Antiangiogenic potential of 10-hydroxycamptothecin

The Effect of Hydroxycamptothecin on Wound Healing Following Reduction of the Knee Intra-Articular Adhesion in Rabbits

Topical application of 10-hydroxycamptothecin (HCPT) can reduce intra-articular scar adhesion after knee surgery, but the effect of HCPT on wound healing has not yet been elucidated. The study investigates the effect of the topical application of HCPT on wound healing after knee surgery in rabbits. Forty New Zealand white rabbits were divided into five groups: 2.0, 1.0, 0.5, and 0.1 mg/ml HCPT groups and control group. Approximately 10 mm × 10 mm of the cortical bone was removed from both sides of the femoral condyle, and the underneath of the cancellous bone was exposed. HCPT in various concentrations or saline was applied to the decorticated sites. Two weeks after surgery, the intra-articular adhesion was evaluated by Masson's trichrome staining. The blood vessel density and the fibroblast counting were evaluated by hematoxylin-eosin staining. The Vascular endothelial growth factor (VEGF) expression was evaluated by immunohistochemical staining and mRNA measurement. The recovery of all rabbits was stable after surgery. Topical application of HCPT could reduce intra-articular adhesion after 2 weeks. The blood vessel density, the number of fibroblast, and the level of VEGF expression in 2.0 and 1.0 mg/ml HCPT groups were lower than those of 0.5 mg/ml HCPT group, 0.1 mg/ml HCPT group, and the control group. However, there was no difference in multiple parameters between 1.0 and 2.0 mg/ml HCPT groups. Topical application of HCPT could reduce intra-articular scar adhesion in rabbits, but HCPT with concentrations above 1.0 mg/ml may affect the wound healing process by inhibiting the angiogenesis and fibroblast proliferation.

Integration of an anti-tumor drug into nanocrystalline assemblies for sustained drug release

Delicate mesoscopic architectures, bearing complex forms with multiple hierarchy levels, lead to significant functions in biogenic minerals. Herein, a bio-inspired approach was developed to fabricate comet-shaped assemblies of an anti-tumor drug - 10-hydroxycamptothecin (HCPT). The anti-solvent co-precipitation of HCPT and the excipient - PEG-b-PLGA - within the emulsifier leads to the immediate nucleation of comet bundles, followed by a secondary nucleation to generate the comet head, which is an assembly of nanofibers aligned almost in parallel. The continuous manufacturing furnishes drug-excipient hybrid particles with high drug-loading and a sustained drug release profile. This simple and efficient bio-inspired approach led to a promising sustained local drug delivery system, and could be extended to the fabrication of other functional organic materials bearing mesoscopic structural units.

Anti-angiogenic activity of salvicine

CONTEXT

Salvicine is a pharmacologically active derivative from Chinese medicinal plant Salvia prionitis Hance (Labiatae). It has been reported that salvicine inactivates β1 integrin and inhibits integrin-mediated cell adhesion to fibronectin. Given the emerging correlation between integrins and angiogenesis, we propose that salvicine abolishes cell adhesion and subsequent metastasis by inhibiting angiogenisis.

OBJECTIVE

The anti-angiogenesis activities of salvicine were investigated for the first time.

MATERIALS AND METHODS

The cytotoxicity of salvicine on human microvascular endothelial cells (HMECs) and non-small cell lung adenocarcinoma A549 cells were measured at doses between 0.625 and 200 µM. Changes of cell migration were detected with doses of salvicine at 1.25-5 µM, and basement membrane matrigel matrix was used for the assessment of tube formation at concentrations ranging from 0.078 to 1.25 µM. In addition, mRNA expression of basic fibroblast growth factor (bFGF) in A549 cells was studied with the RT-PCR assay.

RESULTS

In vitro studies revealed that the IC50 of salvicine on A549 cells (18.66 µM) was two-fold higher than that of HMECs (7.91 µM). Salvicine (1.25, 2.5 and 5.0 μM) inhibited significantly the endothelial cell migration up to 56, 73 and 82%, respectively. Salvicine decreased capillary-like tube formation of HMECs with high potency. Furthermore, it (30 µM) markedly reduced the mRNA expression of bFGF in A549 cells, while vascular endothelial growth factor (VEGF) mRNA expression remained unchanged.

DISCUSSION AND CONCLUSION

Our results suggest that salvicine has potent anti-angiogenic activity through the inhibition on the sequential angiogenic cascades: proliferation, migration and tube formation and is associated with influence on the expression of bFGF of tumor cell.

Newly discovered angiogenesis inhibitors and their mechanisms of action

In the past decade, the success of angiogenesis inhibitors in clinical contexts has established the antiangiogenic strategy as an important part of cancer therapy. During that time period, we have discovered and reported 17 compounds that exert potent inhibition on angiogenesis. These compounds exhibit tremendous diversity in their sources, structures, targets and mechanisms. These studies have generated new models for further modification and optimization of inhibitory compounds, new information for mechanistic studies and a new drug candidate for clinical development. In particular, through studies on the antiangiogenic mechanism of pseudolaric acid B, we discovered a novel mechanism by which the stability of hypoxia-inducible factor 1α is regulated by the transcription factor c-Jun. We also completed a preclinical study of AL3810, a compound with the potential to circumvent tumor drug resistance to a certain extent. All of these findings will be briefly reviewed in this article.

The Chick Embryo Chorioallantoic Membrane as an In Vivo Assay to Study Antiangiogenesis

Antiangiogenesis, e.g., inhibition of blood vessel growth, is being investigated as a way to prevent the growth of tumors and other angiogenesis-dependent diseases. Pharmacological inhibition interferes with the angiogenic cascade or the immature neovasculature with synthetic or semi-synthetic substances, endogenous inhibitors or biological antagonists.The chick embryo chorioallantoic membrane (CAM) is an extraembryonic membrane, which serves as a gas exchange surface and its function is supported by a dense capillary network. Because its extensive vascularization and easy accessibility, CAM has been used to study morphofunctional aspects of the angiogenesis process in vivo and to study the efficacy and mechanism of action of pro- and anti-angiogenic molecules. The fields of application of CAM in the study of antiangiogenesis, including our personal experience, are illustrated in this review article.

Metronomic treatment of malignant glioma xenografts with irinotecan (CPT-11) inhibits angiogenesis and tumor growth

Irinotecan (CPT-11) has shown emerging promise in the treatment of malignant gliomas. It is believed the mechanism of action of irinotecan is to sensitize glioma cells to the cytotoxic action of radiation therapy and alkylating agents. However, clinical trials using weekly or three-weekly doses of CPT-11 have demonstrated imaging responses in only 10-15% of patients. In this study, we evaluated another mechanism of action, angiosuppression by CPT-11 of ACNU-resistant gliomas, using a metronomic administration schedule. Two different types of treatment, (1) conventional and (2) metronomic, were applied to the subcutaneous U87 model. We found that metronomic administration of CPT-11 significantly inhibited malignant glioma growth by inhibiting angiogenesis; this treatment procedure reduced the number of tumor vessels and the area of hypoxic lesions and reduced expression of VEGF and HIF-1alpha, the most important angiogenic factors in gliomas. Metronomic treatment was superior to conventional treatment with regard to the severe systemic side effect of body weight loss. The growth inhibitory effect was very similar for both low and high doses of CPT-11. These angiosuppressive effects of CPT-11 show promise for another use of CPT-11 in metronomic and scheduled angiosuppressive chemotherapy with low dose and long-term administration for malignant gliomas without systemic side effects.

Evaluation of the antiangiogenic potential of AQ4N

PURPOSE

A number of cytotoxic chemotherapy agents tested at low concentrations show antiangiogenic properties with limited cytotoxicity, e.g., cyclophosphamide, tirapazamine, and mitoxantrone. AQ4N is a bioreductive alkylaminoanthraquinone that is cytotoxic when reduced to AQ4; hence, it can be used to target hypoxic tumor cells. AQ4N is structurally similar to mitoxantrone and was evaluated for antiangiogenic properties without the need for bioreduction.

EXPERIMENTAL DESIGN

The effect of AQ4N and fumagillin on human microvascular endothelial cells (HMEC-1) was measured using a variety of in vitro assays, i.e., 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, wound scrape, tubule formation, rat aortic ring, and invasion assays. Low-dose AQ4N (20 mg/kg) was also given in vivo to mice bearing a tumor in a dorsal skin flap.

RESULTS

AQ4N (10(-11) to 10(-5) mol/L) had no effect on HMEC-1 viability. AQ4N (10(-9) to 10(-5)mol/L) caused a sigmoidal dose-dependent inhibition of endothelial cell migration in the wound scrape model. Fumagillin showed a similar response over a lower dose range (10(-13) to 10(-9) mol/L); however, the maximal inhibition was less (25% versus 43% for AQ4N). AQ4N inhibited HMEC-1 cell contacts on Matrigel (10(-8) to 10(-5) mol/L), HMEC-1 cell invasion, and sprouting in rat aorta explants. Immunofluorescence staining with tubulin, vimentim, dynein, and phalloidin revealed that AQ4N caused disruption to the cell cytoskeleton. When AQ4N (20 mg/kg) was given in vivo for 5 days, microvessels disappeared in LNCaP tumors grown in a dorsal skin flap.

CONCLUSIONS

This combination of assays has shown that AQ4N possesses antiangiogenic effects in normoxic conditions, which could potentially contribute to antitumor activity.

Differential proinflammatory and angiogenesis-specific cytokine production in human pulmonary endothelial cells, HPMEC-ST1.6R infected with dengue-2 and dengue-3 virus

In this study, the ability of dengue virus serotypes 2 (DENV-2) and 3 (DENV-3) to infect and induce increased production of proinflammatory cytokines in a pulmonary endothelial cell line (HPMEC-ST1.6R) was investigated. This cell line exhibits the major constitutive and inducible endothelial cell characteristics, as well as angiogenic response. DENV-2 and DENV-3 infection was confirmed by an observed cytopathic effect (CPE), as well as RT-PCR and immunofluorescence assays. Increases in Th-1 and Th-2 cytokines IL-4, IL-8, IL-6, IL-10, GM-CSF, INF-gamma, and tumor necrosis factor (TNF-alpha) within DENV-2- and DENV-3-infected cells were demonstrated using a microbead-based Bio-plex assay. Proinflammatory cytokine increases and the expression of a potent angiogenic inducer protein, VEGF were confirmed by dot-blot analysis using the TranSignal Human Angiogenesis Antibody Array. Dengue virus-infected HPMEC-ST1.6R cells exhibited an elongated cytoplasmic morphology, possibly representing a response to VEGF and activation of angiogenesis. The increased levels of Th-1 cytokines and VEGF in DENV-2 virus infected-HPMEC-ST1.6R could be distinguished from those infected by DENV-3. This suggests that cytokine patterns associated with DENV infections may be serotype and strain-specific. The experimental approaches described here could be developed further into a useful diagnostic tool for the characterization of dengue hemorrhagic fever cases, leading to enhancement of treatment therapy.

4-nitroquinoline-1-oxide induces the formation of cellular topoisomerase I-DNA cleavage complexes

RecQ helicase BLM-deficient cells are characteristically hypersensitive to 4-nitroquinoline-1-oxide (4NQO). We recently reported that isogenic BLM-deficient cells (PNSG13) are more sensitive than BLM-complemented cells (PNSF5) to camptothecin, which specifically traps topoisomerase I cleavage complexes (Top1cc). We now report that PNSG13 are also 3.5-fold more sensitive to 4NQO compared with PNSF5 and that 4NQO induces higher levels of Top1cc and reduced histone gamma-H2AX in PSNG13 than in PNSF5. Similarly, 4NQO induces more Top1cc in primary fibroblasts from a patient with Bloom syndrome than in normal human fibroblasts. 4NQO also induces Top1cc in colon cancer HCT116 and HT29 cells in a time- and concentration-dependent fashion. Of note, distinct from camptothecin, the Top1cc produced by 4NQO accumulate progressively after 4NQO addition and persist following 4NQO removal. The Top1cc induced by 4NQO are detectable by alkaline elution. To examine the functional relevance of the Top1cc induced by 4NQO, we used two stable topoisomerase I small interfering RNA (siRNA) cell lines derived from HCT116 and MCF7 cells. Both topoisomerase I siRNA cell lines are resistant to 4NQO, indicating that Top1cc contribute to the cellular activity of 4NQO. Collectively, these data show that 4NQO is an effective inducer of cellular Top1cc. Because 4NQO does not directly trap Top1cc in biochemical assays, we propose that active metabolites of 4NQO trap Top1cc by forming DNA adducts. Induction of Top1cc and histone gamma-H2AX by 4NQO may contribute to the cellular effects of 4NQO, including its selective activity toward RecQ helicase BLM-deficient cells.

Clinical study on combined chemotherapy of oxaliplatin or hydroxycamptothecine plus 5-fluorouracil and leucovorin for advanced colorectal cancer

AIM: To evaluate the short-time efficacy, side effects, survival of combined chemotherapy of oxaliplatin or hydroxycamptothecine plus 5-fluorouracil and leucovorin for advanced colorectal cancer.

METHODS: Sixty patients with advanced colorectal cancer confirmed by pathology were included in this study. The patients in group A (n = 40) received oxaliplatin plus 5-fluorouracil and leucovorin, and those in group B (n = 20) were treated with hydroxycamptothecine plus 5-fluorouracil and leucovorin. Both regimens had 21-day cycle, i.e., the treatment was repeated once every 3 wk and the side effects were evaluated. The efficacy was estimated two or three cycles after chemotherapy.

RESULTS: The efficacy rates were 30.0% (12/40) and 25.0% (5/20) in group A and B, respectively, and there was no significant difference between them (χ² = 0.531, P = 0.811). The 1-year survival rates (34.09% vs 38.55%, u = 0.3275, P > 0.05), median progression-free survival time (6.4 mo vs 7.3 mo, u = 1.5088, P > 0.05), and median overall survival time (10.2 mo vs 10.8 mo, u= 0.3487, P > 0.05) were not markedly different between group A and B, neither. The major side effects of grade Ⅲ and Ⅳ in both groups were myelosuppression and gastrointestinal reactions, and the incidence rate of diarrhea was significantly higher in group B than that in group A (χ² = 7.876, P = 0.044).

CONCLUSION: The efficacy is almost equal between combined chemotherapy of oxaliplatin or hydroxycamptothecine plus 5-fluorouracil and leucovorin for advanced colorectal cancer. Peripheral neuropathy appears more as the former is used, while diarrhea has a higher frequency as the latter is used.

Pseudolaric acid B inhibits angiogenesis and reduces hypoxia-inducible factor 1alpha by promoting proteasome-mediated degradation

PURPOSE

Pseudolaric acid B (PAB), the naturally occurring diterpenoid isolated from the root bark of Pseudolarix kaempferi Gordon tree (Pinaceae), possesses potent antifungal and pregnancy-terminating effects that may be tightly associated with angiogenesis. This study was to examine its angiogenic inhibition, impact on vascular endothelial growth factor (VEGF) secretion from tumor cells and the possible mechanism of action.

EXPERIMENTAL DESIGN

Angiogenesis inhibition was assessed by the human umbilical vascular endothelial cell proliferation, migration, and tube-formation assays, as well as the chorioallantoic membrane assay. ELISA, reverse transcription-PCR, and Western blotting analyses were performed to examine VEGF protein secretion, mRNA expression, and the possible mechanism in hypoxic MDA-MB-468 cells.

RESULTS

PAB displayed potent in vitro antiangiogenic activity shown by inhibiting VEGF-stimulated proliferation and migration and fetal bovine serum-stimulated tube formation of human umbilical vascular endothelial cells in a concentration-dependent manner. Moreover, PAB (10 nmol per egg) significantly suppressed in vivo angiogenesis in the chorioallantoic membrane assay. On the other hand, PAB abrogated hypoxia-induced VEGF secretion from MDA-MB-468 cells via reducing HIF-1alpha protein. Additional analyses using LY294002 and U0126 indicated that the increase in hypoxia-inducible factor 1 (HIF-1)alpha protein level was highly dependent on phosphatidylinositol 3'-kinase and p42/p44 mitogen-activated protein kinase activities in hypoxic MDA-MB-468 cells. However, PAB treatment did not affect the active (phosphorylated) forms of Akt and Erk. Interestingly, the selective proteasome inhibitor MG-132 completely reversed the reduction of HIF-1alpha protein in the PAB-treated MDA-MB-468 cells.

CONCLUSIONS

PAB displays the dual antiangiogenic activities of directly inhibiting endothelial cells and abrogating paracrine stimulation of VEGF from tumor cells due to reducing HIF-1alpha protein by promoting its proteasome-mediated degradation in MDA-MB-468 cells, which has potential clinical relevance.

Pseudolarix acid B inhibits angiogenesis by antagonizing the vascular endothelial growth factor-mediated anti-apoptotic effect

Angiogenesis is controlled by a number of growth factors, including vascular endothelial growth factor (VEGF). In this study, pseudolarix acid B, isolated from the traditional Chinese medicinal plant Pseudolarix kaempferi and originally identified as an early pregnancy-terminating agent, was evaluated for its potential as an angiogenesis inhibitor, using in vitro and in vivo models. After exposure to pseudolarix acid B 0.625-5 microM for 72 h, the proliferation of human umbilical vein endothelial cells was significantly inhibited. Pseudolarix acid B 0.313-2.5 microM for 24 h potently blocked the VEGF-induced tube formation of human umbilical vein endothelial cells in a dose-dependent manner. Matrigel plug assays disclosed that pseudolarix acid B reduced angiogenesis induced by VEGF in vivo. In addition, pseudolarix acid B antagonized VEGF-mediated anti-apoptotic effects on serum-deprived human umbilical vein endothelial cells and increased apoptosis of endothelial cells induced by VEGF in Matrigel plug assays. Moreover, pseudolarix acid B significantly inhibited VEGF-induced tyrosine phosphorylation of kinase insert domain-containing receptor/fetal liver kinase-1 (KDR/flk-1), in correlation with a marked decrease in the phosphorylation of Akt and extracellular signal-regulated kinases (ERK). These findings collectively suggest that pseudolarix acid B possesses anti-angiogenic activity. One of the main anti-angiogenesis mechanisms of pseudolarix acid B may involve antagonism of the VEGF-mediated anti-apoptosis effect via inhibition of KDR/flk-1, ERK1/2, and Akt phosphorylation in endothelial cells.

Anti-angiogenic effects of SN38 (active metabolite of irinotecan): inhibition of hypoxia-inducible factor 1 alpha (HIF-1?)/vascular endothelial growth factor (VEGF) expression of glioma and growth of endothelial cells

PURPOSE

Inhibition of angiogenesis is an important new treatment modality for malignancies, including gliomas. Vascular endothelial growth factor (VEGF) and hypoxia inducible factor-1alpha (HIF-1alpha) have been investigated as potent mediators of tumor angiogenesis. We investigated whether four major chemotherapeutic agents (ACNU, cisplatin, etoposide, and SN38) showed an angiosuppressive effect in vitro.

METHOD

The effects of ACNU, cisplatin, etoposide, and SN38 for endothelial cells were assessed by cell growth inhibition assay (WST-8 assay) and vessel formation assay (angiogenesis kit). The inhibitory effects of the HIF-1alpha and VEGF expression of glioma cells after SN38 treatment were assessed by real-time RT-PCR, Western blot, and ELISA.

RESULTS

SN38, but not other chemotherapeutic agents, selectively inhibited endothelial cell proliferation and three-dimensional tube formations at the 0.01 microM. Furthermore, SN38 significantly decreased the HIF-1alpha and VEGF expression of glioma cells in a dose- and time-dependent manner under normoxic and hypoxic conditions. SN38 has dual angiosuppressive actions, including both the inhibition of endothelial proliferation and tube formation, and the inhibition of the angiogenic cascade in glioma cells.

CONCLUSION

SN38 is an attractive agent as both a direct and indirect angiogenesis inhibitor and provides the anti-glioma agents with an angiosuppressive function.

Gimatecan, a novel camptothecin with a promising preclinical profile

The realization that position 7 of camptothecin allows several options in chemical manipulation of the drug has stimulated a systematic investigation of a variety of substituents in this position. These efforts resulted in the identification of a novel series of 7-oxyiminomethyl derivatives. Among compounds of this series we have selected a promising lipophilic derivative, gimatecan, for further development. The relevant features of gimatecan are: (i) marked cytotoxic potency, likely related to multiple factors, including a potent inhibition of topoisomerase I, a persistent stabilization of the cleavable complex, an increased intracellular accumulation and a peculiar subcellular localization; (ii) lack of recognition by known resistance-related transport systems; (iii) increased lactone stability and favorable pharmacokinetics; (iv) good oral bioavailability; and (v) an impressive antitumor efficacy in a large panel of human tumor xenografts, with various treatment schedules. Phase I clinical studies with oral administration support the preclinical results of the novel camptothecin. Using different schedules and dosing durations, gimatecan exhibited an acceptable toxicity profile, with myelotoxicity being the dose-limiting toxic effect. An appreciable number of tumor responses was achieved and favorable pharmacokinetics with a very long terminal half-life was observed. The clinical development of gimatecan is currently ongoing, with phase II studies in diverse tumor types (colon, lung, breast carcinoma and pediatric tumors).

Characterization of salvicine-resistant lung adenocarcinoma A549/SAL cell line

Salvicine is a diterpenoid quinone derived from a traditional Chinese medication that has been shown to possess potent in vitro and in vivo antitumor effects. This compound, which inhibits the activity of Topoisomerase II, was found to equipotently kill various multidrug-resistant tumor cells and their corresponding parental counterparts in vitro and to inhibit mdr1/P-gp expression in multidrug-resistant K562/A02 cells. To examine the features of tumor resistance to salvicine, we established a salvicine-resistant tumor cell subline of A549 lung adenocarcinoma cells. Compared with parental cells, A549/SAL cells displayed 8.91-fold resistance to salvicine and an average of 6.70-fold resistance to the antimetabolites. A549/SAL cells, however, were not resistant to alkylating agents, platinum compounds and other naturally-derived antineoplastics. RT-PCR analysis showed that the expression of mRNAs from the mdr-1, MRP, PCNA, topoisomerase II alpha and beta, GSTpi, p21 and GADD45 genes was not altered in the salvicine-resistant subline. In contrast, expression of p53 and bax mRNA was significantly lower, and expression of mdm2 mRNA was significantly higher, in A549/SAL cells compared to A549 cells. A549/SAL cells grew more slowly, and in a more scattered pattern, than A549 cells. In addition, the A549/SAL cells showed enhanced ability to migrate and invade in comparison to the parental cells. These results indicate that exposure to salvicine does not induce a tumor multidrug-resistant phenotype.

Quercetin, a dietary-derived flavonoid, possesses antiangiogenic potential

Quercetin, a dietary-derived flavonoid, suppresses tumor growth in vitro and in vivo, and inhibits the activity of tyrosine kinase. The effects of quercetin on the angiogenic process were examined in this study. Quercetin was found to inhibit several important steps of angiogenesis including proliferation, migration, and tube formation of human microvascular dermal endothelial cells in a dose-dependent manner. Additionally, the effect of quercetin on endothelial cell proliferation was confirmed using human umbilical vein endothelial cells. The activity of quercetin on the proliferation of endothelial cells was stronger than that on A549, BEL-7402, MKN-45 tumor cells and NIH-3T3 fibroblast cells. The chicken chorioallantoic membrane assay revealed that addition of quercetin displayed an antiangiogenic effect in vivo. After exposure to quercetin, a decrease in the expression and activity of matrix metalloproteinase-2, which is involved in the angiogenic process of migration, invasion, and tube formation, was observed by reverse transcription-polymerase chain reaction (RT-PCR) and gelatin zymography. These findings suggest that quercetin has antiangiogenic potential and that this effect may be related to an influence on the expression and activity of matrix metalloproteinase-2.