TNP-470 (AGM-1470): mechanisms of action and early clinical development

Fumagillin regulates stemness and malignancies in cancer stem-like cells derived from liver cancer via targeting to MetAP-2

BACKGROUND

Cancer relapse is associated with the presence of cancer stem-like cells (CSCs), which lead to multidirectional differentiation and unrestricted proliferative replication. Fumagillin, a myocotoxin produced by the saprophytic filamentous fungus Aspergillus fumigatus, has been reported to affect malignant characteristics in hepatocellular cancer cells. However, its exact role in CSCs is still unknown.

METHODS

CSCs were enriched by culturing cancer cells in serum-free medium. The effects of fumagillin on malignant cell characteristics and mitochondrial function were measured. The regulatory role of fumagillin on methionine aminopeptidase-2 (MetAP-2) was assessed.

RESULTS

When it was supplemented in medium, fumagillin treatment inhibited sphere formation and the maintenance of stemness of CSCs without disturbing cell growth. Fumagillin also decreased stemness-related markers and the aldehyde dehydrogenase 1 (ALDH1)-positive proportion, which demonstrated that fumagillin decreases stemness in CSCs. It was also found to inhibit malignant traits in CSCs, including cell proliferation, invasion, and tumor formation, and sensitize CSCs to chemoagents, including sorafenib and doxorubicin, by promoting chemoagent-induced apoptosis. Moreover, fumagillin treatment was found to disturb mitochondrial membrane homeostasis, ATP synthesis and mitochondrial transcriptional activity. In addition, we found that fumagillin decreased MetAP-2 protein levels and exerted anti-CSC effects potentially by regulating MetAP-2. We also found that fumagillin treatment activated p53 and its transcriptional activity and thus caused cell cycle blockade. Moreover, fumagillin treatment significantly decreased tumor formation in nude mice.

CONCLUSION

This work offers evidence for fumagillin as a specific inhibitor of liver cancer CSCs and proposes a novel strategy for cancer therapy.

Androgen dependent mechanisms of pro-angiogenic networks in placental and tumor development

The placenta and tumors share important characteristics, including a requirement to establish effective angiogenesis. In the case of the placenta, optimal angiogenesis is required to sustain the blood flow required to maintain a successful pregnancy, whereas in tumors establishing new blood supplies is considered a key step in supporting metastases. Therefore the development of novel angiogenesis inhibitors has been an area of active research in oncology. A subset of the molecular processes regulating angiogenesis are well understood in the context of both early placentation and tumorigenesis. In this review we focus on the well-established role of androgen regulation of angiogenesis in cancer and relate these mechanisms to placental angiogenesis. The physiological actions of androgens are mediated by the androgen receptor (AR), a ligand dependent transcription factor. Androgens and the AR are essential for normal male embryonic development, puberty and lifelong health. Defects in androgen signalling are associated with a diverse range of clinical disorders in men and women including disorders of sex development (DSD), polycystic ovary syndrome in women and many cancers. We summarize the diverse molecular mechanisms of androgen regulation of angiogenesis and infer the potential significance of these pathways to normal and pathogenic placental function. Finally, we offer potential research applications of androgen-targeting molecules developed to treat cancer as investigative tools to help further delineate the role of androgen signalling in placental function and maternal and offspring health in animal models.

Dual-therapy with αvβ3-targeted Sn2 lipase-labile fumagillin-prodrug nanoparticles and zoledronic acid in the Vx2 rabbit tumor model

Fumagillin, an unstable anti-angiogenesis mycotoxin, was synthesized into a stable lipase-labile prodrug and incorporated into integrin-targeted lipid-encapsulated nanoparticles (αvβ3-Fum-PD NP). Dual anti-angiogenic therapy combining αvβ3-Fum-PD NP with zoledronic acid (ZA), a long-acting osteoclast inhibitor with proposed anti-angiogenic effects, was evaluated. In vitro, αvβ3-Fum-PD NP reduced (P<0.05) endothelial cell viability without impacting macrophage viability. ZA suppressed (P<0.05) macrophage viability at high dosages but not endothelial cell proliferation. 3D MR neovascular imaging of rabbit Vx2 tumors showed no effect with ZA, whereas αvβ3-Fum-PD NP alone and with ZA decreased angiogenesis (P<0.05). Immunohistochemistry revealed decreased (P<0.05) microvascularity with αvβ3-Fum-PD NP and ZA and further microvascular reduction (P<0.05) with dual-therapy. In vivo, ZA did not decrease tumor macrophage numbers nor cancer cell proliferation, whereas αvβ3-Fum-PD-NPs reduced both measures. Dual-therapy with ZA and αvβ3-Fum-PD-NP may provide enhanced neo-adjuvant utility if macrophage ZA uptake is increased. From the Clinical Editor: Although anti-angiogenesis is one of the treatment modalities in the fight against cancer, many cancers become resistant to VEGF pathway inhibitors. In this article, the authors investigated the use of dual therapy using fumagillin, integrin-targeted lipid-encapsulated nanoparticles (αvβ3- Fum-PD NP) and zoledronic acid (ZA), in both in-vitro and in-vivo experiments. This combination approach may provide an insight to the design of future drugs against cancers.

Reactive stroma in the prostate during late life: The role of microvasculature and antiangiogenic therapy influences

BACKGROUND

Prostate cancer is associated to a reactive stroma microenvironment characterized by angiogenic processes that are favorable for tumor progression. Senescence has been identified as a predisposing factor for prostate malignancies. In turn, the relationships between aging, reactive stroma, and the mechanisms that induce this phenotype are largely unknown. Thus, we investigated the occurrence of reactive stroma in the mouse prostate during advanced age as well as the effects of antiangiogenic and androgen ablation therapies on reactive stroma recruitment.

METHODS

Male mice (52-week-old FVB) were treated with two classes of angiogenesis inhibitors: direct (TNP-470; 15 mg/kg; s.c.) and/or indirect (SU5416; 6 mg/kg; i.p.). Androgen ablation was carried out by finasteride administration (20 mg/kg; s.c.), alone or in association to both inhibitors. The Transgenic Adenocarcinoma of the Mouse Prostate (TRAMP) model was used as a paradigm of cancer-associated reactive stroma. The dorsolateral prostate was collected for α-actin (αSMA), vimentin (VIM), and transforming growth factor-beta (TGF-β) immunohistochemical and Western blotting analyses as well as for CD34/αSMA and CD34/VIM colocalization.

RESULTS

Senescence was associated with increased αSMA, VIM, and TGF-β expression as well as with the recruitment of CD34/αSMA and CD34/VIM dual-positive fibroblasts. These observations were similar to those verified in TRAMP mice. Antiangiogenic treatment promoted the recovery of senescence-associated stromal changes. Hormonal ablation, despite having led to impaired CD34/αSMA and CD34/VIM dual-positive cell recruitment, did not result in decreased stimulus to reactive stroma development, due to enhanced TGF-β expression in relation to the aged controls.

CONCLUSIONS

Reactive stroma develops in the prostate of non-transgenic mice as a result of aging. The periacinar microvasculature is a candidate source for the recruitment of reactive stroma-associated cells, which may be derived either from perivascular-resident mesenchymal stem cells (MSCs) or from an endothelial-to-mesenchymal transition (EndMT) process. Thus, antiangiogenic therapy is a promising approach for preventing age-associated prostate malignancies by means of its negative interference in the development of reactive stroma phenotype from the vascular wall.

Anti-VEGFs hinder bone healing and implant osseointegration in rat tibiae

AIM

To assess the effect of anti-vascular endothelial growth factors (VEGF) on bone healing (defect volume) and implant osseointegration (bone-implant contact per cent) in rat tibia.

MATERIALS AND METHODS

In Sprague-Dawley rats (n = 36), a unicortical defect was created in the right tibia and a titanium implant was placed in the left tibia of each rat. Rats were assigned into three groups and received either anti-vascular endothelial growth factor neutralizing antibody, Ranibizumab or saline (control). Two weeks following surgery, rats were euthanized and bone samples were retrieved. Bone healing and osseointegration were assessed using micro-CT and histomorphometry. One-way anova followed by the Tukey's test was used for data analyses.

RESULTS

The volume of the bone defects in the anti-VEGF group (2.48 ± 0.33 mm(3) ) was larger (p = 0.026) than in the controls (2.11 ± 0.36 mm(3) ) as measured by μ-CT. Bone-implant contact percent in the anti-VEGF (19.9 ± 9.4%) and Ranibizumab (21.7 ± 9.2%) groups were lower (p < 0.00) than in the control group (41.8 ± 12.4%).

CONCLUSIONS

The results of this study suggest that drugs that inhibit the activity of vascular endothelial growth factor (i.e. anti-VEGF) may hinder bone healing and implant osseointegration in rat tibiae.

Prostatic angiogenic responses in late life: antiangiogenic therapy influences and relation with the glandular microenvironment in the transgenic adenocarcinoma of mouse prostate (TRAMP) model

BACKGROUND

Aging is considered one of the main predisposing factors for the development of prostate malignancies. Angiogenesis is fundamental for tumor growth and its inhibition represents a promising therapeutic approach in cancer treatment. Thus, we sought to determine angiogenic responses and the effects of antiangiogenic therapy in the mouse prostate during late life, comparing these findings with the prostatic microenvironment in the Transgenic Adenocarcinoma of Mouse Prostate (TRAMP) model.

METHODS

Male mice (52 week-old FVB) were submitted to treatments with SU5416 (6 mg/kg; i.p.) and/or TNP-470 (15 mg/kg; s.c.). Finasteride was administered (20 mg/kg; s.c.), alone or in association to both inhibitors. The dorsolateral prostate was collected for VEGF, HIF-1α, FGF-2 and endostatin immunohistochemical and Western Blotting analyses and for microvessel density (MVD) count.

RESULTS

Senescence led to increased MVD and VEGF, HIF-1α and FGF-2 protein levels in the prostatic microenvironment, similarly to what was observed in TRAMP mice prostate. The angiogenic process was impaired in all the treated groups, demonstrating significantly decreased MVD. Antiangiogenic and/or finasteride treatments resulted in decreased VEGF and HIF-1α levels, especially following TNP-470 administration, either alone or associated to SU5416. The combination of these agents resulted in increased endostatin levels, regardless of the presence of finasteride.

CONCLUSIONS

Prostatic angiogenesis stimulation during senescence favored the development of neoplastic lesions, considering the pro-angiogenic microenvironment as a common aspect also observed during cancer progression in TRAMP mice. The combined antiangiogenic therapy was more efficient, leading to enhanced imbalance towards angiogenic inhibition in the organ. Finally, finasteride administration might secondarily upregulate the expression of pro-angiogenic factors, pointing to the harmful effects of this therapy.

Synthesis and antiproliferative activity of ligerin and new fumagillin analogs against osteosarcoma

Ligerin (1) is a natural chlorinated merosesquiterpenoid related to fumagillin (2) exhibiting a selective antiproliferative activity against osteosarcoma cell lines and an in vivo antitumor activity in a murine model. Semisynthesis of ligerin analogs was performed in order to study the effects of the C3-spiroepoxide substitution by a halogenated moiety together with the modulation of the C6 chain. Results showed that all derivatives exhibited an in vitro antiproliferative activity against osteosarcoma cell lines and that chlorohydrin compounds were equally or more active than their spiroepoxy analogs. Among semisynthetic analogs, the parent compound 1 was the best candidate for further studies since it exhibited higher or equivalent activity compared to TNP470 (3) against SaOS2 and MG63 human osteosarcoma cells with a four times weaker toxicity against HFF2 human fibroblasts. Quantitative videomicroscopy analysis was conducted and allowed a better understanding of the mechanism of its antiproliferative activity.

Antiangiogenic therapy effects on age-associated matrix metalloproteinase-9 (MMP-9) and insulin-like growth factor receptor-1 (IGFR-1) responses: a comparative study of prostate disorders in aged and TRAMP mice

Senescence is associated with hormonal imbalance and prostatic disorders. Angiogenesis is fundamental for the progression of malignant lesions and is a promising target for prostate cancer treatment. The aim was to characterize matrix metalloproteinase-9 (MMP-9) and insulin-like growth factor receptor-1 (IGFR-1) responses in the prostate during senescence and following antiangiogenic and/or androgen ablation therapies, comparing them to cancer progression features in TRAMP mice. Aged male mice (52-week-old FVB) were submitted to antiangiogenic treatments with SU5416 (6 mg/kg; i.p.) and/or TNP-470 (15 mg/kg; s.c). Finasteride (20 mg/kg; s.c.) was administered alone or associated to both inhibitors. Dorsolateral prostate was collected for light microscopy, and immunohistochemistry and Western blotting collected for MMP-9 and IGFR-1. Senescence led to inflammation and different proliferative lesions in the prostate, as well as to increased MMP-9 and IGFR-1, resembling TRAMP mice prostatic microenvironment. Antiangiogenic therapies promoted recovery and/or interruption of age-associated alterations, presenting differential effects on the molecules studied. SU5416 acted mainly on MMP-9, whereas TNP-470 showed its best influence on IGFR-1 levels. Finasteride administration, alone or in combination with antiangiogenic agents, also resulted in regression of inflammation and neoplastic lesions, besides having a negative modulatory effect on both MMP-9 and IGFR-1. We concluded that stimulated tissue remodeling and proliferative processes during senescence predisposed the prostate to malignant disorders. The combination of different agents was more effective to minimize prostatic imbalance during this period, probably due to the differential action of each drug on factors involved in cell proliferation and extracellular matrix remodeling, resulting in a broader spectrum of effects following the combined treatment.

Autonomous vascular networks synchronize GABA neuron migration in the embryonic forebrain

GABA neurons, born in remote germinative zones in the ventral forebrain (telencephalon), migrate tangentially in two spatially distinct streams to adopt their specific positions in the developing cortex. The cell types and molecular cues that regulate this divided migratory route remains to be elucidated. Here we show that embryonic vascular networks are strategically positioned to fulfill the task of providing support as well as critical guidance cues that regulate the divided migratory routes of GABA neurons in the telencephalon. Interestingly, endothelial cells of the telencephalon are not homogeneous in their gene expression profiles. Endothelial cells of the periventricular vascular network have molecular identities distinct from those of the pial network. Our data suggest that periventricular endothelial cells have intrinsic programs that can significantly mold neuronal development and uncovers new insights into concepts and mechanisms of CNS angiogenesis from both developmental and disease perspectives.

Specific cell targeting with APRPG conjugated PEG-PLGA nanoparticles for treating ovarian cancer

Good biocompatibility, specific tumor targeting, effective drug loading capacity and persistence in the circulation in vivo are imperative prerequisites for the antitumor efficiency of nanoparticles and their further clinical application. In this study, APRPG (Ala-Pro-Arg-Pro-Gly) peptide-modified poly (ethylene glycol)-poly (lactic acid) (PEG-PLA) nanoparticles (NP-APRPG) encapsulating inhibitors of angiogenesis (TNP-470) (TNP-470-NP-APRPG) were fabricated. TNP-470-NP-APRPG was designed to feature maleimide-PEG-PLA and mPEG-PLA as carrier materials, the APRPG peptide for targeting angiogenesis, PEG for prolonging circulation in vivo and PLA for loading TNP-470. TNP-470-NP-APRPG was confirmed to be approximately 130 nm in size with negative ζ-potential (-14.3 mV), narrow distribution (PDI = 0.27) and spherical morphology according to dynamic light scattering (DLS) and transmission electron microscopy (TEM) analyses. In addition, X-ray photoelectron spectra (XPS) analyses confirmed 7.73% APRPG grafting on the TNP-470-NP. In vitro, TNP-470-NP-APRPG exhibited effective inhibition of proliferation, migration and tube formation in human umbilical vein endothelial cells (HUVECs). Similar findings were observed for the retardation of tumor growth in SKOV3 ovarian cancer-bearing mice, suggesting the significant inhibition of angiogenesis and antitumor efficiency of TNP-470-NP-APRPG. Moreover, no obvious toxic drug responses were observed. Further evidence obtained from the immunohistochemical examination demonstrated that the tumor growth inhibition was closely correlated with the high rate of apoptosis among endothelial cells and the effective blockade of endothelial cell proliferation. These results demonstrate that NP-APRPG is a promising carrier for delivering TNP-470 to treat ovarian cancer and that this approach has the potential to achieve broad tumor coverage in the clinic.

Design, synthesis and evaluation of a cellular stable and detectable biotinylated fumagillin probe and investigation of cell permeability of fumagillin and its analogs to endothelial and cancer cells

Fumagillin (1), a natural product of fungal origin, and its analogs were discovered to be extremely potent and highly selective inhibitors restraining endothelial cell proliferation in vitro by covalently binding to MetAP2. In order to further understand the unclear biological mechanisms and pharmacological processes of fumagillin and its derivatives, fumagillin-biotin conjugate 8 was designed and synthesized, which is linked with a 27-atom connection chain and by urethane (carbamate) bonds between fumagillol and D-norbiotinamine. The conjugate 8 shows comparable activity and selectivity against HUVEC proliferation as fumagillin. It was demonstrated that the conjugate 8 is stable inside the cell and its linker is of a suitable length for the detection of biotin in native and denatured conditions. Using the conjugate 8, it was determined that the cell permeability of fumagillin (1) and its analogs are not responsible for their inhibitory activity difference against the proliferation of endothelial and cancer cells. Furthermore, we confidently believe that our present strategy is a versatile and convenient method for investigating drug's cell permeability along with other studies regardless of reversible or irreversible interaction between the drug and binding target/s.

The relationship between the cyclic-RGDfK ligand and αvβ3 integrin receptor

Ever since the finding that αvβ3 integrin receptors are over expressed on the endothelial cell surfaces of tumor vasculatures relative to normal resting vasculatures was disclosed in 1994, αvβ3 integrin receptor selective systems are finding increasing applications both for targeting anti-cancer drugs/genes selectively to tumor vasculatures and for imaging growing tumors. Among the cyclic peptide based integrin antagonists identified through both phage display and structure-activity studies, mainly αvβ3 integrin selective cyclic peptide c(RGDfK-) has found most widespread exploitations for targeting chemotherapeutic drugs/genes to both tumor and tumor vasculatures in anti-angiogenic cancer therapy. Herein we show that a lipopeptide containing widely acclaimed αvβ3 integrin receptor selective cyclic RGDfK ligand in its head-group area can effectively deliver genes into both the endothelial and tumor cells via all the three widely used integrin receptors namely αvβ3, αvβ5 & α5β1 integrins. We demonstrate that intravenous administration of the electrostatic complex of the cationic liposomes of an amphiphiles with cyclic RGDfK head-group and the anti-cancer p53 gene leads to significant tumor growth inhibition in a syngeneic mouse tumor model presumably through inducing apoptosis of tumor neovasculatures. The findings delineated herein provide experimental evidence that cyclic-RGDfK-ligand may not be that highly selective for αvβ3 integrin receptor as is popularly believed.

Antiangiogenic nanotherapy with lipase-labile Sn-2 fumagillin prodrug

BACKGROUND

The chemical instability of antiangiogenic fumagillin, combined with its poor retention during intravascular transit, requires an innovative solution for clinical translation. We hypothesized that an Sn-2 lipase-labile fumagillin prodrug, in combination with a contact-facilitated drug delivery mechanism, could be used to address these problems.

METHODS

α(v)β(3)-targeted and nontargeted nanoparticles with and without fumagillin in the prodrug or native forms were evaluated in vitro and in vivo in the Matrigel™ (BD Biosciences, CA, USA) plug model of angiogenesis in mice.

RESULTS

In vitro experiments demonstrated that the new fumagillin prodrug decreased viability at least as efficacious as the parent compound, on an equimolar basis. In the Matrigel mouse angiogenesis model, α(v)β(3)-fumagillin prodrug decreased angiogenesis as measured by MRI (3T), while the neovasculature was unaffected with the control nanoparticles.

CONCLUSION

The present approach resolved the previously intractable problems of drug instability and premature release in transit to target sites.

Nanotheranostics for personalized medicine

The application of nanotechnology in the biomedical field, known as nanomedicine, has gained much interest in the recent past, as versatile strategy for selective drug delivery and diagnostic purposes. The already encouraging results obtained with monofunctional nanomedicines have directed the efforts of the scientists towards the creation of "nanotheranostics" (i.e. theranostic nanomedicines) which integrate imaging and therapeutic functions in a single platform. Nanotheranostics hold great promises because they combine the simultaneous non-invasive diagnosis and treatment of diseases with the exciting possibility to monitor in real time drug release and distribution, thus predicting and validating the effectiveness of the therapy. Due to these features nanotheranostics are extremely attractive for optimizing treatment outcomes in cancer and other severe diseases. The following step is the attempt to use nanotheranostics for performing a real personalized medicine which will tailor optimized treatment to each patient, taking into account the individual variability. Clinical application of nanotheranostics would enable earlier detection and treatment of diseases and earlier assessment of the response, thus allowing screening for patients which would potentially respond to therapy and have higher possibilities of a favorable outcome. This concept makes nanotheranostics extremely appealing to elaborate personalized therapeutic protocols for achieving the maximal benefit along with a high safety profile. Among the several systems developed up to now, this review focuses on the nanotheranostics which, due to the promising results, show the highest potential of translation to clinical applications and may transform into concrete practice the concept of personalized nanomedicine.

Angiogenesis imaging with vascular-constrained particles: the why and how

Angiogenesis is a keystone in the treatment of cancer and potentially many other diseases. In cancer, first-generation antiangiogenic therapeutic approaches have demonstrated survival benefit in subsets of patients, but their high cost and notable adverse side effect risk have fueled alternative development efforts to personalize patient selection and reduce off-target effects. In parallel, rapid advances in cost-effective genomic profiling and sensitive early detection of high-risk biomarkers for cancer, atherosclerosis, and other angiogenesis-related pathologies will challenge the medical imaging community to identify, characterize, and risk stratify patients early in the natural history of these disease processes. Conventional diagnostic imaging techniques were not intended for such sensitive and specific detection, which has led to the emergence of novel noninvasive biomedical imaging approaches. The overall intent of molecular imaging is to achieve greater quantitative characterization of pathologies based on microanatomical, biochemical, or functional assessments; in many approaches, the capacity to deliver effective therapy, e.g., antiangiogenic therapy, can be combined. Agents with both diagnostic and therapy attributes have acquired the moniker "theranostics." This review will explore biomedical imaging options being pursued to better segment and treat patients with angiogenesis-influenced disease using vascular-constrained contrast platform technologies.

Theragnostics for tumor and plaque angiogenesis with perfluorocarbon nanoemulsions

Molecular imaging agents are extending the potential of noninvasive medical diagnosis from basic gross anatomical descriptions to complicated phenotypic characterizations based upon the recognition of unique cell-surface biochemical signatures. Although originally the purview of nuclear medicine, "molecular imaging" is now studied in conjunction with all clinically relevant imaging modalities. Of the myriad of particles that have emerged as prospective candidates for clinical translation, perfluorocarbon nanoparticles offer great potential for combining targeted imaging with drug delivery, much like the "magic bullet" envisioned by Paul Ehrlich 100 years ago. Perfluorocarbon nanoparticles, once studied in Phase III clinical trials as blood substitutes, have found new life for molecular imaging and drug delivery. The particles have been adapted for use with all clinically relevant modalities and for targeted drug delivery. In particular, their intravascular constraint due to particle size provides a distinct advantage for angiogenesis imaging and antiangiogenesis therapy. As perfluorocarbon nanoparticles have recently entered Phase I clinical study, this review provides a timely focus on the development of this platform technology and its application for angiogenesis-related pathologies.

Nanomedicine strategies for molecular targets with MRI and optical imaging

The science of 'theranostics' plays a crucial role in personalized medicine, which represents the future of patient management. Over the last decade an increasing research effort has focused on the development of nanoparticle-based molecular-imaging and drug-delivery approaches, emerging as a multidisciplinary field that shows promise in understanding the components, processes, dynamics and therapies of a disease at a molecular level. The potential of nanometer-sized agents for early detection, diagnosis and personalized treatment of diseases is extraordinary. They have found applications in almost all clinically relevant biomedical imaging modality. In this review, a number of these approaches will be presented with a particular emphasis on MRI and optical imaging-based techniques. We have discussed both established molecular-imaging approaches and recently developed innovative strategies, highlighting the seminal studies and a number of successful examples of theranostic nanomedicine, especially in the areas of cardiovascular and cancer therapy.

Methionine aminopeptidase 2 over-expressed in cholangiocarcinoma: potential for drug target

Methionine aminopeptidases (MetAP) are proteases which remove the N-terminal methionine from newly synthesized proteins. Associations of MetAP2 with tumor progression of different cancers have been repeatedly reported. We aim to determine if MetAP2 is expressed in cholangiocarcinomas (CCA) and investigate to see if it would be a useful therapeutic target. We evaluated MetAP2 expression by immunohistochemistry in 82 patients of intrahepatic CCA. MetAP2 was expressed in bile ducts to various degrees. It was occasionally expressed with weak staining in normal bile duct epithelium but was strikingly over-expressed in dysplastic bile duct epithelia, primary and metastatic CCA tissues (p < 0.001). The increased expression of MetAP2 in proliferating bile duct was evident. All metastatic tumors had stronger expression of MetAP2 than the corresponding primary tumors. Fumagillin, a MetAP2 specific inhibitor, significantly inhibited cell proliferation in dose dependent manner and the degree of growth inhibition was dependent on the amount of cellular enzyme. The present study highlights the involvement of MetAP2 in an early event of carcinogenesis of CCA. The findings represent the first description of increased MetAP2 expression in CCA. The inhibition of enzyme activity using MetAP2 inhibitors may be a potential strategy for long-term control of tumor development and progression in CCA patients.

Three-dimensional MR mapping of angiogenesis with alpha5beta1(alpha nu beta3)-targeted theranostic nanoparticles in the MDA-MB-435 xenograft mouse model

Our objectives were 1) to characterize angiogenesis in the MDA-MB-435 xenograft mouse model with three-dimensional (3D) MR molecular imaging using alpha(5)beta(1)(RGD)- or irrelevant RGS-targeted paramagnetic nanoparticles and 2) to use MR molecular imaging to assess the antiangiogenic effectiveness of alpha(5)beta(1)(alpha(nu)beta(3))- vs. alpha(nu)beta(3)-targeted fumagillin (50 mug/kg) nanoparticles. Tumor-bearing mice were imaged with MR before and after administration of either alpha(5)beta(1)(RGD) or irrelevant RGS-paramagnetic nanoparticles. In experiment 2, mice received saline or alpha(5)beta(1)(alpha(nu)beta(3))- or alpha(nu)beta(3)-targeted fumagillin nanoparticles on days 7, 11, 15, and 19 posttumor implant. On day 22, MRI was performed using alpha(5)beta(1)(alpha(nu)beta(3))-targeted paramagnetic nanoparticles to monitor the antiangiogenic response. 3D reconstructions of alpha(5)beta(1)(RGD)-signal enhancement revealed a sparse, asymmetrical pattern of angiogenesis along the tumor periphery, which occupied <2.0% tumor surface area. alpha(5)beta(1)-targeted rhodamine nanoparticles colocalized with FITC-lectin corroborated the peripheral neovascular signal. alpha(5)beta(1)(alpha(nu)beta(3))-fumagillin nanoparticles decreased neovasculature to negligible levels relative to control; alpha(nu)beta(3)-targeted fumagillin nanoparticles were less effective (P>0.05). Reduction of angiogenesis in MDA-MB-435 tumors from low to negligible levels did not decrease tumor volume. MR molecular imaging may be useful for characterizing tumors with sparse neovasculature that are unlikely to have a reduced growth response to targeted antiangiogenic therapy.

Minute dosages of alpha(nu)beta3-targeted fumagillin nanoparticles impair Vx-2 tumor angiogenesis and development in rabbits

Fumagillin suppresses angiogenesis in cancer models and clinical trials, but it is associated with neurotoxicity at systemic doses. In this study, alpha(nu)beta(3)-targeted fumagillin nanoparticles were used to suppress the neovasculature and inhibit Vx-2 adenocarcinoma development using minute drug doses. Tumor-bearing rabbits were treated on days 6, 9, and 12 postimplantation with alpha(nu)beta(3)-targeted fumagillin nanoparticles (30 microg/kg), alpha(nu)beta(3)-targeted nanoparticles without drug, nontargeted fumagillin nanoparticles (30 microg/kg) or saline. On day 16, MRI was performed with alpha(nu)beta(3)-targeted paramagnetic nanoparticles to quantify tumor size and assess neovascularity. Tumor volume was reduced among rabbits receiving alpha(nu)beta(3)-targeted fumagillin nanoparticles (470+/-120 mm(3)) compared with the three control groups: nontargeted fumagillin nanoparticles (1370+/-300 mm(3), P<0.05), alpha(nu)beta(3)-targeted nanoparticles without drug (1080+/-180 mm(3), P<0.05) and saline (980+/-80 mm(3), P<0.05). MR molecular imaging of control rabbits (no fumagillin) revealed a predominant peripheral distribution of neovascularity representing 7.2% of the tumor rim volume, which decreased to 2.8% (P<0.05) with alpha(nu)beta(3)-targeted fumagillin nanoparticle treatment. Microscopically, the tumor parenchyma tended to show T-cell infiltration after targeted fumagillin treatment, which was not appreciated in control animals. These results suggest that alpha(nu)beta(3)-targeted fumagillin nanoparticles could provide a safe and effective means to deliver MetAP2 inhibitors alone or in combination with cytotoxic or immunotherapy.

Ectopic expression of methionine aminopeptidase-2 causes cell transformation and stimulates proliferation

Methionine aminopeptidase-2 (MetAP2) processes N-terminal methionine from nascent cellular proteins. Inhibition of MetAP2 has been shown to block angiogenesis and suppress tumor growth in preclinical tumor models. However, the biological role of MetAP2 in cancer is not well understood. We examined the effect of three distinct chemical classes of MetAP2 inhibitors on the growth of a panel of human cancer cells in vitro. All MetAP2 inhibitors caused inhibition of tumor cell growth in both anchorage-dependent and, particularly, in anchorage-independent manner. These data prompted us to examine the possible roles of MetAP2 in cancers. Ectopic expression of MetAP2 in NIH-3T3 cells caused transformation, evidenced by the formation of foci in monolayer culture and growth of large colonies in soft agar. Overexpression of MetAP2 in an immortalized bronchial epithelial cell line NL20 accelerated growth. These phenotypes induced by the overexpression of MetAP2 were reversed by the treatment with MetAP2 inhibitors, indicating that the catalytic function of MetAP2 was essential. Accordingly, overexpression of a catalytically inactive MetAP2 resulted in growth retardation of HT1080 tumor cells, suggesting a dominant-negative role of the inactive MetAP2 mutant. Finally, we analysed the expression of MetAP2 in patient cancer samples by immunohistochemistry. Moderate-to-high staining was identified in the majority of breast, colon, lung, ovarian and prostate carcinomas examined. These data suggest that MetAP2 plays an important role in tumor cell growth and may contribute to tumorigenesis.

Cell-cycle inhibition by TNP-470 in an in vivo model of hepatocarcinoma is mediated by a p53 and p21WAF1/CIP1 mechanism

The objective of this study was to determine in a rat model of hepatocellular carcinoma (HCC) the effects of the antiangiogenic agent TNP-470 on cell proliferation and effectors of the apoptotic pathway, including p53, p21WAF1/CIP1, cyclin D, and cyclin E. Tumor was induced in male Wistar rats by diethylnitrosamine and promoted by two-thirds hepatectomy plus acetaminofluorene administration. Experiments were carried out at 28 weeks after initiating the treatment. TNP-470 was administered at 30 mg/kg, 3 times per week from 20 to 28 weeks. Serum levels of vascular endothelial growth factor (VEGF) and hepatocyte growth factor beta (HGFbeta) liver expression were increased by hepatocarcinogenesis (+38% and +183%, respectively), and treatment with TNP-470 was able to prevent the increase in these angiogenic factors induced by HCC. HCC coursed with reduced expression of p21WAF1/CIP1 and p53 (-63% and -60%, respectively). Hepatic expression of cyclin D and cyclin E were significantly increased in rats with HCC (+108% and +115%, respectively). In animals with experimental carcinogenesis, a significant increase in the expression of Cdk4 and CdK2 was also observed (+119% and +187%, respectively). These effects were prevented by TNP-470 administration. In conclusion, cell-cycle inhibition by TNP-470 is mediated at least in part by an activation of p21WAF1/CIP1 because of a p53-dependent mechanism, with reduction of the cyclin D-Cdk4 and cyclin E-Cdk 2 expression. These cytostatic effects should be considered when assessing the efficacy of TNP-470 for anti-angiogenic therapy. These findings may prove useful for the development of therapies for the treatment of human HCC.

Targeted radionuclide therapy for solid tumors: an overview

Although radioimmunotherapy (RIT) has been effective in non-Hodgkin's lymphoma (NHL) as a single agent, solid tumors have shown less clinically significant therapeutic response to RIT alone. The clinical impact of RIT or other forms of targeted radionuclide therapy for solid tumors depends on the development of a high therapeutic index (TI) for the tumor vs. normal tissue effect, and the implementation of RIT as part of synergistic combined modality therapy (CMRIT). Preclinical and clinical studies have provided a wealth of information, and new prototypes or paradigms have shed light on future possibilities in many instances. Evidence suggests that combination and sequencing of RIT in CMRIT appropriately can provide effective treatment for many solid tumors. Vascular targets provide RIT enhancement opportunities and nanoparticles may prove to be effective carriers for RIT combined with intracellular drug delivery or alternating magnetic frequency (AMF) induced thermal tumor necrosis. The sequence and timing of combined modality treatments will be of critical importance to achieve synergy for therapy while minimizing toxicity. Fortunately, the radionuclide used for RIT also provides a signal useful for nondestructive quantitation of the influence of sequence and timing of CMRIT on events in animals and patients. This can be readily accomplished clinically using quantitative high-resolution imaging (e.g., positron emission tomography [PET]).

Anti-tumor effect of radiation response by combined treatment with angiogenesis inhibitor, TNP-470, in oral squamous cell carcinoma

Blocking angiogenesis may enhance conventional anticancer treatments such as radiation therapy. In this study, we examined the effects of the angiogenesis inhibitor TNP-470 on human OSCC cell lines HSC2 and KB, with combining radiation therapy in the nude mouse. We evaluated cell-induced neovascularization with dorsal air sac assay, and selected two cells (HSC2: low, KB: high) with different level of cell-induced angiogenesis. The angiogenesis inhibitor TNP-470 was given 30 mg/kg s.c. daily on day 1-5, and irradiation, 8 Gy x 1, was administered on day 1 each week for 3 weeks. Significant inhibition of tumor growth relative to untreated controls was achieved in KB cells showing high induced angiogenesis with both TNP-470 (P < 0.01) and radiation (P < 0.01) and combining TNP-470 and radiation (P < 0.01). We saw little effect of TNP-470 either alone or in addition to the effect of radiation on the HSC2 cells showing low induced angiogenesis. These results suggested that TNP-470 significantly enhanced the effect of radiation on the cells with high neovascularization. These findings indicated that individual evaluation of each tumor neovascularization potential will be important before deciding the anti-angiogenesis treatment.

Fumagillin treatment of hepatocellular carcinoma in rats: An in vivo study of antiangiogenesis

AIM: To investigate the effect and possible mechanisms of antiangiogenesis therapy for HCC in rats.

METHODS: Adult male LEW/SsN rats were divided into 3 groups, 25 animals each. Group A was the control group. Groups B and C were given diethylnitrosamine, 5 mg/kg/d. In addition, group C rats received an intraperitoneal injection of fumagillin, 30 mg/(kg·d). Five animals in each group were killed at 6^th, 12^th, 18^th, 20^th and 24^th wk to evaluate the development of HCC and metastasis. Weight of the rats, liver tumors, and number of organs involved by HCC were measured at each stage. We compared methionine aminopeptidase-2 (MetAP-2) mRNA, Bcl-2 mRNA, telomerase mRNA, and telomerase activity at 24^th wk in the liver tissue of group A rats and tumor tissue of HCC from group B and C rats.

RESULTS: No HCC developed in group A, but tumors were present in group B and C rats by the 18^th wk. At wk 20 and 24, the median liver weight in group B was 0.64 g (range: 0.58-0.70 g) and 0.79 g (range: 0.70-0.90 g) (P = 0.04), and that in group C was 0.37 g (range: 0.35-0.42 g) and 0.39 g (range: 0.35-0.47 g) (P = 0.67). The liver weight in group C rats was significantly lower than that in group B rats (P = 0.009). At the same time, the median metastasis score (number of organ systems involved) was 3 (range 2-3) in group B, and 1 (range 1-2) in group C, a significant difference between the groups (P = 0.007, 0.004). The levels of MetAP-2 mRNA were significantly higher in groups B and C than in group A (P = 0.025), and significantly higher in group C than in group B (P = 0.047). The level of Bcl-2 mRNA was significantly higher in group B than in group A (P = 0.024), but lower in group C than in group B, although not significantly (P = 0.072). Telomerase mRNA was significantly higher in group B than in group A (P = 0.025), but significantly lower in group C than in group B (P = 0.016). The same inter-group relationship was also true for telomerase activity (P = 0.025 and 0.046).

CONCLUSION: Fumagillin effectively inhibits both liver tumor growth and metastasis in rats in vivo. A possible mechanism is fumagillin-induced inhibition of MetAP-2, which plays an essential role in endothelial cell proliferation. Inhibition of MetAP-2 also results in inhibition of Bcl-2 and telomerase activity.

Treatment of cells with the angiogenic inhibitor fumagillin results in increased stability of eukaryotic initiation factor 2-associated glycoprotein, p67, and reduced phosphorylation of extracellular signal-regulated kinases

Fumagillin, an angiogenic inhibitor, binds to methionine aminopeptidase 2, which is the same as eukaryotic initiation factor 2-associated glycoprotein, p67. p67 protects eIF2alpha from phosphorylation by its kinases. To understand the importance of fumagillin binding to p67, we measured the level of p67 in mouse C2C12 myoblasts treated with fumagillin. We show that fumagillin increases the stability of p67 by decreasing its turnover rate. The increased levels of p67 result in inhibition of phosphorylation of extracellular signal-regulated kinases 1 and 2 (ERKs 1 and 2). p67 binds to these ERKs, and the 108-480 amino acid segment is sufficient for this binding. p67's affinity to ERKs 1 and 2 also increases in fumagillin-treated myoblasts while its affinity for eIF2alpha remains unchanged. A mutant at the conserved amino acid residue D251A increases the phosphorylation of ERKs 1 and 2 without affecting the binding to p67, thus indicating the importance of this residue in the regulation of the phosphorylation of these ERKs. These results suggest that fumagillin increases the stability of p67 and its affinity to ERKs 1 and 2 and causes the inhibition of the phosphorylation of ERKs 1 and 2.

Synthesis and biological evaluation of novel fumagillin and ovalicin analogues

A promising approach among the numerous efforts to cure cancer is the interruption of the tumour-induced formation of new blood vessels (angiogenesis). By suppressing angiogenesis with drugs, the tumour can neither grow to a life threatening size, nor metastasize. The natural product fumagillin 1 and the structurally related ovalicin 2 are two of the most potent anti-angiogenic compounds. Here, we report the design and synthesis of novel fumagillin and ovalicin analogues lacking reactive epoxy functionalities, which were thought to be responsible for the severe toxic side-effects observed. We also report a new synthetic approach and the determination of the anti-angiogenic properties of these compounds in endothelial cells.

Antiangiogenic strategies in neuroblastoma

Promising new antiangiogenic strategies are emerging for the treatment of cancer and the inhibition of angiogenesis could represent a powerful adjunct to traditional therapy of malignant tumors. Over the last ten years several reports have been published concerning the relationship between tumor progression and angiogenesis in neuroblastoma in experimental models in vitro and in vivo. Moreover, a high vascular index in neuroblastoma correlates with poor prognosis, suggesting dependence of aggressive tumor growth on active angiogenesis. Here, we present an overview of recent advances in antiangiogenesis in neuroblastoma and describe the most important active substances, preclinical and clinical data, as well as future perspectives.

Drug delivery systems for vitreoretinal diseases

The eye has an environment that is specific unto itself in terms of pharmacokinetics: the inner and outer blood-retinal barriers separate the retina and the vitreous from the systemic circulation and vitreous body, which physiologically has no cellular components, occupies the vitreous cavity, an inner space of the eye, and reduces practical convection of molecules. Considering this, development of a drug delivery system (DDS) is becoming increasingly important in the treatment of vitreoretinal diseases not only to facilitate drug efficacy but also to attenuate adverse effects. The DDS has three major goals: enhances drug permeation (e.g., iontophoresis and transscleral DDS), controls release of drugs (e.g., microspheres, liposomes, and intraocular implants), and targets drugs (e.g., prodrugs with high molecular weight and immunoconjugates). Comprehensive knowledge of these should lead to development of innovative treatment modalities.

Clinical and pharmacokinetic study of TNP-470, an angiogenesis inhibitor, in combination with paclitaxel and carboplatin in patients with solid tumors

PURPOSE

Preclinical studies have demonstrated a synergistic effect with the angiogenesis inhibitor TNP-470 and several cytotoxic agents. A recent clinical trial with the combination of paclitaxel and TNP-470 has shown promising effects. The present study was designed to determine the toxicity and pharmacokinetics of carboplatin in combination with TNP-470 in comparison with the doublet regimen of paclitaxel and carboplatin in patients with solid tumors.

EXPERIMENTAL DESIGN

Enrolled in the study were 17 patients with lung (11), head/neck (3), sarcoma (2) and thymoma (1). The patients received intravenous paclitaxel and carboplatin on day 1 followed by TNP-470 (60 mg/m(2) i.v. over 1 h administered thrice weekly on Monday, Wednesday, and Friday). Each cycle of therapy consisted of 3 weeks. The initial cohort of three patients received carboplatin at AUC 5 mg/ml x min. No dose-limiting toxic effects occurred, thus the subsequent cohort received carboplatin at AUC 6 mg/ml x min. In addition to toxicity, the pharmacokinetics of carboplatin were evaluated, and tumor response and patient survival rates were assessed.

RESULTS

The administered regimen of paclitaxel (225 mg/m(2) i.v. over 3 h) and carboplatin (AUC 6 mg/ml x min i.v. over 1 h) on day 1 followed by TNP-470 (60 mg/m(2) i.v. over 1 h administered thrice weekly on Monday, Wednesday, and Friday) was defined as both the maximum tolerated and optimal dose. Hematological toxic effects were similar to those expected with the chemotherapy doublet. All neurocognitive impairments were graded as mild to moderate and reversed after discontinuation of TNP-470 administration. No alterations in the pharmacokinetic disposition of carboplatin were noted. Overall, the median survival duration was 297 days. Four patients (24%) had a partial response, and eight (47%) had stable disease.

CONCLUSIONS

The combination of TNP-470, paclitaxel, and carboplatin is a reasonably well tolerated regimen. Further randomized studies of TNP-470 with this doublet regimen are now warranted for non-small-cell lung carcinoma and other solid tumors.

Blockade of Vascular Endothelial Growth Factor Receptor I (VEGF-RI), but not VEGF-RII, Suppresses Joint Destruction in the K/BxN Model of Rheumatoid Arthritis

It was recently shown that vascular endothelial growth factor (VEGF), a growth factor for endothelial cells, plays a pivotal role in rheumatoid arthritis. VEGF binds to specific receptors, known as VEGF-RI and VEGF-RII. We assessed the physical and histological effects of selective blockade of VEGF and its receptors in transgenic K/BxN mice, a model of rheumatoid arthritis very close to the human disease. Mice were treated with anti-mouse VEGF Ab, anti-mouse VEGF-RI and -RII Abs, and an inhibitor of VEGF-RI tyrosine kinase. Disease activity was monitored using clinical indexes and by histological examination. We found that synovial cells from arthritic joints express VEGF, VEGF-RI, and VEGF-RII. Treatment with anti-VEGF-RI strongly attenuated the disease throughout the study period, while anti-VEGF only transiently delayed disease onset. Treatment with anti-VEGF-RII had no effect. Anti-VEGF-RI reduced the intensity of clinical manifestations and, based on qualitative and semiquantitative histological analyses, prevented joint damage. Treatment with a VEGF-RI tyrosine kinase inhibitor almost abolished the disease. These results show that VEGF is a key factor in pannus development, acting through the VEGF-RI pathway. The observation that in vivo administration of specific inhibitors targeting the VEGF-RI pathway suppressed arthritis and prevented bone destruction opens up new possibilities for the treatment of rheumatoid arthritis.

Angiogenesis inhibition with TNP-470, 2-methoxyestradiol, and paclitaxel in experimental pancreatic carcinoma

INTRODUCTION

Inhibition of tumor angiogenesis is a novel therapeutic modality for various malignancies.

AIM

To investigate the effect of different antiangiogenic agents (TNP-470, 2-methoxyestradiol, and paclitaxel) on growth and neovascularization of experimental pancreatic cancer.

METHODOLOGY

In 25 male Lewis rats, tumor induction was achieved by orthotopic and subcutaneous tumor fragment implantation of ductlike pancreatic cancer DSL6A. Four weeks after tumor implantation, the animals were randomly treated with TNP-470, 2-methoxyestradiol, or paclitaxel. After 2 weeks of antiangiogenic therapy, total tumor volume, vital tumor surface, vascular density, and apoptosis were measured.

RESULTS

Total tumor volume and vital tumor surface were not significantly different in any of the treatment groups. Similarly, vascular density and apoptosis were not altered by treatment with the various angiogenesis inhibitors at the specific doses used.

CONCLUSION

We conclude that in contrast to many earlier studies, angiogenesis inhibition by a single-drug application and by the doses used in the present model did not reveal a favorable therapeutic effect on pancreatic cancer DSL6A. The combination of different angiogenesis inhibitors or higher doses might be more effective.

Noninvasive estimation of tumour viability in a xenograft model of human neuroblastoma with proton magnetic resonance spectroscopy (1H MRS)

The aim of the study was to evaluate proton magnetic resonance spectroscopy ((1)H MRS) for noninvasive biological characterisation of neuroblastoma xenografts in vivo. For designing the experiments, human neuroblastoma xenografts growing subcutaneously in nude rats were analysed in vivo with (1)H MRS and magnetic resonance imaging at 4.7 T. The effects of spontaneous tumour growth and antiangiogenesis treatment, respectively, on spectral characteristics were evaluated. The spectroscopic findings were compared to tumour morphology, proliferation and viable tumour tissue fraction. The results showed that signals from choline (Cho)-containing compounds and mobile lipids (MLs) dominated the spectra. The individual ML/Cho ratios for both treated and untreated tumours were positively correlated with tumour volume (P<0.05). There was an inverse correlation between the ML/Cho ratio and the viable tumour fraction (r=-0.86, P<0.001). Higher ML/Cho ratios concomitant with pronounced histological changes were seen in spectra from tumours treated with the antiangiogenic drug TNP-470, compared to untreated control tumours (P<0.05). In conclusion, the ML/Cho ratio obtained in vivo by (1)H MRS enabled accurate assessment of the viable tumour fraction in a human neuroblastoma xenograft model. (1)H MRS also revealed early metabolic effects of antiangiogenesis treatment. (1)H MRS could prove useful as a tool to monitor experimental therapy in preclinical models of neuroblastoma, and possibly also in children.

Anti-angiogenic agents for the treatment of brain tumors

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

Angiogenesis and anti-angiogenesis in neuroblastoma

Angiogenesis is a biological process by which new capillaries are formed from pre-existing vessels. It occurs in physiological and pathological conditions, such as tumours, where a specific critical turning point is the transition from the avascular to the vascular phase. Tumour angiogenesis depends mainly on the release by neoplastic cells of growth factors specific for endothelial cells that able to stimulate the growth of the host's blood vessels. This review summarises the literature concerning the relationship between angiogenesis and progression in human neuroblastoma, the most common extracranial solid tumour of infancy and childhood. It is becoming increasingly evident that agents which interfere with blood vessel formation also block tumour progression. Accordingly, anti-angiogenic tumour therapy has gained much interest in preclinical and clinical assessments. The recent applications of anti-angiogenic agents which interfere or block neuroblastoma progression are reviewed.

TNP-470 reduces collagen and macrophage accumulation in expanded polytetrafluoroethylene tube implants

BACKGROUND

TNP-470 is a potent angiogenic inhibitor that has been demonstrated to decrease the rate of cutaneous wound healing. This study investigated the effect that TNP-470 has upon collagen growth and macrophage infiltration into expanded polytetrafluoroethylene (e-PTFE) tube implants.

METHODS

e-PTFE tubes (1.0 cm in length) were implanted into the dorsum of male Swiss-Webster mice (8-10 weeks old). TNP-470 was administered subcutaneously in doses of 0.5, 1.0, or 5.0 mg/kg for determination of hydroxyproline accumulation on day 18 after implantation. Additionally, TNP-470 was administered at 5.0 mg/kg for determination of macrophage infiltration on days 4, 8, 13, and 18 after implantation.

RESULTS

Administration of TNP-470 at doses of 1.0 and 5.0 mg/kg on days 0, 2, and 4 significantly (P < 0.05) decreased hydroxyproline accumulation in e-PTFE implants on day 18 after implantation. Administration of 0.5 mg/kg of TNP-470 yielded no significant difference vs the vehicle control (P < 0.81). Additionally, administration of TNP-470 at 5.0 mg/kg on days 0, 2, and 4 significantly (P < 0.05) decreased macrophage infiltration into e-PTFE implants on day 4 after implantation. There was also a significantly (P < 0.05) increased percentage of macrophages in the e-PTFE implants on day 13 after wounding. No significant differences were observed between the experimental and control groups on days 8 and 18.

CONCLUSIONS

Administration of TNP-470 significantly decreases hydroxyproline accumulation in e-PTFE implants. These data suggest that while TNP-470 is administered, macrophage infiltration is impaired; however, upon discontinuing administration, macrophage infiltration increases. Possible mechanisms to account for these findings are discussed.

Antiangiogenic agents and their promising potential in combined therapy

One of the most promising strategies for treating cancer is the addition of antiangiogenic therapy to therapeutic regimens. Angiogenesis, or the growth of new blood vessels from preexisting vessels, is essential both for the growth of a primary tumor and for successful metastasis. As a result of intense research in this field, a number of antiangiogenic agents have been identified and have demonstrated varying degrees of success in inhibiting the growth of solid tumors and metastases in preclinical and clinical studies. The real potential of antiangiogenic agents for cancer therapy resides in strategic combinations with each other, with chemotherapy, with radiation, and with tumor-targeting agents, such as radioimmunotherapy. Along with this new opportunity to develop synergistic therapy comes the challenging complexities of the physiologic systems regulating angiogenesis. These multifaceted systems could intimidate investigators seeking to take advantage of the potential synergy in combined cancer therapy. To aid in these efforts, this overview of key antiangiogenic agent mechanisms, combination strategies and initial studies of the potential synergy with chemotherapy, radiation and radioimmunotherapy is presented.

New agents for prostate cancer

Given the poor results with currently available therapies, it is imperative that new treatments be developed for patients with advanced prostate cancer. The next generation of therapies will include many novel biologic agents targeted at molecular defects in the cancer cell. Investigating the efficacy and safety of these compounds and evaluating their utility in combination with traditional therapies such as chemotherapy or radiotherapy are major goals of prostate cancer clinical research for the next decade.

Effect of TNP-470 (AGM-1470) on the growth of rat rhabdomyosarcoma tumors of different sizes

Potential anticancer therapy with the fumagillin analog TNP-470 was investigated in the present project using subcutaneously growing rhabdomyosarcomas in rats. Specifically, influences of different tumor sizes at the start of treatment as well as dose/schedules were evaluated with this angiogenesis inhibitor. The results show a significant (p = < or = 0.01) reduction of the growth rate, even for relatively large-sized (> 7 cm3) tumors, when 50 mg/kg TNP-470 was used every other day for up to 3 or 5 injections. With 30 mg/kg TNP-470 injections, effects were seen only with tumors measuring < 7 cm3. The histologic examinations demonstrate an increase in necrosis, both in the center and in the peripheral part of TNP-470-treated tumors. Overall, both tumor volume and drug dose determine treatment outcome with the rat rhabdomyosarcoma. The results suggest that angiogenesis inhibitors could represent a valid component in the treatment of progressive tumor growth, also of large tumors as often encountered in clinics. The antivasculature therapy might also improve hypoxia/necrosis-related therapeutic approaches.

Antiangiogenic therapy inhibits human neuroblastoma growth

BACKGROUND

Angiogenesis plays a crucial role in the progression and metastasis of malignant solid tumors. In many types of cancer, including neuroblastoma, high tumor vascularity correlates with poor outcome. Recently, a number of angiogenic inhibitors have been identified that had antitumor activity in preclinical studies.

PROCEDURE

To investigate the effect of the antiangiogenic agent TNP-470 on neuroblastoma tumor growth, we treated nude mice with TNP-470 after they were inoculated subcutaneously with 5 x 10(6) cells from the MYCN-amplified, human neuroblastoma cell line NBL-W-N.

RESULTS

TNP-470 did not significantly affect tumor growth when it was administered to mice with large tumors (>600 mm3). However, when TNP-470 was administered in the setting of microscopic disease 12 hr following tumor cell inoculation, treated mice had a significantly improved tumor-free survival at 12 weeks (P < 0.001), and overall survival at 45 weeks (P < 0.001), compared to control animals.

CONCLUSIONS

Our studies suggest that TNP-470 treatment may be most effective if it is administered in the setting of microscopic disease. We speculate that TNP-470 may inhibit neuroblastoma growth in children if treatment is initiated following intensive multimodality therapy, when residual disease is minimal.

Active drug targeting with immunoconjugates to choroidal neovascularization

PURPOSE

Active drug targeting with monoclonal antibody to neovascular vessels may be a potential treatment for choroidal neovascularization (CNV) in age-related macular degeneration (AMD). Endoglin (CD105) is a proliferating endothelial cell marker with excellent potential for targeting. The goals of this study were to investigate the expression of CD105 in CNV membranes surgically excised from patients with AMD and CNV lesions induced by intense laser photocoagulation in a cynomolgus monkey and to evaluate the in vitro effect of immunoconjugates on endothelial cells.

METHODS

CNV membranes were surgically excised from 10 patients with AMD. Experimental CNV was induced by intense laser photocoagulation in a cynomolgus monkey. Immunolocalization of CD105 on frozen sections of CNV lesions was studied by immunohistochemical evaluation. Anti-von Willebrand's factor antibody was used as an endothelial cell marker. The cytotoxic effect of immunoconjugates of anti-CD105 monoclonal antibody and dextran binding mitomycin C on human umbilical vein endothelial cells (HUVECs) was evaluated in vitro.

RESULTS

Endothelial cells demonstrated strong immunoreactivity of CD105 in all surgically excised CNV membranes. In the monkey eye, CD105-positive cells were detected only in CNV lesions but not in normal chorioretinal tissues. Immunoconjugates with anti-CD105 monoclonal antibody showed a specific inhibitory effect on proliferating HU-VECs.

CONCLUSIONS

These results suggest that anti-CD105 monoclonal antibody-mediated drug targeting has a potential to treat CNV in AMD.

The antiangiogenic agent TNP-470 requires p53 and p21CIP/WAF for endothelial cell growth arrest

Targeting the endothelial cell cycle as an antiangiogenic strategy has been difficult given the ubiquitous expression of critical cell cycle regulators. Here, we show that the antiangiogenic drug TNP-470 displays striking cell-type specificity insofar as it induces the expression of p21(CIP/WAF), a cyclin-dependent kinase inhibitor, in endothelial cells but not in embryonic or adult fibroblasts. Moreover, primary endothelial cells isolated from p53(-/-) and p21(CIP/WAF-/-) mice are resistant to the cytostatic activity of TNP-470. We also demonstrate that p21(CIP/WAF-/-) mice are resistant to the antiangiogenic activity of TNP-470 in the basic fibroblast growth factor corneal micropocket angiogenesis assay. We conclude that TNP-470 induces p53 activation through a unique mechanism in endothelial cells leading to p21(CIP/WAF) expression and subsequent growth arrest.

Inhibition of hepatic stellate cell proliferation and activation by the semisynthetic analogue of fumagillin TNP-470 in rats

Proliferation and activation of hepatic stellate cells (HSCs) are critical steps for the development of postnecrotic fibrosis in the liver. The present study aimed to reveal the inhibitory effect of the semisynthetic analogue of fumagillin TNP-470 on these events for its possible use as an antifibrogenic agent. Rat models of carbon tetrachloride (CCl(4))- and dimethylnitrosamine-induced hepatic fibrosis were used for an in vivo study. In both models, the fibrotic area was considerably decreased by concurrent repetitive subcutaneous injections of 30 mg/kg body weight of TNP-470. In CCl(4)-induced fibrosis, factor VIII-related antigen-positive blood vessels, desmin-, or alpha-smooth muscle actin (alphaSMA)-positive mesenchymal cells, bromodeoxyuridine (BrdU)-positive mesenchymal cells also decreased in number by treatment with TNP-470. In in vitro experiments, a supplement of 1,000 ng/mL TNP-470 suppressed BrdU incorporation and cyclins D1, D2, and E expression by cultured HSCs in the absence and/or presence of platelet-derived growth factor (PDGF). Expression of HSC activation markers, i.e., alphaSMA and PDGF receptor beta, was also suppressed. The present results indicate that TNP-470 inhibits HSC proliferation by blocking the cell-cycle transition from G1 to S and HSC activation, and, as the consequence, prevents the progression of hepatic fibrosis, probably being coupled with its antiangiogenic effect.

Inhibition by an angiogenesis inhibitor, TNP-470, of the growth of a human hepatoblastoma heterotransplanted into nude mice

BACKGROUND/PURPOSE

The effect of TNP-470, an angiogenesis inhibitor, on the growth of a hepatoblastoma transplanted into nude mice was examined.

METHODS

A hepatoblastoma obtained from a 3-year-old girl was serially transplanted into nude mice subcutaneously, and the transplant tumors of the seventh and eighth generations were used for experiments. Expression of various markers in the tumors was examined immunohistochemically. TNP-470 was injected subcutaneously every other day into tumor-bearing mice from 3 weeks after tumor transplantation. The proliferation of tumor cells and endothelial cells was estimated by means of the bromodeoxyuridine labeling index.

RESULTS

The original hepatoblastoma showed the histology of the epithelial type, consisting of both the fetal and embryonal subtypes and was positively stained with anti-alpha-fetoprotein (AFP), anti-cytokeratin-19 and polyclonal anticarcinoembryonic antigen antibodies, and an antihuman hepatocyte antibody (hepatocyte paraffin 1). The transplant tumors consisted of solid nests of tumor cells with numerous vascular lakes of various sizes, and showed positive staining with all antibodies that reacted positively with the original hepatoblastoma. Injections of TNP-470 at the doses of 15 mg and 30 mg/kg body weight suppressed the tumor growth and the increase in the serum level of AFP dose dependently. Injections of TNP-470 also suppressed the proliferation of tumor cells and endothelial cells in the tumors.

CONCLUSIONS

Hepatoblastomas maintained in nude mice retained the immunohistochemical characteristics of the original hepatoblastoma, and TNP-470 suppressed the growth of hepatoblastomas transplanted into nude mice. TNP-470 may be worth investigating further as to its usefulness as a therapy for hepatoblastomas.

TNP-470 and recombinant human interferon-alpha2a inhibit angiogenesis synergistically

The hypothesis that the combination of two known antiangiogenic agents TNP-470 and interferon (IFN)-alpha exerts synergistic effects has been investigated in vitro and in vivo. In vitro, TNP-470 and recombinant human IFN-alpha2a (rhIFN-alpha2a) resulted in a dose-dependent inhibition of proliferation of human umbilical vein endothelial cells (HUVECs) and EA.hy926 endothelial cells. Compared with the two agents used singly at their lowest or ineffective doses, combined treatment with the same doses inhibited more intensely in the absence of cytotoxicity and displayed similar behaviour on cell chemotaxis and capillary morphogenesis on Matrigel. However, the secretion of matrix metalloproteinase 2 (MMP-2) and MMP-9 was not influenced by the two agents, either alone or in combination, even when they were applied at their lowest efficacious doses or at higher cytotoxic doses. Experiments in vivo with the chick embryo chorioallantoic membrane (CAM)-sponge assay revealed the same dose-dependent inhibition and synergy. As the basic fibroblast growth factor (bFGF)-induced angiogenesis in the CAM-sponge model was strongly inhibited by the combined treatment, TNP-470 and rhIFN-alpha2a would appear to exert antiangiogenesis synergistically, perhaps by interfering with the bFGF-mediated pathway.

TNP-470: an angiogenesis inhibitor in clinical development for cancer

TNP-470, an analogue of fumagillin, has been shown to inhibit angiogenesis in vitro and in vivo. In 1992, TNP-470 entered clinical development for cancer as an anti-angiogenic agent. It is currently in Phase I/II trials in Kaposi's sarcoma, renal cell carcinoma, brain cancer, breast cancer, cervical cancer and prostate cancer. In early clinical reports, TNP-470 is tolerated up to 177 mg/m(2) with neurotoxic effects (fatigue, vertigo, ataxia, and loss of concentration) being the principal dose limiting toxicity (DLT). Terminal half-life values are short and have shown intermittent and intrapatient variation (range: 0.05 - 1.07 h). Recently, mechanistic studies have identified cell cycle mediators and the protein methionine aminopeptidase-2 (MetAP-2) as molecular targets of TNP-470 and fumagillin. Animal studies confirm some toxic effects on normal angiogenic processes such as the female reproductive system and wound healing, which will require caution and close monitoring in the clinic. TNP-470 is one of the first anti-angiogenic compounds to enter clinical trials, making it a valuable prototype for future trials of angiogenesis inhibitors in oncology.