Hypoxia induces hemorrhagic transformation in pituitary adenomas via the HIF-1α signaling pathway

The hypoxia inducible factor 1 α (HIF-1α) activity has been associated with various hemorrhagic events. The biological role of HIF-1α in the hemorrhagic transformation of pituitary adenomas remains unknown. We hypothesized that fast growing tumor cells tend to predispose themselves to sublethal hypoxia and activate the HIF-1α signaling pathway, leading to hemorrhagic transformation in pituitary adenomas. Here, we used apoplectic and non-apoplectic pituitary adenomas to determine the involvement of HIF-1α signaling in intratumoral hemorrhage. We employed HIF-1α overexpression/knockdown strategies to examine the association between HIF-1α signaling and hemorrhagic presentation in?vitro and in?vivo. In support of our hypothesis, compared with non-hemorrhagic pituitary adenomas, higher cellular proliferation was observed in hemorrhagic ones and it correlated with increased HIF-1α signaling. HIF-1α overexpression activated its downstream genes, vascular endothelial growth factor and the proapoptotic BNIP3, in MMQ pituitary adenoma cells and this up-regulation was attenuated by HIF-1 siRNA. In?vivo studies using MMQ cell xenografts in nude mice showed that HIF-1α overexpression significantly promoted hemorrhagic transformation. Our study indicates that tumor hypoxia, following rapid tumor growth, may promote hemorrhagic transformation in pituitary adenomas via the HIF-1α signaling pathway.     

Human chondrosarcoma secretes vascular endothelial growth factor to induce tumor angiogenesis and stores basic fibroblast growth factor for regulation of its own growth.

Vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) are well-known factors that induce neovascularization in many tumors. The molecular mechanisms that regulate tumor angiogenesis in human chondrosarcoma are not clear. We assessed in this work the angiogenic activities of a human chondrosarcoma cell line (OUMS-27) in vivo and determined the efficacies of angiogenic factors derived from OUMS-27 cells on human umbilical vein endothelial cells (HUVECs) in vitro. Tumor xenografts induced an increase in the formation of neovessels, but the distributions of Ki-67 antigen, VEGF and bFGF were unaffected. We also demonstrated that OUMS-27 cells secreted VEGF(165) into the culture medium and that it was the maximal angiogenic factor to stimulate endothelial proliferation and migration in chondrosarcoma. Anti-VEGF antibodies induced an approximately 70% inhibition of these responses of HUVECs, but did not have any effect on OUMS-27 cells. Anti-bFGF antibodies suppressed not only the activities of HUVECs but also the growth of tumor cells in vitro. We indicate that angiogenesis is principally elicited by VEGF(165) and that tumorigenesis is mainly regulated by bFGF stored in the extracellular matrix of OUMS-27 cells. The present study may offer the availability of combination therapies for inhibition of VEGF and bFGF action on vascular endothelial cells and chondrosarcoma cells, respectively.     

Anti-tumor effect of lentivirus-mediated gene transfer of alphastatin on human glioma

Alphastatin, an endogenous angiogenesis inhibitor, has recently been used as an anticancer agent in several tumor models. This study was to investigate whether local sustained long-term expression of alphastatin could serve to diminish tumor growth of a human xenograft glioma model. We found that the recombinant alphastatin lentiviruses were able to stably infect HUVECs, and infected HUVECs could sustainably secrete alphastatin, which exhibited potent inhibitory effects on HUVECs migration, differentiation but not proliferation induced by vascular endothelial growth factor (VEGF) or basic fibroblast growth factor(bFGF). And the expression of secreted protein alphastatin markedly decreased tumor vascularization and inhibited tumor growth. Additionally, alphastatin inhibited VEGF- or bFGF-induced initial stage of angiogenesis by reducing JNk and ERK phosphorylation in vitro. Taken together, these data demonstrate that secreted protein alphastatin inhibits VEGF- or bFGF-induced angiogenesis by suppressing JNK and ERK kinases activation pathways in HUVECs, and markedly inhibits tumor angiogenesis in vivo. Consequently lentivirus-mediated gene transfer might represent an effective strategy for expression of alphastatin to achieve inhibition of human malignant glioma proliferation and tumor progression.     

Penta-O-galloyl-beta-D-glucose suppresses tumor growth via inhibition of angiogenesis and stimulation of apoptosis: roles of cyclooxygenase-2 and mitogen-activated protein kinase pathways

Recent studies have revealed that 1,2,3,4,6-penta-O-galloyl-beta-d-glucose (PGG) has anti-tumorigenic activity in vitro. In the present work, we evaluated the in vitro and in vivo antiangiogenic and antitumor activities of PGG and examined its molecular mechanisms. PGG significantly inhibited the proliferation and tube formation in basic fibroblast growth factor (bFGF)-treated human umbilical vein endothelial cells (HUVECs) at non-cytotoxic concentrations. PGG effectively disrupted the bFGF-induced neo-vascularization in chick chorioallantoic membrane (CAM) and in Matrigel plugs in the mice. When mice were intraperitoneally injected, PGG also significantly inhibited tumor angiogenesis induced by Lewis lung carcinoma (LLC) and the growth of LLC by 57 and 91% of control tumor weight at 4 and 20 mg/kg, respectively. Immunohistochemical analysis revealed decreased microvessel density, decreased expression of cyclooxygenase-2 (COX-2) and vascular endothelial growth factor (VEGF), reduced tumor cell proliferation and increased tumor cell apoptosis. Similarly, PGG significantly attenuated the expression of COX-2 and VEGF and reduced the secretion of VEGF and prostaglandin E2 in bFGF-treated HUVECs. Furthermore, the COX-2 inhibitor NS398 significantly inhibited tube formation and neo-vascularization in CAM, supporting the role of COX-2 in PGG inhibition of angiogenesis. PGG diminished the phosphorylation of extracellular signal regulated kinase 1/2, Jun NH2-terminal kinase and activated phospho-p38 mitogen-activated protein kinase (MAPK) in a dose-dependent manner in bFGF-treated HUVECs. In addition, p38 inhibitor SB203580 abolished the downregulation of COX-2, VEGF and the antiproliferative activity by PGG. Taken together, our data demonstrate that PGG exerts antitumor activity primarily via inhibition of angiogenesis through COX-2 and MAPK- dependent pathways.     

Norcantharidin: a potential antiangiogenic agent for gallbladder cancers in vitro and in vivo

Our objective was to explore the antiangiogenic activity of norcantharidin (NCTD) as an angiogenic inhibitor for gallbladder cancers. In vitro and in vivo experiments to determine the effects of NCTD on HUVECs, chicken CAM capillaries and gallbladder cancer xenograft angiogenesis in nude mice were respectively done. The MTT method was used to assay the cytotoxicity of NCTD on HUVECs. Immunofluorescence was used to evaluate HUVEC apoptosis. The scraping line method, matrigel invasion assay and tube formation assay were used to detect the migration, invasion and tube formation of HUVECs. A digital camera was used to observe chicken CAM capillaries. Experiments with NCTD in a xenograft model were used to observe the effect of NCTD on xenograft growth and survival of mice with xenografts. CD?? immunohistochemistry, flow cytometry and micro-MRA were used, respectively, to determine MVD, cell apoptosis and hemodynamic analysis of the xenografts. Immunohistochemistry and RT-PCR were used, respectively, to detect the expression of VEGF, Ang-2, TSP, TIMP-2 proteins/mRNAs of the xenografts. The xenograft MVD associated with tumor volume, the PCNA/apoptosis ratio and related-protein expression was evaluated simultaneously. We found that NCTD effectively inhibited the proliferation, migration, invasion and capillary-like tube formation of HUVECs in vitro; it reduced angiogenesis and directly destroyed the formed CAM capillaries in vivo. In the experiments in mice, NCTD not only inhibited significantly xenograft proliferation and growth, prolonged survival time of mice with xenografts, decreased the xenograft MVD and vascular perfusion, but also, similarly to ES, decreased significantly the expression of VEGF or Ang-2 protein/mRNA, increased the expression of TSP or TIMP-2 protein/mRNA. Moreover, the xenograft MVD was positively related with tumor volume, PCNA/apoptosis ratio, and VEGF or Ang-2 expression, respectively (all P<0.05), but negatively correlated with TSP or TIMP-2 expression (both P<0.05). These data showed that NCTD could serve as a potential antiangiogenic agent for gallbladder cancers.     

Antiangiogenic mechanisms of PJ-8, a novel inhibitor of vascular endothelial growth factor receptor signaling

Angiogenesis occurs not only during tissue growth and development but also during wound healing and tumor progression. Angiogenesis is a balanced process controlled by proangiogenic and antiangiogenic molecules. As a critical factor in the induction of angiogenesis, vascular endothelial growth factor (VEGF) has become an attractive target for antiangiogenic and cancer therapeutic agents. In an effort to develop novel inhibitors to block VEGF signaling, we selected Pj-8, a benzimidazole derivative, and investigated its inhibitory mechanisms in human umbilical vascular endothelial cells (HUVECs). Pj-8 concentration-dependently inhibited VEGF-induced proliferation, migration and tube formation of HUVECs. Pj-8 also suppressed VEGF-induced microvessel sprouting from aortic rings ex vivo and suppressed neovascularization of implanted matrigel plugs in vivo. Pj-8 inhibited VEGF-induced phosphorylation of VEGF receptor (VEGFR) 2 and the downstream protein kinases, including Akt, focal adhesion kinase, extracellular signal-regulated kinases and Src. Results from in vitro kinase assay further demonstrated that Pj-8 suppressed the kinase activity of 3-phosphoinositide-dependent kinase 1 (PDK1). Using xenograft tumor angiogenesis model, Pj-8 markedly eliminated tumor-associated angiogenesis. Taken together, our findings suggest that Pj-8 inhibits VEGF and tumor cells MDA-MB-231-induced angiogenesis, and it may be a potential drug candidate in anticancer therapy. Downregulation of VEGFR2-mediated signaling may contribute to its antiangiogenic actions.     

JAK2信号通路与肿瘤血管新生

JAK2是 JAK 家族的成员之一,JAK2与 STAT 家族的多个成员共同构成多条信号转导通路,如JAK2／STAT3、JAK2／STAT5等。JAK2／STATs 信号通路通过配体和细胞表面的受体结合而诱导受体二聚化,并相互磷酸化,从而激活 JAK。激活了的 JAK2／STAT 信号通路参与了肿瘤的发生、发展、血管新生、侵袭和转移等多个环节。研究表明肿瘤细胞中活化的 JAK2／STATs 信号通路主要是通过上调多种血管生成相关因子如血管内皮生长因子（VEGF）、环氧化酶－2（COX －2）等表达来促进肿瘤血管生成,IFN －α、SHP －1、SOCS通过 JAK2／STATs 通路下调肿瘤细胞促血管生成因子表达,抑制肿瘤血管生成。本文就 JAK2信号通路与肿瘤血管新生作一综述。     

Inhibition of growth factor-induced Ras signaling in vascular endothelial cells and angiogenesis by 3,3'-diindolylmethane

3,3'-Diindolylmethane (DIM), an indole derivative produced on consumption of broccoli and other cruciferous vegetables, has been shown to have multiple anticancer effects in both in vivo and in vitro models. The present study was carried out to clarify the mechanism of DIM's antiangiogenic activity. We found that DIM can inhibit vascular endothelial growth factor (VEGF)-induced cell proliferation and DNA synthesis in human umbilical vascular endothelial cells (HUVECs). Consistent with this inhibition, VEGF-induced extracellular signal-regulated kinase (ERK1/2) phosphorylation was greatly reduced. However, VEGF receptor phosphorylation induced by VEGF was not affected by DIM, indicating that DIM does not exert a direct and specific effect on the tyrosine kinase activity of this receptor. Further studies showed that DIM had a similar inhibitory effect on ERK1/2 phosphorylation induced by a variety of growth factors. Furthermore, Ras-GTP content, which dramatically increased after HUVECs were challenged by either individual growth factors or serum, was reduced by approximately 80% with 25 muM DIM treatment, which in turn resulted in the reduced activities of Raf and MEK, culminating in the drop of ERK1/2 activation. Overexpression of constitutively active GTPase mutant, Ras G12V, in HUVECs reversed the inhibitory effect of DIM on ERK1/2 activation. In a rodent Matrigel plug model, the presence of DIM strongly reduced VEGF-induced neovascularization, indicating that DIM is active in vivo. These data provide evidence that DIM inhibits Ras signaling induced by VEGF and other growth factors, which interferes with its downstream biological effects necessary for angiogenesis.     

Activated STAT3 is a mediator and biomarker of VEGF endothelial activation

STAT3 plays important roles in cell proliferation and survival signaling and is often constitutively activated in transformed cells. In this study, we examined STAT3 activation in endothelial cells (EC) during angiogenic activation and therapeutic angiogenesis inhibition. VEGF stimulation of cultured EC induced STAT3 phosphorylation by a VEGFR2- and Src-dependent mechanism. FGF2 but not PlGF also induced EC STAT3 activation in vitro. Activated STAT3 mediated VEGF induction of EC Bcl-2 and contributed to VEGF protection of EC from apoptosis. In vivo, p-STAT3 was absent by immunohistological staining in the vascular EC of most normal mouse organs but was present in the vessels of mouse and human tumors. Tumor vascular p-STAT3 increased as tumors were induced to overexpress VEGF, indicating that VEGF is an activator of EC p-STAT3 in vivo. Tumor vascular p-STAT3 decreased during angiogenesis inhibition by antagonists of VEGF-VEGFR signaling, VEGF Trap and SU5416, indicating that VEGF contributed to the EC STAT3 activation seen in the tumors prior to treatment and that p-STAT3 may be used to monitor therapy. These studies show that p-STAT3 is a mediator and biomarker of endothelial activation that reports VEGF-VEGFR2 activity and may be useful for studying the pharmacodynamics of targeted angiogenesis inhibitors.     

6-Bromoindirubin-3'-oxime inhibits JAK/STAT3 signaling and induces apoptosis of human melanoma cells

STAT3 is persistently activated and contributes to malignant progression in various cancers. Janus activated kinases (JAK) phosphorylate STAT3 in response to stimulation by cytokines or growth factors. The STAT3 signaling pathway has been validated as a promising target for development of anticancer therapeutics. Small-molecule inhibitors of JAK/STAT3 signaling represent potential molecular-targeted cancer therapeutic agents. In this study, we investigated the role of JAK/STAT3 signaling in 6-bromoindirubin-3'-oxime (6BIO)-mediated growth inhibition of human melanoma cells and assessed 6BIO as a potential anticancer drug candidate. We found that 6BIO is a pan-JAK inhibitor that induces apoptosis of human melanoma cells. 6BIO directly inhibited JAK-family kinase activity, both in vitro and in cancer cells. Apoptosis of human melanoma cells induced by 6BIO was associated with reduced phosphorylation of JAKs and STAT3 in both dose- and time-dependent manners. Consistent with inhibition of STAT3 signaling, expression of the antiapoptotic protein Mcl-1 was downregulated. In contrast to the decreased levels of phosphorylation of JAKs and STAT3, phosphorylation levels of the Akt and mitogen-activated protein kinase (MAPK) signaling proteins were not inhibited in cells treated with 6BIO. Importantly, 6BIO suppressed tumor growth in vivo with low toxicity in a mouse xenograft model of melanoma. Taken together, these results show that 6BIO is a novel pan-JAK inhibitor that can selectively inhibit STAT3 signaling and induces tumor cell apoptosis. Our findings support further development of 6BIO as a potential anticancer therapeutic agent that targets JAK/STAT3 signaling in tumor cells.     

VEGF及其受体KDR在垂体腺瘤中的表达与肿瘤血管形成的关系

 目的　探讨血管内皮生长因子(VEGF) 及其受体( KDR) 的表达与垂体腺瘤血管生成的关系。方法　应用免疫组织化学S2P 法检测58 例人垂体腺瘤中的V E GF 及KD R 的表达,并对血管进行染色、计数。结果　其中54 例有VEGF 的表达(占93. 1 %) ,阳性表达主要位于肿瘤细胞胞膜及胞浆; KD R 在47 例中有阳性表达(占81. 0 %) ,阳性表达位于肿瘤血管内皮细胞、肿瘤细胞胞膜及胞浆。VEGF 和KD R 表达与垂体腺瘤的侵袭性密切相关;V E GF 和KD R 高表达组微血管密度明显高于低表达组( P <0. 01) 。结论　VEGF 以旁分泌、自分泌形式协同KDR 促进垂体腺瘤血管的生成,并与垂体腺瘤的侵袭密切相关。     

Barbigerone, an isoflavone, inhibits tumor angiogenesis and human non-small-cell lung cancer xenografts growth through VEGFR2 signaling pathways

Purpose

We previously reported that barbigerone (BA), an isoflavone isolated from Suberect Spatholobus, exhibited inhibitory effects on proliferation of many cancer cell lines in vitro. The objective of this study was to explore whether BA could effectively suppress tumor angiogenesis and tumor growth.

Methods

Zebrafish model and Matrigel assay were performed to access the anti-angiogenesis effects of BA. A549 and SPC-A1 tumor xenografts in mice models were used to examine the antitumor activity of BA. The anti-angiogenic effects and underlying mechanisms were also investigated using human umbilical vein endothelial cells (HUVECs) and A549 cells.

Results

In zebrafish model, 2.5???mol/L of BA significantly inhibited angiogenesis. Intravenous administration of BA effectively inhibited the tumor growth of A549 and SPC-A1 xenograft models in mice. The anti-angiogenic effect was indicated by CD31 immunohistochemical staining, Matrigel plug assay, and mouse aortic ring assay. BA could inhibit vascular endothelial growth factor (VEGF)-induced cell proliferation, migration, and capillary-like tuber formation of HUVECs in a dose-dependent manner, suggesting that BA inhibited tumorigenesis by targeting angiogenesis. Western blots revealed that BA directly inhibited the phosphorylation of VEGFR2, followed by inhibiting the activations of its downstream protein kinases, including ERK, p38, FAK, AKT, and expression of iNOS, but had no effect on COX2. Additionally, BA could also down-regulate VEGF secretion in A549 cancer cells, which may correlate with the suppression of ERK, AKT activation, indicating that BA inhibits tumor angiogenesis and tumor growth through VEGFR2 signaling pathways.

Conclusions

These findings suggest that BA may be a novel candidate in inhibiting tumor angiogenesis and NSCLC tumor growth.     

Hispidulin, a small flavonoid molecule, suppresses the angiogenesis and growth of human pancreatic cancer by targeting vascular endothelial growth factor receptor 2-mediated PI3K/Akt/mTOR signaling pathway

Hispidulin, an active component from Artemisia vestita, a traditional Tibetan medicinal plant, has been shown to possess anti-inflammatory and anti-oxidative activities. However, the functional role of hispidulin on tumor growth and angiogenesis has not been elucidated. We found that hispidulin significantly inhibited human pancreatic tumor growth in xenograft mice when s.c. treated at a dosage of 20 mg/kg daily, and this effect was accompanied with a potent inhibition on angiogenesis. When examining the cytotoxicity of hispidulin on HUVECs and pancreatic cancer cells in vitro, we found that HUVECs were more susceptible to the treatment, suggesting angiogenesis might be the primary target of hispidulin. Our results further showed that hispidulin inhibited vascular endothelial growth factor (VEGF)-induced cell migration, invasion, and capillary-like structure formation of HUVECs in a dose-dependent manner. In ex vivo and in vivo angiogenesis assays, we showed that hispidulin suppressed VEGF-induced microvessel sprouting of rat aortic rings and corneal neovascularization in C57/BL6 mice. To understand the underlying molecular basis, we next examined the effects of hispidulin on different molecular components in treated HUVECs, and found that hispidulin suppressed the VEGF-triggered activation of VEGF receptor 2, PI3K, Akt, mTOR, and ribosomal protein S6 kinase, but had little effect on focal adhesion kinase or extracellular signal-regulated kinase at an effective concentration. Taken together, our results indicate that hispidulin targets the VEGF receptor 2-mediated PI3K/Akt/mTOR signaling pathway in endothelial cells, leading to the suppression of pancreatic tumor growth and angiogenesis.     

Blockade of her2/neu decreases VEGF expression but does not alter HIF-1 distribution in experimental Wilms tumor

Her2/neu regulates angiogenesis in human breast cancer, in part by stabilizing hypoxia-inducible factor 1alpha (HIF-1alpha), causing accumulation of the HIF-1 heterodimer and thus increasing expression of the proangiogenic cytokine VEGF. Her2/neu has recently been shown to be overexpressed in a subset of Wilms tumors. Using her2/neu (+) and her2/neu (-) Wilms tumor cell lines, we tested the effect of blocking anti-her2/neu antibody in vitro and in vivo. Blocking antibody did not alter VEGF expression in vitro, but decreased expression of VEGF in her2/neu (+) Wilms tumor xenografts. Tumor suppression was less marked than in parallel experiments using agents directly blocking VEGF. HIF-1alpha immunostaining was not altered in her2/neu (+) xenografts exposed to blocking antibody. These results suggest that her2/neu contributes to Wilms tumor angiogenesis in vivo by regulating VEGF, but other processes may act to rescue HIF-1alpha and thus to support tumor growth in this system.     

Antitumor activities of synthetic and natural stilbenes through antiangiogenic action

We reported that the antitumor and antimetastatic actions of resveratrol might be due to the inhibition of tumor‐induced angiogenesis. To search for anticancer agents with stronger activity than resveratrol, we examined the antiangiogenic effects of 21 synthetic and/or natural stilbenes. Among these 21 stilbenes, 2,3‐, 3,4‐, and 4,4′‐dihydroxystilbene inhibited the pro‐matrix metalloproteinase (pro‐MMP)–9 production in colon 26 cells at 5–25 µM, vascular endothelial growth factor (VEGF)–induced human umbilical vein endothelial cell (HUVEC) migration at 10 and 25 µM, and VEGF‐induced angiogenesis at 5–50 µM. Resvertarol inhibited the pro‐MMP‐9 production and VEGF‐induced angiogenesis at 25 or 50 µM. Thus, the inhibition of pro‐MMP‐9 production in colon 26 cells and VEGF‐induced angiogenesis by three dihydroxystilbenes were greater than those of resveratrol. The three dihydroxystilbenes (8 mg/kg, intraperitoneal injection) inhibited the tumor‐induced neovascularization in colon 26–packed chamber‐bearing mice and the tumor growth in colon 26–bearing mice. Furthermore, the three dihydroxystilbenes inhibited VEGF‐induced VEGFR‐2 phosphorylation. On the other hand, the three dihydroxystilbenes had no effect on VEGFR‐1 and‐2 expression, and VEGF‐induced VEGFR‐1 phosphorylation in HUVECs. These findings suggest that the inhibition of tumor‐induced neovascularization by these three dihydroxystilbenes may be due to the inhibition of VEGF‐induced endothelial cell migration and VEGF‐induced angiogenesis through the inhibition of VEGF‐induced VEGFR‐2 phosphorylation in endothelial cells and pro‐MMP‐9 expression in colon 26 cells. (Cancer Sci 2008; 99: 2083–2096)