Angiotensinogen Delays Angiogenesis and Tumor Growth of Hepatocarcinoma in Transgenic Mice

François Vincent, Philippe Bonnin, Maud Clemessy, Jean-Olivier Contrerès, Noël Lamandé, Jean-Marie Gasc, José Vilar, Patricia Hainaud, Gérard Tobelem, Pierre Corvol1 and Evelyne Dupuy

Angiotensinogen, a member of the serpin family, is involved in the suppression of tumor growth and metastasis. To investigate whether human angiotensinogen protects against tumor progression in vivo, we established an original bitransgenic model in which transgenic mice expressing human angiotensinogen (Hu-AGT-TG mice) were crossed with a transgenic mouse model of hepatocellular carcinoma (HCC-TG mice). Bitransgenic mice overexpressing human angiotensinogen (HCC/Hu-AGT-TG) had a significantly longer survival time than the HCC-TG mice and a reduction of both tumor growth and blood flow velocities in the liver. This antitumor effect of angiotensinogen is related to a reduced angiogenesis, impaired expression of endothelial arterial markers (active Notch4, Delta-like 4 ligand, and ephrin B2) with a decrease of arterial vessel density in HCC/Hu-AGT-TG mice liver. Overexpression of human angiotensinogen decreases angiogenesis, and prevents tumor sinusoids from remodeling and arterialization, thus delaying tumor progression in vivo.

EZH2 is a mediator of EWS/FLI1 driven tumor growth and metastasis blocking endothelial and neuro-ectodermal differentiation

Günther H. S. Richter, Stephanie Plehm, Annette Fasan, Sabine Rössler, Rebekka Unland, Idriss M. Bennani-Baiti, Marc Hotfilder, Diana Löwel, Irene von Luettichau, Ilona Mossbrugger, Leticia Quintanilla-Martinez, Heinrich Kovar, Martin S. Staege, Carsten Müller-Tidow, and Stefan Burdach

Ewing tumors (ET) are highly malignant, localized in bone or soft tissue, and are molecularly defined by ews/ets translocations. DNA microarray analysis revealed a relationship of ET to both endothelium and fetal neural crest. We identified expression of histone methyltransferase enhancer of Zeste, Drosophila, Homolog 2 (EZH2) to be increased in ET. Suppressive activity of EZH2 maintains stemness in normal and malignant cells. Here, we found EWS/FLI1 bound to the EZH2 promoter in vivo, and induced EZH2 expression in ET and mesenchymal stem cells. Down-regulation of EZH2 by RNA interference in ET suppressed oncogenic transformation by inhibiting clonogenicity in vitro. Similarly, tumor development and metastasis was suppressed in immunodeficient Rag2−/−γC−/− mice. EZH2-mediated gene silencing was shown to be dependent on histone deacetylase (HDAC) activity. Subsequent microarray analysis of EZH2 knock down, HDAC-inhibitor treatment and confirmation in independent assays revealed an undifferentiated phenotype maintained by EZH2 in ET. EZH2 regulated stemness genes such as nerve growth factor receptor (NGFR), as well as genes involved in neuroectodermal and endothelial differentiation (EMP1, EPHB2, GFAP, and GAP43). These data suggest that EZH2 might have a central role in ET pathology by shaping the oncogenicity and stem cell phenotype of this tumor.

Dysfunctional Microvasculature as a Consequence of Shb Gene Inactivation Causes Impaired Tumor Growth

Nina S. Funa, Vitezslav Kriz, Guangxiang Zang, Gabriela Calounova, Björn Åkerblom, Jaroslav Mares, Erik Larsson, Ying Sun, Christer Betsholtz and Michael Welsh

Shb (Src homology 2 protein B) is an adapter protein downstream of the vascular endothelial growth factor receptor receptor-2 (VEGFR-2). Previous experiments have suggested a role for Shb in endothelial cell function. Recently, the Shb gene was inactivated and Shb null mice were obtained on a mixed genetic background, but not on C57Bl6 mice. The present study was performed to address endothelial function in the Shb knockout mouse and its relevance for tumor angiogenesis. Tumor growth was retarded in Shb mutant mice, and this correlated with decreased angiogenesis both in tumors and in Matrigel plugs. Shb null mice display an abnormal endothelial ultrastructure in liver sinusoids and heart capillaries with cytoplasmic extensions projecting toward the lumen. Shb null heart VE-cadherin staining was less distinct than that of control heart, exhibiting in the former case a wavy and punctuate pattern. Experiments on isolated endothelial cells suggest that these changes could partly reflect cytoskeletal abnormalities. Vascular permeability was increased in Shb null mice in heart, kidney, and skin, whereas VEGF-stimulated vascular permeability was reduced in Shb null mice. It is concluded that Shb plays an important role in maintaining a functional vasculature in adult mice, and that interference with Shb signaling may provide novel means to regulate tumor angiogenesis.

Pleiotrophin produced by multiple myeloma induces transdifferentiation of monocytes into vascular endothelial cells: a novel mechanism of tumor-induced vasculogenesis

Haiming Chen, Richard A. Campbell, Yunchao Chang, Mingjie Li, Cathy S. Wang, Jennifer Li, Eric Sanchez, Michael Share, Jeffrey Steinberg, Ariana Berenson, Dror Shalitin, Zhaohui Zeng, Dorina Gui, Pablo Perez-Pinera, Ronald J. Berenson, Jonathan Said, Benjamin Bonavida, Thomas F. Deuel, and James R. Berenson

Enhanced angiogenesis is a hallmark of cancer. Pleiotrophin (PTN) is an angiogenic factor that is produced by many different human cancers and stimulates tumor blood vessel formation when it is expressed in malignant cancer cells. Recent studies show that monocytes may give rise to vascular endothelium. In these studies, we show that PTN combined with macrophage colony-stimulating factor (M-CSF) induces expression of vascular endothelial cell (VEC) genes and proteins in human monocyte cell lines and monocytes from human peripheral blood (PB). Monocytes induce VEC gene expression and develop tube-like structures when they are exposed to serum or cultured with bone marrow (BM) from patients with multiple myeloma (MM) that express PTN, effects specifically blocked with antiPTN antibodies. When coinjected with human MM cells into severe combined immunodeficient (SCID) mice, green fluorescent protein (GFP)–marked human monocytes were found incorporated into tumor blood vessels and expressed human VEC protein markers and genes that were blocked by anti-PTN antibody. Our results suggest that vasculogenesis in human MM may develop from tumoral production of PTN, which orchestrates the transdifferentiation of monocytes into VECs.

Mitogen-Activated Protein 3 Kinase 6 Mediates Angiogenic and Tumorigenic Effects via Vascular Endothelial Growth Factor Expression

Nobuaki Eto, Makoto Miyagishi, Reiko Inagi, Toshiro Fujita and Masaomi Nangaku

Genome-wide screening using a small interfering RNA (siRNA) library has revealed novel molecules that are involved in a wide range of physiological responses. The expression of vascular endothelial growth factor (VEGF) is increased under hypoxic conditions, and plays a crucial role in tumor angiogenesis and tissue responses to ischemia. Here, we used a siRNA expression vector library to elucidate molecules that modify VEGF expression. Screening using an siRNA library revealed that MAPKKK6 (MEKK6/MAP3K6) regulates VEGF expression under both normoxic and hypoxic conditions in vitro, although the biological function of MAP3K6 remains unknown. Attenuation of VEGF expression by MAP3K6 inhibition was demonstrated by transient transfection of double-stranded RNA as well as by stable transfection of short hairpin RNA-expressing vectors against MAP3K6. Conditioned medium of MAP3K6-knocked down cells attenuated both endothelial proliferation and capillary network formation in a VEGF-dependent manner in vitro. In addition, tumor cells with down-regulation of MAP3K6 expression showed significant suppression of tumor growth in vivo, which was accompanied by significant repression of vessel formation and VEGF expression in these tumors. The results of this study suggest that MAP3K6 regulates VEGF expression in both normoxia and hypoxia, and that regulation of VEGF by MAP3K6 may play a crucial role in both angiogenesis and tumorigenesis.

Cross-talk between Tumor and Endothelial Cells Involving the Notch3-Dll4 Interaction Marks Escape from Tumor Dormancy

Stefano Indraccolo, Sonia Minuzzo, Massimo Masiero, Irene Pusceddu, Luca Persano, Lidia Moserle, Andrea Reboldi, Elena Favaro, Marco Mecarozzi, Giuseppina Di Mario, Isabella Screpanti, Maurilio Ponzoni, Claudio Doglioni and Alberto Amadori

The Notch ligand Dll4 has a recognized role during both physiologic and tumor angiogenesis, as it contributes to regulate Notch activity in endothelial cells (EC). The effects of Dll4 on Notch signaling in tumor cells expressing Notch receptors remain, however, largely unknown. Here, we report that escape of human T-cell acute lymphoblastic leukemia (T-ALL) cells or colorectal cancer cells from dormancy is associated with Dll4 expression in the tumor microenvironment and increased Notch3 signaling in tumor cells. Dll4 was expressed at early time points during the angiogenic process, and its expression preceded perfusion of the newly established vessels. Treatment of EC with angiogenic factors induced Dll4 expression and increased Notch3 activation in cocultured T-ALL cells. Neutralization of Dll4 greatly reduced EC-mediated activation of Notch 3 signaling in T-ALL cells and blocked tumorigenesis. Moreover, silencing Notch3 by RNA interference had marked antiproliferative and proapoptotic effects on T-ALL cells in vitro and reduced tumorigenicity in vivo. Our results elucidate a novel mechanism by which a direct interplay between endothelial and tumor cells promotes survival and triggers tumor growth.

Selective Inhibition of Matrix Metalloproteinase-14 Blocks Tumor Growth, Invasion, and Angiogenesis

Laetitia Devy, Lili Huang, Laurent Naa, Niranjan Yanamandra, Henk Pieters, Nicolas Frans, Edward Chang, Qingfeng Tao, Marc Vanhove, Annabelle Lejeune, Reinoud van Gool, Daniel J. Sexton, Guannan Kuang, Douglas Rank, Shannon Hogan, Csaba Pazmany, Yu Lu Ma, Sonia Schoonbroodt, Andrew E. Nixon, Robert C. Ladner, Rene Hoet, Paula Henderikx, Chris TenHoor, Shafaat A. Rabbani, Maria Luisa Valentino, Clive R. Wood and Daniel T. Dransfield

Inhibition of specific matrix metalloproteinases (MMP) is an attractive noncytotoxic approach to cancer therapy. MMP-14, a membrane-bound zinc endopeptidase, has been proposed to play a central role in tumor growth, invasion, and neovascularization. Besides cleaving matrix proteins, MMP-14 activates proMMP-2 leading to an amplification of pericellular proteolytic activity. To examine the contribution of MMP-14 to tumor growth and angiogenesis, we used DX-2400, a highly selective fully human MMP-14 inhibitory antibody discovered using phage display technology. DX-2400 blocked proMMP-2 processing on tumor and endothelial cells, inhibited angiogenesis, and slowed tumor progression and formation of metastatic lesions. The combination of potency, selectivity, and robust in vivo activity shows the potential of a selective MMP-14 inhibitor for the treatment of solid tumors.

Host-Derived Angiopoietin-2 Affects Early Stages of Tumor Development and Vessel Maturation but Is Dispensable for Later Stages of Tumor Growth

Patrick Nasarre, Markus Thomas, Karoline Kruse, Iris Helfrich, Vivien Wolter, Carleen Deppermann, Dirk Schadendorf, Gavin Thurston, Ulrike Fiedler and Hellmut G. Augustin

The angiopoietin/Tie2 system has been identified as the second vascular-specific receptor tyrosine kinase system controlling vessel assembly, maturation, and quiescence. Angiopoietin-2 (Ang-2) is prominently up-regulated in the host-derived vasculature of most tumors, making it an attractive candidate for antiangiogenic intervention. Yet, the net outcome of Ang-2 functions on tumor angiogenesis is believed to be contextual depending on the local cytokine milieu. Correspondingly, Ang-2 manipulatory therapies have been shown to exert protumorigenic as well as antitumorigenic effects. To clarify the role of Ang-2 for angiogenesis and tumor growth in a definite genetic experimental setting, the present study was aimed at comparatively studying the growth of different tumors in wild-type and Ang-2–deficient mice. Lewis lung carcinomas, MT-ret melanomas, and B16F10 melanomas all grew slower in Ang-2–deficient mice. Yet, tumor growth in wild-type and Ang-2–deficient mice dissociated during early stages of tumor development, whereas tumor growth rates during later stages of primary tumor progression were similar. Analysis of the intratumoral vascular architecture revealed no major differences in microvessel density and perfusion characteristics. However, diameters of intratumoral microvessels were smaller in tumors grown in Ang-2–deficient mice, and the vasculature had an altered pattern of pericyte recruitment and maturation. Ang-2–deficient tumor vessels had higher pericyte coverage indices. Recruited pericytes were desmin and NG2 positive and predominately -smooth muscle actin negative, indicative of a more mature pericyte phenotype. Collectively, the experiments define the role of Ang-2 during tumor angiogenesis and establish a better rationale for combination therapies involving Ang-2 manipulatory therapies.

Massive T-Lymphocyte Infiltration into the Host Stroma Is Essential for Fibroblast Growth Factor-2-Promoted Growth and Metastasis of Mammary Tumors via Neovascular Stability

Satoshi Tsunoda, Hiroaki Sakurai, Yurika Saito, Yoko Ueno, Keiichi Koizumi and Ikuo Saiki

Inflammation in the tumor stroma greatly influences tumor development. In the present study, we investigated the roles of fibroblast growth factor (FGF)-2-induced chronic inflammation in the development of 4T1 murine mammary tumors. Administration of FGF-2 into the tumor inoculation site during the initial phase of tumor growth enhanced tumor growth and pulmonary metastasis as well as microvessel density in tumor tissues in normal but not in nude mice. Infiltration of T lymphocytes and macrophages, recruitment of pericytes/vascular mural cells in neovascular walls, and the expression levels of cyclooxygenase (COX)-2 and vascular endothelial growth factor A (VEGFA) were also enhanced in the FGF-2-activated host stroma of normal mice. In addition, FGF-2-induced tumor growth and metastasis was abrogated by administration of either an immunosuppressant, FK506, or a COX-2 inhibitor. FGF-2 enhanced prostaglandin E2 secretion in cultured T lymphocytes. In addition, VEGFA secretion was increased in a co-culture of T lymphocytes and fibroblasts in vitro. These results indicate that the massive infiltration of T lymphocytes into FGF-2-activated host stroma during the initial phase of tumor growth enhances neovascular stability by regulating endogenous COX-2 and VEGFA levels because both compounds are known to play important roles in marked 4T1 mammary tumor development via FGF-2-induced inflammatory reactions.

Fetal Microchimeric Cells Participate in Tumour Angiogenesis in Melanomas Occurring during Pregnancy

Sau Nguyen Huu, Michèle Oster, Marie-Françoise Avril, Françoise Boitier, Laurent Mortier, Marie-Aleth Richard, Delphine Kerob, Eve Maubec, Pierre Souteyrand, Philippe Moguelet, Kiarash Khosrotehrani and Selim Aractingi

Melanoma is a major malignancy in younger individuals that accounts for 8% of all neoplasias associated with gestation. During pregnancy, a small number of fetal cells enter the maternal circulation. These cells persist and then migrate to various maternal tissues where they may engraft and differentiate, particularly if there is organ damage, adopting the phenotype of the host organ. To understand the relationship between melanoma and pregnancy, we analyzed these tumors in both humans and mice. Fetal cells were detected in 63% of human primary melanomas versus 12% in nevi during pregnancy (P = 0.034) and in 57% of B16 melanomas in pregnant mice but never in normal skin (P = 0.000022). More than 50% of these fetal cells expressed the CD34, CD31, or von Willebrand factor endothelial cell markers. In addition, the Lyve-1 lymphatic antigen was expressed by more than 30% of fetal cells in mice. In conclusion, we show that melanomas during pregnancy frequently harbor fetal cells that have an endothelial phenotype. Further studies are needed to assess whether the fetal contribution to lymphangiogenesis may alter the prognosis of the maternal tumor.

Host CXCR2-Dependent Regulation of Melanoma Growth, Angiogenesis, and Experimental Lung Metastasis

Seema Singh, Michelle Varney and Rakesh K. Singh

Crucial steps in tumor growth and metastasis are proliferation, survival, and neovascularization. Previously, we have shown that receptors for CXCL-8, CXCR1, and CXCR2 are expressed on endothelial cells and CXCR2 has been shown to be a putative receptor for angiogenic chemokines. In this report, we examined whether tumor angiogenesis and growth of CXCL-8–expressing human melanoma cells are regulated in vivo by a host CXCR2–dependent mechanism. We generated mCXCR2–/–, mCXCR2+/–, and wild-type nude mice following crosses between BALB/c mice heterozygous for nude+/– and heterozygous for mCXCR2+/–. We observed a significant inhibition of human melanoma tumor growth and experimental lung metastasis in mCXCR2–/– mice as compared with wild-type nude mice. Inhibition in tumor growth and metastasis was associated with a decrease in melanoma cell proliferation, survival, inflammatory response, and angiogenesis. Together, these studies show the importance of host CXCR2–dependent CXCL-8–mediated angiogenesis in the regulation of melanoma growth and metastasis.

Thyroid Hormone Receptor β1 Acts as a Potent Suppressor of Tumor Invasiveness and Metastasis

Olaia Martínez-Iglesias, Susana Garcia-Silva, Stephan P. Tenbaum, Javier Regadera, Fernando Larcher, Jesus M. Paramio, Bjorn Vennström and Ana Aranda

Loss of thyroid hormone receptors (TR) is a common feature in some tumors, although their role in tumor progression is currently unknown. We show here that expression of TRβ1 in hepatocarcinoma and breast cancer cells reduces tumor growth, causes partial mesenchymal-to-epithelial cell transition, and has a striking inhibitory effect on invasiveness, extravasation, and metastasis formation in mice. In cultured cells, TRβ1 abolishes anchorage-independent growth and migration, blocks responses to epidermal growth factor, insulin-like growth factor-I, and transforming growth factor β, and regulates expression of genes that play a key role in tumorigenicity and metastatic growth. The receptor disrupts the mitogenic action of growth factors by suppressing activation of extracellular signal-regulated kinase and phosphatidylinositol 3-kinase signaling pathways that are crucial for cell proliferation and invasiveness. Furthermore, increased aggressiveness of skin tumors is found in genetically modified mice lacking TRs, further demonstrating the role of these receptors as inhibitors of tumor progression. These results define a novel role for the thyroid hormone receptor as a metastasis suppressor gene, providing a starting point for the development of novel therapeutic strategies for the treatment of human cancer.