients with malignant brain tumors. The vascularity of many primary brain tumors and the encouraging preclinical studies suggest that antiangiogenic agents have the potential to become an important component of multimodality treatment of patients with brain tumors. The understanding of the biology of angiogenesis is improving rapidly, offering the hope for more specific vascular targeting of brain tumor neovasculature. Neuroimaging techniques evaluating the angiogenic process and the impact of antiangiogenic agents will be an important tool for the rapid development of these novel therapeutic agents.

Development of matrix metalloproteinase inhibitors in cancer therapy

The matrix metalloproteinases represent an attractive target for cancer treatment, and a number of matrix metalloproteinase inhibitors are undergoing clinical trials. The results of these studies will establish whether any of these compounds are therapeutically useful. Independent of the conclusions from the first generation of studies, the field of matrix metalloproteinase inhibitors remains attractive for creative and innovative research. In the future, the development of novel, less toxic, and more effective matrix metalloproteinase inhibitors, and the combination of conventional agents with these novel anticancer agents will constitute the main focus of research efforts.

Mechanisms and future directions for angiogenesis-based cancer therapies

Targeting angiogenesis represents a new strategy for the development of anticancer therapies. New targets derived from proliferating endothelial cells may be useful in developing anticancer drugs that prolong or stabilize the progression of tumors with minimal systemic toxicities. These drugs may also be used as novel imaging and radiommunotherapeutic agents in cancer therapy. In this review, the mechanisms and control of angiogenesis are discussed. Genetic and proteomic approaches to defining new potential targets on tumor vasculature are then summarized, followed by discussion of possible antiangiogenic treatments that may be derived from these targets and current clinical trials. Such strategies involve the use of endogenous antiangiogenic agents, chemotherapy, gene therapy, antiangiogenic radioligands, immunotherapy, and endothelial cell-based therapies. The potential biologic end points, toxicities, and resistance mechanisms to antiangiogenic agents must be considered as these therapies enter clinical trials.

Matrix metalloproteinases in cancer: prognostic markers and therapeutic targets

Degradation of extracellular matrix is crucial for malignant tumour growth, invasion, metastasis and angiogenesis. Matrix metalloproteinases (MMPs) are a family of zinc-dependent neutral endopeptidases collectively capable of degrading essentially all matrix components. Elevated levels of distinct MMPs can be detected in tumour tissue or serum of patients with advanced cancer and their role as prognostic indicators in cancer is studied. In addition, therapeutic intervention of tumour growth and invasion based on inhibition of MMP activity is under intensive investigation and several MMP inhibitors are in clinical trials in cancer. In this review, we discuss the current view on the feasibility of MMPs as prognostic markers and as targets for therapeutic intervention in cancer.

The role of matrix metalloproteinase genes in glioma invasion: co-dependent and interactive proteolysis

Matrix metalloproteinases (MMPs) are cation-dependent endopeptidases which have been implicated in the malignancy of gliomas. It is thought that the MMPs play a critical role in both metastasis and angiogenesis, and that interference with proteases might therefore deter local tumor dissemination and neovascularization. However, the attempt to control tumor-associated proteolysis will rely on better definition of the normal tissue function of MMPs, an area of study still in its infancy in the central nervous system (CNS). Understanding the role of MMP-mediated proteolysis in the brain relies heavily on advances in other areas of molecular neuroscience, most notably an understanding of extracellular matrix (ECM) composition and the function of cell adhesion molecules such as integrins, which communicate knowledge of ECM composition intracellularly. Recently, protease expression and function has been shown to be strongly influenced by the functional state and signaling properties of integrins. Here we review MMP function and expression in gliomas and present examples of MMP profiling studies in glioma tissues and cell lines by RT-PCR and Western blotting. Co-expression of MMPs and certain integrins substantiates the gathering evidence of a functional intersection between the two, and inhibition studies using recombinant TIMP-1 and integrin antisera demonstrate significant inhibition of glioma invasion in vitro. Use of promising new therapeutic compounds with anti-MMP and anti-invasion effects are discussed. These data underline the importance of functional interaction of MMPs with accessory proteins such as integrins during invasion, and the need for further studies to elucidate the molecular underpinnings of this process.

Suppression of matrix metalloproteinase activity by SI-27: detection by a new activity assay with S-2444, a specific chromogenic peptide

We have previously reported on the anti-invasive and angiosuppressive effects of SI-27, an anti-matrix metalloproteinase (MMP) agent. The molecular mechanism of its anti-MMP action, however, has not yet been determined. The purpose of this study was to investigate the effects of SI-27 on MMP- 1, -2, -3, -9, and TIMP-1, -2 secreted by human glioma cell lines (U87MG, U251MG, U373MG, and Y98G). When cells were exposed to non-cytotoxic concentrations of SI-27 (preliminarily determined by the MTT assay), expressions of mRNAs for the enzymes was not inhibited. For an MMP activity assay, we employed the fact that active MMPs could cleave modified pro-urokinase to form active urokinase, which then acted on S-2444 peptide to create a chromogenic product. Secretion of all pro-MMPs from glioma cells was not significantly reduced by SI-27. However, activation of pro-MMPs was significantly inhibited in a dose-dependent manner ((IC50 values for MMP-2; U87MG, 3.5 microg/ml; U25 IMG, 4.2 microg/ml; U373MG, 4.8 microg/ml; Y98G, 4.0 degreesg/ml); (IC50 values for MMP-9; 251MG, 7.2 microg/ml, U373MG, 2.8 microg/ml). In addition, active MMPs were not inhibited by SI-27. These findings were supported by zymographic analysis and by collagenolysis assay data. TIMP-1 and -2 were also not inactivated by SI-27. These findings suggest that SI-27 targets the activation process of pro-MMP. S-2444, a specific chromogenic peptide, was useful for quantitative analysis of the activity of MMP subtypes in this study.

Mechanisms of tumour invasion and metastasis: emerging targets for therapy

The progression of a tumour from one of benign and delimited growth to one that is invasive and metastatic is the major cause of poor clinical outcome in cancer patients. The invasion and metastasis of tumours is a highly complex and multistep process that requires a tumour cell to modulate its ability to adhere, degrade the surrounding extracellular matrix, migrate, proliferate at a secondary site and stimulate angiogenesis. Knowledge of the process has greatly increased and this has resulted in the identification of a number of molecules that are fundamental to the process. The involvement of these molecules has been shown to relate not only to the survival and proliferation of the tumour cell but, also to the processes of tumour cell adhesion, migration, and the tumour cells ability to degrade and escape the primary site as well as play a role in angiogenesis. These molecules may provide important therapeutic targets that represent the ability to target specific steps in the process of invasion and metastasis and provide additional therapies. The review focuses on representative key targets in each of these processes and summarises the state of play in each case.

Complex roles of tissue inhibitors of metalloproteinases in cancer

Matrix metalloproteinases (MMPs) is tightly associated with extracellular matrix (ECM) turnover, which plays a very active role in tumor invasion and metastasis. Tissue inhibitors of metalloproteinases (TIMPs) plays a critical role in the homeostasis of ECM by regulating the activity of MMPs. TIMPs are well-known for their ability to inhibit MMP activity thereby inhibiting tumor growth and metastasis. However, many evidences suggest that TIMPs are multifunctional proteins, which regulate cell proliferation, apoptosis, proMMP-2 activation, and angiogenesis. These effects may be through MMP-dependent or MMP-independent pathways. Recent data indicate that TIMPs have many paradoxical roles in tumorigenesis. In particular, both inhibitory effect and stimulatory effect on tumorigenesis have been demonstrated in many animal models in which TIMPs were overexpressed in cancer cells or in mice. Elevated TIMP levels are reported in association with cancer progression and identified as poor prognostic indicators in several human tumor types. Herein, we review the complex roles of TIMPs in cancer growth and metastasis.

Anti-angiogenic effects of the thienopyridine SR 25989 in vitro and in vivo in a murine pulmonary metastasis model

Neovascularisation is a key step in tumour growth and establishment of distant metastases. We have recently demonstrated that the thienopyridine SR 25989 an enantiomer of the anti-aggregant clopidogrel (Plavix) lacking anti-aggregant activity, inhibits endothelial cell proliferation in vitro by increasing the expression of endogenous thrombospondin-1, a natural potent inhibitor of angiogenesis. The anti-angiogenic effect of SR 25989 was further assessed in vitro in a quantitative assay of angiogenesis comprising a fragment of rat aorta embedded in a fibrin gel and in vivo in a pulmonary metastatic model using C57BL/6 mice inoculated in the foot pad with the highly metastatic melanoma cell line B16 F10. SR 25989 induced a dose dependent inhibition of spontaneous microvessel development in vitro reaching half maximal inhibition at around less than 50 microM and caused platelet derived growth factor induced angiogenesis to regress as a function of thienopyridine concentration. In vivo, SR 25989 did not alter significantly the growth rate of the primary tumour in the foot pad and did not inhibit development of inguinal nodes which appeared after amputation. However, the number and size of lung metastases were reduced in treated animals when examined at the time of sacrifice. In addition, the few metastases over 1 mm3 did not show any neovascularisation, as confirmed by negative von Willebrand immunostaining and in contrast to intense vascularisation seen in metastases developed by control mice. These results confirm that SR 25989 possesses potent anti-angiogenic properties and is able to inhibit metastatic dissemination and growth. The lack of effect on the primary tumour and inguinal nodes illustrates the complexity of the mechanisms involved in tumoural neo-angiogenesis and points out the possibility for distinct processes leading to neovascularisation in primary tumour as opposed to metastases.

SI-27, a novel inhibitor of matrix metalloproteinases with antiangiogenic activity: detection with a variable-pressure scanning electron microscope

OBJECTIVE

Degradation of basement membrane is one the of crucial steps in tumor angiogenesis and is performed by matrix metalloproteinases (MMPs). This study was designed to investigate the suppression of tumor angiogenesis by SI-27, an MMP inhibitor.

METHODS

SI-27 was applied at noncytotoxic concentrations (1-100 micromol/L), and its effect on nonmitogenic vascular endothelial growth factor (VEGF)-enhanced cell motility and in vitro angiogenesis by human umbilical vein endothelial cells was determined. The activity of MMP-1, MMP-2, and tissue inhibitor of metalloproteinase 1 was determined by enzyme-linked immunosorbent assay. The effect of SI-27 on in vitro angiogenesis stimulated by supernatants of human glioma cell lines (U87MG, U251MG, and U373MG) also was examined. Angiogenesis was detected with variable vacuum scanning electron microscopy.

RESULTS

Cell motility and in vitro angiogenesis by human umbilical vein endothelial cells were significantly increased by VEGF. The maximal effect on cell motility by VEGF was noted at 5 ng/ml (P < 0.001), and the maximal effect on the capillary network was observed at 10 ng/ml (P < 0.001), along with elevated MMP-1 and MMP-2 activity. Whereas SI-27 significantly suppressed VEGF-mediated in vitro angiogenesis (50 micromol/L; P < 0.001) and inactivated both MMP-1 and MMP-2, the expression of tissue inhibitor of metalloproteinase 1 and VEGF-mediated cell motility were not affected by SI-27. The angiogenesis promoted by glioma supernatants showed a significant reduction in the presence of SI-27 (10 micromol/L; U87MG, P < 0.01; U251MG, P < 0.01; U373MG, P < 0.01).

CONCLUSION

SI-27 inhibited in vitro tumor angiogenesis by suppression of MMP. This agent may be anticipated to prevent tumor growth through an angiosuppressive effect.

Envelope gene-mediated neurovirulence in feline immunodeficiency virus infection: induction of matrix metalloproteinases and neuronal injury

The release of neurotoxins by activated brain macrophages or microglia is one mechanism proposed to contribute to the development of neurological disease following infection by lentiviruses, including feline immunodeficiency virus (FIV). Since molecular diversity in the lentiviral envelope gene influences the expression of host molecules implicated in neuronal injury, the role of the envelope sequence in FIV neuropathogenesis was investigated by using the neurovirulent FIV strain V1CSF, the nonneurovirulent strain Petaluma, and a chimera (FIVCh) containing the V1CSF envelope gene in a Petaluma background. All three viruses replicated in primary feline macrophages with equal efficiency, but conditioned medium from V1CSF- or FIVCh-infected cells was significantly more neurotoxic than medium from Petaluma-infected cultures (P < 0.001) and could be attenuated in a dose-dependent manner by treatment with either the matrix metalloproteinase (MMP) inhibitor prinomastat (PMT) or function-blocking antibodies to MMP-2. Although FIV sequences were detectable by PCR in brain tissue from neonatal cats infected with each of the viral strains, immunohistochemistry revealed increased astrogliosis and macrophage activation in the brains of V1CSF- and FIVCh-infected cats relative to the other groups, together with elevated markers of neuronal stress that included morphological changes and increased c-fos immunoreactivity. Similarly, MMP-2, but not MMP-9, mRNA and protein expression was increased in brain tissues of V1CSF- and FIVCh-infected cats relative to Petaluma-infected animals (P < 0.01). Infection with V1CSF or FIVCh was also associated with greater CD4(+) cell depletion (P < 0.001) and neurodevelopmental delays (P < 0.005), than in Petaluma-infected animals; these deficits improved following PMT therapy. These findings indicated that diversity in the envelope gene sequence influenced the neurovirulence exhibited by FIV both in vitro and in vivo, possibly through a mechanism involving the differential induction of MMP-2.

The effect of prinomastat (AG3340), a synthetic inhibitor of matrix metalloproteinases, on uveal melanoma rabbit model

PURPOSE

We studied the effects of intravitreally administered prinomastat on the take rate and growth of uveal melanoma after xenograft implantation in rabbit uveal melanoma model.

METHODS

Uveal melanoma xenograft was implanted to suprachoroidal space in each eye of 24 pigmented rabbits which were immunosuppressed with cyclosporine. One week after surgery, the eyes were randomized to receive prinomastat or the vehicle of the prinomastat intravitreally every week for 4 weeks. The take rate of the xenograft, tumor height, apoptosis, and necrosis in the eyes which developed tumors from the treatment and control groups were compared.

RESULTS

A tumor mass was identified in 8 of 24 (33%) prinomastat-treated eyes and 20 of 24 (83%) of the vehicle-treated eyes. Echographic measurements revealed a mean tumor height of 2.2 mm in the prinomastat-treated group and 3.8 mm in the control group in those eyes with take of tumor (p < 0.001). Stereomicroscopic measurements showed a mean tumor height of 1.9 mm in the treatment group and 3.9 mm in the control group (p < 0.001). The mean number of apoptotic nuclei detected per mm(2) of the histologic section in the non-necrotic tumor was 8.12 in the prinomastat-treated group and 0.57 in the control group (p < 0.001). Evaluation of the digital images in microscopic sections of the tumors on histologic slides revealed 29.6% necrosis in prinomastat-treated eyes as compared to 10.9% in vehicle-treated eyes (p = 0.003).

CONCLUSIONS

These results suggest that prinomastat treatment significantly reduces the take rate and the growth rate of xenograft in uveal melanoma rabbit model.

Matrix metalloproteinases in the progression of heart failure: potential therapeutic implications

Matrix metalloproteinases (MMPs) are a family of functionally related zinc-containing enzymes that denature and degrade fibrillar collagens and other components of the extracellular matrix. Myocardial extracellular matrix remodelling and fibrosis regulated by MMPs are believed to be important contributors to the progression of heart failure. The role of MMPs in cardiac fibrosis and the progression of heart failure, along with the possibility of halting the progression of heart failure by modulating extracellular matrix remodelling are important issues under intense study. MMPs are increased in the failing hearts of both animal models and patients with heart failure. MMP inhibition may therefore modulate extracellular matrix remodelling and the progression of heart failure. It is a great advantage that various MMP inhibitors have been developed initially for the treatment of cancer, arthritis and other diseases believed to be associated with increased MMP activity. Several preclinical studies have shown that treatment of heart failure in animal models with MMP inhibitors results in less collagen matrix damage, favourable extracellular matrix remodelling, and improved cardiac structure and function. The results suggest that modulation of MMP activity can prevent myocardial dysfunction and the progression of heart failure through alterations in the remodelling process of extracellular matrix and the left ventricle. Although these promising results suggest potential benefits of MMP inhibition for human heart failure, no clinical data evaluating MMP inhibitors in heart failure have been reported. As the preclinical evidence continues to grow and the potential of MMP inhibition for the treatment of heart failure continues to unfold, MMP inhibition may prove to be an effective treatment for heart failure.

Motuporamines, anti-invasion and anti-angiogenic alkaloids from the marine sponge Xestospongia exigua (Kirkpatrick): isolation, structure elucidation, analogue synthesis, and conformational analysis

Extracts of the sponge Xestospongia exigua collected in Papua New Guinea were positive in a new assay for anti-invasion activity. Bioassay-guided fractionation led to the identification of the three known motuporamines A (1), B (2), and C (3) along with the new motuporamines D (4), E (5), and F (6) and a mixture of G, H, and I (15). Motuporamines A (1), B (2), and C (3) and the mixture of G, H, and I (15) were responsible for the anti-invasion activity of the crude extract. Motuporamine C (3) has also been found to be anti-angiogenic. A series of analogues of the motuporamines have been synthesized and evaluated for anti-invasive activity. These SAR results revealed that a saturated 15-membered cyclic amine fused to the natural motuporamine diamine side chain (13) represented the optimal structure for anti-invasive activity in this family. Single-crystal X-ray diffraction analysis of one of the analogues 20 showed that in the solid state its 16-membered macrocyclic amine fragment adopted the [4444] quadrangular conformation predicted by calculations to be the lowest energy conformation for the corresponding cycloalkane, cyclohexadecane. These data along with literature X-ray data and conformational analysis for derivatives of azacyclotridecane have been used as precedents for predicting the lowest energy ring conformations of other motuporamines. The SAR data from the natural and synthetic motuporamines have been combined with the conformational analyses to provide an outline of the functionality and shape required for activity in this family of alkaloids and to design a new analogue 49 that showed good anti-invasion activity.

Matrix metalloproteinase inhibitors: current developments and future perspectives

Malignant tumors are characterized by invasive growth and metastasis. To facilitate this invasive behavior, the enzymatic breakdown of the extracellular matrix (ECM) is a prerequisite. Many human tumors are characterized by locally increased concentrations of matrix metalloproteinases (MMPs), enzymes that are able to degrade this ECM. A vast number of matrix metalloproteinase inhibitors (MMPIs) have been developed in recent years and after extensive preclinical testing, the results of the first clinical studies with several of these compounds have recently been presented. In this review we will describe some of the basic concepts of the degradation of the ECM, with special emphasis on the role of MMPs in the progression of cancer. Furthermore we will review the results of preclinical and clinical studies with MMPIs and discuss their future perspective.

Aerosol delivery of PEI-p53 complexes inhibits B16-F10 lung metastases through regulation of angiogenesis

Inhibition of pulmonary metastases poses a difficult clinical challenge for current therapeutic regimens. We have developed an aerosol system utilizing a cationic polymer, polyethyleneimine (PEI), for topical gene delivery to the lungs as a novel approach for treatment of lung cancer. Using a B16-F10 murine melanoma model in C57BL/6 mice, we previously demonstrated that aerosol delivery of PEI-p53 DNA resulted in highly significant reductions in the tumor burden (P < .001) in treated animals, and also lead to about 50% increase in the mean length of survival of the mice-bearing B16-F10 lung tumors. The mechanisms of this antitumor effect of p53 are investigated in this report. Here, we demonstrate that the p53 transfection leads to an up-regulation of the antiangiogenic factor thrombospondin-1 (TSP-1) in the lung tissue and the serum of the mice. Furthermore, there is a down-regulation of vascular endothelial growth factor (VEGF) in the lung tissue and serum of the B16-F10 tumor-bearing mice treated with PEI-p53 DNA complexes, compared with untreated tumor-bearing animals. In addition, staining for von Willebrand factor (vWF), a marker for the angiogenic blood vessels, revealed that p53 treatment leads to a decrease in the angiogenic phenotype of the B16-F10 tumors. Immunohistochemistry for transgene expression reveals that the PEI-p53 aerosol complexes transfect mainly the epithelial cells lining the airways, with diffuse transfection in the alveolar lining cells, as well as, the tumor foci in the lung tissue. There was also some evidence of apoptosis in the lung tumor foci of animals treated with p53. The data suggest that aerosol delivery of PEI-p53 complexes leads to inhibition of B16-F10 lung metastases, in part by suppression of angiogenesis.

Proteases and the biology of glioma invasion

Despite optimal clinical treatment, the prognosis for malignant gliomas remains poor. One of the primary reasons for treatment failure is not diffuse dissemination, but local invasion. Recently, there has been an increase in information regarding specific molecules that determine the aggressiveness and invasion potential of high-grade astrocytic tumors. In particular, expression of matrix metalloproteases in high-grade gliomas appears to correlate with tissue invasiveness. It is the purpose of the present review to describe the connection between alterations in growth-related genes, protease activity, and tumor biology, and how these connections may suggest potential novel therapeutic targets.

Sulfated polysaccharides increase plasma levels of SDF-1 in monkeys and mice: involvement in mobilization of stem/progenitor cells

It was previously reported that treatment with the sulfated polysaccharide fucoidan or the structurally similar dextran sulfate increased circulating mature white blood cells and hematopoietic progenitor/stem cells (HPCs) in mice and nonhuman primates; however, the mechanism mediating these effects was unclear. It is reported here that plasma concentrations of the highly potent chemoattractant stromal-derived factor 1 (SDF-1) increase rapidly and dramatically after treatment with fucoidan in monkeys and in mice, coinciding with decreased levels in bone marrow. In vitro and in vivo data suggest that the SDF-1 increase is due to its competitive displacement from heparan sulfate proteoglycans that sequester the chemokine on endothelial cell surfaces or extracellular matrix in bone marrow and other tissues. Although moderately increased levels of interleukin-8, MCP1, or MMP9 were also present after fucoidan treatment, studies in gene-ablated mice (GCSFR(-/-), MCP1(-/-), or MMP9(-/-)) and the use of metalloprotease inhibitors do not support their involvement in the concurrent mobilization. Instead, SDF-1 increases, uniquely associated with sulfated glycan-mobilizing treatments and not with several other mobilizing agents tested, are likely responsible. To the authors' knowledge, this is the first published report of disrupting the SDF-1 gradient between bone marrow and peripheral blood through a physiologically relevant mechanism, resulting in mobilization with kinetics similar to other mobilizing CXC chemokines. The study further underscores the importance of the biological roles of carbohydrates.

Scaling down imaging: molecular mapping of cancer in mice

The development of miniaturized imaging equipment and reporter probes has improved our ability to study animal models of disease, such as transgenic and knockout mice. These technologies can now be used to continuously monitor in vivo tumour development, the effects of therapeutics on individual populations of cells, or even specific molecules. If these techniques prove effective in mice, they might be translated into the clinic in the future, where they could be used to non-invasively detect and monitor treatment of human cancers.

Matrix metalloproteinase-9 and vascular endothelial growth factor: a possible link in adult T-cell leukaemia cell invasion

Plasma from a total of 57 patients with adult T-cell leukaemia (ATL) (acute ATL, 39 patients; lymphoma ATL, one patient; chronic ATL, 15 patients; smouldering ATL, two patients) and 20 healthy controls was analysed for the presence of type IV gelatinase activity with clinical features. A significant elevation of plasma matrix metalloproteinase-9 (MMP-9) was observed in some ATL patients, particularly in the patients with malignant cell infiltration. MMP-9 was found to be secreted into the conditioned medium from all ATL cell lines examined. Moreover, the corresponding mRNA was detectable both in all ATL cell lines examined and in the majority of primary acute ATL cells, indicating that ATL cells are capable of synthesizing and secreting MMP-9. We previously demonstrated that a high incidence of ATL cell infiltration was closely related to a high plasma level of vascular endothelial growth factor (VEGF) produced by ATL cells themselves. This present study showed that the presence of increased plasma MMP-9 was closely associated with elevated plasma VEGF in ATL patients. Furthermore, we showed that both increased plasma MMP-9 and VEGF were significantly related to high ATL cell infiltration. All these findings strongly suggest that MMP-9 and VEGF act co-operatively in the process of ATL cell invasion.

Ventilator-induced lung injury upregulates and activates gelatinases and EMMPRIN: attenuation by the synthetic matrix metalloproteinase inhibitor, Prinomastat (AG3340)

Mechanical ventilation has become an indispensable therapeutic modality for patients with respiratory failure. However, a serious potential complication of MV is the newly recognized ventilator-induced acute lung injury. There is strong evidence suggesting that matrix metalloproteinases (MMPs) play an important role in the development of acute lung injury. Another factor to be considered is extracellular matrix metalloproteinase inducer (EMMPRIN). EMMPRIN is responsible for inducing fibroblasts to produce/secrete MMPs. In this report we sought to determine: (1) the role played by MMPs and EMMPRIN in the development of ventilator-induced lung injury (VILI) in an in vivo rat model of high volume ventilation; and (2) whether the synthetic MMP inhibitor Prinomastat (AG3340) could prevent this type of lung injury. We have demonstrated that high volume ventilation caused acute lung injury. This was accompanied by an upregulation of gelatinase A, gelatinase B, MT1-MMP, and EMMPRIN mRNA demonstrated by in situ hybridization. Pretreatment with the MMP inhibitor Prinomastat attenuated the lung injury caused by high volume ventilation. Our results suggest that MMPs play an important role in the development of VILI in rat lungs and that the MMP-inhibitor Prinomastat is effective in attenuating this type of lung injury.

Novel pharmacological agents in clinical development for solid tumours

For decades, cancer therapy has focused on DNA-directed mechanisms of cytotoxicity, utilising agents with limited efficacy and significant toxicity. Recent advances in tumour biology have elucidated the molecular pathways implicated in the pathogenesis and progression of cancers and have resulted in the discovery of a variety of novel molecular targets for therapeutic intervention. Promising novel agents targeting signal transduction pathways, cell cycle regulation, angiogenesis and apoptosis are in clinical testing and are discussed in this review.

New molecular targets and biological therapies in sarcomas

The treatment of patients with soft tissue and bone sarcomas has dramatically improved over the last decade. This improvement has been brought about through advances in diagnosis, surgical techniques, conformal radiotherapy, and combination chemotherapy. Further advances in the management of the diverse spectrum of sarcoma patients will reflect tailoring of therapy based on molecular abnormalities. The role of cytogenetics and molecular analysis of fusion or mutated genes in diagnosis, prognosis, and design of biological treatments is discussed. An example of this approach has been the recent success in treatment of patients with gastrointestinal stromal tumours expressing mutant c-kit with a specific tyrosine kinase inhibitor, STI571. Molecular rearrangements may also serve as targets for designing specific immunotherapies with the fusion gene product. The use of biological therapies with signal transduction inhibitors, angiogenesis inhibitors, matrix metalloproteinase inhibitors, immunotherapy, differentiation inducers, and gene therapy could complement existing treatments for long-term control of disease. As these newer biological agents take form, clinical trial design will undergo change to reflect the chronic nature of these therapies.

Optical imaging of matrix metalloproteinase-2 activity in tumors: feasibility study in a mouse model

PURPOSE

To develop an optical imaging method to determine the expression level of tumoral matrix metalloproteinase-2 (MMP-2) in vivo.

MATERIALS AND METHODS

An optical contrast agent was developed that was highly activatable by means of MMP-2-induced conversion. Signal characteristics of the probe were quantified ex vivo with a recombinant enzyme. Animal tumor models were established with MMP-2-positive (human fibrosarcoma cell line, n = 4) and MMP-2-negative (well-differentiated mammary adenocarcinoma, n = 4) tumor cell lines. Both tumors were implanted into nude mice and were optically imaged after intravenous administration of the MMP-2-sensitive probe.

RESULTS

The MMP-2-sensitive probe was activated by MMP-2 in vitro, producing up to an 850% increase in near-infrared fluorescent signal intensity. This activation could be blocked by MMP-2 inhibitors. MMP-2-positive tumors were easily identified as high-signal-intensity regions as early as 1 hour after intravenous injection of the MMP-2 probe, while contralateral MMP-2-negative tumors showed little to no signal intensity. A nonspecific control probe showed little to no activation in MMP-2-positive tumors.

CONCLUSION

It is feasible to image MMP-2 enzyme activity in vivo by using near-infrared optical imaging technology and "smart" matrix metalloproteinase-sensitive probes.

Matrix metalloproteinase inhibitors: past lessons and future prospects in breast cancer

The matrix metalloproteinases (MMPs) play a central role in invasion and metastasis. However, despite striking activity in preclinical models, the clinical development of the matrix metalloproteinase inhibitors (MMPIs) has been difficult. The results of important phase III trials are now emerging and it is therefore opportune to review the current state of the MMPIs. In this article the evidence for the role of MMPs in the progression of breast cancer, the development of the MMPIs and the recent phase III results are discussed. Despite the problems encountered it is hoped that the MMPIs may yet provide another mechanism for the long-term control of micrometastatic disease. Furthermore, important lessons can be learnt from their development that are relevant to the development of other biological agents.

Inhibition of tumor angiogenesis by non-steroidal anti-inflammatory drugs: emerging mechanisms and therapeutic perspectives

Chronic intake of non steroidal anti-inflammatory drugs (NSAIDs) is associated with a reduced risk of developing gastrointestinal tumors, in particular colon cancer. Increasing evidence indicates that NSAID exert tumor-suppressive activity on pre-malignant lesions (polyps) in humans and on established experimental tumors in mice. Some of the tumor-suppressive effects of NSAIDs depend on the inhibition of cyclooxygenase-2 (COX-2), a key enzyme in the synthesis of prostaglandins and thromboxane, which is highly expressed in inflammation and cancer. Recent findings indicate that NSAIDs exert their anti-tumor effects by suppressing tumor angiogenesis. The availability of COX-2-specific NSAIDs opens the possibility of using this drug class as anti-angiogenic agents in combination with chemotheapy or radiotherapy for the treatment of human cancer. Here we will briefly review recent advances in the understanding of the mechanism by which NSAIDs suppress tumor angiogenesis and discuss their potential clinical application as anti-cancer agents.

Tumor angiogenesis as a therapeutic target

Angiogenesis - the formation of new blood vessels within a tumor (or many other tissue types) - has become a hotbed of pharmacological research as well as industrial drug discovery. This is the result of the efforts of a generation of scientists elucidating the complex (patho)physiological, biochemical and molecular events accompanying angiogenesis. It is estimated that >300 drug candidates are currently in various stages of testing, and it is, therefore, impossible to capture all of this in a brief review. Therefore, the emphasis here is on relatively advanced projects that are either in preclinical or clinical development, thus neglecting, to a large extent, the many exciting avenues being pursued in both academic and biotechnology laboratories. Although the potential of the approaches described cannot be overestimated, it is also important to note that there is still no drug on the market that achieves clinical benefit based on a selective modulation or inhibition of angiogenesis.

Structure-based design and synthesis of potent matrix metalloproteinase inhibitors derived from a 6H-1,3,4-thiadiazine scaffold

We describe a new generation of heterocyclic nonpeptide matrix metalloproteinase (MMP) inhibitors derived from a 6H-1,3,4-thiadiazine scaffold. A screening effort was utilized to identify some chiral 6-methyl-1,3,4-thiadiazines that are weak inhibitors of the catalytic domain of human neutrophil collagenase (cdMMP-8). Further optimization of the lead compounds revealed general design principles that involve the placement of a phenyl or thienyl group at position 5 of the thiadiazine ring, to improve unprimed side affinity; the incorporation of an amino group at position 2 of the thiadiazine ring as the chelating agent for the catalytic zinc; the placement of a N-sulfonamide-substituted amino acid residue at the amino group, to improve primed side affinity; and the attachment of diverse functional groups at position 4 or 5 of the phenyl or thienyl group at the unprimed side, to improve selectivity. The new compounds were assayed against eight different matrix metalloproteinases, MMP-1, cdMMP-2, cdMMP-8, MMP-9, cdMMP-12, cdMMP-13, cdMMP-14, and the ectodomain of MMP-14, respectively. A unique combination of the above-described modifications produced the selective inhibitor (2R)-N-[5-(4-bromophenyl)-6H-1,3,4-thiadiazin-2-yl]-2-[(phenylsulfonyl)amino]propanamide with high affinity for MMP-9 (K(i) = 40 nM). X-ray crystallographic data obtained for cdMMP-8 cocrystallized with N-allyl-5-(4-chlorophenyl)-6H-1,3,4-thiadiazin-2-amine hydrobromide gave detailed design information on binding interactions for thiadiazine-based MMP inhibitors.

Association of increased phosphatidylinositol 3-kinase signaling with increased invasiveness and gelatinase activity in malignant gliomas

OBJECT

Glioblastoma multiforme is the most malignant of the primary brain tumors and aggressively infiltrates surrounding brain tissue, resulting in distant foci within the central nervous system, thereby rendering this tumor surgically incurable. The recent findings that both phosphatidylinositol 3-kinase (PI 3-K) and the phosphatase and tensin homolog (PTEN) regulate tumor cell invasiveness have led the authors to surmise that these lipid signaling molecules might play a role in regulating matrix metalloproteinases (MMPs), which are essential for tumor cell invasion.

METHODS

Using the C6 glioma cell line, which does not express measurable amounts of PTEN protein and in which in vitro invasiveness is MMP dependent, the authors determined that in vitro glioma cell invasiveness was significantly reduced when cells were preincubated overnight with LY294002 or wortmannin, two specific inhibitors of PI 3-K signaling. Next, using gelatin zymography, it was noted that these compounds significantly inhibited MMP-2 and MMP-9 activities. Moreover, the decrease in MMP activity correlated with the decrease in PI 3-K activity, as assessed by Akt phosphorylation. Finally, using semiquantitative reverse transcriptase-polymerase chain reaction, the authors demonstrated that LY294002 decreased messenger (m)RNA levels for both MMPs. Thus, these in vitro data indicate that PI 3-K signaling modulates gelatinase activity at the level of mRNA. Using immunostaining of phosphorylated Akt (p-Akt) as a measure of PI 3-K activity, the authors next assessed rat brains implanted with C6 cells. Compared with surrounding brain, there was marked p-Akt staining in C6 glioma cells and in neurons immediately adjacent to the tumor, but not in normal brain. The p-Akt staining in tumors was especially intense in perivascular areas. Using double-labeling techniques, colocalization of p-Akt with MMP-2 and MMP-9 was also noted in perivascular tumor areas.

CONCLUSIONS

The increase in p-Akt staining within these PTEN-deficient gliomas is consistent with what would be predicted from unchecked PI 3-K signaling. Furthermore, the immunohistochemically detected colocalization of p-Akt and MMP-2 and MMP-9 supports the authors' in vitro studies and the proposed linkage between PI 3-K signaling and MMP activity in gliomas.

Matrix metalloproteinase 9, apoptosis, and vascular morphology in early arthritis

OBJECTIVE

To examine matrix metalloproteinase 9 (MMP-9) in the synovial fluid (SF) and synovial membrane (SM) in relation to vascular endothelial cell (EC) apoptosis, vascular endothelial growth factor (VEGF), and SM vascular pattern.

METHODS

Thirty-four patients underwent needle arthroscopy of the knee joint; 12 had early rheumatoid arthritis (RA), 12 had early psoriatic arthritis (PsA), and 10 had osteoarthritis (OA). The early RA and early PsA patients were matched for disease activity. SF levels of MMP-9 and VEGF were measured by an enzyme-linked immunosorbent assay, and EC apoptosis was measured by TUNEL assay. MMP-9 expression was examined in SM by immunohistochemistry. Synovial tissue explants were stimulated with VEGF, and MMP-9 levels were measured in the supernatants. The synovial vascular pattern was recorded.

RESULTS

SF MMP-9 levels were significantly higher in early PsA patients than in early RA patients; OA patients had minimal levels. MMP-9 levels correlated with blood vessel morphology and SF VEGF levels. MMP-9 expression was greater in early PsA SM than in early RA SM, but the difference was not significant. In contrast however, EC apoptosis was greater in early RA SM than in early PsA SM. MMP-9 levels increased 2-fold and 9-fold, respectively, in SM explant culture supernatants on day 7 in response to stimulation with 25 ng/ml and 50 ng/ml of VEGF.

CONCLUSION

SF MMP-9 levels correlate with the pattern of SM neovascularization and SF VEGF levels in early inflammatory arthritis, and VEGF increases MMP-9 production by SM. Endothelial cell apoptosis, however, appears to be more prevalent in early RA. This combination of factors may explain the pattern of differential angiogenesis in these arthritides.