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Metastasis via the lymphatic vasculature is an important step in cancer progression. The formation of new lymphatic vessels (lymphangiogenesis), or remodeling of existing lymphatics, is thought to facilitate the entry and transport of tumor cells into lymphatic vessels and on to distant organs. The migration of lymphatic endothelial cells (LEC) toward guidance cues is critical for lymphangiogenesis. While chemokines are known to provide directional navigation for migrating immune cells, their role in mediating LEC migration during tumor-associated lymphangiogenesis is not well defined. Here, we undertook gene profiling studies to identify chemokine–chemokine receptor pairs that are involved in tumor lymphangiogenesis associated with lymph node metastasis. CCL27 and CCL28 were expressed in tumor cells with metastatic potential, while their cognate receptor, CCR10, was expressed by LECs and upregulated by the lymphangiogenic growth factor VEGFD and the proinflammatory cytokine TNFα. Migration assays demonstrated that LECs are attracted to both CCL27 and CCL28 in a CCR10-dependent manner, while abnormal lymphatic vessel patterning in CCR10-deficient mice confirmed the significant role of CCR10 in lymphatic patterning. In vivo analyses showed that LECs are recruited to a CCL27 or CCL28 source, while VEGFD was required in combination with these chemokines to enable formation of coherent lymphatic vessels. Moreover, tumor xenograft experiments demonstrated that even though CCL27 expression by tumors enhanced LEC recruitment, the ability to metastasize was dependent on the expression of VEGFD. These studies demonstrate that CCL27 and CCL28 signaling through CCR10 may cooperate with inflammatory mediators and VEGFD during tumor lymphangiogenesis.Significance:The study shows that the remodeling of lymphatic vessels in cancer is influenced by CCL27 and CCL28 chemokines, which may provide a future target to modulate metastatic spread.

Supplementary Figures S1-S8 S1 Heat map of chemokines and receptors S2 Immunohistochemical staining of lymphatic vessels S3 Expression of VEGF-D and chemokines in cancer cell lines S4 Expression of genes in melanoma patient samples S5 Chemokine secretion by tumour cells S6 Chemokine induced migration of LEC S7 Chemokines attract LEC in vivo S8 CCL-293EBNA tumour growth and CCL27 secretion

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Lymph node metastasis, an early and prognostically important event in the progression of many human cancers, is associated with expression of VEGF-D. Changes to lymph node vasculature that occur during malignant progression may create a metastatic niche capable of attracting and supporting tumor cells. In this study, we sought to characterize molecules expressed in lymph node endothelium that could represent therapeutic or prognostic targets. Differential mRNA expression profiling of endothelial cells from lymph nodes that drained metastatic or nonmetastatic primary tumors revealed genes associated with tumor progression, in particular bone morphogenetic protein-4 (BMP-4). Metastasis driven by VEGF-D was associated with reduced BMP-4 expression in high endothelial venules, where BMP-4 loss could remodel the typical high-walled phenotype to thin-walled vessels. VEGF-D expression was sufficient to suppress proliferation of the more typical BMP-4–expressing high endothelial venules in favor of remodeled vessels, and mechanistic studies indicated that VEGF receptor-2 contributed to high endothelial venule proliferation and remodeling. BMP-4 could regulate high endothelial venule phenotype and cellular function, thereby determining morphology and proliferation responses. Notably, therapeutic administration of BMP-4 suppressed primary tumor growth, acting both at the level of tumor cells and tumor stromal cells. Together, our results show that VEGF-D–driven metastasis induces vascular remodeling in lymph nodes. Furthermore, they implicate BMP-4 as a negative regulator of this process, suggesting its potential utility as a prognostic marker or antitumor agent. Cancer Res; 71(20); 6547–57. ©2011 AACR.

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Objectives Lipedema, a poorly understood chronic disease of adipose hyper-deposition, is often mistaken for obesity and causes significant impairment to mobility and quality-of-life. To identify molecular mechanisms underpinning lipedema, we employed comprehensive omics-based comparative analyses of whole tissue, adipocyte precursors (adipose-derived stem cells (ADSCs)), and adipocytes from patients with or without lipedema. Methods We compared whole-tissues, ADSCs, and adipocytes from body mass index–matched lipedema (n = 14) and unaffected (n = 10) patients using comprehensive global lipidomic and metabolomic analyses, transcriptional profiling, and functional assays. Results Transcriptional profiling revealed >4400 significant differences in lipedema tissue, with altered levels of mRNAs involved in critical signaling and cell function-regulating pathways (e.g., lipid metabolism and cell-cycle/proliferation). Functional assays showed accelerated ADSC proliferation and differentiation in lipedema. Profiling lipedema adipocytes revealed >900 changes in lipid composition and >600 differentially altered metabolites. Transcriptional profiling of lipedema ADSCs and non-lipedema ADSCs revealed significant differential expression of >3400 genes including some involved in extracellular matrix and cell-cycle/proliferation signaling pathways. One upregulated gene in lipedema ADSCs, Bub1, encodes a cell-cycle regulator, central to the kinetochore complex, which regulates several histone proteins involved in cell proliferation. Downstream signaling analysis of lipedema ADSCs demonstrated enhanced activation of histone H2A, a key cell proliferation driver and Bub1 target. Critically, hyperproliferation exhibited by lipedema ADSCs was inhibited by the small molecule Bub1 inhibitor 2OH-BNPP1 and by CRISPR/Cas9-mediated Bub1 gene depletion. Conclusion We found significant differences in gene expression, and lipid and metabolite profiles, in tissue, ADSCs, and adipocytes from lipedema patients compared to non-affected controls. Functional assays demonstrated that dysregulated Bub1 signaling drives increased proliferation of lipedema ADSCs, suggesting a potential mechanism for enhanced adipogenesis in lipedema. Importantly, our characterization of signaling networks driving lipedema identifies potential molecular targets, including Bub1, for novel lipedema therapeutics.

Lymphangiogenesis (growth of new lymphatic vessels), and lymphatic remodelling more broadly, are important for disease progression in cancer, lymphedema and the pulmonary disease lymphangioleiomyomatosis. Multiple molecular pathways which signal for aspects of lymphangiogenesis are known but little is understood about their co-ordinate regulation in lymphatic endothelial cells (LECs). Small RNA molecules co-ordinately regulate complex biological processes, but knowledge about their involvement in lymphangiogenesis is limited. Here we used high-throughput small RNA sequencing of LECs to identify microRNAs (miRs) regulating lymphatic remodelling driven by the lymphangiogenic growth factors VEGF-C and VEGF-D. We identified miR-132 as up-regulated by both growth factors, and demonstrated that inhibiting miR-132 in LECs in vitro blocked cell proliferation and tube formation, key steps in lymphangiogenesis. We showed that miR-132 is expressed in human LECs in vivo in the lymphatics of human breast tumours expressing VEGF-D. Importantly, we demonstrated that inhibiting miR-132 in vivo blocked many aspects of lymphangiogenesis in mice. Finally, we identified mRNAs regulated by miR-132 in LECs, by sequencing after RNA-protein cross-linking and Argonaute immunoprecipitation, which demonstrated how miR-132 co-ordinately regulates signalling pathways in lymphangiogenesis. This study shows miR-132 is a critical regulator of lymphangiogenesis and a potential target for therapeutically manipulating lymphatic remodelling in disease.

Lipedema, a poorly understood chronic disease of adipose hyper-deposition, is often mistaken for obesity and causes significant impairment to mobility and quality-of-life. To identify molecular mechanisms underpinning lipedema, we employed comprehensive omics-based comparative analyses of whole tissue, adipocyte precursors (adipose-derived stem cells (ADSCs)), and adipocytes from patients with or without lipedema.We compared whole-tissues, ADSCs, and adipocytes from body mass index-matched lipedema (n = 14) and unaffected (n = 10) patients using comprehensive global lipidomic and metabolomic analyses, transcriptional profiling, and functional assays.Transcriptional profiling revealed4400 significant differences in lipedema tissue, with altered levels of mRNAs involved in critical signaling and cell function-regulating pathways (e.g., lipid metabolism and cell-cycle/proliferation). Functional assays showed accelerated ADSC proliferation and differentiation in lipedema. Profiling lipedema adipocytes revealed900 changes in lipid composition and600 differentially altered metabolites. Transcriptional profiling of lipedema ADSCs and non-lipedema ADSCs revealed significant differential expression of3400 genes including some involved in extracellular matrix and cell-cycle/proliferation signaling pathways. One upregulated gene in lipedema ADSCs, Bub1, encodes a cell-cycle regulator, central to the kinetochore complex, which regulates several histone proteins involved in cell proliferation. Downstream signaling analysis of lipedema ADSCs demonstrated enhanced activation of histone H2A, a key cell proliferation driver and Bub1 target. Critically, hyperproliferation exhibited by lipedema ADSCs was inhibited by the small molecule Bub1 inhibitor 2OH-BNPP1 and by CRISPR/Cas9-mediated Bub1 gene depletion.We found significant differences in gene expression, and lipid and metabolite profiles, in tissue, ADSCs, and adipocytes from lipedema patients compared to non-affected controls. Functional assays demonstrated that dysregulated Bub1 signaling drives increased proliferation of lipedema ADSCs, suggesting a potential mechanism for enhanced adipogenesis in lipedema. Importantly, our characterization of signaling networks driving lipedema identifies potential molecular targets, including Bub1, for novel lipedema therapeutics.

Angiogenesis underlies development, physiology and pathogenesis of cancer, eye and cardiovascular diseases. Inhibiting aberrant angiogenesis using anti-angiogenic therapy (AAT) has been successful in the clinical treatment of cancer and eye diseases. However, resistance to AAT inevitably occurs and its molecular basis remains poorly understood. Here, we uncover molecular modifiers of the blood endothelial cell (EC) response to a widely used AAT bevacizumab by performing a pooled genetic screen using three-dimensional microcarrier-based cell culture and CRISPR–Cas9. Functional inhibition of the epigenetic reader BET family of proteins BRD2/3/4 shows unexpected mitigating effects on EC survival and/or proliferation upon VEGFA blockade. Moreover, transcriptomic and pathway analyses reveal an interaction between epigenetic regulation and anti-angiogenesis, which may affect chromosomal structure and activity in ECs via the cell cycle regulator CDC25B phosphatase. Collectively, our findings provide insight into epigenetic regulation of the EC response to VEGFA blockade and may facilitate development of quality biomarkers and strategies for overcoming resistance to AAT., Through three-dimensional CRISPR screening, He et al. report that functional inhibition of BET family of proteins BRD2/3/4 shows mitigating effects on blood endothelial cell (EC) survival and/or proliferation upon VEGFA blockade. An interaction between epigenetic regulation and anti-angiogenesis, which may affect chromosomal structure and activity in ECs through CDC25B phosphatase, is potentially involved with EC resistance to anti-angiogenic therapy.

Tumour angiogenesis and lymphangiogenesis are hallmarks of cancer and have been associated with tumour progression, tumour metastasis and poor patient prognosis. Many factors regulate angiogenesis and lymphangiogenesis in cancer including non-coding RNAs which are a category of RNAs that do not encode proteins and have important regulatory functions at transcriptional and post-transcriptional levels. Non-coding RNAs can be encapsulated in extracellular vesicles called exosomes which are secreted by tumour cells or other cells in the tumour microenvironment and can then be taken up by the endothelial cells of blood vessels and lymphatic vessels. The “delivery” of these non-coding RNAs to endothelial cells in tumours can facilitate tumour angiogenesis and lymphangiogenesis. Here we review recent findings about exosomal non-coding RNAs, specifically microRNAs and long non-coding RNAs, which regulate tumour angiogenesis and lymphangiogenesis in cancer. We then focus on the potential use of these molecules as cancer biomarkers and opportunities for exploiting ncRNAs for the treatment of cancer.

Even though we have known for over 250 years that cancers spread to regional lymph nodes (LNs) and distant organs, the fundamental question of which anatomical routes are taken by tumor cells has remained a mystery. Two recently published papers in Science, by Pereira et al. and Brown et al., directly address this important issue in tumor biology by assessing the capacity of tumor cells in LNs to spread to distant sites.

While the link between the lymphatic system and the metastatic spread of cancer is centuries old, understanding of the underlying mechanisms is still evolving. Lymphatic vessels provide a route for tumour cells to reach regional lymph nodes (LNs), which is prognostic of distant organ metastasis and poor survival. However, genomic analyses of metastatic cancer now reveal complex patterns of dissemination. The lymphatic endothelial cells lining lymphatics respond to molecular cues from the tumour microenvironment, mediating growth and remodelling of lymphatic vessels at the primary tumour, draining LNs and distant premetastatic niches. Recent studies emphasise that this not only supports metastasis but also influences antitumour immunity. Understanding the complex interactions between tumour cells, the immune system and lymphatics will be essential to inform developing therapeutic and prognostic approaches to cancer.

Remodelling of lymphatic vessels in tumours facilitates metastasis to lymph nodes. The growth factors VEGF-C and VEGF-D are well known inducers of lymphatic remodelling and metastasis in cancer. They are initially produced as full-length proteins requiring proteolytic processing in order to bind VEGF receptors with high affinity and thereby promote lymphatic remodelling. The fibrinolytic protease plasmin promotes processing of VEGF-C and VEGF-D in vitro, but its role in processing them in cancer was unknown. Here we explore plasmin’s role in proteolytically activating VEGF-D in vivo, and promoting lymphatic remodelling and metastasis in cancer, by co-expressing the plasmin inhibitor α2-antiplasmin with VEGF-D in a mouse tumour model. We show that α2-antiplasmin restricts activation of VEGF-D, enlargement of intra-tumoural lymphatics and occurrence of lymph node metastasis. Our findings indicate that the fibrinolytic system influences lymphatic remodelling in tumours which is consistent with previo...

The lymphatic system is a series of vessels that transport cells and excess fluid from tissues to the blood vascular system. Normally quiescent, the lymphatics can grow or remodel in response to developmental, immunological, or cells pathological stimuli. Lymphatic vessels comprise lymphatic endothelial cells (LECs) that can respond to external growth factors by undergoing proliferation, migration, adhesion, and tube and lumen formation into new vessel structures, a process known as lymphangiogenesis. To understand the key gene and signaling pathways necessary for lymphangiogenesis and lymphatic vessel remodeling, we have developed a three-dimensional LEC tube formation assay to explore the role of kinase signaling in these processes. The collagen-overlay-based assay was used with primary human adult dermal LECs to investigate a library of 60 tyrosine kinase (TK) and TK-like genes by siRNA knockdown. Nine candidate genes were identified and characterized for their ability to modify key parameters of lymphatic tube formation, including tube length, area, thickness, branching, and number of blind-ended sacs. Four genes-ZAP70, IRAK4, RIPK1, and RIPK2-were identified as high-confidence hits after tertiary deconvolution screens and demonstrate the utility of the assay to define LEC genes critical for the formation of tube structures. This assay facilitates the identification of potential molecular targets for novel drugs designed to modulate the remodeling of lymphatics that is important for the metastatic spread of cancer and other pathologies.

VEGF-C and VEGF-D are secreted glycoproteins that induce angiogenesis and lymphangiogenesis in cancer, thereby promoting tumor growth and spread. They exhibit structural homology and activate VEGFR-2 and VEGFR-3, receptors on endothelial cells that signal for growth of blood vessels and lymphatics. VEGF-C and VEGF-D were thought to exhibit similar bioactivities, yet recent studies indicated distinct signaling mechanisms (e.g. tumor-derived VEGF-C promoted expression of the prostaglandin biosynthetic enzyme COX-2 in lymphatics, a response thought to facilitate metastasis via the lymphatic vasculature, whereas VEGF-D did not). Here we explore the basis of the distinct bioactivities of VEGF-D using a neutralizing antibody, peptide mapping, and mutagenesis to demonstrate that the N-terminal α-helix of mature VEGF-D (Phe93–Arg108) is critical for binding VEGFR-2 and VEGFR-3. Importantly, the N-terminal part of this α-helix, from Phe93 to Thr98, is required for binding VEGFR-3 but not VEGFR-2. Surprisingly, the corresponding part of the α-helix in mature VEGF-C did not influence binding to either VEGFR-2 or VEGFR-3, indicating distinct determinants of receptor binding by these growth factors. A variant of mature VEGF-D harboring a mutation in the N-terminal α-helix, D103A, exhibited enhanced potency for activating VEGFR-3, was able to promote increased COX-2 mRNA levels in lymphatic endothelial cells, and had enhanced capacity to induce lymphatic sprouting in vivo. This mutant may be useful for developing protein-based therapeutics to drive lymphangiogenesis in clinical settings, such as lymphedema. Our studies shed light on the VEGF-D structure/function relationship and provide a basis for understanding functional differences compared with VEGF-C.

Leakage of fluid from blood vessels, leading to oedema, is a key feature of many diseases including hyperoxic acute lung injury (HALI), which can occur when patients are ventilated with high concentrations of oxygen (hyperoxia). The molecular mechanisms driving vascular leak and oedema in HALI are poorly understood. VEGF-D is a protein that promotes blood vessel leak and oedema when overexpressed in tissues, but the role of endogenous VEGF-D in pathological oedema was unknown. To address these issues, we exposed Vegfd-deficient mice to hyperoxia. The resulting pulmonary oedema in Vegfd-deficient mice was substantially reduced compared to wild-type, as was the protein content of bronchoalveolar lavage fluid, consistent with reduced vascular leak. Vegf-d and its receptor Vegfr-3 were more highly expressed in lungs of hyperoxic, versus normoxic, wild-type mice, indicating that components of the Vegf-d signalling pathway are up-regulated in hyperoxia. Importantly, VEGF-D and its receptors were co-localized on blood vessels in clinical samples of human lungs exposed to hyperoxia; hence, VEGF-D may act directly on blood vessels to promote fluid leak. Our studies show that Vegf-d promotes oedema in response to hyperoxia in mice and support the hypothesis that VEGF-D signalling promotes vascular leak in human HALI. © 2016 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

Metastasis via the lymphatic vasculature is an important step in cancer progression. The formation of new lymphatic vessels (lymphangiogenesis), or remodeling of existing lymphatics, is thought to facilitate the entry and transport of tumor cells into lymphatic vessels and on to distant organs. The migration of lymphatic endothelial cells (LEC) toward guidance cues is critical for lymphangiogenesis. While chemokines are known to provide directional navigation for migrating immune cells, their role in mediating LEC migration during tumor-associated lymphangiogenesis is not well defined. Here, we undertook gene profiling studies to identify chemokine–chemokine receptor pairs that are involved in tumor lymphangiogenesis associated with lymph node metastasis. CCL27 and CCL28 were expressed in tumor cells with metastatic potential, while their cognate receptor, CCR10, was expressed by LECs and upregulated by the lymphangiogenic growth factor VEGFD and the proinflammatory cytokine TNFα. Migration assays demonstrated that LECs are attracted to both CCL27 and CCL28 in a CCR10-dependent manner, while abnormal lymphatic vessel patterning in CCR10-deficient mice confirmed the significant role of CCR10 in lymphatic patterning. In vivo analyses showed that LECs are recruited to a CCL27 or CCL28 source, while VEGFD was required in combination with these chemokines to enable formation of coherent lymphatic vessels. Moreover, tumor xenograft experiments demonstrated that even though CCL27 expression by tumors enhanced LEC recruitment, the ability to metastasize was dependent on the expression of VEGFD. These studies demonstrate that CCL27 and CCL28 signaling through CCR10 may cooperate with inflammatory mediators and VEGFD during tumor lymphangiogenesis. Significance: The study shows that the remodeling of lymphatic vessels in cancer is influenced by CCL27 and CCL28 chemokines, which may provide a future target to modulate metastatic spread.

Transcription factor Myb is overexpressed in most colorectal cancers (CRC). Patients with CRC expressing the highest Myb are more likely to relapse. We previously showed that mono-allelic loss of Myb in an Adenomatous polyposis coli (APC)-driven CRC mouse model (Apc(Min/+)) significantly improves survival. Here we directly investigated the association of Myb with poor prognosis and how Myb co-operates with tumor suppressor genes (TSGs) (Apc) and cell cycle regulator, p27. Here we generated the first intestinal-specific, inducible transgenic model; a MybER transgene encoding a tamoxifen-inducible fusion protein between Myb and the estrogen receptor-α ligand-binding domain driven by the intestinal-specific promoter, Gpa33. This was to mimic human CRC with constitutive Myb activity in a highly tractable mouse model. We confirmed that the transgene was faithfully expressed and inducible in intestinal stem cells (ISCs) before embarking on carcinogenesis studies. Activation of the MybER did not change colon homeostasis unless one p27 allele was lost. We then established that MybER activation during CRC initiation using a pro-carcinogen treatment, azoxymethane (AOM), augmented most measured aspects of ISC gene expression and function and accelerated tumorigenesis in mice. CRC-associated symptoms of patients including intestinal bleeding and anaemia were faithfully mimicked in AOM-treated MybER transgenic mice and implicated hypoxia and vessel leakage identifying an additional pathogenic role for Myb. Collectively, the results suggest that Myb expands the ISC pool within which CRC is initiated while co-operating with TSG loss. Myb further exacerbates CRC pathology partly explaining why high MYB is a predictor of worse patient outcome.

Lymphatic vessels constitute a specialized vasculature that is involved in development, cancer, obesity, and immune regulation. The migration of lymphatic endothelial cells (LECs) is critical for vessel growth (lymphangiogenesis) and vessel remodeling, processes that modify the lymphatic network in response to developmental or pathological demands. Using the publicly accessible results of our genome-wide siRNA screen, we characterized the migratome of primary human LECs and identified individual genes and signaling pathways that regulate LEC migration. We compared our data set with mRNA differential expression data from endothelial and stromal cells derived from two in vivo models of lymphatic vessel remodeling, viral infection and contact hypersensitivity-induced inflammation, which identified genes selectively involved in regulating LEC migration and remodeling. We also characterized the top candidates in the LEC migratome in primary blood vascular endothelial cells to identify genes with functions common to lymphatic and blood vascular endothelium. On the basis of these analyses, we showed that LGALS1, which encodes the glycan-binding protein Galectin-1, promoted lymphatic vascular growth in vitro and in vivo and contributed to maintenance of the lymphatic endothelial phenotype. Our results provide insight into the signaling networks that control lymphangiogenesis and lymphatic remodeling and potentially identify therapeutic targets and biomarkers in disease specific to lymphatic or blood vessels.

Remodelling of lymphatic vessels in tumours facilitates metastasis to lymph nodes. The growth factors VEGF-C and VEGF-D are well known inducers of lymphatic remodelling and metastasis in cancer. They are initially produced as full-length proteins requiring proteolytic processing in order to bind VEGF receptors with high affinity and thereby promote lymphatic remodelling. The fibrinolytic protease plasmin promotes processing of VEGF-C and VEGF-D in vitro, but its role in processing them in cancer was unknown. Here we explore plasmin's role in proteolytically activating VEGF-D in vivo, and promoting lymphatic remodelling and metastasis in cancer, by co-expressing the plasmin inhibitor α

Many cell types undergo migration during embryogenesis and disease. Endothelial cells line blood vessels and lymphatics, which migrate during development as part of angiogenesis, lymphangiogenesis and other types of vessel remodelling. These processes are also important in wound healing, cancer metastasis and cardiovascular conditions. However, the molecular control of endothelial cell migration is poorly understood. Here, we present a dataset containing siRNA screens that identify known and novel components of signalling pathways regulating migration of lymphatic endothelial cells. These components are compared to signalling in blood vascular endothelial cells. Further, using high-content microscopy, we captured a dataset of images of migrating cells following transfection with a genome-wide siRNA library. These datasets are suitable for the identification and analysis of genes involved in endothelial cell migration and morphology, and for computational approaches to identify signalling networks controlling the migratory response and integration of cell morphology, gene function and cell signaling. This may facilitate identification of protein targets for therapeutically modulating angiogenesis and lymphangiogenesis in the context of human disease.

Vascular endothelial growth factors (VEGFs) control angiogenesis and lymphangiogenesis during development and in pathological conditions. In the zebrafish trunk, Vegfa controls the formation of intersegmental arteries by primary angiogenesis and Vegfc is essential for secondary angiogenesis, the formation of veins and lymphatics. VEGFD has been largely thought of as dispensable for vascular development in vertebrates. Here, we generated a zebrafish vegfd mutant by genome editing. vegfd mutants display significant defects in facial lymphangiogenesis independent of vegfc function. Strikingly, we find that vegfc and vegfd cooperatively control lymphangiogenesis throughout the embryo, including during the formation of the trunk lymphatic vasculature. Interestingly, we find that vegfd and vegfc also redundantly drive artery hyperbranching phenotypes observed upon depletion of Flt1 or Dll4. Epistasis and biochemical binding assays suggest that during primary angiogenesis Vegfd influences these phenotypes through Kdr (Vegfr2) rather than Flt4 (Vegfr3). These data demonstrate that, rather than being dispensable during development, Vegfd plays context specific indispensible and also compensatory roles during both blood vessel angiogenesis and lymphangiogenesis.

Background: Preoperative radiotherapy (RT) is commonly used to treat localised soft-tissue sarcomas (STS). Hypoxia is an important determinant of radioresistance. Whether antiangiogenic therapy can ‘normalise' tumour vasculature, thereby improving oxygenation, remains unknown. Methods: Two cohorts were prospectively enrolled. Cohort A evaluated the implications of hypoxia in STS, using the hypoxic tracer 18F-azomycin arabinoside (FAZA-PET). In cohort B, sunitinib was added to preoperative RT in a dose-finding phase 1b/2 design. Results: In cohort A, 13 out of 23 tumours were hypoxic (FAZA-PET), correlating with metabolic activity (r2=0.85; P

Recently developed cancer immunotherapy approaches including immune checkpoint inhibitors and chimeric antigen receptor (CAR) T cell transfer are showing promising results both in trials and in clinical practice. These approaches reflect increasing recognition of the crucial role of the tumor microenvironment in cancer development and progression. Cancer cells do not act alone, but develop a complex relationship with the environment in which they reside. The host immune response to tumors is critical to the success of immunotherapy; however the determinants of this response are incompletely understood. The immune cell infiltrate in tumors varies widely in density, composition, and clinical significance. The tumor vasculature is a key component of the microenvironment that can influence tumor behavior and treatment response, and can be targeted through the use of anti-angiogenic drugs. Blood vascular and lymphatic endothelial cells have important roles in the trafficking of immune cells and controlling the microenvironment, and modulate the immune response. Improving access to the tumor through vascular alteration with anti-angiogenic drugs may prove an effective combinatorial strategy with immunotherapy approaches, and might be applicable to many tumor types. In this review we briefly discuss the host’s immune response to cancer and the treatment strategies utilizing this response, before focusing on the pathological features of tumor blood and lymphatic vessels and the contribution these might make to tumor immune evasion.

Summary: Lymphatic vascular development establishes embryonic and adult tissue fluid balance and is integral in disease. In diverse vertebrate organs, lymphatic vessels display organotypic function and develop in an organ-specific manner. In all settings, developmental lymphangiogenesis is considered driven by vascular endothelial growth factor (VEGF) receptor-3 (VEGFR3), whereas a role for VEGFR2 remains to be fully explored. Here, we define the zebrafish Vegf/Vegfr code in receptor binding studies. We find that while Vegfd directs craniofacial lymphangiogenesis, it binds Kdr (a VEGFR2 homolog) but surprisingly, unlike in mammals, does not bind Flt4 (VEGFR3). Epistatic analyses and characterization of a kdr mutant confirm receptor-binding analyses, demonstrating that Kdr is indispensible for rostral craniofacial lymphangiogenesis, but not caudal trunk lymphangiogenesis, in which Flt4 is central. We further demonstrate an unexpected yet essential role for Kdr in inducing lymphatic endothelial cell fate. This work reveals evolutionary divergence in the Vegf/Vegfr code that uncovers spatially restricted mechanisms of developmental lymphangiogenesis. : Lymphatic vessels display organotypic function and develop in an organ-specific manner. Vogrin et al. find that the zebrafish Kdr receptor is indispensible for craniofacial, but not trunk, lymphangiogenesis whereas Flt4 is essential for the latter. Thus, vascular endothelial growth factor (VEGF) receptor signaling pathways are differentially employed in different tissues to drive developmental lymphangiogenesis. Keywords: developmental biology, Kdr, lymphangiogenesis, lymphatic, organotypic, vascular biology, VEGF, VEGF receptor, Vegfd, zebrafish

The progression of cancer is supported by a wide variety of non-neoplastic cell types which make up the tumour stroma, including immune cells, endothelial cells, cancer-associated fibroblasts and nerve fibres. These host cells contribute molecular signals that enhance primary tumour growth and provide physical avenues for metastatic dissemination. This article provides an overview of the role of blood vessels, lymphatic vessels and nerve fibres in the tumour microenvironment and highlights the interconnected molecular signalling pathways that control their development and activation in cancer. Further, this article highlights the known pharmacological agents which target these pathways and discusses the potential therapeutic uses of drugs that target angiogenesis, lymphangiogenesis and stress-response pathways in the different stages of cancer care.

Mutations in SOX18, VEGFC and Vascular Endothelial Growth Factor 3 underlie the hereditary lymphatic disorders hypotrichosis-lymphedema-telangiectasia (HLT), Milroy-like lymphedema and Milroy disease, respectively. Genes responsible for hereditary lymphedema are key regulators of lymphatic vascular development in the embryo. To identify novel modulators of lymphangiogenesis, we used a mouse model of HLT (Ragged Opossum) and performed gene expression profiling of aberrant dermal lymphatic vessels. Expression studies and functional analysis in zebrafish and mice revealed one candidate, ArfGAP with RhoGAP domain, Ankyrin repeat and PH domain 3 (ARAP3), which is down-regulated in HLT mouse lymphatic vessels and necessary for lymphatic vascular development in mice and zebrafish. We position this known regulator of cell behaviour during migration as a mediator of the cellular response to Vegfc signalling in lymphatic endothelial cells in vitro and in vivo. Our data refine common mechanisms that are likely to contribute during both development and the pathogenesis of lymphatic vascular disorders. Refereed/Peer-reviewed

VEGF-D is an angiogenic and lymphangiogenic glycoprotein that can be proteolytically processed generating various forms differing in subunit composition due to the presence or absence of N- and C-terminal propeptides. These propeptides flank the central VEGF homology domain, that contains the binding sites for VEGF receptors (VEGFRs), but their biological functions were unclear. Characterization of propeptide function will be important to clarify which forms of VEGF-D are biologically active and therefore clinically relevant. Here we use VEGF-D mutants deficient in either propeptide, and in the capacity to process the remaining propeptide, to monitor the functions of these domains. We report for the first time that VEGF-D binds heparin, and that the C-terminal propeptide significantly enhances this interaction (removal of this propeptide from full-length VEGF-D completely prevents heparin binding). We also show that removal of either the N- or C-terminal propeptide is required for VEGF-D to drive formation of VEGFR-2/VEGFR-3 heterodimers which have recently been shown to positively regulate angiogenic sprouting. The mature form of VEGF-D, lacking both propeptides, can also promote formation of these receptor heterodimers. In a mouse tumor model, removal of only the C-terminal propeptide from full-length VEGF-D was sufficient to enhance angiogenesis and tumor growth. In contrast, removal of both propeptides is required for high rates of lymph node metastasis. The findings reported here show that the propeptides profoundly influence molecular interactions of VEGF-D with VEGF receptors, co-receptors, and heparin, and its effects on tumor biology.

Tumor metastasis to lymph nodes is a key indicator of patient survival, and is enhanced by the neo-lymphatics induced by tumor-secreted VEGF-C or VEGF-D, acting via VEGFR-3 signalling. These targets constitute important avenues for anti-metastatic treatment. Despite this new understanding, clinical observations linking metastasis with tumor depth or location suggest that lymphangiogenic growth factors are not the sole determinants of metastasis. Here we explored the influence of tumor proximity to lymphatics capable of responding to growth factors on nodal metastasis in a murine VEGF-D over-expression tumor model. We found that primary tumor location profoundly influenced VEGF-D-mediated lymph node metastasis: 89 % of tumors associated with the flank skin metastasised, in contrast with only 19 % of tumors located more deeply on the body wall (p

Metastasis to local lymph nodes via the lymphatic vessels is a common step in the spread of solid tumors. To investigate the molecular mechanisms underlying the spread of cancer by the lymphatics, we examined the ability of vascular endothelial growth factor (VEGF)-D, a ligand for the lymphatic growth factor receptor VEGFR-3/Flt-4, to induce formation of lymphatics in a mouse tumor model. Staining with markers specific for lymphatic endothelium demonstrated that VEGF-D induced the formation of lymphatics within tumors. Moreover, expression of VEGF-D in tumor cells led to spread of the tumor to lymph nodes, whereas expression of VEGF, an angiogenic growth factor which activates VEGFR-2 but not VEGFR-3, did not. VEGF-D also promoted tumor angiogenesis and growth. Lymphatic spread induced by VEGF-D could be blocked with an antibody specific for VEGF-D. This study demonstrates that lymphatics can be established in solid tumors and implicates VEGF family members in determining the route of metastatic spread.

The analysis of receptor tyrosine kinases and their interacting ligands involved in vascular biology is often challenging due to the constitutive expression of families of related receptors, a broad range of related ligands and the difficulty of dealing with primary cultures of specialized endothelial cells. Here we describe a bioassay for the detection of ligands to the vascular endothelial growth factor receptor-2 (VEGFR-2), a key transducer of signals that promote angiogenesis and lymphangiogenesis. A cDNA encoding a fusion of the extracellular (ligand-binding) region of VEGFR-2 with the transmembrane and cytoplasmic regions of the erythropoietin receptor (EpoR) is expressed in the factor-dependent cell line Ba/F3. This cell line grows in the presence of interleukin-3 (IL-3) and withdrawal of this factor results in death of the cells within 24 hr. Expression of the VEGFR-2/EpoR receptor fusion provides an alternative mechanism to promote survival and potentially proliferation of stably transfected Ba/F3 cells in the presence of a ligand capable of binding and cross-linking the extracellular portion of the fusion protein (i.e., one that can cross-link the VEGFR-2 extracellular region). The assay can be performed in two ways: a semi-quantitative approach in which small volumes of ligand and cells permit a rapid result in 24 hr, and a quantitative approach involving surrogate markers of a viable cell number. The assay is relatively easy to perform, is highly responsive to known VEGFR-2 ligands and can accommodate extracellular inhibitors of VEGFR-2 signaling such as monoclonal antibodies to the receptor or ligands, and soluble ligand traps.

Substantial evidence supports important independent roles for lymphangiogenic growth factor signaling and prostaglandins in the metastatic spread of cancer. The significance of the lymphangiogenic growth factors, vascular endothelial growth factor (VEGF)-C and VEGF-D, is well established in animal models of metastasis, and a strong correlation exits between an increase in expression of VEGF-C and VEGF-D, and metastatic spread in various solid human cancers. Similarly, key enzymes that control the production of prostaglandins, cyclooxygenases (COX-1 and COX-2, prototypic targets of Non-steroidal anti-inflammatory drugs (NSAIDs)), are frequently over-expressed or de-regulated in the progression of cancer. Recent data have suggested an intersection of lymphangiogenic growth factor signaling and the prostaglandin pathways in the control of metastatic spread via the lymphatic vasculature. Furthermore, this correlates with current clinical data showing that some NSAIDs enhance the survival of cancer patients through reducing metastasis. Here, we discuss the potential biochemical and cellular basis for such anti-cancer effects of NSAIDs through the prostaglandin and VEGF signaling pathways.

Vascular endothelial growth factor-D (VEGF-D) is a secreted glycoprotein that promotes growth of blood vessels (angiogenesis) and lymphatic vessels (lymphangiogenesis), and can induce remodeling of large lymphatics. VEGF-D enhances solid tumor growth and metastatic spread in animal models of cancer, and in some human cancers VEGF-D correlates with metastatic spread, poor patient outcome, and, potentially, with resistance to anti-angiogenic drugs. Hence, VEGF-D signaling is a potential target for novel anti-cancer therapeutics designed to enhance anti-angiogenic approaches and to restrict metastasis. In the cardiovascular system, delivery of VEGF-D in animal models enhanced angiogenesis and tissue perfusion, findings which have led to a range of clinical trials testing this protein for therapeutic angiogenesis in cardiovascular diseases. Despite these experimental and clinical developments, our knowledge of the signaling mechanisms driven by VEGF-D is still evolving--here we explore the biology of VEGF-D, its signaling mechanisms, and the clinical relevance of this growth factor.

Shayan R, Karnezis T, Murali R, Wilmott J S, Ashton M W, Taylor G I, Thompson J F, Hersey P, Achen M G, Scolyer R A & Stacker S A (2012) Histopathology 61, 702–710 Lymphatic vessel density in primary melanomas predicts sentinel lymph node status and risk of metastasis Aims: Important prognostic factors in patients with cutaneous melanoma include primary tumour thickness/depth of invasion, ulceration and mitotic rate, and the presence of tumour cells in regional lymph nodes. More recently, features of stromal components, such as blood and lymphatic vessel density, have been suggested as additional indicators of metastatic potential. Our aim was to investigate the relationship between tumour lymphatic vessels and lymph node metastasis. Methods and results: Metastasizing (n = 11) and non-metastasizing (n = 11) primary melanoma samples matched for depth/thickness, mitotic rate and ulceration were examined for lymphatic vessel density (LVD) in the primary tumour, using an antibody to podoplanin. Significant differences were found between LVD (vessels/unit area) in the peripheral (5.73 ± 0.67) versus central (1.72 ± 0.42) regions of the metastasizing tumour group (P

SUMMARY Clinical oncology experience with recently marketed antiangiogenic agents, which inhibit proteins important for tumor angiogenesis, has exposed significant limitations to their efficacy. Bevacizumab, a humanized neutralizing anti-VEGF-A monoclonal antibody, used in combination with cytotoxic chemotherapy for the treatment of metastatic colorectal cancer, represents the best-studied clinical example of targeted antiangiogenic therapy. In this context, bevacizumab provides modestly improved progression-free and overall survival in unselected patient populations via poorly understood mechanisms. Here we review concepts central to the identification and development of biomarkers in order to refine clinical use of bevacizumab in treating colorectal cancer and outline a phenotype-driven strategy for the discovery of high-value candidate biomarkers based on large-scale screening by molecular perturbation.

Vascular endothelial growth factor-D (VEGF-D), a secreted angiogenic and lymphangiogenic glycoprotein, enhances tumor growth and metastasis in animal models, and its expression correlates with metastasis and poor patient outcome in some cancers – it is therefore considered a target for novel anti-cancer therapeutics. The definition of the structure of the complex of VEGF-D bound to its receptors would be beneficial for design of inhibitors of VEGF-D signaling aimed at restricting the growth and spread of cancer. In addition, there is interest in using VEGF-D protein for therapeutic angiogenesis and lymphangiogenesis in the settings of cardiovascular diseases and lymphedema, respectively. However, VEGF-D has proven difficult to express and purify in a highly bioactive form due to a tendency to exist as monomers rather than bioactive dimers. Here we describe a protocol for expression and purification of mature human VEGF-D, and a mutant thereof with reduced glycosylation, potentially suitable for preclinical therapeutic and structural studies, respectively. The degree of glycosylation in mature VEGF-D was reduced by eliminating one of the two N -glycosylation sites, and expressing the protein in Lec3.2.8.1 cells which had reduced glycosylation capacity. Mature VEGF-D and the glycosylation mutant were each enriched for the biologically active dimeric form by optimizing the separation of dimer from monomer via gel filtration, followed by conversion of remaining monomers to dimers via treatment with cysteine. The glycosylation mutant of VEGF-D intended for structural studies preserved all the cysteine residues of mature VEGF-D, in contrast to previous structural studies, exhibited comparable receptor binding to mature VEGF-D and might facilitate structural studies of the VEGF-D/VEGFR-3 complex.

SummaryLymphatic metastasis is facilitated by lymphangiogenic growth factors VEGF-C and VEGF-D that are secreted by some primary tumors. We identified regulation of PGDH, the key enzyme in prostaglandin catabolism, in endothelial cells of collecting lymphatics, as a key molecular change during VEGF-D-driven tumor spread. The VEGF-D-dependent regulation of the prostaglandin pathway was supported by the finding that collecting lymphatic vessel dilation and subsequent metastasis were affected by nonsteroidal anti-inflammatory drugs (NSAIDs), known inhibitors of prostaglandin synthesis. Our data suggest a control point for cancer metastasis within the collecting lymphatic endothelium, which links VEGF-D/VEGFR-2/VEGFR-3 and the prostaglandin pathways. Collecting lymphatics therefore play an active and important role in metastasis and may provide a therapeutic target to restrict tumor spread.

Lymph node metastasis, an early and prognostically important event in the progression of many human cancers, is associated with expression of VEGF-D. Changes to lymph node vasculature that occur during malignant progression may create a metastatic niche capable of attracting and supporting tumor cells. In this study, we sought to characterize molecules expressed in lymph node endothelium that could represent therapeutic or prognostic targets. Differential mRNA expression profiling of endothelial cells from lymph nodes that drained metastatic or nonmetastatic primary tumors revealed genes associated with tumor progression, in particular bone morphogenetic protein-4 (BMP-4). Metastasis driven by VEGF-D was associated with reduced BMP-4 expression in high endothelial venules, where BMP-4 loss could remodel the typical high-walled phenotype to thin-walled vessels. VEGF-D expression was sufficient to suppress proliferation of the more typical BMP-4–expressing high endothelial venules in favor of remodeled vessels, and mechanistic studies indicated that VEGF receptor-2 contributed to high endothelial venule proliferation and remodeling. BMP-4 could regulate high endothelial venule phenotype and cellular function, thereby determining morphology and proliferation responses. Notably, therapeutic administration of BMP-4 suppressed primary tumor growth, acting both at the level of tumor cells and tumor stromal cells. Together, our results show that VEGF-D–driven metastasis induces vascular remodeling in lymph nodes. Furthermore, they implicate BMP-4 as a negative regulator of this process, suggesting its potential utility as a prognostic marker or antitumor agent. Cancer Res; 71(20); 6547–57. ©2011 AACR.

Vascular endothelial growth factor-D (VEGF-D) is a secreted protein that promotes tumor growth and metastatic spread in animal models of cancer. Expression of VEGF-D in prevalent human cancers was reported to correlate with lymph node metastasis and patient outcome—hence, this protein is a potential target for novel anticancer therapeutics designed to restrict tumor growth and spread. Here, we define the binding site in VEGF-D of a neutralizing antibody, designated VD1, which blocks the interaction of VEGF-D with its cell surface receptors vascular endothelial growth factor receptor (VEGFR)-2 and VEGFR-3 and is being used for the development of therapeutic antibodies. We show by peptide-based mapping and site-directed mutagenesis that the VD1 binding site includes the five residues 147NEESL151 and that immunization with a synthetic peptide containing this motif generates antibodies that neutralize VEGF-D. The tertiary structure of VEGF-D indicates that the 147NEESL151 epitope is located in the L2 loop of the growth factor, which is important for receptor binding. Mutation of any of these five residues influences receptor binding; for example, mutations to E148, which abolished binding to VD1, impaired the interaction with VEGFR-2 but enhanced binding to VEGFR-3. This structure/function study indicates that the VD1 binding epitope is part of the receptor binding site of VEGF-D, identifies a region of VEGF-D critical for binding of receptors and explains why VD1 does not bind other members of the VEGF family of growth factors.

Angiogenesis inhibition is a useful strategy for treating cancer. However, the efficacy of anti-angiogenic therapy (AAT) in clinical oncology has been limited largely by highly variable patient response and the inevitable occurrence of resistance. The modest patient benefits have underscored a pressing need for qualified biomarkers and better knowledge of resistance mechanisms. Blood endothelial cells (ECs) are one of the main targets of AAT in the tumor microenvironment. Hence, understanding the EC response to AAT will provide insight into tumor response. To identify molecular modifiers of the EC response to AAT (in this study, bevacizumab, a humanized neutralizing anti-VEGF-A monoclonal antibody), we developed a high-throughput genetic screening platform. This involved a three-dimensional microcarrier-based culture system, CRISPR-Cas9-driven gene loss-of-function (LOF) and VEGF-A-dependent serum-free culture conditions for response modifiers. A pooled kinome-wide CRISPR-Cas9-based screen of 763 genes (with four single guide RNAs/sgRNAs targeting each gene) identified 18 candidate genes that upon LOF (represented by sgRNAs) were significantly enriched or depleted in the bevacizumab versus control treatment arm (P ≤ 0.005, FDR ≤ 0.3). Further candidate evaluation using siRNAs validated six genes whose knockdown conferred EC resistance or sensitization to bevacizumab (P < 0.05). Of these, knockdown of BRD2 or BRD3, which encode the epigenetic reader bromodomain-containing protein 2 or 3 (BRD2 or BRD3), respectively, conferred EC resistance to bevacizumab. The bromodomain and extraterminal domain (BET) inhibitors JQ1 and I-BET762, which selectively target the BET family of proteins (BRD2, BRD3, BRD4 and BRDT), reproduced the results of BRD2 or BRD3 LOF, with a more prominent phenotype (P < 0.05). Drug dose-response assessment indicated an anti-angiogenic effect of BET inhibitors regardless of the presence of bevacizumab. This inhibitory effect was unexpectedly attenuated when cells were co-treated with bevacizumab under VEGF-A-dependent conditions. Experiments to investigate the mechanistic basis for this phenotype of resistance are ongoing and include differential gene expression analysis using RNA-Seq and in vivo evaluation. Applying a non-biased approach to identify molecular modifiers of the EC response to AAT, we demonstrate in this study that BET inhibition is unexpectedly associated with resistance to bevacizumab, despite BET inhibition alone having an anti-angiogenic effect. These observations prompt further evaluation of epigenetic regulation in tumor angiogenesis, particularly in the context of interaction between BET inhibition and VEGF blockade. Clinically, these findings may facilitate development of potential predictive and/or response biomarkers and strategies to overcome resistance to AAT and/or BET inhibitors. Citation Format: Michael Y. He, Michael M. Halford, Marc G. Achen, Steven A. Stacker. A kinome-wide CRISPR screen reveals BET inhibition-associated endothelial cell resistance to anti-angiogenic therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1.