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

A quantitative structure-activity relationship study on matrix metalloproteinase inhibitors: Piperidine sulfonamide aryl hydroxamic acid analogs

A quantitative structure-activity relationship (QSAR) study has been made on a series of piperidine sulfonamide aryl hydroxamic acid analogs acting as matrix metalloproteinase (MMP) inhibitors. The inhibitory potencies of the compounds against two MMPs, MMP-2 and MMP-13, are found to be significantly correlated with the hydrophobic properties of the molecules, suggesting that in both enzymes the hydrophobic interaction is playing a dominant role.

Pharmacoproteomics of a metalloproteinase hydroxamate inhibitor in breast cancer cells: dynamics of membrane type 1 matrix metalloproteinase-mediated membrane protein shedding

Broad-spectrum matrix metalloproteinase (MMP) inhibitors (MMPI) were unsuccessful in cancer clinical trials, partly due to side effects resulting from limited knowledge of the full repertoire of MMP substrates, termed the substrate degradome, and hence the in vivo functions of MMPs. To gain further insight into the degradome of MMP-14 (membrane type 1 MMP) an MMPI, prinomastat (drug code AG3340), was used to reduce proteolytic processing and ectodomain shedding in human MDA-MB-231 breast cancer cells transfected with MMP-14. We report a quantitative proteomic evaluation of the targets and effects of the inhibitor in this cell-based system. Proteins in cell-conditioned medium (the secretome) and membrane fractions with levels that were modulated by the MMPI were identified by isotope-coded affinity tag (ICAT) labeling and tandem mass spectrometry. Comparisons of the expression of MMP-14 with that of a vector control resulted in increased MMP-14/vector ICAT ratios for many proteins in conditioned medium, indicating MMP-14-mediated ectodomain shedding. Following MMPI treatment, the MMPI/vehicle ICAT ratio was reversed, suggesting that MMP-14-mediated shedding of these proteins was blocked by the inhibitor. The reduction in shedding or the release of substrates from pericellular sites in the presence of the MMPI was frequently accompanied by the accumulation of the protein in the plasma membrane, as indicated by high MMPI/vehicle ICAT ratios. Considered together, this is a strong predictor of biologically relevant substrates cleaved in the cellular context that led to the identification of many undescribed MMP-14 substrates, 20 of which we validated biochemically, including DJ-1, galectin-1, Hsp90alpha, pentraxin 3, progranulin, Cyr61, peptidyl-prolyl cis-trans isomerase A, and dickkopf-1. Other proteins with altered levels, such as Kunitz-type protease inhibitor 1 and beta-2-microglobulin, were not substrates in biochemical assays, suggesting an indirect affect of the MMPI, which might be important in drug development as biomarkers or, in preclinical phases, to predict systemic drug actions and adverse side effects. Hence, this approach describes the dynamic pattern of cell membrane ectodomain shedding and its perturbation upon metalloproteinase drug treatment.

Molecular profiling of angiogenesis with targeted ultrasound imaging: early assessment of antiangiogenic therapy effects

Molecular ultrasound is capable of elucidating the expression of angiogenic markers in vivo. However, the capability of the method for volumetric "multitarget quantification" and for the assessment of antiangiogenic therapy response has rather been investigated. Therefore, we generated cyanoacrylate microbubbles linked to vascular endothelial growth factor receptor 2 (VEGFR2) and alphavbeta3 integrin binding ligands and quantified their accumulation in squamous cell carcinoma xenografts (HaCaT-ras-A-5RT3) in mice with the quantitative volumetric ultrasound scanning technique, sensitive particle acoustic quantification. Specificity of VEGFR2 and alphavbeta3 integrin binding microbubbles was shown, and changes in marker expression during matrix metalloproteinase inhibitor treatment were investigated. In tumors, accumulation of targeted microbubbles was significantly higher compared with nonspecific ones and could be inhibited competitively by addition of the free ligand in excess. Also, multimarker imaging could successfully be done during the same imaging session. Molecular ultrasound further indicated a significant increase of VEGFR2 and alphavbeta3 integrin expression during tumor growth and a considerable decrease in both marker densities after matrix metalloproteinase inhibitor treatment. Histologic data suggested that the increasing VEGFR2 and alphavbeta3 integrin concentrations in tumors during growth are related to an up-regulation of its expression by the endothelial cells, whereas its decrease under therapy is more related to the decreasing relative vessel density. In conclusion, targeted ultrasound appears feasible for the longitudinal molecular profiling of tumor angiogenesis and for the sensitive assessment of therapy effects in vivo.

Specific inhibition of autoimmune T cell transmigration contributes to beta cell functionality and insulin synthesis in non-obese diabetic (NOD) mice

Human diabetes mellitus (IDDM; type I diabetes) is a T cell-mediated disease that is closely modeled in non-obese diabetic (NOD) mice. The pathogenesis of IDDM involves the transmigration of autoimmune T cells into the pancreatic islets and the subsequent destruction of insulin-producing beta cells. Therapeutic interventions leading to beta cell regeneration and the reversal of established IDDM are exceedingly limited. We report here that specific inhibition of T cell intra-islet transmigration by using a small molecule proteinase inhibitor restores beta cell functionality, increases insulin-producing beta cell mass, and alleviates the severity of IDDM in acutely diabetic NOD mice. As a result, acutely diabetic NOD mice do not require insulin injections for survival for a significant time period, thus providing a promising clue to effect IDDM reversal in humans. The extensive morphometric analyses and the measurements of both the C-peptide blood levels and the proinsulin mRNA levels in the islets support our conclusions. Diabetes transfer experiments suggest that the inhibitor specifically represses the T cell transmigration and homing processes as opposed to causing immunosuppression. Overall, our data provide a rationale for the pharmacological control of the T cell transmigration step in human IDDM.

MMP-9 short interfering RNA induced senescence resulting in inhibition of medulloblastoma growth via p16(INK4a) and mitogen-activated protein kinase pathway

The involvement of matrix metalloproteinases (MMP) has been suggested in cellular mechanisms leading to medulloblastoma, the most common malignant brain tumor in children. A significant association of the expression levels of MMP-9 with survival and M stage suggests that patients with medulloblastoma metastatic disease at diagnosis may benefit from the anti-MMP therapy. Here, we have evaluated the tumorigenicity of medulloblastoma cells after infection with an adenovirus containing a 21-bp short interfering RNA sequence of the human MMP-9 gene (Ad-MMP-9). Infection of Daoy medulloblastoma cells with Ad-MMP-9 reduced MMP-9 activity and protein levels compared with parental and Ad-SV controls. Ad-MMP-9 decreased the number of viable Daoy cells in a concentration-dependent manner. Fluorescence-activated cell sorting analysis indicated that Ad-MMP-9 infection caused a dose-dependent cell cycle arrest in the G(0)-G(1) phase. Ad-MMP-9-induced cell cycle arrest seems to be mediated by the extracellular signal-regulated kinase/mitogen-activated protein kinase pathway and the cell cycle inhibitor p16(INK4a) and is phenotypically indistinguishable from senescence. Ad-MMP-9 treatment inhibited medulloblastoma tumor growth in an intracranial model and was mediated by up-regulation of p16 expression. These studies validate the usefulness of targeting MMP-9 and provide a novel perspective in the treatment of medulloblastoma.

Rapid vascular regrowth in tumors after reversal of VEGF inhibition

Inhibitors of VEGF signaling can block angiogenesis and reduce tumor vascularity, but little is known about the reversibility of these changes after treatment ends. In the present study, regrowth of blood vessels in spontaneous RIP-Tag2 tumors and implanted Lewis lung carcinomas in mice was assessed after inhibition of VEGF receptor signaling by AG-013736 or AG-028262 for 7 days. Both agents caused loss of 50%-60% of tumor vasculature. Empty sleeves of basement membrane were left behind. Pericytes also survived but had less alpha-SMA immunoreactivity. One day after drug withdrawal, endothelial sprouts grew into empty sleeves of basement membrane. Vessel patency and connection to the bloodstream followed close behind. By 7 days, tumors were fully revascularized, and the pericyte phenotype returned to baseline. Importantly, the regrown vasculature regressed as much during a second treatment as it did in the first. Inhibition of MMPs or targeting of type IV collagen cryptic sites by antibody HUIV26 did not eliminate the sleeves or slow revascularization. These results suggest that empty sleeves of basement membrane and accompanying pericytes provide a scaffold for rapid revascularization of tumors after removal of anti-VEGF therapy and highlight their importance as potential targets in cancer therapy.

Amphiphilic triblock copolymer poly(p-dioxanone-co-L-lactide)-block-poly(ethylene glycol), enhancement of gene expression and inhibition of lung metastasis by aerosol delivery

We describe the development of an aerosol system for topical gene delivery to the lungs of C57BL/6 mice. This system is based on the combination of the commercial cationic lipid Lipofectin with a novel amphiphilic triblock copolymer, poly(p-dioxanone-co-L-lactide)-block-poly(ethylene glycol) (PPDO/PLLA-b-PEG, and abbreviated in the text as polymeric micelles). After optimizing conditions for DNA delivery to the lungs of mice using the combination of polymeric micelles with Lipofectin and LacZ DNA, we used the Lipofectin/polymeric micelle system to deliver the tumor suppressor gene PTEN to the lungs of C57BL/6 mice bearing the B16-F10 melanoma. Lipofectin/PTEN/polymeric micelles significantly improved gene expression of PTEN in the lungs of mice with no evidence of cell toxicity or acute inflammation. Importantly, lung metastasis, as measured by lung weight, was significantly reduced (P<0.001), as were total tumor foci in the lungs (P<0.001) and size of individual tumor nodules in animals treated with Lipofectin/PTEN/polymeric micelles compared with control animals. Survival time was also extended. These results suggest that the Lipofectin/polymeric micelle system is appropriate for enhancing gene delivery in vivo and that it can be applied as a non-invasive gene therapy for lung cancer.

Anti-angiogenic drugs: from bench to clinical trials

Angiogenesis, the generation of new capillaries through a process of pre-existing microvessel sprouting, is under stringent control and normally occurs only during embryonic and post-embryonic development, reproductive cycle, and wound repair. However, in many pathological conditions (solid tumor progression, metastasis, diabetic retinopathy, hemangioma, arthritis, psoriasis and atherosclerosis among others), the disease appears to be associated with persistent upregulated angiogenesis. The development of specific anti-angiogenic agents arises as an attractive therapeutic approach for the treatment of cancer and other angiogenesis-dependent diseases. The formation of new blood vessels is a complex multi-step process. Endothelial cells resting in the parent vessels are activated by an angiogenic signal and stimulated to synthesize and release degradative enzymes allowing endothelial cells to migrate, proliferate and finally differentiate to give rise to capillary tubules. Any of these steps may be a potential target for pharmacological intervention. In spite of the disappointing results obtained initially in clinical trials with anti-angiogenic drugs, recent reports with positive results in phases II and III trials encourage expectations in their therapeutic potential. This review discusses the current approaches for the discovery of new compounds that inhibit angiogenesis, with emphasis on the clinical developmental status of anti-angiogenic drugs.

Matrix Metalloproteinase-2 Plays a Critical Role in the Pathogenesis of White Matter Lesions After Chronic Cerebral Hypoperfusion in Rodents

BACKGROUND AND PURPOSE

Cerebrovascular white matter (WM) lesions contribute to cognitive impairment and motor dysfunction in the elderly. A disruption of the blood-brain barrier (BBB) is believed to be a critical early event leading to these WM lesions. Previous studies have suggested the involvement of matrix metalloproteinase-2 (MMP-2) in BBB disruptions and the upregulation of MMP-2 after chronic cerebral hypoperfusion in a rat model. In the present study, we asked whether MMP-2 is involved in the BBB disruption and the subsequent WM lesions after chronic cerebral hypoperfusion.

METHODS

We compared the severity of white matter lesions in rats after chronic cerebral hypoperfusion with or without an MMP inhibitor. Then, we also induced the chronic cerebral hypoperfusion in wild-type and MMP-2-null mice.

RESULTS

In the rats treated with a relatively selective MMP-2 inhibitor, AG3340, the WM lesions after chronic cerebral hypoperfusion were significantly less severe, and the number of activated astroglia and microglia were also significantly lower as compared with the vehicle-treated rats. Gene knockout of MMP-2 also reduced the severity of the WM lesions and the number of activated astroglia and microglia in a mice system. In both rodents, the disruption of BBB function, as assessed by IgM staining and the Evans blue extravasation test, was less severe when MMP-2 activity was attenuated.

CONCLUSIONS

These findings indicate that MMP-2 plays a critical role in the BBB disruption, glial cell activation, and WM lesions after chronic cerebral hypoperfusion and suggest the potential value of MMP-2 inhibitors as a therapeutic tool in cerebrovascular WM lesions.

Mechanistic insights into targeting T cell membrane proteinase to promote islet beta-cell rejuvenation in type 1 diabetes

It has been well established that invasion-promoting membrane type-1 matrix metalloproteinase (MT1-MMP), a multifunctional membrane-tethered enzyme, functions in cancer cells as a mediator of pericellular proteolysis and directly cleaves several cell surface receptors, including CD44. In this report, we confirm that adhesion of diabetogenic T cells promotes the activation of endogenous MT1-MMP. Activated protease then cleaves CD44 in adherent T cells. We have validated that the T cell CD44 receptor is critical for the adhesion of diabetogenic insulin-specific, CD8-positive, K(d)-restricted cells to the matrix as well as for the subsequent transmigration of the adherent T cells through the endothelium and homing of the transmigrated T cells into the pancreatic islets. We have determined that the inhibition of MT1-MMP by low dosages of AG3340 (a subnanomolar range hydroxamate inhibitor of MMPs that has been widely tested in cancer patients) inhibited both T cell MT1-MMP activity and MT1-MMP-dependent shedding of CD44, immobilized T cells on the endothelium, repressed the homing of diabetogenic T cells into the pancreatic islets, reduced insulitis and mononuclear cell infiltration, and promoted either the recovery or the rejuvenation of the functional insulin-producing beta cells in diabetic NOD mice with freshly developed type I diabetes (IDDM). We believe our data constitute a mechanistic and substantive rationale for clinical trials of selected MT1-MMP inhibitors in the therapy of IDDM in humans.

New Pharmacologic Approaches to Therapy for Age-Related Macular Degeneration

As a result of a better understanding of molecular mechanisms, a variety of new pharmacologic treatments have recently been developed for patients with age-related macular degeneration (AMD). Efficacy and tolerability have been demonstrated for drugs targeting vascular endothelial growth factor (VEGF), a key player in the pathogenesis of choroidal neovascularization. Both pegaptanib (anti-VEGF aptamer) and ranibizumab (anti-VEGF antibody fragment), applied at 4- to 6-week intervals into the vitreous, modified the natural course of the disease in phase III clinical studies. Corticosteroids with anti-angiogenic properties also represent a treatment option for wet AMD. Both intravitreal triamcinolone and anecortave acetate, administered juxtasclerally, are currently being pursued. The combination of different treatment strategies and potential synergistic effects offers new perspectives. While photodynamic therapy (PDT) combined with intravitreal triamcinolone is already frequently applied, other combinations (e.g. anti-VEGF drugs with PDT or antifibrotic agents) appear to be attractive alternatives. Pigment epithelium-derived factor represents another potential target, as well as inhibitors of matrix-metallo-proteinases. With the advent of gene therapy, the use of small interfering RNA (siRNA) is also on the horizon. Prophylactic measures are still limited. The combination of vitamins C and E, beta-carotene, and zinc as used in the AREDS (Age-Related Eye Disease Study) reduces risk for conversion from early- to late-stage disease in patients with high-risk features, at least to some extent. Lutein and zeaxanthin dietary supplements for improvement of macular pigment density need to be investigated in future longitudinal trials.

Inhibiting matrix metalloproteinases with prinomastat produces abnormalities in fetal growth and development in rats

BACKGROUND

Matrix metalloproteinases (MMPs) play key roles in remodeling of the extracellular matrix during embryogenesis and fetal development. The objective of this study was to determine the effects of prinomastat, a potent selective MMP inhibitor, on fetal growth and development.

METHODS

Prinomastat (25, 100, 250 mg/kg/day, p.o.) was administered to pregnant female Sprague-Dawley rats on gestational days (GD) 6-17. A Cesarian section was carried out on GD 20 and the fetuses were evaluated for viability and skeletal and soft tissue abnormalities.

RESULTS

Prinomastat treatment at the 250 mg/kg/day dose produced a decrease in body weight and food consumption in the dams. A dose-dependent increase in post-implantation loss was observed in the 100 and 250 mg/kg/day-dose groups, resulting in only 22% of the dams having viable litters for evaluation at the 250 mg/kg/day dose. Fetal skeletal tissue variations and malformations were present in all prinomastat treated groups and their frequency increased with dose. Variations and malformation in fetal soft tissue were also increased at the 100 and 250 mg/kg/day doses. Prinomastat also interfered with fetal growth of rat embryo cultures in vitro.

CONCLUSIONS

These data confirm that MMP inhibition has a profound effect on fetal growth and development in vivo and in vitro.

Antiangiogenesis: A Possible Treatment Option for Prostate Cancer?

With a need for effective treatment modalities in prostate cancer, angiogenesis is a likely target for the interference of tumor progression. Angiogenesis promotes the vasculature of a tumor, allowing for tumor progression and for cancer cells to metastasize and spread throughout the circulatory system. To date, there are > 20 antiangiogenic drugs undergoing preclinical and clinical investigation alone and in conjunction with other treatment options to determine the validity of antiangiogenic agents in the treatment of prostate cancer. This article reviews several aspects of antiangiogenesis and its relationship to the treatment of prostate cancer.

The transmembrane domain is essential for the microtubular trafficking of membrane type-1 matrix metalloproteinase (MT1-MMP)

Membrane type-1 matrix metalloproteinase (MT1-MMP) degrades the extracellular matrix, initiates the activation pathway of soluble MMPs and regulates the functionality of cell adhesion signaling receptors, thus playing an important role in many cell functions. Intracellular transport mechanisms, currently incompletely understood, regulate the presentation of MT1-MMP at the cell surface. We have focused our efforts on identifying these mechanisms. To understand the transport of MT1-MMP across the cell, we used substitution and deletion mutants, the trafficking of which was examined using antibody uptake and Chariot delivery experiments. Our experiments have demonstrated that the microtubulin cytoskeleton and the centrosomes (the microtubulin cytoskeleton-organizing centers) are essential for the trafficking and the internalization of MT1-MMP. We determined that after reaching the plasma membrane, MT1-MMP is internalized in the Rab-4-positive recycling endosomes and the Rab-11-positive pericentrosomal recycling endosomes. The microtubular trafficking causes the protease to accumulate in the pericentrosomal region of the cell. We believe that the presence of the transmembrane domain is required for the microtubular vesicular trafficking of MT1-MMP because the soluble mutants are not presented at the cell surface and they are not delivered to the centrosomes. The observed transport mechanisms provide a vehicle for the intracellular targets and, accordingly, for an intracellular cleavage function of MT1-MMP in malignant cells, which routinely overexpress this protease.

Detection of Early Antiangiogenic Effects in Human Colon Adenocarcinoma Xenografts: In vivo Changes of Tumor Blood Volume in Response to Experimental VEGFR Tyrosine Kinase Inhibitor

Antiangiogenesis is emerging as efficient strategy for targeting and potentially eliminating neoplastic tumor vessels. The main goal of this study was to establish whether absolute tumor blood volume (V(b)) change could be used as an early predictor of antiangiogenesis in ectopic and orthotopic colon carcinomas. To assess therapy-induced changes of V(b), we did comparative analysis of signal intensities in tumors and muscle using steady-state magnetic resonance imaging (MRI) assisted with an intravascular paramagnetic contrast agent [gadolinium-labeled protected graft copolymer (PGC-Gd)]. Athymic mice with implanted human MV522 tumors were treated with vascular endothelial growth factor type 2 receptor tyrosine kinase inhibitor (VEGFR2-TKI) that has been shown to inhibit VEGFR2 phosphorylation and tumor growth in vivo. Animals were imaged either after a single day or after a 1-week course of treatments. The measured V(b) in ectopic tumors was 2.5 +/- 1.5% of total tissue volume 1 week after the implantation (n = 8). Two doses of VEGFR2-TKI (25 mg/kg, p.o., b.i.d.) resulted in a decrease of V(b) to 1.3 +/- 0.3%. In orthotopic tumors, the measured V(b) was initially higher (11.9 +/- 2.0%); however, VEGFR2-TKI treatment also resulted in a statistically significant decrease of V(b). The absolute V(b) was not affected in the muscle as a result of treatments. MRI measurements were corroborated by using isotope and correlative histology experiments. Our results show that steady-state MRI is highly sensitive to early antiangiogenic effects caused by small molecule drugs.

Angiogenesis in gliomas: imaging and experimental therapeutics

Much of the interest in angiogenesis and hypoxia has led to investigating diagnostic imaging methodologies and developing efficacious agents against angiogenesis in gliomas. In many ways, because of the cytostatic effects of these agents on tumor growth and tumor-associated endothelial cells, the effects of therapy are not immediately evident. Hence finding clinically applicable imaging tools and pathologic surrogate markers is an important step in translating glioma biology to therapeutics. There are a variety of strategies in the approach to experimental therapeutics that target the hypoxia-inducible factor pathway, the endogenous antiangiogenic and proangiogenic factors and their receptors, adhesion molecules, matrix proteases and cytokines, and the existing vasculature. We discuss the rationale for antiangiogenesis as a treatment strategy, the preclinical and clinical assessment of antiangiogenic interventions and finally focus on the various treatment strategies, including combining antiangiogenic drugs with radiation and chemotherapy.

Molecular optical imaging: applications leading to the development of present day therapeutics

A number of advances in the molecular imaging field have led to the sensing of specific molecular targets and pathways in living animals. In the optical imaging field, these include the designing of biocompatible near-infrared fluorochromes, development of targeted and activatable "smart" imaging probes, and engineering of activatable fluorescent and bioluminescent proteins. The current advances in molecular optical imaging will help in early disease diagnoses, functioning of a number of pathways and finally help speed drug discovery. In this review, we will describe the near infrared fluorescent and bioluminescence imaging modalities and how these techniques have been employed in current research. Furthermore, we will also shed some light on the use of these imaging modalities in neurotherapeutics, for example imaging different parameters of vector-mediated gene expression in glioma tumors and stem cell tracking in vivo.

Molecular optical imaging: applications leading to the development of present day therapeutics

A number of advances in the molecular imaging field have led to the sensing of specific molecular targets and pathways in living animals. In the optical imaging field, these include the designing of biocompatible near-infrared fluorochromes, development of targeted and activatable "smart" imaging probes, and engineering of activatable fluorescent and bioluminescent proteins. The current advances in molecular optical imaging will help in early disease diagnoses, functioning of a number of pathways and finally help speed drug discovery. In this review, we will describe the near infrared fluorescent and bioluminescence imaging modalities and how these techniques have been employed in current research. Furthermore, we will also shed some light on the use of these imaging modalities in neurotherapeutics, for example imaging different parameters of vector-mediated gene expression in glioma tumors and stem cell tracking in vivo.

Alteration of the Pharmacokinetics of COL-3, a Matrix Metalloproteinase Inhibitor, Due to Acute Gastrointestinal Toxicity of Doxorubicin

PURPOSE

Combination of COL-3, a matrix metalloproteinase inhibitor, and doxorubicin (DOX) might be a promising anticancer regimen. The present study was to examine the potential pharmacokinetic interactions and toxicity profile following their coadministration in rats.

METHODS

Normal rats were treated with single agent or different combinations with oral or intravenous COL-3 and DOX, and the bile-duct cannulated (BDC) rats received oral COL-3 plus DOX. In a separate disposition study, the effects of DOX on the biliary, urinary, and fecal excretion of COL-3 were examined. In addition, the effects of DOX on in vitro protein binding, metabolism, and transport of COL-3 across Caco-2 monolayers were investigated.

RESULTS

COL-3 did not affect the pharmacokinetics of DOX in rats. However, treatment with DOX significantly decreased the oral absorption, and prolonged the elimination, of COL-3 in the normal rats, but not in the BDC rats. DOX did not alter the biliary and urinary excretion of COL-3, but significantly decreased the fecal excretion of COL-3. DOX significantly enhanced the basolateral to apical flux of COL-3 across Caco-2 monolayers, but had no apparent effects on the protein binding and metabolism of COL-3. The combination of DOX with oral COL-3 did not significantly (p > 0.05) increase the acute diarrhea score and intestinal damage compared to rats receiving DOX alone.

CONCLUSIONS

These results indicated that DOX altered the oral absorption and elimination of COL-3, largely resulting from gastrointestinal toxicity caused by biliary excretion of DOX. Further studies are required to explore the efficacy and optimized dosage regimen of this promising combination.

Metalloproteinases and their inhibitors in tumor angiogenesis

Angiogenesis is the process by which new blood vessels are formed from preexisting vasculature. It is an essential feature of the female reproductive cycle, embryonic development and wound repair. Angiogenesis has also been identified as a causal or contributing factor in several pathologies, including cancer, where it is a rate-limiting step during tumor progression. Matrix metalloproteinases (MMPs) are a family of soluble and membrane-anchored proteolytic enzymes that can degrade components of the extracellular matrix (ECM) as well as a growing number of modulators of cell function. Several of the MMPs, in particular the gelatinases and membrane-type 1 MMP (MT1-MMP), have been linked to angiogenesis. Potential roles for these proteases during the angiogenic process include degradation of the basement membrane and perivascular ECM components, unmasking of cryptic biologically relevant sites in ECM components, modulation of angiogenic factors and production of endogenous angiogenic inhibitors. This review brings together what is currently known about the functions of the MMPs and the closely related ADAM (a disintegrin and metalloproteinase domain) and ADAMTS (a disintegrin and metalloproteinase with thrombospondin motifs) families in angiogenesis and considers how this information might be useful in manipulation of the angiogenic process, with a view to constraining tumor progression.

Cyclic mechanical strain-induced proliferation and migration of human airway smooth muscle cells: role of EMMPRIN and MMPs

Airway smooth muscle (ASM) proliferation and migration are major components of airway remodeling in asthma. Asthmatic airways are exposed to mechanical strain, which contributes to their remodeling. Matrix metalloproteinase (MMP) plays an important role in remodeling. In the present study, we examined if the mechanical strain of human ASM (HASM) cells contributes to their proliferation and migration and the role of MMPs in this process. HASM were exposed to mechanical strain using the FlexCell system. HASM cell proliferation, migration and MMP release, activation, and expression were assessed. Our results show that cyclic strain increased the proliferation and migration of HASM; cyclic strain increased release and activation of MMP-1, -2, and -3 and membrane type 1-MMP; MMP release was preceded by an increase in extracellular MMP inducer; Prinomastat [a MMP inhibitor (MMPI)] significantly decreased cyclic strain-induced proliferation and migration of HASM; and the strain-induced increase in the release of MMPs was accompanied by an increase in tenascin-C release. In conclusion, cyclic mechanical strain plays an important role in HASM cell proliferation and migration. This increase in proliferation and migration is through an increase in MMP release and activation. Pharmacological MMPIs should be considered in the pursuit of therapeutic options for airway remodeling in asthma.

Tumour angiogenesis: a novel therapeutic target in patients with malignant disease

Angiogenesis refers to the formation of new blood vessels from an existing vasculature and is recognised as a necessary requirement for most tumours to grow beyond 1-2 mm in diameter. Factors established as playing a role in angiogenesis may be divided into two principal groups: (a) those that stimulate endothelial cell proliferation and/or elongation, migration and vascular morphogenesis including vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), platelet derived endothelial cell growth factor (PD-ECGF) and the tie and tek receptors, and (b) proteases and their receptors involved in the breakdown of basement membranes and the extracellular matrix (ECM) including the matrix metalloproteinases (MMPs), cathepsins and those involved in the plasmin cascade. Angiogenesis has been identified as a potential target for development of anticancer agents. The discovery of a range of naturally-occurring factors which negatively regulate angiogenesis, including the thrombospondins, angiostatin and endostatin, and the tissue inhibitors of MMPs (TIMPs), has given added impetus to this approach. Synthetic anti-angiogenic compounds have been developed, including TNP-470, carboxyamidotriazole, VEGF-tyrosine kinase inhibitors and MMP inhibitors (MMPI) which, like the naturally-occurring anti-angiogenic factors, inhibit angiogenesis in vitro and in vivo, and tumour development, growth and metastasis in vivo. Anti-angiogenic agents also enhance the antitumour activity of many conventional cytotoxic chemotherapeutic agents. Such combinations may have a particular role as adjuvant therapies following surgical resection of primary tumours. Unlike tumour cells, tumour associated endothelial cells do not develop resistance to anti-angiogenic agents. Furthermore, anti-angiogenic agents are generally cytostatic rather than cytotoxic. As such, these agents are, in general, likely to be administered over long periods of time. Therefore, as well as having proven antitumour efficacy, an anti-angiogenic compound will need to be well-tolerated if it is to become established in the clinical management of patients with malignant disease.

Inhibition of Membrane Type-1 Matrix Metalloproteinase by Cancer Drugs Interferes with the Homing of Diabetogenic T Cells into the Pancreas

We have discovered that clinically tested inhibitors of matrix metalloproteinases can control the functional activity of T cell membrane type-1 matrix metalloproteinase (MT1-MMP) and the onset of disease in a rodent model of type 1 diabetes in non-obese diabetic mice. We determined that MT1-MMP proteolysis of the T cell surface CD44 adhesion receptor affects the homing of T cells into the pancreas. We also determined that both the induction of the intrinsic T cell MT1-MMP activity and the shedding of cellular CD44 follow the adhesion of insulin-specific, CD8-positive, Kd-restricted T cells to the matrix. Conversely, inhibition of these events by AG3340 (a potent hydroxamate inhibitor that was widely used in clinical trials in cancer patents) impedes the transmigration of diabetogenic T cells into the pancreas and protects non-obese diabetic mice from diabetes onset. Overall, our studies have divulged a previously unknown function of MT1-MMP and identified a promising novel drug target in type I diabetes.

Antimetastatic activity of a novel mechanism-based gelatinase inhibitor

Matrix metalloproteinases (MMPs), and in particular gelatinases (MMP-2 and MMP-9), play a key role in cancer progression. However, clinical trials in which MMP inhibitors were tested in cancer patients have been disappointing. Whereas many reasons have been postulated to explain the failure of the clinical trials, lack of inhibitor selectivity was a major limitation. Thus, despite the consensus opinion that MMP-mediated proteolysis is essential for cancer progression and that certain MMPs represent important targets for intervention, effective and selective inhibition of those MMPs remains a major challenge in drug development. We previously reported the first mechanism-based MMP inhibitor, designated SB-3CT, which is a selective gelatinase inhibitor. Here we report that SB-3CT (5-50 mg/kg/d) is a potent inhibitor of liver metastasis and increases survival in an aggressive mouse model of T-cell lymphoma. This study shows that mechanism-based inhibition of gelatinases represents a novel approach to inhibitor design that promises to be a successful anticancer therapy.

Cerebral Ischemic Events in Patients with Advanced Lung or Prostate Cancer

Conventional stroke risks are thought responsible for most cerebral ischemic events (CIE) in adult cancer patients. Also suspected as a risk is cisplatin chemotherapy, alone or in combination with tumor angiogenesis inhibitor. We investigated whether treatment or tumor characteristics, independently of conventional stroke risks, are associated with CIE in a retrospective cohort study of 1,559 patients with advanced non-small cell lung cancer or hormone-refractory prostate cancer followed during 3 clinical trials of matrix metalloprotease inhibitor (prinomastat) versus placebo, with chemotherapy (gemcitabine/cisplatin, paclitaxel/carboplatin or mitoxantrone/prednisone). During 11,907 patient-months, 28 CIE (17 cerebral infarction, 11 transient ischemic attack) were diagnosed in 24 patients, all but 1 over 55 years. Neither prinomastat, platinum-based chemotherapy nor their combination was associated with CIE after age 55. However, such events were predicted by the presence of distant metastases in the liver or lungs and not in distant lymph nodes (hazard estimate 4.6, 95% CI 2.0-10.5, adjusted for conventional stroke risks). Further studies are needed to verify this preliminary finding and determine its generalizability to advanced tumors other than lung or prostate cancer.

Gelatinase-mediated migration and invasion of cancer cells

The matrix metalloproteinases(MMP)-2 and -9, also known as the gelatinases have been long recognized as major contributors to the proteolytic degradation of extracellular matrix during tumor invasion. In the recent years, a plethora of non-matrix proteins have also been identified as gelatinase substrates thus significantly broadening our understanding of these enzymes as proteolytic executors and regulators in various physiological and pathological states including embryonic growth and development, angiogenesis and tumor progression, inflammation, infective diseases, degenerative diseases of the brain and vascular diseases. Although the effect of broad-spectrum inhibitors of MMPs in the treatment of cancer has been disappointing in clinical trials, novel mechanisms of gelatinase inhibition have been now identified. Inhibition of the association of the gelatinases with cell-surface integrins appears to offer highly specific means to target these enzymes without inhibiting their catalytic activity in multiple cell types including endothelial cells, tumor cells and leukocytes. Here, we review the multiple functions of the gelatinases in cancer, and especially their role in the tumor cell migration and invasion.

Phase III study of matrix metalloproteinase inhibitor prinomastat in non-small-cell lung cancer

PURPOSE

Matrix metalloproteinases (MMPs) degrade extracellular proteins and facilitate tumor growth, invasion, metastasis, and angiogenesis. This trial was undertaken to determine the effect of prinomastat, an inhibitor of selected MMPs, on the survival of patients with advanced non-small-cell lung cancer (NSCLC), when given in combination with gemcitabine-cisplatin chemotherapy.

PATIENTS AND METHODS

Chemotherapy-naive patients were randomly assigned to receive prinomastat 15 mg or placebo twice daily orally continuously, in combination with gemcitabine 1,250 mg/m2 days 1 and 8 plus cisplatin 75 mg/m2 day 1, every 21 days for up to six cycles. The planned sample size was 420 patients.

RESULTS

Study results at an interim analysis and lack of efficacy in another phase III trial prompted early closure of this study. There were 362 patients randomized (181 on prinomastat and 181 on placebo). One hundred thirty-four patients had stage IIIB disease with T4 primary tumor, 193 had stage IV disease, and 34 had recurrent disease (one enrolled patient was ineligible with stage IIIA disease). Overall response rates for the two treatment arms were similar (27% for prinomastat v 26% for placebo; P = .81). There was no difference in overall survival or time to progression; for prinomastat versus placebo patients, the median overall survival times were 11.5 versus 10.8 months (P = .82), 1-year survival rates were 43% v 38% (P = .45), and progression-free survival times were 6.1 v 5.5 months (P = .11), respectively. The toxicities of prinomastat were arthralgia, stiffness, and joint swelling. Treatment interruption was required in 38% of prinomastat patients and 12% of placebo patients.

CONCLUSION

Prinomastat does not improve the outcome of chemotherapy in advanced NSCLC.

Future directions of liposome- and immunoliposome-based cancer therapeutics

Nanoscale drug delivery systems including liposomes, polymers, and other nanoparticles provide potential solutions for improved cancer therapeutics. Of these drug delivery systems, liposome-based agents, particularly liposomal anthracyclines, have had the greatest impact in oncology to date. Current liposomal drugs evolved from a number of design strategies for improved biodistribution over free drugs. Reticuloendothelial system-targeted formulations significantly reduce systemic exposure to high peak levels of free drug, but do not facilitate targeting to tumors. Passive or physiologic targeting of drugs to tumors is achievable using long-circulating liposomes, including pure lipid systems as well as surface-modified formulations designed to resist recognition and uptake by reticuloendothelial system cells. The latter, represented by pegylated or STEALTH liposomes, circulate for days as stable constructs and slowly extravasate in neoangiogenic vessels in tumors, providing a degree of passive targeting to tumor tissue. Future liposome therapeutics are building on these validated designs as well as on pharmacologic insights into their mechanisms of delivery. For example, camptothecin analogues, anti-angiogenesis agents, and antisense oligonucleotides each represent rational candidates for delivery in highly stabilized and long-circulating liposomes. For such agents, pegylated liposome delivery offers improved chemical stability of encapsulated drug, enhanced accumulation in tumors, and prolonged drug exposure. True molecular targeting can be achieved using liposomes linked to ligands such as monoclonal antibody fragments directed against cancer-associated antigens. Immunoliposomes combine antibody-mediated tumor recognition with liposomal delivery and, when designed for target cell internalization, provide intracellular drug release. Recent advances in immunoliposome design include rapid selection of phage antibody-derived scFv for targeting, and methods for conjugation of ligands to existing US Food and Drug Administration-approved liposomal drugs such as pegylated liposomal doxorubicin (Doxil/Caelxy [PLD]). An immunoliposome consisting of novel anti-HER2 scFv F5 conjugated to PLD, currently in development, selectively binds to and internalizes in HER2-overexpressing tumor cells. The modular organization of immunoliposome technology enables a combinatorial approach in which a repertoire of monoclonal antibody fragments can be used in conjunction with a series of liposomal drugs to yield a new generation of molecularly targeted agents.

Preventive versus treatment effect of AG3340, a potent matrix metalloproteinase inhibitor in a rat model of choroidal neovascularization

PURPOSE

AG3340 (prinomastat) is a nonpeptidic, small-molecular-weight, synthetic matrix metalloproteinase inhibitor (MMPI) with selective inhibitory action of MMP-2, MMP-9, MMP-3, and MT-MMP1. We evaluated AG3340 injected intravitreally to treat choroidal neovascularization in a laser induced rat CNV model.

METHODS

In the pretreatment group, the drug was injected the same day after induction of choroidal neovascularization by diode laser. In the treatment group, the drug was injected 2 weeks after induction of choroidal neovascularization (CNV). Fluorescein and indocyanine green angiography were performed to evaluate CNV. ERG recordings and histology were performed to assess toxicity and the CNV lesions.

RESULTS

When used at the time of CNV induction, 62.8% of lesions in control versus 22.8% of the laser lesions in treated eyes developed CNV (p < 0.0001). The invading fibrovascular complex was thicker in the control eyes than that in the treated eyes. No signs of toxicity were detected. When used to treat established CNV, the percentage of leakage in treated and control eyes were 54.1% and 58.9% respectively (p > 0.05). Prinomastat was effective when given at the time of induction of CNV in the rat model. Administration of prinomastat 2 weeks after laser induction did not show efficacy.

CONCLUSION

Prinomastat was active in the earliest stages of experimental CNV. It might be best used in combination with photodynamic therapy to inhibit recurrence of CNV from temporarily closed new vessels.

The effect of prinomastat (AG3340), a potent inhibitor of matrix metalloproteinase, on a new animal model of epiretinal membrane

PURPOSE

To develop a simple epiretinal membrane (ERM) animal model and evaluate the efficacy of prinomastat (AG3340), a synthetic inhibitor of matrix metalloproteinase.

METHODS

This experiment was carried out on 18 eyes of nine Brown Norway rats. Preretinal hemorrhage was induced bilaterally using diode laser focused deeply on choroidal blood vessels. One day later, AG3340 was injected intravitreally in the right eyes while the left eyes received equal amounts of vehicle. The developed epiretinal membrane was measured in disk areas and compared between groups.

RESULTS

Clinically, preretinal hemorrhage showed a slow clearance persisting for 8 to 10 weeks. ERM was well established around 12 weeks. Histologically, ERMs consist of fibroblast and glial cells embedded in collagen-rich extracellular matrix infiltrated by macrophages. Seventy-five percent of the hemorrhagic laser burns in the control group developed ERM, whereas only 25% of the hemorrhagic laser burns in treated group developed ERM (P = 0.01). The total surface area of developed ERM was 3.66 DD in treated eyes versus 25.45 DD in control eyes (P = 0.049). The mean surface area of ERM per eye was 0.52 disk areas +/- 1.05 in treated eyes versus 3.18 +/- 3.07 in control eyes.

CONCLUSION

We demonstrated that ERM can be induced on rat retina by simple hemorrhagic retinal laser coagulation. This new animal model could be used for future evaluation of different medical treatment modalities for proliferating ERM. Furthermore, AG3340 demonstrated an inhibitory effect on ERM formation in this new rat model.

Cartilage degradation independent of MMP/aggrecanases

OBJECTIVE

To identify and characterize a cartilage degradation mechanism that is independent of the proteolytic cleavages by matrix metalloproteinases (MMPs) and aggrecanases.

METHODS

The sensitivity of glycosaminoglycan (GAG) release and collagen release to an MMP/aggrecanase inhibitor, AG3340, was compared using a bovine nasal cartilage explant culture. The release of matrix proteins and hyaluronan (HA) from the culture was analyzed by immunoblotting and radioimmunoassay, respectively. Induction of HA-degrading activity by retinoic acid was examined using the cartilage explant culture and a primary culture of chondrocytes. Degradation of the matrix components of cartilage was also characterized in vivo using an acute arthritis model induced by an intra-articular injection of interleukin 1alpha (IL-1alpha).

RESULTS

AG3340 did not effectively inhibit GAG release at a concentration of more than 10muM, while 10nM of the inhibitor completely suppressed collagen degradation. Retinoic acid induced the release of the aggrecan G1 domain, link protein and HA into the culture medium, and the release of these molecules was not completely inhibited by 10muM of AG3340. The molecules were released as ternary complexes. Retinoic acid induced HA degradation in the explant culture and hyaluronidase activity in the primary culture of chondrocytes. The release of the G1 domain of aggrecan and link protein into the synovial fluid was also observed in the IL-1alpha-induced acute arthritis model.

CONCLUSION

A novel mechanism by chondrocyte-derived hyaluronidase(s) is involved in the release of the matrix components from cartilage, and the hyaluronidase(s) and MMPs/aggrecanases act in a coordinated manner in cartilage degradation.

Magnetic resonance imaging detects early changes in microvascular permeability in xenograft tumors after treatment with the matrix metalloprotease inhibitor Prinomastat

Macromolecular contrast medium-enhanced magnetic resonance imaging was applied to monitor the effect of matrix metalloprotease (MMP) inhibition on microvascular characteristics of human breast cancers implanted in athymic rats. Twice-daily intraperitoneal administration of Prinomastat over 1.5 days induced significant declines in MRI-assayed microvascular permeabilities (p<0.05); but this leak suppression effect had extinguished by the 10(th) day of MMP treatment using the same dose and time schedule. Results demonstrate that Prinomastat produces a rapid but transient decrease in tumor vascular permeability. Contrast-enhanced MRI using macromolecular contrast medium may prove useful as a biomarker for the dynamic MMP biological effect in cancers.

Different pattern of matrix metalloproteinases expression in alveolar versus embryonal rhabdomyosarcoma

BACKGROUND/PURPOSE

The matrix metalloproteinases (MMPs), a family of enzymes that degrade the extracellular matrix (ECM), are important in neoplastic cell invasion and metastasis. Data for rhabdomyosarcoma (RMS), the most frequent soft tissue sarcoma of childhood, are lacking. The aim of this study was to assess their expression in this tumor and to evaluate the correlation with clinicopathologic parameters.

METHODS

Immunohistochemical expression of MMP-1, MMP-2, MMP-3, MMP-7, MMP-9, TIMP-1, and TIMP-2 was investigated in 33 human RMSs, 12 alveolar, and 21 embryonal histologic subtypes (12 high risk and 9 low/standard risk). Evaluation of the results was based on the percent of positive neoplastic cells and on staining intensity (negative, moderate, and strong). In situ zymography was carried out on 4 frozen RMS samples (2 alveolar and 2 high-risk embryonal).

RESULTS

Alveolar type showed a stronger MMP-1, -2 and -9 expression in comparison with embryonal (P = .006, P <.001, and P <.001, respectively). Intratumoral vessels and perivascular ECM were positive for MMP-9 in the majority of RMSs. Both TIMPs had negative results.

CONCLUSIONS

Gelatinases MMP-2 and MMP-9 and collagenase MMP-1 overexpression seem to contribute to the more aggressive phenotype of alveolar rhabdomyoblastic cells. Further characterization of the expression of MMPs and consequent utilization of their inhibitors in aggressive alveolar RMSs might lead to the development of novel anticancer therapies.

Phase I and pharmacokinetic study of prinomastat, a matrix metalloprotease inhibitor

PURPOSE

Prinomastat is a matrix metalloprotease (MMP) inhibitor with selectivity for MMPs 2, 3, 9, 13, and 14. Inhibition of these MMPs has been postulated to block tumor invasion and metastasis. This Phase I, dose-escalation study was designed to evaluate the acute and chronic toxicities of various doses of prinomastat and to determine prinomastat pharmacokinetics.

EXPERIMENTAL DESIGN

Seventy-five patients with advanced cancer were given 1, 2, 5, 10, 25, 50, or 100 mg prinomastat orally twice daily until tumor progression or development of significant toxicities. Prinomastat pharmacokinetics were measured on day 29 of therapy.

RESULTS

The primary toxicities identified were joint and muscle-related pain, which were generally reversible with treatment rest and/or dose reduction. No dose-limiting toxicities were noted within the first 4 weeks of treatment, but grade 2-3 arthralgias and myalgias were noted 2-3 months after initiation of therapy in >25% of patients at doses >25 mg twice a day. The frequency and severity of symptoms were dose related. Plasma prinomastat concentrations greater than the K(i) for MMPs 2 and 9 were achieved at all of the dose levels.

CONCLUSIONS

Doses of 5-10 mg bid were recommended for additional trials, because this dose range was well tolerated for a treatment duration of at least 3 months and achieves trough plasma concentrations 10-100-fold greater than the K(i) (in vitro inhibition constant) for the targeted MMPs (2 and 9).

Patterns of protease production during prostate cancer progression: proteomic evidence for cascades in a transgenic model

Extracellular proteases are recognized as critical factors in the progression of a number of carcinomas, including prostate cancer. Matrix metalloproteases (MMP) are important in processes of tumor growth, invasion and dissemination, but other classes of proteases, such as serine and cysteine proteases, also contribute. We utilized the TRAMP model for prostate cancer to elucidate proteases involved in prostate cancer progression. General proteomic analysis was performed on normal murine prostate, early TRAMP tumors and advanced TRAMP tumors, as well as normal and involved lymph nodes. Zymography and antigenic analyses revealed increased expression of mainly pro-MMP in early TRAMP tumors but substantial elaboration of activated MMP only in late TRAMP tumors. Progressive increase in cysteine, serine and certain membrane-bound proteases from normal to early to advanced prostate tumors, was also seen. Our results implicate pericellular proteases as initiators of major proteolytic cascades during tumor progression and suggest targets for maximal therapeutic effect.

Inhibition of glioma angiogenesis and invasion by SI-27, an anti-matrix metalloproteinase agent in a rat brain tumor model

OBJECTIVE

The matrix metalloproteinase (MMP) inhibitor SI-27 has undergone extensive development because of its effectiveness against glioma invasion and angiogenesis. However, previous studies have been performed in vitro. The present work investigates the potential of SI-27 to inhibit tumor invasion, slow angiogenesis, and prolong survival in rodent brain tumor models.

METHODS

Stable enhanced green fluorescent protein-expressing clones of a human malignant glioma cell line, U251MG, were stereotactically xenografted into the periphery of the anterior striatum and corpus callosum of Fischer 944 rats after immunosuppression with cyclosporin A. SI-27 (1 or 10 mg/kg) or carrier solution was administered on three successive days by intraperitoneal injection, and tumor invasion and angiogenesis were assessed 3 weeks later by quantitative image analysis. This was performed on whole brain sections analyzed either by direct observation of enhanced green fluorescent protein-expressing glioma cells or by additional immunohistochemistry to detect the endothelial cells with anti-factor VIII monoclonal antibody. In situ zymography on frozen sections was used to detect MMP activity.

RESULTS

The group receiving a total of 30 mg/kg showed a statistically significant (P < 0.001) increase in survival time compared with the controls receiving carrier (median survival, 47.3 versus 32.6 d). There was also a decrease in MMP activity, tumor cell invasion, and neovascularization. In contrast, animals given 3 mg/kg did not show these differences.

CONCLUSION

Systemic administration of the anti-MMP agent SI-27 is effective in the treatment of glioma in an animal model.

Matrix metalloproteinase-2 and -9 expression increases in Mycoplasma-infected airways but is not required for microvascular remodeling

Murine Mycoplasma pulmonis infection induces chronic lung and airway inflammation accompanied by profound and persistent microvascular remodeling in tracheobronchial mucosa. Because matrix metalloproteinase (MMP)-2 and -9 are important for angiogenesis associated with placental and long bone development and skin cancer, we hypothesized that they contribute to microvascular remodeling in airways infected with M. pulmonis. To test this hypothesis, we compared microvascular changes in airways after M. pulmonis infection of wild-type FVB/N mice with those of MMP-9−/− and MMP-2−/−/MMP-9−/− double-null mice and mice treated with the broad-spectrum MMP inhibitor AG3340 (Prinomastat). Using zymography and immunohistochemistry, we find that MMP-2 and MMP-9 rise strikingly in lungs and airways of infected wild-type FVB/N and C57BL/6 mice, with no zymographic activity or immunoreactivity in MMP-2−/−/MMP-9−/− animals. However, microvascular remodeling as assessed by Lycopersicon esculentum lectin staining of whole-mounted tracheae is as severe in infected MMP-9−/−, MMP-2−/−/MMP-9−/− and AG3340-treated mice as in wild-type mice. Furthermore, all groups of infected mice develop similar inflammatory infiltrates and exhibit similar overall disease severity as indicated by decrease in body weight and increase in lung weight. Uninfected wild-type tracheae show negligible MMP-2 immunoreactivity, with scant MMP-9 immunoreactivity in and around growing cartilage. By contrast, MMP-2 appears in epithelial cells of infected, wild-type tracheae, and MMP-9 localizes to a large population of infiltrating leukocytes. We conclude that despite major increases in expression, MMP-2 and MMP-9 are not essential for microvascular remodeling in M. pulmonis-induced chronic airway inflammation.

Effect of deoxyribozymes targeting c-Jun on solid tumor growth and angiogenesis in rodents

BACKGROUND

The basic region-leucine zipper protein c-Jun has been linked to cell proliferation, transformation, and apoptosis. However, a direct role for c-Jun in angiogenesis has not been shown.

METHODS

We used human microvascular endothelial cells (HMEC-1) transfected with a DNAzyme targeting the c-Jun mRNA (Dz13), related oligonucleotides, or vehicle in in vitro models of microvascular endothelial cell proliferation, migration, chemoinvasion, and tubule formation, a rat model of corneal neovascularization, and a mouse model of solid tumor growth and vascular endothelial growth factor (VEGF)-induced angiogenesis. All statistical tests were two-sided.

RESULTS

Compared with mock-transfected cells, HMEC-1 cells transfected with Dz13 expressed less c-Jun protein and possessed lower DNA-binding activity. Dz13 blocked endothelial cell proliferation, migration, chemoinvasion, and tubule formation. Dz13 inhibited the endothelial cell expression and proteolytic activity of MMP-2, a c-Jun-dependent gene. Dz13 inhibited VEGF-induced neovascularization in the rat cornea compared with vehicle control (Dz13 versus vehicle: 4.0 neovessels versus 30.7 neovessels, difference = 26.7 neovessels; P =.004; area occupied by new blood vessels for Dz13 versus vehicle: 0.35 mm2 versus 1.52 mm2, difference = 1.17 mm2; P =.005) as well as solid melanoma growth in mice (Dz13 versus vehicle at 14 days: 108 mm3 versus 283 mm3, difference = 175 mm3; P =.006) with greatly reduced vascular density (Dz13 versus vehicle: 30% versus 100%, difference = 70%; P<.001).

CONCLUSION

DNAzymes targeting c-Jun may have therapeutic potential as inhibitors of tumor angiogenesis and growth.

The matrix metalloproteinase inhibitor prinomastat enhances photodynamic therapy responsiveness in a mouse tumor model

Photodynamic therapy (PDT) clinical results are promising; however, tumor recurrences can occur and, therefore, methods for improving treatment efficacy are needed. PDT elicits direct tumor cell death and microvascular injury as well as expression of angiogenic, inflammatory, and prosurvival molecules. Preclinical studies combining antiangiogenic drugs or cyclooxygenase-2 inhibitors with PDT show improved treatment responsiveness (A. Ferrario et al., Cancer Res 2000;60:4066-9; A. Ferrario et al., Cancer Res 2002;62:3956-61). In the present study, we evaluated the role of Photofrin-mediated PDT in eliciting expression of matrix metalloproteinases (MMPs) and modulators of MMP activity. We also examined the efficacy of a synthetic MMP inhibitor, Prinomastat, to enhance tumoricidal activity after PDT, using a mouse mammary tumor model. Immunoblot analysis of extracts from PDT-treated tumors demonstrated strong expression of MMPs and extracellular MMP inducer along with a concomitant decrease in expression of tissue inhibitor of metalloproteinase-1. Gelatin zymography and enzyme activity assays performed on protein extracts from treated tumors confirmed the induction of both latent and enzymatically active forms of MMP-9. Immunohistochemical analysis indicated that infiltrating inflammatory cells and endothelial cells were primary sources of MMP-9 expression after PDT, whereas negligible expression was observed in tumor cells. Administration of Prinomastat significantly improved PDT-mediated tumor response (P = 0.02) without affecting normal skin photosensitization. Our results indicate that PDT induces MMPs and that the adjunctive use of an MMP inhibitor can improve PDT tumor responsiveness.

Pro-matrix metalloproteinase-2 transfection increases orthotopic primary growth and experimental metastasis of MDA-MB-231 human breast cancer cells in nude mice

The ability to activate pro-matrix metalloproteinase (pro-MMP)-2 via membrane type-MMP is a hallmark of human breast cancer cell lines that show increased invasiveness, suggesting that MMP-2 contributes to human breast cancer progression. To investigate this, we have stably transfected pro-MMP-2 into the human breast cancer cell line MDA-MB-231, which lacks MMP-2 expression but does express its cell surface activator, membrane type 1-MMP. Multiple clones were derived and shown to produce pro-MMP-2 and to activate it in response to concanavalin A. In vitro analysis showed that the pro-MMP-2-transfected clones exhibited an increased invasive potential in Boyden chamber and Matrigel outgrowth assays, compared with the parental cells or those transfected with vector only. When inoculated into the mammary fat pad of nude mice, each of the MMP-2-tranfected clones grew faster than each of the vector controls tested. After intracardiac inoculation into nude mice, pro-MMP-2-transfected clones showed a significant increase in the incidence of metastasis to brain, liver, bone, and kidney compared with the vector control clones but not lung. Increased tumor burden was seen in the primary site and in lung metastases, and a trend toward increased burden was seen in bone, however, no change was seen in brain, liver, or kidney. This data supports a role for MMP-2 in breast cancer progression, both in the growth of primary tumors and in their spread to distant organs. MMP-2 may be a useful target for breast cancer therapy when refinement of MMP inhibitors provides for MMP-specific agents.

Drug-induced apoptosis by a matrix metalloproteinase inhibitor, SI-27 on human malignant glioma cell lines; in vitro study

Matrix metalloproteinase (MMP) plays important roles in cell invasion and tumor angiogenesis. SI-27, an anti-MMP agent, has already been shown to possess both in vitro anti-invasive and anti-angiogenic properties against malignant gliomas in non-cytotoxic dose concentrations. However, to the best of our knowledge, the molecular mechanism mediating the cytotoxic action by this agent and the molecular mechanism in the cytotoxic action against malignant glioma cell have not yet been clarified. Therefore, we assessed the effect in the cytotoxic dose concentrations to investigate whether this cytotoxic action is related to apoptosis in this study. The effect on human glioma cell lines (U87MG, U251MG, and U373MG) was examined by transmission electron microscope, agarose gel electrophoresis with the DNA fragmentation, flow cytometry with FITC-conjugated Annexin V, and detection of caspase activity. Drug-induced apoptosis was observed in the cytotoxic dose. The result indicated that the cytotoxity of SI-27 might be related to the drug-induced apoptosis mediated by caspase.

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

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

Apoptotic induction by BE16627B on human malignant glioma cell lines by an anti-matrix metalloproteinase agent

We have elucidated the pharmacological action of the anti-matrix metalloproteinase inhibitor BE16627B on glioma cells. The study was limited to the noncytotoxic dose range. The aim of the study was to investigate whether the cytotoxicity of BE16627B, an anti-MMP agent, is related to apoptosis in the human malignant glioma cell lines U87MG, U251MG, and U373MG. MTT assay was performed to detect the cytotoxic dose range. Agarose gel electrophoresis was performed with purified genomic DNA following exposure to 20 to 500 microM BE16627B for 24 h, compared with 0 microM for the control group. Transmission electron microscopy (TEM) was employed to study nuclear fragmentation following exposure to 0, 20, and 500 microM of the agent for 24 h. An in situ endolabeling assay was performed to determine the index of apoptotic induction. MTT assay revealed that concentrations of 100 microM and above were cytotoxic. DNA laddering was demonstrated in agarose gel electrophoresis. TEM disclosed condensing and fragmentation of the chromatin. None of these changes were observed in the control group and the noncytotoxic dose group. The in situ endolabeling study disclosed that the apoptotic index was significantly elevated by cytotoxic doses of this agent (U373MG; control, 4.0%; 500 microM, 68.5%). These results indicated that cytotoxic concentrations of BE16627B induced apoptosis in human malignant glioma cell lines. In our previous report, this agent inhibited activity of MMP in noncytotoxic concentrations. Further study should be done to determine the pharmacological action of toxic BE16627B.

Promising developments in targeted therapies for non-small-cell lung cancer

Despite advances in chemotherapy, radiation therapy, and surgery, the overall survival for patients with lung cancer remains poor. Thus, novel therapeutic approaches are warranted. As knowledge of the molecular abnormalities and dysregulated cellular processes contributing to the pathogenesis and progression of lung cancer has been acquired, intense interest has been directed at developing agents that target these abnormalities. New agents targeting aberrant receptor tyrosine kinases, the Ras oncoprotein, mediators of metastases and angiogenesis, and the tumor suppressor gene p53 have, among other agents, shown promise in preclinical studies. Early clinical trials with these agents in patients with advanced malignancies suggest preliminary evidence of clinical activity and possible applications in non-small-cell lung cancer (NSCLC). Ongoing clinical trials will help clarify the settings in which these agents are of greatest therapeutic value, the optimal schedule of administration, toxicities associated with chronic administration, and hopefully, provide additional insight into the biology of lung cancer. Selected clinical trials will be presented to highlight the use of rationally designed, targeted therapies for patients with NSCLC.

The Combination of Antiangiogenic and Cytotoxic Agents in the Treatment of Prostate Cancer

Metastatic prostate cancer is one of the leading causes of cancer death in men. Although initially responsive to hormone therapy, it eventually progresses in almost all patients. For this reason, there has been a search for novel agents to use in the fight against androgen-independent prostate cancer. Antiangiogenesis is a relatively new antitumor strategy that has been employed in the treatments of many malignancies. As prostate cancer is likely dependent on angiogenesis for its growth and progression, it would logically serve as a good target for this modality. Initially met with great enthusiasm, antiangiogenic drugs have seen only limited success when used as single agents. This has been attributed to many possible etiologies including lack of cytotoxicity and use in situations of large tumor burden. In order to overcome these problems, many investigators are combining antiangiogenic agents with more traditional cytotoxic chemotherapy regimens in hope of augmenting the effects of either drug alone. This article will review the background of angiogenesis inhibition and the use of such combinations in metastatic prostate cancer.

Identification of peptide substrates for human MMP-11 (stromelysin-3) using phage display

The MMP-11 proteinase, also known as stromelysin-3, probably plays an important role in human cancer because MMP-11 is frequently overexpressed in human tumors and MMP-11 levels affect tumorogenesis in mice. Unlike other MMPs, however, human MMP-11 does not cleave extracellular matrix proteins, such as collagen, laminin, fibronectin, and elastin. To help identify physiologic MMP-11 substrates, a phage display library was used to find peptide substrates for MMP-11. One class of peptides containing 26 members had the consensus sequence A(A/Q)(N/A) downward arrow (L/Y)(T/V/M/R)(R/K), where downward arrow denotes the cleavage site. This consensus sequence was similar to that for other MMPs, which also cleave peptides containing Ala in position 3, Ala in position 1, and Leu/Tyr in position 1', but differed from most other MMP substrates in that proline was rarely found in position 3 and Asn was frequently found in position 1. A second class of peptides containing four members had the consensus sequence G(G/A)E downward arrow LR. Although other MMPs also cleave peptides with these residues, other MMPs prefer proline at position 3 in this sequence. In vitro assays with MMP-11 and representative peptides from both classes yielded modest kcat/Km values relative to values found for other MMPs with their preferred peptide substrates. These reactions also showed that peptides with proline in position 3 were poor substrates for MMP-11. A structural basis for the lower kcat/Km values of human MMP-11, relative to other MMPs, and poor cleavage of position 3 proline substrates by MMP-11 is provided. Taken together, these findings explain why MMP-11 does not cleave most other MMP substrates and predict that MMP-11 has unique substrates that may contribute to human cancer.

Anti-tumor activity of the novel angiogenesis inhibitor anginex

Anginex is a novel cytokine-like peptide with potent anti-angiogenic activity, which operates specifically against angiogenically-activated endothelial cells via prevention of cell adhesion/migration on the extracellular matrix and subsequent induction of apoptosis. Here, we demonstrate that anginex inhibits tumor growth in vivo in mouse xenograft models. In the MA148 ovarian carcinoma model, tumor growth was inhibited dose-dependently by up to 80% when systemically administered via osmotic mini-pumps starting at the time of tumor cell inoculation. The optimal dose was found to be 10 mg/kg per day. When tested against established tumors, mini-pump-administered anginex demonstrated essentially the same effectivity at this optimal dose, whereas once or twice-daily injections were only half as effective. When anginex was conjugated to human serum albumin, effectivity was significantly improved, most likely due to increased bioavailability of the conjugate. Immunohistochemical analysis of microvessel density indicated that the anti-tumor activity of anginex is mediated by angiogenesis inhibition. This was confirmed in an in vitro angiogenesis assay based on tube formation in a collagen gel. Animals demonstrated no signs of toxicity as judged by unaltered behavior, normal weight gain, blood markers and macro- and microscopic morphology of internal organs upon autopsy. Overall, these in vivo studies indicate that anginex is an effective anti-tumor agent.