The role of tumor lymphangiogenesis in metastatic spread

[The expressions of IL-7 and IL-7R and the relationship between them with lymph node metastasis and prognosis in non-small cell lung cancer]

背景与目的

已有的研究表明淋巴转移与肺癌的预后密切相关，白介素-7（interleukin-7, IL-7）和IL-7受体（interleukin-7 receptor, IL-7R）可以通过血管内皮生长因子-D（vascular endothelial growth factor-D, VEGF-D）促进淋巴转移。本研究旨在探讨IL-7和IL-7R在非小细胞肺癌（non-small cell lung cancer, NSCLC）中的表达情况，分析它们与各临床病理因素、VEGF-D及预后之间的关系。

方法

免疫组化方法检测95例原发性NSCLC组织标本中IL-7和IL- 7R的表达情况，分析它们与各临床病理因素、VEGF-D及预后之间的关系。

结果

95例原发性NSCLC组织中IL-7、IL-7R和VEGF-D高表达者分别占63.16%、61.05%和58.95%，IL-7和IL-7R的表达与临床分期和淋巴结转移均密切相关，而与患者的年龄、性别、组织分型、分化程度无明显关系；IL-7和IL-7R与VEGF-D高表达组的淋巴管密度（lymphatic vessel density, LVD）明显高于低表达或无表达组的LVD，差异具有统计学意义（P=0.003，P=0.019和P < 0.001）；生存分析显示IL-7和IL-7R与VEGF-D高表达组的预后较差。

结论

在NSCLC中IL-7/IL-7R高表达与分期、淋巴结转移、VEGF-D、LVD和预后不良呈正相关。

Invasive ductal carcinomas of the breast showing partial reversed cell polarity are associated with lymphatic tumor spread and may represent part of a spectrum of invasive micropapillary carcinoma

Invasive micropapillary carcinomas (IMPC) of the breast are aggressive tumors frequently associated with lymphatic invasion and nodal metastasis even when micropapillary (MP) differentiation is very focal within the tumors. We have noticed that some breast carcinomas showing lymphatic spread but lacking histologic features of IMPC have occasional tumor cell clusters reminiscent of those of IMPC without the characteristic prominent retraction artifact. To study the clinicopathologic significance of such features, we prospectively selected 1323 invasive ductal carcinomas and determined the presence and extent of MP differentiation and retraction artifact in the tumors. One representative tumor block per case was used for immunostaining for epithelial membrane antigen (EMA). Partial reverse cell polarity (PRCP) was defined as prominent linear EMA reactivity on at least part of the periphery of tumor cell clusters usually associated with decreased cytoplasmic staining. The clinicopathologic features of carcinomas with PRCP were compared with IMPC and invasive ductal (no special type) carcinomas without this feature. Of the 1323 cases, 96 (7.3%) and 92 (7.0%) showed MP features and the presence of PRCP, respectively. We found that the presence of both PRCP and MP features were strongly associated with decreased cytoplasmic EMA immunoreactivity and the presence of lymphatic invasion and nodal metastasis, even if such features were present only very focally. Our results suggest that breast carcinomas with PRCP may have the same implication as MP differentiation and these tumors may represent part of a spectrum of IMPC. Complete or partial reversal of cell polarity may play a significant role in lymphatic tumor spread.

CXCR4 signaling regulates metastasis of chemoresistant melanoma cells by a lymphatic metastatic niche

Highly metastatic and chemotherapy-resistant properties of malignant melanomas stand as challenging barriers to successful treatment; yet, the mechanisms responsible for their aggressive characteristics are not fully defined. We show that a distinct population expressing CD133 (Prominin-1), which is highly enriched after administration of a chemotherapeutic drug, dacarbazine, has enhanced metastatic potential in vivo. CD133(+) tumor cells are located close to tumor-associated lymphatic vessels in metastatic organs such as the regional lymph nodes and lung. Lymphatic endothelial cells promote the migratory activity of a CD133(+) subset to target organs and regulation of lymphatic growth efficiently modulates the metastasis of CD133(+) tumor cells. We found that lymphatic vessels in metastatic tissues stimulate chemokine receptor 4 (CXCR4)(+)/CD133(+) cell metastasis to target organs by secretion of stromal cell-derived factor-1 (SDF-1). The CXCR4(+)/CD133(+) cells exhibited higher metastatic activity compared with CXCR4(-)/CD133(+) cells and, importantly, blockade of CXCR4 coupled with dacarbazine efficiently inhibited both tumor growth and metastasis; dacarbazine alone could not attenuate tumor metastasis. The current study demonstrates a previously unidentified role of the lymphatic microenvironment in facilitating metastasis of chemoresistant melanoma cells via a specific chemotactic axis, SDF-1/CXCR4. Our findings suggest that targeting the SDF-1/CXCR4 axis in addition to dacarbazine treatment could therapeutically block chemoresistant CD133(+) cell metastasis toward a lymphatic metastatic niche.

Lymphatic vessel density as a prognostic marker in clinical stage I endocervical adenocarcinoma

There are limited data evaluating the significance of lymphatic vessel density (LVD) as a prognostic marker in cervical adenocarcinoma. In this study, we investigated intratumoral and peritumoral LVD, using the lymphatic marker D2-40, as a prognostic marker in endocervical adenocarcinoma. Surgical specimens from 50 consecutive patients with endocervical adenocarcinoma treated with complete staging surgical procedures were reviewed. Selected tumor blocks were immunostained for D2-40 and CD31. Positively stained microvessels (MVs) were counted in densely vascular/lymphatic foci (hot spots) at 400x field in each specimen (0.17 mm). Results were expressed as the highest MV count identified within any single field. Both intratumoral CD31 MV and peritumoral D2-40 LVD showed significant correlation with depth of invasion (r=0.39, 0.37, respectively), percentage of circumferential involvement (r=0.36, 0.48, respectively), and lymphovascular invasion detected by D2-40 (r=0.45, 0.51, respectively; P<0.01). Only peritumoral D2-40 LVD showed a significant correlation with lymph node metastases (r=0.40; P<0.01), disease-free and overall survivals. Using univariate analysis, peritumoral D2-40 LVD showed significant correlation with lymphovascular invasion detected by D20-40 and lymph node metastases (P<0.05), which was maintained on multivariate analysis. D2-40 detected lymphovascular invasion in 16 of 50 (32%) cases, and showed a significant correlation with depth of invasion, lymph node metastases, involvement of parametrium (r=0.41, 0.38, 0.32, respectively; P<0.01), and disease-free survival. Our study showed that both angiogenesis and lymphangiogenesis play an important role in the progression of endocervical adenocarcinoma, and that peritumoral D2-40 LVD is an independent predictor of lymph node metastasis.

Role of the vascular endothelial growth factor signaling pathway in tumor growth and angiogenesis

New blood vessel formation (angiogenesis) is a fundamental event in the process of tumor growth and metastatic dissemination. Hence, the molecular basis of tumor angiogenesis has been of keen interest in the field of cancer research. The vascular endothelial growth factor (VEGF) signaling pathway is well established as one of the key regulators of this process. The VEGF/VEGF-receptor axis is composed of multiple ligands and receptors with overlapping and distinct ligand-receptor binding specificities, cell-type expression, and function. Activation of the VEGF signaling pathway triggers a network of signaling processes that promote endothelial cell growth, migration, and survival from pre-existing vasculature. In addition, VEGF-mediated vessel permeability has been associated with malignant effusions. More recently, an important role of VEGF has emerged in mobilization of endothelial progenitor cells from the bone marrow to distant site neovascularization. The well-established role of VEGF in promoting tumor angiogenesis and the pathogenesis of human cancers has led to the rational design and development of reagents that selectively target this pathway. Studies with various anti-VEGF/VEGFR therapies have shown that these reagents can potently inhibit angiogenesis and tumor growth in preclinical models.

Invasive micropapillary variant of the gallbladder adenocarcinoma and its aggressive potential for lymph node metastasis

An invasive micropapillary variant (IMPV) has recently been described in several organs but has not been reported in the gallbladder. It has been mentioned to have aggressive behavior with a high propensity for lymphovascular invasion, lymph node metastasis and poor clinical outcome. We analyzed the clinicopathologic findings of IMPV and compared them with those of a conventional adenocarcinoma in the gallbladder to clarify the highly aggressive potential of IMPV of gallbladder carcinoma. Ninety consecutive cases of surgically resected gallbladder carcinomas were studied for age, gender, type, depth of invasion and lymph node and distant metastases. Histologically, IMPV of gallbladder carcinoma was characterized by a small cluster of tumor cells lying within clear stromal spaces. This pattern mimicked extensive lymphatic invasion, but the cluster of tumor cells showed a distinctive retraction artifact from the surrounding stroma. In total, 20 (22.2%) cases had foci of IMPV, which ranged from 5% to 10% of the primary tumor tissue. Of those 20 cases, 17 (85.0%) carcinomas with IMPV also included lymph node metastasis, which was more frequent than in conventional carcinoma (32.8%, P < 0.001). Carcinomas with IMPV had a more advanced tumor status and showed severe lymphatic invasion (P = 0.001, P < 0.001, respectively). A multivariate regression analysis demonstrated that the presence of IMPV is an independent predictor of regional nodal metastasis (Odds ratio: 9.995, 95% confidence interval: 1.996-50.052, P = 0.005). IMPV is a useful predictor of regional lymph node metastasis in gallbladder adenocarcinoma.

Vimentin expression of esophageal squamous cell carcinoma and its aggressive potential for lymph node metastasis

Esophageal squamous cell carcinoma (ESCC) has been generally considered as one of the most aggressive cancers with poor prognosis. Vimentin is the major protein constituent of intermediate filaments in normal and neoplastic mesenchymal cells, and has been regarded as a marker of epithelial-mesenchymal transition (EMT). However, little is known about ESCC with vimentin expression as a marker of EMT. In this study, we analyzed vimentin expression in 129 cases of ESCC in order to elucidate whether vimentin expression is correlated with clinicopathological features and aggressive behavior of ESCC. Vimentin expression was identified in 96 of the 129 cases (74.4%). The cases with vimentin-positive carcinoma cells showed a significantly higher incidence of lymph node metastasis (P = 0.001). Carcinomas with vimentin expression were more advanced in terms of tumor status and lymphatic invasion (P = 0.001, P = 0.009, respectively), and associated with stronger stromal alpha-smooth muscle actin (alpha-SMA) expression (P < 0.001). Vimentin expression was also associated with distant metastasis, including distant node metastasis (P = 0.014). Vimentin expression in both primary and metastatic carcinomas was found in 68.6% (48/70) of the cases, while no vimentin expression in both primary and metastatic carcinomas comprised 92.3% of the cases (12/13) (P < 0.001). In conclusion, we demonstrated that vimentin expression in ESCC is an independent predictor of lymph node metastasis (multivariate analysis, P = 0.014, odds ratio: 3.314, 95% confidence interval: 1.276-8.605). In addition, vimentin expression was frequently retained in metastatic carcinoma of the lymph node.

Mechanism of lymph node metastasis in prostate cancer

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

Phage-derived fully human monoclonal antibody fragments to human vascular endothelial growth factor-C block its interaction with VEGF receptor-2 and 3

Vascular endothelial growth factor C (VEGF-C) is a key mediator of lymphangiogenesis, acting via its receptors VEGF-R2 and VEGF-R3. High expression of VEGF-C in tumors correlates with increased lymphatic vessel density, lymphatic vessel invasion, sentinel lymph node metastasis and poor prognosis. Recently, we found that in a chemically induced skin carcinoma model, increased VEGF-C drainage from the tumor enhanced lymphangiogenesis in the sentinel lymph node and facilitated metastatic spread of cancer cells via the lymphatics. Hence, interference with the VEGF-C/VEGF-R3 axis holds promise to block metastatic spread, as recently shown by use of a neutralizing anti-VEGF-R3 antibody and a soluble VEGF-R3 (VEGF-C/D trap). By antibody phage-display, we have developed a human monoclonal antibody fragment (single-chain Fragment variable, scFv) that binds with high specificity and affinity to the fully processed mature form of human VEGF-C. The scFv binds to an epitope on VEGF-C that is important for receptor binding, since binding of the scFv to VEGF-C dose-dependently inhibits the binding of VEGF-C to VEGF-R2 and VEGF-R3 as shown by BIAcore and ELISA analyses. Interestingly, the variable heavy domain (V_H) of the anti-VEGF-C scFv, which contains a mutation typical for camelid heavy chain-only antibodies, is sufficient for binding VEGF-C. This reduced the size of the potentially VEGF-C-blocking antibody fragment to only 14.6 kDa. Anti-VEGF-C V_H-based immunoproteins hold promise to block the lymphangiogenic activity of VEGF-C, which would present a significant advance in inhibiting lymphatic-based metastatic spread of certain cancer types.

Nerve growth factor-beta expression is associated with lymph node metastasis and nerve infiltration in human hilar cholangiocarcinoma

BACKGROUND

Angiogenesis and lymphangiogenesis are important processes in the progression of malignant tumors. Previous studies have shown that nerve growth factor-beta (NGF-beta) can promote the initiation and progression of many tumors. In addition, vascular endothelial growth factor-C (VEGF-C) has become recognized as the most important lymphangiogenic factor. In the present study, the expression of NGF-beta in human hilar cholangiocarcinoma and its relationship with lymphangiogenesis, lymph node metastasis, nerve infiltration, and VEGF-C expression was investigated.

METHODS

Nerve growth factor-beta and VEGF-C expression were investigated by immunohistochemistry in samples from 28 cases of hilar cholangiocarcinoma. The lymphatic vessel density (LVD) in the tumor tissue that indicated lymphangiogenesis were calculated by immunostaining with the lymphendothelial-specific antibody D2-40. The relationship between NGF-beta expression and VEGF-C expression, lymphangiogenesis, lymph node metastasis, and nerve infiltration was evaluated.

RESULTS

The overexpression of NGF-beta and VEGF-C occurred in 57.1% (16/28) and 46.4% (13/28) of tumor samples, respectively. Nerve growth factor-beta overexpression was highly correlated with VEGF-C overexpression (P = 0.005), LVD (P < 0.001), lymph node metastasis (P = 0.021), nerve infiltration (P = 0.019), and tumor stage (P = 0.040). Furthermore, VEGF-C overexpression was highly correlated with LVD (P < 0.001) and lymph node metastasis (P < 0.001). However, there was no statistic significance in the relation between NGF-beta expression and sex (P = 0.185), age (P = 0.387), maximal tumor size (P = 0.736), Bismuth classification (P = 0.627) as well as histological grade (P = 0.203).

CONCLUSIONS

Nerve growth factor-beta might promote lymph node metastasis and nerve infiltration in human hilar cholangiocarcinoma.

Immunohistochemical expression of epidermal growth factor receptor (EGFR) in oral squamous cell carcinoma in relation to proliferation, apoptosis, angiogenesis and lymphangiogenesis

OBJECTIVES

Squamous cell carcinoma (SCC) is by far the most common malignant neoplasm of the oral cavity. A number of etiologic factors have been implicated in its development. During the past few decades, a particular focus has been placed on the investigation of valid biomarkers predictive of cancer behavior and cervical lymph node metastasis in head and neck Squamous cell carcinoma (HNSCC).The present study was designed to investigate the expression of epidermal growth factor in these tumors in relation to proliferation, apoptosis, angiogenesis and lymphangiogenesis.

MATERIALS AND METHODS

Immunohistochemical (IHC) evaluation of epidermal growth factor receptor (EGFR) expression in 40 retrospective OSCC specimens and its correlation with proliferating cell nuclear antigen (PCNA), antiapoptotic antibody (P53), vascular endothelial growth factor (VEGF), and D2-40 monoclonal antibodies (Mab), in relation to the clinicopathological parameters.

RESULTS

Data revealed positive EGFR immunoreactivity in 35(87.5%) cases. There was a statistically significant correlation regarding EGFR extent score with respect to intratumoral lymphatic vessel density (ILVD) (r = 0.35) as well as EGFR intensity score with respect to ILVD and peritumoral lymphatic vessel density (PLVD) (r = 0.33, r = 0.36 respectively). EGFR expression was not correlated with the clinicopathological parameters.

CONCLUSIONS

EGFR is expressed by most of the cases. EGFR correlation with D2- 40 positive lymphatic vessels suggests a higher tendency of OSCC for lymphatic dissemination. Lack of correlation among the studied markers suggests their independent effect on tumor behavior.

Pigment epithelium-derived factor stimulates tumor macrophage recruitment and is downregulated by the prostate tumor microenvironment

Pigment epithelium-derived factor (PEDF) is a potent inhibitor of angiogenesis but whether it has additional effects on the tumor microenvironment is largely unexplored. We show that overexpression of PEDF in orthotopic MatLyLu rat prostate tumors increased tumor macrophage recruitment. The fraction of macrophages expressing inducible nitric oxide synthase, a marker of cytotoxic M1 macrophages, was increased, suggesting that PEDF could enhance antitumor immunity. In addition, PEDF overexpression reduced vascular growth both in the tumor and in the surrounding normal tissue, slowed tumor growth, and decreased lymph node metastasis. Contrary, extratumoral lymphangiogenesis was increased. PEDF expression is, for reasons unknown, often decreased or lost during prostate tumor progression. When AT-1 rat prostate tumor cells, expressing high levels of PEDF messenger RNA (mRNA) and protein, were injected into the prostate, PEDF is markedly downregulated, suggesting that factors in the microenvironment suppressed its expression. One such factor could be macrophage-derived tumor necrosis factor alpha (TNFalpha). A fraction of the accumulating macrophages expressed TNFalpha, and TNFalpha treatment downregulated the expression of PEDF protein and mRNA in prostate AT-1 tumor cells in vitro and in the rat ventral prostate in vivo. PEDF apparently has multiple effects in prostate tumors: it suppresses angiogenesis and metastasis, but it also causes macrophage accumulation. Accumulating macrophages may inhibit tumor growth, but they may also suppress PEDF and enhance lymph angiogenesis and, in this way, eventually enhance tumor growth.

Role of lymphangiogenesis in lung cancer

Lung cancer represents one of the most frequent causes of death due to neoplastic disease in Poland and around the world. The high mortality which accompany neoplastic diseases used to be ascribed mainly to dissemination of cancerous cells. Studies on animal models suggest that tumour lymphangiogenesis represents the principal factor in the process of metastases formation. Lymphangiogenesis involves a process of formation of new lymphatic vessels from already existing lymphatic capillaries. Lymphangiogenesis is stimulated by vascular endothelial growth factors (VEGF) and other, recently reported factors, such as, e.g., cyclooxygenase 2, fibroblast growth factor 2, angiopoetin-1 and the insulin-resembling growth factor. In lymphangiogenesis a key role is played by neutropilin 2 or podoplanin and this promoted development of studies on lymphangiogenesis. Activation of VEGF-C/VEGF-D/VEGFR-3 axis increases motility and invasiveness of neoplastic cells, promotes development of metastases in several types of tumours such as, e.g., lung cancer, mammary carcinoma, cancers of the neck, prostate and large intestine. In recent years lymphangiogenesis provided topic of many studies. A positive correlation was detected between expressions of VEGF-C/D and VEGFR-3 in non-small cell lung cancer. In patients with lung cancer with high expression of VEGF-C a markedly abbreviated survival was noted. Positive correlation was detected between expression of VEGF-C and VEGF-D on one hand and expression of LYVE-1 on the other in sentinel lymph nodes with metastases of neoplastic cells in patients with non-small cell lung cancer. Also, high density of lymphatic vessels and high density of intraneoplastic microvessels proved to be independent poor prognostic indices in patients with non-small cell lung cancer. Extensive hope is linked to studies on inhibitors of lymphangiogenesis, which may improve results of treatment also in tumour patients.

Involvement of lymphatics in lymphangioleiomyomatosis

Lymphangioleiomyomatosis (LAM), a rare multisystem disease, occurs primarily in women, with cystic destruction of the lungs, abdominal tumors, and involvement of the axial lymphatics in the thorax and abdomen. To understand the pathogenesis of LAM, we initiated a longitudinal study of patients with LAM; over 500 patients have been enrolled. LAM results from the proliferation of a neoplastic cell (LAM cell), which has mutations in the tuberous sclerosis complex (TSC) genes, TSC1 or TSC2. Consistent with their metastatic behavior, LAM cells were isolated from blood, urine, and chylous effusions. Surface proteins on LAM cells include those found on metastatic cells and those involved in cell migration. In the lung, LAM cells are found clustered in nodules, which appear in the walls of the cysts, and in the interstitium. LAM lung nodules are traversed by slit-like vascular structures, with lining cells showing reactivity with antibodies against components of lymphatic endothelial cells. The axial lymphatics appear to be infiltrated by LAM cells, which may result in obstruction and formation of chyle-filled lymphangioleiomyomas. LAM cell clusters have been isolated from chylous pleural effusions, and it is hypothesized that these clusters may be responsible for metastatic spread of LAM cells via lymphatic vessels. Consistent with a lymphangiogenic process, levels of VEGF-D, a lymphangiogenic factor, were higher in sera of patients with LAM and lymphatic involvement (i.e., lymphangioleiomyoma, adenopathy) than in healthy volunteers or LAM patients with cystic disease limited to the lung. These findings are consistent with an important function for lymphangiogenesis in LAM.

Serum VEGFR-3 and survival of advanced gastric cancer patients treated with FOLFOX

AIM: To explore if vascular endothelial growth factor receptor-3 (VEGFR-3) and carcinoembryonic antigen (CEA) can predict overall survival in advanced gastric cancer.

METHODS: VEGFR-3 level was assessed by enzyme-linked immunosorbent assay, and CEA was assessed by chemiluminescence immunoassay in the sera of 81 advanced gastric cancer patients before treatment with oxaliplatin plus 5-fluorouracil and folinic acid.

RESULTS: Median survival time in patients with a low serum VEGFR-3 level was significantly longer than in those with a higher VEGFR-3 level (15.4 mo vs 7.7 mo, P < 0.001). Patients with a low CEA level had a longer survival than those with a higher CEA level (15.8 mo vs 8.6 mo, P < 0.001). Thirty-nine patients with low VEGFR-3 and low CEA levels had a median survival of 19.7 mo (P = 0.0006). The hazard ratio for patients with a high VEGFR-3 level was 2.443 (P = 0.002).

CONCLUSION: High serum VEGFR-3 level is correlated significantly with poor survival. In patients with a high serum level of VEGFR-3, alternative chemotherapy regimens should be considered.

Netrin-4 induces lymphangiogenesis in vivo

Netrin-4, a laminin-related secreted protein is an axon guidance cue recently shown essential outside of the nervous system, regulating mammary and lung morphogenesis as well as blood vascular development. Here, we show that Netrin-4, at physiologic doses, induces proliferation, migration, adhesion, tube formation and survival of human lymphatic endothelial cells in vitro comparable to well-characterized lymphangiogenic factors fibroblast growth factor-2 (FGF-2), hepatocyte growth factor (HGF), vascular endothelial growth factor-A (VEGF-A), and vascular endothelial growth factor-C (VEGF-C). Netrin-4 stimulates phosphorylation of intracellular signaling components Akt, Erk and S6, and their specific inhibition antagonizes Netrin-4-induced proliferation. Although Netrin receptors Unc5B and neogenin, are expressed by human lymphatic endothelial cells, suppression of either or both does not suppress Netrin-4-promoted in vitro effects. In vivo, Netrin-4 induces growth of lymphatic and blood vessels in the skin of transgenic mice and in breast tumors. Its overexpression in human and mouse mammary carcinoma cancer cells leads to enhanced metastasis. Finally, Netrin-4 stimulates in vitro and in vivo lymphatic permeability by activating small GTPases and Src family kinases/FAK, and down-regulating tight junction proteins. Together, these data provide evidence that Netrin-4 is a lymphangiogenic factor contributing to tumor dissemination and represents a potential target to inhibit metastasis formation.

Intratumoral as well as peritumoral lymphatic vessel invasion correlates with lymph node metastasis and unfavourable outcome in colorectal cancer

The aim of this study was to assess the intratumoral and peritumoral distribution of lymphatic vessel density (LVD) and lymphatic vessel invasion (LVI) in colorectal cancer and their relationships with patients' clinicopathological characteristics and survival. Paraffin sections of 81 primary colorectal cancers were examined by immunohistochemical staining using monoclonal antibody D2-40. Peritumoral LVD was significantly higher than intratumoral LVD (P = 0.000). Both intratumoral LVD and peritumoral LVD were correlated with the presence of LVI (P = 0.006 and P = 0.003, respectively). LVI, intratumoral LVI and peritumoral LVI were identified, respectively in 38, 28 and 32% of the samples investigated. Both intratumoral LVI and peritumoral LVI were correlated with lymph node metastasis (P = 0.030 and P = 0.014, respectively). Lymph node metastasis, the presence of intratumoral LVI and peritumoral LVI were adversely associated with the 5-year overall survival in a univariate analysis (P = 0.001, P = 0.011 and P = 0.017, respectively). Multivariate analysis using Cox proportional hazard model showed that neither intratumoral LVI nor peritumoral LVI was an independent prognostic factor of overall survival. The results of this study demonstrated that intratumoral as well as peritumoral LVI was associated with lymph node metastasis and adverse outcome in colorectal cancer.

Hypoxic tumor cell modulates its microenvironment to enhance angiogenic and metastatic potential by secretion of proteins and exosomes

Under hypoxia, tumor cells produce a secretion that modulates their microenvironment to facilitate tumor angiogenesis and metastasis. Here, we observed that hypoxic or reoxygenated A431 carcinoma cells exhibited enhanced angiogenic and metastatic potential such as reduced cell-cell and cell-extracellular matrix adhesion, increased invasiveness, and production of a secretion with increased chorioallantoic membrane angiogenic activity. Consistent with these observations, quantitative proteomics revealed that under hypoxia the tumor cells secreted proteins involved in angiogenesis, focal adhesion, extracellular matrix-receptor interaction, and immune cell recruitment. Unexpectedly, the secreted proteins were predominantly cytoplasmic and membrane proteins. Ultracentrifugation at 100,000 x g precipitated 54% of the secreted proteins and enriched for many exosome-associated proteins such as the tetraspanins and Alix and also proteins with the potential to facilitate angiogenesis and metastasis. Two tetraspanins, CD9 and CD81, co-immunoprecipitated. Together, these data suggested that tumor cells secrete proteins and exosomes with the potential to modulate their microenvironment and facilitate angiogenesis and metastasis.

Role of intratumoral lymphatic vessels in the lymph node dissemination of laryngopharyngeal squamous cell carcinoma

BACKGROUND

The development of new markers for lymphatic endothelium allowed the study of intratumoral lymphatic microcirculation, as well as its association with lymph node metastasis.

METHODS

In all, 120 patients with laryngopharyngeal squamous cell carcinoma (LPSCC) without previous treatment were retrospectively studied. The immunohistochemical determination of PA2.26 antigen/podoplanin was used to assess intratumoral lymphatic vessels (ILVs) in the primary tumor.

RESULTS

Multivariate analysis revealed that lymph node metastasis was associated with tumor location (p = .001), differentiation grade (p = .02), and ILV (p = .013). Hypopharyngeal and supraglottic locations, poor grade of differentiation, and ILV, respectively, increased the risk of developing lymph node metastasis 13.5-, 4.7-, 5.2-, and 3.2-fold.

CONCLUSIONS

In our series, the presence of ILV in the primary tumor was an independent risk factor for the development of lymph node metastasis. The incorporation of ILV assessment into routine clinicopathological study might improve the evaluation of patients with LPSCC.

Effects of VEGFR-3 phosphorylation inhibitor on lymph node metastasis in an orthotopic diffuse-type gastric carcinoma model

BACKGROUND

Vascular endothelial growth factor receptor-3 (VEGFR-3) signalling mediates lymphangiogenesis and lymphatic invasion; however, the effect of VEGFR-3 inhibition on the lymph node (LN) metastasis remains unclear. The aim of this study is to clarify the benefit of a VEGFR-3 inhibitor Ki23057 for LN metastasis.

METHODS

Ki23057 was administered orally to gastric cancer models created by orthotopic inoculation of diffuse-type gastric cancer cells, OCUM-2MLN. The effects of Ki23057 on lymphatic vessel invasion, lymphatic vessel density, and VEGFR-3 phosphorylation were examined by immunostaining or immunoblotting.

RESULTS

Ki23057 inhibited the autophosphorylation of VEGFR-3, with IC50 values of 4.3 nM in the cell-free kinase assay. Murine gastric cancer models created by the orthotopic inoculation of OCUM-2MLN cells showed the diffusely infiltrating growth and frequently developed LN metastasis. The oral administration of Ki23057 significantly (P<0.01) reduced the size of orthotopic tumours and the number of the metastatic LN in gastric cancer models. The degree of lymphatic invasion and lymphangiogenesis was significantly (P<0.05) lower in the gastric tumours treated by Ki23057. Ki23057 inhibited the phosphorylation of VEGFR-3 of lymphatic endothelial cells in gastric tumours.

CONCLUSION

The inhibition of lymphangiogenesis targeting VEGFR-3 phosphorylation is a therapeutic strategy for inhibiting LN metastasis of diffuse-type gastric cancer.

Overexpression of vascular endothelial growth factor C increases growth and alters the metastatic pattern of orthotopic PC-3 prostate tumors

Background

Prostate cancer metastasizes to regional lymph nodes and distant sites but the roles of lymphatic and hematogenous pathways in metastasis are not fully understood.

Methods

We studied the roles of VEGF-C and VEGFR3 in prostate cancer metastasis by blocking VEGFR3 using intravenous adenovirus-delivered VEGFR3-Ig fusion protein (VEGFR3-Ig) and by ectopic expression of VEGF-C in PC-3 prostate tumors in nude mice.

Results

VEGFR3-Ig decreased the density of lymphatic capillaries in orthotopic PC-3 tumors (p < 0.05) and inhibited metastasis to iliac and sacral lymph nodes. In addition, tumor volumes were smaller in the VEGFR3-Ig-treated group compared with the control group (p < 0.05). Transfection of PC-3 cells with the VEGF-C gene led to a high level of 29/31 kD VEGF-C expression in PC-3 cells. The size of orthotopic and subcutaneous PC-3/VEGF-C tumors was significantly greater than that of PC-3/mock tumors (both p < 0.001). Interestingly, while most orthotopic PC-3 and PC-3/mock tumors grown for 4 weeks metastasized to prostate-draining lymph nodes, orthotopic PC-3/VEGF-C tumors primarily metastasized to the lungs. PC-3/VEGF-C tumors showed highly angiogenic morphology with an increased density of blood capillaries compared with PC-3/mock tumors (p < 0.001).

Conclusion

The data suggest that even though VEGF-C/VEGFR3 pathway is primarily required for lymphangiogenesis and lymphatic metastasis, an increased level of VEGF-C can also stimulate angiogenesis, which is associated with growth of orthotopic prostate tumors and a switch from a primary pattern of lymph node metastasis to an increased proportion of metastases at distant sites.

Vascular endothelial growth factor-D is correlated with hepatic metastasis from gastric cancer after radical gastrectomy

BACKGROUND

Vascular endothelial growth factor-D (VEGF-D), the activating ligand for vascular endothelial growth factor receptor-3 (VEGFR-3), has been identified as an important endogenic tumor-associated lymphangiogenic factors which can promote lymphatic metastasis from primary tumor. Lymphatic metastasis, which is the most common metastatic method of gastric cancer (GC), is still deemed a potentially relative indicator of distant metastasis from GC. We hypothesize that VEGF-D is associated with hepatic metastasis (HM) from GC after radical gastrectomy by promoting lymphatic metastasis and/or hematogenous metastasis.

METHODS

This study included 150 GC patients who underwent radical gastrectomy (75 cases presented with HM and 75 cases presented without any recurrences). VEGF-D, VEGF-C, VEGF-A, VEGFR-2, VEGFR-3, and microvessel density (MVD) were evaluated by immunohistochemistry. Besides, clinicopathologic variables and prognosis of GC patients were analyzed statistically.

RESULTS

Significant associations were seen between Lauren classification and HM, VEGF-D and HM, VEGFR-3 and HM, MVD and HM, and between nodal status and HM. VEGF-D remained an independent factor for HM from GC after radical gastrectomy. Further significant association was evaluated between high-grade VEGF-D expression and short disease-free survival of HM from GC after radical gastrectomy.

CONCLUSION

VEGF-D, which can induce lymphangiogenesis specifically in many kinds of malignant diseases, is an important factor for predicting HM from GC following radical gastrectomy.

Transcriptional control of endothelial cell development

The transcription factors that regulate endothelial cell development have been a focus of active research for several years, and many players in the endothelial transcriptional program have been identified. This review discusses the function of several major regulators of endothelial transcription, including members of the Sox, Ets, Forkhead, GATA, and Kruppel-like families. This review also highlights recent developments aimed at unraveling the combinatorial mechanisms and transcription factor interactions that regulate endothelial cell specification and differentiation during vasculogenesis and angiogenesis.

High VEGFR-3-positive circulating lymphatic/vascular endothelial progenitor cell level is associated with poor prognosis in human small cell lung cancer

PURPOSE

The newly identified bone marrow-derived cell population, called lymphatic/vascular endothelial progenitor cells (LVEPC), has been shown to contribute to lymph capillary growth in experimental tumor systems. The clinical significance of these cells has not yet been investigated in a human malignancy. Our aim was to study whether peripheral blood circulating LVEPCs participate in the progression of human small cell lung cancer (SCLC).

EXPERIMENTAL DESIGN

A total of 88 patients with limited-stage SCLC and 32 tumor-free control subjects were included. Peripheral blood circulating LVEPC labeled with CD34 and vascular endothelial growth factor receptor-3 (VEGFR3) antibodies and the serum levels of the key lymphangiogenic molecule VEGF-C were measured by flow cytometry and ELISA, respectively.

RESULTS

CD34-positive/VEGFR3-positive LVEPC levels were significantly increased in patients (versus controls; P<0.01), and there was also a significant relationship between LVEPC counts and lymph node metastasis (P<0.01). High pretreatment circulating LVEPC numbers correlated with poor overall survival (P<0.01). Although we observed significantly elevated VEGF-C concentrations in patients (versus controls; P<0.01), there was no significant correlation between VEGF-C and LVEPC levels. Moreover, no significant differences in peripheral blood VEGF-C levels were seen between patients subgrouped by clinicopathologic variables including tumor and lymph node stages and survival.

CONCLUSIONS

Peripheral blood levels of bone marrow-derived LVEPCs are significantly increased in patients with SCLC and correlate with lymphatic involvement and prognosis. This is the first study that shows evidence of increased numbers of circulating LVEPC in patients with a malignant tumor.

The presence of micropapillary features and retraction artifact in core needle biopsy material predicts lymph node metastasis in breast carcinoma

Retraction artifact around tumor cell nests is a characteristic feature of invasive micropapillary carcinoma (IMPC), a special type of breast cancer commonly associated with nodal metastasis. We have recently reported that the extent of retraction artifact in usual invasive ductal carcinomas (IDC) is also a strong predictor of nodal metastasis. We examined whether the presence and extent of micropapillary features and retraction artifact in core needle biopsy of breast cancers can predict nodal metastasis in a prospective series of 47 IMPC and 424 IDC. Micropapillary features were present on core needle biopsy in 28 of 47 IMPC cases. Nodal metastases were found in 21 of 28 and 14 of 19 IMPC cases with and without micropapillary features present on core needle biopsy, respectively. Lymph node metastasis was significantly associated with the presence of micropapillary features, but not with its extent within these tumors. The presence of extensive retraction artifact in core needle biopsy samples of IDC also showed a significant association with nodal metastasis. Our results indicate that the presence of micropapillary features or extensive retraction artifact on core needle biopsy of breast carcinoma can predict nodal metastasis. Our results support the notion that the characteristic clear spaces separating the tumor cells from the stroma in IMPC and IDC of the breast are not a random artifactual phenomenon simply resulting from tissue fixation and processing, but rather they are likely related to altered tumor-stromal interactions, which might have an important role in lymphatic tumor spread.

Vascular endothelial growth factor-C and C-C chemokine receptor 7 in tumor cell-lymphatic cross-talk promote invasive phenotype

Most carcinomas spread to distant sites through lymphatic vessels. Several preclinical and clinical studies have shown a positive correlation between the incidence of lymph node metastasis and secretion of the lymphatic growth factor vascular endothelial growth factor-C (VEGF-C) by tumor cells, suggesting tumor lymphangiogenesis as an escape mechanism. However, recent evidence has shown VEGF receptor-3 (VEGFR-3) expression on tumor cells and autocrine signaling, which increase metastatic potential. Furthermore, there is growing evidence implicating lymphatic-homing chemokine receptors, particularly C-C chemokine receptor 7 (CCR7), in lymph node metastasis. We report here that expressions of VEGF-C and CCR7 by tumor cells act synergistically to promote their invasion toward lymphatics. First, VEGF-C acts to increase lymphatic secretion of CCL21, which in turn drives CCR7-dependent tumor chemoinvasion toward lymphatics. Second, VEGF-C acts in an autocrine fashion to increase tumor invasiveness by increasing the proteolytic activity and motility of tumor cells in a three-dimensional matrix. Both of these effects are VEGFR-3 dependent and evident only in three-dimensional environments. We further verified that VEGF-C induces lymphatic CCL21 up-regulation in vivo by direct injection of VEGF-C protein intradermally in the mouse. Taken together, these results bridge the prometastatic functions of CCR7 and VEGF-C in tumors and show that, beyond lymphangiogenesis, VEGF-C promotes tumor invasion toward lymphatics by both autocrine and CCR7-dependent paracrine signaling mechanisms, which may be a significant cause of lymph node metastasis.

Tumoural expression and circulating level of VEGFR-3 (Flt-4) in metastatic melanoma patients: correlation with clinical parameters and outcome

PURPOSE

The presence of metastases in regional lymph nodes is a strong indicator of poor patient survival in many types of cancer. It has recently been shown that vascular endothelial growth factor-C (VEGF-C), and its receptor VEGFR-3, may play a pivotal role in the promotion of metastasis to regional lymph nodes. This study was designed to detect and evaluate whether the expression of VEGFR-3 or its soluble form plays a role in metastatic malignant melanoma and to determine the relationship with clinicopathological parameters and patients outcome.

EXPERIMENTAL DESIGN

VEGFR-3 expression on melanoma tumour was evaluated by immunohistochemical study. Using a sensitive enzyme-linked immunosorbent assay, sVEGFR-3 was measured in sera of 60 metastatic melanoma patients in comparison with 30 healthy controls.

RESULTS

Immunohistochemical study demonstrated a high expression of VEGFR-3 in melanoma cells. Median level of pre-treatment sVEGFR-3 was significantly higher (p=0.00001) in melanoma patients as compared to healthy donors. No association was noted between VEGFR-3 in situ or in sera and gender, age or LDH level. Median serum VEGFR-3 levels were significantly higher in patients with high tumour burden as compared to those with low tumour burden (p=0.013) as well as in non-responding patients (n=33) as compared to responding ones (n=27). Finally, low level of VEGFR-3 was also related positively to disease free survival (X(2)=3.85, p=0.022).

CONCLUSION

These results suggest that the expression and high pre-treatment sVEGFR-3 level are significantly correlated to poorer prognosis, and may be promising targets for new therapeutic strategies in melanoma disease.

Efficacy and safety of (32)P-nanocolloid for treatment of distant lymph node metastasis in VX2 tumor-bearing rabbits

BACKGROUND

Eradication of micrometastases present in lymph nodes of cancer patients improves their prognosis significantly. Radionuclide therapy possesses the potential to eliminate such metastases.

OBJECTIVE

This study was performed to evaluate the efficacy and safety of (32)P-nanocolloid therapy in the treatment of distant carcinoma cell metastases in lymph nodes of VX2 tumor-bearing rabbits.

METHODS

To obtain VX2 tumor micrometastases in right armpit lymph nodes of 12 male New Zealand white rabbits, VX2 tumors were implanted by hypodermal inoculation into the right anterior limb. Animals were randomly divided into therapy (n = 6) and control (n = 6) groups. (32)P-nanocolloid (0.5 mCi), 95% of which was >50 nm in diameter, was administered to the therapy group, and saline was administered to the control group. Injections were given once weekly for 4 weeks.

RESULTS

2-Deoxy-2[(18)F]-fluoro-D -glucose positron emission tomography revealed that the number of involved lymph nodes and the maximum standardized uptake value decreased in the (32)P-nanocolloid therapy group as compared with the baseline or saline control group (P < 0.05). The expression of the lymphangiogenesis factors vascular endothelial growth factors (VEGF)-C and VEGF-D by VX2 tumor cells present in lymph nodes was significantly lower in the therapy group as compared with the control group. Additionally, apoptotic VX2 tumor cell death was significantly greater in lymph nodes of the therapy as compared with the control group (P < 0.01). With the exception of a decrease in white blood cells of peripheral blood (P < 0.05), standard laboratory values were unaffected throughout the course of therapy with (32)P-nanocolloid.

CONCLUSIONS

These findings support treatment with (32)P-nanocolloid as a safe and effective approach for eradication of lymph node micrometastases.

Lymphatic vessel density is not associated with lymph node metastasis in non-small cell lung carcinoma

CONTEXT

Angiogenesis is essential for tumors to grow and metastasize. Lymphatic metastasis is also an important means of tumor spread. In non-small cell lung carcinoma, the relationship of lymphangiogenesis with lymph node metastasis and, ultimately, patient prognosis is unknown.

OBJECTIVE

To evaluate whether lymphangiogenesis is related to lymph node metastasis and/or overall survival.

DESIGN

Seventy-eight cases of non-small cell lung carcinoma diagnosed from 1987 to 2004 were retrospectively analyzed for intratumoral, peritumoral, and uninvolved adjacent lung tissue lymphatic vessel density (LVD) by D2-40 immunostaining. Lymphatics in 6 cases of squamous dysplasia/carcinoma in situ were similarly evaluated. Appropriate statistical methods were used.

RESULTS

Intratumoral and peritumoral LVD was significantly higher than in the uninvolved adjacent lung but showed no significant association with lymph node stage at the time of tumor resection. Survival in patients with above average D2-40 values was not significantly different when compared with those who had below average values (median survival, 895 vs 1131 days; P = .97). Furthermore, patients with affected lymph nodes had significantly shorter survival (median survival, 467 vs 1425 days; P = .002). Overall, regardless of lymph node status, there was a significantly higher intratumoral (P < .001) and peritumoral (P < .001) LVD when compared with the adjacent uninvolved lung LVD. There was a trend toward increasing LVD with higher grade of squamous dysplasia.

CONCLUSIONS

The results suggest that although lymphangiogenesis occurs in association with non-small cell lung carcinoma, it may not be an important factor in lymph node metastasis. In fact, there is a suggestion that the number of lymphatics that a person inherently has appears to be more important than lymphangiogenesis when it comes to the development of lymph node metastasis.

Lymphatic vessel density as prognostic marker in esophageal adenocarcinoma

We studied tumor lymphatic vascular density (LVD) as a predictive marker for the risk of lymph node (LN) metastasis and its relationship to other prognostic parameters and survival in 75 patients with esophageal adenocarcinoma. Samples were immunostained for D2-40, CD31, and vascular endothelial growth factor (VEGF). Microvessels were counted in densely vascular/lymphatic foci (hot spots) at x400 field (0.17 mm2). Intensity of staining for VEGF was scored on a 2-tiered scale. CD31 microvessel counts showed significant correlation with tumor stage and patient survival (P < .01). D2-40 LVD demonstrated a significant correlation with LN metastases, lymphovascular invasion, and tumor stage (r = 0.45, r = 0.47, and r = 0.37, respectively) and with shorter disease-free survival. D2-40 detected lymphovascular invasion in 29 of 75 cases, more than with CD31 (23/75) and H&E (18/75). VEGF was expressed in 48 (64%) of 75 cases and was significantly correlated with lymphovascular invasion, LN metastases, and overall survival. Our study showed that angiogenesis and lymphangiogenesis have important roles in the progression of esophageal adenocarcinoma.

Combinatorial regulation of endothelial gene expression by ets and forkhead transcription factors

Vascular development begins when mesodermal cells differentiate into endothelial cells, which then form primitive vessels. It has been hypothesized that endothelial-specific gene expression may be regulated combinatorially, but the transcriptional mechanisms governing specificity in vascular gene expression remain incompletely understood. Here, we identify a 44 bp transcriptional enhancer that is sufficient to direct expression specifically and exclusively to the developing vascular endothelium. This enhancer is regulated by a composite cis-acting element, the FOX:ETS motif, which is bound and synergistically activated by Forkhead and Ets transcription factors. We demonstrate that coexpression of the Forkhead protein FoxC2 and the Ets protein Etv2 induces ectopic expression of vascular genes in Xenopus embryos, and that combinatorial knockdown of the orthologous genes in zebrafish embryos disrupts vascular development. Finally, we show that FOX:ETS motifs are present in many known endothelial-specific enhancers and that this motif is an efficient predictor of endothelial enhancers in the human genome.

Lymphatic invasion in cutaneous melanoma is associated with sentinel lymph node metastasis

BACKGROUND

Sentinel lymph node (SLN) metastasis is a major determinant for staging, prognostication and clinical management of patients with cutaneous melanoma. However, the role of lymphatic vs. vascular invasion (VI) for SLN spread remains unclear.

METHODS

We compared the frequency of lymphatic invasion (LI) vs. VI in melanoma sections from 94 patients with a mean three-year clinical follow up using immunostains for the lymphatic endothelial markers D2-40 (podoplanin) and LYVE-1 and the panvascular marker CD31.

RESULTS

LI occurred more frequently than VI (16 vs. 3%, respectively, p = 0.001) and correlated with higher American Joint Committee on Cancer stage at diagnosis (p = 0.0004). In a univariate analysis, LI was strongly associated with SLN metastasis (p = 0.008), independent of tumor thickness. In a multivariate analysis, LI was not a significant risk factor for SLN metastasis. The presence of intratumoral lymphatics (ITLs) was associated with distant metastasis, whereas VI was rare and did not correlate with SLN or distant metastasis. A combination of LI and ITL had higher positive and negative predictive values for the risk of developing SLN metastasis compared with routine histology and VI.

CONCLUSION

Detection of LI in the primary tumor may aid in identifying melanoma patients with the propensity to develop SLN metastasis.

Developmental and pathological lymphangiogenesis: from models to human disease

The lymphatic vascular system, the body's second vascular system present in vertebrates, has emerged in recent years as a crucial player in normal and pathological processes. It participates in the maintenance of normal tissue fluid balance, the immune functions of cellular and antigen trafficking and absorption of fatty acids and lipid-soluble vitamins in the gut. Recent scientific discoveries have highlighted the role of lymphatic system in a number of pathologic conditions, including lymphedema, inflammatory diseases, and tumor metastasis. Development of genetically modified animal models, identification of lymphatic endothelial specific markers and regulators coupled with technological advances such as high-resolution imaging and genome-wide approaches have been instrumental in understanding the major steps controlling growth and remodeling of lymphatic vessels. This review highlights the recent insights and developments in the field of lymphatic vascular biology.

Intratumoural lymphatics in benign and malignant soft tissue tumours

Soft tissue sarcomas do not generally metastasise via lymphatics, and the presence or absence of lymphatic vessels within sarcomas and benign soft tissue tumours is not known. In this study, we determined whether lymphatic vessels were present in a wide range of benign and malignant soft tissue lesions by examining intratumoural expression of the lymphatic endothelial cell markers, Lyve-1 and podoplanin. Intratumoural Lyve-1+/podoplanin+ lymphatics were not identified in sarcomas apart from all cases of epithelioid sarcoma (a tumour which is known to metastasise to lymph nodes) and a few cases of leiomyosarcoma, rhabdomyosarcoma and synovial sarcoma. Intratumoural lymphatics were also absent in most benign soft tissue tumours. Reparative and inflammatory soft tissue lesions contained lymphatics, as did all (pseudosarcomatous) proliferative myofibroblastic lesions including nodular, proliferative and ischaemic fasciitis, elastofibroma, nuchal fibroma and deep fibromatosis. Our results show that most soft tissue sarcomas do not contain intratumoural lymphatics, a finding which is consistent with the infrequent finding of sarcoma metastasis to lymph nodes. In contrast to fibrosarcoma and a number of other malignant spindle cell tumours, proliferative fibroblastic/myofibroblastic lesions of soft tissue contain intralesional lymphatic vessels.

Current insights on the biology and clinical aspects of VEGF regulation

Vascular endothelial growth factor (VEGF) is a key molecule that orchestrates the formation and function of vascular networks. Impaired regulation of angiogenesis is implicated in a number of pathologic states. For instance, neoplasias exhibit uncontrolled angiogenesis, whereas ischemia and states of vascular insufficiency involve reduced VEGF activity. As the role of VEGF has been elucidated in these disease processes, its therapeutic role has been developed. The Food and Drug Administration has approved several anti-VEGF agents for treating colorectal, lung, and kidney cancer. VEGF-inducing agents have also been used experimentally to induce angiogenesis in patients with critical limb ischemia. As more knowledge is gathered about the biology of VEGF and its receptors, there is greater promise for therapeutic modulation of VEGF expression. The purpose of this review is to describe the various therapeutic and biologic factors that regulate the expression of VEGF.

Tumor lymphangiogenesis and melanoma metastasis

Malignant melanomas of the skin primarily metastasize to lymph nodes, and the detection of sentinel lymph node metastases serves as an important prognostic parameter. There is now compelling evidence that melanomas can induce lymphangiogenesis (growth of lymphatic vessels), mainly at the tumor-stroma interface, and that the level of tumor lymphangiogenesis is correlated with the incidence of sentinel lymph node metastases and with disease-free survival. Thus, tumor lymphangiogenesis can serve as a novel prognostic predictor in melanoma. Vascular endothelial growth factor (VEGF)-C, released by melanoma cells and by tumor-associated macrophages, likely represents the major lymphangiogenic factor in melanoma, although other members of the VEGF family might also be involved. The recent discovery that tumors can induce a premetastatic niche, by inducing lymphatic vessel growth in sentinel lymph nodes even before metastasis, and that lymph node lymphangiogenesis enhances metastatic spread, indicates that activated lymphatic vessels represent novel targets for the detection and/or therapy of melanoma metastases.

Molecular control of lymphatic metastasis

The metastatic spread of tumor cells is the most lethal aspect of cancer and often occurs via the lymphatic vasculature. Both experimental tumor models and human clinicopathologic data indicate that growth of lymphatic vessels (lymphangiogenesis) near solid tumors is often associated with lymph node metastasis. Changes in the adhesive properties of lymphatic endothelium near tumors may also facilitate metastatic spread via the lymphatics. Lymphangiogenic growth factors have been identified that promote formation of tumor lymphatics and metastatic spread of tumor cells to lymph nodes. These include the secreted glycoproteins vascular endothelial growth factor-C (VEGF-C) and VEGF-D, which act via their cognate receptor tyrosine kinase VEGF receptor-3 (VEGFR-3) located on lymphatic endothelial cells. Other signaling molecules that have been reported to promote lymphangiogenesis and/or lymphatic metastasis in cancer include VEGF-A, platelet-derived growth factor-BB, and hepatocyte growth factor. However, the quantitative contribution of these proteins to tumor lymphangiogenesis and lymphatic metastasis in different tumor types requires further investigation. In addition, chemokines are thought to play a role in attracting tumor cells and lymphatic vessels to each other. Moreover, it has recently been shown that lymphangiogenic growth factors secreted from a primary tumor can induce lymphangiogenesis in nearby lymph nodes, even before arrival of tumor cells, which may facilitate further metastasis. This article provides an overview of the molecular mechanisms that control lymphatic metastasis and discusses potential therapeutic approaches for inhibiting this process in human cancer.

Lymphatic involvement in lymphangioleiomyomatosis

Lymphangioleiomyomatosis (LAM) is a rare, multisystem disease affecting primarily premenopausal women. The disease is characterized by cystic lung disease, at times leading to respiratory compromise, abdominal tumors (in particular, renal angiomyolipomas), and involvement of the axial lymphatics (e.g., adenopathy, lymphangioleiomyomas). Disease results from the proliferation of neoplastic cells (LAM cells), which, in many cases, have a smooth muscle cell phenotype, express melanoma antigens, and have mutations in one of the tuberous sclerosis complex genes (TSC1 or TSC2). In the lung, LAM cells found in the vicinity of cysts are, at times, localized in nodules and may be responsible for cyst formation through the production of proteases. Lymphatic channels, expressing characteristic lymphatic endothelial cell markers, are found within the LAM lung nodules. LAM cells may also be localized within the walls of the axial lymphatics, and, in some cases, penetrate the wall and proliferate in the surrounding adipose tissue. Consistent with extensive lymphatic involvement in LAM, the serum concentration of VEGF-D, a lymphangiogenic factor, is higher in LAM patients than in healthy volunteers.

Growth hormone promotes lymphangiogenesis

The lymphatic system plays an important role in inflammation and cancer progression, although the molecular mechanisms involved are poorly understood. As determined using comparative transcriptional profiling studies of cultured lymphatic endothelial cells versus blood vascular endothelial cells, growth hormone receptor was expressed at much higher levels in lymphatic endothelial cells than in blood vascular endothelial cells. These findings were confirmed by quantitative real-time reverse transcriptase-polymerase chain reaction and Western blot analyses. Growth hormone induced in vitro proliferation, sprouting, tube formation, and migration of lymphatic endothelial cells, and the mitogenic effect was independent of vascular endothelial growth factor receptor-2 or -3 activation. Growth hormone also inhibited serum starvation-induced lymphatic endothelial cell apoptosis. No major alterations of lymphatic vessels were detected in the normal skin of bovine growth hormone-transgenic mice. However, transgenic delivery of growth hormone accelerated lymphatic vessel ingrowth into the granulation tissue of full-thickness skin wounds, and intradermal delivery of growth hormone resulted in enlargement and enhanced proliferation of cutaneous lymphatic vessels in wild-type mice. These results identify growth hormone as a novel lymphangiogenic factor.

Hypoxia increases breast cancer cell-induced lymphatic endothelial cell migration

Because tumors are characterized by hypoxic environments, we used a novel in vitro noninvasive magnetic resonance imaging assay to examine the influence of invasive MDA-MB-231 breast cancer cells on the invasion and migration of human dermal lymphatic microvascular endothelial cells (HMVEC-dLy) under normoxic and hypoxic conditions. Nonmalignant immortalized MCF-12A human mammary epithelial cells instead of cancer cells or chambers with HMVEC-dLy alone were used as controls for comparison. HMVEC-dLy cells were labeled with a T(2) contrast agent (Feridex), and their invasion and migration through extracellular matrix under normoxic and hypoxic conditions were monitored using magnetic resonance imaging. A significant increase in the invasion and migration of HMVEC-dLy cells was detected in the presence of cancer cells, which further increased significantly under hypoxic conditions. HMVEC-dLy cells formed interconnecting strands extending toward the cancer cells under normoxic but not under hypoxic conditions. Following reoxygenation, these interconnecting strands, extending from HMVEC-dLy cells toward the cancer cells, were observed. These data demonstrate the importance of hypoxia in lymphatic endothelial cell invasion and migration through extracellular matrix in the presence of cancer cells.

Molecular biology and pathology of lymphangiogenesis

The lymphatic vasculature is essential for the maintenance of tissue fluid balance, immune surveillance, and adsorption fatty acids in the gut. The lymphatic vessels are also crucially involved in the pathogenesis of diseases such as tumor metastasis, lymphedema, and various inflammatory conditions. Attempts to control or treat these diseases have drawn a lot of interest to lymphatic vascular research during the past few years. Recently, several markers specific for lymphatic endothelium and models for lymphatic vascular research have been characterized, enabling great technical progress in lymphatic vascular biology, and many critical regulators of lymphatic vessel growth have been identified. Despite these significant achievements, our understanding of the lymphatic vessel development and pathogenesis is still rather limited. Several key questions remain to be resolved, including the relative contributions of different pathways targeting lymphatic vasculature, the molecular and cellular processes of lymphatic maturation, and the detailed mechanisms of tumor metastasis via the lymphatic system.

Circulating lymphangiogenic growth factors in gastrointestinal solid tumors, could they be of any clinical significance?

Metastasis is the principal cause of cancer mortality, with the lymphatic system being the first route of tumor dissemination. The glycoproteins VEGF-C and VEGF-D are members of the vascular endothelial growth factor (VEGF) family, whose role has been recently recognized as lymphatic system regulators during embryogenesis and in pathological processes such as inflammation, lymphatic system disorders and malignant tumor metastasis. They are ligands for the VEGFR-3 receptor on the membrane of the lymphatic endothelial cell, resulting in dilatation of existing lymphatic vessels as well as in vegetation of new ones (lymphangiogenesis). Their determination is feasible in the circulating blood by immunoabsorption and in the tissue specimen by immunohistochemistry and reverse transcription polymerase chain reaction (RT-PCR). Experimental and clinicopathological studies have linked the VEGF-C, VEGF-D/VEGFR3 axis to lymphatic spread as well as to the clinical outcome in several human solid tumors. The majority of these data are derived from surgical specimens and malignant cell series, rendering their clinical application questionable, due to subjectivity factors and post-treatment quantification. In an effort to overcome these drawbacks, an alternative method of immunodetection of the circulating levels of these molecules has been used in studies on gastric, esophageal and colorectal cancer. Their results denote that quantification of VEGF-C and VEGF-D in blood samples could serve as lymph node metastasis predictive biomarkers and contribute to preoperative staging of gastrointestinal malignancies.

Inhibition of human pancreatic cell line MIA PaCa2 proliferation by HA-But, a hyaluronic butyric ester: a preliminary report

OBJECTIVES

Inhibition of histone deacetylase activity is one of the epigenetic mechanisms in the regulation of the cellular gene expression. We investigated the antitumor effect of HA-But, a new histone deacetylase inhibitor, in which hyaluronic acid is esterified with butyric acid residues and selectively bind to CD44, overexpressed in most human cancers, including pancreatic cancer.

METHODS

We analyzed the effect of HA-But on the expression level of some cell cycle (p21 waf1/cip1, p27 kip1, p53, and cyclin D1), apoptosis (BAX, caspase-7, Bcl-2, and survivin), and angiogenesis-related (vascular endothelial growth factor [VEGF] A165, VEGF-C, and VEGF-D) proteins on MIA PaCa-2, a pancreas carcinoma cell line that expressed CD44 in a high percentage (99%) of cells.

RESULTS

HA-But was 7-fold more effective than sodium butyrate in inhibiting cell proliferation; it induced p21 waf1/cip1, p27 kip1, p53, and cyclin D1 modulation, resulting in a block of the cell cycle at G0/G1 and G2/M phases. Moreover, Ha-But induced apoptosis, affecting the expression level of either proapoptotic or antiapoptotic factors, reduced the expression level of VEGF-A165 and VEGF-D, and inhibited the angiogenesis process in vitro.

CONCLUSIONS

On the basis of these results, which demonstrated an interesting antiproliferative, proapoptotic, and antiangiogenic activity, Ha-But could be a promising candidate for the treatment of pancreatic cancer.

Blocking neuropilin-2 function inhibits tumor cell metastasis

Metastasis, which commonly uses lymphatics, accounts for much of the mortality associated with cancer. The vascular endothelial growth factor (VEGF)-C coreceptor, neuropilin-2 (Nrp2), modulates but is not necessary for developmental lymphangiogenesis, and its significance for metastasis is unknown. An antibody to Nrp2 that blocks VEGFC binding disrupts VEGFC-induced lymphatic endothelial cell migration, but not proliferation, in part independently of VEGF receptor activation. It does not affect established lymphatics in normal adult mice but reduces tumoral lymphangiogenesis and, importantly, functional lymphatics associated with tumors. It also reduces metastasis to sentinel lymph nodes and distant organs, apparently by delaying the departure of tumor cells from the primary tumor. Our results demonstrate that Nrp2, which was originally identified as an axon-guidance receptor, is an attractive target for modulating metastasis.

Accelerated orthotopic hepatocellular carcinomas growth is linked to increased expression of pro-angiogenic and prometastatic factors in murine liver fibrosis

BACKGROUND

Most experimental therapy studies are performed in mice that bear subcutaneous or orthotopic hepatoma but are otherwise healthy. We questioned whether a pre-existing fibrosis affects tumour development of implanted syngenic hepatoma cells. To further investigate a selected panel of factors involved in tumour growth, tumour organ samples were characterized for gene expression of vascular endothelial growth factor (VEGF)-A/-C, VEGF receptors Flt1, Flk-1, Flt-4 and for VEGF-A protein levels.

RESULTS

The presented data show that tumour sizes were 3.7-fold increased and fibrotic livers had numerous satellites. Increased tumour sizes were associated with elevated intratumoral VEGF-A protein amounts and intratumoral increased VEGF receptor gene expression levels in tumour tissue from fibrotic livers as compared with non-fibrotic livers. Additionally, intratumoral gene expression levels of matrix metalloproteinase-2 (MMP-2) and MMP-9 were elevated in fibrotic mice.

CONCLUSION

Our results indicate that liver fibrosis stimulates tumour development of implanted syngenic hepatoma cells. Accelerated tumour growth was going along with elevated intratumoral VEGF-A and VEGF-A receptor status, which most probably mediated pro-angiogenic and prometastatic effects in this model. Furthermore, advanced tumour spread was associated with increased MMP-2/-9 expression. These data suggest that the intratumoral VEGF-A proteins levels and VEGF receptor status contribute to accelerated hepatocellular carcinoma development in fibrotic mice and that elevated MMP-2, MMP-9 and VEGF-C levels could promote tumour metastasis in this model.

Tumor lymphangiogenesis and lymphangiogenic growth factors

Recent studies have revealed that malignant tumors can actively induce the formation of new lymphatic vessels and metastasize through the lymphatic system. Tumor-induced lymphangiogenesis driven by tumors expressed lymphangiogenic growth factors such as VEGF family, fibroblast growth factor 2 (FGF-2), angiopoietin-1 (Ang-1), angiopoietin-2 (Ang-2), and platelet-derived growth factors (PDGFs) is correlated with lymph node metastasis in experimental cancer models and in several types of human cancers. Tumor- induced lymphangiogenesis has now been firmly established as a novel mechanism for cancer progression and lymph node metastasis. Recent studies indicate that blockade of the lymphangiogenic growth factors pathway inhibits tumor spread to lymph nodes and likely beyond. The potential effects of most of these newly identified lymphatic growth factors on tumor-induced lymphangiogenesis and lymph node metastasis remain to be further investigated. A number of questions remain to be answered concerning the potential efficacy of targeting at tumor-induced lymphangiogenesis for inhibiting tumor spread to lymph nodes.

A tumor-selective biotherapy with prolonged impact on established metastases based on cytokine gene-engineered MSCs

The poor prognosis for patients with advanced malignancy relates partly to the inability to reverse cancer metastasis. In this study we have investigated an integrated immunotherapy method against pre-established metastases in three kinds of advanced cancer models including B16 melanoma, 4T1 breast tumor, and Hca hepatoma. The progression of metastases into multistep lymph nodes (LN) and internal organs was, markedly impeded in the midway stage and reversed in the ultimate stage following a 20-day course of intravenous immunotherapy [with interleukin-12 (IL-12) gene-engineered mesenchymal stem cells (MSCs), administered once every 5 days P < 0.05)]; the therapy was without systemic toxic effects. As the control, obvious systemic toxicity was observed in the free AdIL-12 group, yet metastasis was partly delayed only in the midway stage but not in the ultimate stage. Enzyme-linked immunosorbent assay (ELISA) showed that the intratumoral expression levels of IL-12 were enhanced by cytokine-engineered MSCs to be tenfold greater than that of free AdIL-12 groups in the ultimate stage; conversely, free AdIL-12 groups showed elevated serum, but not intratumoral levels of IL-12, during the midway stage. Furthermore, histomorphometric analysis revealed a reductive tendency toward reversion of tumor-associated lymphatic sprouts and an increased tumor apoptosis index in engineered MSC groups (P < 0.05). These data indicate the potential of cytokine-engineered MSCs to be considered as an integrated therapeutic weapon for targeting advanced malignancies.