Cancer Cell-induced Angiogenesis Research Articles

Suppression of endothelial miR-22 mediates non-small cell lung cancer cell-induced angiogenesis

MicroRNAs (miRNAs) expressed in endothelial cells (ECs) are powerful regulators of angiogenesis, which is essential for tumor growth and metastasis. Here, we demonstrated that miR-22 is preferentially and highly expressed in ECs, while its endothelial level is significantly downregulated in human non-small cell lung cancer (NSCLC) tissues when compared to matched nontumor lung tissues. This reduction of endothelial miR-22 is possibly induced by NSCLC cell-secreted interleukin-1β and subsequently activated transcription factor nuclear factor-κB. Endothelial miR-22 functions as a potent angiogenesis inhibitor that inhibits all of the key angiogenic activities of ECs and consequently NSCLC growth through directly targeting sirtuin 1 and fibroblast growth factor receptor 1 in ECs, leading to inactivation of AKT/mammalian target of rapamycin signaling. These findings provide insight into the molecular mechanisms of NSCLC angiogenesis and indicate that endothelial miR-22 represents a potential target for the future antiangiogenic treatment of NSCLC.

Inhibiting Endothelial Cell Function in Normal and Tumor Angiogenesis Using BMP Type I Receptor Macrocyclic Kinase Inhibitors.

Simple SummaryAnti-angiogenesis agents have shown anti-cancer activity by preventing blood vessel ingrowth, thereby limiting tumour growth and metastasis. Although these molecules lead to prolonged overall survival of cancer patients, therapy resistance is easily acquired. Therefore, novel inhibitors against other signaling pathways mediating angiogenesis are needed to achieve more efficient and sustainable targeting of the angiogenesis process. Here, we synthesized and identified two compounds belonging to a new class of small molecules termed macrocyclics that selectively inhibit bone morphogenetic protein receptor kinase activity. One compound also inhibits vascular endothelial growth factor-induced signalling. Treatment studies using in vitro cultured cells and zebrafish embryos revealed that both compounds impaired endothelial cell function and decreased normal and tumour-induced angiogenesis. Both compounds might provide a steppingstone for the development of novel-angiogenesis therapeutic agents.Angiogenesis, i.e., the formation of new blood vessels from pre-existing endothelial cell (EC)-lined vessels, is critical for tissue development and also contributes to neovascularization-related diseases, such as cancer. Vascular endothelial growth factor (VEGF) and bone morphogenetic proteins (BMPs) are among many secreted cytokines that regulate EC function. While several pharmacological anti-angiogenic agents have reached the clinic, further improvement is needed to increase clinical efficacy and to overcome acquired therapy resistance. More insights into the functional consequences of targeting specific pathways that modulate blood vessel formation may lead to new therapeutic approaches. Here, we synthesized and identified two macrocyclic small molecular compounds termed OD16 and OD29 that inhibit BMP type I receptor (BMPRI)-induced SMAD1/5 phosphorylation and downstream gene expression in ECs. Of note, OD16 and OD29 demonstrated higher specificity against BMPRI activin receptor-like kinase 1/2 (ALK1/2) than the commonly used small molecule BMPRI kinase inhibitor LDN-193189. OD29, but not OD16, also potently inhibited VEGF-induced extracellular regulated kinase MAP kinase phosphorylation in ECs. In vitro, OD16 and OD29 exerted strong inhibition of BMP9 and VEGF-induced ECs migration, invasion and cord formation. Using Tg (fli:EGFP) zebrafish embryos, we found that OD16 and OD29 potently antagonized dorsal longitudinal anastomotic vessel (DLAV), intra segmental vessel (ISV), and subintestinal vessel (SIV) formation during embryonic development. Moreover, the MDA-MB-231 breast cancer cell-induced tumor angiogenesis in zebrafish embryos was significantly decreased by OD16 and OD29. Both macrocyclic compounds might provide a steppingstone for the development of novel anti-angiogenesis therapeutic agents.

Novel Nargenicin A1 Analog Inhibits Angiogenesis by Downregulating the Endothelial VEGF/VEGFR2 Signaling and Tumoral HIF-1α/VEGF Pathway.

Targeting angiogenesis is an attractive strategy for the treatment of angiogenesis-related diseases, including cancer. We previously identified 23-demethyl 8,13-deoxynargenicin (compound 9) as a novel nargenicin A1 analog with potential anticancer activity. In this study, we investigated the antiangiogenic activity and mode of action of compound 9. This compound was found to effectively inhibit in vitro angiogenic characteristics, including the proliferation, invasion, capillary tube formation, and adhesion of human umbilical vein endothelial cells (HUVECs) stimulated by vascular endothelial growth factor (VEGF). Furthermore, compound 9 suppressed the neovascularization of the chorioallantoic membrane of growing chick embryos in vivo. Notably, the antiangiogenic properties of compound 9 were related to the downregulation of VEGF/VEGFR2-mediated downstream signaling pathways, as well as matrix metalloproteinase (MMP)-2 and MMP-9 expression in HUVECs. In addition, compound 9 was found to decrease the in vitro AGS gastric cancer cell-induced angiogenesis of HUVECs by blocking hypoxia-inducible factor-1α (HIF-1α) and VEGF expression in AGS cells. Collectively, our findings demonstrate for the first time that compound 9 is a promising antiangiogenic agent targeting both VEGF/VEGFR2 signaling in ECs and HIF-1α/VEGF pathway in tumor cells.

Murrangatin suppresses angiogenesis induced by tumor cell-derived media and inhibits AKT activation in zebrafish and endothelial cells.

IntroductionLung cancer is a major cancer type and a leading cause of cancer-related death. Angiogenesis plays a crucial role in lung cancer pathogenesis and its inhibition is beneficial to patients.Materials and methodsMurrangatin, a natural product, can inhibit the proliferation of lung cancer cells, so herein we investigated its anti-angiogenic effects in transgenic zebrafish TG (fli1: EGFP) and in lung cancer cell-induced angiogenesis in human umbilical vein endothelial cells.ResultsWe found that murrangatin strongly inhibited the growth of subintestinal vessels in zebrafish embryos and tumor conditioned media-induced angiogenic phenotypes including cell proliferation, cell invasion, cell migration, and tube formation. Additionally, murrangatin greatly attenuated conditioned medium-induced AKT phosphorylation, but not extracellular signal-regulated kinase 1/2 phosphorylation.Discussion and conclusionThese findings indicate that murrangatin can inhibit tumor-induced angiogensis, at least in part through the regulation of AKT signaling pathways. Murrangatin may, therefore, be a potential candidate for the development of new anti-lung-cancer drugs.

CAMP regulated EPAC1 supports microvascular density, angiogenic and metastatic properties in a model of triple negative breast cancer

Breast cancer is a leading cause of cancer-related mortality in women. Triple-negative breast cancer (TNBC; HER2-, ER-/PR-) is an aggressive subtype prone to drug resistance and metastasis, which is characterized by high intratumor microvascular density (iMVD) resulting from angiogenesis. However, the mechanisms contributing to the aggressive phenotypes of TNBC remain elusive. We recently reported that down-regulation of exchange factor directly activated by cyclic AMP (cAMP), also known as EPAC1, leads to a reduction in metastatic properties including proliferation and cell migration in TNBC cell lines. Here, we report that EPAC1 supports TNBC-induced angiogenesis, tumor cell migration and invasiveness as well as pro-metastatic phenotypes in endothelial cells induced through the tumor secretome. Using an approach that integrates proteomics with bioinformatics and gene ontologies, we elucidate that EPAC1 supports a tumor-secreted network of angiogenic, cell adhesion and cell migratory pathways. Using confocal microscopy, we show that signaling molecules involved in focal adhesion, including Paxillin and MENA, are down-regulated in the absence of EPAC1, and electric cell substrate impedance sensing technique confirmed a role for EPAC1 on TNBC-induced endothelial cell permeability. Finally, to provide a translational bridge, we studied iMVD and therapy response using a primary human tumor explant assay, CANscriptTM, which suggests a link between therapy-modulated neovascularization and drug sensitivity. These data provide mechanistic insight into the role of EPAC1 in regulating the tumor microenvironment, iMVD and cancer cell-induced angiogenesis, a dynamic mechanism under drug pressure that may associate to treatment failure.

Platelet releasate promotes breast cancer growth and angiogenesis via VEGF\u2013integrin cooperative signalling

Background:Selective platelet release of pro- or anti-angiogenic factors distinctly regulated angiogenesis. We hypothesised that selective release of platelet angiogenic factors could differently regulate tumour growth.Methods:Breast cancer cell proliferation, cancer cell-induced endothelial tube formation in vitro, and tumour growth in vivo were studied in the presence of protease-activated receptor 1-stimulated platelet releasate (PAR1-PR; rich in pro-angiogenic factors) or PAR4-PR (rich in anti-angiogenic factors).Results:The PAR1-PR and PAR4-PR supplementation (10%) similarly enhanced cell proliferation of MCF-7 and MDA-MB-231 breast cancer cells. The cancer cells triggered capillary-like tube formation of endothelial cells that was further enhanced by pro-angiogenic factor-rich PAR1-PR. The VEGF, but not SDF-1α, receptor blockade abolished PAR1-PR/PAR4-PR-enhanced cancer cell proliferation. Integrin blockade by RGDS had identical effects as VEGF inhibition. The Src and ERK inhibition diminished, whereas PI3K and PKC blockade abolished platelet releasate-enhanced cancer cell proliferation. Using a model of subcutaneous implantation of MDA-MB-231 cells in nude mice, PAR1-PR enhanced tumour growth more markedly than PAR4-PR, and seemed to achieve the exaggeration by promoting more profound tumour angiogenesis.Conclusions:Platelet releasate increases breast cancer cell proliferation through VEGF–integrin cooperative signalling. Pro-angiogenic factor-rich platelet releasate enhances cancer cell-induced angiogenesis more markedly, and thus exaggerates tumour growth in vivo.

1-methylnicotinamide and its structural analog 1,4-dimethylpyridine for the prevention of cancer metastasis.

Background1-methylnicotinamide (1-MNA), an endogenous metabolite of nicotinamide, has recently gained interest due to its anti-inflammatory and anti-thrombotic activities linked to the COX-2/PGI2 pathway. Given the previously reported anti-metastatic activity of prostacyclin (PGI2), we aimed to assess the effects of 1-MNA and its structurally related analog, 1,4-dimethylpyridine (1,4-DMP), in the prevention of cancer metastasis.MethodsAll the studies on the anti-tumor and anti-metastatic activity of 1-MNA and 1,4-DMP were conducted using the model of murine mammary gland cancer (4T1) transplanted either orthotopically or intravenously into female BALB/c mouse. Additionally, the effect of the investigated molecules on cancer cell-induced angiogenesis was estimated using the matrigel plug assay utilizing 4T1 cells as a source of pro-angiogenic factors.ResultsNeither 1-MNA nor 1,4-DMP, when given in a monotherapy of metastatic cancer, influenced the growth of 4T1 primary tumors transplanted orthotopically; however, both compounds tended to inhibit 4T1 metastases formation in lungs of mice that were orthotopically or intravenously inoculated with 4T1 or 4T1-luc2-tdTomato cells, respectively. Additionally, while 1-MNA enhanced tumor vasculature formation and markedly increased PGI2 generation, 1,4-DMP did not have such an effect. The anti-metastatic activity of 1-MNA and 1,4-DMP was further confirmed when both agents were applied with a cytostatic drug in a combined treatment of 4T1 murine mammary gland cancer what resulted in up to 80 % diminution of lung metastases formation.ConclusionsThe results of the studies presented below indicate that 1-MNA and its structural analog 1,4-DMP prevent metastasis and might be beneficially implemented into the treatment of metastatic breast cancer to ensure a comprehensive strategy of metastasis control.Electronic supplementary materialThe online version of this article (doi:10.1186/s13046-016-0389-9) contains supplementary material, which is available to authorized users.

Effect of AURKA Gene Expression Knockdown on Angiogenesis and Tumorigenesis of Human Ovarian Cancer Cell Lines.

Ovarian cancer is one of the most common malignant gynecological cancers. Higher expression of AURKA has been found in immortalized human ovarian epithelial cells in previous studies, implying the relationship between AURKA and ovarian cancer pathogenesis. We investigated the effect of AURKA on angiogenesis and tumorigenesis of human ovarian cancer cells. Firstly, the expression of AURKA in HO8910 and SKOV3 ovarian cancer cell lines was knocked down using a vector expressing a short hairpin small interfering RNA (shRNA). Next, the effect of knockdown of AURKA on cell angiogenesis, proliferation, migration, and invasion was determined by microtubule formation assay, proliferation assay, transwell migration, and invasion assays. In addition, the effect of AURKA knockdown on angiogenesis and tumorigenesis was also determined in a chicken chorioallantoic membrane (CAM) model and in nude mice. The results of the microtubule formation assay indicated that knockdown of AURKA significantly inhibited ovarian cancer cell-induced angiogenesis of endothelial cells compared to its control (P < 0.001). Knockdown of AURKA also significantly inhibited cell proliferation, migration, and invasion of HO8910 and SKOV3 cells in vitro. Furthermore, the Matrigel plug assay showed that knockdown of AURKA significantly repressed ovarian cancer cell-induced angiogenesis in nude mice (P < 0.05), and the CAMs model also showed that AURKA knockdown significantly attenuated the angiogenesis (P < 0.001) and tumorigenesis (P < 0.001) of HO8910 cells compared to the control. Finally, the tumorigenicity assay in vivo further indicated that AURKA shRNA reduced tumorigenesis in nude mice inoculated with ovarian cancer cells (P < 0.001). These results suggest the potential role of AURKA in angiogenesis and tumorigenesis of ovarian cancer, which may provide a potential therapeutic target for the disease.

Ionizing radiation modulates human macrophages towards a pro-inflammatory phenotype preserving their pro-invasive and pro-angiogenic capacities.

In order to improve the efficacy of conventional radiotherapy, attention has been paid to immune cells, which not only modulate cancer cell response to therapy but are also highly recruited to tumours after irradiation. Particularly, the effect of ionizing radiation on macrophages, using therapeutically relevant doses, is not well understood. To evaluate how radiotherapy affects macrophage behaviour and macrophage-mediated cancer cell activity, human monocyte derived-macrophages were subjected, for a week, to cumulative ionizing radiation doses, as used during cancer treatment (2 Gy/fraction/day). Irradiated macrophages remained viable and metabolically active, despite DNA damage. NF-kappaB transcription activation and increased Bcl-xL expression evidenced the promotion of pro-survival activity. A significant increase of pro-inflammatory macrophage markers CD80, CD86 and HLA-DR, but not CCR7, TNF and IL1B was observed after 10 Gy cumulative doses, while anti-inflammatory markers CD163, MRC1, VCAN and IL-10 expression decreased, suggesting the modulation towards a more pro-inflammatory phenotype. Moreover, ionizing radiation induced macrophage morphological alterations and increased their phagocytic rate, without affecting matrix metalloproteases (MMP)2 and MMP9 activity. Importantly, irradiated macrophages promoted cancer cell-invasion and cancer cell-induced angiogenesis. Our work highlights macrophage ability to sustain cancer cell activities as a major concern that needs to be addressed to improve radiotherapy efficacy.

Interactions of tumour-derived micro(nano)vesicles with human gastric cancer cells.

BackgroundTumour cells release membrane micro(nano)fragments called tumour-derived microvesicles (TMV) that are believed to play an important role in cancer progression. TMV suppress/modify antitumour response of the host, but there is also some evidence for their direct interaction with cancer cells. In cancer patients TMV are present in body fluid and tumour microenvironment. The present study aimed at characterization of whole types/subpopulations, but not only exosomes, of TMV from newly established gastric cancer cell line (called GC1415) and to define their interactions with autologous cells.MethodsTMV were isolated from cell cultures supernatants by centrifugation at 50,000×g and their phenotype was determined by flow cytometry. The size of TMV was analysed by dynamic light scattering and nanoparticle tracking analysis, while morphology by transmission electron microscopy and atomic force microscopy. Interactions of TMV with cancer cells were visualized using fluorescence-activated cell sorter, confocal and atomic force microscopy, biological effects by xenografts in NOD SCID mice.ResultsIsolated TMV showed expression of CD44H, CD44v6 (hyaluronian receptors), CCR6 (chemokine receptor) and HER-2/neu molecules, exhibited different shapes and sizes (range 60–900 nm, highest frequency of particles with size range of 80–120 nm). TMV attached to autologous cancer cells within 2 h and then were internalized by them at 24 h. CD44H, CD44v6 and CCR6 molecules may play a role in attachment of TMV to cancer cells, while HER-2 associated with CD24 be involved in promoting cancer cells growth. Pre-exposure of cancer cells to TMV resulted in enhancement of tumour growth and cancer cell-induced angiogenesis in NOD SCID mice model.ConclusionsTMV interact directly with cancer cells serving as macro-messengers and molecular cargo transfer between gastric cancer cells resulting in enhancement of tumour growth. TMV should be considered in future as target of anticancer therapy.

Matrix metalloproteases as maestros for the dual role of LPS- and IL-10-stimulated macrophages in cancer cell behaviour.

BackgroundThe interactions established between macrophages and cancer cells are largely dependent on instructions from the tumour microenvironment. Macrophages may differentiate into populations with distinct inflammatory profiles, but knowledge on their role on cancer cell activities is still very scarce. In this work, we investigated the influence of pro-inflammatory (LPS-stimulated) and anti-inflammatory (IL-10-stimulated) macrophages on gastric and colorectal cancer cell invasion, motility/migration, angiogenesis and proteolysis, and the associated molecular mechanisms.MethodsFollowing exposure of gastric and colon cancer cell lines to LPS- and IL-10-stimulated human macrophages, either by indirect contact or conditioned media, we analyzed the effect of the different macrophage populations on cancer cell invasion, migration, motility and phosphorylation status of EGFR and several interacting partners. Cancer-cell induced angiogenesis upon the influence of conditioned media from both macrophage populations was assessed using the chick embryo chorioallantoic membrane assay. MMP activities were evaluated by gelatin zymograhy.ResultsOur results show that IL-10-stimulated macrophages are more efficient in promoting in vitro cancer cell invasion and migration. In addition, soluble factors produced by these macrophages enhanced in vivo cancer cell-induced angiogenesis, as opposed to their LPS-stimulated counterparts. We further demonstrate that differences in the ability of these macrophage populations to stimulate invasion or angiogenesis cannot be explained by the EGFR-mediated signalling, since both LPS- and IL-10-stimulated macrophages similarly induce the phosphorylation of cancer cell EGFR, c-Src, Akt, ERK1/2, and p38. Interestingly, both populations exert distinct proteolytic activities, being the IL-10-stimulated macrophages the most efficient in inducing matrix metalloprotease (MMP)-2 and MMP-9 activities. Using a broad-spectrum MMP inhibitor, we demonstrated that proteolysis was essential for macrophage-mediated cancer cell invasion and angiogenesis.ConclusionsWe propose that IL-10- and LPS-stimulated macrophages distinctly modulate gastric and colorectal cancer cell behaviour, as result of distinct proteolytic profiles that impact cell invasion and angiogenesis.

Paris saponin II inhibits human ovarian cancer cell-induced angiogenesis by modulating NF-κB signaling.

The clinical applications of Rhizomaparidis in traditional Chinese medicine are well known. However, the therapeutic potential of Rhizomaparidis and its active component such as Paris saponinI (polyphyllin D) and Paris saponinII (PSII) (formosaninC) in cancer treatments have not yet been fully explored. Recent studies have demonstrated that PSII and chemoagents exhibit comparable inhibitory affects against human ovarian cancer cell growth. Since NF-κB, a ubiquitous transcription factor that plays an important role in cancer biology, is often associated with gynecological cancers, in the present study, we evaluated the possibility that PSII modulates NF-κB activity and VEGF-mediated angiogenesis and elucidated the molecular mechanisms underlying such effects. We assessed the effects of PSII on NF-κB activity in SKOV3 tumor cells and on tumor cell induced-angiogenesis using standardized angiogenesis invitro, exvivo and invivo assays, western blot analysis and kinase assay. We also assessed the effect of the super-engineered repressor of IĸBα and its effect, in combination with PSII treatment on tumor growth and angiogenesis in xenograft athymic mouse models of ovarian cancer (SKOV3 and SKOV3/mutant IĸBα cells) using color Doppler ultrasound and traditional immunohistochemistry. We showed that PSII suppressed NF-κB activation as a result of the reduction in IKKβ kinase activity on its substrate IκBα and the expression of IKKβ. Compromising NF-κB activation reduced the expression of NF-κB-downstream targets such as VEGF, Bcl-2 and Bcl-xL. Such inhibitory effects at molecular levels appear to compromise tumor growth and angiogenesis. Most importantly, the combination of PSII treatment and constitutive repression of IĸBα activity exhibited marked inhibitory effects against human ovarian cancer cell growth in a xenograft mouse model of ovarian cancer. For the first time, we provide evidence showing that PSII potently inhibits angiogenesis and the growth of human ovarian cancer by suppressing NF-κB signaling.

Effects of tetrahydrocurcumin on hypoxia-inducible factor-1α and vascular endothelial growth factor expression in cervical cancer cell-induced angiogenesis in nude mice.

Tetrahydrocurcumin (THC), one of the important in vivo metabolites of curcumin, inhibits tumor angiogenesis. Its effects on angiogenesis in cervical cancer- (CaSki-) implanted nude mice and its mechanisms on hypoxia-inducible factor-1α and vascular endothelial growth factor expression were investigated. Female BALB/c nude mice were divided into control (CON) and CaSki-implanted groups (CaSki group). One month after the injection with cervical cancer cells, mice were orally administered vehicle or 100, 300, and 500 mg/kg of THC daily for 30 consecutive days. The microvascular density (MVD) was evaluated using the CD31 expression. VEGF, VEGFR-2, and HIF-1α expression were also detected by immunohistochemistry. The MVD in CaSki + vehicle group was significantly increased compared to the CON + vehicle group. Interestingly, when treated with THC at all doses, the CaSki group showed a significant smaller number of the MVD. The CaSki + vehicle group also showed significantly increased VEGF, VEGFR-2, and HIF-1α expressions, but they were downregulated when mice were treated with THC at all doses. THC demonstrated an inhibitory effect against tumor angiogenesis in CaSki-implanted nude mice model. This effect is likely to be mediated by the downregulation of HIF-1-α, VEGF expression, and its receptor. THC could be developed into a promising agent for cancer therapy in the future.

Piperine, a dietary phytochemical, inhibits angiogenesis

Angiogenesis plays an important role in tumor progression. Piperine, a major alkaloid constituent of black pepper, has diverse physiological actions including killing of cancer cells; however, the effect of piperine on angiogenesis is not known. Here we show that piperine inhibited the proliferation and G1/S transition of human umbilical vein endothelial cells (HUVECs) without causing cell death. Piperine also inhibited HUVEC migration and tubule formation in vitro, as well as collagen-induced angiogenic activity by rat aorta explants and breast cancer cell-induced angiogenesis in chick embryos. Although piperine binds to and activates the cation channel transient receptor potential vanilloid 1 (TRPV1), its effects on endothelial cells did not involve TRPV1 since the antiproliferative effect of piperine was not affected by TRPV1-selective antagonists, nor did HUVECs express detectable TRPV1 mRNA. Importantly, piperine inhibited phosphorylation of Ser 473 and Thr 308 residues of Akt (protein kinase B), which is a key regulator of endothelial cell function and angiogenesis. Consistent with Akt inhibition as the basis of piperine's action on HUVECs, inhibition of the phosphoinositide-3 kinase/Akt signaling pathway with LY-294002 also inhibited HUVEC proliferation and collagen-induced angiogenesis. Taken together, these data support the further investigation of piperine as an angiogenesis inhibitor for use in cancer treatment.

FP3: A Novel VEGF Blocker with Anti-Angiogenic and Anti-Tumor Effects

Vascular endothelial growth fac-tor (VEGF) serves as a logical target for antiangiogenic cancer therapy. This study is to investigate the inhibitory effects of FP3, a novel VEGF blocker, on angiogenesis in vitro and in vivo as well as anti-tumor effects ona liver cancer xenograft model in vivo. The inhibitory effects of FP3 on angiogenesis were assessed by using human umbilical vein endothelial cells(HUVECs) in vitro and the chick embryo chorioallantoialc membrane (CAM) in viva. The inhibitory effect of FP3 on tumor growth in viva were evaluated in a human liver cancer cell line Hep-3B xenograft model in nude mice with the methods of tumor growth regression as-say. In experiments with HUVECs, FP3 inhibit-ed cell survival and tube formation. In CAM assay, FP3 suppressed MCF-7 human breast cancer cell-induced angiogenesis. In tumor growth regression assay, FP3 significantly blocked the growth of Hep-3B tumor cellin subcutaneous tumor xenograft model in nude mice. FP3 has excellent inhibitory effects on angiogenesis both in vitro and in viva and antitumor effect on liver cancer xenograft model; therefore, it might be used as an effective antiangiogenic agent in treatment of liver cancer.

Acacetin inhibits VEGF expression, tumor angiogenesis and growth through AKT/HIF-1α pathway

Acacetin (5,7-dihydroxy-4′-methoxyflavone) is a flavone compound, some of which have anti-cancerous effects. Vascular endothelial growth factor (VEGF) plays an important role in angiogenesis and tumor growth. In this study, we found that acacetin decreased the steady level of VEGF mRNA level and inhibited VEGF transcriptional activation. To further determine the potential mechanism of acacetin in inhibiting VEGF expression, we showed that acacetin inhibited HIF-1α expression and AKT activation. Over-expression of HIF-1α or AKT restored acacetin-decreasing VEGF transcriptional activation, indicating that AKT and HIF-1 are the essential downstream targets of acacetin for inhibiting VEGF expression in the cells. Moreover, acacetin significantly inhibited ovarian cancer cell-induced angiogenesis and tumor growth in vivo through inhibiting HIF-1α and VEGF expression. Acacetin did not change HIF-1α mRNA level, but inhibited HIF-1α protein level through increasing its degradation and decreasing its stability. These results indicate that acacetin may be a useful natural compound for ovarian cancer prevention and treatment.

Novel hexahydrocannabinol analogs as potential anti-cancer agents inhibit cell proliferation and tumor angiogenesis

Both natural and synthetic cannabinoids have been shown to suppress the growth of tumor cells in culture and in animal models by affecting key signaling pathways including angiogenesis, a pivotal step in tumor growth, invasion, and metastasis. In our search for cannabinoid-like anticancer agents devoid of psychoactive side effects, we synthesized and evaluated the anti-angiogenic effects of a novel series of hexahydrocannabinol analogs. Among these, two analogs LYR-7 [(9 S)-3,6,6,9-tetramethyl-6a,7,8,9,10,10a-hexahydro-6 H-benzo[c]chromen-1-ol] and LYR-8 [(1-((9 S)-1-hydroxy-6,6,9-trimethyl-6a,7,8,9,10,10a-hexahydro-6 H-benzo[c]chromen-2-yl)ethanone)] were selected based on their anti-angiogenic activity and lack of binding affinity for cannabinoid receptors. Both LYR-7 and LYR-8 inhibited VEGF-induced proliferation, migration, and capillary-like tube formation of HUVECs in a concentration-dependent manner. The inhibitory effect of the compounds on cell proliferation was more selective in endothelial cells than in breast cancer cells (MCF-7 and tamoxifen-resistant MCF-7). We also noted effective inhibition of VEGF-induced new blood vessel formation by the compounds in the in vivo chick chorioallantoic membrane (CAM) assay. Furthermore, both LYR analogs potently inhibited VEGF production and NF-κB transcriptional activity in cancer cells. Additionally, LYR-7 or LYR-8 strongly inhibited breast cancer cell-induced angiogenesis and tumor growth. Together, these results suggest that novel synthetic hexahydrocannabinol analogs, LYR-7 and LYR-8, inhibit tumor growth by targeting VEGF-mediated angiogenesis signaling in endothelial cells and suppressing VEGF production and cancer cell growth.

P16 Modulates VEGF Expression via Its Interaction With HIF-1α in Breast Cancer Cells

ABSTRACTThe degree of tumor progression (such as growth, angiogenesis, and metastasis) directly correlates with the expression of vascular endothelial growth factor (VEGF), but inversely correlates with the expression of tumor-suppressor gene p16, therefore we examined whether the restoration of p16 in breast cancer cells would modulate VEGF expression. Adenoviralmediated p16 expression downregulated VEGF gene expression in breast cancer cells, and inhibited breast cancer cell-induced angiogenesis by a dorsal air sac model in mice. Moreover, p16 appears to form a complex with HIF-1a, the transcription factor for the VEGF gene promoter. Taken together, the binding between p16 and HIF-1a protein may alter HIF-1a's ability to transactivate VEGF expression.

LIMK1 and LIMK2 Are Important for Metastatic Behavior and Tumor Cell-Induced Angiogenesis of Pancreatic Cancer Cells

The two LIM kinases (LIMKs) LIMK1 and LIMK2 are members of the PDZ/LIM family. These serine/threonine protein kinases are involved in actin cytoskeleton reorganization through phosphorylation and inactivation of ADF/cofilin. Different subcellular localizations of LIMK1 and LIMK2 suggest different functions. LIMK1 is implicated in microtubule disassembly in endothelial- and cancer cells, whereas LIMK2 plays a role in cell cycle progression. To compare the role of the two LIMKs in cancer-related processes, we used a cell-based in vitro migration assay, as well as two zebrafish xenograft assays. We analyzed here the metastatic behavior and tumor cell-induced neovascularization of pancreatic cancer cells in which both LIMK genes were silenced by siRNAs. Both LIMK1 and LIMK2 single knock down led to a reduction of invasion and metastatic behavior in the zebrafish xenograft metastasis assay. Interestingly, the double knock down completely blocked invasion and formation of micrometastasis in vivo. Moreover, in the zebrafish xenograft angiogenesis assay, we observed a reduction of pancreatic cancer cell-induced angiogenesis for both the LIMK1 and LIMK2 knockdowns. Our results demonstrate similar functions for the two LIMKs in pancreatic cancer cells and suggest an important role for both LIMK1 and LIMK2 in tumor progression and metastasis formation.

A Paradox of Cadmium: A Carcinogen That Impairs the Capability of Human Breast Cancer Cells To Induce Angiogenesis

Cadmium, a highly persistent heavy metal, has been categorized as a human carcinogen. Even though it is known that cadmium acts as estrogens in breast cancer cells, several studies failed to demonstrate whether cadmium is a causal factor for breast cancer. The lack of a strong association between cadmium and breast cancer could be found in the antiangiogenic properties of this heavy metal, which might counteract its carcinogenic properties in the progression of breast cancer. In this study, we exposed estrogen-responsive breast cancer cells to subtoxic levels of cadmium, and we evaluated their angiogenic potential using the chick embryo chorioallantoic membrane assay. Exposure of breast cancer cells to subtoxic levels of cadmium significantly inhibited the angiogenic potential of the breast cancer cell line, suggesting the possibility that cadmium might negatively regulate the production of proangiogenic factors in breast cancer cells. Our results suggest that cadmium might exert a paradoxical effect in breast cancer: on the one hand, it could promote carcinogenesis, and, on the other hand, it could delay the onset of tumors by inhibiting breast cancer cell-induced angiogenesis.