Molecular lymphangiogenesis: new players

Case report: Noonan syndrome with protein-losing enteropathy

Background: Noonan syndrome (NS) is characterized by typical facial features, short stature, congenital heart defects and other comorbidities. Lymphedema and chylous pleural effusions are also common in NS, but protein-losing enteropathy (PLE) is rarely reported. Case presentation: We present the case of a 19-year-old Chinese woman presenting with PLE. Small intestine biopsy showed obvious expansion of lymphatic vessels. The gene mutation results of the patient indicated a c.184T>G missense mutation (p.Tyr62Asp) in the PTPN11 gene (NM_002834.3). Conclusion: NS accompanied by PLE is not common, but hypoproteinemia attributable to PLE may be more common in patients with NS than previously thought. It remains uncertain whether mutation of the PTPN11 gene is related to PLE, indicating that further research is needed.

Biomechanical control of lymphatic vessel physiology and functions

The ever-growing research on lymphatic biology has clearly identified lymphatic vessels as key players that maintain human health through their functional roles in tissue fluid homeostasis, immunosurveillance, lipid metabolism and inflammation. It is therefore not surprising that the list of human diseases associated with lymphatic malfunctions has grown larger, including issues beyond lymphedema, a pathology traditionally associated with lymphatic drainage insufficiency. Thus, the discovery of factors and pathways that can promote optimal lymphatic functions may offer new therapeutic options. Accumulating evidence indicates that aside from biochemical factors, biomechanical signals also regulate lymphatic vessel expansion and functions postnatally. Here, we review how mechanical forces induced by fluid shear stress affect the behavior and functions of lymphatic vessels and the mechanisms lymphatic vessels employ to sense and transduce these mechanical cues into biological signals.

Hydroxysafflor yellow A regulates lymphangiogenesis and inflammation via the inhibition of PI3K on regulating AKT/mTOR and NF-κB pathway in macrophages to reduce atherosclerosis in ApoE-/- mice

BACKGROUND

Macrophage-mediated inflammatory infiltration and pathological lymphangiogenesis around atherosclerotic plaques are newly highlighted treatment targets of atherosclerosis. Although the effect of Hydroxysafflor yellow A(HSYA) on atherosclerosis was clear, few studies focus on the regulation of HSYA on such mechanisms.

PURPOSE

This study aimed to uncover the key site of HSYA on improving atherosclerosis by regulating macrophage-induced inflammation and lymphangiogenesis.

STUDY DESIGN

This study was designed to explore the new mechanism of HSYA on alleviating atherosclerosis in vitro and in vivo.

METHODS

We determined the expression of vascular endothelial growth factor C(VEGF-C) in Raw264.7 cells and high-fat diet fed ApoE knockout (ApoE^-/-) mice. Raw264.7 cells were treated with HSYA under the stimulation of LPS and ox-LDL. HFD induced ApoE^-/- mice were given different concentrations of HSYA-saline solution by tail vein injection and ATV-saline suspension by gavage. C57/B6j mice fed with chow diet were used for the control group. H&E, oil red O and immunofluorescence staining analysis were used for visualizing the pathological changes. The biological impact of HSYA was evaluated by body weight, lipid metabolism, inflammation levels, and corresponding function indexes of kidney and liver. RT-qPCR and western blot methods were conducted to determine the expression of the inflammation and lymphangiogenesis factors. Molecular docking and microscale thermophoresis analysis were used to verify the combination of HSYA and PI3K.

RESULTS

In vivo, HSYA reduced the plaque formation, hepatic steatosis and inflammation-related lymphangiogenesis (IAL). It also changed the serum levels of inflammation (VEGF-C, TNF-α, IL-6, VCAM1, MCP1), lipid indexes (LDL, CHOL, TRIG) and relevant lymphangiogenesis (VEGF-C and LYVE-1) and inflammation (VCAM-1 and IL-6) signals in the aorta. In vitro, HSYA regulated Akt/mTOR and NF-κB activation by the inhibition of PI3K in macrophages.

CONCLUSION

HSYA affects inflammation and inflammation-associated lymphangiogenesis via suppressing PI3K to affect AKT/mTOR and NF-B pathway activation in macrophages, showing a comprehensive protective effect on atherosclerosis.

Lymphangiogenesis, a potential treatment target for myocardial injury

The lymphatic vascular system is crucial for the regulation of tissue fluid homeostasis, lipid metabolism, and immune function. Cardiac injury quickly leads to myocardial edema, cardiac lymphatic dysfunction, which ultimately results in myocardial fluid imbalance and cardiac dysfunction. Therefore, lymphangiogenesis-targeted therapy may improve the recovery of myocardial function post cardiac ischemia as observed in myocardial infarction (MI). Indeed, a promising strategy for the clinical treatment of MI relies on vascular endothelial growth factor-C (VEGF-C)-targeted therapy, which promotes lymphangiogenesis. However, much effort is needed to identify the mechanisms of lymphatic transport in response to heart disease. This article reviews regulatory factors of lymphangiogenesis, and discusses the effects of lymphangiogenesis on cardiac function after cardiac injury and its regulatory mechanisms. The involvement of stem cells on lymphangiogenesis was also discussed as stem cells could differentiate into lymphatic endothelial cells (LECs) and stimulate phenotype of LECs.

Lymphatic Vascular Density, the Expression of Podoplanin and Tumor Budding in Oral Squamous Cell Carcinoma

BACKGROUND

Notwithstanding recent advances in oral squamous cell carcinoma (OSCC) management, its mortality rate is still high. It is imperative to investigate new parameters that are complementary to clinical staging for OSCC to provide better prognostic insight. The presence of isolated neoplastic cells or small clusters of up to four cells at the tumor's invasive front, called tumor budding, is a morphological marker of OSCC with prognostic value. Increased lymphatic vascular density (LVD) and a high expression of podoplanin in neoplastic cells have also been associated with worse prognosis in OSCC. To investigate these markers in OSCC, we evaluated differences in LVD and the expression of podoplanin in neoplastic cells between tumors with high-intensity tumor budding versus low-intensity or no tumor budding. In the samples of high-intensity budding, differences in those parameters between the​​ budding area and the area outside the budding were also evaluated. Furthermore, the study assessed differences in LVD and in the expression of podoplanin in neoplastic cells concerning OSCC clinicopathological characteristics.

METHODS

To those ends, we subjected 150 samples of OSCC to immunohistochemistry to evaluate the intensity of tumor budding (via multi-cytokeratin immunostaining). Moreover, the 150 samples of OSCC and 15 specimens of normal oral mucosa (used as a control) were employed to assess LVD and the expression of podoplanin (in neoplastic cells of OSCC and in the lining epithelium of normal oral mucosa), both via podoplanin immunostaining. Data were processed into descriptive and analytical statistics.

RESULTS

No differences were observed neither in the LVD nor in the expression of podoplanin in neoplastic cells concerning sex, age, tobacco smoking, tumor location and tumor size. The LVD was greater in OSCC and in tumors with high-intensity budding than in normal mucosa but did not differ between normal mucosa and tumors with low-intensity or no tumor budding. The data analyses also revealed that LVD was greater in tumors with high-intensity tumor budding than in tumors with low-intensity or no budding and showed no difference in LVD between the budding area and the area outside the budding. When compared to the lining epithelium of the normal mucosa, the expression of podoplanin was greater in neoplastic cells of OSCC, tumors with high-intensity budding and tumors with low-intensity or no tumor budding. The expression of podoplanin in neoplastic cells was also greater in tumors with high-intensity budding and, within those tumors, greater in the budding area than in the area outside de budding.

CONCLUSION

Those findings support the hypothesis that tumor budding is a biological phenomenon associated with the progression and biological behavior of OSCC.

Current Understanding of Pathological Mechanisms of Lymphedema

Significance: Lymphedema is a common disease that affects hundreds of millions of people worldwide with significant financial and social burdens. Despite increasing prevalence and associated morbidities, the mainstay treatment of lymphedema is largely palliative without an effective cure due to incomplete understanding of the disease. Recent Advances: Recent studies have described key histological and pathological processes that contribute to the progression of lymphedema, including lymphatic stasis, inflammation, adipose tissue deposition, and fibrosis. This review aims to highlight cellular and molecular mechanisms involved in each of these pathological processes. Critical Issues: Despite recent advances in the understanding of the pathophysiology of lymphedema, cellular and molecular mechanisms underlying the disease remains elusive due to its complex nature. Future Directions: Additional research is needed to gain a better insight into the cellular and molecular mechanisms underlying the pathophysiology of lymphedema, which will guide the development of therapeutic strategies that target specific pathology of the disease.

Lack of relationship between PROX1 expression and clinicopathological parameters and prognosis in gastric cancer patients: a meta-analysis and TCGA analysis

Background

The relationship between PROX1 expression and clinicopathological characteristics and prognosis in patients with gastric cancer (GC) remain controversial. The aim of this study is to determine the clinicopathological and prognostic significance of PROX1 expression in patients with GC.

Methods

A systematic literature search and meta-analysis were performed. Odds ratio (OR) and confidence interval (CI) were used to evaluated the relationship between PROX1 expression and clinicopathological characteristics and overall survival (OS) of GC patients. Additionally, the Cancer Genome Atlas (TCGA) and the Genotype-Tissue Expression (GTEx) datasets were utilized to examine the relationship between PROX1 expression and clinicopathological significance and OS in GC patients.

Results

A total of 8 studies pooling 1289 GC patients were included in the assessment. In GC patients, PROX1 expression was not related to gender (OR: 1.234, 95% CI 0.958–1.590, P = 0.104), depth of tumor invasion (OR: 0.742, 95% CI 0.428–1.287, P = 0.289), lymph node metastasis (OR: 2.161, 95% CI 0.808–5.779, P = 0.125), TNM stage (OR: 1.324, 95% CI 0.572–3.066, P = 0.513), tumor size (OR: 0.889, 95% CI 0.502–1.576, P = 0.687), distant metastasis (OR: 1.096, 95% CI 0.470–2.555, P = 0.763). In addition, we also found that PROX1 expression was not associated with 1-year OS (OR: 0.908, 95% CI 0.631–1.306, P = 0.602), 3-year OS (OR: 1.234, 95% CI 0.482–3.160, P = 0.661) and 5-year OS (OR: 0.853, 95% CI 0.266–2.736, P = 0.790). According to TCGA, in comparison with high and low PROX1 expression in GC patients, the OS did not differ statistically (p = 0.119).

Conclusion

The expression of PROX1 was shown to lack a significant relationship to gender, TNM stage, depth of invasion, tumor size, stage, distant metastasis, or lymph node metastasis in statistically. The expression of PROX1 was not related to OS and it failed to be a meaningful biomarker to prevent and diagnose GC.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12876-022-02229-6.

Leukocyte Trafficking via Lymphatic Vessels in Atherosclerosis

In recent years, lymphatic vessels have received increasing attention and our understanding of their development and functional roles in health and diseases has greatly improved. It has become clear that lymphatic vessels are critically involved in acute and chronic inflammation and its resolution by supporting the transport of immune cells, fluid, and macromolecules. As we will discuss in this review, the involvement of lymphatic vessels has been uncovered in atherosclerosis, a chronic inflammatory disease of medium- and large-sized arteries causing deadly cardiovascular complications worldwide. The progression of atherosclerosis is associated with morphological and functional alterations in lymphatic vessels draining the diseased artery. These defects in the lymphatic vasculature impact the inflammatory response in atherosclerosis by affecting immune cell trafficking, lymphoid neogenesis, and clearance of macromolecules in the arterial wall. Based on these new findings, we propose that targeting lymphatic function could be considered in conjunction with existing drugs as a treatment option for atherosclerosis.

Association of VEGFA, TIMP-3, and IL-6 gene polymorphisms with predisposition to optic neuritis and optic neuritis with multiple sclerosis

BACKGROUND

The etiology of the inflammatory ON is multifactorial. Much attention is paid to the inflammatory and immune processes that are likely to contribute to the demyelination and MS development. IL-6, VEGFA, and TIMP-3 genes are thought to be involved in the inflammatory processes and manifestation of CNS demyelination, so we aimed to determine the relationship between VEGFA rs1413711, TIMP-3 rs9621532, IL-6 rs1800796 gene polymorphisms and ON, and ON with MS.

MATERIALS AND METHODS

Patients with ON, ON with MS, and a random sample of healthy population were enrolled. The genotyping of VEGFA rs1413711, TIMP-3 rs9621532, and IL-6 rs1800796 polymorphisms was carried out using the real-time polymerase chain reaction method.

RESULTS

T/C and C/C genotypes of VEGFA rs1413711 were associated with about threefold increased odds of developing ON in the dominant and codominant models. Each allele C at VEGFA rs1413711 was associated with 1.7-fold increased odds of ON development. IL-6 rs1800796 allele C was more frequent in the ON with MS group compared to the control: 17.6% vs. 7.5%, respectively (p = .040). No statistically significant associations were found between TIMP-3 rs9621532 and the ON development.

CONCLUSION: VEGFA

rs1413711 is associated with the ON development.

Evolutionary approaches in protein engineering towards biomaterial construction

The tailoring of proteins for specific applications by evolutionary methods is a highly active area of research. Rational design and directed evolution are the two main strategies to reengineer proteins or create chimeric structures. Rational engineering is often limited by insufficient knowledge about proteins' structure-function relationships; directed evolution overcomes this restriction but poses challenges in the screening of candidates. A combination of these protein engineering approaches will allow us to create protein variants with a wide range of desired properties. Herein, we focus on the application of these approaches towards the generation of protein biomaterials that are known for biodegradability, biocompatibility and biofunctionality, from combinations of natural, synthetic, or engineered proteins and protein domains. Potential applications depend on the enhancement of biofunctional, mechanical, or other desired properties. Examples include scaffolds for tissue engineering, thermostable enzymes for industrial biocatalysis, and other therapeutic applications.

Lymphatic Function and Dysfunction in the Context of Sex Differences

Endothelial cells are the building blocks of the blood vascular system and exhibit well-characterized sexually dimorphic phenotypes with regard to chromosomal and hormonal sex, imparting innate genetic and physiological differences between male and female vascular systems and cardiovascular disease. However, even though females are predominantly affected by disorders of lymphatic vascular function, we lack a comprehensive understanding of the effects of sex and sex hormones on lymphatic growth, function, and dysfunction. Here, we attempt to comprehensively evaluate the current understanding of sex as a biological variable influencing lymphatic biology. We first focus on elucidating innate and fundamental differences between the sexes in lymphatic function and development. Next, we delve into lymphatic disease and explore the potential underpinnings toward bias prevalence in the female population. Lastly, we incorporate more broadly the role of the lymphatic system in sex-biased diseases such as cancer, cardiovascular disease, reproductive disorders, and autoimmune diseases to explore whether and how sex differences may influence lymphatic function in the context of these pathologies.

History and progress of hypotheses and clinical trials for Alzheimer's disease

Alzheimer's disease (AD) is a neurodegenerative disease characterized by progressive memory loss along with neuropsychiatric symptoms and a decline in activities of daily life. Its main pathological features are cerebral atrophy, amyloid plaques, and neurofibrillary tangles in the brains of patients. There are various descriptive hypotheses regarding the causes of AD, including the cholinergic hypothesis, amyloid hypothesis, tau propagation hypothesis, mitochondrial cascade hypothesis, calcium homeostasis hypothesis, neurovascular hypothesis, inflammatory hypothesis, metal ion hypothesis, and lymphatic system hypothesis. However, the ultimate etiology of AD remains obscure. In this review, we discuss the main hypotheses of AD and related clinical trials. Wealthy puzzles and lessons have made it possible to develop explanatory theories and identify potential strategies for therapeutic interventions for AD. The combination of hypometabolism and autophagy deficiency is likely to be a causative factor for AD. We further propose that fluoxetine, a selective serotonin reuptake inhibitor, has the potential to treat AD.

Molecular Signature of Prospero Homeobox 1 (PROX1) in Follicular Thyroid Carcinoma Cells

The prospero homeobox 1 (PROX1) transcription factor is a product of one of the lymphangiogenesis master genes. It has also been suggested to play a role in carcinogenesis, although its precise role in tumour development and metastasis remains unclear. The aim of this study was to gain more knowledge on the PROX1 function in thyroid tumorigenesis. Follicular thyroid cancer-derived cells—CGTH-W-1—were transfected with PROX1-siRNA (small interfering RNA) and their proliferation, cell cycle, apoptosis and motility were then analysed. The transcriptional signature of PROX1 depletion was determined using RNA-Sequencing (RNA-Seq) and the expression of relevant genes was further validated using reverse transcriptase quantitative PCR (RT-qPCR), Western blot and immunocytochemistry. PROX1 depletion resulted in a decreased cell motility, with both migratory and invasive potential being significantly reduced. The cell morphology was also affected, while the other studied cancer-related cell characteristics were not significantly altered. RNA-seq analysis revealed significant changes in the expression of transcripts encoding genes involved in both motility and cytoskeleton organization. Our transcriptional analysis of PROX1-depleted follicular thyroid carcinoma cells followed by functional and phenotypical analyses provide, for the first time, evidence that PROX1 plays an important role in the metastasis of thyroid cancer cells by regulating genes involved in focal adhesion and cytoskeleton organization in tumour cells.

Tumor-associated macrophages: a short compendium

Macrophages play an important role in tissue development and homeostasis. They serve as a nexus between adaptive and innate immunity, and employ considerable plasticity. In cancer, they play a pivotal role in chronic inflammation and tumor growth either by directly stimulating the proliferation of cancer cells or by producing angiogenic and lymphangiogenic factors. Although numerous immune cells play an important role in the tumor microenvironment, tumor-associated macrophages (TAMs) are by far the most extensively studied. A better understanding of the role of TAMs in mediating chemo- and radiotherapy resistance and suppressing immunosurveillance has led to numerous strategies targeting TAMs as an anticancer therapy either by targeting them directly or by polarizing TAMs toward a tumoricidal phenotype.

Regulation of Blood and Lymphatic Vessels by Immune Cells in Tumors and Metastasis

Research over the last decades has provided strong evidence for the pivotal role of the tumor-associated blood and lymphatic vasculature in supporting immunoevasion and in subverting T cell-mediated immunosurveillance. Conversely, tumor blood and lymphatic vessel growth is in part regulated by the immune system, with infiltrating innate as well as adaptive immune cells providing both immunosuppressive and various angiogenic signals. Thus, tumor angiogenesis and escape of immunosurveillance are two cancer hallmarks that are tightly linked and interregulated by cell constituents from compartments secreting both chemokines and cytokines. In this review, we discuss the implication and regulation of innate and adaptive immune cells in regulating blood and lymphatic angiogenesis in tumor progression and metastases. Moreover, we also highlight novel therapeutic approaches that target the tumor vasculature as well as the immune compartment to sustain and improve therapeutic efficacy in cancer.

The Lymphatic Fluid

This review will highlight our current understanding of the formation, circulation, and immunological role of lymphatic fluid. The formation of the extracellular fluid depends on the net balance between the hydrostatic and osmotic pressure gradients effective in the capillary beds. Lymph originates from the extracellular fluid and its composition combines the ultrafiltrated plasma proteins with the proteome generated by the metabolic activities of each parenchymal tissue. Several analyses have indicated how the lymph composition reflects the organs' physiological and pathological states. The collected lymphatic fluid moves from the capillaries into progressively larger collectors toward the draining lymph node aided by the lymphangion contractility and unidirectional valves, which prevent backflow. The proteomic composition of the lymphatic fluid is reflected in the MHC II peptidome presented by nodal antigen-presenting cells. Taken together, the past few years have generated new interest in the formation, transport, and immunological role of the lymphatic fluid.

An Important Role of VEGF-C in Promoting Lymphedema Development

Secondary lymphedema is a common complication after cancer treatment, but the pathomechanisms underlying the disease remain unclear. Using a mouse tail lymphedema model, we found an increase in local and systemic levels of the lymphangiogenic factor vascular endothelial growth factor (VEGF)-C and identified CD68⁺ macrophages as a cellular source. Surprisingly, overexpression of VEGF-C in a transgenic mouse model led to aggravation of lymphedema with increased immune cell infiltration and vascular leakage compared with wild-type littermates. Conversely, blockage of VEGF-C by overexpression of soluble VEGF receptor-3 reduced edema development, diminishing inflammation and blood vascular leakage. Similar findings were obtained in a hind limb lymph node excision lymphedema model. Flow cytometry analyses and immunofluorescence stainings in lymphedematic tissue showed that VEGF receptor-3 expression was restricted to lymphatic endothelial cells. Our data suggest that endogenous VEGF-C causes blood vascular leakage and fluid influx into the tissue, thus actively contributing to edema formation. These data may provide the basis for future clinical therapeutic approaches.

Sulfatase 2 facilitates lymphangiogenesis in breast cancer by regulating VEGF-D

In our previous studies, sulfatase 2 (Sulf2) was found to upregulate vascular endothelial growth factor-D (VEGF-D) expression in breast cancer. As VEGF-D plays an important role in lymphangiogenesis, we hypothesized that Sulf2 facilitates lymphangiogenesis in breast cancer by regulating VEGF-D. To evaluate the functions of Sulf2 on lymphangiogenesis in breast cancer, proliferation, apoptosis, cell cycle, cell mobility and tube-formation of lymphatic endothelial cells (LECs) were measured in vitro. Lymphangiogenesis in nude mouse ears and breast cancer xenografts were examined in vivo. Furthermore, the expression levels of related signaling pathway genes were screened and verified in LECs. We found that Sulf2 significantly increased the mobility and tube formation of the LECs, inhibited cisplatin-induced LEC apoptosis, but had no effect on cell proliferation and the cell cycle. Moreover, recombinant Sulf2 (rSulf2) combined with VEGF-D further promoted the proliferation, cell cycle, mobility and tube-like structure formation in the LECs, and at the same time inhibited cisplatin-induced apoptosis especially in the late stage. Sulf2 also significantly increased the density of lymphatic vessels in mouse ears and breast cancer xenografts in vivo. AKT1 was also shown to be upregulated and activated by Sulf2. Our results confirmed that Sulf2 facilitated lymphangiogenesis in breast cancer cells by regulating VEGF-D and that the AKT1-related signaling pathway was involved.

Circulating Angiogenic Factors as Biomarkers of Disease Severity and Bacterial Burden in Pulmonary Tuberculosis

BACKGROUND

Angiogenesis and lymphangiogenesis are classical features of granuloma formation in pulmonary tuberculosis (PTB). In addition, the angiogenic factor--VEGF-A is a known biomarker for PTB.

AIMS/METHODOLOGY

To examine the association of circulating angiogenic factors with PTB, we examined the systemic levels of VEGF-A, VEGF-C, VEGF-D, VEGF-R1, VEGF-R2 and VEGF-R3in individuals with PTB, latent TB (LTB) or no TB infection (NTB).

RESULTS

Circulating levels of VEGF-A, VEGF-C andVEGF-R2 were significantly higher in PTB compared to LTB or NTB individuals. Moreover, the levels of VEGF-A, VEGF-C and VEGF-R2 were significantly higher in PTB with bilateral and/or cavitary disease. The levels of these factors also exhibited a significant positive relationship with bacterial burdens in PTB. ROC analysis revealed VEGF-A and VEGF-R2 as markers distinguishing PTB from LTB or NTB. Finally, the circulating levels of all the angiogenic factors examined were significantly reduced following successful chemotherapy.

CONCLUSION

Therefore, our data demonstrate that PTB is associated with elevated levels of circulating angiogenic factors, possibly reflecting vascular and endothelial dysfunction. In addition, some of these circulating angiogenic factors could prove useful as biomarkers to monitor disease severity, bacterial burden and therapeutic responses.

Vascular endothelial growth factor C disrupts the endothelial lymphatic barrier to promote colorectal cancer invasion

BACKGROUND & AIMS

Colorectal cancer (CRC) is highly metastatic. Metastases spread directly into local tissue or invade distant organs via blood and lymphatic vessels, but the role of lymphangiogenesis in CRC progression has not been determined. Lymphangiogenesis is induced via vascular endothelial growth factor C (VEGFC) activation of its receptor, VEGFR3; high levels of VEGFC have been measured in colorectal tumors undergoing lymphangiogenesis and correlated with metastasis. We investigated VEGFC signaling and lymphatic barriers in human tumor tissues and mice with orthotopic colorectal tumors.

METHODS

We performed immunohistochemical, immunoblot, and real-time polymerase chain reaction analyses of colorectal tumor specimens collected from patients; healthy intestinal tissues collected during operations of patients without CRC were used as controls. CT26 CRC cells were injected into the distal posterior rectum of BALB/c-nude mice. Mice were given injections of an antibody against VEGFR3 or an adenovirus encoding human VEGFC before orthotopic tumors and metastases formed. Lymph node, lung, and liver tissues were collected and evaluated by flow cytometry. We measured expression of vascular endothelial cadherin (CDH5) on lymphatic vessels in mice and in human intestinal lymphatic endothelial cells.

RESULTS

Levels of podoplanin (a marker of lymphatic vessels), VEGFC, and VEGFR3 were increased in colorectal tumor tissues, compared with controls. Mice that expressed VEGFC from the adenoviral vector had increased lymphatic vessel density and more metastases in lymph nodes, lungs, and livers, compared with control mice. Anti-VEGFR3 antibody reduced numbers of lymphatic vessels in colons and prevented metastasis. Expression of VEGFC compromised the lymphatic endothelial barrier in mice and endothelial cells, reducing expression of CDH5, increasing permeability, and increasing trans-endothelial migration by CRC cells. Opposite effects were observed in mice and cells when VEGFR3 was blocked.

CONCLUSIONS

VEGFC signaling via VEGFR3 promotes lymphangiogenesis and metastasis by orthotopic colorectal tumors in mice and reduces lymphatic endothelial barrier integrity. Levels of VEGFC and markers of lymphatic vessels are increased in CRC tissues from patients, compared with healthy intestine. Strategies to block VEGFR3 might be developed to prevent CRC metastasis in patients.

Expression of lymphatic markers and lymphatic growth factors in psoriasis before and after anti-TNF treatment

BACKGROUND

Angiogenesis is an early stage of psoriatic lesion development, but less is known about lymphagiogenesis and its role in the development of psoriasis.

OBJECTIVE

To examine the expression of specific lymphatic markers and lymphatic growth factors in untreated psoriatic skin, in the unaffected skin of patients and skin of healthy volunteers, as well as their alteration after treatment with an anti-TNF agent.

METHODS

Immunohistochemistry for the lymphatic markers D2-40 and LYVE-1, in addition to the VEGF-C and VEGF-D growth factors, was performed in the skin biopsies of psoriatic lesions and adjacent non-psoriatic skin of 19 patients before and after treatment with etanercept, as well as in the skin biopsies of 10 healthy volunteers.

RESULTS

The expressions of D2-40, VEGF-C and VEGF-D on lymphatic vessels underwent statistically significant increases in untreated psoriatic skin compared with non-lesional skin, in contrast to LYVE-1, which did not involve significant increase in expression in psoriatic skin. VEGF-C expression on lymphatic vessels diminished after treatment with etanercept. Moreover VEGF-C and VEGF-D staining on fibroblasts presented with higher expression in lesional skin than in non-lesional adjacent skin.

CONCLUSION

Remodeling of lymphatic vessels possibly occurs during psoriatic lesion development, parallel to blood vessel formation. The exact role of this alteration is not yet clear and more studies are necessary to confirm these results.

The mRNA expressions and immunohistochemistry of factors involved in angiogenesis and lymphangiogenesis in the early stage of rat skin incision wounds

Wound healing evaluation is important in forensic pathology, in which angiogenesis plays an important role. We have already shown that vascular endothelial growth factor A (VEGF) is produced in the rat skin incision wounds by neutrophils, endothelial cells, and fibroblasts. In this study, we assessed the changes in the mRNA expressions of various factors possibly involved in angiogenesis including angiopoietin (ANGPT) 1 and 2, cadherin 5 (CDH5), granulocyte-macrophage colony stimulating factor (CSF2/GM-CSF), granulocyte colony stimulating factor (CSF3/G-CSF), chemokine (C-X-C motif) ligand 2 (CXCL2), chemokine (C-X-C motif) ligand12 (CXCL12/SDF1), endothelin 1 (ET1), fibroblast growth factor 1 (FGF 1), hepatocyte growth factor (HGF), hypoxia inducible factor 1 alpha (HIF1a), leptin, matrix metallopepitidase 9 (MMP9), serpine/plasminogen activator inhibitor1 (PAI1), platelet-derived growth factor-A (PDGF-A), transforming growth factor alpha and beta 1 (TGFa and b1), tenomodulin (TNMD), and troponin I type 2 (TNNI2) in the early stage of the rat skin incision wounds by real time RT-PCR. Factors reported to be involved in lymphangiogenesis such as fibroblast growth factor 2 (FGF 2), c-fos induced growth factor (FIGF/VEGF-D), forkhead box C2 (FOXC2), and prospero homeobox 1 (PROX1) were also studied. One and 3 days after the dorsal skin incisions, wounds on male Sprague-Dawley rats showed the statistically significant increases in the mRNA expressions for CXCL2, CSF3, MMP9, PAI1, and CSF2, whereas TGFa, TNNI2, FGF1, TNMD, leptin, and CXCL12 showed the statistically significant decreases. Interestingly, lymphgangiogenic factors FOXC2, PROX1, and FGF2 also showed the statistically significant decreases. In situ hybridization and immunohistochemistry showed the mRNA and protein positivity in endothelial cells, fibroblasts, and some leukocytes at the bottom of the wound tissue for PAI1, CSF3, and MMP9, 1 day after the skin incisions. Our novel findings show the possible involvement of several factors involved in angiogenesis and lymphangiogenesis in the early stage of wound healing process, which may be useful for forensic wound evaluations.

Generation of conditional alleles for Foxc1 and Foxc2 in mice

The Forkhead box transcription factors, Foxc1 and Foxc2, are crucial for development of the eye, cardiovascular network, and other physiological systems, but their cell-type specific and postdevelopmental functions are unknown, in part because conventional (i.e., whole-organism) homozygous-null mutations of either factor result in perinatal death. Here, we describe the generation of mice with conditional-null Foxc1(flox) and Foxc2(flox) mutations that are induced via Cre-mediated recombination. Mice homozygous for the unrecombined alleles are viable and fertile, indicating that the conditional alleles retain their wild-type function. The embryos of Foxc1(flox) or Foxc2(flox) mice crossed with Cre-deleter mice that are homozygous for the recombined allele (i.e., Foxc1(Δ/Δ) or Foxc2(Δ/Δ) embryos) lack expression of the corresponding gene and show the same developmental defects observed in conventional homozygous mutant embryos. We expect these conditional mutations to enable characterization of the cell-type specific functions of Foxc1 and Foxc2 in development, disease, and adult animals.

Diverse roles for VEGF-A in the nervous system

Vascular endothelial growth factor A (VEGF-A) is best known for its essential roles in blood vessel growth. However, evidence has emerged that VEGF-A also promotes a wide range of neuronal functions, both in vitro and in vivo, including neurogenesis, neuronal migration, neuronal survival and axon guidance. Recent studies have employed mouse models to distinguish the direct effects of VEGF on neurons from its indirect, vessel-mediated effects. Ultimately, refining our knowledge of VEGF signalling pathways in neurons should help us to understand how the current use of therapeutics targeting the VEGF pathway in cancer and eye disease might be expanded to promote neuronal health and nerve repair.

Effect of standard tuberculosis treatment on plasma cytokine levels in patients with active pulmonary tuberculosis

BACKGROUND

Sputum Mycobacterium tuberculosis (Mtb) culture is commonly used to assess response to antibiotic treatment in individuals with pulmonary tuberculosis (TB). Such techniques are constrained by the slow growth rate of Mtb, and more sensitive methods to monitor Mtb clearance are needed. The goal of this study was to evaluate changes in plasma cytokines in patients undergoing treatment for TB as a means of identifying candidate host markers associated with microbiologic response to therapy.

METHODS

Twenty-four plasma cytokines/chemokines were measured in 42 individuals diagnosed with active pulmonary TB, 52% were HIV co-infected. Individuals, undergoing a 26-week standard TB treatment, were followed longitudinally over 18 months and measurements were associated with HIV status and rates of sputum culture conversion.

RESULTS

Plasma concentrations of interferon-inducible protein-10 (IP-10) and vascular endothelial growth factor (VEGF) were significantly reduced upon TB treatment, regardless of HIV status. By the end of treatment, IP-10 concentrations were significantly lower in HIV negative individuals when compared to HIV-positive individuals (p = 0.02). Moreover, in HIV negative patients, plasma VEGF concentrations, measured as early as 2-weeks post TB treatment initiation, positively correlated with the time of sputum conversion (p = 0.0017). No significant changes were observed in other studied immune mediators.

CONCLUSIONS

These data suggest that VEGF plasma concentration, measured during early TB treatment, could represent a surrogate marker to monitor sputum culture conversion in HIV uninfected individuals.

Integrins and their extracellular matrix ligands in lymphangiogenesis and lymph node metastasis

In the 1970s, the late Judah Folkman postulated that tumors grow proportionately to their blood supply and that tumor angiogenesis removed this limitation promoting growth and metastasis. Work over the past 40 years, varying from molecular examination to clinical trials, verified this hypothesis and identified a host of therapeutic targets to limit tumor angiogenesis, including the integrin family of extracellular matrix receptors. However, the propensity for some tumors to spread through lymphatics suggests that lymphangiogenesis plays a similarly important role. Lymphangiogenesis inhibitors reduce lymph node metastasis, the leading indicator of poor prognosis, whereas inducing lymphangiogenesis promotes lymph node metastasis even in cancers not prone to lymphatic dissemination. Recent works highlight a role for integrins in lymphangiogenesis and suggest that integrin inhibitors may serve as therapeutic targets to limit lymphangiogenesis and lymph node metastasis. This review discusses the current literature on integrin-matrix interactions in lymphatic vessel development and lymphangiogenesis and highlights our current knowledge on how specific integrins regulate tumor lymphangiogenesis.

The EMILIN/Multimerin family

Elastin microfibrillar interface proteins (EMILINs) and Multimerins (EMILIN1, EMILIN2, Multimerin1, and Multimerin2) constitute a four member family that in addition to the shared C-terminus gC1q domain typical of the gC1q/TNF superfamily members contain a N-terminus unique cysteine-rich EMI domain. These glycoproteins are homotrimeric and assemble into high molecular weight multimers. They are predominantly expressed in the extracellular matrix and contribute to several cellular functions in part associated with the gC1q domain and in part not yet assigned nor linked to other specific regions of the sequence. Among the latter is the control of arterial blood pressure, the inhibition of Bacillus anthracis cell cytotoxicity, the promotion of cell death, the proangiogenic function, and a role in platelet hemostasis. The focus of this review is to highlight the multiplicity of functions and domains of the EMILIN/Multimerin family with a particular emphasis on the regulatory role played by the ligand-receptor interactions of the gC1q domain. EMILIN1 is the most extensively studied member both from the structural and functional point of view. The structure of the gC1q of EMILIN1 solved by NMR highlights unique characteristics compared to other gC1q domains: it shows a marked decrease of the contact surface of the trimeric assembly and while conserving the jelly-roll topology with two β-sheets of antiparallel strands it presents a nine-stranded β-sandwich fold instead of the usual 10-stranded fold. This is likely due to the insertion of nine residues that disrupt the ordered strand organization and forma a highly dynamic protruding loop. In this loop the residue E933 is the site of interaction between gC1q and the α4β1 and α9β1 integrins, and contrary to integrin occupancy that usually upregulates cell growth, when gC1q is ligated by the integrin the cells reduce their proliferative activity.

Understanding RAMPs through genetically engineered mouse models

The family of Receptor Activity Modifying Proteins (RAMPs) consists of three members, RAMP1, 2 and 3, which are each encoded by a separate gene and have diverse spatiotemporal expression patterns. Biochemical and pharmacological studies in cultured cells have shown that RAMPs can modulate several aspects of G receptor (GPCR) signaling, including receptor trafficking, ligand binding affinity, second messenger signaling and receptor desensitization. Moreover, these studies have shown that RAMPs can interact with several GPCRs other than the canonical calcitonin receptor-like receptor (CLR), with which they were first identified. Given these expanding roles for RAMPs, it becomes interesting to question how these biochemical and pharmacological properties bear significance in normal or disease physiology. To this end, several gene targeted knockout and transgenic models have been generated and characterized in recent years. Fortunately, they have each supported important roles for RAMPs during embryonic development and adulthood. This chapter provides a comprehensive overview of the most recent findings from gene targeted knockout mouse models and transgenic over-expression models, and gives special consideration to how comparative phenotyping approaches and conditional deletion strategies can be highly beneficial. In the future, these genetically engineered mouse models will provide both insights and tools for the exploitation of RAMP-based therapies for the treatment of human diseases.

Peripheral lymphangiogenesis in mice depends on ectodermal connexin-26 (Gjb2)

In order to study the specific function of connexin-26 (Cx26, also known as gap junction beta-2 protein; Gjb2), we generated knockin mice that expressed either a floxed lacZ reporter or, after Cre-mediated deletion, connexin-32 (Cx32)-coding DNA, both driven by the endogenous Cx26 promoter. Heterozygous Cx26knock-inCx32 (Cx26KICx32) embryos developed normally until embryonic day 14.5 but died before birth with severe lymphedemas. Although the jugular lymph sacs were normally developed, these embryos had a strongly reduced dermal lymphatic capillary network. By analyses of β-galactosidase reporter protein expression and lymphatic or blood endothelial-specific marker proteins, we demonstrated that Cx26 expression is temporally closely linked to lymphangiogenesis. No obvious phenotypic abnormalities were observed in Cx26KICx32 mice when Cre-mediated recombination was directed to mesenchyme or blood endothelium using the Prx1-Cre or Tie2-Cre mouse strains, respectively. By contrast, keratin-5-Cre-mediated replacement of Cx26 with Cx32 or deletion of both Cx26 alleles revealed severe lymphedemas similar to the general Cx26KICx32 phenotype. Thus, conditional ablation of Cx26 (loss of function) in ectoderm leads to partial disruption of lymphatic capillaries and embryonic death. We conclude that appropriate development of dermal lymphatic vessels in mice is dependent on the expression of Cx26 in the ectoderm.

The effects of vascular endothelial growth factor C knockdown in esophageal squamous cell carcinoma

PURPOSE

We investigated the role of vascular endothelial growth factor C (VEGF-C) in esophageal squamous cell carcinoma (ESCC) by knocking down VEGF-C expression in the ESCC cell line EC9706.

METHODS

Immunohistochemistry and in situ hybridization techniques were used to detect the expression of VEGF-C expression in ESCC tissues. We also investigated the relationship between VEGF-C expression and lymph node metastasis. We designed a siRNA expression plasmid for VEGF-C and transfected it into EC9706 cells. Stable clones were selected, and VEGF-C expression was analyzed by RT-PCR and western blotting. Cells were inoculated into nude mice. The expression of VEGF-C in the resulting tumors was analyzed by immunohistochemistry and in situ hybridization.

RESULTS

VEGF-C is highly expressed in ESCC and correlated with lymph node metastasis, as high levels were observed in patients presenting with lymph node metastases relative to those who did not (P < 0.01). Transfection with VEGF-C-siRNA decreased the expression of VEGF-C mRNA and protein. ESCC cells stably transfected with VEGF-C-siRNA expressed very low levels of VEGF-C (P < 0.01 compared with control). This knockdown effect persisted when the cells were inoculated into nude mice and allowed to form tumors.

CONCLUSIONS

The siRNA-targeted knockdown of VEGF-C led to a significant reduction in VEGF-C expression. This siRNA technique could be used for gene therapy in ESCC.

Lymphangiogenesis in post-natal tissue remodeling: lymphatic endothelial cell connection with its environment

The main physiological function of the lymphatic vasculature is to maintain tissue fluid homeostasis. Lymphangiogenesis or de novo lymphatic formation is closely associated with tissue inflammation in adults (i.e. wound healing, allograft rejection, tumor metastasis). Until recently, research on lymphangiogenesis focused mainly on growth factor/growth factor-receptor pathways governing this process. One of the lymphatic vessel features is the incomplete or absence of basement membrane. This close association of endothelial cells with the underlying interstitial matrix suggests that cell-matrix interactions play an important role in lymphangiogenesis and lymphatic functions. However, the exploration of interaction between extracellular matrix (ECM) components and lymphatic endothelial cells is in its infancy. Herein, we describe ECM-cell and cell-cell interactions on lymphatic system function and their modification occurring in pathologies including cancer metastasis.

Expression of lymphatic endothelium-specific hyaluronan receptor LYVE-1 in the developing mouse kidney

Our knowledge of the embryonic development of the lymphatic vessels within the kidney is limited. The aim of this study was to establish the time of appearance and the distribution of intra-renal lymphatic vessels in the developing mouse kidney by using the lymphatic marker, LYVE-1. Kidneys from embryonic day 12 (E12) to E18, from neonates at post-natal day 1 (P1) to P21, and from adults were studied. In the adult mouse kidney, LYVE-1 was expressed mainly in the lymphatic endothelial cells (LECs) and in a subset of endothelial cells in the glomerular capillaries. However, in the developing mouse kidney, LYVE-1 was also expressed transiently in F4/80(+)/CD11b(-) immature macrophages/dendritic cells and in the developing renal vein. LYVE-1(+) lymphatic vessels connected with extra-renal lymphatics were detected in the kidney at E13. F4/80(+)/CD11b(-)/LYVE-1(+) immature macrophages/dendritic cells appeared prior to the appearance of LYVE-1(+) renal lymphatic vessels and were closely intermingled or even formed part of the lymphatic vascular wall. Prox1 was expressed only in the LYVE-1(+) LECs from fetus to adult-hood, but not in LYVE-1(+) endothelial cells of the developing renal vein and macrophages/dendritic cells. Thus, lymphatic vessels of the kidney might originate by extension of extra-renal lymphatics through an active branching process possibly associated with F4/80(+)/CD11b(-)/LYVE-1(+) macrophages/dendritic cells.

Lymphatic system: a vital link between metabolic syndrome and inflammation

Metabolic syndrome is defined by a cluster of different metabolic risk factors that include overall and central obesity, elevated fasting glucose levels, dyslipidemia, hypertension, and intimal atherogenesis. Metabolic syndrome leads to increased risk for the development of type 2 diabetes and cardiovascular disease (e.g., heart disease and stroke). The exacerbated progression of metabolic syndrome to cardiovascular disease has lead to intense study of the physiological ramifications of metabolic syndrome on the blood vasculature. These studies have particularly focused on the signaling and architectural alterations that manifest in hypertension and atherosclerosis. However, despite the overlap of metabolic syndrome pathology with lymphatic function, tangent effects on the lymphatic system have not been extensively documented. In this review, we discuss the current status of metabolic syndrome and provide evidence for, and the remaining challenges in studying, the connections among the lymphatic system, lipid transport, obesity, insulin resistance, and general inflammation.

High matrix metalloproteinase-to-E-cadherin ratio measured by bicolor fluorescent in situ hybridization is associated with lymphangiogenesis and lymph node metastasis in prostate cancer

OBJECTIVE

The colorimetric in situ hybridization (CISH)-based matrix metalloproteinase (MMP)-to-E-cadherin (ECD) ratio (MER) has been revealed as an excellent marker for the disease stage in prostate cancer. The one aim of this study was investigating a new method for estimation of MER by bicolor fluorescent ISH (bicolor FISH) with a computerized fluorescence detector-based system. Another aim was examination of relation of MER by bicolor FISH with expression of vascular endothelial growth factor-C (VEGF-C).

METHODS

The bicolor FISH technique used cyanin 5 (cy5)-labeled MMP-2 and -9 probes, and a cyanin 3 (cy3)-labeled ECD probe on needle biopsy specimens from 67 prostate cancer cases. The ISH was followed by computerized detection of the signal intensities and cy5-to-cy3 ratios using a fluorescence detector. VEGF-C expression was examined using cy5-labeled VEGF-C by computerized detection.

RESULTS

The bicolor FISH-based MER was well correlated with CISH-based MER (P < 0.0001). The bicolor FISH-based MER correlated with Gleason score and pathologic stage of the cases. VEGF-C mRNA expression was associated with the pathologic stage and maximum lymph vessel density (LVD). The LVD was associated with VEGF-C expression at the tumor area where the maximum MER was detected (P < 0.0001).

CONCLUSION

The MER was correlated with the VEGF-C expression and LVD, indicating lymph node metastasis of prostate cancer. Therefore, this computer-assisted MER is a useful marker for preoperative prediction of disease stage, especially lymph node metastasis, of prostate cancer.

Lymphatic dysfunction, not aplasia, underlies Milroy disease

OBJECTIVE

Milroy disease is an inherited autosomal dominant lymphoedema caused by mutations in the gene for vascular endothelial growth factor receptor-3 (VEGFR-3, also known as FLT4). The phenotype has to date been ascribed to lymphatic aplasia. We further investigated the structural and functional defects underlying the phenotype in humans.

METHODS

The skin of the swollen foot and the non-swollen forearm was examined by (i) fluorescence microlymphangiography, to quantify functional initial lymphatic density in vivo; and (ii) podoplanin and LYVE-1 immunohistochemistry of biopsies, to quantify structural lymphatic density. Leg vein function was assessed by colour Doppler duplex ultrasound.

RESULTS

Milroy patients exhibited profound (86-91%) functional failure of the initial lymphatics in the foot; the forearm was unimpaired. Dermal lymphatics were present in biopsies but density was reduced by 51-61% (foot) and 26-33% (forearm). Saphenous venous reflux was present in 9/10 individuals with VEGFR3 mutations, including two carriers.

CONCLUSION

We propose that VEGFR3 mutations in humans cause lymphoedema through a failure of tissue protein and fluid absorption. This is due to a profound functional failure of initial lymphatics and is not explained by microlymphatic hypoplasia alone. The superficial venous valve reflux indicates the dual role of VEGFR-3 in lymphatic and venous development.

Can lymphangiosarcoma be resurrected? A clinicopathological and immunohistochemical study of lymphatic differentiation in 49 angiosarcomas

AIMS

The term lymphangiosarcoma has largely been abandoned in the current classification of endothelial neoplasms. Recently, a number of lymphatic-associated antibodies have been developed for immunohistochemistry, which frequently stain angiosarcomas, implying lymphatic or mixed lymphatic and blood vascular differentiation is common. The aim was to investigate further lymphatic antigen expression, and to explore the relation of immunohistochemistry to morphological and clinical findings.

METHODS AND RESULTS

Forty-nine angiosarcomas in tissue microarrays were analysed with D2-40 and antibodies to Prox-1 and vascular endothelial growth factor receptor (VEGFR)-3. D2-40 was positive in 53%, Prox-1 in 76%, and VEGFR-3 in 57%. Tumours with features attributable to lymphatic differentiation such as hobnail and kaposiform morphologies were more often positive with these markers, including a statistical association between D2-40 and hobnailing. Ten tumours had features suggestive of lymphatic differentiation, namely well-differentiated histology, interanastomosing channels devoid of red cells, prominent hobnailing, lymphoid aggregates, and multi-antigen expression of D2-40 (100%), Prox-1 (100%) and VEGFR-3 (60%), which might be deserving of the appellation lymphangiosarcoma. Nine were cutaneous scalp/facial tumours in elderly patients and one arose within chronic lymphoedema.

CONCLUSIONS

Lymphatic differentiation is common in angiosarcoma, certain subsets show greater lymphatic differentiation than others, and lymphangiosarcoma may be defined pathologically, rather than clinically.

Mechanism of lymph node metastasis in prostate cancer

Detection of lymph node metastases indicates poor prognosis for prostate cancer patients. Therefore, elucidation of the mechanism(s) of lymph node metastasis is important to understand the progression of prostate cancer and also to develop therapeutic interventions. In this article, the known mechanisms for lymph node metastasis are discussed and the involvement of lymphatic vessels in prostate cancer lymph node metastasis is comprehensively summarized. In addition, contradictory findings regarding the importance of lymphangiogenesis in facilitating lymph node metastasis in prostate cancer are pointed out and reconcilation is attempted.

Tbx1 regulates Vegfr3 and is required for lymphatic vessel development

Defects in lymphangiogenesis are added to the broad clinical manifestations of DiGeorge syndrome, caused by deletion of the T box transcription factor Tbx1.

Lymphatic dysfunction causes several human diseases, and tumor lymphangiogenesis is implicated in cancer spreading. TBX1 is the major gene for DiGeorge syndrome, which is associated with multiple congenital anomalies. Mutation of Tbx1 in mice recapitulates the human disease phenotype. In this study, we use molecular, cellular, and genetic approaches to show, unexpectedly, that Tbx1 plays a critical role in lymphatic vessel development and regulates the expression of Vegfr3, a gene that is essential for lymphangiogenesis. Tbx1 activates Vegfr3 transcription in endothelial cells (ECs) by binding to an enhancer element in the Vegfr3 gene. Conditional deletion of Tbx1 in ECs causes widespread lymphangiogenesis defects in mouse embryos and perinatal death. Using the mesentery as a model tissue, we show that Tbx1 is not required for lymphatic EC differentiation; rather, it is required for the growth and maintenance of lymphatic vessels. Our findings reveal a novel pathway for the development of the lymphatic vessel network.

Expression of PROX1 Is a common feature of high-grade malignant astrocytic gliomas

PROX1 is a prospero-related transcription factor that plays a critical role in the development of various organs including the mammalian lymphatic and central nervous systems; it controls cell proliferation and differentiation through different transcription pathwaysand has both oncogenic and tumor-suppressive functions. We investigated PROX1 expression patterns in 56 human astrocytic gliomas of different grades using immunohistochemistry. An average of 79% of cells in World Health Organization Grade IV (glioblastoma, n = 15) and 57% of cells in World Health Organization Grade III (anaplastic astrocytoma, n = 13) were strongly PROX1 positive; low-grade diffuse astrocytomas (Grade II, n = 13) had 21% of cells that were strongly positive; Grade I tumors (n = 15) had 1.5%; and non-neoplastic brain tissue (n = 15) had 3.7% of cells that were PROX1 positive. Double immunolabeling showed that PROX1+ cells in glioblastomas frequently coexpressed early neuronal proteins MAP2 and betaIII-tubulin but not the mature neuronal marker protein NeuN. Analyses of coexpression with proliferation markers suggest that PROX1+ cells have a marginally lower rate of proliferation than other tumor cells but are still mitotically active. We conclude that PROX1 may constitute a useful tool for the diagnosis and grading ofastrocytic gliomas and for distinguishing Grade III and Grade IV tumors from Grade I and Grade II tumors.

The tumor microenvironment in colorectal carcinogenesis

Colorectal cancer is the second leading cause of cancer-related mortality in the United States. Therapeutic developments in the past decade have extended life expectancy in patients with metastatic disease. However, metastatic colorectal cancers remain incurable. Numerous agents that were demonstrated to have significant antitumor activity in experimental models translated into disappointing results in extending patient survival. This has resulted in more attention being focused on the contribution of tumor microenvironment to the progression of a number of solid tumors including colorectal cancer. A more complete understanding of interactions between tumor epithelial cells and their stromal elements will enhance therapeutic options and improve clinical outcome. Here we will review the role of various stromal components in colorectal carcinogenesis and discuss the potential of targeting these components for the development of future therapeutic agents.

Novel aspects of corneal angiogenic and lymphangiogenic privilege

In this article, we provide the results of experimental studies demonstrating that corneal avascularity is an active process involving the production of anti-angiogenic factors, which counterbalance the pro-angiogenic/lymphangiogenic factors that are upregulated during wound healing. We also summarize pertinent published reports regarding corneal neovascularization (NV), corneal lymphangiogenesis and corneal angiogenic/lymphangiogenic privilege. We outline the clinical causes of corneal NV, and discuss the angiogenic proteins (VEGF and bFGF) and angiogenesis regulatory proteins. We also describe the role of matrix metalloproteinases MMP-2, -7, and MT1-MMP, anti-angiogenic factors, and lymphangiogenic regulatory proteins during corneal wound healing. Established and potential new therapies for the treatment of corneal neovascularization are also discussed.

Steroid-resistant lymphatic remodeling in chronically inflamed mouse airways

Angiogenesis and lymphangiogenesis participate in many inflammatory diseases, and their reversal is thought to be beneficial. However, the extent of reversibility of vessel remodeling is poorly understood. We exploited the potent anti-inflammatory effects of the corticosteroid dexamethasone to test the preventability and reversibility of vessel remodeling in Mycoplasma pulmonis-infected mice using immunohistochemistry and quantitative RT-PCR. In this model robust immune responses drive rapid and sustained changes in blood vessels and lymphatics. In infected mice not treated with dexamethasone, capillaries enlarged into venules expressing leukocyte adhesion molecules, sprouting angiogenesis and lymphangiogenesis occurred, and the inflammatory cytokines tumor necrosis factor and interleukin-1 increased. Concurrent dexamethasone treatment largely prevented the remodeling of blood vessels and lymphatics. Dexamethasone also significantly reduced cytokine expression, bacterial burden, and leukocyte influx into airways and lungs over 4 weeks of infection. In contrast, when infection was allowed to proceed untreated for 2 weeks and then was treated with dexamethasone for 4 weeks, most blood vessel changes reversed but lymphangiogenesis did not, suggesting that different survival mechanisms apply. Furthermore, dexamethasone significantly reduced the bacterial burden and influx of lymphocytes but not of neutrophils or macrophages or cytokine expression. These findings show that lymphatic remodeling is more resistant than blood vessel remodeling to corticosteroid-induced reversal. We suggest that lymphatic remodeling that persists after the initial inflammatory response has resolved may influence subsequent inflammatory episodes in clinical situations.

Linkage and sequence analysis indicate that CCBE1 is mutated in recessively inherited generalised lymphatic dysplasia

Generalised lymphatic dysplasia (GLD) is characterised by extensive peripheral lymphoedema with visceral involvement. In some cases, it presents in utero with hydrops fetalis. Autosomal dominant and recessive inheritance has been reported. A large, non-consanguineous family with three affected siblings with generalised lymphatic dysplasia is presented. One child died aged 5 months, one spontaneously miscarried at 17 weeks gestation, and the third has survived with extensive lymphoedema. All three presented with hydrops fetalis. There are seven other siblings who are clinically unaffected. Linkage analysis produced two loci on chromosome 18, covering 22 Mb and containing 150 genes, one of which is CCBE1. A homozygous cysteine to serine change in CCBE1 has been identified in the proband, in a residue that is conserved across species. High density SNP analysis revealed homozygosity (a region of 900 kb) around the locus for CCBE1 in all three affected cases. This indicates a likely ancestral mutation that is common to both parents; an example of a homozygous mutation representing Identity by Descent (IBD) in this pedigree. Recent studies in zebrafish have shown this gene to be required for lymphangiogenesis and venous sprouting and are therefore supportive of our findings. In view of the conserved nature of the cysteine, the nature of the amino acid change, the occurrence of a homozygous region around the locus, the segregation within the family, and the evidence from zebrafish, we propose that this mutation is causative for the generalised lymphatic dysplasia in this family, and may be of relevance in cases of non-immune hydrops fetalis.