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PubMed2006

Pathways targeting tumor lymphangiogenesis.

Tumor metastasis to sentinel lymph nodes represents the first step of tumor dissemination in most human cancers and serves as a major prognostic indicator for disease progression. Recent studies have revealed that tumors can actively induce the formation of lymphatic vessels, and that tumor lymphangiogenesis is correlated with lymph node metastasis in experimental cancer models and in several types of human cancers. Metastatic tumor cells may continue to promote lymphatic vessel growth even after their metastasis to sentinel lymph nodes, likely promoting further cancer spread. Vascular endothelial growth factor-C (VEGF-C) and VEGF-D were the first specific lymphangiogenesis factors identified, acting predominantly via VEGF receptor-3 (VEGFR-3) that is expressed by lymphatic endothelial cells, and a large number of clinical studies have shown a correlation between tumor expression of VEGF-C or VEGF-D and lymph node metastasis. VEGFR-3 activation promotes lymphatic endothelial cell proliferation, migration, and survival via the extracellular signal-regulated kinase 1/2, the phosphatidylinositol 3-kinase/AKT, and the c-Jun NH(2)-terminal kinase 1/2 pathways. Additional tumor lymphangiogenesis factors have been recently identified, including VEGF-A. Importantly, blockade of the VEGFR-3 pathway by specific antibodies, by soluble receptor constructs, and by small molecule kinase inhibitors efficiently inhibits experimental tumor lymphangiogenesis and metastasis and might also represent a novel therapeutic avenue for the treatment of human cancers.

Animals↗
PubMed2006

Current strategies for modulating lymphangiogenesis signalling pathways in human disease.

The recent discovery that members of the vascular endothelial growth factor (VEGF) family of secreted glycoproteins can mediate lymphatic vessel growth (lymphangiogenesis) via cell surface receptor tyrosine kinases expressed on endothelial cells has opened the way for therapeutic intervention for pathologies involving dysregulated lymphatic vessel function. At least two members of this family, VEGF-C and VEGF-D, have been shown to induce lymphangiogenesis in vivo. Lymphatic vessels and their specific growth factors have been directly implicated in a number of significant human pathologies. In cancer, VEGF-C and VEGF-D appear to correlate with tumor metastasis and poor patient outcome in a range of prevalent human cancers. Experimental studies have demonstrated that expression of the lymphangiogenic growth factors in tumor models induces increased lymphangiogenesis and results in spread of tumor cells via the lymphatics. In contrast, conditions such as lymphedema, where lymphatic vessels fail to clear fluid from interstitial spaces, are opportunities for which the application of growth factors to generate new lymphatic vessels may be a viable therapeutic option. The list of molecules that control lymphangiogenesis is now expanding, allowing more opportunities for the development of drugs with which to manipulate the relevant signalling pathways. Modulating these pathways and other molecules with specificity to the lymphatic endothelium could offer alternative treatments for a number of important clinical conditions.

Disease↗
PubMed2026

Lymphangiogenesis-related gene signature-based risk model for prognostic assessment of cervical cancer: immune-metabolic characterization and molecular subtype analysis.

BACKGROUND: Lymphangiogenesis promotes tumor dissemination and may shape the immune contexture of cervical cancer, yet lymphangiogenesis-related prognostic stratification and its immunometabolic implications remain insufficiently defined in cervical squamous cell carcinoma and endocervical adenocarcinoma (CESC). METHODS: TCGA-CESC transcriptomes and clinical data were obtained from UCSC Xena and integrated with normal cervix tissues from the Genotype-Tissue Expression Project after batch correction. Prognostic LYMRGs were first identified from the differentially expressed set using univariable Cox proportional hazards analysis. Candidate genes were then reduced using an L1-regularized Cox model (Least Absolute Shrinkage and Selection Operator), and the remaining markers were entered into a multivariable Cox regression to obtain the final coefficients and compute an individualized risk score. The model's prognostic value was further assessed in an independent Gene Expression Omnibus dataset. In addition, expression patterns of the signature genes were leveraged for molecular subtyping of TCGA samples via non-negative matrix factorization (NMF). Immune infiltration and immunotherapy-associated characteristics were interrogated through a multi-algorithm strategy (single-sample gene set enrichment analysis, CIBERSORT, ESTIMATE, Tumor Immune Dysfunction and Exclusion (TIDE), and Immunophenoscore . Additional analyses included pathway enrichment (GSEA/GO/KEGG), drug sensitivity prediction (pRRophetic/CellMiner), and ceRNA network analysis. RESULTS: A six-gene LYMRG signature robustly stratified survival. High-risk patients had significantly worse overall survival in The Cancer Genome Atlas with AUCs of 0.819/0.801/0.801 at 1/3/5 years, and in GSE52903 (P = 0.001) with AUCs of 0.733/0.719/0.725. NMF identified two subtypes with distinct prognosis (P = 0.01) and divergent immune landscapes. Risk groups and subtypes exhibited consistent differences in immune infiltration, checkpoint expression, TIDE/IPS patterns, and pathway enrichment. Predicted chemosensitivity differed by risk group, and the ceRNA network suggested candidate upstream lncRNA regulators of the signature. CONCLUSION: A lymphangiogenesis-related six-gene model enables clinically meaningful prognostic stratification of CESC and links lymphangiogenesis programs to distinct tumor immune phenotypes and therapeutic vulnerabilities.

cancer↗
PubMed2003

[Lymphangiogenesis and new markers for lymphatic endothelium].

OBJECTIVE: To summarise recent knowledge about lymphangiogenesis, markers of the lymphatic endothelium and their importance to the tumor dissemination. DESIGN: A literature review. SETTING: Department of Gynecology and Obstetrics, Medical Faculty, Palacký University, University Hospital, Olomouc. ABSTRACTS: Clinicopathological data suggest that the lymphatics are an initial route for the spread of solid tumors. Detection of sentinel lymph nodes by biopsy provides significant information for staging and designing therapeutic regimens. The role of angiogenesis (formation of new blood vessels) in facilitating the growth of tumors has been well established, but the presence of lymphatic vessels and the relevance of lymphangiogenesis (formation of new lymphatics) to tumor spread are less clear. Growth factors involved in lymphangiogenesis during embryogenesis have been recently identified and showed to be able to induce formation of intratumoral lymphatics and thus facilitate metastatic spread to lymph nodes. The development of approaches to block tumor lymphangiogenesis and treat lymphedema would benefit from the availability of markers specific for lymphatic endothelium.

Animals↗
PubMedDate not supplied

Lymphangiogenesis, inflammation and metastasis.

The lymphatic vascular system is necessary for the return of extravasated interstitial fluid and macromolecules to the blood circulation, for immune defense, and for the uptake of dietary fats. Impaired functioning of lymphatic vessels results in lymphedema, whereas tumor-associated lymphangiogenesis may contribute to the spread of cancer cells from solid tumors. Recent studies have identified lymphatic molecular markers and growth factors necessary for lymphangiogenesis. In particular, lymphatic endothelial receptor tyrosine kinase VEGFR-3, and its ligands VEGF-C and VEGF-D, are major players in promoting lymphatic vascular growth both during development and in pathological conditions. Lymphatic vessels play a crucial role in a variety of human cancers, since invasion of lymphatic vessels by tumor cells and subsequent development of lymph node metastases significantly influence the prognosis of cancer patients and, therefore, represent an integral part of tumor staging. Recent evidence on the important influence of lymphangiogenic growth factors on intralymphatic cancer growth and metastasis raises hopes that lymphatic vessels and factors inducing their growth could serve as additional targets for tumor therapy. Nevertheless, in contrast to blood vessel angiogenesis, the mechanisms of new lymphatic vessel formation in human cancers, i.e. lymphangiogenesis, are still relatively unclear. In the framework of possible antilymphangiogenic therapies, this review focuses on the mechanisms of lymphangiogenesis in general, and especially on the role of lymphatic vessels in the process of metastasis.

Endothelial Cells↗
PubMed2001

Lymphangiogenesis in malignant tumours: Does it occur?

The development of a vascular bed is essential for solid tumour growth and metastasis. In many tumours, mean vascular density can be related to the rate of metastasis and, therefore, to prognosis. In other tumour types, such as cutaneous melanoma and head-and-neck squamous cell carcinoma, this relation is absent. Until now, the reason for this has been unclear, but since these particular tumour types are also known for their propensity to spread via the lymphatic system, it may be speculated that the presence of a pre-existing lymphatic bed and the formation of new lymphatics (lymphangiogenesis) are important factors. Growth factors involved in lymphangiogenesis during embryogenesis have been recently identified and these are also expressed in many tumour types, but the existence of tumour-induced lymphangiogenesis has not so far been reported. Partly, this could be due to the lack of reliable endothelial markers, thereby hampering a consistent evaluation of lymphatic vasculature. This editorial discusses the role of the lymphatic bed in mediating the metastasis of solid tumours, summarizes known methods to detect lymphatics, and proposes a hypothetical mechanism of tumour-induced lymphangiogenesis.

Biomarkers, Tumor↗
PubMed2003

Tumor lymphangiogenesis: a novel prognostic indicator for cutaneous melanoma metastasis and survival.

Malignant melanomas of the skin are distinguished by their propensity for early metastatic spread via lymphatic vessels to regional lymph nodes, and lymph node metastasis is a major determinant for the staging and clinical management of melanoma. However, the importance of tumor-induced lymphangiogenesis for lymphatic melanoma spread has remained unclear. We investigated whether tumor lymphangiogenesis occurs in human malignant melanomas of the skin and whether the extent of tumor lymphangiogenesis may be related to the risk for lymph node metastasis and to patient survival, using double immunostains for the novel lymphatic endothelial marker LYVE-1 and for the panvascular marker CD31. Tumor samples were obtained from clinically and histologically closely matched cases of primary melanomas with early lymph node metastasis (n = 18) and from nonmetastatic melanomas (n = 19). Hot spots of proliferating intratumoral and peritumoral lymphatic vessels were detected in a large number of melanomas. The incidence of intratumoral lymphatics was significantly higher in metastatic melanomas and correlated with poor disease-free survival. Metastatic melanomas had significantly more and larger tumor-associated lymphatic vessels, and a relative lymphatic vessel area of >1.5% was significantly associated with poor disease-free and overall survival. In contrast, no differences in the density of tumor-associated blood vessels were found. Vascular endothelial growth factor and vascular endothelial growth factor-C expression was equally detected in a minority of cases in both groups. Our results reveal tumor lymphangiogenesis as a novel prognostic indicator for the risk of lymph node metastasis in cutaneous melanoma.

Adult↗
PubMed2003

Corneal lymphangiogenesis: evidence, mechanisms, and implications for corneal transplant immunology.

PURPOSE: The normal cornea is devoid of blood and lymphatic vessels but can become vascularized secondary to a variety of corneal diseases and surgical manipulations. Whereas corneal (hem)angiogenesis, i.e., the outgrowth of new blood vessels from preexisting limbal vessels, is obvious both clinically and histologically, proof of associated corneal lymphangiogenesis has long been hampered by invisibility and lack of specific markers. This has changed with the recent discovery of the lymphatic endothelial markers vascular endothelial growth factor receptor 3, LYVE-1 (a lymphatic endothelium-specific hyaluronan receptor), Prox 1, and Podoplanin. METHODS: We herein summarize the current evidence for lymphangiogenesis in the cornea and describe its molecular markers and mediators. Furthermore, the pathophysiologic implications of corneal lymphangiogenesis for corneal transplant immunology are discussed. RESULTS: Whereas corneal angiogenesis in vascularized high-risk beds provides a route of entry for immune effector cells to the graft, lymphangiogenesis enables the exit of antigen-presenting cells and antigenic material from the graft to regional lymph nodes, thus inducing alloimmunization and subsequent graft rejection. CONCLUSIONS: Antilymphangiogenic strategies may improve transplant survival both in the high- and low-risk setting of corneal transplantation.

Biomarkers↗
PubMed2002

The role of interstitial stress in lymphatic function and lymphangiogenesis.

The management and control of tissue fluid balance depends on the highly regulated orchestration of various interstitial factors. In particular, lymphatic function, lymphatic biology, and development (lymphangiogenesis), and the extracellular matrix all contribute to interstitial fluid balance. In light of the dynamic interdependence of these factors, our lab has been working towards establishing a mechanical-molecular picture of the process of lymphangiogenesis-that is, bridging the physiological context of lymphangiogenesis with its molecular regulation by studying the coordination of mechanical forces, ECM development, lymphatic biology, and lymphatic capillary organization and development. Our working hypothesis is that the physiological driving force for lymphangiogenesis is the need for organized interstitial fluid flow. This paper will outline the rationale and background for such an approach and highlight some of the recently published findings of our lab and others that support this concept.

Animals↗
PubMed2006

Glucocorticoids suppress tumor lymphangiogenesis of prostate cancer cells.

PURPOSE: Glucocorticoids such as prednisone, hydrocortisone, and dexamethasone are known to provide some clinical benefit for patients with hormone-refractory prostate cancer. However, the underlying mechanisms by which glucocorticoids affect hormone-refractory prostate cancer progression are not well established as yet. Our previous study has shown that glucocorticoids inhibit tumor angiogenesis possibly by down-regulation of vascular endothelial growth factor (VEGF) and interleukin 8. Here, we hypothesized that the therapeutic effect of dexamethasone on hormone-refractory prostate cancer can be partly attributed to a direct inhibition of lymphangiogenesis through the glucocorticoid receptor by down-regulating a major lymphangiogenic factor, VEGF-C. EXPERIMENTAL DESIGN: The effects of dexamethasone on the expression of VEGF-C and its receptor, VEGF receptor-3 (VEGFR-3), were examined using an androgen-independent human prostate cancer cell line, DU145, which expresses glucocorticoid receptor. The effects of dexamethasone on tumor-associated lymphangiogenesis in DU145 xenografts were determined by analyzing VEGF-C gene expression, lymphatic vessel density, and relative lymphatic vessel area. RESULTS: Dexamethasone significantly down-regulated VEGF-C gene expression and protein production by 48% (P = 0.003) and 44% (P = 0.002), respectively, under normoxic condition. Similarly, hydrocortisone down-regulated VEGF-C gene expression. The effects of dexamethasone were completely reversed by the glucocorticoid receptor antagonist RU486. Even under hypoxia-like conditions, dexamethasone inhibited VEGF-C gene expression. In DU145 xenografts, dexamethasone significantly down-regulated VEGF-C gene expression and decreased lymphangiogenesis. Dexamethasone did not affect VEGFR-3 gene expression in vitro and in vivo. CONCLUSION: Glucocorticoids suppressed tumor-associated lymphangiogenesis by down-regulating VEGF-C through glucocorticoid receptor in androgen-independent prostate cancer cells in vivo.

Animals↗
PubMed2001

Lymphangiogenesis and tumor metastasis: myth or reality?

The metastatic spread of tumor cells is responsible for the majority of cancer deaths, and with few exceptions, all cancers can metastasize. Clinical findings have long suggested that by providing a pathway for tumor cell dissemination, tumor-associated lymphatics are a key component of metastatic spread. It is not known, however, whether pre-existing vessels are sufficient to serve this function, or whether tumor cell dissemination requires de novo lymphatic formation (lymphangiogenesis) or an increase in lymphatic size. Lymphangiogenesis has traditionally been overshadowed by the greater emphasis placed on the blood vascular system (angiogenesis). This is due in part to the lack of identification of lymphangiogenic factors, as well as suitable markers that distinguish blood from lymphatic vascular endothelium. This scenario is changing rapidly after the identification of the first lymphangiogenic factor, vascular endothelial growth factor C (VEGF-C). Increased expression of VEGF-C in primary tumors correlates with increased dissemination of tumor cells to regional lymph nodes in a variety of human carcinomas. Here I will review what is known about the mechanisms of lymphangiogenesis, particularly in the context of metastatic tumor spread, and will critically examine the role of VEGF-C in this process. However, despite recent progress in this field, it remains to be determined whether inhibition of lymphangiogenesis is a realistic therapeutic strategy for inhibiting tumor cell dissemination and the formation of metastasis.

Cell Adhesion↗
PubMedDate not supplied

Lymphatic vessels and lymphangiogenesis in female cancer: mechanisms, clinical impact and possible implications for anti-lymphangiogenic therapies (Review).

Lymphatic vessels play a crucial role in a variety of human cancers, since invasion of lymphatic vessels by tumor cells and subsequent development of lymph node metastases significantly influences prognosis of cancer patients and therefore represent an integral part of tumor staging. Recent evidence on the important influence of lymphangiogenetic growth factors on intralymphatic cancer growth and metastasis raises hopes that lymphatic vessels and factors inducing their growth could serve as an additional target for tumor therapy. Nevertheless, in contrast to blood vessel angiogenesis, the mechanisms of new lymphatic vessel formation in human cancers, i.e. lymphangiogenesis, are still relatively unclear. In addition, only little data exist so far on the quantification and impact of this lymphangiogenesis, evident by lymphatic microvessel density (LMVD), on the prognosis of cancer patients. With expectation of possible anti-lymphangiogenic therapies, this review focuses on the mechanisms of lymphangiogenesis in general, and especially on the role of lymphatic vessels in gynecological and breast cancer, which are the so far most detailed investigated malignancies with regard to lymphangiogenesis.

Endothelial Growth Factors↗
PubMed1997

Lack of lymphangiogenesis in human primary cutaneous melanoma. Consequences for the mechanism of lymphatic dissemination.

Cutaneous melanoma has an initial preference for lymphatic spread. Remarkably, melanoma progression toward this metastasizing phenotype is accompanied by intense blood vessel angiogenesis (hemangiogenesis), but lymphangiogenesis, the formation of new lymph vessels in the tumor, has never been reported. To investigate how primary melanoma cells interact with the existing lymphatic microvasculature, and whether lymphangiogenesis occurs, an immunostaining was developed that differentially decorates blood and lymph vessels in frozen tissue sections. The density and distribution of both these vessel types in and around thin (< or = 1.5 mm) and thick (> or = 1.5 mm) primary melanoma lesions and in normal and uninvolved skin were determined. Although especially in thick melanoma lesions a significant increase in blood vessel density was observed, lymphatic density remained unaltered, showing that lymphangiogenesis did not occur. Morphological analysis indicated, however, that melanoma progression is accompanied by a sequence of events that involves hemangiogenesis supporting tumor expansion, especially in the vertical growth phase. Often, stromal sepia are formed around the blood capillaries in the tumor neovasculature protecting them from invasion. Lymph vessels inside the tumor were infrequently observed. However, subepidermal lymph vessels often seemed to be entrapped and penetrated by the expanding tumor mass. In this way, hemangiogenesis, as the driving force behind tumor expansion, might indirectly increase the chance of lymphatic invasion in the absence of lymphangiogenesis. This model explains the paradox that, although melanoma metastasis seems to require angiogenesis, a consistent relation of prognosis with blood capillary density in primary cutaneous melanoma is lacking.

Biomarkers↗
PubMed2006

Lymphangiogenesis by blind-ended vessel sprouting is concurrent with hemangiogenesis by vascular splitting.

Development of effective vascular therapies requires the understanding of all modes of vessel formation involved in angiogenesis (here termed "hemangiogenesis") and lymphangiogenesis. Two major modes of vessel morphogenesis include sprouting of a new vessel from a preexisting vessel and splitting of a preexisting parent vessel into two offspring vessels. In the quail chorioallantoic membrane (CAM) during mid-development (embryonic days E6-E9), lymphangiogenesis progressed primarily via blind-ended vessel sprouting. Isolated lymphatic endothelial progenitor cells were recruited to the tips of growing vessels. During concurrent hemangiogenesis, parent blood vessels expanded from the capillary network and split into offspring vessels, accompanied by transient capillary expression of alpha smooth muscle actin (alphaSMA) and recruitment of polarized mural progenitor cells. Lymphatics and blood vessels were identified by confocal/fluorescence microscopy of vascular endothelial growth factor (VEGF) receptor VEGFR-2, alphaSMA (specific to CAM blood vessels), homeobox transcription factor Prox1 (specific to lymphatics), and the quail hematopoetic marker, QH-1. VEGFR-2 was expressed intensely in isolated cells and lymphatics, and moderately in blood vessels. Prox1 was absent from isolated progenitor cells prior to lymphatic recruitment. Exogenous vascular endothelial growth factor-165 (VEGF165) increased blood vessel density and anastomotic frequency without changing endogenous modes of vascular/lymphatic vessel formation or marker expression. Although VEGF165 is a key cellular regulator of hemangiogenesis and vasculogenesis, the role of VEGF165 in lymphangiogenesis is less clear. Interestingly, VEGF165 increased lymphatic vessel diameter and density as measured by novel Euclidean distance mapping, and the antimaturational dissociation of lymphatics from blood vessels, accompanied by lymphatic reassociation into homogeneous networks.

Animals↗
PubMed2007

DNA demethylation of vascular endothelial growth factor-C is associated with gene expression and its possible involvement of lymphangiogenesis in gastric cancer.

Previous studies have indicated that lymphangiogenesis in solid tumors is associated with lymphatic metastasis. Overexpression of Vascular endothelial growth factor (VEGF)-C plays a major role in lymphangiogenesis in cancers. In the present study, DNA methylation and expression of the VEGF-C gene was investigated in gastric cancer (GC). Four GC cell lines (MKN-45, MKN-74, HSC-39 and HSC-43) showed no expression of VEGF-C, and the VEGF-C gene was found to be methylated in these cells. In contrast, 7 GC cell lines (MKN-1, MKN-7, MKN-28, TMK-1, KATO-III, SH101-P4 and HSC-44PE) expressed VEGF-C, and the VEGF-C gene was found to be unmethylated in these cell lines. In addition, expression of VEGF-C mRNA was retrieved by treatment with a demethylating agent, Aza-2'-deoxycytidine. In GC tissue samples, bisulfite DNA sequencing analysis revealed that VEGF-C was not methylated in 9 (29.0%) of 31 GC samples, whereas demethylation was not observed in corresponding non-neoplastic mucosa samples. Overexpression of VEGF-C mRNA was observed in 16 (51.6%) of 31 GC samples by quantitative reverse transcription-polymerase chain reaction. Of the 9 GC cases with VEGF-C demethylation, 8 (88.9%) overexpressed VEGF-C. In contrast, of the 22 GC cases without VEGF-C demethylation, 8 (36.4%) overexpressed VEGF-C (p = 0.0155). Furthermore, lymphatic vessel density determined by immunostaining of podoplanin in GC tissues was associated with overexpression of VEGF-C (p < 0.0001). These results suggest that demethylation and activation of the VEGF-C gene is likely involved in lymphangiogenesis in GC.

Adenocarcinoma↗
PubMed2005

Evidence for lymphangiogenesis and its prognostic implications in head and neck squamous cell carcinoma.

Lymph node metastasis is a frequent reason for adverse clinical outcome in many epithelial neoplasms, including head and neck squamous cell carcinoma. The mechanisms underlying the capability of epithelial neoplasms to metastasize via lymphatic vessels have not yet been fully elucidated. There is great debate about whether cancer cells can metastasize by expansion and invasion of pre-existing peritumoral lymphatics or by the formation and invasion of new lymphatics within tumours (lymphangiogenesis). In order to investigate this issue, we examined 81 tissue specimens from patients with head and neck squamous cell carcinoma, using immunostaining for the specific lymphatic endothelium marker podoplanin, and assessed intratumoral and peritumoral lymphatic density. We also quantified lymphatic invasion and examined the possible associations of all the above parameters with clinicopathological features and outcome. Finally, we used double staining with podoplanin and the cell proliferation marker Ki-67 in order to evaluate lymphangiogenesis. High intratumoral and peritumoral lymphatic density were both significantly associated with the presence of lymph node metastasis at the time of diagnosis (chi2 test, p < 0.001 and p = 0.007, respectively) and there was a significant correlation between high intratumoral lymphatic density and lymphatic invasion. Patients with higher intratumoral lymphatic density exhibited shorter overall survival (log rank p < 0.001) and this correlation remained significant after multivariate analysis (Cox p = 0.04), indicating that intratumoral lymphatic density is an independent prognostic factor for mortality. Peritumoral lymphatic density had no influence on outcome. Double staining revealed the existence of proliferating intratumoral lymphatics, in which tumour emboli were occasionally observed. These results indicate that lymphangiogenesis indeed occurs in head and neck squamous cell carcinoma; that newly formed vessels are targets of invasion by cancer cells; and that intratumoral lymphatic density might be used as a criterion to separate patients at higher risk of an adverse clinical outcome.

Adult↗
PubMed2006

Inducible nitric oxide synthase activity correlates with lymphangiogenesis and vascular endothelial growth factor-C expression in head and neck squamous cell carcinoma.

Nitric oxide (NO) is a diatomic free radical molecule that has been implicated in tumour angiogenesis and progression of head and neck squamous cell carcinoma (HNSCC). However, the mechanism underlying the effect of NO on tumour spread remains largely unknown. Tumour lymphangiogenesis has recently received considerable attention and there is increasing evidence that it is relevant for metastasis to lymph nodes in HNSCC. Here, we study the correlation between inducible NOS synthase (iNOS) activity and lymphangiogenesis in a series of 60 HNSCCs and the possible involvement of the lymphangiogenic factor vascular endothelial growth factor (VEGF)-C. HNSCC presenting with lymph node metastasis had a significantly higher lymphatic vessel density in both the tumour mass and the peritumour area (p = 0.006 and p = 0.001, respectively). Similarly, tumours with lymph node metastasis showed greater lymphatic vessel area than tumours with no lymph node involvement (p = 0.001 for intratumour lymphatics and p < 0.001 for peritumour lymphatics). iNOS activity measured in specimens from the tumour periphery correlated strongly with both lymphatic vessel density and lymphatic vessel area (p = 0.01, rs = 0.45 and p < 0.001, rs = 0.725, respectively). Conversely, these correlations were not observed in specimens from the tumour core. In addition, VEGF-C mRNA expression was significantly elevated in tumours with high iNOS activity (p = 0.008, rs = 0.563), and VEGF-C expression correlated positively with the presence of lymph node metastases (p = 0.03). In vitro, in the A431 human squamous carcinoma cell line, exogenous and endogenous stimulation of the iNOS pathway led to up-regulation of VEGF-C, which was blocked by the NOS inhibitor L-NNA. Taken together, our results indicate that iNOS activity may promote lymphangiogenesis and spread to lymph nodes in HNSCC, with the possible involvement of VEGF-C.

Aged↗
PubMed2003

Lymphangiogenesis and tumor metastasis.

The lymphatic system transports interstitial fluid and macromolecules from tissues back to the blood circulation, and plays an important role in the immune response by directing the traffic of lymphocytes and antigen-presenting cells. The lymphatic system also constitutes one of the most important pathways of tumor dissemination. In many human cancers, increased expression of vascular endothelial growth factor-C (VEGF-C) is correlated with regional lymph node metastases. Experimental studies using transgenic mice overexpressing VEGF-C or xenotransplantation of VEGF-C-expressing tumor cells into immunodeficient mice have demonstrated a role for VEGF-C in tumor lymphangiogenesis and the subsequent formation of lymph node metastases. However, there is at present little evidence for lymphangiogenesis in human tumors and the relative importance of preexisting vs. newly formed lymphatics for metastasis in humans remains to be determined. Nonetheless, the striking correlation between the levels of VEGF-C in primary human tumors and lymph node metastases predicts its importance in cancer spread. Aside from promoting lymphangiogenesis, VEGF-C may also activate lymphatics to promote tumor cell chemotaxis, lymphatic intravasation and hence tumor cell dissemination.

Animals↗