Synthetic inhibitor of matrix metalloproteinases (batimastat) reduces prostate cancer growth in an orthotopic rat model

New Derivatives of N-Hydroxybutanamide: Preparation, MMP Inhibition, Cytotoxicity, and Antitumor Activity

Using a novel method of N-substituted succinimide ring opening, new N-hydroxybutanamide derivatives were synthesized. These compounds were evaluated for their ability to inhibit matrix metalloproteinases (MMPs) and their cytotoxicity. The iodoaniline derivative of N1-hydroxy-N4-phenylbutanediamide showed the inhibition of MMP-2, MMP-9, and MMP-14 with an IC50 of 1-1.5 μM. All the compounds exhibited low toxicity towards carcinoma cell lines HeLa and HepG2. The iodoaniline derivative was also slightly toxic to glioma cell lines A-172 and U-251 MG. Non-cancerous FetMSC and Vero cells were found to be the least sensitive to all the compounds. In vivo studies demonstrated that the iodoaniline derivative of N1-hydroxy-N4-phenylbutanediamide had low acute toxicity. In a mouse model of B16 melanoma, this compound showed both antitumor and antimetastatic effects, with a 61.5% inhibition of tumor growth and an 88.6% inhibition of metastasis. Our findings suggest that the iodoaniline derivative of N1-hydroxy-N4-phenylbutanediamide has potential as a lead structure for the development of new MMP inhibitors. Our new synthetic approach can be a cost-effective method for the synthesis of inhibitors of metalloenzymes with promising antitumor potential.

Specific Inhibitor of Matrix Metalloproteinase Decreases Tumor Invasiveness After Radiofrequency Ablation in Liver Tumor Animal Model

Objective

To determine whether the specific inhibitor of matrix metalloproteinase (MMP)-batimastat (BB-94)-could decrease the progression of liver tumor after radiofrequency ablation (RFA) and achieve better therapeutic efficacy in an animal model.

Methods

In vitro experiments, the proliferation of H22 liver tumor cells was detected by CCK 8 assay and cell migration was detected by Transwell method. In vivo experiments, H22 murine liver tumors were used. First, 32 mice with one tumor were randomized into four groups (n = 8 each group): control (PBS only), RFA alone (65°C, 5 min), BB-94 (30 mg/kg), RFA+BB-94. The growth rate of the residual tumor and the end point survival were calculated and the pathologic changes were evaluated. Secondly, a total of 48 tumors in 24 animals (paired tumors) were randomized into three groups (n = 8 each group): control, RFA alone, RFA+BB-94. Each mouse was implanted with two tumors subcutaneously, one tumor was treated by RFA and the other was evaluated for distant metastasis after applying BB-94.

Results

In vitro, the proliferation assay demonstrated higher proliferation ability after heat treatment (0.82 ± 0.07 vs 1.27 ± 0.08, P = 0.008), and it could be inhibited by BB-94 (1.27 ± 0.08 vs 0.67 ± 0.06, P = 0.001). In the cell migration assay, the H22 cells demonstrated enhanced tumor invasiveness in the heat group than the control group (33.7 ± 2.1 vs 19.7 ± 4.9, P = 0.011). And it could be significantly suppressed after BB-94 incubation (33.7 ± 2.1 vs 23.0 ± 4.6, P = 0.009). With one tumor animal, the growth rate of the residual tumor in the BB-94+RFA group was slower than that in the RFA alone group (P = 0.003). And combination of BB-94 could significantly prolong the survival of the mice (40.3 ± 1.4d vs 47.1 ± 1.3d, P = 0.002). The expression of CD31 and VEGF at the coagulation margin were decreased after combined with BB-94. With two tumors animal, the growth of metastasis tumor in the BB-94+RFA group was slower than that in the RFA group (P < 0.001).

Conclusion

BB-94 combined with RFA reduced the invasiveness of the liver tumor and improved the end-point survival. Our data suggested that targeting the MMP process with the specific inhibition could help to increase overall ablation efficacy.

Depressive-like behaviours and decreased dendritic branching in the medial prefrontal cortex of mice with tumors: A novel validated model of cancer-induced depression

Depression is commonly comorbid in cancer patients and has detrimental effects on disease progression. Evidence suggests that biological mechanisms may induce the onset of cancer-induced depression (CID). The present investigation aims to establish a validated preclinical animal model of CID. Female BALB/c mice were allocated to four groups: control (n=12), chronic oral exposure to corticosterone (CORT) (n=12), CORT exposure followed by chronic low dose fluoxetine (FLX) treatment (n=12), and subcutaneous inoculation of 4T1 mammary carcinoma cells (n=13). Anhedonia was evaluated using the sucrose preference test (SPT), and behavioural despair was evaluated using the forced swim test (FST) and tail suspension test (TST). Sholl analyses were used to examine the dendritic morphology of Golgi-Cox impregnated neurons from the medial prefrontal cortex (mPFC). CORT exposure and tumor burden were both associated with decreased sucrose preference, increased FST immobility, and decreased basilar and apical dendritic branching of neurons in the mPFC. CORT-induced behavioural and dendritic morphological changes were reversible by FLX. No differences in TST immobility were observed between groups. On the secondary TST outcome measure, CORT exposure and tumor burden were associated with a trend towards decreased power of movement. CORT exposure induced a positive control model of a depressive-like state, with FLX treatment confirming the predictive validity of the model. This verified the sensitivity of behavioural and histological tests, which were used to assess the CID model. The induction of a depressive-like state in this model represents the first successfully validated animal model of CID.

Roles of matrix metalloproteinases and their natural inhibitors in prostate cancer progression

Matrix metalloproteinases (MMPs), a group of zinc-dependent endopeptidases involved in the degradation of the extracellular matrix, play an important role in tissue remodeling associated with various physiological processes such as morphogenesis, angiogenesis, and tissue repair, as well as pathological processes including cirrhosis, arthritis and cancer. The MMPs are well established as mediators of tumor invasion and metastasis by breaking down connective tissue barriers. Although there has been a vast amount of literature on the role of MMPs in invasion, metastasis and angiogenesis of various cancers, the role of these endopeptidases in prostate cancer progression has not been systematically reviewed. This overview summarizes findings on the tissue and blood expression of MMPs, their function, regulation and prognostic implication in human prostate cancer, with a focus on MMP-2, -7, -9, MT1-MMP and tissue inhibitor of metalloproteinase 1 (TIMP-1). This review also summarizes the efficacy and failure of early-generation matrix metalloproteinase inhibitors (MMPIs) in the treatment of metastatic prostate cancer and highlights the lessons and challenges for next generation MMPIs.

Ultrasound molecular imaging of VEGFR2 in a rat prostate tumor model using BR55

OBJECTIVES

To evaluate BR55, a new VEGFR2-specific ultrasound contrast agent, for imaging prostate tumors in an orthotopic model in the rat.

MATERIALS AND METHODS

Rat prostate adenocarcinoma were established by injection of G Dunning R-3327 tumor cells in one lobe of the prostate of Copenhagen rats. Imaging experiments were performed with BR55, SonoVue, and streptavidin-functionalized microbubbles coupled with an anti-vascular endothelial growth factor receptor 2 (VEGFR2) antibody using a clinical ultrasound scanner. Contrast enhancement in the tumor and healthy prostate was followed over time by intermittent imaging at low acoustic power. Signal quantification and statistical analysis were performed in the tumor and healthy tissue to compare the behavior of the 3 contrast agents. Immunohistochemistry was performed on the prostate and tumor specimen to determine the expression of VEGFR2.

RESULTS

Comparable contrast enhancement was observed in tumors at peak intensity for BR55 and SonoVue. Then, once unbound microbubbles had cleared from the circulation, a strong enhancement of the tumor was obtained with BR55, whereas no significant microbubble accumulation was detected in the healthy prostate tissue. SonoVue microbubbles were rapidly eliminated, and no significant binding was observed in the tumor. The tumor to prostate ratio calculated after signal quantification was about 20 for the 3 doses of BR55 tested. The enhancement obtained with BR55 in the tumor was not significantly different from the one observed with antibody-coupled streptavidin microbubbles. Intense staining for VEGFR2 was detected in the tumor vessels by immunohistochemistry.

CONCLUSIONS

This study showed that BR55 binding to prostate tumors resulted in a strong enhancement of the lesions as early as a few minutes after contrast injection, whereas minimal nonspecific accumulation occurred in the healthy part of the gland. BR55, like SonoVue, provide information on tissue perfusion during the early vascular phase, but BR55 binding to the tumoral endothelium allows to gain additional information by highlighting the sites of active angiogenesis. The late phase enhancement of the tumor should be particularly valuable for prostate cancer detection and for biopsy guidance.

Matrix metalloproteinase inhibitor batimastat alleviates pathology and improves skeletal muscle function in dystrophin-deficient mdx mice

Duchenne muscular dystrophy (DMD), caused by mutations in the dystrophin gene, involves severe muscle degeneration, inflammation, fibrosis, and early death in afflicted boys. Matrix metalloproteinases (MMPs) are extracellular proteases that cause tissue degradation in several disease states. In this study, we tested the hypothesis that the expression levels of various MMPs are abnormally increased and that their inhibition will ameliorate muscle pathogenesis in animal models of DMD. Our results show that the transcript levels of several MMPs are significantly up-regulated, whereas tissue inhibitors of MMPs are down-regulated, in dystrophic muscle of mdx mice. Chronic administration of batimastat (BB-94), a broad spectrum peptide inhibitor of MMPs, reduced necrosis, infiltration of macrophages, centronucleated fibers, and the expression of embryonic myosin heavy chain in skeletal muscle of mdx mice. Batimastat also reduced the expression of several inflammatory molecules and augmented the levels of sarcolemmal protein beta-dystroglycan and neuronal nitric oxide in mdx mice. In addition, muscle force production in isometric contraction was increased in batimastat-treated mdx mice compared with those treated with vehicle alone. Furthermore, inhibition of MMPs using batimastat reduced the activation of mitogen-activated protein kinases and activator protein-1 in myofibers of mdx mice. Our study provides the novel evidence that the expression of MMPs is atypically increased in DMD, that their inhibition ameliorates pathogenesis, and that batimastat could prove to be a significant candidate for DMD therapy.

Inhibition of metalloproteinases derived from tumours: new insights in the treatment of human glioblastoma

Glioblastoma multiforme is the most commonly diagnosed malignant primary brain tumour in adults. Invasive behaviour is the pathological hallmark of malignant gliomas; consequently, its inhibition has been suggested as a therapeutic strategy. Tumour cell-derived gelatinases (matrix metalloproteinase-2, matrix metalloproteinase-9) can be considered prime factors in glioma invasiveness: their expression correlates with the progression and the degree of malignancy. Thus, broad spectrum matrix metalloproteinase inhibitors (MMP inhibitors) have been included in clinical trials. In the present study, the invasiveness, viability and progression of the human glioma cell line U87MG were investigated following treatment with N-O-isopropyl sulfonamido-based hydroxamates (compounds 1 and 2) as MMP-2 inhibitors used at nanomolar concentration. A standard broad spectrum MMP-inhibitor belonging to the classical tertiary sulfonamido-based hydroxamates family (CGS_27023A) was used too. The compounds 1 and 2 resulted in potent inhibition of cell invasiveness (P<0.0001) without affecting viability. In some clinical trials, the combined therapy of temozolomide (an alkylating agent used in glioma treatment) plus marimastat (a broad spectrum MMP inhibitor) has provided evidence of the importance of MMPs to tumor progression and invasiveness. On this basis, the effect on U87MG cells of a combined treatment with temozolomide, plus each of the two MMP inhibitors at nanomolar concentration, was investigated. The obtained data demonstrated the inhibition of cell invasiveness and viability after treatment. These results can help in developing clinical combined therapy using MMP inhibitors that, at low doses, increase the anticancer efficacy of chemotherapeutic drugs, probably without causing the side effects typical of broad-spectrum MMP inhibitors.

Tackling EGFR signaling with TACE antagonists: a rational target for metalloprotease inhibitors in cancer

TNF-alpha converting enzyme (TACE/ADAM17) is a transmembrane metalloprotease that plays a key role in the cleavage and mobilization of receptor ligands that are initially synthesized as membrane-tethered precursors. For many years, attention has focused on the role of TACE-dependent TNF-alpha cleavage in arthritis and, more recently, it has become apparent that TACE also plays an important role in regulating epidermal growth factor receptor activity in several tumor types. This review presents the background to these findings and a rationale for the continued development of TACE inhibitors for the treatment of epidermal growth factor receptor-dependent epithelial tumors.

Impact of stroma on the growth, microcirculation, and metabolism of experimental prostate tumors

In prostate cancers (PCa), the formation of malignant stroma may substantially influence tumor phenotype and aggressiveness. Thus, the impact of the orthotopic and subcutaneous implantations of hormone-sensitive (H), hormone-insensitive (HI), and anaplastic (AT1) Dunning PCa in rats on growth, microcirculation, and metabolism was investigated. For this purpose, dynamic contrast-enhanced magnetic resonance imaging and (1)H magnetic resonance spectroscopy ([(1)H]MRS) were applied in combination with histology. Consistent observations revealed that orthotopic H tumors grew significantly slower compared to subcutaneous ones, whereas the growth of HI and AT1 tumors was comparable at both locations. Histologic analysis indicated that glandular differentiation and a close interaction of tumor cells and smooth muscle cells (SMC) were associated with slow tumor growth. Furthermore, there was a significantly lower SMC density in subcutaneous H tumors than in orthotopic H tumors. Perfusion was observed to be significantly lower in orthotopic H tumors than in subcutaneous H tumors. Regional blood volume and permeability-surface area product showed no significant differences between tumor models and their implantation sites. Differences in growth between subcutaneous and orthotopic H tumors can be attributed to tumor-stroma interaction and perfusion. Here, SMC, may stabilize glandular structures and contribute to the maintenance of differentiated phenotype.

1alpha,25-Dihydroxyvitamin D3 enhances proliferation of rat prostate cancer cells in the presence of living bone

1alpha,25-Dihydroxyvitamin D(3) (1alpha,25(OH)(2)D(3)) is known to inhibit prostate cancer cells in vitro. Its effects on proliferation in the presence of living bone have not been reported, but are especially relevant since much of the morbidity and mortality associated with prostate cancer is due to metastatic bone disease. We investigated the effect of 1alpha,25(OH)(2)D(3) on MatLyLu-beta(2) cells (MatLyLu cells), a rat prostate cancer line, co-cultured in transwells with living rat calvaria. Cultures of MatLyLu cells with living calvaria treated with 1alpha,25(OH)(2)D(3) exhibited a statistically significant increase in proliferation (range 1.4 to 1.7-fold; p<0.05). Cultures of MatLylu cells alone, with spleen cells, muscle tissue, or with living or inactivated calvarial bone showed no differences in proliferation. To investigate the mechanism for enhanced proliferation, Galardin, a matrix metalloproteinase (MMP) inhibitor, or pamidronate, an antiresorptive agent, was added. Enhanced proliferation was prevented by either agent, but not to an equal extent. The presence of 1alpha,25(OH)(2)D(3) may lead to proteolytic release or activation of growth factors from bone. These results may explain the variability in reports on the in vivo effects of Vitamin D and suggest a potential concern in using Vitamin D or its analogs alone in patients with metastatic prostate cancer.

Inhibition of estrogen-induced pituitary tumor growth and angiogenesis in Fischer 344 rats by the matrix metalloproteinase inhibitor batimastat

The development of estrogen-induced pituitary prolactinoma in Fischer 344 (F344) rats is associated with enhanced neovascularization. Based on the significance of matrix metalloproteinases (MMPs) for tumor growth and angiogenesis, we have studied the effect of batimastat (BB-94), a synthetic MMPs inhibitor (MMPI) on the progression of prolactin-secreting pituitary adenoma in rats. Pituitary tumors were induced in male F344 rats by s.c. implantation of Silastic tubes containing diethylstilbestrol (DES). The effects of chronic treatment with BB-94 (30 mg/kg b.w.) on pituitary weight, cell proliferation, apoptosis and vascular density were evaluated. We have stated that chronic treatment with batimastat caused a significant reduction in the pituitary weight. Batimastat has been found to decrease cell proliferation evaluated by a number of PCNA-positive stained cell nuclei. A marked increase in the apoptotic index within the pituitary was observed in the study group. Moreover, the density of microvessels identified by CD31 was reduced in the group treated with BB-94. The results of our study provide evidence for an inhibitory effect of batimastat, a synthetic MMPI, on the growth and angiogenesis in an experimental model of human prolactinoma. The ability of BB-94 to suppress established pituitary tumor growth suggests a possible application of MMPIs in the treatment of pituitary adenomas.

Enhanced inhibitory effect of the matrix metalloproteinase inhibitor Ro 28-2653 in combination with estramustine and etoposide on the prostate carcinoma in the rat Dunning orthotopic tumor model

PURPOSE

Therapeutic efficacy of the novel matrix metalloproteinase (MMP) inhibitor Ro 28-2653 has been shown in various models of different tumor entities. We hypothesized that the inhibitor effect of Ro 28-2653 on the tumor growth could be improved by combination with chemotherapeutic drugs and examined therefore the effect of Ro 28-2653 alone and in combination with etoposide or estramustine in the MatLyLu Dunning R-3327 rat tumor model characteristic for the androgen-independent prostate cancer (PCa).

METHODS

In vitro effects were estimated measuring the proliferation of MatLyLu cells incubated with the three agents alone or in combination using the XTT test. The in vivo effects of the agents alone or in combination were examined by measuring the tumor weight 18 days after tumor cell injection.

RESULTS

The proliferation rate was only inhibited by etoposide while that effect was increased in combination with Ro 28-2653 and estramustine. Ro 28-2653 reduced the tumor weight by 86%. That effect was significantly increased in combination with etoposide to 92%.

CONCLUSIONS

The inhibitory effect of the MMP inhibitor Ro 28-2653 on the tumor growth in the Dunning PCa model is enhanced by the standard chemotherapeutic drug etoposide. A combined application of both agents could be considered as potential tool to improve the therapy of patients with advanced PCa after failure of hormonal treatment.

Matrix metalloproteinase inhibitor Ro 28-2653 in combination with estramustine: tumor-reducing effects on hormone-sensitive prostate cancer in rats

Therapeutic efficacy of the novel matrix metalloproteinase (MMP) inhibitor, Ro 28-2653 (5-biphenyl-4-yl-5-[4-(-nitro-phenyl)-piperazin-1-yl]-pyrimidine-2,4,6-trione), has been shown in various models of different tumor entities. The tumor growth-reducing effect has been demonstrated in the orthotopic rat prostate Dunning model (subline MatLyLu). Based on these results we investigated Ro 28-2653 in combination with estramustine on the G subline of the Dunning tumor. This subline is characterized by a low metastatic ability and androgen sensitivity. Efficacy was determined by recording tumor growth in vivo by magnetic resonance imaging (MRI). Tumor cells were injected into the prostates of 81 Copenhagen rats. MRI was performed at day 100 and at day 126 after tumor cell injection. The duration of therapy was 17 days with daily oral application of Ro 28-2653 (100 mg/kg) and four i.p. injections of estramustine (7.5 mg/kg). Histological evaluations were conducted to provide further information about the effects on tumor morphology. Orthotopic tumor induction was successful in 100% of the animals. Tumor volume calculations with MRI showed a significant difference between the control groups, the animals treated with Ro 28-2653, and the animals treated with the combination of Ro 28-2653 and estramustine. The new MMP inhibitor Ro 28-2653 reduces tumor growth and provides a compatible therapeutic alternative for patients with prostate cancer.

Angiogenesis and prostate cancer tumor growth

The initiation of new blood vessels through angiogenesis is critical to tumor growth. Tumor cells release soluble angiogenic factors that induce neovascularization, without which nutrients and oxygen would not be available to allow tumors to grow more than 2-3 mm in diameter. This "angiogenic switch" or angiogenic phenotype requires an imbalance between proangiogenic and antiangiogenic factors since the formation of new blood vessels is highly regulated. This review discusses angiogenesis mediators, and the potential for manipulation of angiogenic factors as a practical cancer therapy, particularly in prostate cancer.

Dynamic Magnetic Resonance Tomography and Proton Magnetic Resonance Spectroscopy of Prostate Cancers in Rats Treated by Radiotherapy

RATIONALE AND OBJECTIVES

To establish an experimental setting for monitoring perfusion and metabolism in orthotopic prostate cancer at 1.5 T using dynamic contrast-enhanced magnetic resonance imaging (DCE MRI) and 1H-MR spectroscopy (MRS).

METHODS

Dunning rat prostate cancer cells were injected into the prostate by open surgery. Twelve tumor-bearing rats (5 of these irradiated) and 6 healthy controls were followed up using gadolinium-diethylenetriaminepentaacetic acid -enhanced dynamic MRI and 1H-MRS. Amplitude and the exchange rate constant kep were calculated (2-compartment model). From 1H-MR spectra, ratios of choline (Cho) and creatine (tCr) were calculated. All tumors were examined histologically.

RESULTS

On DCE MRI parameter maps, tumors showed increased vascularization. kep and microvessel density were correlated (r = 0.97). Tumors showed elevated Cho/tCr and an unexpected lipid fraction (2.0-2.2 parts per million). Irradiation slowed tumor growth significantly. Changes of perfusion and metabolism could be detected in all tumors during follow up.

CONCLUSION

DCE MRI and 1H-MRS has potential to characterize orthotopic Dunning prostate cancer in rats, which is a promising model similar to human prostate carcinomas.

Angiogenesis in prostate cancer: its role in disease progression and possible therapeutic approaches

The interaction between cancer cells and their microenvironment is a promising area for the development of novel therapeutic anti-cancer modalities. The formation of new blood vessels, angiogenesis, is an important step in cancer progression. Angiogenesis is a complex multistep process involving close orchestration of endothelial cells, extracellular matrix, and soluble factors. Essentially every step has been found to be regulated by inducers and inhibitors. Prostate cancer has the ability to produce angiogenic factors such as metalloproteinases, vascular endothelial growth factor, fibroblast growth factor 2, transforming growth factor-beta and cyclooxygenase-2. In several studies in prostate cancer an increased microvessel density is associated with poorer prognosis. On the other hand several endogenous inhibitors of angiogenesis have been described in prostate cancer e.g., angiostatin, endostatin, prostate specific antigen (PSA), thrombospondin-1, interleukin 10, interferons and retinoids. The expanding insight in the process of angiogenesis has resulted in a large number of pharmaceutical agents that have been tested in preclinical studies and are currently tested in clinical trials. These agents inhibit endothelial cell proliferation or migration and induce apoptosis. This ultimately will affect the formation of new vessels thereby inducing tumor dormancy. Because antiangiogenic treatment is cytostatic rather than cytotoxic, patients will need long-term therapy to prevent regrowth of the tumor. Prostate cancer is an ideal tumor for antiangiogenic studies because of the availability of a reliable tumor marker, PSA, the indolent clinical course of this cancer and the low rate of proliferation even in metastatic sites. Furthermore, clinical studies showed limited side effects, which is advantageous in this elderly patient group. Whether the ultimate antiangiogenic treatment is effective as a single agent or in combination with radiation therapy, chemotherapy or immunotherapy remains to be determined.

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.

The new synthetic matrix metalloproteinase inhibitor (Roche 28-2653) reduces tumor growth and prolongs survival in a prostate cancer standard rat model

The therapeutic efficacy of synthetic inhibitors of matrix-metalloproteinases (MMPs) in various cancers has been demonstrated. A novel inhibitor, Ro 28-2653, with high selectivity for MMP2, MMP9 and membrane type 1-MMP was evaluated in an orthotopic prostate cancer rat model. Efficacy was determined by recording tumor growth and survival endpoints. Prostate cancer was induced by inoculating R3327 Dunning tumor cells (MatLyLu) into the ventral lobe of the prostates of 148 Copenhagen rats. Daily oral treatment with Ro 28-2653 (10-300 mg/kg per day) was started on day 1 or on day 6 after tumor cell injection. Animals were sacrificed on day 20 for determination of tumor weights. For survival studies, rats received daily oral Ro 28-2653 (100 mg/kg per day) or vehicle for up to 30 days. Tumor induction was successful in 100% of the animals. Ro 28-2653 reproducibly reduced the tumor weights by up to 90% in a dose-dependent manner. In addition, an inhibitory effect in rats with established tumors (treatment start at day 6) was shown. A significantly prolonged survival of Ro 28-2653-treated rats was also demonstrated. Selective inhibition of MMP activity is a novel therapeutic approach, which bears promise for studies in patients with prostate cancer.

Matrix metalloproteinases-2 and 9 do not play a role in the growth of preneoplastic liver lesions in F344 rats

Matrix metalloproteinases- (MMPs) 2 and 9 (gelatinases A and B) have been implicated in tumor invasion and metastasis, and recent studies have shown increased levels of these enzymes during recovery from partial hepatectomy (PH) in rats. F344 rats are highly susceptible to the growth of glutathione S-transferase 7-7- (GST 7-7) positive preneoplastic liver lesions promoted using the modified resistant hepatocyte (RH) protocol. Since the RH protocol consists of 2-acetylaminofluorene (2-AAF) followed by a PH, we reasoned that MMP-2 and -9 might be critical for the growth of lesions. Using gelatin zymography, we examined the expression of these enzymes in the livers of F344 rats treated with the RH protocol and sacrificed on Days 2, 4, 7, 14, and 21 after 2-AAF/PH. We found increases in both pro- and active MMP-2 and -9 over baseline levels, with the highest levels occurring on Day 7 post-PH. Also, a 54-kDa band, likely to be proMMP-1, was elevated in a pattern similar to MMP-2 and -9. In contrast to F344 rats, identically treated Copenhagen rats that are highly resistant to promotion of liver lesion growth using the RH protocol had significantly lower levels of proMMP-1 and -2. To test the importance of these MMPs to the growth of liver lesions, F344 rats that had been initiated with diethylnitrosamine were treated using the RH protocol. They then received either the MMP inhibitor batimastat (30 mg/kg, intraperitoneally) or vehicle alone daily from Day 3 to 20 post-PH and were sacrificed on Day 21. There were no differences in the percentage of liver volume occupied by GST 7-7-positive lesions (19.1 +/- 4.84 vs 19.4 +/- 3.31, treated versus vehicle, mean +/- SEM) or liver weight as a percentage of body weight (4.11% +/- 0.15 vs 4.07% +/- 0.18, treated versus vehicle, mean +/- SEM) between the treated and control groups. Treatment of rats with batimastat clearly did not affect lesion growth or liver regeneration following the RH protocol. These results suggest that increases in gelatinase expression during the RH protocol are a result of the promotional stimulus rather than a mechanism by which 2-AAF/PH causes lesion growth.