Distinct roles of vascular endothelial growth factor-D in lymphangiogenesis and metastasis

The Sympathetic Nervous System Promotes Hepatic Lymphangiogenesis, which Is Protective Against Liver Fibrosis

Liver is the largest lymph-producing organ. In cirrhotic patients, lymph production significantly increases concomitant with lymphangiogenesis. The aim of this study was to determine the mechanism of lymphangiogenesis in liver and its implication in liver fibrosis. Liver biopsies from portal hypertensive patients with portal-sinusoidal vascular disease (n = 22) and liver cirrhosis (n = 5) were evaluated for lymphangiogenesis and compared with controls (n = 9 and n = 6, respectively). For mechanistic studies, rats with partial portal vein ligation (PPVL) and bile duct ligation (BDL) were used. A gene profile data set (GSE77627), including 14 histologically normal liver, 18 idiopathic noncirrhotic portal hypertension, and 22 cirrhotic patients, was analyzed. Lymphangiogenesis was significantly increased in livers from patients with portal-sinusoidal vascular disease, cirrhotic patients, as well as PPVL and BDL rats. Importantly, Schwann cells of sympathetic nerves highly expressed vascular endothelial growth factor-C in PPVL rats. Vascular endothelial growth factor-C neutralizing antibody or sympathetic denervation significantly decreased lymphangiogenesis in livers of PPVL and BDL rats, which resulted in progression of liver fibrosis. Liver specimens from cirrhotic patients showed a positive correlation between sympathetic nerve/Schwann cell-positive areas and lymphatic vessel numbers, which was supported by gene set analysis from patients with noncirrhotic portal hypertension and cirrhotic patients. Sympathetic nerves promote hepatic lymphangiogenesis in noncirrhotic and cirrhotic livers. Increased hepatic lymphangiogenesis can be protective against liver fibrosis.

Anti-angiogenic therapy using the multi-tyrosine kinase inhibitor Regorafenib enhances tumor progression in a transgenic mouse model of ß-cell carcinogenesis

BACKGROUND

Pancreatic neuroendocrine tumors (PNETs) represent a distinct hypervascularized tumor entity, often diagnosed at metastatic stage. Therapeutic efficacy of anti-angiogenic multi-kinase inhibitors is frequently limited by primary or acquired resistance in vivo. This study aimed to characterize the molecular mode of action as well as resistance mechanisms to the anti-angiogenic multi-tyrosine kinase inhibitor (TKI) Regorafenib in vitro and in vivo.

METHODS

In vitro, human and murine pancreatic neuroendocrine cell lines were comparatively treated with Regorafenib and other TKIs clinically used in PNETs. Effects on cell viability and proliferation were analyzed. In vivo, transgenic RIP1Tag2 mice were treated with Regorafenib at two different time periods during carcinogenesis and its impact on angiogenesis and tumor progression was evaluated.

RESULTS

Compared to the established TKI therapies with Sunitinib and Everolimus, Regorafenib showed the strongest effects on cell viability and proliferation in vitro, but was unable to induce apoptosis. Unexpectedly and in contrast to these in vitro findings, Regorafenib enhanced proliferation during early tumor development in RIP1Tag2 mice and had no significant effect in late tumor progression. In addition, invasiveness was increased at both time points. Mechanistically, we could identify an upregulation of the pro-survival protein Bcl-2, the induction of the COX2-PGE2-pathway as well as the infiltration of CSF1R positive immune cells into the tumors as potential resistance mechanisms following Regorafenib treatment.

DISCUSSION

Our data identify important tumor cell-autonomous and stroma-dependent mechanisms of resistance to antiangiogenic therapies.

Embryological, anatomical and clinical considerations on pleuroperitoneal communication

The pleural and peritoneal cavity share many related features due to their common celomic origin. Normally these two spaces are completely separated with the development of the diaphragm. Defects in diaphragm morphogenesis may result in congenital diaphragmatic hernias, which is the most known form of communication between the pleural and peritoneal cavity. However, in several cases, findings of pleuroperitoneal communication (PPC) have been described in adults through an apparently intact diaphragm. In this comprehensive review we systematically evaluate clinical scenarios of this form of "unexpected" PPC as reported in the literature and focus on the possible mechanisms involved.

Models in Pancreatic Neuroendocrine Neoplasms: Current Perspectives and Future Directions

Pancreatic neuroendocrine neoplasms (pNENs) are a heterogeneous group of tumors derived from multiple neuroendocrine origin cell subtypes. Incidence rates for pNENs have steadily risen over the last decade, and outcomes continue to vary widely due to inability to properly screen. These tumors encompass a wide range of functional and non-functional subtypes, with their rarity and slow growth making therapeutic development difficult as most clinically used therapeutics are derived from retrospective analyses. Improved molecular understanding of these cancers has increased our knowledge of the tumor biology for pNENs. Despite these advances in our understanding of pNENs, there remains a dearth of models for further investigation. In this review, we will cover the current field of pNEN models, which include established cell lines, animal models such as mice and zebrafish, and three-dimensional (3D) cell models, and compare their uses in modeling various disease aspects. While no study model is a complete representation of pNEN biology, each has advantages which allow for new scientific understanding of these rare tumors. Future efforts and advancements in technology will continue to create new options in modeling these cancers.

Targeting Tumor Angiogenesis with the Selective VEGFR-3 Inhibitor EVT801 in Combination with Cancer Immunotherapy

The receptor tyrosine kinase VEGFR-3 plays a crucial role in cancer-induced angiogenesis and lymphangiogenesis, promoting tumor development and metastasis. Here, we report the novel VEGFR-3 inhibitor EVT801 that presents a more selective and less toxic profile than two major inhibitors of VEGFRs (i.e., sorafenib and pazopanib). As monotherapy, EVT801 showed a potent antitumor effect in VEGFR-3–positive tumors, and in tumors with VEGFR-3–positive microenvironments. EVT801 suppressed VEGF-C–induced human endothelial cell proliferation in vitro and tumor (lymph)angiogenesis in different tumor mouse models. In addition to reduced tumor growth, EVT801 decreased tumor hypoxia, favored sustained tumor blood vessel homogenization (i.e., leaving fewer and overall larger vessels), and reduced important immunosuppressive cytokines (CCL4, CCL5) and myeloid-derived suppressor cells (MDSC) in circulation. Furthermore, in carcinoma mouse models, the combination of EVT801 with immune checkpoint therapy (ICT) yielded superior outcomes to either single treatment. Moreover, tumor growth inhibition was inversely correlated with levels of CCL4, CCL5, and MDSCs after treatment with EVT801, either alone or combined with ICT. Taken together, EVT801 represents a promising anti(lymph)angiogenic drug for improving ICT response rates in patients with VEGFR-3 positive tumors.

Significance:

The VEGFR-3 inhibitor EVT801 demonstrates superior selectivity and toxicity profile than other VEGFR-3 tyrosine kinase inhibitors. EVT801 showed potent antitumor effects in VEGFR-3–positive tumors, and tumors with VEGFR-3–positive microenvironments through blood vessel homogenization, and reduction of tumor hypoxia and limited immunosuppression. EVT801 increases immune checkpoint inhibitors’ antitumor effects.

Use of Vascular Endothelial Growth Factor-D As a Targeted Therapy in Lymphedema Treatment: A Comprehensive Literature Review

Background: Lymphangiogenic growth factors, such as vascular endothelial growth factor (VEGF)-D, are subjects of interest in studies of targeted therapies in lymphedema treatment. Methods and Results: We conducted a systematic review assessing the use of VEGF-D as a targeted therapy in lymphedema treatment. We hypothesized that VEGF-D was a promising therapy to induce lymphangiogenesis. Our search yielded 90 studies in the literature, but only 4 articles fulfilled our study eligibility criteria, and they were all experimental studies using viral gene transfer. The majority of the studies were conducted on small animals (mice) and investigated the effects of VEGF-D on lymph node transfer. All authors agreed about VEGF-D's lymphangiogenic potential, but they noticed that VEGF-C induced a superior lymphangiogenesis, and one study noticed that VEGF-D induced seroma. Conclusions: The publications assessing the use of VEGF-D as a targeted therapy in lymphedema treatment were able to demonstrate its lymphangiogenic potential. Nonetheless, further studies are still necessary to investigate VEGF-D's efficacy and safety in lymphedema treatment on patients.

Cathepsin L promotes angiogenesis by regulating the CDP/Cux/VEGF-D pathway in human gastric cancer

BACKGROUND

Increasing evidence indicates that angiogenesis plays an important role in tumor progression. The function of cathepsin L (CTSL), an endosomal proteolytic enzyme, in promoting tumor metastasis is well recognized. The mechanisms by which CTSL has promoted the angiogenesis of gastric cancer (GC), however, remains unclear.

METHODS

The nuclear expression levels of CTSL were assessed in GC samples. The effects of CTSL on GC angiogenesis were determined by endothelial tube formation analysis, HUVEC migration assay, and chick embryo chorioallantoic membrane (CAM) assay. The involvement of the CDP/Cux/VEGF-D pathway was analyzed by angiogenesis antibody array, Western blot, co-immunoprecipitation (Co-IP) and dual-luciferase reporter assay.

RESULTS

In this study, we found that the nuclear CTSL expression level in GC was significantly higher than that in adjacent nontumor gastric tissues and was a potential important clinical prognostic factor. Loss- and gain-of-function assays indicated that CTSL promotes the tubular formation and migration of HUVEC cells in vitro. The CAM assay also showed that CTSL promotes angiogenesis of GC in vivo. Mechanistic analysis demonstrated that CTSL can proteolytically process CDP/Cux and produce the physiologically relevant p110 isoform, which stably binds to VEGF-D and promotes the transcription of VEGF-D, thus contributing to the angiogenesis of GC.

CONCLUSION

The findings of the present study suggested that CTSL plays a constructive role in the regulation of angiogenesis in human GC and could be a potential therapeutic target for GC.

Increased Expression of Vascular Endothelial Growth Factor-D Following Brain Injury

Alterations in the expression of the vascular endothelial growth factors (VEGF) A and B occur during blood–brain barrier (BBB) breakdown and angiogenesis following brain injury. In this study, the temporal and spatial expression of VEGF-D and VEGF receptors-2 and -3 (VEGFR-2 and VEGFR-3, respectively) was determined at the mRNA and protein level in the rat cortical cold-injury model over a period of 0.5 to 6 days post-injury. In order to relate endothelial VEGF-D protein expression with BBB breakdown, dual labeling immunofluorescence was performed using antibodies to VEGF-D and to fibronectin, a marker of BBB breakdown. In control rats, VEGF-D signal was only observed in scattered perivascular macrophages in the cerebral cortex. The upregulation of VEGF-D mRNA expression was observed in the injury site between days 0.5 to 4, coinciding with the period of BBB breakdown and angiogenesis. At the protein level, intracerebral vessels with BBB breakdown to fibronectin in the lesion on days 0.5 to 4 failed to show endothelial VEGF-D. Between days 0.5 to 6, an increased VEGF-D immunoreactivity was noted in the endothelium of pial vessels overlying the lesion site, in neutrophils, macrophages, and free endothelial cells within the lesion. The upregulation of VEGFR-2 and -3 mRNA and protein expression was observed early post-injury on day 0.5. Although there was concurrent expression of VEGF-A, VEGF-B, and VEGF-D post-injury, differences in their spatial expression during BBB breakdown and angiogenesis suggest that they have specific and separate roles in these processes.

Hypoxia-Dependent Angiogenesis and Lymphangiogenesis in Cancer

Hypoxia (low O₂) is a ubiquitous feature of solid cancers, arising as a mismatch between cellular O₂ supply and consumption. Hypoxia is associated to metastatic disease and mortality owing to its ability to stimulate the formation of blood (angiogenesis) and lymphatic vessels (lymphangiogenesis), thereby allowing cancer cells to escape the unfavorable tumor microenvironment and disseminate into secondary sites. This review outlines molecular mechanisms by which intratumoral hypoxia regulates the expression of motogenic and mitogenic factors that induce angiogenesis and lymphangiogenesis, whilst discussing their implications for metastatic cancers.

Human Plasma Levels of VEGF-A, VEGF-C, VEGF-D, their Soluble Receptor - VEGFR-2 and Applicability of these Parameters as Tumor Markers in the Diagnostics of Breast Cancer

VEGF family members are important factors in promoting angio- and lymphangiogenesis. The aim of this study was to investigate concentrations, diagnostic utility and power of VEGF-A, VEGF-C, VEGF-D and VEGFR-2 in comparison to CA15-3 in breast cancer (BC) patients. The study included 120 BC patients and 60 control patients (28 with benign breast tumors and 32 healthy women). Plasma levels of tested parameters were determined by ELISA, CA15-3 by CMIA. Concentrations of all parameters showed statistical significance when compared BC patients to controls. VEGF-D showed the highest SE (82.50%) in total BC group. Highest SP and PPV in total BC group showed VEGF-A(76.67%;84.78%,respectively), but lower than CA15-3. Highest NPV showed VEGF-C(52.33%), but it was lower than CA15-3. VEGF-C was also the best parameter which had statistically significant AUC in total cancer group (0.7672), but also stages I(0.7684) and II(0.7772). In the total group of BC almost all tested parameters showed statistically significant AUC, but a maximum range was obtained for the combination of VEGF-C + CA15-3(0.8476). The combined analysis of tested parameters and CA15-3 resulted in increase in SE and AUC values, which provides hope for developing a new panel of biomarkers that may be used in the diagnosis of BC in the future.

EGFR may participate in immune evasion through regulation of B7‑H5 expression in non‑small cell lung carcinoma

Lung cancer is one of the most prevalent malignancies worldwide; it has been ranked the most lethal type of cancer. Non‑small cell lung carcinoma (NSCLC) comprises >80% of all types of lung cancer. Although certain achievements have been made in the treatment of NSCLC, including the targeted gene drug epidermal growth factor receptor‑tyrosine kinase inhibitor (EGFR‑TKI), the five‑year survival rate of patients has not significantly increased. A previous study demonstrated that B7‑H5, a novel co‑stimulatory molecule in the B7 molecule family, was negatively correlated with EGFR in pancreatic cancer. Thus, in the present study, we aimed to investigate whether EGFR participates in immune evasion, probably through regulation of B7‑H5 expression. NCI‑H1299 NSCLCL cells were divided into control, mock, small interfering‑EGFR and EGFR‑TKI groups. The cell viability and apoptosis rate were analysed by a Cell Counting Kit‑8 assay and flow cytometry. The transforming growth factor (TGF)‑β and interleukin (IL)‑10 content was measured using an ELISA. The expression levels of EGFR, B7‑H5, Survivin, apoptosis regulator Bax, apoptosis regulator Bcl‑2 (Bcl‑2), TGF‑β, vascular endothelial growth factor (VEGF), IL‑10 and cyclooxygenase (COX)‑2 were assessed via quantitative PCR and western blotting. The activation of the tyrosine‑protein kinase JAK2 (JAK2)/signal transducer and activator of transcription 3 (STAT3) signalling pathway was detected using western blotting. The results demonstrated a notable negative correlation between EGFR and B7‑H5 expression levels in cancer tissues and cell lines. Inhibition of EGFR expression via gene silencing and EGFR inhibition markedly decreased cell viability and increased the apoptosis of NCI‑H1299 cells, by upregulating survivin and Bcl‑2 expression. The protein expression levels of TGF‑β, VEGF, IL‑10 and COX‑2 were additionally decreased, with weak activation of the JAK2/STAT3 signalling pathway. EGFR may be involved in immune evasion, possibly through regulation of B7‑H5 expression in NSCLC.

Fluorescent reporter transgenic mice for in vivo live imaging of angiogenesis and lymphangiogenesis

The study of lymphangiogenesis is an emerging science that has revealed the lymphatic system as a central player in many pathological conditions including cancer metastasis, lymphedema, and organ graft rejection. A thorough understanding of the mechanisms of lymphatic growth will play a key role in the development of therapeutic strategies against these conditions. Despite the known potential of this field, the study of lymphatics has historically lagged behind that of hemangiogenesis. Until recently, significant strides in lymphatic studies were impeded by a lack of lymphatic-specific markers and suitable experimental models compared to those of the more immediately visible blood vasculature. Lymphangiogenesis has also been shown to be a key phenomenon in developmental biological processes, such as cell proliferation, guided migration, differentiation, and cell-to-cell communication, making lymphatic-specific visualization techniques highly desirable and desperately needed. Imaging modalities including immunohistochemistry and in situ hybridization are limited by the need to sacrifice animal models for tissue harvesting at every experimental time point. Moreover, the processes of mounting and staining harvested tissues may introduce artifacts that can confound results. These traditional methods for investigating lymphatic and blood vasculature are associated with several problems including animal variability (e.g., between mice) when replicating lymphatic growth environments and the cost concerns of prolonged, labor-intensive studies, all of which complicate the study of dynamic lymphatic processes. With the discovery of lymphatic-specific markers, researchers have been able to develop several lymphatic and blood vessel-specific, promoter-driven, fluorescent-reporter transgenic mice for visualization of lymphatics in vivo and in vitro. For instance, GFP, mOrange, tdTomato, and other fluorescent proteins can be expressed under control of a lymphatic-specific marker like Prospero-related homeobox 1 (Prox1), which is a highly conserved transcription factor for determining embryonic organogenesis in vertebrates that is implicated in lymphangiogenesis as well as several human cancers. Importantly, Prox1-null mouse embryos develop without lymphatic vessels. In human adults, Prox1 maintains lymphatic endothelial cells and upregulates proteins associated with lymphangiogenesis (e.g., VEGFR-3) and downregulates angiogenesis-associated gene expression (e.g., STAT6). To visualize lymphatic development in the context of angiogenesis, dual fluorescent-transgenic reporters, like Prox1-GFP/Flt1-DsRed mice, have been bred to characterize lymphatic and blood vessels simultaneously in vivo. In this review, we discuss the trends in lymphatic visualization and the potential usage of transgenic breeds in hemangiogenesis and lymphangiogenesis research to understand spatial and temporal correlations between vascular development and pathological progression.

Emerging Roles for VEGF-D in Human Disease

Blood vessels and lymphatic vessels are located in many tissues and organs throughout the body, and play important roles in a wide variety of prevalent diseases in humans. Vascular endothelial growth factor-D (VEGF-D) is a secreted protein that can promote the remodeling of blood vessels and lymphatics in development and disease. Recent fundamental and translational studies have provided insight into the molecular mechanisms by which VEGF-D exerts its effects in human disease. Hence this protein is now of interest as a therapeutic and/or diagnostic target, or as a potential therapeutic agent, in a diversity of indications in cardiovascular medicine, cancer and the devastating pulmonary condition lymphangioleiomyomatosis. This has led to clinical trial programs to assess the effect of targeting VEGF-D signaling pathways, or delivering VEGF-D, in angina, cancer and ocular indications. This review summarizes our understanding of VEGF-D signaling in human disease, which is largely based on animal disease models and clinicopathological studies, and provides information about the outcomes of recent clinical trials testing agonists or antagonists of VEGF-D signaling.

The paradox of Th17 cell functions in tumor immunity

Immune system acts as a host defensive mechanism protecting against attacking pathogens and transformed cells, including cancer cells. Th17 cells are a specific subset of T helper lymphocytes determined by high secretion of IL-17 and other inflammatory cytokines. Th17 cells increase tumor progression by activating angiogenesis and immunosuppressive activities. They can also mediate antitumor immune responses through recruiting immune cells into tumors, stimulating effector CD8+ T cells, or surprisingly by altering toward Th1 phenotype and producing IFN-γ, so Th17 cells are supposed as a double-edged sword in cancer. A comprehensive approach to indicating the activity of Th17 cells in tumor progression could help in the planning of new therapeutic approaches specially targeting Th17 cells in cancer.

Natriuretic peptide receptor A is related to the expression of vascular endothelial growth factors A and C, and is associated with the invasion potential of tongue squamous cell carcinoma

Natriuretic peptide receptor A (NPRA) is one of the natriuretic peptide receptors. NPRA has been reported to play a role in the carcinogenesis of various tumours, as well as functional roles in renal, cardiovascular, endocrine, and skeletal homeostasis. The clinicopathological significance of NPRA in tongue squamous cell carcinoma (TSCC) was examined in this study. The overexpression of NPRA was more frequent in TSCC (21/58, 36.2%) than in the normal oral epithelium (0/10, 0%) (P<0.05). It was also more frequently observed in cancers with higher grades according to the pattern of invasion (grades 1-2 vs. grades 3-4, P<0.01). Additionally, there was a tendency towards an association between the N classification and NPRA expression (N0 vs. N1-2, P=0.06). Significant correlations were also observed between the expression of NPRA and that of VEGF-A (P<0.001) and VEGF-C (P<0.001). The high-NPRA expression group had a significantly poorer prognosis, with a 5-year disease-specific survival rate of 39.7%, compared to 97.0% in the low-expression group (P<0.001). Multivariate analysis suggested that the overexpression of NPRA may also be an independent prognostic factor (P<0.05). In conclusion, NPRA is associated with VEGF expression levels, invasion, and metastasis, and may be a prognostic factor in TSCC patients.

Elevated VEGF-D Modulates Tumor Inflammation and Reduces the Growth of Carcinogen-Induced Skin Tumors

Vascular endothelial growth factor D (VEGF-D) promotes the lymph node metastasis of cancer by inducing the growth of lymphatic vasculature, but its specific roles in tumorigenesis have not been elucidated. We monitored the effects of VEGF-D in cutaneous squamous cell carcinoma (cSCC) by subjecting transgenic mice overexpressing VEGF-D in the skin (K14-mVEGF-D) and VEGF-D knockout mice to a chemical skin carcinogenesis protocol involving 7,12-dimethylbenz[a]anthracene and 12-O-tetradecanoylphorbol-13-acetate treatments. In K14-mVEGF-D mice, tumor lymphangiogenesis was significantly increased and the frequency of lymph node metastasis was elevated in comparison with controls. Most notably, the papillomas regressed more often in K14-mVEGF-D mice than in littermate controls, resulting in a delay in tumor incidence and a remarkable reduction in the total tumor number. Skin tumor growth and metastasis were not obviously affected in the absence of VEGF-D; however, the knockout mice showed a trend for reduced lymphangiogenesis in skin tumors and in the untreated skin. Interestingly, K14-mVEGF-D mice showed an altered immune response in skin tumors. This consisted of the reduced accumulation of macrophages, mast cells, and CD4⁺ T-cells and an increase of cytotoxic CD8⁺ T-cells. Cytokine profiling by flow cytometry and quantitative real time PCR revealed that elevated VEGF-D expression results in an attenuated Th2 response and promotes M1/Th1 and Th17 polarization in the early stage of skin carcinogenesis, leading to an anti-tumoral immune environment and the regression of primary tumors. Our 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.

Lymphangiogenesis: fuel, smoke, or extinguisher of inflammation's fire?

Lymphangiogenesis is a recognized hallmark of inflammatory processes in tissues and organs as diverse as the skin, heart, bowel, and airways. In clinical and animal models wherein the signaling processes of lymphangiogenesis are manipulated, most studies demonstrate that an expanded lymphatic vasculature is necessary for the resolution of inflammation. The fundamental roles that lymphatics play in fluid clearance and immune cell trafficking from the periphery make these results seemingly obvious as a mechanism of alleviating locally inflamed environments: the lymphatics are simply providing a drain. Depending on the tissue site, lymphangiogenic mechanism, or induction timeframe, however, evidence shows that inflammation-associated lymphangiogenesis (IAL) may worsen the pathology. Recent studies have identified lymphatic endothelial cells themselves to be local regulators of immune cell activity and its consequential phenotypes - a more active role in inflammation regulation than previously thought. Indeed, results focusing on the immunocentric roles of peripheral lymphatic function have revealed that the basic drainage task of lymphatic vessels is a complex balance of locally processed and transported antigens as well as interstitial cytokine and immune cell signaling: an interplay that likely defines the function of IAL. This review will summarize the latest findings on how IAL impacts a series of disease states in various tissues in both preclinical models and clinical studies. This discussion will serve to highlight some emerging areas of lymphatic research in an attempt to answer the question relevant to an array of scientists and clinicians of whether IAL helps to fuel or extinguish inflammation. Impact statement Inflammatory progression is present in acute and chronic tissue pathologies throughout the body. Lymphatic vessels play physiological roles relevant to all medical fields as important regulators of fluid balance, immune cell trafficking, and immune identity. Lymphangiogenesis is often concurrent with inflammation and can potentially aide or worsen disease progression. How new lymphatic vessels impact inflammation and by which mechanism is an important consideration in current and future clinical therapies targeting inflammation and/or vasculogenesis. This review identifies, across a range of tissue-specific pathologies, the current understanding of inflammation-associated lymphangiogenesis in the progression or resolution of inflammation.

Nucleolin Promotes Heat Shock-Associated Translation of VEGF-D to Promote Tumor Lymphangiogenesis

The vascular endothelial growth factor VEGF-D promotes metastasis by inducing lymphangiogenesis and dilatation of the lymphatic vasculature, facilitating tumor cell extravasion. Here we report a novel level of control for VEGF-D expression at the level of protein translation. In human tumor cells, VEGF-D colocalized with eIF4GI and 4E-BP1, which can program increased initiation at IRES motifs on mRNA by the translational initiation complex. In murine tumors, the steady-state level of VEGF-D protein was increased despite the overexpression and dephosphorylation of 4E-BP1, which downregulates protein synthesis, suggesting the presence of an internal ribosome entry site (IRES) in the 5' UTR of VEGF-D mRNA. We found that nucleolin, a nucleolar protein involved in ribosomal maturation, bound directly to the 5'UTR of VEGF-D mRNA, thereby improving its translation following heat shock stress via IRES activation. Nucleolin blockade by RNAi-mediated silencing or pharmacologic inhibition reduced VEGF-D translation along with a subsequent constriction of lymphatic vessels in tumors. Our results identify nucleolin as a key regulator of VEGF-D expression, deepening understanding of lymphangiogenesis control during tumor formation. Cancer Res; 76(15); 4394-405. ©2016 AACR.

Association between VEGF-A, C and D expression and lymph node involvement in breast cancer: a meta-analysis

BACKGROUND

Metastasis is the primary cause of death in patients with breast cancer. Although VEGF-A, C and D are considered to be prime factors in lymph node metastasis in breast cancer, the published studies have conflicting conclusions.

METHODS

To resolve this conflict, we conducted a meta-analysis of 37 studies (n = 5,001 patients) evaluating the correlation between VEGF-A, C and D immunohistochemical expression and lymph node metastasis (LNM). The meta-analysis included 22 studies of VEGF-A, 17 of VEGF-C, and 6 of VEGF-D. The relationships between VEGF-A, C and D and clinicopathological parameters were also examined.

RESULTS

The results showed a significant association between VEGF-A or VEGF-C overexpression and LNM (risk ratio [RR] = 1.28 [95% CI 1.04-1.58], p = 0.02; and RR = 1.36 [95% CI 1.07-1.72], p = 0.01, respectively). Subgroup evaluation showed a significant association between VEGF-A, C and D overexpression and LNM when analyses were limited to Asian patients (RR = 1.78 [95% CI 1.28-2.46], p = 0.0005; RR = 1.38 [95% CI 1.04-1.84], p = 0.03, and RR = 2.62 [95% CI 1.35-5.09], p = 0.004, respectively). VEGF-A overexpression was significantly associated with lymph vessel invasion (RR = 1.86 [95% CI 1.33-2.60], p = 0.0003). Overexpression of VEGF-C or VEGF-D was significantly associated with HER-2 positivity (RR = 1.30 [95% CI 1.06-1.59], p = 0.01; and RR = 1.75 [95% CI 1.01-3.03], p = 0.05, respectively).

CONCLUSIONS

With some limitations, our meta-analysis indicated that VEGF-A and C could predict LNM in patients with breast cancer, particularly Asian patients.

VEGF receptor-2-specific signaling mediated by VEGF-E induces hemangioma-like lesions in normal and in malignant tissue

Viral VEGF-E (ovVEGF-E), a homolog of VEGF-A, was discovered in the genome of Orf virus. Together with VEGF-A, B, C, D, placental growth factor (PlGF) and snake venom VEGF (svVEGF), ovVEGF-E is a member of the VEGF family of potent angiogenesis factors with a bioactivity similar to

VEGF-A

it induces proliferation, migration and sprouting of cultured vascular endothelial cells and proliferative lesions in the skin of sheep, goat and man that are characterized by massive capillary proliferation and dilation. These biological functions are mediated exclusively via its interaction with VEGF receptor-2 (VEGFR-2). Here, we have generated transgenic mice specifically expressing ovVEGF-E in β-cells of the endocrine pancreas (Rip1VEGF-E; RVE). RVE mice show an increase in number and size of the islets of Langerhans and a distorted organization of insulin and glucagon-expressing cells. Islet endothelial cells of RVE mice hyper-proliferate and form increased numbers of functional blood vessels. In addition, the formation of disorganized lymphatic vessels and increased immune cell infiltration is observed. Upon crossing RVE single-transgenic mice with Rip1Tag2 (RT2) transgenic mice, a well-studied model of pancreatic β-cell carcinogenesis, double-transgenic mice (RT2;RVE) display hyper-proliferation of endothelial cells resulting in the formation of hemangioma-like lesions. In addition, RT2;RVE mice exhibit activated lymphangiogenesis at the tumor periphery and increased neutrophil and macrophage tumor infiltration and micro-metastasis to lymph nodes and lungs. These phenotypes markedly differ from the phenotypes observed with the transgenic expression of the other VEGF family members in β-cells of normal mice and of RT2 mice.

The Rip1Tag2 Transgenic Mouse Model

The Rip1Tag2 transgenic mouse model of β-cell carcinogenesis has been instrumental in studying various aspects of tumor angiogenesis and in investigating the response to anti-angiogenic therapeutics. Thereby, the in-depth assessment of blood and lymphatic vessel phenotypes and functionality represents key experimental analyses. In this chapter, we describe basic protocols to assess tumor blood vessel morphology (pericyte coverage), functionality (perfusion, leakiness, and hypoxia), lymphatic tumor coverage, and tumor cell proliferation and apoptosis based on immunofluorescence microscopy analysis.

The lymphatic system and pancreatic cancer

This review summarizes current knowledge of the biology, pathology and clinical understanding of lymphatic invasion and metastasis in pancreatic cancer. We discuss the clinical and biological consequences of lymphatic invasion and metastasis, including paraneoplastic effects on immune responses and consider the possible benefit of therapies to treat tumors that are localized to lymphatics. A review of current techniques and methods to study interactions between tumors and lymphatics is presented.

Understanding lymphangiogenesis in knockout models, the cornea, and ocular diseases for the development of therapeutic interventions

A major focus of cancer research for several decades has been understand the ability of tumors to induce new blood vessel formation, a process known as angiogenesis. Unfortunately, only limited success has been achieved in the clinical application of angiogenesis inhibitors. We now know that lymphangiogenesis, the growth of lymphatic vessels, likely also plays a major role in tumor progression. Thus, therapeutic strategies targeting lymphangiogenesis or both lymphangiogenesis and angiogenesis may represent promising approaches for treating cancer and other diseases. Importantly, research progress toward understanding lymphangiogenesis is significantly behind that related to angiogenesis. A PubMed search of "angiogenesis" returns nearly 80,000 articles, whereas a search of "lymphangiogenesis" returns 2,635 articles. This stark contrast can be explained by the lack of molecular markers for identifying the invisible lymphatic vasculature that persisted until less than 2 decades ago, combined with the intensity of research interest in angiogenesis during the past half century. Still, significant strides have been made in developing strategies to modulate lymphangiogenesis, largely using ocular disease models. Here we review the current knowledge of lymphangiogenesis in the context of knockout models, ocular diseases, the biology of activators and inhibitors, and the potential for therapeutic interventions targeting this process.

FOXC2 expression is associated with tumor proliferation and invasion potential in oral tongue squamous cell carcinoma

Forkhead box protein C2 (FOXC2) is a gene encoding a transcription factor that controls the generation of mesodermal tissue including vascular and lymphatic tissues. FOXC2 has previously been associated with EMT and tumor angiogenesis in various cancers. Moreover, a relationship between the expression of FOXC2 and poor prognosis has been reported in various cancers. We herein examined the clinicopathological significance of FOXC2 in oral tongue squamous cell carcinoma (OTSCC) and attempted to clarify the function of FOXC2 in OTSCC cell lines in vitro. The overexpression of FOXC2 was more frequent in cancers with higher grades according to the pattern of invasion (grade 4 vs. 1-3; p < 0.05). A correlation was observed between the expression of FOXC2 and that of VEGF-A and -C (VEGF-A; p < 0.05, VEGF-C; p < 0.001). The high-FOXC2 expression group had a significantly poorer prognosis than that of the low-expression group (p < 0.001). Multivariate analysis indicated that the overexpression of FOXC2 may also be an independent prognostic factor, similar to N classification (N0 vs 1/2; p < 0.05), stage classification (stage I/II vs III/IV; p < 0.05), pattern of invasion (grade 1-3vs 4; p < 0.05), local recurrence (local recurrence (+) vs (-); p < 0.01), and the overexpression of FOXC2 (FOXC2 overexpression (-) vs.(+); p < 0.05). In the OTSCC cell line analysis, the expression of FOXC2 was also associated with proliferation and invasion potential. These results strongly suggest that the overexpression of FOXC2 may be a potent predictor of survival in OTSCC patients.

Impaired islet function in commonly used transgenic mouse lines due to human growth hormone minigene expression

The human growth hormone (hGH) minigene is frequently used in the derivation of transgenic mouse lines to enhance transgene expression. Although this minigene is present in the transgenes as a secondcistron, and thus not thought to be expressed, we found that three commonly used lines, Pdx1-Cre(Late), RIP-Cre, and MIP-GFP, each expressed significant amounts of hGH in pancreatic islets. Locally secreted hGH binds to prolactin receptors on β cells, activates STAT5 signaling, and induces pregnancy-like changes in gene expression, thereby augmenting pancreatic β cell mass and insulin content. In addition, islets of Pdx1-Cre(Late) mice have lower GLUT2 expression and reduced glucose-induced insulin release and are protected against the β cell toxin streptozotocin. These findings may be important when interpreting results obtained when these and other hGH minigene-containing transgenic mice are used.

The role of interleukin 17 in tumour proliferation, angiogenesis, and metastasis

With 7.6 million deaths globally, cancer according to the World Health Organisation is still one of the leading causes of death worldwide. Interleukin 17 (IL-17) is a cytokine produced by Th17 cells, a T helper cell subset developed from an activated CD4+ T-cell. Whilst the importance of IL-17 in human autoimmune disease, inflammation, and pathogen defence reactions has already been established, its potential role in cancer progression still needs to be updated. Interestingly studies have demonstrated that IL-17 plays an intricate role in the pathophysiology of cancer, from tumorigenesis, proliferation, angiogenesis, and metastasis, to adapting the tumour in its ability to confer upon itself both immune, and chemotherapy resistance. This review will look into IL-17 and summarise the current information and data on its role in the pathophysiology of cancer as well as its potential application in the overall management of the disease.

Emerging Role of Sphingosine-1-phosphate in Inflammation, Cancer, and Lymphangiogenesis

The main function of the lymphatic system is to control and maintain fluid homeostasis, lipid transport, and immune cell trafficking. In recent years, the pathological roles of lymphangiogenesis, the generation of new lymphatic vessels from preexisting ones, in inflammatory diseases and cancer progression are beginning to be elucidated. Sphingosine-1-phosphate (S1P), a bioactive lipid, mediates multiple cellular events, such as cell proliferation, differentiation, and trafficking, and is now known as an important mediator of inflammation and cancer. In this review, we will discuss recent findings showing the emerging role of S1P in lymphangiogenesis, in inflammation, and in cancer.

Prox1 and FOXC2 act as regulators of lymphangiogenesis and angiogenesis in oral squamous cell carcinoma

Prospero homeobox 1 (Prox1) and forkhead box (FOX) C2 regulate angiogenesis and/or lymphangiogenesis. However, the detailed role and function of Prox1 and FOXC2 in cancer remains controversial. In the present study, we examined the expression of Prox1 and FOXC2 proteins in specimens from 163 cases with oral squamous cell carcinoma (OSCC). Furthermore, the role of Prox1 and FOXC2 in cancer cell growth and invasion was evaluated in cultured OSCC cells. Prox1 expression was significantly associated with local progression of the tumor (P = 0.0023), clinical stage (P<0.0001), lymphovessel density (LVD) (P<0.0001), nodal metastasis (P<0.0001), and worse prognosis (P<0.0001). Immunoreactivity of FOXC2 was strongly correlated with microvessel density (MVD) (P<0.0001) and poor prognosis (P = 0.0076). In vitro analysis demonstrated that Prox1 regulates cell growth, proliferation, invasion, and lymphangiogenesis by activating vascular endothelial growth factor (VEGF)-C expression. Furthermore, FOXC2 enhanced the expression level of Prox1 and promoted angiogenesis by enhancement of VEGF-A expression. Our results suggested that Prox1 and FOXC2 play key roles in OSCC progression and that further studies focusing on these proteins may yield useful insights for diagnosis and therapy of OSCC.

The biophysical property of A549 cells transferred by VEGF-D

Vascular endothelial growth factor-D (VEGF-D) together with VEGF-C is considered to be associated with lymphangiogenesis and angiogenesis and involve in tumorization. This study aims to investigate the influence of exogenous VEGF-D gene on the biophysical property of cell surface of lung adenocarcinoma cell line. A panel of lung adenocarcinoma cell lines were examined the expression of VEGF-D and VEGF-C by real-time PCR. The VEGF-D recombinant plasmid containing enhanced green fluorescence protein (EGFP) was constructed and transfected to the cell line with no expression of VEGF-D and confirmed by real-time PCR and Western blot analysis. Topographic images of cells were obtained by using atomic force microscope (AFM) in contact mode. Unlike VEGF-C, VEGF-D was found to have a very low expression or undetectable expression in lung adenocarcinoma cell lines. The VEGF-D recombinant plasmid had been constructed successfully and was transferred into the human lung adenocarcinoma cell line A549 cells which had no endogenous expression of VEGF-D, and exogenous VEGF-D could be detected in mRNA and protein expression levels in the gene modified cells, while the VEGF-C gene expression had no change after VEGF-D transfection. After transfection, the irregular microspikes or nano clusters could observe on the surface of A549 cells, and VEGF-D transfected A549 cells became more rigid. The exogenous VEGF-D gene might cause the remarkable biophysical architectural changes in the A549 cells, which might as a novel biomarker for evaluation of its biological function.

Inhibition of VEGFR-3 activation in tumor-draining lymph nodes suppresses the outgrowth of lymph node metastases in the MT-450 syngeneic rat breast cancer model

For many types of human cancer, the expression of vascular endothelial growth factor-C (VEGF-C) correlates with enhanced tumor-associated lymphatic vessel density, metastasis formation and poor prognosis. In experimental animals, VEGF-C produced by primary tumors can induce lymphangiogenesis within and/or at the periphery of the tumor, and promotes metastasis formation. Tumor-induced lymphangiogenesis is therefore thought to expedite entry of tumor cells into the lymphatic vasculature and their trafficking to regional lymph nodes, thereby fostering metastatic dissemination. Tumour-produced VEGF-C can also drain to the regional lymph nodes and induce lymphangiogenesis there. Whether this activity promotes metastasis formation remains unclear. To address this issue we manipulated VEGF-C activity and VEGFR-3 activation in the lymph nodes draining syngeneic rat breast cancers using intra-dermal delivery of either recombinant VEGF-C or VEGFR-3 blocking antibodies to induce or suppress lymph node lymphangiogenesis, respectively. Recombinant VEGF-C induced lymph node lymphangiogenesis, but was not sufficient to promote metastasis formation by poorly metastatic NM-081 breast tumours. Conversely, inhibition of lymph node lymphangiogeneis induced by highly metastatic MT-450 breast tumours suppressed the outgrowth of lymph node metastases, but not the initial colonization of the lymph nodes. Lung metastasis was also not affected. We conclude that tumor-derived VEGF-C draining to regional lymph nodes promotes the outgrowth of lymph node metastases. VEGF-C may induce lung metastasis independently of its effects on lymph node metastasis.

Lymphovascular and neural regulation of metastasis: shared tumour signalling pathways and novel therapeutic approaches

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.

A practical and sensitive method of quantitating lymphangiogenesis in vivo

To address the inadequacy of current assays, we developed a directed in vivo lymphangiogenesis assay (DIVLA) by modifying an established directed in vivo angiogenesis assay. Silicon tubes (angioreactors) were implanted in the dorsal flanks of nude mice. Tubes contained either growth factor-reduced basement membrane extract (BME)-alone (negative control) or BME-containing vascular endothelial growth factor (VEGF)-D (positive control for lymphangiogenesis) or FGF-2/VEGF-A (positive control for angiogenesis) or a high VEGF-D-expressing breast cancer cell line MDA-MD-468LN (468-LN), or VEGF-D-silenced 468LN. Lymphangiogenesis was detected superficially with Evans Blue dye tracing and measured in the cellular contents of angioreactors by multiple approaches: lymphatic vessel endothelial hyaluronan receptor-1 (Lyve1) protein (immunofluorescence) and mRNA (qPCR) expression and a visual scoring of lymphatic vs blood capillaries with dual Lyve1 (or PROX-11 or Podoplanin)/Cd31 immunostaining in cryosections. Lymphangiogenesis was absent with BME, high with VEGF-D or VEGF-D-producing 468LN cells and low with VEGF-D-silenced 468LN. Angiogenesis was absent with BME, high with FGF-2/VEGF-A, moderate with 468LN or VEGF-D and low with VEGF-D-silenced 468LN. The method was reproduced in a syngeneic murine C3L5 tumor model in C3H/HeJ mice with dual Lyve1/Cd31 immunostaining. Thus, DIVLA presents a practical and sensitive assay of lymphangiogenesis, validated with multiple approaches and markers. It is highly suited to identifying pro- and anti-lymphangiogenic agents, as well as shared or distinct mechanisms regulating lymphangiogenesis vs angiogenesis, and is widely applicable to research in vascular/tumor biology.

Signaling for lymphangiogenesis via VEGFR-3 is required for the early events of metastasis

Metastasis to regional lymph nodes is an important and early event in many tumors. Vascular endothelial growth factor-C (VEGF-C), VEGF-D and their receptor VEGFR-3, play a role in tumor spread via the lymphatics, although the timing of their involvement is not understood. In contrast, VEGFR-2, activated by VEGF-A, VEGF-C and VEGF-D, is a mediator of angiogenesis and drives primary tumor growth. We demonstrate the critical role for VEGFR-3, but not VEGFR-2, in the early events of metastasis. In a tumor model exhibiting both VEGF-D-dependent angiogenesis and lymphangiogenesis, an antibody to VEGFR-2 (DC101) was capable of inhibiting angiogenesis (79 % reduction in PECAM + blood vessels) and growth (93 % reduction in tumor volume). However, unlike an anti-VEGFR-3 Mab (mF4-31C1), DC101 was not capable of eliminating either tumor lymphangiogenesis or lymphogenous metastasis (60 % reduction of lymph node metastasis by DC101 vs 95 % by mF4-31C1). Early excision of the primary tumors demonstrated that VEGF-D-mediated tumor spread precedes angiogenesis-induced growth. Small but highly metastatic primary human breast cancers had significantly higher lymphatic vessel density (23.1 vessels/mm(2)) than size-matched (11.7) or larger non-metastatic tumors (12.4) thus supporting the importance of lymphatic vessels, as opposed to angiogenesis-mediated primary tumor growth, for nodal metastasis. These results suggest that lymphangiogenesis via VEGF-D is more critical than angiogenesis for nodal metastasis.

Mouse models for studying angiogenesis and lymphangiogenesis in cancer

The formation of new blood vessels (angiogenesis) is required for the growth of most tumors. The tumor microenvironment also induces lymphangiogenic factors that promote metastatic spread. Anti-angiogenic therapy targets the mechanisms behind the growth of the tumor vasculature. During the past two decades, several strategies targeting blood and lymphatic vessels in tumors have been developed. The blocking of vascular endothelial growth factor (VEGF)/VEGF receptor-2 (VEGFR-2) signaling has proven effective for inhibition of tumor angiogenesis and growth, and inhibitors of VEGF-C/VEGFR-3 involved in lymphangiogenesis have recently entered clinical trials. However, thus far anti-angiogenic treatments have been less effective in humans than predicted on the basis of pre-clinical tests in mice. Intrinsic and induced resistance against anti-angiogenesis occurs in patients, and thus far the clinical benefit of the treatments has been limited to modest improvements in overall survival in selected tumor types. Our current knowledge of tumor angiogenesis is based mainly on experiments performed in tumor-transplanted mice, and it has become evident that these models are not representative of human cancer. For an improved understanding, angiogenesis research needs models that better recapitulate the multistep tumorigenesis of human cancers, from the initial genetic insults in single cells to malignant progression in a proper tissue environment. To improve anti-angiogenic therapies in cancer patients, it is necessary to identify additional molecular targets important for tumor angiogenesis, and to get mechanistic insight into their interactions for eventual combinatorial targeting. The recent development of techniques for manipulating the mammalian genome in a precise and predictable manner has opened up new possibilities for the generation of more reliable models of human cancer that are essential for the testing of new therapeutic strategies. In addition, new imaging modalities that permit visualization of the entire mouse tumor vasculature down to the resolution of single capillaries have been developed in pre-clinical models and will likely benefit clinical imaging.

Ech1 is a potent suppressor of lymphatic metastasis in hepatocarcinoma

We have previously demonstrated that Ech1 is involved in the lymphatic metastasis of tumors in vitro. Here, we gain an insight into the role that Ech1 is playing in Hca-F cell. The expression of Annexin A7, Gelsolin and Clic1 genes, which were also relevant to tumor lymphatic metastasis, had been inhibited due to downregulation Ech1 gene by Western blot analysis. And downregulated of Ech1 inhibits the metastasic capability of Hca-F cells to peripheral lymph nodes in vivo. Our work indicates although the involvement of Ech1 in tumor metastasis development and progression, but the subcellular location of Ech1 has not much contribution to that.

The VEGF signaling pathway in cancer: the road ahead

The vascular endothelial growth factor (VEGF) family of soluble protein growth factors consists of key mediators of angiogenesis and lymphangiogenesis in the context of tumor biology. The members of the family, VEGF-A (also known as VEGF), VEGF-B, VEGF-C, VEGF-D, and placenta growth factor (PIGF), play important roles in vascular biology in both normal physiology and pathology. The generation of a humanized neutralizing antibody to VEGF-A (bevacizumab, also known as Avastin) and the demonstration of its benefit in numerous human cancers have confirmed the merit of an anti-angiogenesis approach to cancer treatment and have validated the VEGF-A signaling pathway as a therapeutic target. Other members of the VEGF family are now being targeted, and their relevance to human cancer and the development of resistance to anti-VEGF-A treatment are being evaluated in the clinic. Here, we discuss the potential of targeting VEGF family members in the diagnosis and treatment of cancer.

The propeptides of VEGF-D determine heparin binding, receptor heterodimerization, and effects on tumor biology

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.

Transient brown adipocyte-like cells derive from peripheral nerve progenitors in response to bone morphogenetic protein 2

Perineurial-associated brown adipocyte-like cells were rapidly generated during bone morphogenetic protein 2 (BMP2)-induced sciatic nerve remodeling in the mouse. Two days after intramuscular injection of transduced mouse fibroblast cells expressing BMP2 into wild-type mice, there was replication of beta-3 adrenergic receptor(+) (ADRB3(+)) cells within the sciatic nerve perineurium. Fluorescence-activated cell sorting and analysis of cells isolated from these nerves confirmed ADRB3(+) cell expansion and their expression of the neural migration marker HNK1. Similar analysis performed 4 days after BMP2 delivery revealed a significant decrease in ADRB3(+) cells from isolated sciatic nerves, with their concurrent appearance within the adjacent soft tissue, suggesting migration away from the nerve. These soft tissue-derived cells also expressed the brown adipose marker uncoupling protein 1 (UCP1). Quantification of ADRB3-specific RNA in total hind limb tissue revealed a 3-fold increase 2 days after delivery of BMP2, followed by a 70-fold increase in UCP1-specific RNA after 3 days. Expression levels then rapidly returned to baseline by 4 days. Interestingly, these ADRB3(+) UCP1(+) cells also expressed the neural guidance factor reelin. Reelin(+) cells demonstrated distinct patterns within the injected muscle, concentrated toward the area of BMP2 release. Blocking mast cell degranulation-induced nerve remodeling resulted in the complete abrogation of UCP1-specific RNA and protein expression within the hind limbs following BMP2 injection. The data collectively suggest that local BMP2 administration initiates a cascade of events leading to the expansion, migration, and differentiation of progenitors from the peripheral nerve perineurium to brown adipose-like cells in the mouse, a necessary prerequisite for associated nerve remodeling.

Vascular endothelial growth factor-D: signaling mechanisms, biology, and clinical relevance

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.

The connection between lymphangiogenic signalling and prostaglandin biology: a missing link in the metastatic pathway

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.

Recombinant human endostatin endostar inhibits tumor growth and metastasis in a mouse xenograft model of colon cancer

To investigate the effects of recombinant human endostatin Endostar on metastasis and angiogenesis and lymphangiogenesis of colorectal cancer cells in a mouse xenograft model. Colon cancer cells SW620 were injected subcutaneously into the left hind flank of nude mice to establish mouse xenograft models. The mice were treated with normal saline or Endostar subcutaneously every other day. The growth and lymph node metastasis of tumor cells, angiogenesis and lymphangiogenesis in tumor tissue were detected. Apoptosis and cell cycle distribution were studied by flow cytometry. The expression of VEGF-A, -C, or -D in SW620 cells was determined by immunoblotting assays. Endostar inhibited tumor growth and the rate of lymph node metastasis (P < 0.01). The density of blood vessels in or around the tumor area was 12.27 ± 1.21 and 22.25 ± 2.69 per field in Endostar-treated mice and controls (P < 0.05), respectively. Endostar also decreased the density of lymphatic vessels in tumor tissues (7.84 ± 0.81 vs. 13.83 ± 1.08, P < 0.05). Endostar suppresses angiogenesis and lymphangiogenesis in the lymph nodes with metastases, simultaneously. The expression of VEGF-A, -C and -D in SW620 cells treated with Endostar was substantially lower than that of controls. Endostar inhibited growth and lymph node metastasis of colon cancer cells by inhibiting angiogenesis and lymphangiogenesis in a mouse xenograft model of colon cancer.

Role of Akt-mediated VEGF signaling pathway in lymphangiogenesis in gastric cancer

Tumor lymphangiogenesis plays a vital role in lymphatic metastasis of solid tumors and is an important index for evaluation of prognosis. However, due to the lack of understanding of lymphatic endothelium-specific factors and the limitation of detection techniques, the specific mechanisms of lymphatic metastasis and molecule pathways involved in tumor lymphangiogenesis are not well understood. Akt signal pathway is an important transduction pathway that is closely related with the occurrence, proliferation, anti-apoptosis and metastasis of tumors. It has been found that Akt signaling has a close relationship with VEGF signal pathway and mediates lymphatic metastasis or tumor lymphangiogenesis. This article will summarize the role of Akt-mediated VEGF signaling pathway in lymphangiogenesis in gastric cancer.

VEGF-D promotes tumor metastasis by regulating prostaglandins produced by the collecting lymphatic endothelium

Lymphatic 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.

Endothelium-specific overexpression of human vascular endothelial growth factor-D in mice leads to increased tumor frequency and a reduced lifespan

BACKGROUND

Vascular endothelial growth factors (VEGFs) are central mediators in vascular development and lymphangiogenesis. VEGF-D contributes to the growth and formation of blood and lymphatic vessels, although its biological role is still somewhat unclear.

METHODS

Transgenic mice, which express the mature form of human VEGF-D under endothelium-specific Tie1 promoter, were produced by the lentiviral perivitelline-injection method. The mice were followed up to generation F(5) and the effect of the transgene was analyzed.

RESULTS

Transgenic mice had a high expression of human (h)VEGF-D in the endothelium in several tissues, such as kidney, liver, lung and spleen. However, transgenic mice developed tumors in lungs, kidneys, liver, mammary glands and lymph nodes upon aging and their mortality was also increased as a result of other pathological conditions. Hind limb ischemia was surgically induced in these mice and they were analyzed 1, 2 and 3  weeks after the ischemia operation. No significant differences were found in hVEGF-D mRNA expression, the number of capillaries or tissue repair between ischemic transgenic mice and transgene negative littermates.

CONCLUSIONS

It is concluded that targeted unregulated long-term expression of hVEGF-D in endothelium may not be useful and reduces the life span of transgenic mice.

Qidantongmai protects endothelial cells against hypoxia-induced damage through regulating the serum VEGF-a level

Qidantongmai (QDTM) is a Traditional Chinese Medicine (TCM) preparation that has long been used in folk medicine for the treatment of cardiovascular diseases. However, the underlying mechanisms are poorly understood. The present study was designed to determine the effects of QDTM on endothelial cells under hypoxic conditions both in vitro and in vivo. Primary human umbilical vein endothelial cells (HUVECs) were isolated, pretreated with QDTM medicated serum or saline control, and then cultured under hypoxia (2% oxygen) for 24 h. Sprague-Dawley rats were administered 1 ml/100 g of QDTM or saline twice a day for 4 days and treated with hypoxia (6 hours/day, discontinuous hypoxia, 360 mm Hg). QDTM not only protected HUVECs from hypoxia-induced damage by significantly retaining cell viability (P < 0.05) and decreasing apoptosis (P < 0.05) in vitro, but also protected liver endothelial cells from hypoxia-induced damage in vivo. Moreover, QDTM increased the serum VEGF-A level (P < 0.05) in rats treated with hypoxia for 7 days but suppressed the upregulation of serum VEGF-A in rats treated with hypoxia for 14 days. QDTM is a potent preparation that can protect endothelial cells against hypoxia-induced damage. The ability of QDTM to modulate the serum VEGF-A level may play an important role in its effects on endothelial cells.