Showing papers by "Kari Alitalo published in 2016"
TL;DR: The most recent advances in the field of lymphatic vascular biology are reviewed, with a focus on cardiovascular disease.
Abstract: The mammalian circulatory system comprises both the cardiovascular system and the lymphatic system. In contrast to the blood vascular circulation, the lymphatic system forms a unidirectional transit pathway from the extracellular space to the venous system. It actively regulates tissue fluid homeostasis, absorption of gastrointestinal lipids, and trafficking of antigen-presenting cells and lymphocytes to lymphoid organs and on to the systemic circulation. The cardinal manifestation of lymphatic malfunction is lymphedema. Recent research has implicated the lymphatic system in the pathogenesis of cardiovascular diseases including obesity and metabolic disease, dyslipidemia, inflammation, atherosclerosis, hypertension, and myocardial infarction. Here, we review the most recent advances in the field of lymphatic vascular biology, with a focus on cardiovascular disease.
238 citations
TL;DR: In obese and insulin-resistant mice, Vegfb gene transfer, together with endothelial Flt1 gene deletion, induced weight loss and mitigated the metabolic complications, demonstrating the therapeutic potential of the VEGFB/VEGFR1 pathway.
175 citations
TL;DR: It is determined that both ANG1 and ANG2 binding to Tie2 increases Tie1-Tie2 interactions in a β1 integrin-dependent manner and that Tie1 regulates ANG-induced Tie2 trafficking in endothelial cells, which supports a model in which Tie1 directly interacts with Tie2 to promote ANG- induced vascular responses under noninflammatory conditions.
Abstract: The angiopoietin/Tie (ANG/Tie) receptor system controls developmental and tumor angiogenesis, inflammatory vascular remodeling, and vessel leakage. ANG1 is a Tie2 agonist that promotes vascular stabilization in inflammation and sepsis, whereas ANG2 is a context-dependent Tie2 agonist or antagonist. A limited understanding of ANG signaling mechanisms and the orphan receptor Tie1 has hindered development of ANG/Tie-targeted therapeutics. Here, we determined that both ANG1 and ANG2 binding to Tie2 increases Tie1-Tie2 interactions in a β1 integrin-dependent manner and that Tie1 regulates ANG-induced Tie2 trafficking in endothelial cells. Endothelial Tie1 was essential for the agonist activity of ANG1 and autocrine ANG2. Deletion of endothelial Tie1 in mice reduced Tie2 phosphorylation and downstream Akt activation, increased FOXO1 nuclear localization and transcriptional activation, and prevented ANG1- and ANG2-induced capillary-to-venous remodeling. However, in acute endotoxemia, the Tie1 ectodomain that is responsible for interaction with Tie2 was rapidly cleaved, ANG1 agonist activity was decreased, and autocrine ANG2 agonist activity was lost, which led to suppression of Tie2 signaling. Tie1 cleavage also occurred in patients with hantavirus infection. These results support a model in which Tie1 directly interacts with Tie2 to promote ANG-induced vascular responses under noninflammatory conditions, whereas in inflammation, Tie1 cleavage contributes to loss of ANG2 agonist activity and vascular stability.
162 citations
TL;DR: Angiopoietin-2 activation of Tie2 supports stable enlargement of normal nonleaky vessels, but reduction of Tie1 in inflammation leads to ANG2 antagonism of tie2 and initiates a positive feedback loop wherein FOXO1-driven ANG2 expression promotes vascular remodeling and leakage.
Abstract: Angiopoietin-2 (ANG2) regulates blood vessel remodeling in many pathological conditions through differential effects on Tie2 signaling. While ANG2 competes with ANG1 to inhibit Tie2, it can paradoxically also promote Tie2 phosphorylation (p-Tie2). A related paradox is that both inactivation and overactivation of Tie2 can result in vascular remodeling. Here, we reconciled these opposing actions of ANG2 by manipulating conditions that govern its actions in the vasculature. ANG2 drove vascular remodeling during Mycoplasma pulmonis infection by acting as a Tie2 antagonist, which led to p-Tie2 suppression, forkhead box O1 (FOXO1) activation, increased ANG2 expression, and vessel leakiness. These changes were exaggerated by anti-Tie2 antibody, inhibition of PI3K signaling, or ANG2 overexpression and were reduced by anti-ANG2 antibody or exogenous ANG1. In contrast, under pathogen-free conditions, ANG2 drove vascular remodeling by acting as an agonist, promoting high p-Tie2, low FOXO1 activation, and no leakage. Tie1 activation was strong under pathogen-free conditions, but infection or TNF-α led to Tie1 inactivation by ectodomain cleavage and promoted the Tie2 antagonist action of ANG2. Together, these data indicate that ANG2 activation of Tie2 supports stable enlargement of normal nonleaky vessels, but reduction of Tie1 in inflammation leads to ANG2 antagonism of Tie2 and initiates a positive feedback loop wherein FOXO1-driven ANG2 expression promotes vascular remodeling and leakage.
158 citations
TL;DR: It is suggested that the establishment of tumor-associated inflammation and immunity critically depends on lymphatic vessel remodeling and drainage, and the results have implications for immunotherapies, the efficacies of which are regulated by the tumor immune microenvironment.
Abstract: Lymphatic remodeling in tumor microenvironments correlates with progression and metastasis, and local lymphatic vessels play complex and poorly understood roles in tumor immunity. Tumor lymphangiogenesis is associated with increased immune suppression, yet lymphatic vessels are required for fluid drainage and immune cell trafficking to lymph nodes, where adaptive immune responses are mounted. Here, we examined the contribution of lymphatic drainage to tumor inflammation and immunity using a mouse model that lacks dermal lymphatic vessels (K14-VEGFR3-Ig mice). Melanomas implanted in these mice grew robustly, but exhibited drastically reduced cytokine expression and leukocyte infiltration compared with those implanted in control animals. In the absence of local immune suppression, transferred cytotoxic T cells more effectively controlled tumors in K14-VEGFR3-Ig mice than in control mice. Furthermore, gene expression analysis of human melanoma samples revealed that patient immune parameters are markedly stratified by levels of lymphatic markers. This work suggests that the establishment of tumor-associated inflammation and immunity critically depends on lymphatic vessel remodeling and drainage. Moreover, these results have implications for immunotherapies, the efficacies of which are regulated by the tumor immune microenvironment.
150 citations
TL;DR: It is shown that an ADAMTS3-CCBE1 complex can form independently of VEGFR3 and is required to convert VEGFC, but not VEGFD, into an active ligand, revealing that lymphangiogenesis is regulated by two distinct proteolytic mechanisms of ligand activation.
Abstract: Lymphangiogenesis is supported by 2 homologous VEGFR3 ligands, VEGFC and VEGFD. VEGFC is required for lymphatic development, while VEGFD is not. VEGFC and VEGFD are proteolytically cleaved after cell secretion in vitro, and recent studies have implicated the protease a disintegrin and metalloproteinase with thrombospondin motifs 3 (ADAMTS3) and the secreted factor collagen and calcium binding EGF domains 1 (CCBE1) in this process. It is not well understood how ligand proteolysis is controlled at the molecular level or how this process regulates lymphangiogenesis, because these complex molecular interactions have been difficult to follow ex vivo and test in vivo. Here, we have developed and used biochemical and cellular tools to demonstrate that an ADAMTS3-CCBE1 complex can form independently of VEGFR3 and is required to convert VEGFC, but not VEGFD, into an active ligand. Consistent with these ex vivo findings, mouse genetic studies revealed that ADAMTS3 is required for lymphatic development in a manner that is identical to the requirement of VEGFC and CCBE1 for lymphatic development. Moreover, CCBE1 was required for in vivo lymphangiogenesis stimulated by VEGFC but not VEGFD. Together, these studies reveal that lymphangiogenesis is regulated by two distinct proteolytic mechanisms of ligand activation: one in which VEGFC activation by ADAMTS3 and CCBE1 spatially and temporally patterns developing lymphatics, and one in which VEGFD activation by a distinct proteolytic mechanism may be stimulated during inflammatory lymphatic growth.
97 citations
TL;DR: This study shows that vascular endothelial growth factor-B (VEGF-B) gene therapy can be used to prevent the cardiotoxicity of doxorubicin (DOX), and VEGF-B inhibited DOX-induced cardiac atrophy, protected endothelial cells from apoptosis, and preserved the myocardial capillary network.
Abstract: Congestive heart failure is one of the leading causes of disability in long-term survivors of cancer The anthracycline antibiotic doxorubicin (DOX) is used to treat a variety of cancers, but its utility is limited by its cumulative cardiotoxicity As advances in cancer treatment have decreased cancer mortality, DOX-induced cardiomyopathy has become an increasing problem However, the current means to alleviate the cardiotoxicity of DOX are limited We considered that vascular endothelial growth factor-B (VEGF-B), which promotes coronary arteriogenesis, physiological cardiac hypertrophy, and ischemia resistance, could be an interesting candidate for prevention of DOX-induced cardiotoxicity and congestive heart failure To study this, we administered an adeno-associated viral vector expressing VEGF-B or control vector to normal and tumor-bearing mice 1 wk before DOX treatment, using doses mimicking the concentrations used in the clinics VEGF-B treatment completely inhibited the DOX-induced cardiac atrophy and whole-body wasting VEGF-B also prevented capillary rarefaction in the heart and improved endothelial function in DOX-treated mice VEGF-B also protected cultured endothelial cells from apoptosis and restored their tube formation VEGF-B increased left ventricular volume without compromising cardiac function, reduced the expression of genes associated with pathological remodeling, and improved cardiac mitochondrial respiration Importantly, VEGF-B did not affect serum or tissue concentrations of DOX or augment tumor growth By inhibiting DOX-induced endothelial damage, VEGF-B could provide a novel therapeutic possibility for the prevention of chemotherapy-associated cardiotoxicity in cancer patients
90 citations
TL;DR: The results identify Prox1 as an essential transcription factor that regulates skeletal muscle phenotype and myoblast differentiation by interacting with the NFAT and Notch pathways.
Abstract: The remarkable adaptive and regenerative capacity of skeletal muscle is regulated by several transcription factors and pathways. Here we show that the transcription factor Prox1 is an important regulator of myoblast differentiation and of slow muscle fibre type. In both rodent and human skeletal muscles Prox1 is specifically expressed in slow muscle fibres and in muscle stem cells called satellite cells. Prox1 activates the NFAT signalling pathway and is necessary and sufficient for the maintenance of the gene program of slow muscle fibre type. Using lineage-tracing we show that Prox1-positive satellite cells differentiate into muscle fibres. Furthermore, we provide evidence that Prox1 is a critical transcription factor for the differentiation of myoblasts via bi-directional crosstalk with Notch1. These results identify Prox1 as an essential transcription factor that regulates skeletal muscle phenotype and myoblast differentiation by interacting with the NFAT and Notch pathways.
53 citations
TL;DR: It is shown that vein formation are disrupted in mouse skin and mesentery when Tie2 signals are diminished by targeted deletion of Tek either ubiquitously or specifically in embryonic ECs, implying that Tie2 is essential for venous specification and maintenance via Akt mediated stabilization of COUP-TFII.
Abstract: Mechanisms underlying the vein development remain largely unknown. Tie2 signaling mediates endothelial cell (EC) survival and vascular maturation and its activating mutations are linked to venous malformations. Here we show that vein formation are disrupted in mouse skin and mesentery when Tie2 signals are diminished by targeted deletion of Tek either ubiquitously or specifically in embryonic ECs. Postnatal Tie2 attenuation resulted in the degeneration of newly formed veins followed by the formation of haemangioma-like vascular tufts in retina and venous tortuosity. Mechanistically, Tie2 insufficiency compromised venous EC identity, as indicated by a significant decrease of COUP-TFII protein level, a key regulator in venogenesis. Consistently, angiopoietin-1 stimulation increased COUP-TFII in cultured ECs, while Tie2 knockdown or blockade of Tie2 downstream PI3K/Akt pathway reduced COUP-TFII which could be reverted by the proteasome inhibition. Together, our results imply that Tie2 is essential for venous specification and maintenance via Akt mediated stabilization of COUP-TFII.
51 citations
TL;DR: High PROX1 and β-catenin expression were independent factors for better prognosis in pancreatic ductal adenocarcinoma and predicted lower risk of death from PDAC.
Abstract: The Wnt/β-catenin pathway has a key role in regulating cellular processes and its aberrant signaling can lead to cancer development. The role of β-catenin expression in pancreatic ductal adenocarcinoma is somewhat controversial. Transcription factor PROX1 is a target of Wnt/β-catenin signaling and it is involved in carcinogenesis through alterations in its expression. The actions can be either oncogenic or tumor suppressive depending on the tissue. The aim of this study was to investigate PROX1 and β-catenin expression in pancreatic ductal adenocarcinoma (PDAC). Expression of PROX1 and β-catenin were evaluated in 156 patients by immunohistochemistry of tissue microarrays. Associations between tumor marker expression and clinicopathological parameters were assessed by the Fischer’s exact-test or the linear-by-linear association test. The Kaplan-Meier method and log-rank test were used for survival analysis. Uni- and multivariate survival analyses were carried out by the Cox regression proportional hazard model. High PROX1 expression was seen in 74 (48 %) tumors, and high β-catenin expression in 100 (65 %). High β-catenin expression was associated with lower tumor grade (p = 0.025). High PROX1 and β-catenin expression associated significantly with lower risk of death from PDAC in multivariate analysis (HR = 0.63; 95 % CI 0.42–0.95, p = 0.026; and HR = 0.54; 95 % CI 0.35–0.82, p = 0.004; respectively). The combined high expression of PROX1 and β-catenin also predicted lower risk of death from PDAC (HR = 0.46; 95 % CI 0.28–0.76, p = 0.002). In conclusion, high PROX1 and β-catenin expression were independent factors for better prognosis in pancreatic ductal adenocarcinoma.
38 citations
TL;DR: It is indicated that elevated VEGF-C levels contribute to metabolic deterioration and the development of insulin resistance, and that blockade of VEGf-C in obesity represents a suitable approach to alleviate the developmentof insulin resistance.
Abstract: Obesity comprises great risks for human health, contributing to the development of other diseases such as metabolic syndrome, type 2 diabetes and cardiovascular disease. Previously, obese patients were found to have elevated serum levels of VEGF-C, which correlated with worsening of lipid parameters. We recently identified that neutralization of VEGF-C and -D in the subcutaneous adipose tissue during the development of obesity improves metabolic parameters and insulin sensitivity in mice. To test the hypothesis that VEGF-C plays a role in the promotion of the metabolic disease, we used K14-VEGF-C mice that overexpress human VEGF-C under control of the keratin-14 promoter in the skin and monitored metabolic parameters over time. K14-VEGF-C mice had high levels of VEGF-C in the subcutaneous adipose tissue and gained more weight than wildtype littermates, became insulin resistant and had increased ectopic lipid accumulation at 20 weeks of age on regular mouse chow. The metabolic differences persisted under high-fat diet induced obesity. These results indicate that elevated VEGF-C levels contribute to metabolic deterioration and the development of insulin resistance, and that blockade of VEGF-C in obesity represents a suitable approach to alleviate the development of insulin resistance.
TL;DR: The results suggest that tissue damage rapidly changes lymphatic vessel phenotype, which, in turn, may shape the interplay of innate and adaptive immunity.
TL;DR: An unexpected role is revealed for VEGF-C, a major lymphangiogenic growth factor, in the transition to FL erythropoiesis, characterized by anemia and lack of enucleated red blood cells in blood circulation.
TL;DR: This research presents a novel probabilistic approach that allows us to assess the importance of knowing the carrier and removal status of canine coronavirus, as a source of infection for other animals.
Abstract: Rationale: Lymphatic vessel growth is mediated by major prolymphangiogenic factors, such as vascular endothelial growth factor (VEGF-C) and VEGF-D, among other endothelial effectors. Heparan sulfate is a linear polysaccharide expressed on proteoglycan core proteins on cell membranes and matrix, playing roles in angiogenesis, although little is known about any function(s) in lymphatic remodeling in vivo. Objective: To explore the genetic basis and mechanisms, whereby heparan sulfate proteoglycans mediate pathological lymphatic remodeling. Methods and Results: Lymphatic endothelial deficiency in the major heparan sulfate biosynthetic enzyme N -deacetylase/ N -sulfotransferase-1 (Ndst1; involved in glycan-chain sulfation) was associated with reduced lymphangiogenesis in pathological models, including spontaneous neoplasia. Mouse mutants demonstrated tumor-associated lymphatic vessels with apoptotic nuclei. Mutant lymphatic endothelia demonstrated impaired mitogen (Erk) and survival (Akt) pathway signaling and reduced VEGF-C–mediated protection from starvation-induced apoptosis. Lymphatic endothelial-specific Ndst1 deficiency (in Ndst1 f/f Prox1 +/ Cre ERT2 mice) was sufficient to inhibit VEGF-C–dependent lymphangiogenesis. Lymphatic heparan sulfate deficiency reduced phosphorylation of the major lymphatic growth receptor VEGF receptor-3 in response to multiple VEGF-C species. Syndecan-4 was the dominantly expressed heparan sulfate proteoglycan in mouse lymphatic endothelia, and pathological lymphangiogenesis was impaired in Sdc4 (−/−) mice. On the lymphatic cell surface, VEGF-C induced robust association between syndecan-4 and VEGF receptor-3, which was sensitive to glycan disruption. Moreover, VEGF receptor-3 mitogen and survival signaling was reduced in the setting of Ndst1 or Sdc4 deficiency. Conclusions: These findings demonstrate the genetic importance of heparan sulfate and the major lymphatic proteoglycan syndecan-4 in pathological lymphatic remodeling. This may introduce novel future strategies to alter pathological lymphatic-vascular remodeling.
TL;DR: Nanoparticles against VEGFR2 and −3 expressing tumor-associated endothelial cells represent a promising and novel anti-cancer strategy that leads to tumor starvation and pronounced reduction of tumor burden.
Abstract: Background: Tumor progression depends on angiogenesis. Vascular endothelial growth factor (VEGF) receptors (VEGFRs) are the main signal transducers that stimulate endothelial cell migration and vessel sprouting. At present, only VEGFR2 is targeted in the clinical practice.Purpose: To develop new, anti-angiogenic nanoparticles (immunoliposomes, ILs), that redirect cytotoxic compounds to tumor-associated vascular cells.Methods: Pegylated liposomal doxorubicin (PLD) was targeted against VEGFR2- and VEGFR3-expressing cells by inserting anti-VEGFR2 and/or anti-VEGFR3 antibody fragments into the lipid bilayer membrane of PLD. These constructs were tested in vitro, and in vivo in the Rip1Tag2 mouse model of human cancer.Results: The combination treatment with anti-VEGFR2-ILs-dox and anti-VEGFR3-ILs-dox was superior to targeting only VEGFR2 cells and provides a highly efficient approach of depleting tumor-associated vasculature. This leads to tumor starvation and pronounced reduction of tumor burden.Concl...
TL;DR: The data suggest that VEGF-D may be beneficial in early-stage tumors since it suppresses the pro-tumorigenic inflammation, while at later stages VEGf-D-induced tumor lymphatics provide a route for metastasis.
01 Jan 2016
TL;DR: It is shown that the homogeneously staining regions of the COLO 320 HSR marker chromosome contain amplified c-myc, and amplification of c- myc has been accompanied by translocation of the gene from its normal position on chromosome 8 (8q24).
Abstract: Two human neuroendocrine tumor cell lines de- rived from a colon carcinoma contain either numerous double min- ute chromosomes (COLO 320 DM) or a homogeneously staining marker chromosome (COLO 320 HSR). We found amplification and enhanced expression of the cellular oncogene c-myc in both COLO 320 DM and HSR cells, and we were able to show that the homogeneously staining regions of the COLO 320 HSR marker chromosome contain amplified c-myc. From previous and present karyotypes, it appears that the homogeneously staining regions re- side on a distorted X chromosome. Therefore, amplification of c- myc has been accompanied by translocation of the gene from its normal position on chromosome 8 (8q24). Because double minute