Tumor lymphangiogenesis and new drug development

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Abstract

Traditionally, tumor-associated lymphatic vessels have been regarded as passive by-standers, serving simply as a drainage system for interstitial fluid generated within the tumor. However, with growing evidence that tumors actively induce lymphangiogenesis, and that the number of lymphatic vessels closely correlates with metastasis and clinical outcome in various types of cancer, this picture has changed dramatically in recent years. Tumor-associated lymphatic vessels have now emerged as a valid therapeutic target to control metastatic disease, and the first specific anti-lymphangiogenic drugs have recently entered clinical testing. Furthermore, we are just beginning to understand the whole functional spectrum of tumor-associated lymphatic vessels, which not only concerns transport of fluid and metastatic cells, but also includes the regulation of cancer stemness and specific inhibition of immune responses, opening new venues for therapeutic applications. Therefore, we predict that specific targeting of lymphatic vessels and their function will become an important tool for future cancer treatment.

Introduction

The lymphatic system is one of the two vascular systems present in the human body.

In contrast to the blood vascular system, it is blind ended and unidirectional, and lacks a central pump. Its principal functions under physiologic conditions are the drainage of interstitial fluid, the absorption of dietary fats in the gastrointestinal tract, and the transport of immune cells and antigens from peripheral to lymphoid tissues (reviewed in [1]). In order to fulfill these functions, lymphatic capillaries form an extensive network in most peripheral organs, which is particularly dense at potential entry sites for pathogens, such as the skin and the mucosae. Lymphatic capillaries merge to form larger pre-collecting and collecting vessels, which ultimately converge in the thoracic duct which is connected to the blood circulation via the jugular vein. The microanatomy of the lymphatic capillaries facilitates the entry of interstitial fluid.

Capillary lymphatic endothelial cells (LECs) form specialized, flap-like junctions, so called “primary valves”, which also allow entry of immune cells such as dendritic cells, while preventing leakage of fluid back into the tissue. Capillaries have a discontinuous basement membrane and no pericyte coverage, making them even more permissive for fluid and cell entry. Anchoring filaments, connecting the capillary LECs with the surrounding extracellular matrix, prevent the collapse of capillaries, even when the external pressure is high. Pre-collecting and collecting lymphatic vessels on the other hand are generally resistant to fluid transport through the vessel wall. Collector LECs form tight, “zipper-like” junctions, are surrounded by a complete basement membrane, and are further supported by perivascular cells (reviewed in [2]). Once inside the lymphatic network, the fluid (now called lymph) is actively transported from the periphery back to the blood circulation. This is achieved by external pressure on the vessels, e.g. due to body movement and skeletal muscle activity, as well as an intrinsic pumping activity in collecting vessels, which is mediated by perivascular smooth muscle cells. Valves in collecting vessels prevent the backflow of lymph, and a specialized valve at the lympho-venous interface between the thoracic duct and the jugular vein impedes retrograde entry of venous blood into the lymphatic system.

On its way down the lymphatic tree, the lymph also passes several lymph nodes, the principal sites for encounters between antigen, antigen-presenting cells (APCs), and cells of the adaptive immune system. Antigen derived from the periphery is transported with the lymph either as free, soluble molecules, or may be taken up and transported by dendritic cells. Within the lymph nodes, APCs present processed antigen to the T- and B-cells, leading to specific immune responses or peripheral tolerance, depending on the context. Therefore, a functional lymphatic system is crucial for the initiation and regulation of adaptive immune responses.

Lymphangiogenesis is defined as the formation of new lymphatic vessels from pre-existing ones, and is considered the predominant mechanism of postnatal lymphatic vessel growth. In addition, lymphatic vessel remodeling can involve enlargement of preexisting lymphatic vessels. In general, lymphangiogenesis is needed for the development of the lymphatic system during embryogenesis, but does not occur in a healthy, adult organism, with a few exceptions, e.g. in the ovaries and the mammary tissue during the female reproductive cycle. However, lymphangiogenesis as well as enlargement of pre-existing lymphatic vessels are induced in various pathological conditions, most prominently during acute and chronic inflammatory conditions, wound healing, but also in various types of human cancers and experimental tumor models (reviewed in [3], [4]). This is due to activation of lymphangiogenic pathways such as the VEGF-C/VEGFR-3 pathway, as outlined below (Section 3). In tumors, lymphangiogenesis may occur both within the primary tumor mass and/or in the tumor periphery, leading to formation of intratumoral (ILVs) and peritumoral lymphatic vessels (PLVs), respectively. ILVs are often small in caliber and appear collapsed in histological tissue sections, which may be explained by the high interstitial pressure within the tumor mass and/or the loss of the normal tissue architecture, impeding the function of the anchoring filaments. Consequently, ILVs have been hypothesized to be functionally compromised [5], [6], [7], [8]. On the other hand, PLVs often appear grossly dilated, tortuous in shape, and filled with cells, and have thus been considered as the major route for fluid and cell drainage from the primary tumor (reviewed in [4]) (Fig. 1). Of note, tumor lymphangiogenesis is very heterogeneous, with some tumor types showing a very low degree or even absence of lymphatic vessel growth [9], [10]. Despite this, the tumor mass may still acquire ILVs and/or PLVs by “trapping” them from the tissue into which the tumor is expanding.

Lymph drained from the primary tumor is transported by the lymphatic system through one or several lymph nodes on its way back to the blood circulation, the first of which is referred to as the “sentinel lymph node” (SLN). During tumor growth, the SLN frequently expands in size and cellularity, concomitant with a dramatic lymphatic expansion within the node. This may be due to metastatic tumor cells entering the node and expressing lymphangiogenic factors. However, experimental work by our lab has shown that SLN lymphangiogenesis occurs even before the arrival of metastatic cells, and is most likely stimulated by factors drained from the primary tumor [11], [12], [13]. By this mechanism, tumors have been suggested to prepare a “pre-metastatic niche” in the SLN to facilitate later dissemination to the node. Another potential source of lymphangiogenic factors in the SLN are immune cells, such as B-cells or macrophages, which have been found to regulate LN lymphangiogenesis in inflammatory conditions [14], [15]. Inflammatory cytokines drained from the primary tumor are likely to induce expression of lymphangiogenic factors in these cells, and also to induce additional recruitment of immune cells from the blood circulation.

Section snippets

Lymphatic metastasis

Whereas lymphatic expansion plays an important, protective role in acute and chronic inflammatory conditions [16], [17], the role of lymphatic vessels during tumor growth and progression is rather opposite. Although tumor-associated lymphatic vessels may aid in relieving interstitial fluid pressure, tumors have adapted to exploit the lymphatic system for their own benefit, including cancer cell dissemination. Metastasis to tumor draining lymph nodes is common in melanoma and in many types of

VEGF-C/-D

In the past decade, multiple factors promoting tumor lymphangiogenesis have been identified, of which VEGF-C and VEGF-D are the most prominent and best investigated ones. During embryonic development, VEGF-C is absolutely required for the development of the lymphatic system, whereas VEGF-D appears to be dispensable [38], [39]. However, both growth factors have strong lymphangiogenic effects in the adult [40]. VEGF-C and -D are expressed by tumor cells as well as stromal cells, including

Development of anti-lymphangiogenic drugs

Tumor lymphangiogenesis represents a potential target to treat or prevent metastatic disease. Nevertheless, only very few drugs specifically designed to block this process have entered clinical testing so far (Fig. 2). Why is that so? On the one hand, the discovery of tumor lymphangiogenesis and its role in the metastatic process is still relatively recent. Considering the long time frames required to develop a drug from preclinical to clinical trials, many more lymphangiogenesis inhibitors can

Conclusion and outlook

Over the last 15 years, tumor-associated lymphangiogenesis has been recognized as a new target to fight metastatic disease. As of now, the development of specific anti-lymphangiogenic drugs has finally reached the stage of clinical trials. However, much remains to be done: On the one hand, better imaging methods are needed to accurately monitor the efficiency of such drugs, and to identify those patients that would most likely benefit from the treatment. Secondly, anti-lymphangiogenic treatment

Acknowledgement

Work in the authors' laboratory is supported by Swiss National Science Foundation grant 310030B_147087, European Research Council grant LYVICAM, Oncosuisse, Krebsliga Zurich and Leducq Foundation Transatlantic Network of Excellence grant Lymph Vessels in Obesity and Cardiovascular Disease (11CVD03) (all to MD).

References (216)

  • S.F. Schoppmann et al.

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

    Am. J. Pathol.

    (2002)
  • R.C. Ji

    Hypoxia and lymphangiogenesis in tumor microenvironment and metastasis

    Cancer Lett.

    (2014)
  • F. Morfoisse et al.

    Hypoxia induces VEGF-C expression in metastatic tumor cells via a HIF-1alpha-independent translation-mediated mechanism

    Cell Rep.

    (2014)
  • R. Valtola et al.

    VEGFR-3 and its ligand VEGF-C are associated with angiogenesis in breast cancer

    Am. J. Pathol.

    (1999)
  • Y. Zhang et al.

    Activation of vascular endothelial growth factor receptor-3 in macrophages restrains TLR4-NF-kappaB signaling and protects against endotoxin shock

    Immunity

    (2014)
  • S. Karaman et al.

    Blockade of VEGF-C and VEGF-D modulates adipose tissue inflammation and improves metabolic parameters under high-fat diet

    Mol. Metab.

    (2015)
  • S.A. Stacker et al.

    Biosynthesis of vascular endothelial growth factor-D involves proteolytic processing which generates non-covalent homodimers

    J. Biol. Chem.

    (1999)
  • L. Eklund et al.

    Angiopoietin signaling in the vasculature

    Exp. Cell Res.

    (2013)
  • R. Cao et al.

    Hepatocyte growth factor is a lymphangiogenic factor with an indirect mechanism of action

    Blood

    (2006)
  • N. Platonova et al.

    Evidence for the interaction of fibroblast growth factor-2 with the lymphatic endothelial cell marker LYVE-1

    Blood

    (2013)
  • D. Marino et al.

    Activation of the epidermal growth factor receptor promotes lymphangiogenesis in the skin

    J. Dermatol. Sci.

    (2013)
  • A. Bracher et al.

    Epidermal growth factor facilitates melanoma lymph node metastasis by influencing tumor lymphangiogenesis

    J. Invest. Dermatol.

    (2013)
  • R. Cao et al.

    PDGF-BB induces intratumoral lymphangiogenesis and promotes lymphatic metastasis

    Cancer Cell

    (2004)
  • T. Karnezis et al.

    VEGF-D promotes tumor metastasis by regulating prostaglandins produced by the collecting lymphatic endothelium

    Cancer Cell

    (2012)
  • K.R. Klein et al.

    Decoy receptor CXCR7 modulates adrenomedullin-mediated cardiac and lymphatic vascular development

    Dev. Cell

    (2014)
  • C. Eveno et al.

    Netrin-4 delays colorectal cancer carcinomatosis by inhibiting tumor angiogenesis

    Am. J. Pathol.

    (2011)
  • F. Larrieu-Lahargue et al.

    Netrin-4 induces lymphangiogenesis in vivo

    Blood

    (2010)
  • N. Singh et al.

    Soluble vascular endothelial growth factor receptor 3 is essential for corneal alymphaticity

    Blood

    (2013)
  • T. Heishi et al.

    Endogenous angiogenesis inhibitor vasohibin1 exhibits broad-spectrum antilymphangiogenic activity and suppresses lymph node metastasis

    Am. J. Pathol.

    (2010)
  • M. Oka et al.

    Inhibition of endogenous TGF-beta signaling enhances lymphangiogenesis

    Blood

    (2008)
  • K. Alitalo

    The lymphatic vasculature in disease

    Nat. Med.

    (2011)
  • L.C. Dieterich et al.

    Lymphatic vessels: new targets for the treatment of inflammatory diseases

    Angiogenesis

    (2014)
  • S.A. Stacker et al.

    Lymphangiogenesis and lymphatic vessel remodelling in cancer

    Nat. Rev. Cancer

    (2014)
  • T.P. Padera et al.

    Lymphatic metastasis in the absence of functional intratumor lymphatics

    Science

    (2002)
  • A.J. Leu et al.

    Absence of functional lymphatics within a murine sarcoma: a molecular and functional evaluation

    Cancer Res.

    (2000)
  • M. Stanczyk et al.

    Lack of functioning lymphatics and accumulation of tissue fluid/lymph in interstitial “lakes” in colon cancer tissue

    Lymphology

    (2010)
  • W.L. Olszewski et al.

    Lack of functioning intratumoral lymphatics in colon and pancreas cancer tissue

    Lymphat. Res. Biol.

    (2012)
  • B. Agarwal et al.

    Lymphangiogenesis does not occur in breast cancer

    Am. J. Surg. Pathol.

    (2005)
  • S. Hirakawa et al.

    VEGF-A induces tumor and sentinel lymph node lymphangiogenesis and promotes lymphatic metastasis

    J. Exp. Med.

    (2005)
  • R. Liersch et al.

    Induced lymphatic sinus hyperplasia in sentinel lymph nodes by VEGF-C as the earliest premetastatic indicator

    Int. J. Oncol.

    (2012)
  • R. Huggenberger et al.

    Stimulation of lymphangiogenesis via VEGFR-3 inhibits chronic skin inflammation

    J. Exp. Med.

    (2010)
  • G. Gundem et al.

    The evolutionary history of lethal metastatic prostate cancer

    Nature

    (2015)
  • M.K. Hong et al.

    Tracking the origins and drivers of subclonal metastatic expansion in prostate cancer

    Nat. Commun.

    (2015)
  • I. Pastushenko et al.

    Blood microvessel density, lymphatic microvessel density and lymphatic invasion in predicting melanoma metastases: systematic review and meta-analysis

    Br. J. Dermatol.

    (2014)
  • Y. Chen et al.

    A meta-analysis of the relationship between lymphatic microvessel density and clinicopathological parameters in breast cancer

    Bull. Cancer

    (2013)
  • M. Yu et al.

    Intratumoral vessel density as prognostic factors in head and neck squamous cell carcinoma: a meta-analysis of literature

    Head Neck

    (2014)
  • H. Clevers

    The cancer stem cell: premises, promises and challenges

    Nat. Med.

    (2011)
  • S. Mendez-Ferrer et al.

    Mesenchymal and haematopoietic stem cells form a unique bone marrow niche

    Nature

    (2010)
  • S.T. Boyle et al.

    The chemokine receptor CCR7 promotes mammary tumorigenesis through amplification of stem-like cells

    Oncogene

    (2015)
  • N. Cabioglu et al.

    CCR7 and CXCR4 as novel biomarkers predicting axillary lymph node metastasis in T1 breast cancer

    Clin. Cancer Res.

    (2005)
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    This review is part of the Advanced Drug Delivery Reviews theme issue on "Insights into heterogeneity in tumor microenvironment for drug development".

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