Medroxyprogesterone acetate, an anti-cancer and anti-angiogenic steroid, inhibits the plasminogen activator in bovine endothelial cells

Development of a mouse model for testing therapeutic agents: the anticancer effect of dienogest on endometrial neoplasms

OBJECTIVE

As the number of younger women with endometrial carcinoma has increased, fertility-sparing treatments have received more attention. Although there have been several reports on conservative treatments with progestins for endometrial carcinoma, only medroxyprogesterone acetate (MPA) is available in Japan. Dienogest has been developed as a fourth-generation progestin for treating endometriosis. Because of its high progesterone activity, its antitumor activity has attracted attention. In this study, we investigated the anticancer effect of dienogest on endometrial neoplasms using mouse model of endometrial carcinoma.

METHODS/MATERIALS

Pten(loxP/loxP) mice were injected with MPA or dienogest subcutaneously to evaluate the anticancer effect against endometrial neoplasms that developed in the mice. One week after injections, histopathological analyzes were performed.

RESULTS

Endometrial neoplasms were found in one of the eight (12.5%) mice from each group treated with either dienogest or MPA. In contrast, they were found in seven of eight (87.5%) mice not treated with progestins. Each progestin treatment showed anticancer activity against endometrial neoplasms that developed in the mice compared to those without treatment.

CONCLUSIONS

Dienogest and MPA showed potent anticancer activity against endometrial neoplasms in our mouse model. The present study demonstrated that dienogest might be a useful therapeutic agent for human endometrial neoplasms.

Nobiletin, a citrus polymethoxyflavonoid, suppresses multiple angiogenesis-related endothelial cell functions and angiogenesis in vivo

Nobiletin is a citrus polymethoxyflavonoid that suppresses tumor growth and metastasis, both of which depend on angiogenesis. We recently identified nobiletin as a cell differentiation modulator. Because cell differentiation is a critical event in angiogenesis, it might be possible that nobiletin could exhibit antiangiogenic activity, resulting in suppression of these tumor malignant properties. To verify this possibility, we examined the antiangiogenic effects of nobiletin in vitro and in vivo. Nobiletin had concentration-dependent inhibitory effects on multiple functions of angiogenesis-related endothelial cells (EC); it suppressed the proliferation, migration and tube formation on matrigel of human umbilical vein EC (HUVEC) stimulated with endothelial cell growth supplement (ECGS), a mixture of acidic and basic fibroblast growth factors (FGFs). Gelatin zymography and northern blotting revealed that nobiletin suppressed pro-matrix metalloproteinase-2 (proMMP-2) production and MMP-2 mRNA expression in ECGS-stimulated HUVEC. Nobiletin also downregulated cell-associated plasminogen activator (PA) activity and urokinase-type PA mRNA expression. Furthermore, nobiletin inhibited angiogenic differentiation induced by vascular endothelial growth factor and FGF, an in vitro angiogenesis model. This inhibition was accompanied by downregulation of angiogenesis-related signaling molecules, such as extracellular signal-regulated kinase 1/2 and c-Jun N-terminal kinase, and transcriptional factors (c-Jun and signal transducer and activator of transcription 3), and activation of the caspase pathway. In a chick embryo chorioallantoic membrane assay, nobiletin showed an antiangiogenic activity, the ID(50) value being 10μg (24.9nmol) per egg. These results indicate that nobiletin is a novel antiangiogenic compound that exhibits its activity through combined inhibition of multiple angiogenic EC functions.

POSTERIOR JUXTASCLERAL INJECTION OF ANECORTAVE ACETATE

PURPOSE

To confirm juxtascleral delivery of anecortave acetate in rabbit eyes by ocular imaging techniques and to determine drug localization and distribution as a function of time after injection.

METHODS

Four female New Zealand white rabbits (weight, 2.5-3.0 kg) received a single juxtascleral posterior sub-Tenon capsule injection of 0.5 mL or 1 mL of 30 mg/mL anecortave acetate. Rabbit eyes were imaged with ultrasonography and magnetic resonance imaging (MRI) before injection, immediately after injection, and at 2 hours, 1 week, and 4 weeks after injection. Rabbit eyes were also imaged with b-mode ultrasonography during the juxtascleral injections.

RESULTS

Ultrasonography and MRI demonstrated that juxtascleral posterior sub-Tenon capsule injection of anecortave acetate effectively delivered the drug in direct apposition to the posterior pole of the rabbit eye. The drug remained in the juxtascleral site for at least 5 weeks. The drug was visualized clearly by MRI immediately after injection, decreasing in intensity thereafter. Cannula insertion and the drug delivery process were clearly visualized by real-time ultrasound analysis. Immediately after drug injection, ultrasonography indirectly localized anecortave acetate localization as an echolucent zone posterior to the scleral surface. At the later time points, however, the juxtascleral location of the drug was verified with ultrasonography as a relatively echogenic focus in the same location.

CONCLUSIONS

Juxtascleral administration of anecortave acetate via a posterior sub-Tenon capsule approach effectively delivered the drug to the desired position in direct apposition to the globe posteriorly. MRI and ultrasonography both demonstrated that anecortave acetate remained localized to this location for at least 5 weeks after initial injection.

Suppression of Laser-Induced Choroidal Neovascularization by Subconjunctival Injection of 9.ALPHA.-Fluoromedroxyprogesterone Acetate (FMPA), an Anti-angiogenic Agent, in Rats

9alpha-Fluoromedroxyprogesterone acetate (FMPA) is a synthetic analog of medroxyprogesterone acetate (MPA). FMPA exhibited more potent anti-tumor and anti-angiogenic activities in some assay systems than the parent agent, MPA. Exudative age-related macular degeneration (AMD) is characterized by choroidal neovascularization (CNV). Anecortave acetate, an angiostatic steroid, is clinically efficacious in patients with exudative AMD. Betamethasone is an anti-angiogenic steroid. Therefore, we examined the effects of FMPA, anecortave acetate and betamethasone on laser-induced CNV in rats. Anecortave acetate and betamethasone were included as positive controls. Crypton laser was applied to the fundus in Brown Norway rats. Laser photocoagulations were performed in each eye between the major retinal vessels of the superior retina. Subconjunctival injection of FMPA, anecortave acetate or betamethasone was performed once just after the photocoagulation (on day 0). The incidence of CNV formation was evaluated by fluorescein angiography (FAG) on day 14. On the next day, examination of the retinal function was performed by electro retinogram (ERG). Subconjunctival injection of FMPA at doses of 300, 1000 and 3000 microg/eye dose-dependently inhibited the incidence of CNV formation. Significant differences were observed at doses of 1000 and 3000 microg/eye of FMPA as compared with the control group. Anecortave acetate and betamethasone significantly inhibited the incidence of CNV formation. FMPA at the doses used in this study did not affect the retinal function in rats, as determined by ERG. FMPA appeared to be effective in a rat model of CNV, so it was demonstrated that FMPA might be useful in the treatment of AMD.

The use of subretinal triamcinolone acetonide in the management of neovascular age-related macular degeneration: a pilot study

BACKGROUND

We conducted this study to investigate the toxicity and efficacy of pars plana vitrectomy combined with a single dose of sub-retinally administered triamcinolone acetonide (4 mg) in patients with subfoveal choroidal neovascular membranes secondary to age-related macular degeneration (AMD).

METHODS

The important eligibility criteria included eyes with recent and progressive onset of decreased vision (<or= 20/400) secondary to active subfoveal choroidal neovascularization secondary to AMD demonstrable on fluorescein angiography, in which subretinal hemorrhage accounted for < 25% of the area of the choroidal neovascular complex. Eligible patients were offered vitrectomy surgery combined with subretinal injection of 0.1 mL of triamcinolone acetonide (40 mg/mL) followed by air-fluid exchange. Two eyes of 2 patients were enrolled and followed for 28 and 35 months with regular and serial complete ophthalmologic examinations, fluorescein and indocyanine green videoangiography, and multifocal electro-retinography. The primary outcome measures were best-corrected visual acuity, changes in the fluorescein angiographic area and in the greatest linear dimension of leakage of the choroidal neovascular complex, and changes in amplitude and latency of the multifocal electroretinogram (ERG).

RESULTS

Patient 1 sustained a limited subretinal hemorrhage intraoperatively that cleared spontaneously over approximately 3 months, as well as a rise in intraocular pressure that required the use of 2 topical medications to control. Patient 2 demonstrated progression of his nuclear sclerosis and posterior subcapsular lens changes over the 35 months of follow-up. Best-corrected visual acuity improved from 20/400 to 20/200 in patient 1 and improved from counting fingers to 20/320 in patient 2. For patient 1, the area of the neovascular complex increased from 4.5 mm2 at baseline to 7.2 mm2 at the 6-month follow-up; for patient 2, this increase was from 6.2 mm2 to 8.4 mm2. Over the same interval, the greatest linear dimension increased from 3.8 mm to 4.8 mm for patient 1 and from 4.1 mm to 4.8 mm for patient 2. With respect to the multifocal ERG, the response density increased in the first 4 months for patient 1 and declined marginally thereafter. For patient 2, the electro-retinal response density function was stabilized for a 5-month period but declined and stabilized thereafter.

INTERPRETATION

Our results from this pilot study suggest that vitrectomy combined with subretinal injections of 0.1 mL of triamcinolone acetonide (40 mg/mL) and air-fluid exchange is easily accomplished. Although some complications were encountered, these did not appear to be prohibitive. A salutary effect was clearly demonstrated, not unlike the course seen with photodynamic therapy. Further study, perhaps in combination with other antiangiogenic agents, is warranted.

AL-3789: a novel ophthalmic angiostatic steroid

Ocular neovascular diseases are a leading cause of blindness in the world. Research is beginning to unravel the complex mechanisms involved in the pathogenesis of ocular neovascular diseases, but currently there are very few methods for the effective treatment of these blinding disorders. AL-3789 (Alcon Laboratories) is an angiostatic steroid which shows significant activity in inhibiting new blood vessel formation in a wide variety of models of neovascularisation, including neovascularisation in ocular tissues. This angiostatic steroid has broad angiostatic activity and is effective in a number of different animal species and tissues, regardless of the angiogenic stimulus. AL-3789 is devoid of conventional steroid hormone activity and does not appear to have any other pharmacological side-effects at the doses and routes of administration tested. In preclinical safety studies, AL-3789 has no apparent ocular or systemic toxicity when dosed chronically by topical ocular, or by systemic administration and therefore it appears to be a relatively safe compound.

Effects of rhizoxin, a microbial angiogenesis inhibitor, on angiogenic endothelial cell functions

Our previous study revealed that rhizoxin ([1S-[1R*,3R*,5S*,8R*(1R*,2S*,3E,5E,7E),10R*,11S*,13S*,14E,16S*,17S*]]-10-hydroxy-8-[2-methoxy-1,3,7-trimethyl-8-(2-methyl-4-oxazolyl)-3,5,7-octatrienyl]-11,16-dimethyl-4,7,12,18-tetraoxatetracyclo[15.3.1.03,5.011,13]heneicos-14-ene-6,19-dione) has a potent inhibitory effect on in vivo angiogenesis. However, little is known regarding the mechanism by which rhizoxin exhibits antiangiogenic activity. In this study, we examined its effects on the functions of endothelial cells associated with neovascular formation in vivo, using cultured vascular endothelial cells. Rhizoxin concentration-dependently inhibited the proliferation of bovine carotid artery endothelial cells, human umbilical vein endothelial cells and human dermal microvascular endothelial cells, the IC(50) values being 7, 5 and 0.4 nM, respectively. In addition, it reduced the extracellular plasminogen activator level in bovine vascular endothelial cells in the low nM range, and suppressed the migration of human dermal microvascular endothelial cells in the pM range. Furthermore, it blocked the tubular morphogenesis of human umbilical vein endothelial cells and human dermal microvascular endothelial cells on Matrigel in a concentration-dependent manner; the IC(50) values being 40 and 130 pM, respectively. These results suggest that rhizoxin exhibits antiangiogenic activity through the combined inhibition of some functions of endothelial cells responsible for induction of in vivo angiogenesis.

Local anti-angiogenic brain tumor therapies

The critical role of angiogenesis in the growth of solid tumors, including neoplasms of the central nervous system, has provided the impetus for research leading to the discovery of inhibitors of tumor neovascularization. The therapeutic potential of systemically administered antiangiogenic drugs for brain tumors, however, is limited by a variety of anatomic and physiologic barriers to drug delivery. Implantable controlled-release polymers for local drug administration directly into the tumor parenchyma have therefore been developed to achieve therapeutic concentrations of these drugs within the brain while minimizing systemic toxicity. With use of these polymers, successful antiangiogenic therapy for treatment of experimental intracranial malignancies has been achieved. This has been demonstrated with a variety of otherwise unrelated drugs -- including the angiostatic steroids, tetracycline derivatives, and amiloride -- which modulate collagenase activity, and thus, basement membrane and interstitial matrix metabolism. Controlled-release polymers provide a clinically practicable method of achieving sustained antiangiogenic therapy which can be readily used in combination with other treatment modalities such as cytoreductive surgery, radiation, and cytotoxic chemotherapy.

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.

Anti-angiogenic activity of a novel synthetic agent, 9alpha-fluoromedroxyprogesterone acetate

9Alpha-fluoromedroxyprogesterone acetate (FMPA) is a novel synthetic analog of medroxyprogesterone acetate (MPA), widely used as therapeutic agent for breast and endometrium cancers. FMPA showed almost the same binding affinities to the progesterone and glucocorticoid receptors as MPA. In the rabbit corneal assay, FMPA, MPA and fumagillin significantly inhibited the angiogenic response induced by rat mammary tumor at doses of 0. 1, 1 and 50 microg/pellet, respectively, so FMPA showed greater anti-angiogenic activity than MPA and fumagillin. In the mouse dorsal air sac method, FMPA inhibited the mouse sarcoma 180 cell-induced angiogenesis by oral administration at a dose of 200 mg/kg. FMPA inhibited the activity of plasminogen activator (PA) in bovine endothelial cells. These results suggest that FMPA may be useful for diseases associated with angiogenesis by oral administration.

Angiostatic activity of steroids in the chick embryo CAM and rabbit cornea models of neovascularization

Ocular neovascular diseases represent a major cause of blindness in the world. Angiostatic steroids are a unique class of compounds which inhibit the formation of new blood vessels in various models, including ocular models of angiogenesis. In search of potent new anti-angiogenic agents for the treatment of ocular neovascular disease, a large group of steroids were evaluated for angiostatic activity in the chick embryo CAM model. Angiostatic activity was found among all steroid classes included in the study. There was a good correlation between the angiostatic efficacies of 15 diverse steroids tested in the chick CAM and in the rabbit LPS-induced corneal pocket models of neovascularization (r=0.76, p=0.01). These studies show that potent angiostatic steroids inhibit neovascularization in two different animal models, suggesting a common mechanism of action. Glucocorticoid therapy is sometimes associated with ocular side effects. Two of the most potent angiostatic steroids, AL-3789 and AL-4940, were evaluated for glucocorticoid-mediated antiinflammatory activity in the in vitro U937 cell model of LPS-induced IL-1 induction and found to be devoid of glucocorticoid activity. Angiostatic steroids which lack glucocorticoid activity should be attractive drug candidates for treating ocular neovascular disease.

Adjuvant Therapy with High-Dose Medroxyprogesterone Acetate for Operable Breast Cancer

BACKGROUND: Medroxyprogesterone acetate (MPA) produces a comparable or higherresponse rate in metastatic breast cancer compared with tamoxifen which is alsocommonly used for adjuvant endocrine therapy. Several studies in the West have indicated the efficacy of MPA when used as an adjuvant to surgery in certain subsets of patients. The present study was undertaken as a multicenter open study in Japan to investigate the safety and efficacy of MPA in adjuvant endocrine therapy. Method and Patients: A combination of 800 mg/day MPA and a fluorouracil compound for 6 months was given postoperatively to 119 patients with stage II or IIIabreast cancer in 32 participating hospitals between June 1987 and June 1989. RESULTS: Among the 119 patients, 59 patients (49.6%) experienced some kind ofadverse reaction. The major adverse reaction was abnormal menstruation, seen in 13 (25.0%) of the 52 premenopausal patients. Vaginal bleeding was a major adverse reaction in the 67 postmenopausal patients (8/67 or 11.9%). An increase in body weight and moon face were observed in 23 (19.3%) and 9 (7.6%) of the 119 patients, respectively. Administration of drugs was discontinued because of adversereaction in 17 patients (14.3%), and dose reduction or temporary suspension wasnecessary in 7 patients (5.9%). Increase in body weight was the main reason fordiscontinuation of the treatment. No severe adverse reactions were observed. After a median follow-up of 74.5 months (range, 2.2-90.0 months), 84 of the 119 patients are alive with no evidence of disease. The 3-year and 5-year disease-freesurvival rates were 88.2% and 82.6% in stage II patients, and 64.7% and 52.9% in stage IIIa patients, respectively. The 3-year and 5-year disease-free survivalrates according to age were 87.8% and 79.3% in patients aged 50 years or more, and 78.6% and 71.4% in patients aged under 50 years. CONCLUSION: These results show that 800 mg/day MPA plus a fluorouracil compound can be administered with acceptable morbidity as an adjuvant treatment to selected breast cancer patients.

Angiogenesis in malignancies of the female genital tract

OBJECTIVE

The purpose of this work was to review current knowledge pertaining to angiogenesis in malignancies of the female genital tract.

METHODS

We identified studies published in the English language regarding angiogenesis in gynecologic malignancies. The studies were obtained from a MEDLINE search from 1966 through June 1998; additional sources were identified through cross-referencing.

RESULTS

A growing body of evidence confirms the ability of vulvar and cervical squamous cell carcinomas and endometrial and ovarian adenocarcinoma to induce angiogenesis. In vulvar intraepithelial neoplasia a correlation between vascular endothelial growth factor (VEGF) expression, microvessel density (MVD), and progression of dysplasia has been demonstrated. In invasive vulvar carcinoma, high VEGF expression and MVD portend poor prognosis. Currently a debate exists regarding the ability of cervical squamous intraepithelial neoplasia to induce angiogenesis. Most studies, however, indicate angiogenesis to be of prognostic value in patients with invasive squamous cell carcinoma. The ability of complex endometrial hyperplasia to induce angiogenesis has been demonstrated. A direct correlation between angiogenesis, higher grade and depth of invasion in Stage I adenocarcinoma, and prognostic value in Stage I and II and recurrent disease has been noted. In ovarian epithelial adenocarcinoma, higher microvessel counts in the primary ovarian tumor or omental metastases may serve as a prognostic indicator for survival.

CONCLUSIONS

Similar to other malignant diseases, angiogenesis appears to play an important role in disease progression and survival in patients with gynecologic malignancies. Preliminary data indicate angiogenesis may serve as a prognostic indicator in vulvar and cervical squamous cell carcinomas and endometrial and ovarian adenocarcinomas. These findings may lead to future application of therapeutic trials with antiangiogenic factors.

The effect of medroxyprogesterone acetate on angiogenesis in complex endometrial hyperplasia

OBJECTIVE

To evaluate the effect of orally administered medroxyprogesterone acetate upon angiogenesis in the myometrium of patients with complex endometrial hyperplasia.

METHODS

Microvessel counts in the myometrium of consecutive patients with complex endometrial hyperplasia, treated with oral medroxyprogesterone acetate prior to hysterectomy (n = 12), were compared with microvessel counts of consecutive control patients with complex endometrial hyperplasia without prehysterectomy medroxyprogesterone acetate treatment (n = 15). All specimens were stained immunohistochemically for factor VIII-related antigen as a sensitive and specific marker for vascular endothelium. Areas with the highest angiogenic intensity, within the myometrium immediately underlying complex endometrial hyperplasia, were selected. Three fields (x400) were selected for each slide, and the mean microvessel count per high-power field was calculated. Statistical analysis included factorial analysis of variance/covariance, and multiple regression analysis with P < 0.05 considered significant throughout.

RESULTS

Microvessel counts of uterine specimens of patients with complex endometrial hyperplasia treated with oral medroxyprogesterone acetate were significantly lower than microvessel counts of control patients with complex endometrial hyperplasia without medroxyprogesterone acetate therapy (median 20, range 11-37 versus median 38, range 20-130, respectively, P < 0.001).

CONCLUSION

Orally administered medroxyprogesterone acetate has a significant antiangiogenic effect upon myometrium immediately underlying complex endometrial hyperplasia.

The proteasome is involved in angiogenesis

The proteasome is a recently identified intracellular protease whose catalytic active site is a threonine residue and has been shown to play key roles in a variety of important intracellular events, including cell cycle progression, the antigen-presenting pathway, and apoptosis. However, its biological significance in multicellular organisms is still largely unknown because of lack of experimental systems for its study. Here we verified potential involvement of the proteasome in angiogenesis using lactacystin, a specific proteasome inhibitor. Lactacystin treatment resulted in almost complete prevention of in vivo neovascularization in the developing chick embryo chorioallantoic membrane. It also inhibited vascular endothelial tube formation on Matrigel, a model for in vitro angiogenesis, in a concentration-dependent fashion. Moreover, it prevented production of plasminogen activator, an important protease responsible for induction of angiogenesis, by endothelial cells, which correlated well with its suppression of intracellular proteasome activity. Our studies suggest that the proteasome operates in the process of angiogenesis, a phenomenon essential in important physiological and pathological settings.

Predictive value of serum medroxyprogesterone acetate concentration for response in advanced or recurrent breast cancer

Medroxyprogesterone acetate (MPA) is one of the most commonly prescribed drugs for endocrine therapy of metastatic breast cancer. In this study, the serum MPA concentration was measured by high-performance liquid chromatography (HPLC) and evaluated for its usefulness in predicting the response in 79 cases of advanced or recurrent breast cancers. Overall, 29 patients (37%) achieved an objective response. The response rate correlated significantly with the oestrogen receptor (ER) status (P = 0.03), proliferative activity determined by DNA polymerase alpha (P = 0.04), the disease-free interval (DFI) (P = 0.05) and the serum MPA concentration (P < 0.001). Patients with ER-positive tumours, lower proliferative activity, a longer (DFI) or a higher serum MPA concentration responded more frequently. The mean serum MPA concentration in the responders with ER-positive tumours (P = 0.01) or tumours with a lower proliferative activity (P = 0.008) were significantly lower than in cases with ER-negative tumours or tumours with a higher proliferative activity, respectively. Cases with soft tissue metastases showed responses at significantly lower MPA concentrations (P = 0.003) than those with bone or visceral metastases. Furthermore, there was a dramatic decrease in the MPA concentration when a responder with a high concentration became unresponsive to the therapy. Thus, the serum MPA concentration is a determining factor for the response to treatment.

Inhibition of preretinal and optic nerve head neovascularization in pigs by intravitreal triamcinolone acetonide

PURPOSE

The authors tested the antiangiogenic properties of intravitreally administered triamcionolone acetonide in a pig model of preretinal neovascularization to determine the effectiveness of this therapy in preventing neovascularization.

METHODS

In 14 eyes of seven pigs, branch retinal vein occlusions were created in a standardized manner using photodynamic thrombosis with rose bengal dye and thermal burns from the argon green laser. Intravitreal injection of approximately 4 mg of triamcinolone acetonide was performed in one eye of each animal, and eyes were followed clinically for 12 weeks with ophthalmoscopy and fundus photography. A standardized grading system was developed to permit masked assessment of disc proliferations from fundus stereophotographs. After death, all neovascularization was confirmed histopathologically and a final grade was assigned to each eye. Statistical analysis employed use of a nonparametric test of the paired data.

RESULTS

Significant inhibition of neovascularization was observed in triamcinolone-treated eyes (P = 0.0156). Although none of the steroid-injected eyes demonstrated clinically evident new vessels, histopathologic and photographic analysis results demonstrated fine new vessels on the optic disc in four eyes. In all of the untreated eyes, neovascularization of a moderate (II) to high (III to IV) grade developed.

CONCLUSIONS

Intravitreal triamcinolone acetonide effectively inhibited preretinal and optic nerve head neovascularization in the pig model. The grading system used permitted masked assessment of outcome and paired analysis allowed a conclusion to be drawn from a relatively small number of eyes. The mechanisms by which triamcinolone acetonide inhibits neovascularization remain to be elucidated.

Evaluation of angiogenic inhibitors with an in vivo quantitative angiogenesis method using agarose microencapsulation and mouse hemoglobin enzyme-linked immunosorbent assay

In the present work, using a previously reported in vivo quantitative tumor-angiogenesis model, we attempted to ascertain whether this animal model is suitable for practical use in monitoring inhibitors of tumor angiogenesis. Mouse sarcoma-180 cells, human A431 cells or rat C6 cells microencapsulated in agarose beads were implanted s.c. into C57BL/6 mice. The level of blood vessel induction at the agarose pellet site was evaluated using mouse hemoglobin enzyme-linked immunosorbent assay on day 10 after implantation. Hydrocortisone, tetrahydro-S, medroxyprogesterone acetate, pentosan polysulfate and suramin inhibited blood vessel growth in our in vivo tumor-angiogenesis assay system, and heparin enhanced the antiangiogenic effects of hydrocortisone and tetrahydro-S. These results are almost entirely consistent with those observed in common assay systems, and suggest that this method may be useful for the identification and quantitative evaluation of inhibitors of tumor angiogenesis.

Selective enhancement by tumor necrosis factor-alpha of vascular permeability of new blood vessels induced with agarose hydrogel-entrapped Meth-A fibrosarcoma cells

We have previously developed a simple and quantitative method for assessment of in vivo tumor cell-induced angiogenesis by means of microencapsulation of tumor cells in agarose hydrogel and mouse hemoglobin ELISA (mHb-ELISA). In this article, we report that the new blood vessels induced with agarose-encapsulated tumor cells have the same sensitivity to tumor necrosis factor-alpha (TNF-alpha) as the original solid-tumor vessels. Agarose beads (average diameter = 200 microns), in which Meth-A fibrosarcoma cells were microencapsulated, were subcutaneously implanted in non-syngeneic ddY mice. Ten days later, extensive angiogenesis was observed on the implanted sites of Meth-A agarose heads, whereas no new blood vessels were induced with cell-free agarose heads. The vascular permeability of the new blood vessels induced with agarose-microencapsulated Meth-A cells was selectively and significantly enhanced by the i.v. injection of TNF-alpha, and it reached the maximum level at 2 h after the injection of TNF-alpha. At 4 h after the injection of TNF-alpha, the vascular permeability was reduced to the basal level. This permeability profile in Meth-A agarose beads in ddY mice is very similar to that in Meth-A solid tumor in syngeneic BALB/c mice. On the other hand, TNF-alpha-treatment did not affect the vascular permeability of other normal tissues or inflammatory tissue in ddY mice. These results strongly suggest that the new blood vessels induced with agarose-microencapsulated tumor cells have the specific characteristics of tumor vessels. Our in vivo angiogenesis assay system should be useful not only to screen anti-angiogenetic agents, but also to elucidate the mechanism of tumor angiogenesis.

Inhibition of tumor angiogenesis

The exponential growth of solid tumors depends upon induction of new vessel growth, a process mediated by diffusable angiogenic factors produced by tumor cells. By inhibiting angiogenesis, it is now possible to modulate tumor growth and metastasis in laboratory animals. The first described inhibitor of angiogenesis was a protein derived from cartilage. Other important classes of antiangiogenic agents include angiostatic steroids combined with heparin or heparin derivatives, and the synthetic derivatives of fumigallin. As the mechanisms of action of these and other angiostatic agents are being elucidated, it is becoming apparent that many modulators of collagen metabolism inhibit angiogenesis and may offer clinically useful anticancer treatments. Minocycline and other tetracycline derivatives with anticollagenase properties have been shown to be potent inhibitors of angiogenesis. These agents, when administered with other standard cancer therapies, help prolong survival in laboratory animals with solid tumors. Further studies of these biologic response modifiers of tumor progression are under way in the hope that they will offer effective new treatments for cancer in humans.

Angiogenesis inhibition: a review

In this review we discuss the concept of anti-angiogenesis, which is the inhibition of neovascularization. Anti-angiogenic agents are viewed from the standpoint of their effect on various elements of the angiogenic process, including induction of vascular discontinuity, endothelial cell movement, endothelial cell proliferation, and three-dimensional restructuring of patent vessels. An effort is made to place the many different approaches to anti-angiogenesis research into a comprehensible structure, in order to identify problems of evaluation and interpretation, thereby providing a clearer basis for determining promising and needed directions for further investigation.

Modulation of bovine microvascular endothelial cell proteolytic properties by inhibitors of angiogenesis

A tightly controlled increase in extracellular proteolysis, restricted both in time and space, is an important component of the angiogenic process, while anti-proteolysis is effective in inhibiting angiogenesis. By focussing on the plasminogen activator (PA)-plasmin system, the objective of the present studies was to assess whether previously described inhibitors of angiogenesis modify bovine microvascular endothelial cell proteolytic properties. We demonstrate that although synthetic angiostatic steroids (U-24067 and U-42129), heparin, suramin, interferon alpha-2a, and retinoic acid are all inhibitors of in vitro angiogenesis, each of these agents has distinct effects on the plasminogen-dependent proteolytic system. Specifically, angiostatic steroids and interferon alpha-2a reduce urokinase-type PA (u-PA) and PA inhibitor-1 activity, while heparin and retinoic acid increase u-PA activity. Suramin reduces cell-associated u-PA activity and greatly increases PAI-1 production at doses which induce monolayer disruption. These findings demonstrate that a spectrum of alterations in extracellular proteolysis is associated with anti-angiogenesis, and that anti-angiogenesis and anti-proteolysis are not necessarily correlated. A reduction in extracellular proteolysis would be expected to reduce invasion, whereas an increase in proteolysis might modulate the activity of inhibitory cytokines, which in turn could reduce endothelial cell proliferation and migration and inhibit angiogenesis. The spectrum of effects on different elements of the PA system observed in response to the agents assessed suggests that the role of modulations in extracellular proteolytic activity in anti-angiogenesis is likely to be varied and complex.

Regulation of in vitro glia-induced microvessel morphogenesis by urokinase

Plasminogen activators (PAs) regulate a variety of processes involved in tissue morphogenesis and differentiation. We used a coculture system in which microvascular endothelial cells are induced by glial cells to form capillary-like structures in order to examine the role of urokinase-type PA (uPA) during microvessel morphogenesis within the central nervous system (CNS). Endothelia-derived uPA activity decreased sevenfold within glial-endothelial cocultures when capillary-like structures were formed. Incubation of cocultures with concentrations of phorbol 12-myristate 13-acetate (0.1 and 1.0 nM) that induced endothelial uPA activity (45-210%) inhibited endothelial differentiation (25-70%). Furthermore, incubation of cocultures with proteolytically active low molecular weight uPA (5-500 IU/ml) inhibited endothelial differentiation (37-75%), whereas the amino terminal cell-binding fragment of uPA had minimal effect. Inhibition of plasminogen activation in cocultures with the serine protease/plasmin inhibitors aprotinin and soybean trypsin inhibitor increased glia-induced capillary-like structure formation (96-98%). These findings establish a paracrine/autocrine function for urokinase and its inhibitors in regulating endothelial responses to perivascular glia and provide insight into mechanisms of microvascular reactions to CNS pathology.

Angiostatic activities of medroxyprogesterone acetate and its analogues

The effects of medroxyprogesterone acetate (MPA) (I) and related compounds (II-VI) upon angiogenesis induced by basic fibroblast growth factor (bFGF) or transforming growth factor-alpha (TGF-alpha) were investigated using a rabbit corneal system for assay of angiogenesis. Dexamethasone (Dex) was used as a positive control. The MPA analogues tested were 6,6'-dehydro-MPA (II), megestrol acetate (III), 1-dehydromegestrol acetate (IV), melengestrol acetate (V), and 1-dehydromelengestrol acetate (VI). The inhibitory activities of these steroids using bFGF were in the order: Dex = MPA = (VI) = (V) > (IV) > (III). Steroid (II) was inactive. 5 alpha-dihydrotestosterone was weakly active, while estradiol-17 beta and progesterone were inactive. The angiostatic activity of MPA was completely abolished by mefipristone (RU 486) which showed no anti-angiogenic activity in this assay. With TGF-alpha, the order of angiostatic activities was Dex = (VI) > (IV) > (III) > (V). Steroid (II) was again inactive. Dex, MPA, and all the MPA analogues except steroid (II) markedly inhibited the activity of plasminogen activator secreted by cultured calf pulmonary artery endothelial cells, but did not inhibit growth of these cells. The binding affinities of MPA and its analogues to glucocorticoid, progesterone and androgen receptors were determined, but were found not to be correlated with their angiostatic activities.

Radicicol, a microbial cell differentiation modulator, inhibits in vivo angiogenesis

Angiogenesis plays a significant role in various pathological states, including the progressive growth of solid tumors, rheumatoid arthritis, psoriasis, and diabetic retinopathy, in addition to its crucial role in embryonic development. Recent studies have revealed that an angiogenesis inhibitor is efficacious for these so-called angiogenic diseases. In the previous studies, we found that retinoids and vitamin D3 analogs, which are known to exhibit cell differentiation-modulating activity, effectively inhibit angiogenesis in vivo, thus forming the basis of our working hypothesis that a modulator of cell differentiation is capable of affecting angiogenesis. In this study, to verify this hypothesis further, radicicol (syn. monorden; 5-chloro-6-(7,8-epoxy-10-hydoxy-2-oxo-3,5-undecadienyl)-beta -resorcylic acid mu-lactone), a microbial cell differentiation modulator from a fungus, a strain of Neocosmospora tenuicristata, was examined for its anti-angiogenic activity in a bioassay system involving chorioallantoic membranes of growing chick embryos. The microbial cell differentiation modulator dose dependently inhibited embryonic angiogenesis, the ID50 value being 200 ng/egg. Radicicol also inhibited both the proliferation of and plasminogen activator production by vascular endothelial cells in the nM concentration range in a concentration-dependent manner, suggesting the possible involvement of these inhibitory effects in the anti-angiogenic action of the microbial product. These results indicate that radicicol might be a potential drug for treating different angiogenesis-dependent diseases, such as solid tumors, psoriasis, rheumatoid arthritis, and diabetic retinopathy.

Mechanism of action of angiostatic steroids: suppression of plasminogen activator activity via stimulation of plasminogen activator inhibitor synthesis

Recently, a novel class of angiostatic steroids which block angiogenesis in several systems has been described. Since the elaboration of proteases is believed to be an important component of angiogenesis, we tested whether these steroids blocked the fibrinolytic response of endothelial cells to the angiogenic protein, basic fibroblast growth factor [bFGF]). Cultured bovine aortic endothelial (BAE) cells were incubated with bFGF and/or medroxyprogesterone acetate (MPA), an angiostatic steroid which has been shown to inhibit vascularization, collagenolysis, and tumor growth. When bFGF (3 ng/ml) was added to confluent monolayers of BAE cells, plasminogen activator (PA) activity in the medium was increased threefold. In contrast, MPA at 10(-6) M, 10(-7) M, 10(-8) M, and 10(-9) M decreased PA levels in the medium by 83%, 83%, 75%, and 39%, respectively. The stimulation of PA levels in BAE cells by bFGF (3 ng/ml) was abrogated by the presence of 10(-6) M MPA. This decrease in PA activity was found to be mediated by a significant increase in plasminogen activator inhibitor type-1 (PAI-1) production. MPA, therefore, negated one of the important enzymatic activities associated with the angiogenic process. In contrast to the decreased levels of secreted PA in cultures exposed simultaneously to MPA and bFGF, cell-associated PA levels remained high, consistent with earlier observations indicating that PAI-1 does not inhibit cell-associated PA. Thus, angiostatic steroids may exert their inhibitory effects on angiogenesis by increasing the synthesis of PAI-1. This, in turn, inhibits PA activity and, therefore, plasmin generation, which is essential for the invasive aspect of angiogenesis.

Dexamethasone reduces vascular density and plasminogen activator activity in 9L rat brain tumors

Angiogenesis, a process dependent upon perivascular proteolysis, is required for solid tumor growth and is inhibited by certain steroids including glucocorticoids. We examined the relationship between tumor growth and vessel density in experimental rat brain 9L glial tumors following chronic treatment with the glucocorticoid dexamethasone. Tumor growth was inhibited by intraperitoneal administration of 3 mg/kg/day dexamethasone. Maximal cross-sectional areas of post-implantation day 9 tumors were 4.6 +/- 1.0 mm2 in dexamethasone-treated animals and 17.0 +/- 3.4 mm2 in controls (P < 0.01). Microvessel density assessed by laminin immunohistochemistry was 59% lower in dexamethasone-treated tumors (P < 0.01). Plasminogen activator (PA) activity, a proteolytic enzyme related to endothelial migration and vessel growth, was 4.2 +/- 0.9 IU/micrograms protein in dexamethasone-treated tumors and 9.0 +/- 1.0 IU/micrograms protein in control tumors (P < 0.01). Exposure of cultured 9L and central nervous system microvessel endothelial cells to dexamethasone concentrations comparable to those achieved in vivo had no effect on cell growth, but reduced the PA activity of culture supernatant fractions by 78% and 99%, respectively. These findings suggest that inhibition of proteolytic steps involved in vessel growth may underlie, in part, the mechanism by which glucocorticoids decrease brain tumor growth.

Angiogenesis and angiogenesis inhibitors in paediatric diseases

Angiogenesis, the generation of new capillaries from existing blood vessels, is rarely observed in the healthy organism, but can present during various paediatric diseases. In this review, we describe recent progress in the understanding of pathological angiogenesis and approaches for an improved therapy of angiogenic childhood diseases.

Inhibitory effect of medroxyprogesterone acetate on angiogenesis induced by human endometrial cancer

OBJECTIVE

The purpose of this study was to investigate the effect of medroxyprogesterone acetate on angiogenesis induced by endometrial cancer and to elucidate the possible mechanisms by which it inhibits the growth of the cancer.

STUDY DESIGN

Tumors were obtained from 29 patients with endometrial adenocarcinoma, and angiogenesis was assayed in corneas of white rabbits.

RESULTS

Transplantation of tumor tissues into rabbit corneas induced angiogenesis in 70.4% of the corneas, but their transplantation with a pellet of medroxyprogesterone acetate induced angiogenesis in only 21.5% of the corneas. This compound also inhibited angiogenesis induced by acidic fibroblast growth factor and transforming growth factor-alpha.

CONCLUSION

Inhibition of angiogenesis may be one mechanism by which medroxyprogesterone acetate inhibits the growth of endometrial adenocarcinoma, and its inhibition of neovascularization induced by adenocarcinoma may be through its direct action on endothelial cells.

Okadaic acid is a potent angiogenesis inducer

Okadaic acid, which is a non-12-O-tetradecanoylphorbol-13-acetate (TPA)-type tumor promoter and an inhibitor of protein phosphatases 1 and 2A, induced angiogenesis in the chorioallantoic membrane of the chick embryo. Its potent angiogenic activity was dose-dependent. The minimum effective dose was 5 fmol/egg and the effective dose for 50% induction was 90 fmol/egg. These results indicated that okadaic acid exhibits angiogenic activity one order of magnitude stronger than that of TPA (reported previously). Moreover, the time-course of angiogenesis induction by okadaic acid was much slower than that by TPA. The difference is consistent with the time-courses of other biochemical and biological activities and also various gene expressions induced by okadaic acid and TPA, indicating that the difference in the time-course is associated with their mechanisms of action. We conclude that okadaic acid induces angiogenesis through a different pathway than does TPA, indicating the existence of a new mechanism of angiogenesis induction.