Tumor-associated macrophages express lymphatic endothelial growth factors and are related to peritumoral 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.

Lymphatic neoangiogenesis in human renal allografts: results from sequential protocol biopsies

Neoangiogenesis of lymphatic vessels may be important for the cellular immune response in renal transplants. To determine the prevalence and chronology of lymph vessel proliferation and its relation to cellular infiltrates and allograft function, we analyzed sequential protocol biopsies (n = 162), taken at 6, 12 and 26 weeks after transplantation. Biopsies were stained with an antibody against podoplanin and lymphatic vessel density was quantified per square millimeter. The prevalence of lymph vessel-positive biopsies and the lymph vessel density were similar at 6, 12 and 26 weeks after transplantation. Biopsies with acute cellular rejection showed no significantly different lymph vessel density compared to those below the threshold for acute rejection or chronic allograft nephropathy. While lymphatic neoangiogenesis was equally prevalent in biopsies with and without infiltrates, the lymph vessel density was significantly higher in areas with cellular infiltrates than in areas without. Graft function at 1 year after transplantation was better in cases with lymph vessels in their infiltrates compared to cases with lymph vessel-free infiltrates. In conclusion, lymphangiogenesis not only shows a clear association with cellular infiltrates but might also have an impact on the pathogenicity of these cellular infiltrates.

Lymphatic vessels assessment in feline mammary tumours

Background

The lymphatic vessels play a crucial role in a variety of human cancers since tumour cell lymphatic invasion significantly influences prognosis. It is not known if pre-existing lymphatics are enough for tumour dissemination or de novo development is necessary. VEGFR-3 is an angiogenetic mediator for both lymphatic and blood vessels during embryonic development, and only for lymphatics after birth. VEGF is a mediator of both vasculogenesis and angiogenesis, regulates the growth of lymphatics in various experimental models, and is produced in many solid tumours. CD44 mediates hyaluronic acid (HA)-dependent cell adhesion: besides promoting invasion, this interaction also supports neoangiogenesis that indirectly stimulates tumour cell proliferation. The expression of VEGF-C (Vascular Endothelial Growth Factor – C), its receptor VEGFR-3 and CD44, were studied on feline mammary samples to assess the importance of lymphangiogenesis and lymphangiotrophism in neoplasia.

Methods

Samples were taken from six normal mammary glands (NMG), ten benign (BT) and 32 malignant (MT) tumours. Immunohistochemical laminin/VEGFR-3 double stain, VEGF-C and CD44 stains were applied to 4 μm-thick sections, and their expression evaluated in intratumoral/extratumoral and intramammary/extramammary fields.

Results

All groups revealed a higher number of lymphatics in the extratumoral/extramammary areas. VEGF-C expression in the epithelium paralleled the number of positive vessels in the NMG, BT and MT, whereas VEGF-C higher expression was noted in the intratumoral fields only in infiltrating MT. CD44 score was lower in extratumoral than intratumoral fields in tumours and showed a significant increase in extramammary/extratumoral fields from NMG to MT. Pearson test showed a significant and inversely proportional correlation between CD44 expression and the number of lymphatic vessels with VEGFR-3 in malignant infiltrating tumours.

Conclusion

The number of both VEGFR-3 positive and negative lymphatics in the extratumoral and extramammary stroma was significantly higher than intratumoral and intramammary fields respectively in the NMG, BT and MT. This suggests a scant biological importance of intratumoral lymphatics while their higher number is due to the concentration of existing vessels following compression of the extratumoral stroma in spite of a non demonstrable increase from NMG to MT. The tumour model employed provided no evidence of lymphangiogenesis, and metastasis in the regional lymph node develops following the spread through the pre-existing lymphatic network.

Cooperative and redundant roles of VEGFR-2 and VEGFR-3 signaling in adult lymphangiogenesis

Activation of vascular endothelial growth factor (VEGF) receptor-3 (VEGFR-3) by VEGF-C initiates lymphangiogenesis by promoting lymphatic proliferation and migration. However, it is unclear whether VEGFR-3 signaling is required beyond these initial stages, namely during the organization of new lymphatic endothelial cells (LECs) into functional capillaries. Furthermore, the role of VEGFR-2, which is also expressed on LECs and binds VEGF-C, is unclear. We addressed these questions by selectively neutralizing VEGFR-3 and/or VEGFR-2 for various time periods in an adult model of lymphangiogenesis in regenerating skin. While blocking either VEGFR-2 or VEGFR-3 with specific antagonist mAbs (DC101 and mF4-31C1, respectively) prior to lymphatic migration prevented lymphangiogenesis, blocking VEGFR-3 subsequent to migration did not affect organization into functional capillaries, and VEGFR-2 blocking had only a small hindrance on organization. These findings were confirmed in vitro using human LECs and anti-human antagonist mAbs (IMC-1121a and hF4-3C5): both VEGFR-2 and -3 signaling were required for migration and proliferation, but tubulogenesis in 3D cultures was unaffected by VEGFR-3 blocking and partially hindered by VEGFR-2 blocking. Furthermore, both in vitro and in vivo, while VEGFR-3 blocking had no effect on LEC organization, coneutralization of VEGFR-2, and VEGFR-3 completely prevented lymphatic organization. Our findings demonstrate that cooperative signaling of VEGFR-2 and -3 is necessary for lymphatic migration and proliferation, but VEGFR-3 is redundant with VEGFR-2 for LEC organization into functional capillaries.

First international consensus on the methodology of lymphangiogenesis quantification in solid human tumours

The lymphatic system is the primary pathway of metastasis for most human cancers. Recent research efforts in studying lymphangiogenesis have suggested the existence of a relationship between lymphatic vessel density and patient survival. However, current methodology of lymphangiogenesis quantification is still characterised by high intra- and interobserver variability. For the amount of lymphatic vessels in a tumour to be a clinically useful parameter, a reliable quantification technique needs to be developed. With this consensus report, we therefore would like to initiate discussion on the standardisation of the immunohistochemical method for lymphangiogenesis assessment.

Targeting receptor tyrosine kinase on lymphatic endothelial cells for the therapy of colon cancer lymph node metastasis

Oral treatment with the dual-receptor tyrosine kinase inhibitor AEE788 effectively reduces the number of peritumoral lymphatic vessels and the incidence of lymph node metastasis in nude mice with human HT29 colon cancer cells growing in the cecum. Whether inhibition of lymph node metastasis in colon cancer can be achieved by directly targeting lymphatic endothelial cells remains unclear. Using a microsurgical approach, we generated conditionally immortalized lymphatic endothelial cell lines from the H-2K(b)-tsA58 mouse mesentery and characterized these cells for the expression of lymphatic endothelial cell markers. Lymphatic endothelial cells were stimulated in culture with an array of tumor cell-produced cytokines, leading to the identification of redundant pathways for proliferation and survival. Treatment with AEE788 decreased the migration, proliferation, and survival of lymphatic endothelial cells, demonstrating that oral treatment with AEE788 effectively decreases the incidence of colon cancer lymphatic metastasis due, in part, to the direct inhibition of lymphatic endothelial cell signaling.

The human renal lymphatics under normal and pathological conditions

Ishikawa Y, Akasaka Y, Kiguchi H, Akishima-Fukasawa Y, Hasegawa T, Ito K, Kimura-Matsumoto M, Ishiguro S, Morita H, Sato S, Soh S & Ishii T (2006) Histopathology49, 265–273

The human renal lymphatics under normal and pathological conditions

Vascular endothelial growth factor-C accelerates diabetic wound healing

Diabetes impairs numerous aspects of tissue repair. Failure of wound angiogenesis is known to delay diabetic wound healing, whereas the importance of lymphangiogenesis for wound healing is unclear. We have examined whether overexpression of vascular endothelial growth factor (VEGF)-C via an adenoviral vector could improve the healing of full-thickness punch biopsy wounds in genetically diabetic (db/db) mice. We found that VEGF-C enhanced angiogenesis and lymphangiogenesis in the wound and significantly accelerated wound healing in comparison to the control wounds. VEGF-C also recruited inflammatory cells, some of which expressed VEGFR-3. On the other hand, when the function of endogenous VEGF-C/VEGF-D was blocked with a specific inhibitor, wound closure was delayed even further. These results suggest a function for VEGF-C in wound healing and demonstrate the therapeutic potential of VEGF-C in the treatment of diabetic wounds.

Detection of Lymphatic Invasion in Early Stage Primary Colorectal Cancer with the Monoclonal Antibody D2-40

PURPOSE

The purpose of this study was to investigate the presence of lymphatic invasion detected by D2-40 immunostaining compared to conventional hematoxylin-eosin (HE) staining in primary colorectal cancer (CRC) and the development of focal new lymphangiogenesis and peritumoral lymphatic proliferation in relation to the tumor stages. Additionally, we analyzed the relation of peritumoral inflammatory reaction (PIR) to tumor stages in CRC. The identification of new categories of patients with high-risk CRC would be very helpful in improving treatment strategies and patient outcome especially in early CRC.

PATIENTS AND METHOD

Biopsies were taken from 41 patients with colorectal adenocarcinomas at different stages of disease. Immunohistochemistry was performed on paraffin-embedded sections. First, the whole section was screened for the presence of lymphatic invasion and PIR with routine HE staining. After analysis of the HE-stained slides, the slides were destained and reused for immunohistochemistry with the D2-40 monoclonal antibody. D2-40-immunostained sections were screened for the presence of lymphatic invasion, the proliferation of lymphatic vessels and focally newly developed lymph vessels.

RESULTS

Using the D2-40 antibody for immunostaining, our results demonstrate a significantly higher detection (p < 0.05) of lymphatic vessel invasion compared to routine HE staining in primary CRC. 22% more patients with lymphatic vessel invasion could be identified compared to routine HE staining, especially in node-negative tumor stage (UICC II). The positive predictive value of lymphatic invasion evaluated by D2-40 immunostaining to predict lymph node metastasis is 92% (negative predictive value 81%). High PIR was shown in UICC stage I and II. These infiltrations were rarely seen in UICC stage III and were absent in UICC stage IV. Higher UICC tumor stage is associated with a higher rate of focally newly developed lymphatic vessels. In UICC stage I we found peritumoral lymphatic vessel proliferation only in one case (14%) and in UICC stage II no case was found. 47% of the cases in UICC stage III and 50% of the cases in UICC stage IV showed focal peritumoral lymphatic vessel proliferation.

CONCLUSIONS

Immunostaining with D2-40 significantly increased the detection rate of lymphatic invasion compared to conventional HE staining in primary CRC. The D2-40 antibody specific for lymphatic endothelium cells has the potential for a prognostic marker in early stage CRC. Further prospective studies are necessary to evaluate the prognostic value of lymphatic invasion and the induction of tumor lymphangiogenesis and its role in human cancer progression.

Lymphangiogenesis in the bone-implant interface of orthopedic implants: importance and consequence

The lymphatic system plays an essential physiological role in homeostasis, interstitial fluid composition, and immunity while impaired lymphatic function has been implicated in a number of pathological conditions, including arthritis and delayed wound healing. This study investigated lymphatic capillary growth and lymphangiogenesis pathways in the bone-implant interface from patients with aseptically loosened prosthetic joints. The newly developed lymphatic specific marker, podoplanin, has enabled the first demonstration of lymphatic capillaries in peri-prosthetic tissues (60% of cases contained podoplanin positive vessels). The pro-lymphangiogenic factor (VEGF-C) and its receptor VEGFR-3 showed high level of expression in these tissues, (often in areas of high levels of wear debris). However despite the upregulation of the lymphangiogenesis pathway by a VEGF-C/VEGFR-3-mediated mechanism, there were relatively few podoplanin positive lymphatic vessels in the bone-implant interface (3.4% of total vessels). This may have important pathological consequences in terms of perpetuating inflammation and edema by inhibiting the removal of macromolecules, cells, and interstitial fluid. The identification of lymphatic vessels with internalized polyethylene wear particles provides evidence of this route of wear debris transportation to distal sites. This paper highlights the importance of lymphatic vessels in the maintenance of local and distal inflammatory responses to prosthetic wear particles.

Dual role of macrophages in tumor growth and angiogenesis

During the neoplastic progression, macrophages as well as dendritic and NK cells are attracted into the tumor site and initiate the immune response against transformed cells. They activate and present tumor antigens to T cells, which are then activated to kill tumor cells. However, tumor cells are often capable of escaping the immune machinery. As the immune surveillance is not sufficient anymore, tumor-associated macrophages contribute to tumor progression. It is notable that tumor-associated macrophages promote the proliferation of tumor cells directly by secreting growth factors. They also participate in tumor progression by acting on endothelial cells and thus promoting the neovascularization of the tumor. Tumor-associated macrophages are indeed key protagonists during angiogenesis and promote each step of the angiogenesis cascade.

Targeting lymphangiogenesis to prevent tumour metastasis

Recent studies involving animal models of cancer and clinicopathological analyses of human tumours suggest that the growth of lymphatic vessels (lymphangiogenesis) in or nearby tumours is associated with the metastatic spread of cancer. The best validated molecular signalling system for tumour lymphangiogenesis involves the secreted proteins vascular endothelial growth factor-C (VEGF-C) and VEGF-D that induce growth of lymphatic vessels via activation of VEGF receptor-3 (VEGFR-3) localised on the surface of lymphatic endothelial cells. In this review, we discuss the evidence supporting a role for this signalling system in the spread of cancer and potential approaches for blocking this system to prevent tumour metastasis.

Tumor Lymphangiogenesis in Transitional Cell Carcinoma of the Upper Urinary Tract: Association With Clinicopathological Features and Prognosis

PURPOSE

Lymph node metastasis is an important prognostic factor in many types of cancer. Recently several specific markers for lymphatic endothelium were developed that facilitate the quantification of lymphangiogenesis in human cancer tissues. We investigated the clinical and prognostic significance of lymphangiogenesis in patients with transitional cell carcinoma of the upper urinary tract.

MATERIALS AND METHODS

We measured lymph vessel density and relative lymphatic vascular area in 125 specimens by quantitative immunohistochemical staining for D2-40 antibody (DakoCytomation, Glostrup, Denmark). These parameters were examined in the intratumor and peritumor areas, and measured using image analysis software.

RESULTS

Peritumor lymph vessel density and peritumor lymphatic vascular area correlated with lymph node metastasis and tumor grade. In the intratumor area lymphatic vessels were detected in only 16.0% of specimens. However, the presence of intratumor lymphatic vessels was associated with lymph node metastasis (p = 0.002). Multivariate analysis identified high peritumor lymphatic vascular area and the presence of intratumor lymphatic vessels as significant and independent factors of metastasis-free survival after surgery (OR = 5.11, p = 0.020 and OR = 2.92, p = 0.025, respectively). Multivariate analysis also identified the presence of intratumor lymphatic vessels as the only independent predictive factor of cause specific survival (OR = 3.89, p = 0.049).

CONCLUSIONS

Lymphangiogenesis may have important roles in tumor metastasis and survival in patients with transitional cell carcinoma of the upper urinary tract. Quantification of lymphatic vessels, especially peritumor lymphatic vascular area and intratumor lymphatic vessels, was useful for predicting metastasis-free survival. In addition, the presence of intratumor lymphatic vessels was an independent predictor of cause specific survival.

Tumor and lymph node lymphangiogenesis-impact on cancer metastasis

The extent of lymph node (LN) metastasis is a major determinant for the staging and the prognosis of most human malignancies and often guides therapeutic decisions. Although the clinical significance of LN involvement is well documented, little has been known about the molecular mechanisms that promote tumor spread via lymphatic vessels to sentinel and distal LN and beyond. However, recent discoveries have identified novel lymphatic-specific markers, and the newly discovered lymphangiogenesis factors vascular endothelial growth factor-C (VEGF-C) and VEGF-D were found to promote tumor-associated lymphatic vessel growth in mouse tumor models, leading to enhanced tumor spread to sentinel LN. Our recent findings indicate that VEGF-A also acts as a potent tumor lymphangiogenesis factor that promotes lymphatic tumor spread. VEGF-A overexpressing primary tumors induced sentinel LN lymphangiogenesis even before metastasizing and maintained their lymphangiogenic activity after metastasis to draining LN. Our recent studies showed that primary human melanomas that later metastasized were characterized by increased lymphangiogenesis and that the degree of tumor lymphangiogenesis can serve as a novel predictor of LN metastasis and overall patient survival, independently of tumor thickness. Tumor lymphangiogenesis also significantly predicted the presence of sentinel LN metastases at the time of surgical excision of the primary melanoma. Together, these findings suggest that tumor lymphangiogenesis actively contributes to cancer dissemination, that blockade of lymphatic vessel growth might inhibit tumor metastasis to LN, and that the extent of tumor-associated lymphangiogenesis could serve as a novel, prognostic parameter for the metastatic risk of human cancers.

The balance of VEGF-C and VEGFR-3 mRNA is a predictor of lymph node metastasis in non-small cell lung cancer

A positive association between vascular endothelial growth factor-C (VEGF-C) expression and lymph node metastasis has been reported in several cancers. However, the relationship of VEGF-C and lymph node metastasis in some cancers, including non-small cell lung cancer (NSCLC), is controversial. We evaluated the VEGF-C and vascular endothelial growth factor receptor-3 (VEGFR-3) expression in NSCLC samples from patients who had undergone surgery between 1998 and 2002 using real-time quantitative RT–PCR and immunohistochemical staining. We failed to find a positive association between VEGF-C and VEGFR-3 mRNA expression and lymph node metastasis in NSCLC. An immunohistological study demonstrated that VEGF-C was expressed not only in cancer cells, but also in macrophages in NSCLC, and that VEGFR-3 was expressed in cancer cells, macrophages, type II pneumocytes and lymph vessels. The VEGF-C/VEGFR-3 ratio of the node-positive group was significantly higher than that of the node-negative group. Immunohistochemical staining showed that VEGFR-3 was mainly expressed in cancer cells. The immunoreactivity of VEGF-C and VEGFR-3 was roughly correlated to the mRNA levels of VEGF-C and VEGFR-3 in real-time PCR. VEGF-C mRNA alone has no positive association with lymph node metastasis in NSCLC. The VEGF-C/VEGFR-3 ratio was positively associated with lymph node metastasis in NSCLC. This suggests that VEGF-C promotes lymph node metastasis while being influenced by the strength of the VEGF-C autocrine loop, and the VEGF-C/VEGFR-3 ratio can be a useful predictor of lymph node metastasis in NSCLC.

Renal lymphatics, and lymphatic involvement in sinus vein invasive (pT3b) clear cell renal cell carcinoma: a study of 40 cases

Although renal sinus vein invasion is the most common site of extrarenal involvement in clear cell renal cell carcinoma (CC), CC also spreads by lymphatics. As cortical lymphatics drain into the sinus, some involved sinus structures may be lymphatics, not veins. This possibility was investigated with podoplanin, a specific lymphatic endothelial marker, in 40 CC with sinus vein invasion. Ten blocks of uninvolved kidney, serving as controls, showed lymphatics within the adventitia of midcortical intralobular arteries. Lymphatics became more numerous and enlarged with progression towards the medulla. No lymphatics were among glomeruli or within the medulla unless associated with inflammation. The largest lymphatics occurred within the sinus, and were also noted within pelvic muscularis, and media of large veins. Intralymphatic tumor was observed and divided into two Groups. Group 1 (four cases) involved lymphatics within the invasive edge of tumors lacking a pseudocapsule. The lymphatics were small (0.045-0.19 mm), irregularly shaped, often incomplete, and contained single cells or small clusters of tumor cells. Group 2 (four cases) involved sinus lymphatics separate from tumor. One case each also involved adventitial lymphatics of an intralobular artery, the muscularis of the renal pelvis, and media of a muscular vein. The intralymphatic tumor in Group 2 often appeared discohesive, not endothelial cell invested, and larger than in Group 1 (0.4-0.5 mm). Conversely, tumor within muscular veins was cohesive, contained a capillary plexis, and was endothelial cell invested. In conclusion, intralymphatic tumor can be demonstrated in CC. Lymphatic involvement is less frequent than venous involvement and involves smaller structures. The potential for lymphatic spread may not be equal among involved lymphatics. Small peritumoral lymphatics may be destined for destruction by tumor growth. However, involved lymphatics within sinus and associated with renal pelvis, are likely sources for lymphatic spread and lymph node metastases.

Characterization of lymphangiogenesis in a model of adult skin regeneration

To date, adult lymphangiogenesis is not well understood. In this study we describe the evolution of lymphatic capillaries in regenerating skin and correlate lymphatic migration and organization with the expression of matrix metalloproteinases (MMPs), immune cells, the growth factors VEGF-A and VEGF-C, and the heparan sulfate proteogylcan perlecan, a key component of basement membrane. We show that while lymphatic endothelial cells (LECs) migrate and organize unidirectionally, in the direction of interstitial fluid flow, they do not sprout into the region but rather migrate as single cells that later join together into vessels. Furthermore, in a modified "shunted flow" version of the model, infiltrated LECs fail to organize into functional vessels, indicating that interstitial fluid flow is necessary for lymphatic organization. Perlecan expression on new lymphatic vessels was only observed after vessel organization was complete and also appeared first in the distal region, consistent with the directionality of lymphatic migration and organization. VEGF-C expression peaked at the initiation of lymphangiogenesis but was reduced to lower levels throughout organization and maturation. In mice lacking MMP-9, lymphatics regenerated normally, suggesting that MMP-9 is not required for lymphangiogenesis, at least in mouse skin. This study thus characterizes the process of adult lymphangiogenesis and differentiates it from sprouting blood angiogenesis, verifies its dependence on interstitial fluid flow for vessel organization, and correlates its temporal evolution with those of relevant environmental factors.

Lymphatic or hematogenous dissemination: how does a metastatic tumor cell decide?

The formation of distant metastases is the deadliest phase of cancer progression. Although numerous studies have identified genes and mechanisms that affect metastasis after tumors have reached secondary sites, our knowledge about how cancer cells initially gain access to systemic circulation is limited. Since tumors can enter the blood directly by intravasating into venous capillaries or indirectly via lymphatics, it is important to evaluate the relative contributions of both pathways as routes of egress from the primary site. Insights into tumor and stromal factors governing the intravasation process may help explain why certain tumors exhibit "preferred" pathways for metastatic dissemination, both clinically and in experimental animal models.

Monocyte chemoattractant protein-1 transfection induces angiogenesis and tumorigenesis of gastric carcinoma in nude mice via macrophage recruitment

PURPOSE

Monocyte chemoattractant protein-1 (MCP-1) is a chemokine that has various roles in tumor development and progression. We previously reported that expression of MCP-1 is associated with macrophage infiltration and tumor vessel density in human gastric carcinomas. The present study was undertaken to obtain direct evidence that MCP-1 participates in recruitment of macrophages and induction of angiogenesis.

EXPERIMENTAL DESIGN

We did transfection experiments to analyze the role of MCP-1 in tumorigenicity and angiogenesis in gastric carcinoma in nude mice. The human MCP-1 gene cloned into the BCMGS-Neo expression vector was transfected into the human gastric carcinoma TMK-1 cell line. We examined tumor volumes with the ectopic s.c. xenograft model and tumorigenicity with the orthotopic gastric xenograft model. We determined intratumor microvessel counts and tumor-infiltrating macrophage counts by immunohistochemical staining.

RESULTS

There was no difference in in vitro proliferation between MCP-1-transfected TMK-1 cells and mock-transfected (control) cells; however, MCP-1 transfectants induced tumor growth in ectopic xenografts and increased tumorigenicity and induced lymph node metastases and ascites in orthotopic xenografts. In both ectopic and orthotopic xenograft models, strong infiltration of macrophages was observed within and around the tumors after implantation of MCP-1 transfectants whereas fewer macrophages were seen after inoculation of control cells. The microvessel density was significantly higher in tumors produced by MCP-1 transfectants than in control tumors.

CONCLUSIONS

MCP-1 produced by gastric carcinoma cells may regulate angiogenesis via macrophage recruitment. MCP-1 may be a potential target for antiangiogenic therapy for gastric carcinoma.

Bacteria and cancer: cause, coincidence or cure? A review

Research has found that certain bacteria are associated with human cancers. Their role, however, is still unclear. Convincing evidence links some species to carcinogenesis while others appear promising in the diagnosis, prevention or treatment of cancers. The complex relationship between bacteria and humans is demonstrated by Helicobacter pylori and Salmonella typhi infections. Research has shown that H. pylori can cause gastric cancer or MALT lymphoma in some individuals. In contrast, exposure to H. pylori appears to reduce the risk of esophageal cancer in others. Salmonella typhi infection has been associated with the development of gallbladder cancer; however S. typhi is a promising carrier of therapeutic agents for melanoma, colon and bladder cancers. Thus bacterial species and their roles in particular cancers appear to differ among different individuals. Many species, however, share an important characteristic: highly site-specific colonization. This critical factor may lead to the development of non-invasive diagnostic tests, innovative treatments and cancer vaccines.

Hypoxia inducible factor-1α correlates with VEGF-C expression and lymphangiogenesis in breast cancer

The transcription factor Hypoxia inducible factor-1alpha (HIF-1alpha) plays a crucial role in tumor progression by regulating angiogenesis, cell survival and drug resistance. HIF-1alpha is also implicated in biological functions under normoxic conditions and recent data provide evidence for a possible role in tumor lymphangiogenesis by regulating the lymphatic vascular endothelial growth factor-C (VEGF-C). In breast cancer, lymphatic vessel invasion (LVI) by tumor cells and subsequent metastasis to axillary lymph nodes is a critical point in progression of the disease with severe therapeutical and prognostic implications. Aim of this study is to investigate the role of HIF-1alpha in VEGF-C expression, lymphangiogenesis, and LVI in lymph node positive breast cancer. Lymphatic microvessel density (LMVD), LVI, HIF-1alpha and VEGF-C protein-expression were evaluated by immunohistochemistry in 119 cases of lymph node positive invasive breast cancer. There was a significant correlation between HIF-1alpha and VEGF-C (p = 0.026, r = 0.204, Spearman's coefficient of correlation). Further a significant association between HIF-1alpha-expression and the amount of peritumoral lymphangiogenesis LMVD was seen (p = 0.014, Mann-Whitney test). LMVD correlated significantly with LVI (p<0.001, Mann-Whitney test). HIF-1alpha was an independent prognostic factor for overall and disease free survival in uni- and multivariate analysis (p = 0.027, 0.029, 0.025, respectively, Cox regression). Our data provide evidence for a possible role of HIF-1alpha as regulator of tumor-associated lymphangiogenesis in human breast cancer and emphasizes the promising status of HIF-1alpha as a therapeutical target against tumor progression and metastasis.

Tumour-associated macrophages are a distinct M2 polarised population promoting tumour progression: potential targets of anti-cancer therapy

Tumour-associated macrophages (TAM) represent the major inflammatory component of the stroma of many tumours, and can affect different aspects of the neoplastic tissue. Many observations indicate that TAM express several M2-associated pro-tumoural functions, including promotion of angiogenesis, matrix remodelling and suppression of adaptive immunity. The pro-tumoural role of TAM in cancer is further supported by clinical studies that found a correlation between the high macrophage content of tumours and poor patient prognosis. Evidence is presented here supporting the view that TAM represent a unique and distinct M2-skewed myeloid population and are a potential target for anti-cancer therapy.

Tumour lymphangiogenesis is a possible predictor of sentinel lymph node status in cutaneous melanoma: a case-control study

BACKGROUND

Cutaneous melanoma spreads preferentially through the lymphatic route and sentinel lymph node (SLN) status is regarded as the most important predictor of survival.

AIMS

To evaluate whether tumour lymphangiogenesis and the expression of vascular endothelial growth factor C (VEGF-C) is related to the risk of SLN metastasis and to clinical outcome in a case-control series of patients with melanoma.

METHODS

Forty five invasive melanoma specimens (15 cases and 30 matched controls) were investigated by immunostaining for the lymphatic endothelial marker D2-40 and for VEGF-C. Lymphangiogenesis was measured using computer assisted morphometric analysis.

RESULTS

Peritumorous lymphatic vessels were more numerous, had larger average size, and greater relative area than intratumorous lymphatics. The number and area of peritumorous and intratumorous lymphatics was significantly higher in melanomas associated with SLN metastasis than in non-metastatic melanomas. No significant difference in VEGF-C expression by neoplastic cells was shown between metastatic and non-metastatic melanomas. Using logistic regression analysis, intratumorous lymphatic vessel (LV) area was the most significant predictor of SLN metastasis (p = 0.04). Using multivariate analysis, peritumorous LV density was an independent variable affecting overall survival, whereas the intratumorous LV area approached significance (p = 0.07).

CONCLUSIONS

This study provides evidence that the presence of high peritumorous and intratumorous lymphatic microvessel density is associated with SLN metastasis and shorter survival. The intratumorous lymphatic vessel area is the most significant factor predicting SLN metastasis. The tumour associated lymphatic network constitutes a potential criterion in the selection of high risk patients for complementary treatment and a new target for antimelanoma therapeutic strategies.

Tumor-induced lymphangiogenesis: a target for cancer therapy?

Recent advances in understanding the biology of lymphangiogenesis, the new growth of lymphatic vessels, have cast new light on the molecular basis of metastasis to regional lymph nodes. The receptor tyrosine kinase VEGFR-3 is virtually exclusively expressed on lymphatic but not blood endothelium in the adult, and activation of VEGFR-3 by its ligands VEGF-C and VEGF-D is sufficient to induce lymphangiogenesis. Correlative studies with human tumors and functional studies using animal tumor models show that increased levels of VEGF-C or VEGF-D in tumors lead to enhanced numbers of lymphatic vessels in the vicinity of tumors, which in turn promotes metastasis to regional lymph nodes by providing a greater number of entry sites into the lymphatic system for invading tumor cells. These findings have prompted studies to investigate whether inhibitors of VEGFR-3 activation might represent novel therapeutic agents for the suppression of metastasis. However, a number of points regarding the therapeutic potential of anti-lymphangiogenic treatments in the context of cancer remain to be addressed. The spectrum and relative importance of molecules that induce lymphangiogenesis and the regulation of their expression during tumor progression, the reversibility of tumor-induced lymphangiogenesis, and possible side-effects of anti-lymphangiogenesis-based therapies all need to be investigated. Most importantly, the extent to which lymph node metastases contribute to the formation of metastases in other organs remains to be elucidated. These aspects are the focus of this review, and their investigation should serve as a roadmap to possible translational application.

Lymphangiogenesis and Angiogenesis in Bladder Cancer: Prognostic Implications and Regulation by Vascular Endothelial Growth Factors-A, -C, and -D

PURPOSE

Lymph vessel density (LVD) and microvessel density (MVD) correlate with the malignant potential of tumors and patient survival. Vascular endothelial growth factors (VEGF)-A, VEGF-C, and VEGF-D could modulate LVD and MVD. We investigated the clinical and prognostic significance of LVD and MVD on lymphangiogenic and angiogenic function of VEGF-A, VEGF-C, and VEGF-D in human bladder cancer.

EXPERIMENTAL DESIGN

We reviewed tissue samples from patients with nonmetastatic bladder cancer who had undergone transurethral resections (n = 126). The densities of D2-40-positive vessels (LVD) and CD34-positive vessels (MVD) were measured by a computer-aided image analysis system. Expression of VEGF-A, VEGF-C, and VEGF-D was examined by immunohistochemistry; survival analyses and their independent roles were investigated using multivariate analysis models.

RESULTS

LVD was associated with tumor grade but not with pT stage. LVD was associated with metastasis-free survival (log rank P = 0.039), but was not an independent prognostic factor. Although MVD affected survival, the combination of high LVD and high MVD in tumors was an independent predictor of metastasis-free survival. Although VEGF-C expression was positively associated with both LVD and MVD, VEGF-D was associated only with LVD. VEGF-A expression was associated with MVD in univariate analysis, however, it was not an independent factor.

CONCLUSIONS

Lymphangiogenesis and angiogenesis influence metastasis-free survival, and are regulated by VEGF-C and/or VEGF-D. Our results suggest that LVD and MVD are useful tools for the selection of postoperative management and treatment strategies in patients with bladder cancer.

Peritumoral lymphatic vessel density and vascular endothelial growth factor C expression in early-stage squamous cell carcinoma of the uterine cervix

PURPOSE

Lymphatic invasion and nodal metastasis plays a major role in the spread of cervical cancer; however, little is known about the mechanisms whereby tumor cells enter the lymphatic system.

EXPERIMENTAL DESIGN

We examined the intra- and peritumoral lymphatic vessel density (LVD) using D2-40 immunohistochemistry in 111 cervical squamous cell carcinomas and correlated them with vascular endothelial growth factor (VEGF)-C expression, clinicopathologic tumor features, and outcome.

RESULTS

Compared with benign cervix, intratumoral and peritumoral LVD was significantly increased (P < 0.0001). Peritumoral LVD was significantly higher than intratumoral LVD (P = 0.009). High peritumoral, but not intratumoral, LVD showed significant correlation with high tumor stage, lymphatic invasion, and nodal metastasis. VEGF-C showed increased expression at the invasive edge compared with the center of tumors (P < 0.0001) and correlated with high peritumoral LVD, lymphatic invasion, and nodal metastasis. High peritumoral LVD and VEGF-C expression at the invasive edge of tumors were associated with poor overall and recurrence-free survival in univariate analysis. In multivariate analysis, peritumoral LVD was the only independent term predictive of overall survival.

CONCLUSIONS

Our findings suggest a potential role for VEGF-C in tumor-induced lymphangiogenesis represented by high peritumoral LVD, which may be one of the mechanisms leading to lymphatic invasion and metastatic spread. High peritumoral LVD may be an independent prognostic factor in early-stage cervical cancer.

Distinct Role of Macrophages in Different Tumor Microenvironments

Macrophages are prominent in the stromal compartment of virtually all types of malignancy. These highly versatile cells respond to the presence of stimuli in different parts of tumors with the release of a distinct repertoire of growth factors, cytokines, chemokines, and enzymes that regulate tumor growth, angiogenesis, invasion, and/or metastasis. The distinct microenvironments where tumor-associated macrophages (TAM) act include areas of invasion where TAMs promote cancer cell motility, stromal and perivascular areas where TAMs promote metastasis, and avascular and perinecrotic areas where hypoxic TAMs stimulate angiogenesis. This review will discuss the evidence for differential regulation of TAMs in these microenvironments and provide an overview of current attempts to target or use TAMs for therapeutic purposes.

Lymphatic endothelial progenitor cells contribute to de novo lymphangiogenesis in human renal transplants

De novo lymphangiogenesis influences the course of different human diseases as diverse as chronic renal transplant rejection and tumor metastasis. The cellular mechanisms of lymphangiogenesis in human diseases are currently unknown, and could involve division of local preexisting endothelial cells or incorporation of circulating progenitors. We analyzed renal tissues of individuals with gender-mismatched transplants who had transplant rejection and high rates of overall lymphatic endothelial proliferation as well as massive chronic inflammation. Donor-derived cells were detected by in situ hybridization of the Y chromosome. We compared these tissues with biopsies of essentially normal skin and intestine, and two rare carcinomas with low rates of lymphatic endothelial proliferation that were derived from individuals with gender-mismatched bone marrow transplants. Here, we provide evidence for the participation of recipient-derived lymphatic progenitor cells in renal transplants. In contrast, lymphatic vessels of normal tissues and those around post-transplant carcinomas did not incorporate donor-derived progenitors. This indicates a stepwise mechanism of inflammation-associated de novo lymphangiogenesis, implying that potential lymphatic progenitor cells derive from the circulation, transmigrate through the connective tissue stroma, presumably in the form of macrophages, and finally incorporate into the growing lymphatic vessel.

The lymphatic vasculature: recent progress and paradigms

The field of lymphatic research has been recently invigorated by the identification of genes and mechanisms that control various aspects of lymphatic development. We are beginning to understand how, starting from a subgroup of embryonic venous endothelial cells, the whole lymphatic system forms in a stepwise manner. The generation of genetically engineered mice with defects in different steps of the lymphangiogenic program has provided models that are increasing our understanding of the lymphatic system in health and disease. This knowledge, in turn, should lead to the development of better diagnostic methods and treatments of lymphatic disorders and tumor metastasis.

Expression pattern of the lymphatic and vascular markers VEGFR-3 and CD31 does not predict regional lymph node metastasis in cutaneous melanoma

Malignant melanoma of the skin preferentially metastasises via the lymphatic system. Novel molecular biomarkers, which are involved in malignant transformation, proliferation, angiogenesis and lymphangiogenesis, are currently under investigation to elucidate the risk for lymph node metastasis. To this end, the vascular endothelial growth factors VEGF-C and VEGF-D have been identified to promote lymphangiogenesis and lymphatic spread through activation of its receptor, Vascular endothelial growth factor receptor-3 (VEGFR-3). Prompted by this assumption, we estimated the degree of lymphangiogenesis by semiquantitative immunohistochemical analysis of the expression of VEGFR-3 and the panvascular marker CD31 in primary cutaneous melanoma (n=26) and correlated these findings with the sentinel lymph node (SLN) status. The cohort was selected for matched prognostic markers in SLN-positive and SLN-negative patients. In contrast to other studies, we observed an inverse correlation between expression of these markers with lymph node metastases. Additionally, no difference between intratumoral versus peritumoral CD31- or VEGFR-3 expression on blood vessels versus lymphatic capillaries could be detected. Interestingly, VEGFR-3 upregulation was not restrained to vascular structures but also appeared on tumor cells. In summary, in our series VEGFR-3/CD31 immunohistochemical staining of primary melanoma does not serve as a valid marker to predict lymph node involvement. As lymphatic spread is a complex, multi-step process, several different biomarkers have to be combined to define new prognostic subgroups in cutaneous melanoma.

Vascular endothelial growth factor-a promotes peritumoral lymphangiogenesis and lymphatic metastasis

Metastases are commonly found in the lymphatic system. The molecular mechanism of lymphatic metastasis is, however, poorly understood. Here we report that vascular endothelial growth factor (VEGF)-A stimulated lymphangiogenesis in vivo and that overexpression of VEGF-A in murine T241 fibrosarcomas induced the growth of peritumoral lymphatic vessels, which occasionally penetrated into the tumor tissue. As a result of peritumoral lymphangiogenesis, metastases in lymph nodes of mice were detected. VEGF-A-overexpressing tumors contained high numbers of infiltrating inflammatory cells such as macrophages, which are known to express VEGF receptor (VEGFR)-1. It seemed that in the mouse cornea, VEGF-A stimulated lymphangiogenesis through a VEGF-C/-D/VEGFR-3-independent pathway as a VEGFR-3 antagonist selectively inhibited VEGF-C-induced, but not VEGF-A-induced, lymphangiogenesis. Our data show that VEGF-A contributes to lymphatic mestastasis. Thus, blockage of VEGF-A-induced lymphangiogenesis may provide a novel approach for prevention and treatment of lymphatic metastasis.

Lymphatic spread of ductal pancreatic adenocarcinoma is independent of lymphangiogenesis

Early lymph node metastasis is common in pancreatic ductal adenocarcinoma (PDAC). The present study has examined the relationship of lymphatic spread to lymph vessel development and the expression of lymphangiogenic cytokines in a series of well-characterized PDACs. The hot spot method revealed the intratumoural and peritumoural lymphatic vessel density (LVD) to be slightly higher in PDACs than in the normal pancreas. The average intratumoural LVD, however, was strikingly decreased. There was no overexpression of vascular endothelial growth factor (VEGF)-C and VEGF-D in PDACs compared with the normal pancreas. LVD and expression of lymphangiogenic cytokines were not related to any of the biological tumour features or to patient survival. Three orthotopic nude mouse PDAC models did not reveal any increase in tumour-associated LVD, despite a high rate of lymph node metastasis. Lymph vessel proliferation was comparable in PDAC and chronic pancreatitis, in both humans and mice. In conclusion, increased lymphangiogenic activity is not required for and does not significantly affect the lymphatic spread of PDAC. The reduced number of human and murine intratumoural lymph vessels indicates that lymphatic metastasis takes place predominantly via peritumoural lymphatic vessels. The weak expression of lymphangiogenic cytokines in neoplastic cells and lymphatic vessel proliferation in peritumoural regions and chronic pancreatitis indicate that inflammation may be the reason for the low rate of lymphangiogenesis.

Inflammation-induced lymphangiogenesis in the cornea arises from CD11b-positive macrophages

In the inflamed cornea, there is a parallel outgrowth of blood and lymphatic vessels into the normally avascular cornea. We tested whether adaptive and/or innate immune cells were actively involved in the genesis of new lymphatic vessels. Our results indicate that innate immune cells (CD11b+ macrophages, but not CD11c+ dendritic cells) physically contributed to lymphangiogenesis under pathological conditions and that bone marrow-derived CD11b+ macrophages expressed lymphatic endothelial markers such as LYVE-1 and Prox-1 under inflamed conditions in the corneal stromata of mice. Furthermore, blood vascular endothelial cells that expressed the Tie2 promoter did not contribute to newly formed lymphatic vessels under inflamed conditions. Our in vitro experiments demonstrated that CD11b+ macrophages alone were capable of forming tube-like structures that expressed markers of lymphatic endothelium such as LYVE-1 and podoplanin. The novel finding that CD11b+ macrophages are critical for the development of inflammation-dependent lymphangiogenesis in the eye suggests a new mechanism of lymphangiogenesis.

The crucial role of macrophages in lymphangiogenesis

Lymphangiogenesis is associated with pathological processes such as the metastatic spread of carcinoma cells and organization of immunologically active lymphocytic infiltrates following organ transplantation. It has not yet been established whether expansion of the lymphatic vascular meshwork is driven by incorporation of progenitor cells or by local endothelial cell division. In this issue of the JCI, Maruyama et al. provide evidence that after mouse corneal transplant, CD11b+ macrophages infiltrate the corneal stroma and transdifferentiate into lymphatic endothelial cell clusters that join existing lymphatic vessels. In complementary in vitro experiments, murine peritoneal macrophages expressed lymphatic endothelial markers and formed vessel-like protrusions. These findings add yet another facet to the plasticity of macrophages, which are already known to transform from naive monocytes into VEGF-C-producing cells. Thus, macrophages support lymphangiogenesis in 2 different ways, either by transdifferentiating and directly incorporating into the endothelial layer or by stimulating division of preexistent local lymphatic endothelial cells.

Molecular lymphangiogenesis: new players

The function of the lymphatic vascular system as a conduit for immune cells and excess tissue fluid has been known for over a century, but the molecular players involved in lymphangiogenesis--the formation of lymphatic vessels--have remained unknown until recently. Signals mediated by vascular endothelial growth factor-C, the homeodomain transcription factor PROX1 and the forkhead transcription factor FOXC2 have been implicated in the growth, morphogenesis and hierarchic organization of the lymphatic vascular network. Recent results have also shown the importance of the angiopoietin-Tie and ephrin-Eph signaling systems in lymphangiogenesis, suggesting that these pathways regulate the lymphatic vascular system in a manner similar to, yet distinct from, their regulation of angiogenesis. This review provides an overview of the molecular players involved in lymphangiogenesis, with special emphasis on recently discovered molecular mechanisms.

VEGFR1-positive haematopoietic bone marrow progenitors initiate the pre-metastatic niche

The cellular and molecular mechanisms by which a tumour cell undergoes metastasis to a predetermined location are largely unknown. Here we demonstrate that bone marrow-derived haematopoietic progenitor cells that express vascular endothelial growth factor receptor 1 (VEGFR1; also known as Flt1) home to tumour-specific pre-metastatic sites and form cellular clusters before the arrival of tumour cells. Preventing VEGFR1 function using antibodies or by the removal of VEGFR1(+) cells from the bone marrow of wild-type mice abrogates the formation of these pre-metastatic clusters and prevents tumour metastasis, whereas reconstitution with selected Id3 (inhibitor of differentiation 3)-competent VEGFR1+ cells establishes cluster formation and tumour metastasis in Id3 knockout mice. We also show that VEGFR1+ cells express VLA-4 (also known as integrin alpha4beta1), and that tumour-specific growth factors upregulate fibronectin--a VLA-4 ligand--in resident fibroblasts, providing a permissive niche for incoming tumour cells. Conditioned media obtained from distinct tumour types with unique patterns of metastatic spread redirected fibronectin expression and cluster formation, thereby transforming the metastatic profile. These findings demonstrate a requirement for VEGFR1+ haematopoietic progenitors in the regulation of metastasis, and suggest that expression patterns of fibronectin and VEGFR1+VLA-4+ clusters dictate organ-specific tumour spread.

Signal transduction by VEGF receptors in regulation of angiogenesis and lymphangiogenesis

The VEGF/VPF (vascular endothelial growth factor/vascular permeability factor) ligands and receptors are crucial regulators of vasculogenesis, angiogenesis, lymphangiogenesis and vascular permeability in vertebrates. VEGF-A, the prototype VEGF ligand, binds and activates two tyrosine kinase receptors: VEGFR1 (Flt-1) and VEGFR2 (KDR/Flk-1). VEGFR1, which occurs in transmembrane and soluble forms, negatively regulates vasculogenesis and angiogenesis during early embryogenesis, but it also acts as a positive regulator of angiogenesis and inflammatory responses, playing a role in several human diseases such as rheumatoid arthritis and cancer. The soluble VEGFR1 is overexpressed in placenta in preeclampsia patients. VEGFR2 has critical functions in physiological and pathological angiogenesis through distinct signal transduction pathways regulating proliferation and migration of endothelial cells. VEGFR3, a receptor for the lymphatic growth factors VEGF-C and VEGF-D, but not for VEGF-A, regulates vascular and lymphatic endothelial cell function during embryogenesis. Loss-of-function variants of VEGFR3 have been identified in lymphedema. Formation of tumor lymphatics may be stimulated by tumor-produced VEGF-C, allowing increased spread of tumor metastases through the lymphatics. Mapping the signaling system of these important receptors may provide the knowledge necessary to suppress specific signaling pathways in major human diseases.

Serum vascular endothelial growth factor C (VEGF-C) as a specific biomarker for advanced cervical cancer: Relationship to insulin-like growth factor II (IGF-II), IGF binding protein 3 (IGF-BP3) and VEGF-A [corrected]

OBJECTIVES

An early non-invasive diagnosis of cervical cancer and its metastasis can save lives. We have shown that serum IGF-II levels can be effectively used for a specific early diagnosis of cervical cancer. Here, we shall determine if serum levels of vascular endothelial growth factors B and C (VEGF-A [corrected] VEGF-C) associated with vasculogenic and lymphogenic metastasis may be used for an early diagnosis of advanced metastatic cervical cancer and compare these levels with those of the serum IGF-II and IGF-binding protein 3 (IGF-BP3).

MATERIAL AND METHODS

(a) Serum levels of IGF-II, IGF-BP3, VEGF-A [corrected] (VEGF(165)) and VEGF-C (ELISA kits) were determined in: 82 controls with normal Pap smears; 29 women with atypical squamous cells of undetermined significance (ASCUS) and normal cervical biopsy; 46 ASCUS and cervical intraepithelial neoplasia (CIN) on biopsy; 8 pre-therapy CIN-I; 23 successfully treated CIN-I; 75 persistent CIN-I; 14 CIN-II/III pre-therapy; 14 successfully treated CIN-II/III; 70 persistent CIN-II/III; 86 pre-therapy cervical cancer; 26 in early grades of cervical cancer; 21 in late grades of cervical cancer; 22 cervical cancer patients in remission; 50 persistent cervical cancer; 18 with ovarian cancer; and 57 with endometrial cancer. (b) Serial serum samples collected over 5 years in 5 women with progressing cervical cancer were also tested. (c) Serum and tissue VEGF-C were enumerated in 20 matched serum (ELISA) and tissue (semi-quantitative immunofluorescent antibody assay) samples from controls, early cervical cancer, late cervical cancer, ovarian cancer and endometrial cancer patients. Student's t test, chi-square analysis and linear regression analysis were used.

RESULTS

(a) As anticipated, serum IGF-II levels were elevated as early as ASCUS with CIN on biopsy and continued to be elevated in CIN (all grades; pre-therapy and persistent) and cervical cancer (pre-therapy, early, late and persistent). Serum IGF-II levels were normal in ASCUS with normal biopsy, successfully treated CIN-I, II/III, cervical cancer as well as pre-therapy ovarian and endometrial cancers (therapy efficacy: P < 0.0001 by chi-square analysis). Serum IGF-BP3 showed a significant decrease with advancing disease. Serum VEGF-A [corrected] levels were the highest in pre-therapy, early, advanced and persistent cervical cancer, as well as in ovarian and endometrial cancers. Serum VEGF-C levels, on the other hand, were the highest in late and persistent cervical cancers, but not in ovarian or endometrial cancers. (b) In the 5 women with serial samples, the serum levels of the growth factors showed similar trends. (c) VEGF-C levels in serum and tissue were elevated in cervical cancers especially in advanced grades, while they were normal in serum and tissue from the controls and women with ovarian and endometrial cancers. There was a highly significant positive correlation between VEGF-C and IGF-II and a negative correlation between IGF-BP3 and VEGF-C (P < 0.0001).

CONCLUSION

Serum IGF-II up-regulation is specific to cervical cancer and helps in the early diagnosis of malignant proliferation, while serum VEGF-C up-regulation appears to be a unique marker for an early diagnosis of cervical cancer metastasis. VEGF-C and IGF-II systems appear to be interrelated in cervical cancer, contributing to the early malignant cell proliferation and lympho-vascular metastasis. Serum IGF-BP3 and VEGF-A [corrected] appear to be common markers for all gynecological cancers.

Tumor-Secreted Vascular Endothelial Growth Factor-C Is Necessary for Prostate Cancer Lymphangiogenesis, but Lymphangiogenesis Is Unnecessary for Lymph Node Metastasis

Dissemination to draining lymph nodes is a frequent first step in prostate cancer metastasis. Although tumors metastasize to lymph nodes via the lymphatics, the importance of lymphangiogenesis in mediating the process remains controversial. Here, we inhibit intratumoral lymphangiogenesis in s.c. and surgical orthotopic implantation mouse models of human prostate cancer using several strategies. Stable expression of small interfering RNAs (siRNA) targeted against human vascular endothelial growth factor-C (VEGF-C) in PC-3 cells reduced intratumoral lymphatics by 99% in s.c. tumors, indicating that tumor-secreted VEGF-C is necessary for lymphangiogenesis. Expression of siRNAs against human VEGF-A somewhat reduced tumor lymphangiogenesis. Secretion of a soluble VEGF receptor-3/Flt4 fusion protein by PC-3 cells reduced intratumoral lymphatics by 100% in s.c. tumors. Combination of soluble Flt4 and VEGF-C siRNA yielded >92% reduction of intratumoral lymphatics in orthotopic prostate tumors. However, metastasis to lymph nodes was not significantly affected regardless of intratumoral lymphatic vessel density. The abundance of marginal lymphatics at the tumor-stromal interface was unchanged in orthotopic tumors whose intratumoral lymphatics were inhibited, suggesting that these marginal vessels could be sufficient for lymph node metastasis. Hematogenous metastasis (blood tumor burden, lung metastasis) correlated with degree of lymph node invasion. We also analyzed the lymphatics in spontaneous transgenic adenocarcinomas of the mouse prostate which metastasize to lymph nodes. Progression from well-differentiated prostate intraepithelial neoplasia to metastatic, undifferentiated adenocarcinoma was accompanied by loss of lymphatics. These results suggest that tumor-secreted VEGF-C and, to a lesser extent, VEGF-A, are important for inducing prostate cancer intratumoral lymphangiogenesis but are unnecessary for lymph node metastasis.

Lymphatic vessel density and lymph node metastasis in prostate cancer

BACKGROUND

Few data are available examining the significance of prostatic lymphatic vessel density (LVD) to lymph node metastasis in patients with prostate cancer. The purpose of this study was to determine the distribution of lymphatic vessels in non-carcinomatous prostate tissue, and investigate the relationship between LVD and lymph node status in prostate cancer.

METHODS

LVD, identified by D2-40 immunostaining, was evaluated in non-carcinomatous prostates (n = 7) and prostate cancer (n = 37). The staining pattern of D2-40 was compared with that of another lymphatic vessel marker, vascular endothelial growth factor (VEGF) receptor-3, and a blood vessel endothelial marker, CD34, in adjacent sections.

RESULTS

The D2-40 antigen, podoplanin, was expressed exclusively in lymphatic vessels within tumor and normal tissue in all specimens. There was no overlap between cell staining for D2-40 and CD34. Peritumoral LVD and peritumoral lymphatic invasion were significantly associated with lymph node metastasis. VEGF receptor-3 was expressed in a subset of D2-40+ lymphatic vessels.

CONCLUSIONS

We have demonstrated that peritumoral lymphatic vessels are likely to serve as major conduits for nodal metastasis in prostate cancer using D2-40 to decorate lymphatic endothelium marker podoplanin. Lack of coexpression of podoplanin and VEGF receptor-3 in some lymphatic vessels suggests the heterogeneity of lymphatic endothelial cells in prostate tissue.

Lymphangiogenesis in human gynaecological cancers

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 for a long time suggested that by providing a pathway for tumor cell dissemination, tumor-associated lymphatics act as key components of metastatic spread. This is believed to occur principally via pre-existing and possibly also newly formed lymphatics (lymphangiogenesis). Increased expression of vascular endothelial growth factor-C (VEGF-C) and VEGF-D in primary tumors correlates with increased dissemination of tumor cells to regional lymph nodes (LNs) in a variety of human carcinomas. Here we will review the mechanisms of lymphangiogenesis, particularly in the context of metastatic tumor spread, and will critically examine the role of VEGF-C and VEGF-D in this process in gynaecological cancers. Potential anti-lymphangiogenic strategies are also discussed.

Polymorphisms in inflammation genes and bladder cancer: from initiation to recurrence, progression, and survival

PURPOSE

Since chronic inflammation contributes to tumorigenesis, we hypothesized that the risk and clinical outcome of bladder cancer (BC) might be modulated by genetic variations in inflammation genes.

METHODS

Using the TaqMan method, we genotyped single nucleotide polymorphisms in interleukin (IL) -6 (-174 G-->C), IL-8 (-251 T-->A), tumor necrosis factor-alpha (TNF-alpha; -308 G-->A), and peroxisome proliferator-activated receptor gamma (PPARG; Pro12Ala), and determined their associations with BC initiation and clinical outcome.

RESULTS

We found that the IL-6 variant genotype (C/C) was associated with an increased BC risk (OR, 1.77; 95% CI, 1.25 to 2.51). There were joint effects between the variant IL-6 genotypes and smoking status, and between the variant genotypes of IL-6 and other genes. To assess effect on recurrence, we grouped non-muscle-invasive BC patients according to intravesical Bacillus Calmette-Guerin (BCG) treatment status: no BCG, induction BCG (iBCG), and maintenance BCG (mBCG). In the Cox proportional hazards model, the variant IL-6 genotype was associated with an increased recurrence risk (hazard ratio [HR], 4.60; 95% CI, 1.24 to 17.09) in patients receiving mBCG. The variant PPARG genotype was associated with a reduced recurrence risk (HR, 0.41; 95% CI, 0.20 to 0.86) among untreated patients. In patients with non-muscle-invasive BC, the variant IL-6 genotype was associated with an increased progression risk (HR, 1.88; 95% CI, 0.80 to 4.11). In patients with invasive BC, variant IL-6 was associated with improved 5-year overall and disease-specific survival (HR, 0.43; 95% CI, 0.19 to 0.94 and HR, 0.39; 95% CI, 0.15 to 1.00, respectively).

CONCLUSION

Inflammation gene polymorphisms are associated with modified BC risk, treatment response, and survival.

Tumor lymphangiogenesis predicts melanoma metastasis to sentinel lymph nodes

Cutaneous melanoma is a common melanocytic neoplasm that can quickly metastasize to regional lymph nodes. Currently, prognosis is determined by measuring tumor thickness but more reliable markers for metastatic spread are urgently needed. We investigated whether the extent of tumor lymphangiogenesis can predict melanoma metastasis to sentinel lymph nodes. We quantified the extent of tumor lymphangiogenesis, as well as other factors, in excised primary tumors and in sentinel lymph node biopsy samples from 45 patients with primary cutaneous melanoma. The results were correlated with histological and clinical outcome. Primary melanomas from patients whose tumors had metastasized to the sentinel lymph nodes contained prominent 'hot spots' of increased lymphatic vessel density, compared to nonmetastatic tumors. Multivariate risk analysis revealed that the lymphatic vascular area of primary melanomas, an index of tumor lymphangiogenesis, was the most sensitive prognostic marker for sentinel lymph node metastasis, and was even able to more accurately predict which tumors were metastatic to sentinel lymph nodes than the currently used method of measuring tumor thickness. Highly lymphangiogenic melanomas maintained their lymphangiogenic activity after metastasis to the sentinel lymph node. The extent of tumor lymphangiogenesis is a highly sensitive (83%) and specific (89%) prognostic marker of lymph node metastasis. Assessment of lymphangiogenesis in primary melanomas may be a more effective approach than the currently used technique of measuring tumor thickness in selecting patients with early metastatic disease for aggressive therapy.

Opinion: emerging mechanisms of tumour lymphangiogenesis and lymphatic metastasis

Malignant tumours can spread to lymph nodes through lymphatic vessels. Recent studies show that tumours produce a range of growth factors that directly or indirectly stimulate lymphatic vessel growth (lymphangiogenesis) and lymphatic metastasis. These findings indicate that tumour lymphangiogenesis, similar to haemangiogenesis, is a complex process that is regulated by multiple growth factors. Understanding the underlying mechanisms by which tumours induce lymphangiogenesis might provide important information for the therapeutic intervention of metastatic spread.

Spontaneous corneal hem- and lymphangiogenesis in mice with destrin-mutation depend on VEGFR3 signaling

Lymphangiogenesis, the formation of new lymphatic vessels, is important for tumor metastasis and induction of immunity to peripheral antigens including organ transplants. We herein describe a novel mouse model of spontaneous, secondary lymphangiogenesis in the normally avascular cornea. corn1 mice, which suffer from a deletion in the gene encoding the cytoskeletal protein destrin, develop hemangiogenesis as well as spontaneous outgrowth of LYVE-1+++/CD31+ lymphatic vessels into the cornea starting at age 4 weeks. Corneal lymphangiogenesis is delayed in onset, is less intense, and regresses earlier compared with hemangiogenesis. Moreover, the lymphangiogenesis is preceded only by a mild recruitment of CD45+ inflammatory cells into the cornea. In contrast to mice with inflammation-induced hem- and lymphangiogenesis, corn1 mice do not develop breakdown of the blood-aqueous barrier. Finally, in this novel mouse model, a blocking anti-VEGFR3 antibody significantly inhibited not only lymph- but also hemangiogenesis. In summary, destrin deletion has differential effects on spontaneous hem- and lymphangiogenesis in the normally avascular cornea and represents a novel mouse model to study the mechanisms of lymphangiogenesis and to test the antihem- and antilymphangiogenic properties of known or new antiangiogenic agents.

Soluble mediators of inflammation during tumor development

Tissues maintain homeostasis by monitoring and responding to varied physical interactions between cells and their microenvironment. In situations where acute tissue damage occurs, such as wounding, pathogenic assault, or toxic exposure, regulatory circuits that monitor tissue homeostasis are rapidly engaged to initiate tissue repair by regulating cell polarity, proliferation and death, matrix metabolism, inflammation, and vascular and lymphatic function. The critical feature of regulating these acute responses is the innate ability to discriminate between homeostatic versus damaged tissue states and engage or disengage regulatory machinery as appropriate; thus, a major distinction between acute versus chronic disease is the altered ability to appropriately activate and?or inactivate reparative regulatory programs. Since cancer is a chronic disease characterized by altered cell polarity, enhanced cell survival, inflammation, increased matrix metabolism, and enhanced vascular and lymphatic function, considerable attention is now focused on understanding the cellular and molecular mechanisms regulating these responsive pathways. Since chemoattractant cytokines are important mediators of leukocyte recruitment following acute tissue stress, and demonstrate altered characteristics of expression and activation in chronically inflamed tissue, they have been implicated as key regulators of inflammation and angiogenesis during cancer development. This chapter focuses on the clinical and experimental data implicating proinflammatory cytokines and chemokines as important potentiators of carcinogenesis.

Prognostic value of lymphatic and blood vessel invasion in neuroendocrine tumors of the lung

Few data on the influence of vessel invasion on the progression of neuroendocrine lung tumors are available. Because of the lack of specific markers, previous studies could not reliably discriminate lymphatic and blood vessels. By immunostaining for podoplanin, specific for lymphatic endothelium, and CD34 antigen, we assessed lymphatic and blood vessel invasion in 120 tissue specimens of patients with neuroendocrine lung tumors. Lymphovascular invasion was correlated with clinicopathologic parameters, and its prognostic relevance was evaluated. Lymphatic vessels were identified exclusively at the tumor invasion front, whereas blood capillaries were also seen within tumors. Lymphatic vessel as well as lymphatic and blood vessel invasion was prevalent in patients with high-grade neuroendocrine tumors and advanced tumor stages, closely associated with lymph node metastases (P < 0.0001). In univariate analysis, these two invasion types correlated with decreased disease-free survival (both P < 0.0001), whereas blood vessel invasion alone did not. In multivariate analysis, only tumor grade and lymph node status remained statistically significant factors for prognosis (P = 0.016 and P < 0.0001). Our results suggest that evaluation of lymphatic vessel invasion is important in neuroendocrine lung tumors serving as a prognostic parameter for disease-free survival.