Lymphatic markers, tumour lymphangiogenesis and lymph node metastasis

Loss of CYLD accelerates melanoma development and progression in the Tg(Grm1) melanoma mouse model

The deubiquitinase cylindromatosis (CYLD) is a well-known tumor suppressor, found to be down regulated in many cancer types including breast cancer, colon carcinoma and malignant melanoma. CYLD is suppressed in human melanoma cells by the transcriptional repressor SNAIL1 leading to an increase of their proliferative, invasive and migratory potential. To gain additional insights into the distinct function of this tumor suppressor gene a new mouse model Tg(Grm1)Cyld^-/- was generated. Herewith, we demonstrate that Cyld-deficiency leads to earlier melanoma onset and accelerated tumor growth and metastasis in the GRM1 melanoma mouse model. First, RNA sequencing data revealed a potential role of CYLD in the regulation of genes involved in proliferation, migration and angiogenesis. Experiments using cell lines generated from both primary and metastatic melanoma tissue of Tg(Grm1) Cyld^-/- and Tg(Grm1) Cyld^+/+ mice confirmed that loss of CYLD enhances the proliferative and migratory potential, as well as the clonogenicity in vitro. Moreover, we could show that Cyld-knockout leads to increased vasculogenic mimicry and enhanced (lymph-) angiogenesis shown by tube formation assays, immunohistochemistry and mRNA expression analyses. In summary, our findings reveal new functional aspects of CYLD in the process of (lymph-) angiogenesis and demonstrate its importance in the early process of melanoma progression.

A meta-analysis of the lymphatic microvessel density and survival in gastric cancer with 1809 cases

Lymph node metastasis commonly occurs in gastric cancer. Previous studies have demonstrated that the overexpression of lymphatic microvessel density (LVD) is correlated with various malignancies. To evaluate the potential role of LVD in various malignancies, we conducted a systematic review and meta-analysis to thoroughly investigate the association of LVD expression with tumor progression and survival in gastric cancer. We performed a comprehensive search of common databases and selected studies demonstrating the relationship between LVD expression and gastric cancer prognosis. Hazard ratios (HR) were used to determine the value of LVD for predicting gastric cancer metastasis and prognosis. The data were extracted from the included studies and pooled with the appropriate effects model using STATA 12.0. The results showed that high LVD expression obviously impacted the prognosis of gastric cancer, based on an overall survival (OS) HR of 2.58 (95% CI: 1.91–3.48, P < 0.001) and a disease-free survival (DFS) HR of 2.51 (95% CI: 1.35–4.68, P = 0.004) in the univariate analysis. In addition, the results of the multivariate analysis indicated a remarkable relationship between high LVD expression and gastric neoplasm prognosis. The pooled OS HR was 4.12 (95% CI: 3.45–4.91, P < 0.001). The current meta-analysis shows that high LVD is closely related to tumor metastasis and poor prognosis in gastric malignancy. LVD could be a key factor in tumor lymphatic metastasis. Moreover, LVD is likely a potential index and an effective biomarker for the prediction of patient prognosis.

The role of lymphangiogenesis and angiogenesis in tumor metastasis

BACKGROUND

Metastasis is the main cause of mortality in cancer patients. Two major routes of cancer cell spread are currently being recognized: dissemination via blood vessels (hematogenous spread) and dissemination via the lymphatic system (lymphogenous spread). Here, our current knowledge on the role of both blood and lymphatic vessels in cancer cell metastasis is summarized. In addition, I will discuss why cancer cells select one or both of the two routes to disseminate and I will provide a short description of the passive and active models of intravasation. Finally, lymphatic vessel density (LVD), blood vessel density (BVD), interstitial fluid pressure (IFP) and tumor hypoxia, as well as regional lymph node metastasis and the recently discovered primo vascular system (PVS) will be highlighted as important factors influencing tumor cell motility and spread and, ultimately, clinical outcome.

CONCLUSIONS

Lymphangiogenesis and angiogenesis are important phenomena involved in the spread of cancer cells and they are associated with a poor prognosis. It is anticipated that new discoveries and advancing knowledge on these phenomena will allow an improvement in the treatment of cancer patients.

Expression of Lymphatic Markers in the Adult Rat Spinal Cord

Under physiological conditions, lymphatic vessels are thought to be absent from the central nervous system (CNS), although they are widely distributed within the rest of the body. Recent work in the eye, i.e., another organ regarded as alymphatic, revealed numerous cells expressing lymphatic markers. As the latter can be involved in the response to pathological conditions, we addressed the presence of cells expressing lymphatic markers within the spinal cord by immunohistochemistry. Spinal cord of young adult Fisher rats was scrutinized for the co-expression of the lymphatic markers PROX1 and LYVE-1 with the cell type markers Iba1, CD68, PGP9.5, OLIG2. Rat skin served as positive control for the lymphatic markers. PROX1-immunoreactivity was detected in many nuclei throughout the spinal cord white and gray matter. These nuclei showed no association with LYVE-1. Expression of LYVE-1 could only be detected in cells at the spinal cord surface and in cells closely associated with blood vessels. These cells were found to co-express Iba1, a macrophage and microglia marker. Further, double labeling experiments using CD68, another marker found in microglia and macrophages, also displayed co-localization in the Iba1+ cells located at the spinal cord surface and those apposed to blood vessels. On the other hand, PROX1-expressing cells found in the parenchyma were lacking Iba1 or PGP9.5, but a significant fraction of those cells showed co-expression of the oligodendrocyte lineage marker OLIG2. Intriguingly, following spinal cord injury, LYVE-1-expressing cells assembled and reorganized into putative pre-vessel structures. As expected, the rat skin used as positive controls revealed classical lymphatic vessels, displaying PROX1+ nuclei surrounded by LYVE-1-immunoreactivity. Classical lymphatics were not detected in adult rat spinal cord. Nevertheless, numerous cells expressing either LYVE-1 or PROX1 were identified. Based on their localization and overlapping expression with Iba1, the LYVE-1+ cell population likely represents a macrophage subpopulation, while a significant fraction of PROX1+ cells belong to the oligodendrocytic lineage based on their distribution and the expression of OLIG2. The response of these LYVE-1+ and PROX1+ cell subpopulations to pathological conditions, especially in spinal cord inflammatory conditions, needs to be further elucidated.

Down-Regulation of miR-148a Promotes Metastasis by DNA Methylation and is Associated with Prognosis of Skin Cancer by Targeting TGIF2

BACKGROUND MicroRNAs (miRNA) dysregulation has been considered to be significantly related to the occurrence and development of cancers. Several studies had proved that DNA methylation is an important cause of the abnormal expression of miRNAs. The purpose of this study was to investigate the methylation status of miR-148a and its effects on the metastasis and prognosis of skin cancer, as well as the interaction with TGIF2 gene. MATERIAL AND METHODS According to the qRT-PCR analysis, the expression of miR-148a was down-regulated in tumor tissues compared with the adjacent tissues and healthy controls (P<0.05). In vitro cell metastasis assay revealed that miR-148a could inhibit cell metastasis and its down-regulation promoted metastasis. Luciferase reporter assay found that TGIF2 gene was a target gene and its expression was suppressed by miR-148a in skin cancer. RESULTS Methylation-specific PCR demonstrated that DNA methylation rate of miR-148a was higher in tumor tissues than in adjacent tissues and healthy tissues (P<0.05). miR-148a expression was proved to be epigenetically regulated after the demethylation of it by 5-aza-20-deoxycytidine treatment and qRT-PCR analysis. miR-148a methylation was significantly influenced by many clinicopathologic characteristics such as age (P=0.000), pathological differentiation (P=0.000), and lymph node metastasis (P=0.000). Besides, Kaplan-Meier analysis showed patients with miR-148a methylation lived shorter than those without that (P<0.001). Cox regression analysis manifested that miR-148a methylation (HR=0.053, 95CI%=0.005-0.548, P=0.014) could be serve as an independent prognostic marker for skin cancer. CONCLUSIONS Taken together, the expression of miR-148a was regulated by DNA methylation and targeted by TGIF2. Its methylation may be a potential prognostic indicator in skin cancer.

Presence of lymphatics in a rat tendon lesion model

Tendons lack sufficient blood supply and represent a bradytroph tissue with prolonged healing time under pathological conditions. While the role of lymphatics in wound/defect healing in tissues with regular blood supply is well investigated, its involvement in tendon defects is not clear. We here try to identify the role of the lymphatic system in a tendon lesion model with morphological methods. A rat Achilles tendon lesion model (n = 5) was created via surgical intervention. Two weeks after surgery, animals were killed and lesioned site removed and prepared for polarization microscopy (picrosirius red) and immunohistochemistry using the lymphatic markers PROX1, VEGFR3, CCL21, LYVE-1, PDPN, and the vascular marker CD31. Additionally, DAPI was applied. Untreated tendons served as controls, confocal laser-scanning microscopy was used for documentation. At the lesion site, polarization microscopy revealed a structural reintegration while immunohistochemistry detected band-like profiles immunoreactive for PDPN, VEGFR3, CCL21, LYVE1, and CD31, surrounding DAPI-positive nuclei. PROX1-positive nuclei were detected within the lesion forming lines and opposed to each other. These PROX1-positive nuclei were surrounded by LYVE-1- or VEGFR3-positive surfaces. Few CD31-positive profiles contained PROX1-positive nuclei, while the majority of CD31-positive profiles lacked PROX1-positive nuclei. VEGFR3-, PDPN-, and LYVE-1-positive profiles were numerous within the lesion site, but absent in control tissue. Within 2 weeks, a structural rearrangement takes place in this lesion model, with dense lymphatic supply. The role of lymphatics in tendon wound healing is unclear, and proposed model represents a good possibility to study healing dynamics and lymphangiogenesis in a tissue almost completely lacking lymphatics in physiological conditions.

Consensus statement on the immunohistochemical detection of ocular lymphatic vessels

There is currently considerable controversy about existence and classification of "lymphatic vessels" in the eye. Some of the confusion is certainly caused by inappropriate use (or nonuse) of the correct immunohistochemical markers. Many experts in the field expressed the need for a consensus statement, and, in this perspective, authors offer arguments and solutions to reliably continue with immunohistochemical ocular lymphatic research.

High levels of circulating CD34+/VEGFR3+ lymphatic/vascular endothelial progenitor cells is correlated with lymph node metastasis in patients with epithelial ovarian cancer

AIM

Lymph node metastasis is one of the predictive factors associated with poor prognosis of epithelial ovarian cancer. To clarify the role of CD34 and vascular endothelial growth factor receptor-3-positive (CD34+/VEGFR3+) lymphatic/vascular endothelial progenitor cells (LVEPC) in patients with lymph node metastasis and epithelial ovarian cancer progression, the levels of circulating CD34+/VEGFR3+ LVEPC in epithelial ovarian cancer patients were detected. We also tested the plasma protein levels of VEGF and stromal cell-derived factor to find out their possible relationships with lymph node metastasis in our epithelial ovarian cancer cohort.

MATERIAL AND METHODS

Peripheral blood samples were collected from 54 patients diagnosed as epithelial ovarian cancer, and 31 normal samples as control. The circulating levels of LVEPC were carried out by flow cytometry, and blood protein levels of biomarkers were measured by enzyme-linked immunosorbent assay (ELISA).

RESULTS

The level of circulating LVEPC was significantly higher in patients with ovarian cancer compared with that of healthy controls. There was also a statistically significant correlation between LVEPC levels and surgical staging of epithelial ovarian cancer (P < 0.01).

CONCLUSION

The circulating levels of bone marrow-derived LVEPC are significantly increased in epithelial ovarian cancer patients and these levels correlate with lymph node metastasis too.

Epigenetic disruption of cadherin-11 in human cancer metastasis

Little is known about the molecular events occurring in the metastases of human tumours. Epigenetic alterations are dynamic lesions that change over the natural course of the disease, and so they might play a role in the biology of cancer cells that have departed from the primary tumour. Herein, we have adopted an epigenomic approach to identify some of these changes. Using a DNA methylation microarray platform to compare paired primary tumour and lymph node metastatic cell lines from the same patient, we observed cadherin-11 promoter CpG island hypermethylation as a likely target of the process. We found that CDH11 DNA methylation-associated transcriptional silencing occurred in the corresponding lymph node metastases of melanoma and head and neck cancer cells but not in the primary tumours. Using in vitro and in vivo cellular and mouse models for depleted or enhanced CDH11 activity, we also demonstrated that CDH11 acts as an inhibitor of tumour growth, motility and dissemination. Most importantly, the study of CDH11 5′-CpG island hypermethylation in primary tumours and lymph node metastases of cancer patients showed this epigenetic alteration to be significantly confined to the disseminated cells. Overall, these results indicate the existence of metastasis-specific epigenetic events that might contribute to the progression of the disease. Copyright © 2012 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

MicroRNAs and lymph node metastatic disease in lung cancer

Lymphatic and distant metastases are primary factors in determining survival in patients with lung cancer. The identification of novel molecular biomarkers that can predict the presence of micrometastasis in lymph nodes and their incorporation in traditional histologic staging is needed. MicroRNAs are emerging as powerful biomarkers for several neoplastic disorders. This article reports the experimental results that have recently led to the identification of several microRNAs deregulated in lung cancer that are strongly associated with lymph node metastasis and advanced clinical stage. This evidence indicates that microRNAs are a promising tool for the clinical management of lung cancer.

Identification of CD146 expression, angiogenesis, and lymphangiogenesis as progression, metastasis, and poor-prognosis related markers for gallbladder adenocarcinoma

Gallbladder cancers (GBC) are associated with high disease-specific mortality rates because of no means of early detection and effective therapies. In this study, we investigated CD146 expression, microvessel densities, and lymph vessel densities in 108 adenocarcinomas, 15 gallbladder polyps, 35 chronic cholecystitis tissues, and 46 peritumoral tissues using immunohistochemistry. We demonstrated that positive CD146 expression, and average microvessel and lymph vessel counts in gallbladder adenocarcinomas were significantly higher than those in peritumoral tissues, polyps, and chronic cholecystitis (ps < 0.01). Positive CD146 expression, and average microvessel and lymph vessel counts were also significantly lower in cases with well-differentiated adenocarcinoma, maximal tumor diameter <2 cm, no metastasis of lymph node, and no invasion of regional tissues than in cases with poorly differentiated adenocarcinoma, maximal tumor diameter ≥ 2 cm, metastasis in lymph nodes, and invasion of regional tissues (p < 0.05 or p < 0.01). Univariate Kaplan-Meier analysis showed that increased expression of CD146 (p = 0.056), higher average microvessel counts (p < 0.05), and lymph vessel counts (p < 0.05) were associated with decreased overall survival. Multivariate Cox regression analysis showed that average microvessel and lymph vessel counts (ps < 0.05) were independent prognostic predictors in gallbladder adenocarcinoma. Our study suggested that the elevated expression of CD146, angiogenesis, and lymphangiogenesis might be closely related to progression, invasion, metastasis, and prognosis of gallbladder adenocarcinoma.

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

BACKGROUND

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

METHODS AND RESULTS

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

RESULTS

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

CONCLUSION

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

Lymphatic patterns of colorectal liver metastases

BACKGROUND

Hematogenous spread is considered the predominant pathway for development of colorectal liver metastases (CRLM) and subsequent further tumor dissemination portal nodal involvement is also frequently observed in such cases, suggesting that lymphatics may have a role in the spread of CRLM. The role of lymphatics in the development of liver metastases is, however, controversial. The lymphatic patterns of CRLM were determined using a well established murine model.

METHODS

CRLM were induced using a well established murine intrasplenic colorectal cancer model. Tumors were assessed at varying stages of development, and lymphatic patterns were determined in tumors and liver by immunohistochemistry staining for podoplanin and LYVE-1. Blood vessels were characterized using the vascular marker CD-34. Assessment was undertaken using digital microscopy and image analysis.

RESULTS

Peri- and intratumoral lymphatic vessels were identified by podoplanin staining in all metastases and significantly increased with tumor growth. LYVE-1 staining was also noted but was variable. There was a concurrent significant increase in portal lymphatic staining within the normal liver with increasing growth of CRLM.

CONCLUSION

There is increased expression of lymphatics within CRLM and normal liver with increasing tumor growth. Lymphatic development is likely to play a significant role in the intrahepatic and periportal dissemination of CRLM.

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.

A microRNA DNA methylation signature for human cancer metastasis

MicroRNAs (miRNAs) are small, noncoding RNAs that can contribute to cancer development and progression by acting as oncogenes or tumor suppressor genes. Recent studies have also linked different sets of miRNAs to metastasis through either the promotion or suppression of this malignant process. Interestingly, epigenetic silencing of miRNAs with tumor suppressor features by CpG island hypermethylation is also emerging as a common hallmark of human tumors. Thus, we wondered whether there was a miRNA hypermethylation profile characteristic of human metastasis. We used a pharmacological and genomic approach to reveal this aberrant epigenetic silencing program by treating lymph node metastatic cancer cells with a DNA demethylating agent followed by hybridization to an expression microarray. Among the miRNAs that were reactivated upon drug treatment, miR-148a, miR-34b/c, and miR-9 were found to undergo specific hypermethylation-associated silencing in cancer cells compared with normal tissues. The reintroduction of miR-148a and miR-34b/c in cancer cells with epigenetic inactivation inhibited their motility, reduced tumor growth, and inhibited metastasis formation in xenograft models, with an associated down-regulation of the miRNA oncogenic target genes, such as C-MYC, E2F3, CDK6, and TGIF2. Most important, the involvement of miR-148a, miR-34b/c, and miR-9 hypermethylation in metastasis formation was also suggested in human primary malignancies (n = 207) because it was significantly associated with the appearance of lymph node metastasis. Our findings indicate that DNA methylation-associated silencing of tumor suppressor miRNAs contributes to the development of human cancer metastasis.