Endostatin inhibits lymph node metastasis by a down-regulation of the vascular endothelial growth factor C expression in tumor cells

PEDF inhibits lymphatic metastasis of nasopharyngeal carcinoma as a new lymphangiogenesis inhibitor

Nasopharyngeal carcinoma (NPC) is one of the most malignant tumors in southern China and Asia, and lymph node metastasis is an important cause for treatment failure. Lymphangiogenesis is a crucial step in lymphatic metastasis of NPC, while little is known about lymphangiogenesis in NPC. Similar to angiogenesis, lymphangitic neovascularization is a process of balance between pro-lymphangiogenesis and anti-lymphangiogenesis factors, but there are few studies on endogenous lymphangiogenesis inhibitors. Pigment epithelium-derived factor (PEDF) is a well-known effective endogenous angiogenesis inhibitor. However, the relationship between PEDF and lymphangiogenesis remains unknown. Our present study reveals that PEDF is lowly expressed in human NPC tissues with poor prognosis and is negatively correlated with lymphatic vessel density (LVD). Consistently, PEDF inhibits lymphangiogenesis and lymphatic metastasis of NPC in vivo experiments. Mechanistically, PEDF inhibits the proliferation, migration, and tube formation of lymphatic endothelial cells and promotes cell apoptosis. On the other hand, PEDF reduces the expression and secretion of vascular endothelial growth factor C (VEGF-C) of NPC cells through the nuclear factor-κB (NF-κB) signaling pathway. Our findings indicate that PEDF plays a vital role in lymphatic metastasis by targeting both lymphatic endothelial cells and NPC cells, and PEDF may represent a novel therapeutic target for NPC.

Chemotherapy combined with Endostar as salvage treatment for EGFR-tyrosine kinase inhibitor primary resistance in an advanced non-small cell lung cancer patient with EGFR L858R mutation and ROS1 fusion: A case report

EGFR‐activating mutations have been recognized as the most important predictor of response to EGFR‐tyrosine kinase inhibitors (TKIs); however, 20–30% of patients harboring EGFR‐activating mutations show poor responses. The mechanisms of such EGFR‐TKI primary resistance are still poorly understood. In our case, a non‐small cell lung cancer patient developed intrinsic EGFR‐TKI resistance and was then confirmed to simultaneously harbor an L858R mutation and ROS1 rearrangement. Salvage chemotherapy plus Endostar showed enduring therapeutic effects, achieving a disease‐free survival period of 24 months and overall survival of 30 months. This suggests that co‐activation of different oncogenic signal pathways might be a potential mechanism of EGFR‐TKI primary resistance. Chemotherapy combined with anti‐angiogenesis should be considered an important salvage strategy. Further studies are warranted to verify these findings and explore the underlying mechanisms involved.

Current Status and Study Progress of Recombinant Human Endostatin in Cancer Treatment

Angiogenesis plays fundamentally critical roles in solid-tumor pathogenesis, growth, invasion and metastasis. Endostatin, one of the most potent anti-angiogenic factors, was first isolated in Folkman's lab in 1997, and was reported to dramatically shrink tumor blood formation. But its insoluble and unstable nature coupled with the high cost of synthesizing the endostatin protein doomed it for clinical cancer treatment. Intrigued by Folkman's pioneering discoveries, Chinese scientists found a way to refold the protein, making it cost-effective to manufacture a recombinant human endostatin, a soluble and stable form of endostatin. A number of clinical studies have demonstrated the significant survival benefit of rh-endostatin in treating late stage non-small-cell lung carcinoma (NSCLC) and, as a result, rh-endostatin (Endostar®) was approved by the State Food and Drug Administration of China (CFDA) in September of 2005 as a treatment option for NSCLC. Since then, increasing bodies of clinical data and experience have been obtained from a variety of other different cancers, such as small cell lung cancer, NSCLC in other settings, including malignant serous effusion, melanoma, colon cancer, gastric cancer, breast cancer, nasopharyngeal cancers, and others. This review aims at summarizing current clinical data of rh-endostatin including its survival benefits, optimized dosages, routes of administration, recommended duration and frequency of treatment, predictive biomarkers, and its safety profile in lung cancers as well as other cancers.

Effect of VEGF-C siRNA and endostatin on ring formation and proliferation of esophageal squamous cell carcinoma lymphatic endothelial cells

Objective

To study the effects of vascular endothelial growth factor C small interfering RNA and endostatin on esophageal squamous cell carcinoma-related ring formation in vitro and proliferation of lymphatic endothelial cells.

Materials and methods

KYSE150 cells were subjected to analysis of cell transfection and endostatin operation. The groups were as follows: negative group, blank group, negative plus endostatin group, endostatin group, SG1 group, SG2 group, SG1 plus endostatin group, and SG2 plus endostatin group. The esophageal cancer-related microlymphatic endothelial cells were three-dimensionally cultured. Cell Counting Kit-8 (CCK-8) assay was employed to detect cell proliferation.

Results

The negative group’s three-dimensional culture result was the highest, followed by the blank group, negative plus endostatin group, endostatin group, SG2 group, SG1 group, SG1 plus endostatin group, and SG2 plus endostatin group. The quantity of living cells in the blank group was the highest, followed by the negative control, endostatin, SG2, SG1, negative plus endostatin, SG1 plus endostatin, and SG2 plus endostatin groups.

Conclusion

Both vascular endothelial growth factor C small interfering RNA and endostatin could inhibit ring formation in esophageal squamous cell carcinoma and proliferation of lymphatic endothelial cells.

Endostatin's emerging roles in angiogenesis, lymphangiogenesis, disease, and clinical applications

BACKGROUND

Angiogenesis is the process of neovascularization from pre-existing vasculature and is involved in various physiological and pathological processes. Inhibitors of angiogenesis, administered either as individual drugs or in combination with other chemotherapy, have been shown to benefit patients with various cancers. Endostatin, a 20-kDa C-terminal fragment of type XVIII collagen, is one of the most potent inhibitors of angiogenesis.

SCOPE OF REVIEW

We discuss the biology behind endostatin in the context of its endogenous production, the various receptors to which it binds, and the mechanisms by which it acts. We focus on its inhibitory role in angiogenesis, lymphangiogenesis, and cancer metastasis. We also present emerging clinical applications for endostatin and its potential as a therapeutic agent in the form a short peptide.

MAJOR CONCLUSIONS

The delicate balance between pro- and anti-angiogenic factors can be modulated to result in physiological wound healing or pathological tumor metastasis. Research in the last decade has emphasized an emerging clinical potential for endostatin as a biomarker and as a therapeutic short peptide. Moreover, elevated or depressed endostatin levels in diseased states may help explain the pathophysiological mechanisms of the particular disease.

GENERAL SIGNIFICANCE

Endostatin was once sought after as the 'be all and end all' for cancer treatment; however, research throughout the last decade has made it apparent that endostatin's effects are complex and involve multiple mechanisms. A better understanding of newly discovered mechanisms and clinical applications still has the potential to lead to future advances in the use of endostatin in the clinic.

E10A, an adenovirus carrying human endostatin gene, in combination with docetaxel treatment inhibits prostate cancer growth and metastases

E10A, a replication-defective adenovirus carrying human endostatin gene, has finished Phase I clinical trials for solid cancers. We assessed whether the combination of E10A with docetaxel would enhance antiangiogenic activities and inhibit prostate cancer growth and metastases. Combination use of conditioned medium from prostate cancer cells infected by E10A and docetaxel exerted synergistic inhibition of HUVECs proliferation, migration and tube formation, compared with either agent alone. In prostate cancer s.c. xenograft models, combined therapy resulted in significant tumor growth inhibition and survival improvement. The antitumoral effect was tightly correlated with a remarkable decrease in tumor cell proliferation, microvessel, especially immature vasculature and significant increase in apoptosis induction. Systemic administration of E10A and docetaxel also effectively inhibited orthotopic growth and metastases of prostate cancer and achieved better in vivo antiangiogenic effects than either agent alone. Our data indicate that E10A in combination with docetaxel exert enhanced antiangiogenic activities and inhibit prostate cancer growth and metastases. Therefore, this approach may be an effective treatment for advanced prostate cancer and deserves more extensive investigation.

Endostar combined with cisplatin inhibits tumor growth and lymphatic metastasis of lewis lung carcinoma xenografts in mice

OBJECTIVE

To investigate the effects of endostar, a recombined humanized endostatin, plus cisplatin on the growth, lymphangiogenesis and lymphatic metastasis of the Lewis lung carcinoma (LLC) in mice.

METHODS

A tumor model were established in C57BL/6 mice by intravenious transplantation of LLC cells. Then the mice were randomized to receive administration with NS, endostar, cisplatin, or endostar plus cisplatin. After the mice were sacrificed, tumor multiplicity, tumor size and lymph node metastasis were assessed. Then the expression of vascular endothelial growth factor-c (VEGF-C) and podoplanin were determined by immunohistochemical staining.

RESULTS

Endostar plus cisplatin significantly suppressed tumor growth. lymphatic metastasis and prolonged survival time of the mice without obvious toxicity. The inhibition of lymphatic metastasis was associated with decreased microlymphatic vessel density (MLVD) and expression of VEGF-C.

CONCLUSIONS

Endostar combined with cisplatin was more effective to suppress tumor growth and lymphatic metastasis than either agent alone. Thus this may provide a rational alternative for lung carcinoma treatment.

Control of angiogenesis by VEGF and endostatin-encapsulated protein microcrystals and inhibition of tumor angiogenesis

Encapsulation of cytokines within protein microcrystals (polyhedra) is a promising approach for the stabilization and delivery of therapeutic proteins. Here, we investigate the influence of vascular endothelial growth factor (VEGF) microcrystals and endostatin microcrystals on angiogenesis. VEGF was successfully encapsulated into microcrystals derived from insect cypovirus with overexpression of protein disulfide bond isomerase. VEGF microcrystals were observed to increase the phosphorylation of p42/p44 MAP kinase and to stimulate the proliferation, migration, and network and tube formation of human umbilical vein endothelial cells (HUVECs). Endostatin was also successfully encapsulated into microcrystals. Endostatin microcrystals showed antiangiogenesis activities and inhibited the migration, and network and tube formation of HUVECs. Local administration of endostatin microcrystals in mice inhibited both angiogenesis and tumor growth with clear significant differences between treatment and control groups. Endostatin microcrystals only affected angiogenesis, but had no significant effect on lymphangiogenesis compared to controls. Local therapy using endostatin microcrystals offers a potential approach to achieve sustained therapeutic release of antiangiogenic molecules for cancer treatment.

Recombinant human endostatin endostar suppresses angiogenesis and lymphangiogenesis of malignant pleural effusion in mice

Background

Malignant pleural effusion (MPE) is a common complication of lung cancer. One widely used treatment for MPE is Endostar, a recombined humanized endostatin based treatment. However, the mechanism of this treatment is still unclear. The aim of this study was to investigate the effects of Endostar in mice with MPE.

Methods and Materials

Lewis lung carcinoma (LLC) cell line expressing enhanced green fluorescent protein (EGFP) was injected into pleural cavity to establish MPE mice model. Mice were randomly divided into four groups. High dose of Endostar (30 mg/kg), low dose of Endostar (8 mg/kg), normal saline, or Bevacizumab (5 mg/kg) was respectively injected into pleural cavity three times with 3-day interval in each group. Transverse computed tomography (CT) was performed to observe pleural fluid formation 14 days after LLC cells injection. Mice were anesthetized and sacrificed 3 days after final administration. The volume of pleural effusion n was measured using 1 ml syringe. Micro blood vessel density (MVD), Lymphatic micro vessel density (LMVD), the expression level of vascular endothelial growth factor A (VEGF-A) and VEGF-C were observed by immunohistochemistry (IHC) staining.

Results

The volume of pleural effusion as well as the number of pleural tumor foci, MVD and the expression of VEGF-A were significantly reduced in high dose of Endostar treat group. More importantly, LMVD and the expression of VEGF-C were markedly lower in treat group than those in the other three control groups.

Conclusion

Our work demonstrated that Endostar played an efficient anti-cancer role in MPE through its suppressive effect on angiogenesis and lymphangiogenesis, which provided a certain theoretical basis for the effectiveness of Endostar on the MPE treatment.

Early efficacy of Endostar combined with chemoradiotherapy for advanced cervical cancers

The aim of this study was to investigate the early outcome of Endostar combined with chemoradiotherapy for advanced cervical cancer. Fifty-two cases (FIGO IIb to IVa) were divided randomly into two groups, receiving chemoradiotherapy alone (CRT group) and Endostar combined with chemoradiotherapy (CRT+E group). For the patients in the CRT+E group, Endostar was administered daily with the dosage of 7.5 mg/m2, and cisplatin was administered weekly with the dosage of 20 mg/m2 during the radiation. The regimens lasted for 4 weeks with no difference in chemoradiotherapy between the two groups. The early outcome complete remission rate was 73.1%, partial remission rate was 23.1% and the total response rate was 96.2% in CRT+E group, a significnat improvement on the 34.6%, 42.3% and 76.9%, respectively, in the CRT group. One year survive rates were 100% and 84.6% in the CRT+E group and CRT groups, the difference being significant. Endostar combined with chemoradiotherapy can improve the early outcome of the advanced cervical cancer, and adverse effects were not encountered.

Changes in specialized blood vessels in lymph nodes and their role in cancer metastasis

Background

High endothelial venules (HEV) have been recognized to play a role in metastasis by its changes seen in the cancer microenvironment of lymph nodes (LN) and solid cancers. Squamous cell carcinoma (SCC) of the tongue is a prevalent tumor of the head and neck region with high propensity for LN metastasis. The extent of LN metastasis is the most reliable adverse prognostic factor. Primary tumors can induce vasculature reorganization within sentinel LN before the arrival of tumor cells and HEV represents these remodelled vessels. This study aims to evaluate the cancer induced vascular changes in regional lymph nodes (LN) of patients by studying the morphological and functional alterations of HEV and its correlation with clinical outcome and pathological features.

Methods

This study was based on 65 patients with SCC tongue who underwent primary surgical treatment including neck dissection. The patients were categorized into 2 groups based on the presence of malignancy in their cervical lymph nodes. A review of the patients' pathological and clinical data was performed from a prospective database. Immunohistochemical staining of the tissue blocks for HEV and high-power-field image analysis were performed and analyzed with correlation to the patients' clinical and pathological features.

Results

The total number of HEV was found to be significantly associated to disease-free interval. There was a similar association comparing the HEV parameters to overall survival. The density of abnormal HEV was significantly higher in patients with established metastases in their lymph nodes and HEV was shown to be a better prognosis factor than conventional tumor staging. The HEV morphological metamorphosis demonstrates a spectrum that correlates well with disease progression and clinical outcome.

Conclusions

The results suggest that the HEV displays a spectrum of morphological changes in the presence of cancer and LN metastasis, and that HEV is possibly involved in the process of cancer metastasis. We revealed the relationship of HEV and their metamorphosis in pre-metastatic and metastatic environments in regional lymph nodes of tongue cancer patients in relation to clinical outcomes. The significant observation of modified dilated HEV containing red blood cells in lymph nodal basin of a cancer suggests the shifting of its function from one primarily of immune response to that of a blood carrying vessel. It also demonstrated potential prognostic value. More studies are needed to elucidate its potential role in cancer immunotherapy and as a potential novel therapeutic approach to preventing metastasis by manipulating the remodelling processes of HEV.

The newcomer in the integrin family: integrin α9 in biology and cancer

Integrins are heterodimeric transmembrane receptors regulating cell-cell and cell-extracellular matrix interactions. Of the 24 integrin heterodimers identified in humans, α9β1 integrin is one of the least studied. α9, together with α4, comprise a more recent evolutionary sub-family of integrins that is only found in vertebrates. Since α9 was thought to have similar functions as α4, due to many shared ligands, it was a rather overlooked integrin until recently, when its importance for survival after birth was highlighted upon investigation of the α9 knockout mouse. α9β1 is expressed on a wide variety of cell types, interacts with many ligands for example fibronectin, tenascin-C and ADAM12, and has been shown to have important functions in processes such as cell adhesion and migration, lung development, lymphatic and venous valve development, and in wound healing. This has sparked an interest to investigate α9β1-mediated signaling and its regulation. This review gives an overview of the recent progress in α9β1-mediated biological and pathological processes, and discusses its potential as a target for cancer diagnosis and therapy.

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

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

NAHA, a novel hydroxamic acid-derivative, inhibits growth and angiogenesis of breast cancer in vitro and in vivo

Background

We have recently synthesized novel N-alkylated amino acid-derived hydroxamate, 2-[Benzyl-(2-nitro-benzenesulfonyl)-amino]-N-hydroxy-3-methyl-N-propyl-butyramide (NAHA). Here, we evaluate the anticancer activity of NAHA against highly invasive human breast cancer cells MDA-MB-231 in vitro and in vivo.

Methodology/Principal Findings

Cell growth was evaluated by MTT and soft agar assays. Protein expression was determined by DNA microarray and Western blot analysis. Metastatic potential was evaluated by cell adhesion, migration, invasion, capillary morphogenesis, and ELISA assays. The anticancer activity in vivo was evaluated in mouse xenograft model. NAHA inhibited proliferation and colony formation of MDA-MB-231 cells together with the down-regulation of expression of Cdk2 and CDC20 proteins. NAHA inhibited cell adhesion, migration, and invasion through the suppression of secretion of uPA. NAHA suppressed secretion of VEGF from MDA-MB-231 cells and inhibited capillary morphogenesis of human aortic endothelial cells (HAECs). Finally, NAHA at 50 mg/kg was not toxic and decreased tumor volume and tumor weight in vivo. This suppression of tumor growth was associated with the inhibition of mitotic figures and induction of apoptosis, and the reduction of CD31 and VEGF positive cells in tumors.

Conclusion

NAHA could be a novel promising compound for the development of new drugs for the therapy of invasive breast cancers.

Angiogenesis in cancer: Anti-VEGF escape mechanisms

It is now widely accepted that tumor-angiogenesis plays a crucial role in tumor growth, tumor propagation and metastasis formation. Among several angiogenic activators, the vascular endothelial growth factor (VEGF) and its receptors represent one of the major inducers of tumor angiogenesis. Thus, this system has become the focus of therapeutic interventions, which led to the approval of the anti-VEGF blocking antibody bevacizumab and the VEGFR-2 pathway inhibitors pazopanib, sorafenib and sunitinib. However, not every cancer patient benefits from such treatment or finally becomes resistant to anti-VEGF approaches; others are suffering from adverse effects. Thus, there is an urgent need for a better understanding of VEGF-independent mechanisms leading to angiogenesis in cancer. This review focuses on anti-VEGF escape mechanisms of tumor cells and its microenvironment.

Matrikines and the lungs

The extracellular matrix is a complex network of fibrous and nonfibrous molecules that not only provide structure to the lung but also interact with and regulate the behaviour of the cells which it surrounds. Recently it has been recognised that components of the extracellular matrix proteins are released, often through the action of endogenous proteases, and these fragments are termed matrikines. Matrikines have biological activities, independent of their role within the extracellular matrix structure, which may play important roles in the lung in health and disease pathology. Integrins are the primary cell surface receptors, characterised to date, which are used by the matrikines to exert their effects on cells. However, evidence is emerging for the need for co-factors and other receptors for the matrikines to exert their effects on cells. The potential for matrikines, and peptides derived from these extracellular matrix protein fragments, as therapeutic agents has recently been recognised. The natural role of these matrikines (including inhibitors of angiogenesis and possibly inflammation) make them ideal targets to mimic as therapies. A number of these peptides have been taken forward into clinical trials. The focus of this review will be to summarise our current understanding of the role, and potential for highly relevant actions, of matrikines in lung health and disease.

2011 Young Surgeon's Award Winner: High Endothelial Venules: A Novel Prognostic Marker in Cancer Metastasis and the Missing Link?

Introduction: The extent of lymph nodes (LNs) metastasis is a major determinant for the staging and the most reliable adverse prognostic factor. Primary tumours can induce lymphatics and vasculature reorganisations within sentinel LN before the arrival of cancer cells and these key blood vessels are identified as high endothelial venules (HEV). The alterations of HEV in the presence of cancer, coupled with the increased proliferation rate of the endothelial cells, results in a functional shift of HEV from immune response mediator to blood flow carrier. We aim to evaluate tumour-induced vascularisation in regional LN of cancer patients by studying the morphological and functional alterations of HEV and its correlation to clinico-pathological features. Materials and Methods: This multi-centre study with a prospective database identified 65 consecutive patients with tongue squamous cell carcinoma (SCC) who underwent primary surgical treatment from 2001 to 2005. Immunohistochemical staining for HEV and image analysis were performed and analysed with correlation to the patients’ clinico-pathological features. Results: The total number of HEV is significantly associated to disease-free interval when controlling for the group (P = 0.022) as well as combining both groups as one cohort (P = 0.023). There is also a similar association comparing the HEV parameters to overall survival. Conclusion: Our results suggest that HEV possibly plays a key role in the pathogenesis of lymphatic and subsequent distant metastases and may provide the missing link in cancer metastasis. Confirmation of this hypothesis would offer a novel therapeutic approach to preventing metastasis by blocking the remodeling processes of HEV in LN. Key words: High endothelial venules, Cancer metastasis, Angioegenesis

Endostatin specifically targets both tumor blood vessels and lymphatic vessels

Endostatin, a 20 kDa C-terminal fragment of collagen XVIII, was first identified as a potent angiogenic inhibitor. The anti-angiogenic function of endostatin has been well documented during the past decade. Recently, several studies demonstrated that endostatin also inhibits tumor lymphangiogenesis and lymphatic metastasis. However, the exact mechanism that endostatin executes its anti-angiogenic and anti-lymphangiogenic functions remains elusive. In the current mini-review, we briefly summarize recent novel findings, including the functions of endostatin targeting not only angiogenesis but also lymphangiogenesis, and the underlying mechanism by which endostatin internalization regulates its biological functions.

Endostatin suppresses colorectal tumor-induced lymphangiogenesis by inhibiting expression of fibronectin extra domain A and integrin α9

Endostatin is a natural occurring anti-angiogenic peptide and has been shown to inhibit tumor lymphangiogenesis by suppressing the expression of tumor-stimulating growth factors. We have previously shown that fibronectin alternative extra domain A (EDA) facilitates lymphangiogenesis of colorectal tumors. Since it is known that EDA interacts with integrin α9 in the lymphatic endothelial cells (LECs), we hypothesized that endostatin may target EDA-integrin α9 pathway to inhibit colorectal tumor-induced lymphangiogenesis. To test this hypothesis, we examined the effect of endostatin on EDA secreted by SW480 colorectal cancer cells and treated human LECs with different doses of endostatin in the presence of conditional medium from SW480 cells. We found that endostatin significantly reduced EDA secretion by SW480 cells and the expression of integrin α9 in LECs. Immunofluorescence studies showed that EDA and integrin α9 colocalized on the cell membrane of LECs and these colocalizations were dramatically reduced by endostatin. Co-immunoprecipitation studies demonstrated that EDA interacted with integrin α9 in LECs, and showed that endostatin treatment inhibited the formation of EDA-integrin α9 complex in LECs. Furthermore, we found that the arrangement and polarity of LEC cytoskeletons were destroyed by endostatin substantially, leading to a reduced formation of tube-like structures of LECs and a suppressed chemotaxis of LECs toward SW480 cells. Consistently, EDA and integrin α9 expressions as well as lymphangiogenesis were significantly suppressed by endostatin in colorectal cancer xenografts. In conclusion, our results suggest that endostatin reduces colorectal tumor-induced lymphangiogenesis, at least in part, by inhibiting EDA-integrin α9 pathway.

The angiostatic protein 16K human prolactin significantly prevents tumor-induced lymphangiogenesis by affecting lymphatic endothelial cells

The 16-kDa angiostatic N-terminal fragment of human prolactin (16K hPRL) has been reported to be a new potent anticancer compound. This protein has already proven its efficiency in several mouse tumor models in which it prevented tumor-induced angiogenesis and delayed tumor growth. In addition to angiogenesis, tumors also stimulate the formation of lymphatic vessels, which contribute to tumor cell dissemination and metastasis. However, the role of 16K hPRL in tumor-induced lymphangiogenesis has never been investigated. We establish in vitro that 16K hPRL induces apoptosis and inhibits proliferation, migration, and tube formation of human dermal lymphatic microvascular endothelial cells. In addition, in a B16F10 melanoma mouse model, we found a decreased number of lymphatic vessels in the primary tumor and in the sentinel lymph nodes after 16K hPRL treatment. This decrease is accompanied by a significant diminished expression of lymphangiogenic markers in primary tumors and sentinel lymph nodes as determined by quantitative RT-PCR. These results suggest, for the first time, that 16K hPRL is a lymphangiostatic as well as an angiostatic agent with antitumor properties.

Serum endostatin levels correlate with enhanced extracellular matrix degradation and poor patients' prognosis in bladder cancer

Endostatin, the proteolytic fragment of collagen XVIII, is an inhibitor of angiogenesis and tumor growth. Interestingly, elevated circulating endostatin levels have been found to correlate with poor patients' prognosis in several cancers. The aim of this study was to assess the prognostic value of endostatin in bladder cancer (BC) and to gain insight into the mechanisms involved in its production. This retrospective study included a total of 337 patients with BC and 103 controls. Collagen XVIII gene expression was analyzed using real-time PCR (n = 82). Endostatin tissue localization was assessed by immunohistochemistry (n = 27). Endostatin serum (n = 87) and urine (n = 153) levels were determined by ELISA. In 12 cases, both serum and paraffinized tissue samples from the same patients were available. We found decreased collagen XVIII tissue expression and increased endostatin urine and serum concentration in samples of patients with BC compared to controls. High serum endostatin levels correlated with the presence of lymph node metastases and MMP-7 concentrations and were independently associated with poor metastasis-free and disease-specific survival. Immunohistochemical analysis revealed a strong endostatin staining in the wall of tumor associated blood vessels in superficial but not in muscle-invasive BCs. Based on these, we concluded that elevated endostatin levels in patients with BC are the consequence of enhanced extracellular matrix degradation and are independent from collagen XVIII expression. Furthermore, serum endostatin levels may provide prognostic information independent from histopathological parameters and may therefore help to optimize therapy decisions. Loss of endostatin expression in tumor associated blood vessels might represent an important step supporting tumor-induced angiogenesis.

Lymphatic function is regulated by a coordinated expression of lymphangiogenic and anti-lymphangiogenic cytokines

Lymphangiogenic cytokines such as vascular endothelial growth factor-C (VEGF-C) are critically required for lymphatic regeneration; however, in some circumstances, lymphatic function is impaired despite normal or elevated levels of these cytokines. The recent identification of anti-lymphangiogenic molecules such as interferon-γ (IFN-γ), transforming growth factor-β1, and endostatin has led us to hypothesize that impaired lymphatic function may represent a dysregulated balance in the expression of pro/anti-lymphangiogenic stimuli. We observed that nude mice have significantly improved lymphatic function compared with wild-type mice in a tail model of lymphedema. We show that gradients of lymphatic fluid stasis regulate the expression of lymphangiogenic cytokines (VEGF-A, VEGF-C, and hepatocyte growth factor) and that paradoxically the expression of these molecules is increased in wild-type mice. More importantly, we show that as a consequence of T-cell-mediated inflammation, these same gradients also regulate expression patterns of anti-lymphangiogenic molecules corresponding temporally and spatially with impaired lymphatic function in wild-type mice. We show that neutralization of IFN-γ significantly increases inflammatory lymph node lymphangiogenesis independently of changes in VEGF-A or VEGF-C expression, suggesting that alterations in the balance of pro- and anti-lymphangiogenic cytokine expression can regulate lymphatic vessel formation. In conclusion, we show that gradients of lymphatic fluid stasis regulate not only the expression of pro-lymphangiogenic cytokines but also potent suppressors of lymphangiogenesis as a consequence of T-cell inflammation and that modulation of the balance between these stimuli can regulate lymphatic function.

Endostatin inhibits tumour lymphangiogenesis and lymphatic metastasis via cell surface nucleolin on lymphangiogenic endothelial cells

Endostatin has potent anti-endothelial and anti-angiogenic functions. Endostatin was reported to reduce lymphangiogenesis by down-regulating the level of VEGF-C in tumour tissues. However, there is little evidence for the direct function of endostatin on lymphangiogenic endothelial cells and lymphangiogenic vessels. Here, we report that cell surface nucleolin, which was reported as an endostatin receptor mediating its anti-angiogenic and anti-tumour functions, is also selectively expressed on the cell surface of lymphangiogenic endothelial cells both in vitro and in vivo. Treatment of primary mouse lymphatic endothelial cells (mLECs) by endostatin inhibits mLEC migration, tubule formation, and activation of the Erk pathway in mLECs, while neutralization of cell surface nucleolin or nucleolin knockdown results in loss of the anti-lymphatic endothelial activities of endostatin. Also, anti-nucleolin antibody or lentivirus delivered nucleolin siRNA abolishes the anti-lymphangiogenic function of endostatin in the Matrigel plug assay. Endostatin remarkably inhibits tumour-associated lymphangiogenesis, leading to reduced lymphatic metastasis. Systemic blockade of nucleolin notably abolishes the anti-lymphangiogenic and anti-lymphatic metastatic functions of endostatin. Importantly, endostatin does not affect quiescent lymphatics in normal organs, which is consistent with the lack of expression of cell surface nucleolin in quiescent lymphatics. Taken together, our results demonstrate that endostatin directly acts on lymphangiogenic endothelial cells via cell surface nucleolin, which provides a novel mechanism for the inhibition of tumour lymphangiogenesis and lymphatic metastasis by endostatin.

Interaction between the extracellular matrix and lymphatics: consequences for lymphangiogenesis and lymphatic function

The lymphatic system is important for body fluid balance as well as immunological surveillance. Due to the identification of new molecular markers during the last decade, there has been a recent dramatic increase in our knowledge on the molecular mechanisms involved in lymphatic vessel growth (lymphangiogenesis) and lymphatic function. Here we review data showing that although it is often overlooked, the extracellular matrix plays an important role in the generation of new lymphatic vessels as a response to physiological and pathological stimuli. Extracellular matrix-lymphatic interactions as well as biophysical characteristics of the stroma have consequences for tumor formation, growth and metastasis. During the recent years, anti-lymphangiogenesis has emerged as an additional therapeutic modality to the clinically applied anti-angiogenesis strategy. Oppositely, enhancement of lymphangiogenesis in situations of lymph accumulation is seen as a promising strategy to a set of conditions where few therapeutic avenues are available. Knowledge on the interaction between the extracellular matrix and the lymphatics may enhance our understanding of the underlying mechanisms and may ultimately lead to better therapies for conditions where reduced or increased lymphatic function is the therapeutic target.

The Vasohibin Family

Angiogenesis is regulated by the local balance between angiogenesis stimulators and inhibitors. A number of endogenous angiogenesis inhibitors have been found in the body. The origin of these inhibitors is mostly extrinsic to the vasculature. Recently, however, vascular endothelial cells themselves have been found to produce angiogenesis inhibitors including vasohibin-1. These intrinsic inhibitors are thought to regulate angiogenesis by an auto-regulatory or negative-feedback mechanism. This review will focus on vasohibin-1 produced by vascular endothelial cells and on its homologue, vasohibin-2.

Endogenous angiogenesis inhibitor vasohibin1 exhibits broad-spectrum antilymphangiogenic activity and suppresses lymph node metastasis

During cancer progression, the angiogenesis that occurs is involved in tumor growth and hematogenous-distant metastasis, whereas lymphangiogenesis is involved in regional lymph node metastasis. Angiogenesis is counterregulated by various endogenous inhibitors; however, little is known about endogenous inhibitors of lymphangiogenesis. We recently isolated vasohibin1 as an angiogenesis inhibitor intrinsic to the endothelium and further demonstrated its anticancer activity through angiogenesis inhibition. Here, we examined the effect of vasohibin1 on lymphangiogenesis. Vasohibin1 exhibited broad-spectrum antilymphangiogenic activity in the mouse cornea induced by factors including VEGF-A, VEGF-C, FGF2, and PDGF-BB. We then inoculated highly lymph node-metastatic cancer cells into mice and examined the effect of vasohibin1 on lymph node metastasis. Tail-vein injection of adenovirus containing the human vasohibin1 gene inhibited tumor lymphangiogenesis and regional lymph node metastasis. Moreover, local injection of recombinant vasohibin1 inhibited lymph node metastasis. These results suggest vasohibin1 to be the first known intrinsic factor having broad-spectrum antilymphangiogenic activity and indicate that it suppresses lymph node metastasis.

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.

Multipotent mesenchymal stem cells acquire a lymphendothelial phenotype and enhance lymphatic regeneration in vivo

BACKGROUND

The importance and therapeutic value of stem cells in lymphangiogenesis are poorly understood. We evaluated the potential of human and murine mesenchymal stem cells (MSCs) to acquire a lymphatic phenotype in vitro and to enhance lymphatic regeneration in vivo.

METHODS AND RESULTS

We assessed the lymphendothelial differentiation of human and murine MSCs after induction with supernatant derived from human dermal microvascular endothelial cells, isolated lymphatic endothelial cells, and purified vascular endothelial growth factor (VEGF)-C in vitro. We used human or murine progenitor MSC lines and then characterized the lymphatic phenotype by morphology, migratory capacity, and the expression of lymphatic markers such as Prox-1, podoplanin, Lyve-1, VEGF receptor-2, and VEGF receptor-3. Using a murine lymphatic edema model, we assessed the potential of these cells to form a functional lymphatic vasculature in vivo after injection of syngeneic MSCs. Incubation with supernatant from lymphatic endothelial cells induced an endothelium-like morphology and the expression of lymphendothelial markers in both human and murine MSCs in vitro. MSCs showed migratory activity along a VEGF-C gradient, which was enhanced by VEGF-C conditioning. In vivo, the local application of MSCs resulted in a significant decrease in edema formation (-20.1%; P<0.01 versus untreated tails) after 3 weekly cell injections and restored the drainage of intradermally injected methylene blue after 7 weekly injections.

CONCLUSIONS

MSCs were capable of expressing a lymphatic phenotype when exposed to lymph-inductive media and purified VEGF-C. Migratory activity toward VEGF-C in vitro suggests homing capability in vivo. Restoration of lymphatic drainage after injection of MSCs in a lymphedema model indicates that MSCs play a role in lymphatic regeneration. The potential clinical application of MSC in wound healing and reduction of lymphatic edema warrants further research.

Phellinus linteus suppresses growth, angiogenesis and invasive behaviour of breast cancer cells through the inhibition of AKT signalling

The antitumour activity of a medicinal mushroom Phellinus linteus (PL), through the stimulation of immune system or the induction of apoptosis, has been recently described. However, the molecular mechanisms responsible for the inhibition of invasive behaviour of cancer cells remain to be addressed. In the present study, we demonstrate that PL inhibits proliferation (anchorage-dependent growth) as well as colony formation (anchorage-independent growth) of highly invasive human breast cancer cells. The growth inhibition of MDA-MB-231 cells is mediated by the cell cycle arrest at S phase through the upregulation of p27^Kip1 expression. Phellinus linteus also suppressed invasive behaviour of MDA-MB-231 cells by the inhibition of cell adhesion, cell migration and cell invasion through the suppression of secretion of urokinase-plasminogen activator from breast cancer cells. In addition, PL markedly inhibited the early event in angiogenesis, capillary morphogenesis of the human aortic endothelial cells, through the downregulation of secretion of vascular endothelial growth factor from MDA-MB-231 cells. These effects are mediated by the inhibition of serine-threonine kinase AKT signalling, because PL suppressed phosphorylation of AKT at Thr³⁰⁸ and Ser⁴⁷³ in breast cancer cells. Taken together, our study suggests potential therapeutic effect of PL against invasive breast cancer.

Endostatin overexpression inhibits lymphangiogenesis and lymph node metastasis in mice

Endostatin, a proteolytic fragment of collagen XVIII, is a potent inhibitor of angiogenesis and tumor growth. We studied the development of carcinogen-induced skin tumors in transgenic J4 mice overexpressing endostatin in their keratinocytes. Unexpectedly, we did not observe any differences in tumor incidence and multiplicity between these and control mice, nor in the rate of conversion of benign papillomas to malignant squamous cell carcinomas (SCC). We did find, however, that endostatin regulates the terminal differentiation of keratinocytes because the SCCs in the J4 mice were less aggressive and more often well differentiated than those in the control mice. We observed an inhibition of tumor angiogenesis by endostatin at an early stage in skin tumor development, but more strikingly, there was a significant reduction in lymphatic vessels in the papillomas and SCCs in association with elevated endostatin levels and also a significant inhibition of lymph node metastasis in the J4 mice. We showed that tumor-infiltrating mast cells strongly expressed vascular endothelial growth factor-C (VEGF-C), and that the accumulation of these cells was markedly decreased in the tumors of the J4 mice. Moreover, endostatin inhibited the adhesion and migration of murine MC/9 mast cells on fibronectin in vitro. Our data suggest that endostatin can inhibit tumor lymphangiogenesis by decreasing the VEGF-C levels in the tumors, apparently via inhibition of mast cell migration and adhesion, and support the view that the biological effects of endostatin are not restricted to endothelial cells because endostatin also regulates tumor-associated inflammation and differentiation, and the phenotype of epithelial tumors.

Lymphatic metastasis in breast cancer: importance and new insights into cellular and molecular mechanisms

Lymph node metastasis is the main prognosis factor in a number of malignancies, including breast carcinomas. The means by which lymph node metastases arise is not fully understood, and many questions remain about their importance in the further spread of breast cancer. Nevertheless, a number of key cellular and molecular mechanisms of lymphatic metastasis have been identified. These include induction of intra- or peri-tumoral lymphangiogenesis or co-option of existing lymphatic vessels to allow tumour cells to enter the lymphatics, although it remains to be established whether this is primarily an active or passive process. Gene expression microarrays and functional studies in vitro and in vivo, together with detailed clinical observations have identified a number of molecules that can play a role in the genesis of lymph node metastases. These include the well-recognised lymphangiogenic cytokines VEGF-C and VEGF-D as well as chemokine-receptor interactions, integrins and downstream signalling pathways. This paper briefly reviews current clinical and experimental evidence for the underlying mechanisms and significance of lymphatic metastasis in breast cancer and highlights questions that still need to be addressed.

Radiogenic lymphangiogenesis in the skin

The time course of microvascular changes in the environment of irradiated tumors was studied in a standardized human protocol. Eighty skin biopsies from 40 patients with previously treated primary breast cancer were taken from irradiated skin and corresponding contralateral unirradiated control areas 2 to 8 weeks, 11 to 14 months, or 17+ months after radiotherapy (skin equivalent dose 30 to 40 Gy). Twenty-two biopsies of 11 melanoma patients who had undergone lymph node dissection were used for unirradiated control. We found an increase of total podoplanin(+) lymphatic microvessel density resulting mainly from a duplication of the density of smallest lymphatic vessels (diameter <10 microm) in the samples taken 1 year after radiation. Our findings implicate radiogenic lymphangiogenesis during the 1st year after therapy. The numbers of CD68(+) and vascular endothelial growth factor-C(+) cells were highly elevated in irradiated skin in the samples taken 2 to 8 weeks after radiotherapy. Thus, our results indicate that vascular endothelial growth factor-C expression by invading macrophages could be a pathogenetic route of induction of radiogenic lymphangiogenesis.

Papillary thyroid carcinoma with lymph node metastases

Papillary thyroid cancer (PTC) is the most frequently occurring human thyroid cancer with good prognosis following appropriate treatment. Lymph node (LN) metastases are the main way through which PTC spread cancer cells. The mechanisms underlying PTC with local invasion, LN metastases and distant metastases are not well investigated. Tumor secrete cytokines, such as vascular endothelial growth factor (VEGF)-C and -D bind to VEGF receptors on lymphatic endothelial cells and induce proliferation (budding) from nearby lymphatic capillaries and growth of new lymphatic capillaries. About one-third of patients can be diagnosed at the time of surgical findings. Different image studies, such as ultrasonography with fine needle aspiration cytology, scintigraphic localization and positron emission tomography were reported to detect LN metastases. Important factors in predicting LN metastases are vascular invasion, male gender, absence of tumor capsule, and perithyroid involvement. Tumor recurrence in LN after primary treatment of PTC had an independent and highly significant negative effect on survival in patients over 45 year-old. Recombinant adeno-associated virus-mediated gene transfer of sVEGFR3-Fc is a feasible therapeutic scheme for blocking lymphogenous metastasis. In conclusion, aggressive surgical procedures performed by experienced surgeons or postoperative radioactive iodine therapy to minimize local recurrence of LN for PTC patients with high risk.

Anti-angiogenic gene therapy of cancer: current status and future prospects

The discovery of endogenous inhibitors of angiogenesis has made it possible to test the hypothesis that blocking the angiogenic switch may keep tumor growth in check, and has added a new investigational arm to the field of cancer gene therapy. Angiogenesis inhibitors are heterogeneous in origin and potency, and their growing list includes proteolysis products of larger molecules with a different function, such as angiostatin, endostatin and vasostatin, modulators of vascular endothelial growth factor activity, such as sFLT-1, and some cytokines/chemokines with marked anti-endothelial activity, such as IL-12, IFN-alpha, and CXCL10. Pre-clinical studies have clearly indicated that these factors are essentially cytostatic and that they need long-term administration in order to obtain prolonged anti-tumor effects, representing a rational basis for their delivery by a gene therapy approach. The experimental approaches attempted to date, reviewed herein, indicate overall that anti-angiogenic gene therapy has efficacy mainly as an early intervention strategy and that a better understanding of the biological mechanisms underlying resistance to angiogenesis inhibition, as well as appropriate combined treatments, are required to generate a conceptual advancement which could drive the field towards successful management of established tumors.

Current status of angiogenesis inhibitors combined with radiation therapy

Angiogenesis inhibitors combined with cytotoxic chemotherapy have recently entered routine oncological practice. Several rationales exist for combining these agents with ionizing radiation, a primary curative cancer treatment, either in bimodal or trimodal fashion, i.e. with or without additional chemotherapy. More than 20 different anti-angiogenic agents have been studied in preclinical animal tumor models. This systematic review compares the results of preclinical studies published before February 2006. The combination of vascular endothelial growth factor (VEGF) inhibitors with irradiation consistently resulted in improved tumor growth delay (at least additive effects), despite different radiation schedules, drugs and doses, and combination regimens. Only two studies evaluated tumor control dose (TCD)50 as a measure of tumor cure (radiation dose yielding permanent local control in 50% of the tumors). While anti-VEGF receptor (VEGFR) antibody treatment improved the outcome, a VEGFR tyrosine kinase inhibitor showed negative results. For agents interfering with other pathways, the results are also not consistent, although most studies were positive. Trimodal approaches seem to improve tumor growth delay even further. Importantly, both radiotherapy schedule and sequence of the modalities in combined treatment may impact on the outcome. Hence, further preclinical studies examining these parameters need to be conducted. While preclinical research is ongoing, phase I and II clinical trials with bevacizumab, combretastatin A-4, thalidomide and different receptor tyrosine kinase inhibitors, usually combined with radio- and chemotherapy, have been designed. Early results suggest that acute toxicity is acceptable, planned surgery after such treatment is feasible, and that further evaluation of such combined modality treatment is warranted.