Lymphatic endothelial cells, lymphedematous lymphangiogenesis, and molecular control of edema formation

Radiation therapy attenuates lymphatic vessel repair by reducing VEGFR-3 signalling

Introduction: Surgery and radiotherapy are key cancer treatments and the leading causes of damage to the lymphatics, a vascular network critical to fluid homeostasis and immunity. The clinical manifestation of this damage constitutes a devastating side-effect of cancer treatment, known as lymphoedema. Lymphoedema is a chronic condition evolving from the accumulation of interstitial fluid due to impaired drainage via the lymphatics and is recognised to contribute significant morbidity to patients who survive their cancer. Nevertheless, the molecular mechanisms underlying the damage inflicted on lymphatic vessels, and particularly the lymphatic endothelial cells (LEC) that constitute them, by these treatment modalities, remain poorly understood. Methods: We used a combination of cell based assays, biochemistry and animal models of lymphatic injury to examine the molecular mechanisms behind LEC injury and the subsequent effects on lymphatic vessels, particularly the role of the VEGF-C/VEGF-D/VEGFR-3 lymphangiogenic signalling pathway, in lymphatic injury underpinning the development of lymphoedema. Results: We demonstrate that radiotherapy selectively impairs key LEC functions needed for new lymphatic vessel growth (lymphangiogenesis). This effect is mediated by attenuation of VEGFR-3 signalling and downstream signalling cascades. VEGFR-3 protein levels were downregulated in LEC that were exposed to radiation, and LEC were therefore selectively less responsive to VEGF-C and VEGF-D. These findings were validated in our animal models of radiation and surgical injury. Discussion: Our data provide mechanistic insight into injury sustained by LEC and lymphatics during surgical and radiotherapy cancer treatments and underscore the need for alternative non-VEGF-C/VEGFR-3-based therapies to treat lymphoedema.

Drug-Related Lymphedema: Mysteries, Mechanisms, and Potential Therapies

The lymphatic circulation is an important component of the circulatory system in humans, playing a critical role in the transport of lymph fluid containing proteins, white blood cells, and lipids from the interstitial space to the central venous circulation. The efficient transport of lymph fluid critically relies on the rhythmic contractions of collecting lymph vessels, which function to "pump" fluid in the distal to proximal direction through the lymphatic circulation with backflow prevented by the presence of valves. When rhythmic contractions are disrupted or valves are incompetent, the loss of lymph flow results in fluid accumulation in the interstitial space and the development of lymphedema. There is growing recognition that many pharmacological agents modify the activity of ion channels and other protein structures in lymph muscle cells to disrupt the cyclic contraction and relaxation of lymph vessels, thereby compromising lymph flow and predisposing to the development of lymphedema. The effects of different medications on lymph flow can be understood by appreciating the intricate intracellular calcium signaling that underlies the contraction and relaxation cycle of collecting lymph vessels. For example, voltage-sensitive calcium influx through long-lasting ("L-type") calcium channels mediates the rise in cytosolic calcium concentration that triggers lymph vessel contraction. Accordingly, calcium channel antagonists that are mainstay cardiovascular medications, attenuate the cyclic influx of calcium through L-type calcium channels in lymph muscle cells, thereby disrupting rhythmic contractions and compromising lymph flow. Many other classes of medications also may contribute to the formation of lymphedema by impairing lymph flow as an off-target effect. The purpose of this review is to evaluate the evidence regarding potential mechanisms of drug-related lymphedema with an emphasis on common medications administered to treat cardiovascular diseases, metabolic disorders, and cancer. Additionally, although current pharmacological approaches used to alleviate lymphedema are largely ineffective, efforts are mounting to arrive at a deeper understanding of mechanisms that regulate lymph flow as a strategy to identify novel anti-lymphedema medications. Accordingly, this review also will provide information on studies that have explored possible anti-lymphedema therapeutics.

Aberrant stromal tissue factor localisation and mycolactone-driven vascular dysfunction, exacerbated by IL-1β, are linked to fibrin formation in Buruli ulcer lesions

Buruli ulcer (BU) is a neglected tropical disease caused by subcutaneous infection with Mycobacterium ulcerans and its exotoxin mycolactone. BU displays coagulative necrosis and widespread fibrin deposition in affected skin tissues. Despite this, the role of the vasculature in BU pathogenesis remains almost completely unexplored. We hypothesise that fibrin-driven ischemia can be an ‘indirect’ route to mycolactone-dependent tissue necrosis by a mechanism involving vascular dysfunction. Here, we tracked >900 vessels within contiguous tissue sections from eight BU patient biopsies. Our aim was to evaluate their vascular and coagulation biomarker phenotype and explore potential links to fibrin deposition. We also integrated this with our understanding of mycolactone’s mechanism of action at Sec61 and its impact on proteins involved in maintaining normal vascular function. Our findings showed that endothelial cell dysfunction is common in skin tissue adjacent to necrotic regions. There was little evidence of primary haemostasis, perhaps due to mycolactone-dependent depletion of endothelial von Willebrand factor. Instead, fibrin staining appeared to be linked to the extrinsic pathway activator, tissue factor (TF). There was significantly greater than expected fibrin staining around vessels that had TF staining within the stroma, and this correlated with the distance it extended from the vessel basement membrane. TF-induced fibrin deposition in these locations would require plasma proteins outside of vessels, therefore we investigated whether mycolactone could increase vascular permeability in vitro. This was indeed the case, and leakage was further exacerbated by IL-1β. Mycolactone caused the loss of endothelial adherens and tight junctions by the depletion of VE-cadherin, TIE-1, TIE-2 and JAM-C; all Sec61-dependent proteins. Taken together, our findings suggest that both vascular and lymphatic vessels in BU lesions become “leaky” during infection, due to the unique action of mycolactone, allowing TF-containing structures and plasma proteins into skin tissue, ultimately leading to local coagulopathy and tissue ischemia.

To date, the debilitating skin disease Buruli ulcer remains a public health concern and financial burden in low or middle-income countries, especially in tropical regions. Late diagnosis is frequent in remote areas, perhaps due to the painlessness of the disease. Hence patients often present with large, destructive opened ulcers leading to delayed wound closure or even lifelong disability. The infectious agent produces a toxin called mycolactone that drives the disease. We previously found evidence that the vascular system is disrupted by mycolactone in these lesions, and now we have further explored potential explanations for these findings by looking at the expression of vascular markers in BU. In a detailed analysis of patient skin punch biopsies, we identified distinct expression patterns of certain proteins and found that tissue factor, which initiates the so-called extrinsic pathway of blood clotting, is particularly important. Mycolactone is able to disrupt the barrier function of the endothelium, further aggravating the diseased phenotype, which may explain how clotting factors access the tissue. Altogether, such localised hypercoagulation in Buruli ulcer skin lesions may contribute to the development of the lesion.

Involvement of Sigma Receptor-1 in Lymphatic Endothelial Barrier Integrity and Bioenergetic Regulation

Background: Lymphatic endothelium plays significant roles in lymph transport and maintaining a barrier between the lymph and interstitial compartments. Lymphatic endothelial dysfunction is suspected to be a key factor in the pathogenesis of lymphatic diseases such as lymphedema. Sigma receptor-1 (σ1) was recently identified to promote endothelial-dependent production of nitric oxide and relaxation of collecting lymphatic vessels. In this study, we investigated the potential role of σ1 in lymphatic endothelial barrier function. Methods and Results: Cultured adult human dermal lymphatic endothelial cells (HDLEC) were grown into confluent monolayers. Transendothelial electrical resistance (TER) served as an index of barrier function. Glycolytic rate of HDLEC was determined with the Agilent Seahorse system. The σ1-selective agonist PRE-084 was used to test the impact of σ1 on HDLEC monolayer barrier function and endothelial bioenergetics, whereas the contribution of basal σ1 activity was assessed with small interfering RNA (siRNA)-mediated knockdown of σ1 expression. The ability of σ1 activation to counteract interleukin (IL)-1β-induced barrier dysfunction was also tested. The results show that PRE-084 increases HDLEC TER in a concentration-dependent manner, whereas reducing σ1 expression with siRNA decreases HDLEC TER. PRE-084 also enhances glycolytic rate parameters in HDLEC. Moreover, PRE-084 treatment partially counteracts IL-1β-induced HDLEC monolayer barrier dysfunction. Conclusions: Collectively, the results suggest that σ1 contributes to basal lymphatic endothelial barrier function, potentially through its ability to enhance glycolytic energy production. Our work also highlights the therapeutic potential of σ1 agonists for preventing lymphatic barrier dysfunction caused by inflammatory mediators.

Vegfc/d-dependent regulation of the lymphatic vasculature during cardiac regeneration is influenced by injury context

The lymphatic vasculature mediates essential physiological functions including fluid homeostasis, lipid and hormone transport, and immune cell trafficking. Recent studies have suggested that promoting lymphangiogenesis enhances cardiac repair following injury, but it is unknown whether lymphangiogenesis is required for cardiac regeneration. Here, we describe the anatomical distribution, regulation, and function of the cardiac lymphatic network in a highly regenerative zebrafish model system using transgenic reporter lines and loss-of-function approaches. We show that zebrafish lacking functional vegfc and vegfd signaling are devoid of a cardiac lymphatic network and display cardiac hypertrophy in the absence of injury, suggesting a role for these vessels in cardiac tissue homeostasis. Using two different cardiac injury models, we report a robust lymphangiogenic response following cryoinjury, but not following apical resection injury. Although the majority of mutants lacking functional vegfc and vegfd signaling were able to mount a full regenerative response even in the complete absence of a cardiac lymphatic vasculature, cardiac regeneration was severely impaired in a subset of mutants, which was associated with heightened pro-inflammatory cytokine signaling. These findings reveal a context-dependent requirement for the lymphatic vasculature during cardiac growth and regeneration.

Overexpression of Receptor Tyrosine Kinase EphB4 Triggers Tumor Growth and Hypoxia in A375 Melanoma Xenografts: Insights from Multitracer Small Animal Imaging Experiments

Experimental evidence has associated receptor tyrosine kinase EphB4 with tumor angiogenesis also in malignant melanoma. Considering the limited in vivo data available, we have conducted a systematic multitracer and multimodal imaging investigation in EphB4-overexpressing and mock-transfected A375 melanoma xenografts. Tumor growth, perfusion, and hypoxia were investigated by positron emission tomography. Vascularization was investigated by fluorescence imaging in vivo and ex vivo. The approach was completed by magnetic resonance imaging, radioluminography ex vivo, and immunohistochemical staining for blood and lymph vessel markers. Results revealed EphB4 to be a positive regulator of A375 melanoma growth, but a negative regulator of tumor vascularization. Resulting in increased hypoxia, this physiological characteristic is considered as highly unfavorable for melanoma prognosis and therapy outcome. Lymphangiogenesis, by contrast, was not influenced by EphB4 overexpression. In order to distinguish between EphB4 forward and EphrinB2, the natural EphB4 ligand, reverse signaling a specific EphB4 kinase inhibitor was applied. Blocking experiments show EphrinB2 reverse signaling rather than EphB4 forward signaling to be responsible for the observed effects. In conclusion, functional expression of EphB4 is considered a promising differentiating characteristic, preferentially determined by non-invasive in vivo imaging, which may improve personalized theranostics of malignant melanoma.

Diagnostic Accuracy of Clinical Measures Considering Segmental Tissue Composition and Volume Changes of Breast Cancer-Related Lymphedema

Background: If we use only volumetry for measuring lymphedema, we could underdiagnose lymphedema with characteristics of biomechanical changes without definite volume change, especially in the medial forearm.

Methods and Results: In total, 158 breast cancer patients participated in this study. Arm volume was measured by water displacement volumetry, and segmental volumes were calculated from circumferences by using the truncated cone method. Subcutaneous ultrasound echogenicities were assessed on the medial side of the upper arm and forearm of both arms and graded by subcutaneous echogenicity grade (SEG) and revised SEG (rSEG). The standards for diagnosing secondary lymphedema were according to the volume change and clinical stage. Sensitivity, specificity, receiver-operating characteristic (ROC) curve, and area under the curve (AUC) were used. Analysis of ROC curves yielded AUCs of 0.875–0.933 (p < 0.001). Volume differences in each segment were significantly different among the grades by SEG. The highest AUC was found for volume difference (AUC = 0.919, 95% confidence interval [CI] = 0.860–0.978) in the upper arm near the elbow; however, in the medial forearm, the highest AUC was found for rSEG (AUC = 0.948, 95% CI = 0.923–0.965 in the proximal forearm; AUC = 0.940, 95% CI = 0.923–0.965 in the distal forearm).

Conclusions: Our findings support the use of SEG by ultrasound in the assessment of lymphedema, especially in the medial region of the forearm. Subcutaneous ultrasound echogenicities may improve the accuracy of diagnosis of lymphedema in the forearm.

Giant lymphedema of the penis and scrotum: a case report

Lymphedema of the penis and scrotum is a rare entity characterized by enlargement of the skin and subcutaneous tissue of the genital region due to lymphatic drainage impairment. This clinical condition is more frequent in tropical countries due to a higher incidence of filariasis, which, in turn, is the main etiology. We describe the case of a 33-year-old man with large lymphedema of the scrotum and penis due to an acute and chronic inflammatory process, foreign body granuloma, and marked hyalinization. Four consecutive surgical interventions were necessary to remove the great part of the affected tissue, which enabled satisfactory results and improved the patient's quality of life.

Vascular endothelial growth factor (VEGF) levels in short, GH treated children: a distinct pattern of VEGF-C in Noonan syndrome

CONTEXT

Noonan syndrome (NS) is characterized by short stature and elevated risk of lymphedema. The mechanism underlying lymphedema may be mediated by vascular endothelial growth factors (VEGFs).

OBJECTIVE

To assess the effect of growth hormone (GH) treatment on plasma insulin-like growth factor (IGF)-1, VEGF-A and VEGF-C levels in patients with NS as compared to short GH-sufficient children.

DESIGN

Retrospective, comparative.

SETTING

Endocrinology department of a tertiary pediatric medical center.

PATIENTS AND METHODS

Plasma IGF-1, VEGF-A and VEGF-C levels were measured before and during GH treatment in 6 patients with NS and 18 age-matched short subjects (Turner, idiopathic short stature and small for gestational age).

MAIN OUTCOME MEASURES

Changes in plasma VEGF and IGF-1 levels.

RESULTS

Baseline IGF-1 SDS levels were slightly lower in NS patients compared with controls; IGF-1 response to GH therapy was markedly lower in NS patients compared with controls (p = 0.017). Mean baseline VEGF-A levels were similar in NS patients and controls whilst mean baseline VEGF-C levels were significantly lower in the NS group as compared with controls (p = 0.022). Plasma VEGF-A and VEGF-C levels did not significantly change during GH treatment in the study cohort. No correlation was found between VEGF-C levels and levels of IGF-1, VEGF-A and auxological parameters, either before or during GH administration.

CONCLUSION

Children with NS have a distinct growth factor profile including low basal VEGF-C and flattened IGF-1 response to GH. Further studies are needed to confirm our findings and to elucidate the interaction between VEGF-C levels and lymphedema.

Temporal and spatial regulation of epsin abundance and VEGFR3 signaling are required for lymphatic valve formation and function

Lymphatic valves prevent the backflow of the lymph fluid and ensure proper lymphatic drainage throughout the body. Local accumulation of lymphatic fluid in tissues, a condition called lymphedema, is common in individuals with malformed lymphatic valves. The vascular endothelial growth factor receptor 3 (VEGFR3) is required for the development of lymphatic vascular system. The abundance of VEGFR3 in collecting lymphatic trunks is high before valve formation and, except at valve regions, decreases after valve formation. We found that in mesenteric lymphatics, the abundance of epsin 1 and 2, which are ubiquitin-binding adaptor proteins involved in endocytosis, was low at early stages of development. After lymphatic valve formation, the initiation of steady shear flow was associated with an increase in the abundance of epsin 1 and 2 in collecting lymphatic trunks, but not in valve regions. Epsin 1 and 2 bound to VEGFR3 and mediated the internalization and degradation of VEGFR3, resulting in termination of VEGFR3 signaling. Mice with lymphatic endothelial cell-specific deficiency of epsin 1 and 2 had dilated lymphatic capillaries, abnormally high VEGFR3 abundance in collecting lymphatics, immature lymphatic valves, and defective lymph drainage. Deletion of a single Vegfr3 allele or pharmacological suppression of VEGFR3 signaling restored normal lymphatic valve development and lymph drainage in epsin-deficient mice. Our findings establish a critical role for epsins in the temporal and spatial regulation of VEGFR3 abundance and signaling in collecting lymphatic trunks during lymphatic valve formation.

New compression mechanism in penile-scrotal lymphedema and sexual rehabilitation

The objective of this study is to describe a new compression mechanism in the treatment of lymphedema of the penis and scrotum and the ensuing sexual rehabilitation. The patient, a 58-year-old man, had edema of the penile and scrotal region as a result of surgery of the pancreas and spleen and chemotherapy. The patient complained of pain, discomfort, and difficulties to walk and urinate. A clinical diagnosis of lymphedema of the penis and scrotum was reached. Treatment involved the continuous use of a cotton-polyester compression garment for the region together with thorough hygiene skin care. The swelling reduced significantly within a week to almost a normal aspect which was accompanied by clinical improvements of the symptoms. The reduction in penile edema allowed sexual rehabilitation even though erectile dysfunction required the use of a specific medication (sildenafil). In conclusion, simple and low-cost options can improve lymphedema of the penis and scrotum and allow sexual rehabilitation.

Adaptations in the treatment of congenital lymphedema centered on the quality of life

Case Description. This report describes the evolution, necessary adaptations, and complications in the treatment of a 9-year-old child with primary congenital lymphedema. Description of Intervention. The clinical treatment of lymphedema was started in the first year of the patient's life and for five years she was only treated using the Godoy & Godoy technique of cervical stimulation. Three years ago the patient was prescribed a compression stocking made from a cotton-polyester fabric (grosgrain) because of a sudden increase in the lymphedema after she started to take growth hormones. Outcome and Conclusion. The combination of cervical stimulation and a compression stocking was effective to keep the child's life relatively normal, performing all day-to-day and recreational activities.

Adiponectin-mediated modulation of lymphatic vessel formation and lymphedema

BACKGROUND

Obesity is linked with an increased risk of lymphedema, which is a serious clinical problem. Adiponectin is a circulating adipokine that is down-regulated in obese states. We investigated the effects of adiponectin on lymphatic vessel formation in a model of lymphedema and dissected its mechanisms.

METHODS AND RESULTS

A mouse model of lymphedema was created via ablation of tail surface lymphatic network. Adiponectin-knockout mice showed the greater diameter of the injured tail compared with wild-type mice, which was associated with lower numbers of lymphatic endothelial cells (LECs). Systemic delivery of adiponectin reduced the thickness of the injured tail and enhanced LEC formation in wild-type and adiponectin-knockout mice. Adiponectin administration also improved the edema of injured tails in obese KKAy mice. Treatment with adiponectin protein stimulated the differentiation of human LECs into tubelike structures and increased LEC viability. Adiponectin treatment promoted the phosphorylation of AMP-activated protein kinase (AMPK), Akt, and endothelial nitric oxide synthase n LECs. Blockade of AMPK or Akt activity abolished adiponectin-stimulated increase in LEC differentiation and viability and endothelial nitric oxide synthase phosphorylation. Inhibition of AMPK activation also suppressed adiponectin-induced Akt phosphorylation in LECs. In contrast, inactivation of Akt signaling had no effects on adiponectin-mediated AMPK phosphorylation in LECs. Furthermore, adiponectin administration did not affect the thickening of the damaged tail in endothelial nitric oxide synthase-knockout mice.

CONCLUSIONS

Adiponectin can promote lymphatic vessel formation via activation of AMPK/Akt/endothelial nitric oxide synthase signaling within LECs, thereby leading to amelioration of lymphedema.

Therapeutic lymphangiogenesis with implantation of adipose-derived regenerative cells

Background

Lymphedema is one of the serious clinical problems that can occur after surgical resection of malignant tumors such as breast cancer or intra‐pelvic cancers. However, no effective treatment options exist at present. Here, we report that implantation of adipose‐derived regenerative cells (ADRCs) can induce lymphangiogenesis in a mouse model of reparative lymphedema.

Methods and Results

ADRCs were isolated from C57BL/6J mice. To examine the therapeutic efficacy of ADRC implantation in vivo, we established a new mouse model of tail lymphedema. Lymphedema was improved significantly by local injection of ADRCs (P<0.05). Histological analysis revealed that lymphatic capillary density was greater in the ADRC group than in the phosphate‐buffered saline control group (P<0.01). Tissue expression of vascular endothelial growth factor C mRNA and plasma levels of vascular endothelial growth factor C were greater in the ADRC group than in the control group (P<0.01 and P<0.05, respectively). ADRCs released vascular endothelial growth factor C, which directly stimulated lymphangiogenesis. Implantation of ADRCs also enhanced recruitment of bone marrow–derived M2 macrophages, which served as lymphatic endothelial progenitor cells.

Conclusions

Implantation of autologous ADRCs could be a useful treatment option for patients with severe lymphedema via mediation of lymphangiogenesis. (J Am Heart Assoc. 2012;1:e000877 doi: 10.1161/JAHA.112.000877.)

Macrophages are important mediators of either tumor- or inflammation-induced lymphangiogenesis

The lymphatic system provides important functions for tissue fluid homeostasis and immune response. Lymphangiogenesis, the formation of new lymphatics, comprises a series of complex cellular events in vitro or in vivo, e.g., proliferation, differentiation, and sprouting. Recent evidence has implied that macrophages act as a direct structural contributor to lymphatic endothelial walls or secret VEGF-C/-D and VEGF-A to initiate lymphangiogenesis in inflamed or tumor tissues. Bone marrow-derived macrophages are versatile cells that express different functional programs in response to exposure to microenvironmental signals, and can be identified by specific expression of a number of proteins, F4/80, CD11b, and CD68. Several causative factors, e.g., NF-κB, IL-1β, TNF-α, SDF-1, M-CSF, especially TonEBP/VEGF-C signaling, may be actively involved in macrophage-induced lymphangiogenesis. Alteration of macrophage phenotype and function has a profound effect on the development and progression of inflammation and malignancy, and macrophage depletion for controlling lymphangiogenesis may provide a novel approach for prevention and treatment of lymphatic-associated diseases.

Differential cytokine responses in human and mouse lymphatic endothelial cells to cytokines in vitro

BACKGROUND

Inflammatory cytokines dysregulate microvascular function, yet how cytokines affect lymphatic endothelial cells (LEC) are unclear.

METHODS AND RESULTS

We examined effects of TNF-α, IL-1 beta, and IFN-gamma on LEC proliferation, endothelial cell adhesion molecule (ECAM) expression, capillary formation, and barrier changes in murine (SV-LEC) and human LECs (HMEC-1a).

RESULTS

All cytokines induced ICAM-1, VCAM-1, MAdCAM-1, and E-selectin in SV-LECs; TNF-α, IL-1 beta; and IFN-gamma induced ECAMs (but not MAdCAM-1) in HMEC-1a. IL-1 beta increased, while IFN-gamma and TNF-α reduced SV-LEC proliferation. While TNF-α induced, IFN-gamma decreased, and IL-1 beta did not show any effect on HMEC-1a proliferation. TNF-α, IL-1 beta, and IFN-gamma each reduced capillary formation in SV-LEC and in HMEC-1a. TNF-α and IL-1 beta reduced barrier in SV-LEC and HMEC-1a; IFN-gamma did not affect SV-LEC barrier, but enhanced HMEC-1a barrier. Inflammatory cytokines alter LEC growth, activation and barrier function in vitro and may disturb lymphatic clearance increasing tissue edema in vivo.

CONCLUSION

Therapies that maintain or restore lymphatic function (including cytokines blockade), may represent important strategies for limiting inflammation.

FOXC2 is a novel prognostic factor in human esophageal squamous cell carcinoma

BACKGROUND

FOXC2 has been implicated in cancer progression through its induction of epithelial-to-mesenchymal transition. We analyzed the clinical significance of FOXC2 in esophageal cancer cases, in which early distant metastasis or invasion to nearby organs is an obstacle to treatment.

METHODS

Quantitative reverse transcriptase-polymerase chain reaction was used to evaluate FOXC2 mRNA expression in 70 esophageal cancer cases to determine the clinicopathologic significance of FOXC2 expression. Furthermore, we examined associations between FOXC2 expression and matrix metalloproteinases 2 (MMP2) and matrix metalloproteinases 9 (MMP9). We also performed in vitro invasion and migration assays for FOXC2-suppressed esophageal cancer cells.

RESULTS

In clinicopathologic analysis, the high-FOXC2 expression group showed a higher incidence of advanced tumor stage, lymph node metastasis, and lymphatic invasion than the low-FOXC2 expression group (P < 0.05). In particular, tumor stage exhibited the most remarkable difference (P < 0.0001). Expression of MMP2 and MMP9 was far higher in the high-FOXC2 expression group. Furthermore, the high-FOXC2 expression group had a significantly poorer prognosis than did the low expression group (P = 0.006). Multivariate analysis indicated that high FOXC2 expression was an independent prognostic factor for survival. Suppression of FOXC2 expression altered the invasive and the migratory ability of esophageal cancer cells in vitro.

CONCLUSIONS

Our findings suggest that FOXC2 could be an important prognostic indicator for esophageal cancer patients. FOXC2 is directly involved in cancer progression and is associated with poor prognosis in esophageal cancer cases.

Multiple expressions of lymphatic markers and morphological evolution of newly formed lymphatics in lymphangioma and lymph node lymphangiogenesis

The rapid evolution of reliable technology combined with increasing number of specific markers for lymphatic endothelial cells (LECs) facilitates the investigation of lymphangiogenesis in developing and diseased tissues. Here, we injected incomplete Freund's adjuvant (IFA) peritoneally into BALB/c and nonobese diabetic (NOD) mice to induce lymphangioma and found atypical lymphatic accumulations with intervening fibrous tissue and lymphoid aggregates. Lymphatic markers, LYVE-1 and podoplanin, were used to specifically define the morphological features of the neoplastic lymphatics. The NOD mice (affected by an autoimmune disorder) had fewer and smaller lymphangiomas than the BALB/c mice. Injection of IFA in the footpad skin of the mice also disturbed draining regional lymph node lymphangiogenesis and caused enlargement of popliteal lymph nodes. Molecular analyses of the LECs indicated potential interventions for lymphangioma through vascular endothelial growth factor (VEGF)-A/-C/-D and their receptors, VEGF receptors-2/-3, and Prox-1 signaling pathways. These findings represent an important link between multiple factors and lymphatic disorders.

G protein-coupled receptors as potential drug targets for lymphangiogenesis and lymphatic vascular diseases

G protein-coupled receptors (GPCRs) are widely expressed cell surface receptors that have been successfully exploited for the treatment of a variety of human diseases. Recent studies in genetically engineered mouse models have led to the identification of several GPCRs important for lymphatic vascular development and function. The adrenomedullin receptor, which consists of an oligomer between calcitonin receptor-like receptor and receptor activity modifying protein 2, is required for normal lymphatic vascular development and regulates lymphatic capillary permeability in mice. Numerous studies also suggest that lysophospholipid receptors are involved in the development of lymphatic vessels and lymphatic endothelial cell permeability. Given our current lack of pharmacological targets for the treatment of lymphatic vascular diseases like lymphedema, the continued identification and study of GPCRs in lymphatic endothelial cells may eventually lead to major breakthroughs and new pharmacological strategies for the treatment of lymphedema.