Hypoxia-induced downregulation of microRNA-186-5p in endothelial cells promotes non-small cell lung cancer angiogenesis by upregulating protein kinase C alpha.

The tumor microenvironment stimulates the angiogenic activity of endothelial cells (ECs) to facilitate tumor vascularization, growth, and metastasis. The involvement of microRNA-186-5p (miR-186) in regulating the aberrant activity of tumor-associated ECs has so far not been clarified. In the present study, we demonstrated that miR-186 is significantly downregulated in ECs microdissected from human non-small cell lung cancer (NSCLC) tissues compared with matched non-malignant lung tissues. In vitro analyses of primary human dermal microvascular ECs (HDMECs) exposed to different stimuli indicated that this miR-186 downregulation is triggered by hypoxia via activation of hypoxia-inducible factor 1 alpha (HIF1α). Transfection of HDMECs with miR-186 mimic (miR-186m) significantly inhibited their proliferation, migration, tube formation, and spheroid sprouting. In contrast, miR-186 inhibitor (miR-186i) exerted pro-angiogenic effects. In vivo, endothelial miR-186 overexpression inhibited the vascularization of Matrigel plugs and the initial growth of tumors composed of NSCLC cells (NCI-H460) and HDMECs. Mechanistic analyses revealed that the gene encoding for protein kinase C alpha (PKCα) is a bona fide target of miR-186. Activation of this kinase significantly reversed the miR-186m-repressed angiogenic activity of HDMECs. These findings indicate that downregulation of miR-186 in ECs mediates hypoxia-stimulated NSCLC angiogenesis by upregulating PKCα.

Brassinin Promotes the Degradation of Tie2 and FGFR1 in Endothelial Cells and Inhibits Triple-Negative Breast Cancer Angiogenesis.

Brassinin, a phytoalexin derived from cruciferous vegetables, has been reported to exhibit anti-cancer activity in multiple cancer types. However, its effects on triple-negative breast cancer (TNBC) development and the underlying mechanisms have not been elucidated so far. In this study, we demonstrated in vitro that brassinin preferentially reduces the viability of endothelial cells (ECs) when compared to other cell types of the tumor microenvironment, including TNBC cells, pericytes, and fibroblasts. Moreover, brassinin at non-cytotoxic doses significantly suppressed the proliferation, migration, tube formation, and spheroid sprouting of ECs. It also efficiently inhibited angiogenesis in an ex-vivo aortic ring assay and an in-vivo Matrigel plug assay. Daily intraperitoneal injection of brassinin significantly reduced tumor size, microvessel density, as well as the perfusion of tumor microvessels in a dorsal skinfold chamber model of TNBC. Mechanistic analyses showed that brassinin selectively stimulates the degradation of Tie2 and fibroblast growth factor receptor 1 in ECs, leading to the down-regulation of the AKT and extracellular signal-regulated kinase pathways. These findings demonstrate a preferential and potent anti-angiogenic activity of brassinin, which may be the main mechanism of its anti-tumor action. Accordingly, this phytochemical represents a promising candidate for the future anti-angiogenic treatment of TNBC.

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-1ß 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.

Linalool inhibits the angiogenic activity of endothelial cells by downregulating intracellular ATP levels and activating TRPM8.

Angiogenesis crucially contributes to various diseases, such as cancer and diabetic retinopathy. Hence, anti-angiogenic therapy is considered as a powerful strategy against these diseases. Previous studies reported that the acyclic monoterpene linalool exhibits anticancer, anti-inflammatory and anti-oxidative activity. However, the effects of linalool on angiogenesis still remain elusive. Therefore, we investigated the action of (3R)-(-)-linalool, a main enantiomer of linalool, on the angiogenic activity of human dermal microvascular endothelial cells (HDMECs) by a panel of angiogenesis assays. Non-cytotoxic doses of linalool significantly inhibited HDMEC proliferation, migration, tube formation and spheroid sprouting. Linalool also suppressed the vascular sprouting from rat aortic rings. In addition, Matrigel plugs containing linalool exhibited a significantly reduced microvessel density 7 days after implantation into BALB/c mice. Mechanistic analyses revealed that linalool promotes the phosphorylation of extracellular signal-regulated kinase (ERK), downregulates the intracellular level of adenosine triphosphate (ATP) and activates the transient receptor potential cation channel subfamily M (melastatin) member (TRPM)8 in HDMECs. Inhibition of ERK signaling, supplementation of ATP and blockade of TRPM8 significantly counteracted linalool-suppressed HDMEC spheroid sprouting. Moreover, ATP supplementation completely reversed linalool-induced ERK phosphorylation. In addition, linalool-induced ERK phosphorylation inhibited the expression of bone morphogenetic protein (BMP)-2 and linalool-induced TRPM8 activation caused the inhibition of ß1 integrin/focal adhesion kinase (FAK) signaling. These findings indicate an anti-angiogenic effect of linalool, which is mediated by downregulating intracellular ATP levels and activating TRPM8.

Improvement of islet transplantation by the fusion of islet cells with functional blood vessels.

Pancreatic islet transplantation still represents a promising therapeutic strategy for curative treatment of type 1 diabetes mellitus. However, a limited number of organ donors and insufficient vascularization with islet engraftment failure restrict the successful transfer of this approach into clinical practice. To overcome these problems, we herein introduce a novel strategy for the generation of prevascularized islet organoids by the fusion of pancreatic islet cells with functional native microvessels. These insulin-secreting organoids exhibit a significantly higher angiogenic activity compared to freshly isolated islets, cultured islets, and non-prevascularized islet organoids. This is caused by paracrine signaling between the ß-cells and the microvessels, mediated by insulin binding to its corresponding receptor on endothelial cells. In vivo, the prevascularized islet organoids are rapidly blood-perfused after transplantation by the interconnection of their autochthonous microvasculature with surrounding blood vessels. As a consequence, a lower number of islet grafts are required to restore normoglycemia in diabetic mice. Thus, prevascularized islet organoids may be used to improve the success rates of clinical islet transplantation.

Protein Kinase CK2 Regulates Nerve/Glial Antigen (NG)2-Mediated Angiogenic Activity of Human Pericytes.

Protein kinase CK2 is a crucial regulator of endothelial cell proliferation, migration and sprouting during angiogenesis. However, it is still unknown whether this kinase additionally affects the angiogenic activity of other vessel-associated cells. In this study, we investigated the effect of CK2 inhibition on primary human pericytes. We found that CK2 inhibition reduces the expression of nerve/glial antigen (NG)2, a crucial factor which is involved in angiogenic processes. Reporter gene assays revealed a 114 bp transcriptional active region of the human NG2 promoter, whose activity was decreased after CK2 inhibition. Functional analyses demonstrated that the pharmacological inhibition of CK2 by CX-4945 suppresses pericyte proliferation, migration, spheroid sprouting and the stabilization of endothelial tubes. Moreover, aortic rings of NG2-/- mice showed a significantly reduced vascular sprouting when compared to rings of NG2+/+ mice, indicating that NG2 is an important regulator of the angiogenic activity of pericytes. In vivo, implanted Matrigel plugs containing CX-4945-treated pericytes exhibited a lower microvessel density when compared to controls. These findings demonstrate that CK2 regulates the angiogenic activity of pericytes through NG2 gene expression. Hence, the inhibition of CK2 represents a promising anti-angiogenic strategy, because it does not only target endothelial cells, but also vessel-associated pericytes.

Inhibition of erythropoietin-producing hepatoma receptor B4 (EphB4) signalling suppresses the vascularisation and growth of endometriotic lesions.

BACKGROUND AND PURPOSE: The development of endometriotic lesions is crucially dependent on the formation of new blood vessels. In the present study, we analysed whether this process is regulated by erythropoietin-producing hepatoma receptor B4 (EphB4) signalling. EXPERIMENTAL APPROACH: We first assessed the anti-angiogenic action of the EphB4 inhibitor NVP-BHG712 in different in vitro angiogenesis assays. Then, endometriotic lesions were surgically induced in the dorsal skinfold chamber and peritoneal cavity of NVP-BHG712- or vehicle-treated BALB/c mice. This allowed to study the effect of EphB4 inhibition on their vascularisation and growth by means of intravital fluorescence microscopy, high-resolution ultrasound imaging, histology and immunohistochemistry. KEY RESULTS: Non-cytotoxic doses of NVP-BHG712 suppressed the migration, tube formation and sprouting activity of both human dermal microvascular endothelial cells (HDMEC) and mouse aortic rings. Accordingly, we also detected a lower blood vessel density in NVP-BHG712-treated endometriotic lesions. This was associated with a reduced lesion growth due to a significantly lower number of proliferating stromal cells when compared to vehicle-treated controls. CONCLUSIONS AND IMPLICATIONS: Inhibition of EphB4 signalling suppresses the vascularisation and growth of endometriotic lesions. Hence, EphB4 represents a promising pharmacological target for the treatment of endometriosis.

Nerve/glial antigen 2 is crucially involved in the revascularization of freely transplanted pancreatic islets.

Pancreatic islets are highly vascularized endocrine units. Accordingly, their adequate revascularization is of major importance for successful islet transplantation. The proteoglycan, nerve/glial antigen 2 (NG2) expressed in pericytes is a crucial regulator of angiogenesis. Therefore, we herein analyze whether this surface protein contributes to the revascularization of grafted islets. Islets were isolated from NG2+/+ (wild-type) and NG2-/- mice and their cellular composition was analyzed by immunohistochemical detection of insulin, glucagon, somatostatin and CD31. Moreover, insulin secretion was assessed by enzyme-linked immunosorbent assay (ELISA). In addition, isolated islets were transplanted into dorsal skinfold chambers of wild-type mice and their revascularization was determined by intravital fluorescence microscopy and immunohistochemistry. NG2+/+ and NG2-/- islets did not differ in their cellular composition and insulin secretion. However, transplanted NG2-/- islets exhibited a significantly lower functional capillary density and a reduced number of CD31-positive microvessels. These findings demonstrate that the loss of NG2 impairs the revascularization of transplanted islets, underlining the importance of this pericytic proteoglycan for islet engraftment.

Calligonum comosum (Escanbil) extract exerts anti-angiogenic, anti-proliferative and anti-inflammatory effects on endometriotic lesions.

ETHNOPHARMACOLOGICAL RELEVANCE: Calligonum comosum is a desert plant that is applied in traditional folkloric medicine for the treatment of abnormally heavy or prolonged menstruation and menstrual cramps. Moreover, it has been suggested for the treatment of infertility-causing conditions. Its bioactive chemical constituents inhibit multiple processes, such as angiogenesis, inflammation and invasive tissue growth, which may be beneficial in the therapy of endometriosis. AIM OF THE STUDY: We investigated the effects of Calligonum comosum on the development of endometriotic lesions. MATERIALS AND METHODS: We evaluated the anti-angiogenic activity of Calligonum comosum ethyl acetate fraction (CCEAF) in different in vitro angiogenesis assays. Moreover, we surgically induced endometriotic lesions in BALB/c mice, which received 50 mg/kg Calligonum comosum total extract (CCTE) or vehicle (control) over 4 weeks. The growth, cyst formation, vascularization and immune cell infiltration of the lesions were assessed with high-resolution ultrasound imaging, caliper measurements, histology and immunohistochemistry. RESULTS: CCEAF doses of up to 10 µg/mL did not impair the viability of human dermal microvascular endothelial cells (HDMEC), but dose-dependently suppressed their migration, tube formation and sprouting, indicating a substantial anti-angiogenic effect of CCEAF. Furthermore, CCTE significantly inhibited the growth and cyst formation of developing murine endometriotic lesions when compared to vehicle-treated controls. This was associated with a reduced vascularization, cell proliferation and immune cell infiltration. CONCLUSIONS: Our findings show that Calligonum comosum targets multiple, fundamental processes in the pathogenesis of endometriosis, which may be beneficial for the treatment of this common gynecological disorder.

miR-370 inhibits the angiogenic activity of endothelial cells by targeting smoothened (SMO) and bone morphogenetic protein (BMP)-2.

MicroRNAs (miRNAs) crucially modulate fundamental biologic processes such as angiogenesis. In the present study, we focused on the molecular function of miRNA-370-3p (miR-370) in regulating the angiogenic activity of endothelial cells (ECs). Transfection with miR-370 mimic (miR-370m) significantly inhibited the sprouting of human dermal microvascular EC (HDMEC) and HUVEC spheroids and mouse aortic rings, whereas miR-370 inhibitor (miR-370i) promoted sprout formation. Additional in vitro assays demonstrated the pleiotropic inhibitory effects of miR-370m on HDMEC proliferation, migration, and tube formation. Moreover, Matrigel plugs containing miR-370m-transfected HDMECs exhibited a reduced microvessel density after implantation into CD1 nude mice when compared with controls. In contrast, miR-370i exerted proangiogenic effects. Mechanistic analyses revealed that miR-370 directly targets smoothened (SMO) and down-regulates bone morphogenetic protein (BMP)-2 expression in HDMECs. Accordingly, inhibition of SMO by cyclopamine reversed miR-370i-induced HDMEC proliferation and migration. In addition, BMP-2 treatment counteracted miR-370m-suppressed tube formation of HDMECs, whereas blockade of BMP-2 with neutralizing antibody significantly inhibited miR-370i-induced tube formation. Taken together, these novel findings indicate that miR-370 is a potent inhibitor of angiogenesis, which directly targets SMO and BMP-2.-Gu, Y., Becker, V., Zhao, Y., Menger, M. D., Laschke, M. W. miR-370 inhibits the angiogenic activity of endothelial cells by targeting smoothened (SMO) and bone morphogenetic protein (BMP)-2.