Inhibitors of angiogenesis enter phase III testing

Fucoidan from Fucus vesiculosus inhibits new blood vessel formation and breast tumor growth in vivo

Fucoidan is a marine-origin sulfated polysaccharide that can show anticancer activity, to which both pro- and anti-angiogenic responses have been reported. Due to this unpredictability, the angiogenic potential of an effective anticancer crude fucoidan (CF), at a concentration of 0.5 mg mL-1, was evaluated. Tube formation assays demonstrated that CF, either administered while endothelial cells seeding or after their adhesion, migration and organization, inhibited or disrupted the formation of tubular-like structures, respectively. Although CF did not significantly reduced vascular endothelial growth factor (VEGF) secretion, it significantly reduced the expression of platelet-derived growth factor (PDGF), compromising the blood vessels maturation. Two chicken embryo chorioallantoic membrane (CAM) assays were performed: one without tumor (CAM I) and the other with an onplanted tumor mass (CAM II); the CF injection reduced the number of blood of vessels and significantly decreased the tumor size, respectively. In vitro and in vivo results support the effectiveness of fucoidan as a natural antitumor therapeutic agent.

Tumor progression-dependent angiogenesis in gastric cancer and its potential application

Despite improvements in the early diagnosis, prognosis and therapeutic strategies for gastric cancer (GC), human GC remains one of the most frequently diagnosed malignant tumors in the world, and the survival rate of GC patients remains very poor. Thus, a suitable therapeutic strategy for GC is important for prolonging survival. Both tumor cells themselves and the tumor microenvironment play an important role in tumorigenesis, including angiogenesis, inflammation, immunosuppression and metastasis. Importantly, these cells contribute to gastric carcinogenesis by altering the angiogenic phenotype switch. The development, relapse and spreading of tumors depend on new vessels that provide the nutrition, growth factors and oxygen required for continuous tumor growth. Therefore, a state of tumor dormancy could be induced by blocking tumor-associated angiogenesis. Recently, several antiangiogenic agents have been identified, and their potential for the clinical management of GC has been tested. Here, we provide an up-to-date summary of angiogenesis and the angiogenic factors associated with tumor progression in GC. We also review antiangiogenic agents with a focus on the anti-vascular endothelial growth factor receptor (VEGFR)-mediated pathway for endothelial cell growth and their angiogenesis ability in GC. However, most antiangiogenic agents have reported no benefit to overall survival (OS) compared to chemotherapy alone in local or advanced GC. In phase III clinical trials, only ramucirumab (anti-VEGFR blocker) and apatinib (VEGFR-TKI blocker) have reported an improved median overall response rate and prolonged OS and progression-free survival outcomes as a 2nd-line agent combined with chemotherapy treatment in advanced GC. By providing insights into the molecular mechanisms of angiogenesis associated with tumor progression in GC, this review will hopefully aid the optimization of antiangiogenesis strategies for GC therapy in combination with chemotherapy and adjuvant treatment.

Angiogenesis and Cancer Control: From Concept to Therapeutic Trial

Background

There is extraordinary interest in developing angiosuppressive agents for cancer treatment. Several new agents appear promising for the treatment of a variety of human cancers. Current concepts and new agents in clinical trials are the focus of this article. In particular, the introduction of a new treatment for human brain tumors is presented in detail, using an antiangiogenic agent, penicillamine, and depletion of an obligatory cofactor of angiogenesis, copper.

Methods

The explosive increase in literature on antiangiogenesis is reviewed using computerized search, findings presented at the recent national cancer and angiogenesis meetings. A specific protocol, NABTT 97-04, “Penicillamine and Copper Reduction for Newly Diagnosed Glioblastoma,” is presented as an example of angiotherapeutic drug discovery.

Results

A number of promising molecular approaches are being introduced to suppress tumor angiogenesis. Major categories of angiogenesis antagonists include protease inhibitors, direct inhibitors of endothelial cell proliferation and migration, suppression of angiogenic growth factors, inhibition of endothelial-specific integrin/survival signaling, chelators of copper, and inhibitors with specific other mechanisms. The preliminary results of early trials offer a glimpse into how antiangiogenesis therapy will be integrated into future care of the patient with cancer.

Conclusions

Thirty-five antiangiogenesis therapies are currently being evaluated in clinical trials. As we learn more about the fundamental mechanisms of angiogenesis, eg, the role of copper in growth factor activation, effective methods of cancer control will be implemented.

Anticancer effects of fucoidan

Recently, there has been an increased interest in the pharmacologically active natural compounds isolated and used for remedies of various kinds of diseases, including cancer. The great deal of interest has been developed to isolate bioactive compounds from marine resources because of their numerous health beneficial effects. Among marine resources, marine algae are valuable sources of structurally diverse bioactive compounds. Fucoidan is a sulfated polysaccharide derived from brown seaweeds and has been used as an ingredient in some dietary supplement products. Fucoidan has various biological activities including antibacterial, antioxidant, anti-inflammatory, anticoagulant, and antitumor activities. So this chapter deals with anticancer effects of fucoidan.

Brown seaweed fucoidan: biological activity and apoptosis, growth signaling mechanism in cancer

Seaweeds, being abundant sources of bioactive components have much interest in recent times. The complex polysaccharides from the brown, red and green seaweeds possess broad spectrum therapeutic properties. The sulfated polysaccharides are routinely used in biomedical research and have known biological activities. Fucoidan, a fucose-rich polysaccharide extracted from brown seaweed has various biological functions including anticancer effects. Cellular damage induces growth arrest and tumor suppression by inducing apoptosis, the mechanism of cell death depends on the magnitude of DNA damage following exposure to anticancer agents. Apoptosis is mainly regulated by cell growth signaling molecules. Number of research studies evidenced that fucoidan shown to induce cytotoxicity of various cancer cells, induces apoptosis, and inhibits invasion, metastasis and angiogenesis of cancer cells. There are few articles discussing on fucoidan biological activity but no specific review on cancer and its signaling mechanism. Hence, this review discusses the brown seaweed fucoidan structure and some biological function and role in apoptosis, invasion, metastasis, angiogenesis and growth signal mechanism on cancer.

Tumor targeting of doxorubicin by anti-MT1-MMP antibody-modified PEG liposomes

Immunoliposomes are potent carriers for targeting of therapeutic drugs to specific cells. Membrane type-1 matrix metalloproteinase (MT1-MMP), which plays an important role in angiogenesis, is expressed on angiogenic endothelium cells as well as tumor cells. Then, the MT1-MMP might be useful as a target molecule for tumor and neovascularity. In the present study, we addressed a utility of antibodies against the MT1-MMP as a targeting ligand of liposomal anticancer drug. Fab' fragments of antibody against the MT1-MMP were modified at distal end of polyethylene glycol (PEG) of doxorubicin (DXR)-encapsulating liposomes, DXR-sterically stabilized immunoliposomes (DXR-SIL[anti-MT1-MMP(Fab')]). Modification with the antibody significantly enhanced cellular uptake of DXR-SIL[anti-MT1-MMP(Fab')] into the HT1080 cells, which highly express MT1-MMP, compared with the non-targeted liposomes (DXR-stealthliposomes (DXR-SL)), suggesting that MT1-MMP antibody (Fab') is a potent targeting ligand for the MT1-MMP expressed cells. In vivo systemic administration of DXR-SIL[anti-MT1-MMP(Fab')] into the tumor-bearing mice showed significant suppression of tumor growth compared to DXR-SL. This is presumably due to the active targeting of immunoliposomes for tumor and neovascularity. However, tumor accumulation of DXR-SIL[anti-MT1-MMP(Fab')] and DXR-SL were comparable, suggesting that both liposomal formulations accumulated in tumor via enhanced permeation and retention (EPR) effect, but not via targeting to the MT1-MMP expressed on both the endothelial and tumor cells. It appears that the enhanced antitumor activity of DXR-SIL[anti-MT1-MMP(Fab')] resulted from acceleration of cellular uptake of lioposomes owing to the incorporated antibody after extravasation from capillaries in tumor.

Identification and characterization of novel endogenous proteolytic forms of the human angiogenesis inhibitors restin and endostatin

Restin and endostatin are C-terminal fragments of the noncollagenous domains of collagen XV and collagen XVIII exhibiting high sequence homology. Both polypeptides are distinguished by strong anti-angiogenic activity in vivo restricting the growth of solid tumors and metastasis. They are therefore currently being tested in clinical trials as anti-cancer drugs. We present the identification of new endogenous variants of both angiogenesis inhibitors isolated from a human hemofiltrate peptide library. Using an immunological screening approach with time-resolved rare earth metal fluorometry, immunoreactive compounds were purified chromatographically and characterized by mass spectrometry. We discovered four novel proteolytic products of restin as well as four variants of endostatin. Two endostatin products were characterized as short internal fragments (R176-L215 and R176-S219) of the entire molecule containing the recently identified beta1 integrin receptor binding site, which plays a major role in endothelial cell migration and angiogenesis. Two additional forms contain mucin-type O-glycosylations. The O-glycosylated variants possess an oligosaccharide unit consisting of one N-acetylgalactosamine (GalNAc), one N-acetylneuraminic acid (NANA) and two galactose residues (Gal) occurring as sialo-(V117-S311-GalNAc-Gal2-NANA) and asialoglycopeptides (V117-S311-GalNAc-Gal2). The four restin variants (R(I)-R(IV)) were identified with identical C- but different N-termini and no posttranslational modification (R(I): P66-A254, R(II): P75-A254, R(III): Y81-A254 and R(IV): A89-A254). Following a differential peptide mass fingerprint approach by reflector mode MALDI-TOFMS, the disulfide patterns of these circulating restins were determined as Cys1-Cys4 and Cys2-Cys3. These endogenous circulating collagen fragments will help to understand the physiological processing of the therapeutic proteins.

The collagen type XVIII endostatin domain is co-localized with perlecan in basement membranes in vivo

The C-terminal globular endostatin domain of collagen type XVIII is anti-angiogenic in a variety of experimental tumor models, and clinical trials to test it as an anti-tumor agent are already under way. In contrast, many of its cell biological properties are still unknown. We systematically localized the mRNA of collagen type XVIII with the help of in situ hybridization (ISH) and detected it in epithelial and mesenchymal cells of almost all organ systems throughout mouse development. Light and electron microscopic immunohistochemistry (IHC) revealed that the endostatin domain is a widespread component of almost all epithelial basement membranes in all major developing organs, and in all basement membranes of capillaries and blood vessels. Furthermore, quantitative immunogold double labeling demonstrated a co-localization of 50% of the detected endostatin domain together with perlecan in basement membranes in vivo. We conclude that the endostatin domain of collagen type XVIII plays a role, even in early stages of mouse development, other than regulating angiogenesis. In the adult, the endostatin domain could well be involved in connecting collagen type XVIII to the basement membrane scaffolds. At least in part, perlecan appears to be an adaptor molecule for the endostatin domain in basement membranes in vivo.

Oversulfation of fucoidan enhances its anti-angiogenic and antitumor activities

Fucoidan, a sulfated polysaccharide extracted from brown seaweed, has anticoagulant and antithrombotic activities. Unlike heparin, it shows an inhibitory action on the progression and metastasis of malignant tumors, although the precise mechanisms have not been elucidated. We have demonstrated previously that fucoidan can inhibit tube formation following migration of human umbilical vein endothelial cells (HUVEC) and that its chemical oversulfation enhances the inhibitory potency. In this study, we tested the hypothesis that fucoidan may suppress tumor growth by inhibiting tumor-induced angiogenesis. Both natural and oversulfated fucoidans (NF and OSF) significantly suppressed the mitogenic and chemotactic actions of vascular endothelial growth factor 165 (VEGF(165)) on HUVEC by preventing the binding of VEGF(165) to its cell surface receptor. The suppressive effect of OSF was more potent than that of NF, suggesting an important role for the numbers of sulfate groups in the fucoidan molecule. Consistent with its inhibitory actions on VEGF(165), OSF clearly suppressed the neovascularization induced by Sarcoma 180 cells that had been implanted in mice. The inhibitory action of fucoidan was also observed in the growth of Lewis lung carcinoma and B16 melanoma in mice. These results indicate that the antitumor action of fucoidan is due, at least in part, to its anti-angiogenic potency and that increasing the number of sulfate groups in the fucoidan molecule contributes to the effectiveness of its anti-angiogenic and antitumor activities.

Angiogenesis in hematologic malignancies and its clinical implications

Angiogenesis is defined as a neoformation of blood vessels of capillary origin. Hematopoiesis is closely linked with angiogenesis, for they share a common ancestor, the hemangioblast. Although it is well established that growth in solid tumors is dependent on angiogenesis, its role in hematologic malignancies has not yet been clarified. In this review, the direct evidence, ie, increased microvessel density, and the indirect evidence, ie, elevated level of angiogenic factors or overexpression of messenger RNA or protein of angiogenic factors, for and against the role of angiogenesis in the development and progression of hematologic malignancies are presented.

Radiotherapy and antiangiogenic TM in lung cancer

Tetrathiomolybdate (TM) is a potent nontoxic orally delivered copper complexing agent under development for the last several years for the treatment of Wilson's disease. It has been shown to block angiogenesis in primary and metastatic tumors. Therefore, the combination of cytotoxic radiotherapy (RT) and antiangiogenic TM could target both the existing tumor and the tumor microvasculature in a comprehensive strategy. Using a Lewis lung high metastatic (LLHM) carcinoma mouse tumor model, we demonstrate that the combination of TM and RT is more effective than either used as monotherapy. We also show that their therapeutic effects are additive, with no additional toxicity. We show that TM has no significant cytotoxicity in vitro against LLHM tumor cells, further supporting the antiangiogenic mechanism for its action.

Novel approaches to the treatment of non-small cell lung cancer

Prognosis of non-small cell lung carcinomas (NSCLC) remains poor, especially in advanced disease. The introduction of new cytotoxic agents in the past decade did only attain minor improvements in survival. It is rather clear that chemotherapy may have reached a plateau, and that it will be difficult to obtain better results in advanced NSCLC by chemotherapy alone. Novel treatment modalities are urgently needed in advanced NSCLC. Backed-up by advances in the understanding of tumor cell biology, a new generation of anticancer agents specifically directed at targets such as tyrosine kinases, farnesyl transferase, angiogenesis factors, matrixmetalloproteinases and oncogenes has been developed in recent years. In this review, we give a brief summary of the state-of-the-art treatment of NSCLC, highlighting its limitations. Novel systemic approaches are then discussed in detail with focus on their mechanistic rationale, stage of clinical development and possible drawbacks. Finally, perspectives of future applications and impact on the treatment of NSCLC are also discussed.

Angiogenesis in breast cancer: the role of transforming growth factor beta and CD105

The progression of breast cancer depends on the establishment of a neovasculature, by a process called angiogenesis. Angiogenesis is an invasive cellular event that requires the co-ordination of numerous molecules including growth factors and their receptors, extracellular proteins, adhesion molecules, and proteolytic enzymes. TGFbeta has emerged to be a major modulator of angiogenesis by regulating endothelial cell proliferation, migration, extracellular matrix (ECM) metabolism, and the expression of adhesion molecules. It is a potent growth inhibitor of normal mammary epithelial cells and a number of breast cancer cell lines. It seems that TGFbeta exerts pleiotropic effects in the oncogenesis of breast cancers in a contextual manner, i.e., it suppresses tumourigenesis at an early stage by direct inhibition of angiogenesis and tumour cell growth. However, over-production of TGFbeta by an advanced tumour may accelerate disease progression through indirect stimulation of angiogenesis and immune suppression. The cell membrane antigen CD105 (endoglin) binds TGFbeta1 and TGFbeta3 and is preferentially expressed in angiogenic vascular endothelial cells. The reduction of CD105 levels in HUVEC leads to in vitro angiogenesis inhibition and massive cell mortality in the presence of TGFbeta1. CD105 null mice die in utero with impaired vasculature, indicating the pivotal role of CD105 in vascular development. The administration of an immunotoxin-conjugate, mab to CD105, induces long-term and complete regression of breast cancer growth in SCID mice. Therefore, CD105 is a promising vascular target for antiangiogenic therapy.

The role of gemcitabine alone and in combination in the treatment of pancreatic cancer

Pancreatic cancer, one of the most frequently reported gastrointestinal tumors, has a 5-year survival of less than 5%. Despite representing only 2-3% of the total cancer incidence, it is the fifth leading cause of cancer death. This is because it is commonly only diagnosed at an advanced stage. Until recently the traditional therapy for patients with advanced disease was palliative 5-fluorouracil (5-FU)-based chemotherapy. However, the novel antinucleoside gemcitabine (Gemzar) has demonstrated a survival benefit over 5-FU, and an improvement in disease-related symptoms and quality of life in patients with advanced disease. This review presents an overview of the clinical studies of gemcitabine, either alone or in combination, with other chemotherapeutic agents and/or radiation therapy, in the treatment of these patients. A comparison of these studies is made with those using alternative treatment regimens. The data suggest that gemcitabine in combination with biomodulated 5-FU should be considered the standard palliative treatment to which other new drug combinations or combined modality chemoradiation regimens should be compared.

New paradigms for the treatment of cancer: the role of anti-angiogenesis agents

Angiogenesis, the sprouting of new blood vessels, plays a role in diverse disease states including cancer, diabetic retinopathy, age-related macular degeneration, rheumatoid arthritis, psoriasis, atherosclerosis, and restenosis. With regard to cancer, the clinical association of tumor vascularity with tumor aggressiveness has been clearly demonstrated in numerous tumor types. The observation of increased microvessel density in tumors not only serves as an independent prognostic indicator, but also suggests that anti-angiogenic therapy may be an important component of treatment regimens for cancer patients. The complexity of the angiogenic process, which involves both positive and negative regulators, provides a number of targets for therapy. Many positive regulators, including growth factor receptors, matrix metalloproteinases, and integrins, have been correlated with increased vascularity of tumors and poor prognosis for patient survival. Thus, these serve as ideal targets for anti-angiogenesis therapy. Many inhibitors of these targets are currently undergoing clinical evaluation as potential anti-cancer agents. In this article, we discuss the role of positive regulators in angiogenesis and tumor growth and describe the anti-angiogenic agents under development.

Anti-angiogenesis therapy:concepts and importance of dosing schedules in clinical trials

The biological control of angiogenesis is critical to the clinical control of cancer. Understanding the mechanism of formation and regulation of new blood vessel development would open a new avenue for cancer treatment. Intense research effort has revealed a variety of factors which initiate, control and terminate the multi-stage process of angiogenesis, as well as target structures which interfere with this process. Protease inhibitors, inhibitors of the endothelial cell proliferation, suppressors of angiogenic growth factors, copper chelators, and other compounds interfering with the process of angiogenesis were screened for inhibition of tumor angiogenesis and some of them are in clinical trials. Very recently, a new term, 'metronomic dosing regimen' has been introduced, which implicates the use of the old cytostatic anticancer agents as anti-angiogenic agents. Results from recent studies will be discussed briefly and the prospects of inhibition of tumor angiogenesis as a new treatment modality will be outlined. Copyright 2000 Harcourt Publishers Ltd.

Effect of angiostatin on liver metastasis of pancreatic cancer in hamsters

The liver is the most common site of metastasis in pancreatic cancer, and there are no promising strategies to treat it. Angiostatin, a kringle-containing fragment of plasminogen, is a potent inhibitor of angiogenesis. The effect of angiostatin on liver metastasis in pancreatic cancer was investigated by using our established hamster model of liver metastasis. Pancreatic cancer cells (PGHAM-1, 1 x 10(6)) derived from N-nitrosobis(2-oxopropyl)amine (BOP)-induced pancreatic tumor in Syrian golden hamsters were transplanted into the spleen of female hamsters, and the animals were subcutaneously injected with angiostatin and saline. Subsequently, the macroscopic appearance of liver surface metastases was evaluated. In addition, histological sections of the liver metastases were analyzed for neovascularization, proliferation, and apoptosis on the basis of von Willebrand factor, argyrophilic nucleolar organizer region (Ag-NOR), and TdT-mediated dUTP-biotin nick end labeling (TUNEL) staining, respectively. The results showed significant tumor growth retardation and inhibition of angiogenesis in metastatic liver tumors in response to treatment with angiostatin. Moreover, the metastases remained in a nearly dormant state due to a balance between apoptosis and proliferation of the tumor, with no detectable side effects. This is the first experimental trial of angiostatin on pancreatic cancer and liver metastasis. The results suggest that angiostatin therapy could be effective against liver metastases of pancreatic cancer.

MMP-1 is a prognostic marker for hematogenous metastasis of colorectal cancer

BACKGROUND

Degradation of basement membrane and extracellular matrix by matrix metalloproteinases (MMPs) is believed to be an essential step in the complicated process of hematogenous metastasis. MMP-1 is a member of collagenases, a family of MMPs that degrades collagens type I, II, and III, main components of the interstitial stroma. The purpose of this study was to investigate the expression of MMP-1 in colorectal cancer and its correlation with hematogenous metastasis. Patients and Methods. We examined 133 cases of colorectal cancer (Dukes A: 72; Dukes B: 26; Dukes C: 23; Dukes D: 12). Sections were cut from formalin-fixed, paraffin-embedded samples containing the deepest site of cancer invasion and stained immunohistochemically with a monoclonal antibody to MMP-1. According to the area of the tumor that was stained, patients were divided into high- and low-MMP-1 expression groups.

RESULTS

MMP-1 expression was observed in the cytoplasm of cancer cells, some stromal cells, and a few normal epithelial cells of colonic mucosa. High MMP-1 expression was found in 47 (35.3%) cases and low in 86 (64.7%). Hematogenous metastasis was identified in 14 (29.8%) of high-MMP-1 groups and 12 (13.9%) of low-MMP-1 groups. MMP-1 expression significantly correlated with hematogenous metastasis of colorectal cancer, but no correlation was found between MMP-1 expression and the other clinicopathological features investigated.

CONCLUSIONS

MMP-1 expression may be a novel marker for hematogenous metastasis of colorectal cancer, and its inhibition may be a strategy for prevention of metastasis.

Tumour micrometastases: the influence of angiogenesis

INTRODUCTION

Many cancer patients have undetected micrometastatic disease at first presentation which ultimately progresses. Angiogenesis-the development of an independent blood supply-is a key event in the growth of metastases. Improved understanding of the influence of angiogenesis on micrometastatic growth may lead to new therapeutic intervention.

METHODS

This study examines current concepts of the significance of micrometastases and the role of angiogenesis in their development and destruction. A comprehensive review of the literature on micrometastasis and angiogenesis was performed using the Medline database between 1966 and 1999.

CONCLUSIONS

Advances in technology have improved our ability to diagnose metastatic disease, but micrometastases in loco-regional lymph nodes and at distant sites can only be detected by sophisticated histological techniques. While the significance of micrometastases remains controversial, there is increasing evidence that micrometastatic status provides useful prognostic information and should be part of standard staging techniques. Anti-angiogenic therapy has the potential to favourably influence management of certain cancers by manipulating a number of key events in the metastatic process.

Tumor angiogenesis: past, present and the near future

The concept of treating solid tumors by inhibiting tumor angiogenesis was first articulated almost 30 years ago. For the next 10 years it attracted little scientific interest. This situation changed, relatively slowly, over the succeeding decade with the discovery of the first pro-angiogenic molecules such as basic fibroblast growth factor and vascular endothelial growth factor (VEGF), and the development of methods of successfully growing vascular endothelial cells in culture as well as in vivo assays of angiogenesis. However, the 1990s have witnessed a striking change in both attitude and interest in tumor angiogenesis and anti-angiogenic drug development, to the point where a remarkably diverse group of over 24 such drugs is currently undergoing evaluation in phase I, II or III clinical trials. In this review I will discuss the many reasons for this. These features, together with other recent discoveries have created intense interest in initiating and expanding anti-angiogenic drug discovery programs in both academia and industry, and the testing of such newly developed drugs, either alone, or in various combinations with conventional cytotoxic therapeutics. However, significant problems remain in the clinical application of angiogenesis inhibitors such as the need for surrogate markers to monitor the effects of such drugs when they do not cause tumor regressions, and the design of clinical trials. Also of concern is that the expected need to use anti-angiogenic drugs chronically will lead to delayed toxic side effects in humans, which do not appear in rodents, especially in short-term studies.

Dienogest, a synthetic steroid, suppresses both embryonic and tumor-cell-induced angiogenesis

Orally administered dienogest (17alpha-cyanomethyl-17beta-hydroxy-estra-4,9-diene-3-one) is efficacious against human hormone-dependent cancer xenografts in severely immunodeficient mice and in rats with experimental endometriosis, but its mechanisms of action remain unclear. We assessed the effect of dienogest on angiogenesis, because these two diseases that are sensitive to dienogest are known to be angiogenesis-dependent. Topical dienogest treatment dose-dependently inhibited embryonic angiogenesis, the ID(50) value being 6.4 nmol/egg. Oral administration of dienogest (1 mg kg(-1) day(-1)) for 5 consecutive days significantly suppressed angiogenesis induced by S-180 mouse tumor cells in the mouse dorsal air sac assay. In vitro experiments showed that dienogest at concentrations up to 10 microM had little or no effect on the proliferation of plasminogen activator activity or formation of tube-like structures by microvascular endothelial cells. These results suggest that dienogest is a new, orally active antagonist of angiogenesis, and that its anti-angiogenic action may be involved in its therapeutic effects on cancer xenografts and endometriosis that we observed previously.

Roxithromycin and clarithromycin, 14-membered ring macrolides, potentiate the antitumor activity of cytotoxic agents against mouse B16 melanoma cells

We previously reported antiangiogenic activity of roxithromycin and clarithromycin, 14-membered ring macrolide antibiotics. In the present study, we examined the antitumor effects of roxithromycin and clarithromycin, alone and in combination with several cytotoxic drugs, on mouse B16BL6 melanoma cells in vivo and in vitro. Both roxithromycin and clarithromycin potentiated the inhibition of tumor growth induced by cyclophosphamide, cis-diamminedichloroplatinum(II), Adriamycin and vindesine in vivo. However, neither roxithromycin nor clarithromycin, altered the cytotoxicity of 4-hydroperoxycyclophosphamide, cis-diamminedichloroplatinum(II), Adriamycin or vindesine in an in vitro cell proliferation assay. These results suggest that the antiangiogenic activity of roxithromycin and clarithromycin may provide beneficial effects in combination with cytotoxic therapies against solid tumors.

Novel anticancer drug discovery

There is at present, much optimism about the possibility of finding selective anticancer drugs that will eliminate the cytotoxic side effects associated with conventional cancer chemotherapy. This hope is based on uncovering many novel molecular targets that are 'cancer-specific', which will allow the targeting of cancer cells while normal cells are spared. Thus far, encouraging results have been obtained with several of these novel agents at the preclinical level, and clinical trials have begun. These targets are involved at one level or more in tumor biology, including tumor cell proliferation, angiogenesis and metastasis. Novel targets for which advances are being made include the following: growth factor receptor tyrosine kinases such as the epidermal growth factor receptor and HER-2/neu (proliferation); the vascular endothelial growth factor receptor and the basic fibroblast growth factor receptor (angiogenesis); the oncogenic GTP-binding protein Ras (especially agents targeting Ras farnesylation, farnesyltransferase inhibitors) (proliferation); protein kinase C (proliferation and drug resistance); cyclin-dependent kinases (proliferation); and matrix metalloproteinases and angiogenin (angiogenesis and metastasis). Less explored, but potentially useful targets include the receptor tyrosine kinase platelet-derived growth factor receptor, mitogen-activated protein kinase cascade oncogenes such as Raf-1 and mitogen-activated protein kinase kinase, cell adhesion molecules such as integrins, anti-apoptosis proteins such as Bcl-2, MDM2 and survivin, and the cell life-span target telomerase.

Angiogenic factors in laryngeal carcinomas: do they have prognostic relevance?

Angiogenesis is a cascade-like mechanism essential for tumour growth and metastasis. Recently developed inhibitors of angiogenesis have already proven their benefit in anticancer treatment. Therefore the existence of angiogenic molecules in individual tumours is of major interest. The factors most frequently contributing to angiogenesis are basic fibroblast growth factor (bFGF), vascular endothelial growth factor (VEGF) and some matrix metalloproteinases (MMPs). In order to evaluate the prognostic significance of these molecules we investigated the distribution pattern of VEGF, bFGF, MMP-2 and MMP-9 in 41 laryngeal carcinomas using immunohistochemical methods. The results were correlated with clinicopathological parameters, i.e. T and N stage, histological grading, freedom from disease, overall survival and microvessel density (MVD). Only VEGF revealed a correlation with MVD (p = 0.01) and a weak association with histological grading (p = 0.06). Even though there is controversy about published data on the prognostic relevance of angiogenic factors, our results suggest that the factors examined in this study are not suitable for prognosis in larynx cancer patients.

Redundancy of autocrine loops in human osteosarcoma cells

With the aim of identifying innovative therapeutic strategies for osteosarcoma patients who are refractory to conventional chemotherapy, we analyzed the in vitro effects of the blockage of autocrine circuits. Since the insulin-like growth factor-I receptor (IGF-IR)-mediated loop is relevant to the growth of osteosarcoma, we analyzed the activity of the IGF-IR-blocking antibody alphaIR3 in both sensitive and multidrug-resistant osteosarcoma cell lines. Only limited effects, however, were observed, suggesting the simultaneous existence of other autocrine circuits. Indeed, in a representative panel of 12 human osteosarcoma cell lines, in addition to the IGF-IR-mediated circuit, we demonstrated also a loop mediated by epidermal growth factor receptor as well as the presence of nerve growth factor, low-affinity nerve growth factor receptor as well as tyrosine receptor kinase A in the great majority of osteosarcomas. Therapies based on the inhibition of single circuits may have only limited effects in osteosarcoma, whereas the use of suramin, a drug which, besides other activities, non-selectively interferes with the binding of growth factors to their receptors, appears as a promising alternative, in both sensitive and drug-resistant osteosarcoma cells.