Angiogenesis and lymphangiogenesis in stage 1 germ cell tumours of the testis

Angioprevention of Urologic Cancers by Plant-Derived Foods

The number of cancer cases worldwide keeps growing unstoppably, despite the undeniable advances achieved by basic research and clinical practice. Urologic tumors, including some as prevalent as prostate, bladder or kidney tumors, are no exceptions to this rule. Moreover, the fact that many of these tumors are detected in early stages lengthens the duration of their treatment, with a significant increase in health care costs. In this scenario, prevention offers the most cost-effective long-term strategy for the global control of these diseases. Although specialized diets are not the only way to decrease the chances to develop cancer, epidemiological evidence support the role of certain plant-derived foods in the prevention of urologic cancer. In many cases, these plants are rich in antiangiogenic phytochemicals, which could be responsible for their protective or angiopreventive properties. Angiogenesis inhibition may contribute to slow down the progression of the tumor at very different stages and, for this reason, angiopreventive strategies could be implemented at different levels of chemoprevention, depending on the targeted population. In this review, epidemiological evidence supporting the role of certain plant-derived foods in urologic cancer prevention are presented, with particular emphasis on their content in bioactive phytochemicals that could be used in the angioprevention of cancer.

Immune and vascular contributions to organogenesis of the testis and ovary

Gonad development is a highly regulated process that coordinates cell specification and morphogenesis to produce sex-specific organ structures that are required for fertility, such as testicular seminiferous tubules and ovarian follicles. While sex determination occurs within specialized gonadal supporting cells, sexual differentiation is evident throughout the entire organ, including within the interstitial compartment, which contains immune cells and vasculature. While immune and vascular cells have been traditionally appreciated for their supporting roles during tissue growth and homeostasis, an increasing body of evidence supports the idea that these cell types are critical drivers of sexually dimorphic morphogenesis of the gonad. Myeloid immune cells, such as macrophages, are essential for multiple aspects of gonadogenesis and fertility, including for forming and maintaining gonadal vasculature in both sexes at varying stages of life. While vasculature is long known for supporting organ growth and serving as an export mechanism for gonadal sex steroids in utero, it is also an important component of fetal testicular morphogenesis and differentiation; additionally, it is vital for ovarian corpus luteal function and maintenance of pregnancy. These findings point toward a new paradigm in which immune cells and blood vessels are integral components of sexual differentiation and organogenesis. In this review, we discuss the state of the field regarding the diverse roles of immune and vascular cells during organogenesis of the testis and ovary and highlight outstanding questions in the field that could stimulate new research into these previously underappreciated constituents of the gonad.

Increased tumor vascularization is associated with the amount of immune competent PD-1 positive cells in testicular germ cell tumors

Testicular germ cell cancer in a metastatic state is curable with a cisplatin-based first line chemotherapy. However, 10-15% of these patients are resistant to first line chemotherapy and are thus left with only palliative options. Immunotherapies and inhibition of angiogenesis used in multiple types of cancer; however, the molecular context of angiogenesis and immune checkpoints in the development and progression of testicular cancers is still unknown. Therefore, the present study performed tissue micro array based analysis of 84 patients with immunohistochemistry of programmed cell death protein 1 (PD-1), programmed cell death ligand 1 (PD-L1) and vascular endothelial growth factor receptor 2 (VEGFR2) of testicular cancer and corresponding normal appearing testis tissue, matching the results with clinical data. The results demonstrated that PD-L1 was significantly upregulated in testicular tumors and that PD-1 positive cells significantly infiltrated the testicular tumor when compared with normal testicular tissue. VEGFR2 was significantly upregulated in testicular cancer. It was indicated that PD-1 expressing cytotoxic cells may require pathologic tumor vessels to pass the blood-testis-barrier in order to migrate into the tumor. Notably, when matching the clinical data for PD-1, PD-L1 and VEGFR2 there were no differences in expression in the different International Germ Cell Cancer Collaborative Group stages of non-seminoma. These data suggested that the anti-PD-1/PD-L1 immunotherapy and the anti-angiogenic therapy, sequentially or in combination, may be a promising option in the treatment of testicular cancer.

Endocrine Gland-Derived Vascular Endothelial Growth Factor/Prokineticin-1 in Cancer Development and Tumor Angiogenesis

A lot of data suggests endocrine gland-derived vascular endothelial growth factor (EG-VEGF) to be restricted to endocrine glands and to some endocrine-dependent organs. Many evidences show that EG-VEGF stimulates angiogenesis and cell proliferation, although it is not a member of the VEGF family. At the time, a lot of data regarding the role of this growth factor in normal development are available. However, controversial results have been published in the case of pathological conditions and particularly in malignant tumors. Thus, our present paper has been focused on the role of EG-VEGF in normal tissues and various malignant tumors and their angiogenic processes.

Intensive chemotherapy as salvage treatment for solid tumors: focus on germ cell cancer

Germ cell tumors present contrasting biological and molecular features compared to many solid tumors, which may partially explain their unusual sensitivity to chemotherapy. Reduced DNA repair capacity and enhanced induction of apoptosis appear to be key factors in the sensitivity of germ cell tumors to cisplatin. Despite substantial cure rates, some patients relapse and subsequently die of their disease. Intensive doses of chemotherapy are used to counter mechanisms of drug resistance. So far, high-dose chemotherapy with hematopoietic stem cell support for solid tumors is used only in the setting of testicular germ cell tumors. In that indication, high-dose chemotherapy is given as the first or late salvage treatment for patients with either relapsed or progressive tumors after initial conventional salvage chemotherapy. High-dose chemotherapy is usually given as two or three sequential cycles using carboplatin and etoposide with or without ifosfamide. The administration of intensive therapy carries significant side effects and can only be efficiently and safely conducted in specialized referral centers to assure optimum patient care outcomes. In breast and ovarian cancer, most studies have demonstrated improvement in progression-free survival (PFS), but overall survival remained unchanged. Therefore, most of these approaches have been dropped. In germ cell tumors, clinical trials are currently investigating novel therapeutic combinations and active treatments. In particular, the integration of targeted therapies constitutes an important area of research for patients with a poor prognosis.

Current and future biologic markers for disease progression and relapse in testicular germ cell tumors: a review

Testicular germ cell tumors represent a biologically unique disease process. These tumors are exquisitely sensitive to platinum-based chemotherapy, can be cured with surgical metastasectomy, and are known for the integration of biologic markers to stage and assign risk. Exploring further biologic markers that offer insight into the molecular mechanisms that contribute to disease biology is important. In this review, we attempt to summarize the utility of the current and some future biologic markers for disease monitoring and relapse.

Effectivity of pazopanib treatment in orthotopic models of human testicular germ cell tumors

Background

Cisplatin (CDDP) resistance in testicular germ cell tumors (GCTs) is still a clinical challenge, and one associated with poor prognosis. The purpose of this work was to test pazopanib, an anti-tumoral and anti-angiogenic multikinase inhibitor, and its combination with lapatinib (an anti-ErbB inhibitor) in mouse orthotopic models of human testicular GCTs.

Methods

We used two different models of human testicular GCTs orthotopically grown in nude mice; a CDDP-sensitive choriocarcinoma (TGT38) and a new orthotopic model generated from a metastatic GCT refractory to first-line CDDP chemotherapy (TGT44). Nude mice implanted with these orthotopic tumors were treated with the inhibitors and the effect on tumoral growth and angiogenesis was evaluated.

Results

TGT44 refractory tumor had an immunohistochemical profile similar to the original metastasis, with characteristics of yolk sac tumor. TGT44 did not respond when treated with cisplatin. In contrast, pazopanib had an anti-angiogenic effect and anti-tumor efficacy in this model. Pazopanib in combination with lapatinib in TGT38, an orthotopic model of choriocarcinoma had an additive effect blocking tumor growth.

Conclusions

We present pazopanib as a possible agent for the alternative treatment of CDDP-sensitive and CDDP-refractory GCT patients, alone or in combination with anti-ErbB therapies.

Anti-tumour activity of two novel compounds in cisplatin-resistant testicular germ cell cancer

BACKGROUND

Resistance to cisplatin-based chemotherapy is associated with poor prognosis in testicular germ cell cancer, emphasising the need for new therapeutic approaches. In this respect, the therapeutic concept of anti-angiogenesis is of particular interest. In a previous study, we presented two novel anti-angiogenic compounds, HP-2 and HP-14, blocking the tyrosine kinase activity of angiogenic growth factor receptors, such as vascular endothelial growth factor receptor-2 (VEGFR-2), and related signalling pathways in testicular cancer. In this study, we investigated the efficacy of these new compounds in platinum-resistant testicular germ cell tumours (TGCTs), in vitro and in vivo.

METHODS AND RESULTS

Drug-induced changes in cell proliferation of the cisplatin-sensitive TGCT cell line 2102EP and its cisplatin-resistant counterpart 2102EP-R, both expressing the VEGFR-2, were evaluated by crystal violet staining. Both compounds inhibited the growth of cisplatin-resistant TGCT cells in a dose-dependent manner. In combination experiments with cisplatin, HP-14 revealed additive growth-inhibitory effects in TGCT cells, irrespective of the level of cisplatin resistance. Anti-angiogenic effects of HP compounds were confirmed by tube formation assays with freshly isolated human umbilical vein endothelial cells. Using TGCT cells inoculated onto the chorioallantoic membrane of fertilised chicken eggs (chicken chorioallantoic membrane assay), the anti-angiogenic and anti-proliferative potency of the novel compounds was also demonstrated in vivo. Gene expression profiling revealed changes in the expression pattern of genes related to DNA damage detection and repair, as well as in chaperone function after treatment with both cisplatin and HP-14, alone or in combination. This suggests that HP-14 can revert the lost effectiveness of cisplatin in the resistant cells by altering the expression of critical genes.

CONCLUSION

The novel compound HP-14 effectively inhibits the growth of cisplatin-resistant TGCT cells and suppresses tumour angiogenesis. Thus, HP-14 may be an interesting new agent that should be further explored for TGCT treatment, especially in TGCTs that are resistant to cisplatin.

Lymph vessel density in seminomatous testicular cancer assessed with the specific lymphatic endothelium cell markers D2-40 and LYVE-1: correlation with pathologic parameters and clinical outcome

OBJECTIVES

To evaluate the role of lymph vessel density (LVD) and lymphangiogenesis in seminomatous testicular cancer (STC) by using the lymphatic endothelial cell (LEC) markers LYVE-1 and D2-40.

METHODS AND MATERIALS

Paraffin embedded tumor specimens from 40 patients with STC were stained by specific D2-40 and Lyve-1 antibodies. LVD was measured in different representative and standardized areas. Fluorescence double immunostaining for Lyve-1 and Ki-67 was performed and results were correlated with clinicopathologic data. The median follow-up period was 55 (range 10-135) months.

RESULTS

Mean intratumoral LVD (D2-40: 1.30 ± 1.99; Lyve-1: 1.82 ± 2.34) was significantly lower than peritumoral LVD (D2-40: 4.94 ± 2.58; Lyve-1: 4.62 ± 2.73) and LVD in nontumoral areas (D2-40: 4.81 ± 3.79; Lyve-1: 4.22 ± 3.19). There was no significant difference between LVD measures when using D2-40 or LYVE-1. Detection rates of lymphatic vascular invasion (LVI) were significantly higher than in conventional HE-stained sections (77.5% vs. 52.5%). No proliferating lymphatic vessels were found.

CONCLUSIONS

We found that LVD is decreased within tumor areas of STC. Despite a higher peritumoral LVD, no signs of proliferating endothelial cells were observed, suggesting a lack of lymphangiogenesis in STC. Detection of LVI can be optimized by specific D2-40 or LYVE-1 staining.

Novel compounds with antiangiogenic and antiproliferative potency for growth control of testicular germ cell tumours

BACKGROUND

Testicular germ cell tumour (TGCT) is the most common cause of death from solid tumours in young men and especially for platinum-refractory patients novel treatment approaches are urgently needed. Using an in silico screening approach for the detection of novel cancer drugs with inhibitory effects on the tyrosine kinase activity of growth factors (e.g., VEGFR, PDGFR), we identified two compounds (HP-2 and HP-14) with antiangiogenic and antiproliferative potency, which were evaluated in endothelial cell models and TGCT cells.

RESULTS

HP-2 and HP-14 effectively inhibited the growth of VEGFR-2-expressing TGCT cell lines (Tera-1, Tera-2 and 2102EP) and endothelial cell models, while they failed to supress the growth of VEGFR-2-lacking tumour cells. cDNA-microarrays revealed an inhibition of the expression of several growth factor receptors and related signal transduction molecules. Vascular endothelial growth factor (VEGF)-induced cell migration was also potently inhibited. Cell cycle-regulating proteins such as p21 and p27 were upregulated, leading to an S-phase arrest. Additional in vivo evaluations confirmed the antiangiogenic potency and good tolerability of the novel substances.

CONCLUSION

Our data show that the identified novel compounds inhibit the growth of TGCT cells and decrease angiogenic microvessel formation. The mode of action involves cell cycle arresting effects and changes in the expression pattern of several angiogenic genes. The novel compounds may qualify as new candidates for targeted treatment of TGCT and merit further evaluation.

Serum human chorionic gonadotropin is associated with angiogenesis in germ cell testicular tumors

BACKGROUND

Germ cell testicular tumors have survival rate that diminishes with high tumor marker levels, such as human chorionic gonadotropin (hCG). hCG may regulate vascular neoformation through vascular endothelial growth factor (VEGF). Our purpose was to determine the relationship between hCG serum levels, angiogenesis, and VEGF expression in germ cell testicular tumors.

METHODS

We conducted a retrospective study of 101 patients. Serum levels of hCG, alpha-fetoprotein (AFP), and lactate dehydrogenase were measured prior to surgery. Vascular density (VD) and VEGF tissue expression were determined by immunohistochemistry and underwent double-blind analysis.

RESULTS

Histologically, 46% were seminomas and 54%, non-seminomas. Median follow-up was 43 +/- 27 months. Relapse was present in 7.5% and mortality in 11.5%. Factors associated with high VD included non-seminoma type (p = 0.016), AFP > or = 14.7 ng/mL (p = 0.0001), and hCG > or = 25 mIU/mL (p = 0.0001). In multivariate analysis, the only significant VD-associated factor was hCG level (p = 0.04). When hCG levels were stratified, concentrations > or = 25 mIU/mL were related with increased neovascularization (p < 0.0001). VEGF expression was not associated with VD or hCG serum levels.

CONCLUSION

This is the first study that relates increased serum hCG levels with vascularization in testicular germ cell tumors. Hence, its expression might play a role in tumor angiogenesis, independent of VEGF expression, and may explain its association with poor prognosis. hCG might represent a molecular target for therapy.

Potential therapeutic strategies for lymphatic metastasis

Physiologically, the lymphatic system regulates fluid volume in the interstitium and provides a conduit for immune cells to travel to lymph nodes, but pathologically, the lymphatic system serves as a primary escape route for cancer cells. Lymphatic capillaries have a thin discontinuous basement membrane, lack pericyte coverage and often contain endothelial cell gaps that can be invaded by immune cells (or tumor cells). In addition, tumor cells and stromal cells in the tumor microenvironment secrete factors that stimulate lymphangiogenesis, the growth of lymphatic endothelial cells and the sprouting of lymphatic capillaries. As a result, many tumors are surrounded by large, hyperplastic, peri-tumoral lymphatic vessels and less frequently are invaded by intra-tumoral lymphatic vessels. Carcinoma cells commonly metastasize through these lymphatic vessels to regional lymph nodes. The presence of metastatic cells in the sentinel lymph node is a prognostic indicator for many types of cancer, and the degree of dissemination determines the therapeutic course of action. Lymphangiogenesis is currently at the frontier of metastasis research. Recent strides in this field have uncovered numerous signaling pathways specific for lymphatic endothelial cells and vascular endothelial cells. This review will provide an overview of tumor lymphangiogenesis and current strategies aimed at inhibiting lymphatic metastasis. Novel therapeutic approaches that target the tumor cells as well as the vascular and lymphatic endothelial compartments are discussed.

An open-label, multicenter phase II trial of capecitabine in patients with cisplatin-refractory or relapsed germ cell tumors

The objective of this multicenter phase II trial was to evaluate the efficacy and tolerability of capecitabine in patients with cisplatin-refractory or relapsed germ cell tumors. Between March 2003-June 2004, 14 patients refractory to at least two regimens of cisplatin-based chemotherapy or with relapse after high-dose chemotherapy and autologous peripheral blood stem cell transplantation received 1250 mg/qm capecitabine orally twice daily for 14 days in 3-week cycles. Treatment was continued until tumor progression. All patients were heavily pretreated with a median number of four previous lines of chemotherapy (range, 2-11) and 86% had relapsed after high-dose chemotherapy with peripheral blood stem cell transplantation. No patient responded to study treatment. Nine patients (64%) had progressive disease after two cycles. Two patients already stopped treatment after one cycle, because of a clinically overt tumor progression. One patient died of his tumor progression at the end of the second cycle. Two patients received four cycles of capecitabine, as progression was less than 30%. The median survival time was 4 months (range, 0-10). The toxicity profile was favorable. Eighty-six percent of the cycles could be applied without dose modifications or delay. Grade III/IV toxicities (diarrhea and anorexia in one patient each) occurred in 7% of the cases. No hematotoxicity grade III/IV was observed. Neutropenia grade I/II was documented in 21%, anemia in 35% and thrombocytopenia in 14% of the patients. Capecitabine was well tolerated, but is not effective in heavily pretreated patients with cisplatin-refractory or relapsed germ cell tumors.

Transition from preinvasive carcinoma in situ to seminoma is accompanied by a reduction of connexin 43 expression in Sertoli cells and germ cells

Carcinoma in situ (CIS) represents the preinvasive stage of human germ cell tumors, but the mechanism leading to pubertal proliferation and invasive malignancy remains unknown. Among testicular gap junctional proteins, connexin 43 (Cx43) represents the predominant Cx, and, previously, an inverse correlation between synthesis of Cx43 protein and progression of tumor development was detected. In the present study, using cDNA microarray analysis, in situ hybridization, semiquantitative reverse transcription-polymerase chain reaction (RT-PCR) from tissue homogenates, RT-PCR from microdissected tubules with normal spermatogenesis and CIS, and seminoma cells from invasive seminoma, we asked whether reduction of Cx43 protein is accompanied by a change of Cx43 transcripts. We detected a significant downregulation of Cx43 at mRNA level in Sertoli and germ cells starting in seminiferous tubules infiltrated with CIS and resulting in a complete loss in seminoma cells. It was demonstrated, that downregulation of Cx43 expression in neoplastic human testis takes place at the transcriptional level and starts in CIS. This reduction of Cx43 expression further suggests that early intratubular derangement in Cx43 gene expression and disruption of intercellular communication between Sertoli cells and/or Sertoli and preinvasive tumor cells may play a role in the progression phase of human seminoma development.

Human endocrine gland-derived vascular endothelial growth factor: expression early in development and in Leydig cell tumors suggests roles in normal and pathological testis angiogenesis

Angiogenesis is essential for tumor growth and metastasis. A new human angiogenic mitogen, endocrine gland-derived vascular endothelial growth factor (EG-VEGF), has been recently identified; its expression pattern is restricted to endocrine glands, with the highest expression in testis. We used in situ hybridization and newly generated monoclonal antibodies to investigate the expression of EG-VEGF in normal human prenatal and adult testis and in 48 human testicular tumors of different subtypes. We found that EG-VEGF was expressed from 14 wk until birth in human fetal testis. In the adult testis, EG-VEGF was strongly expressed only in Leydig cells. In testicular tumors, EG-VEGF was expressed specifically in Leydig cell tumors, whereas germ cell-derived neoplasms, including carcinoma in situ, seminoma, and nonseminomatous germ cell tumors, were negative for this antigen. In contrast, VEGF, another powerful angiogenic factor, was expressed in seminoma, but very weakly in Leydig cell tumors. Interestingly, we found that Leydig cell tumors presented vessel surface density 3.2-fold higher than seminoma. These findings argue that human EG-VEGF may play a role in angiogenesis both during the early endocrine development of testis and in the adult testis as well as in Leydig cell tumor growth.

Marked increase of the growth factors pleiotrophin and fibroblast growth factor-2 in serum of testicular cancer patients

BACKGROUND

Malignant tumors of the testis are among the most common cancers in men between the ages of 15 and 30 years. The sensitivity of detection of known tumor markers depends upon the tumor histology and stage. In other cancers, increased serum concentrations of various angiogenic growth factors have been described as potential markers for tumor progression and metastasis. One main histological feature of testicular cancer is profound angiogenesis.

DESIGN

In this study, we investigated by sensitive enzyme-linked immunosorbent assays (ELISAs) the levels of various growth and angiogenesis factors in the serum of testicular cancer patients as compared with normal control subjects. For the most profoundly increased growth factors, pleiotrophin (PTN) and fibroblast growth factor-2 (FGF-2), we furthermore analyzed tumor lysates by northern blotting, RT-PCR and ELISA.

RESULTS

We demonstrate a marked elevation of average serum levels of PTN ( approximately 20-fold) and of FGF-2 ( approximately 7-fold) in patients and expression of both growth factors in tumor biopsies. To a lesser extent, vascular endothelial growth factor (VEGF) and epidermal growth factor (EGF) serum levels were increased, whereas FGF-4 and transforming growth factor-beta levels were similar to those in normal control subjects. Elevation of PTN, FGF-2, EGF and VEGF was detected in seminomatous as well as non-seminatous tumors, and even in early stages.

CONCLUSIONS

PTN and FGF-2 may represent promising new diagnostic markers for testicular cancer with high sensitivity even in early-stage testicular cancer. Further studies are warranted to extend our analyses.

Angiogenetic protooncogene ets-1 induced neovascularization is involved in the metastatic process of testicular germ cell tumors

BACKGROUND

Induction of angiogenesis is essential for tumor growth and metastasis. The role of angiogenetic factors and corresponding microvessel density in the development of metastasis of nonseminomatous testicular germ cell tumors (NSGCTs) is not clearly defined. Aim of the study was to gain new insights in the expression of the above described factors in different histological subtypes of metastatic and non-metastatic NSGCTs.

METHODS

Paraffin-embedded tissues of 39 NSGCTs (19 organ confined NSGCTs, pathological stage I and 20 NSGCTs with metastasis, pathological stage II) were immunohistochemical stained with antibodies for vascular endothelial growth factor (VEGF) with the ligands flt and flk, for the angiogenetic factor ets-1 as well as for endothelial markers CD34 and CD105. Areas representative of the invasive tumor were selected and the different histological subtypes were microdissected. For each subtype immunohistochemical expression in metastatic and organ confined tumors was assessed. Additionally, neovascularization was investigated by microvessel density and correlated to the markers of angiogenesis.

RESULTS

VEGF expression was most often seen in teratoma components. There was no significant difference in the expression of VEGF, flt or flk in metastatic vs. organ confined tumors and their different histological subtypes seen. Only frequency and intensity for ets-1 expression differed significantly between metastatic and non-metastatic tumors. Using CD105 a significantly higher microvessel density was observed in stage II tumors. In addition, microvessel density determined by CD105 correlated significantly with ets-1 expression.

DISCUSSION

VEGF and its receptors flt and flk seem not be involved in the progress of metastatic development of NSGCTs. Only expression of ets-1, a protooncogene involved in tumor angiogenesis, was significantly higher and more frequently seen in metastatic NSGCTs. A difference in microvessel density between tumor stages could only be observed if the specific CD105 antibody was used. In contrast, no difference in microvessel distribution between histological subtypes or tumor stages was observed if the pan-endothelial marker CD34 was used. Furthermore, ets-1 expression was significantly associated with CD105 microvessel density. Conclusively, ets-1 together with microvessel density determined by CD105 may have prognostic value in the multistep event of carcinogenesis.

Evaluation of angiogenesis in canine seminomas by quantitative immunohistochemistry

Angiogenesis, which assists in supplying the nutritional and respiratory needs of proliferating cells, is essential for tumour growth. Angiogenic control is complex, involving a network of cytokines, in particular vascular endothelial growth factor (VEGF), a potent endothelial cell mitogen which also stimulates neoplastic cell proliferation. The purpose of this study was to evaluate VEGF expression and microvessel density (number of microvessels per mm(2)), in canine seminomas. VEGF expression and microvessel density were higher in seminomas than in normal testicular tissue; both parameters were higher in diffuse tumours than in intratubular tumours. These data demonstrate an increase in angiogenesis in the more malignant histological types of seminoma and suggest that both VEGF and microvessel density are useful criteria for evaluating the intrinsic malignancy and growth potential of canine testicular tumours.

Lymphangiogenesis in tumors: what do we know?

Lymphangiogenesis, the growth of new lymphatic vessels, has long been regarded as a putative efficient pathway to neoplastic metastization. However, until recently consistent data regarding reliable lymphatic endothelial cell markers were lacking. Moreover, the presence of new formed lymphatic vessels was considered a largely disputable concept. Now, this scenario has changed significantly, owing to consistent reports describing novel lymphatic endothelial cell (LEC) markers, the demonstration of new formed lymphatic vessels within the bulk of the tumor in animal models and human neoplasms, and the characterization of the VEGF-C/VEGFR-3 pathway. We herein review the major breakthroughs in the field of lymphangiogenesis, with special emphasis on novel and reliable LEC markers, such as prox-1, LYVE-1, and podoplanin, as well as on the pathological assessment of lymphangiogenesis as a putative prognostic factor for human neoplasms.