Cancer MetastasisCancer Metastasis

Lymphatic SpreadLymphatic Spread

MetastasisMetastasis

‘‘Metastases’ are tumour implants discontinuous with the primary Metastases’ are tumour implants discontinuous with the primary tumourtumour

Approximately 30% of newly diagnosed patients with solid tumours Approximately 30% of newly diagnosed patients with solid tumours present with metastases present with metastases (1)(1)

They are the major cause of cancer-related morbidity and mortalityThey are the major cause of cancer-related morbidity and mortality

Pathways of SpreadPathways of Spread (1)

(1) Seeding of the body cavities and surfaces(1) Seeding of the body cavities and surfaces When a malignant neoplasm penetrates into a natural ‘open field’ eg. When a malignant neoplasm penetrates into a natural ‘open field’ eg.

peritoneal cavityperitoneal cavity

(2) Lymphatic Spread(2) Lymphatic Spread Most common pathway for the initial dissemination of carcinomasMost common pathway for the initial dissemination of carcinomas Tends to follow the natural routes of lymphatic drainageTends to follow the natural routes of lymphatic drainage

(3) Haematogenous Spread(3) Haematogenous Spread Typical of sarcomasTypical of sarcomas More readily via venous (than arterial) systemMore readily via venous (than arterial) system

Invasion & MetastasisInvasion & Metastasis

For tumour cells to break loose from the primary mass, enter the For tumour cells to break loose from the primary mass, enter the blood/lymph vessels and produce a secondary growth they must blood/lymph vessels and produce a secondary growth they must interact with the extracellular matrix (ECM) at several stages:interact with the extracellular matrix (ECM) at several stages:

Breach the underlying basement membraneBreach the underlying basement membrane Transverse the interstitial connective tissueTransverse the interstitial connective tissue Penetrate the vascular basement membranePenetrate the vascular basement membrane

Invasion of the ECM is an active process which involves:Invasion of the ECM is an active process which involves: Detachment of tumour cells from each otherDetachment of tumour cells from each other Attachment to matrix componentsAttachment to matrix components Degradation of the ECMDegradation of the ECM Migration of tumour cellsMigration of tumour cells

Invasion & Metastasis cont.Invasion & Metastasis cont.

1.1. Detachment of Tumour CellsDetachment of Tumour Cells1.1. Normal cells are adhered to one another via transmembrane Normal cells are adhered to one another via transmembrane

glycoproteins (E-cadherins)glycoproteins (E-cadherins)

2.2. Downregulation of E-cadherin expression in adenocarcinoma of the Downregulation of E-cadherin expression in adenocarcinoma of the coloncolon

3.3. Decreased ability for adherence and facilitation of detachment from the Decreased ability for adherence and facilitation of detachment from the primary tumourprimary tumour

2.2. Attachment of Matrix ComponentsAttachment of Matrix Components1.1. Expression of integrins by tumour cells serve as receptors for ECM Expression of integrins by tumour cells serve as receptors for ECM

componentscomponents

2.2. Receptor-mediated attachment of tumour cells to laminin & fibronectinReceptor-mediated attachment of tumour cells to laminin & fibronectin

3.3. Increased density of receptors = increased invasivenessIncreased density of receptors = increased invasiveness

Invasion & Metastasis cont.Invasion & Metastasis cont.

3.3. Degradation of ECMDegradation of ECM1.1. Secretion of proteolytic enzymes by tumour cellsSecretion of proteolytic enzymes by tumour cells

2.2. Induction of host cell protease synthesis (eg. type IV collagenase)Induction of host cell protease synthesis (eg. type IV collagenase)

3.3. Cleavage of type IV collagen of the epithelial & vascular basement Cleavage of type IV collagen of the epithelial & vascular basement membranesmembranes

4.4. Migration of Tumour CellsMigration of Tumour Cells1.1. Cleavage products of matrix components have growth-promoting, Cleavage products of matrix components have growth-promoting,

angiogeneic and chemotactic activitiesangiogeneic and chemotactic activities

2.2. Promotion of migration of tumour cells through loosened ECM, and Promotion of migration of tumour cells through loosened ECM, and through the degraded basement membranethrough the degraded basement membrane

Lymph Node MetastasisLymph Node Metastasis

Motility towards lymphatic capillaries aided by lower interstitial fluid Motility towards lymphatic capillaries aided by lower interstitial fluid pressures within the ECM, than in the tumour ~ ‘tide of fluid’pressures within the ECM, than in the tumour ~ ‘tide of fluid’ (2)(2)

Having reached the lymphatic capillaries, tumour cells move along external Having reached the lymphatic capillaries, tumour cells move along external surface of the endothelium and invade into the lumen via interendothelial surface of the endothelium and invade into the lumen via interendothelial gapsgaps (2)(2)

The composition of lymphatic vessels makes it easy for fluid, particles and The composition of lymphatic vessels makes it easy for fluid, particles and cells to pass into the vessels cells to pass into the vessels (3)(3)

Having gained access to the capillaries, the tumour cells embolise singly or Having gained access to the capillaries, the tumour cells embolise singly or in clusters towards local lymph nodesin clusters towards local lymph nodes

Some cells do not reach the nodes, but adhere to the lymphatic endothelium Some cells do not reach the nodes, but adhere to the lymphatic endothelium and cause ‘in transit’ metastases and cause ‘in transit’ metastases (2)(2)

Tumour cells enter the subcapsular sinus of the lymph node through the Tumour cells enter the subcapsular sinus of the lymph node through the afferent lymphatics and may either:afferent lymphatics and may either:

Invade the cortex of the nodeInvade the cortex of the node Bypass the node via lymphpaticovenous connectionsBypass the node via lymphpaticovenous connections Travel directly into the efferent lymphatics and spread to further local nodesTravel directly into the efferent lymphatics and spread to further local nodes

LymphangiongenesisLymphangiongenesis

Until recently lymphatic metastasis was believed to be a ‘passive process’ – it Until recently lymphatic metastasis was believed to be a ‘passive process’ – it has now become apparent that lymphangiogenesis can contribute actively to has now become apparent that lymphangiogenesis can contribute actively to tumour metastasistumour metastasis (4)(4)

Studies describing lymphatic growth and development did not emerge until the Studies describing lymphatic growth and development did not emerge until the late 1990s due to a lack of defined lymphatic endothelial markers late 1990s due to a lack of defined lymphatic endothelial markers (5)(5)

Widely established lymphatic endothelial markers include:Widely established lymphatic endothelial markers include: Vascular Endothelial Growth Factor-3 (VEGFR-3)– the first lymphangiogenic growth Vascular Endothelial Growth Factor-3 (VEGFR-3)– the first lymphangiogenic growth

factor identifiedfactor identified Podoplanin Podoplanin LYVE-1LYVE-1 Prox-1Prox-1 FOXC2FOXC2

Current knowledge does not yet provide a full understanding of their exact role Current knowledge does not yet provide a full understanding of their exact role in lymphangiogenesis.in lymphangiogenesis.

Lymphangiogenesis cont.Lymphangiogenesis cont.

While the mechanisms of tumour lymphangiogenesis are not fully understood While the mechanisms of tumour lymphangiogenesis are not fully understood or defined, multiple studies have established VEGF-C & -D as the main or defined, multiple studies have established VEGF-C & -D as the main regulator of lymphangiogenesis regulator of lymphangiogenesis (6, 7, 8, 9, 10)(6, 7, 8, 9, 10)

Over-expression of VEGF-C in animal tumour models has demonstrated strong Over-expression of VEGF-C in animal tumour models has demonstrated strong increases in lymphatic vessel formation and significant promotion of lymph increases in lymphatic vessel formation and significant promotion of lymph node metastases node metastases (7, 9).(7, 9).

Recently VEGF-C has also been shown to promote further metastasis from Recently VEGF-C has also been shown to promote further metastasis from

regional to distal lymph nodes and organs regional to distal lymph nodes and organs (10)(10)

It is proposed that tumour lymphangiogenesis increases the lymphatic vascular It is proposed that tumour lymphangiogenesis increases the lymphatic vascular area within or close to the tumour, and therefore increases contact between area within or close to the tumour, and therefore increases contact between tumour cells and the lymphatics ~ facilitating entry of malignant cells into the tumour cells and the lymphatics ~ facilitating entry of malignant cells into the lymphatic system, thereby promoting metastatic spread lymphatic system, thereby promoting metastatic spread (5).(5).

Colorectal cancer data is conflicting in human models, but it seems likely that Colorectal cancer data is conflicting in human models, but it seems likely that both VEGF-C/-D contribute to the disease course both VEGF-C/-D contribute to the disease course (5)(5)

Therapeutic StrategiesTherapeutic Strategies Anti-lymphangiogenic therapy is an important area for future research ~ Anti-lymphangiogenic therapy is an important area for future research ~

assuming that restriction of lymphatic vessel growth associated with tumours assuming that restriction of lymphatic vessel growth associated with tumours will prevent lymph node metastaseswill prevent lymph node metastases

Lymph node metastases are a key event in colorectal tumour progression;Lymph node metastases are a key event in colorectal tumour progression; With lymph node metastases 5-year survival is reduced from 90% to 68%With lymph node metastases 5-year survival is reduced from 90% to 68%

VEGF-C/-D induced stimulation of VEGFR-3 represents a promising target VEGF-C/-D induced stimulation of VEGFR-3 represents a promising target for anti-lymphangiogenic therapyfor anti-lymphangiogenic therapy Blocking extracellular ligand-receptor interactions with neutralising monoclonal Blocking extracellular ligand-receptor interactions with neutralising monoclonal

antibodies to either receptors or ligands ~ demonstrated in some animal modelsantibodies to either receptors or ligands ~ demonstrated in some animal models Soluble VEGFR-3-fc fusion protein has also been shown to inhibit Soluble VEGFR-3-fc fusion protein has also been shown to inhibit

lymphangiogenesis lymphangiogenesis (5)(5)

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(3) Swartz, MA. & Skobe, M. (2001). Lymphatic Function, Lymphangiogenesis, and Cancer (3) Swartz, MA. & Skobe, M. (2001). Lymphatic Function, Lymphangiogenesis, and Cancer Metastasis. Metastasis. Microscopy Research and TechniqueMicroscopy Research and Technique , , 5555:92-99.:92-99.

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(6) Yoo, PS. et al (2007). A Novel In Vitro Model of Lymphatic Metastasis from Colorectal (6) Yoo, PS. et al (2007). A Novel In Vitro Model of Lymphatic Metastasis from Colorectal CancerCancer. Journal of Surgical Research, ‘article in press’.. Journal of Surgical Research, ‘article in press’.

(7) Kawakami, M. et al (2005). Vascular Endothelial Growth Factor C Promotes Lymph Node (7) Kawakami, M. et al (2005). Vascular Endothelial Growth Factor C Promotes Lymph Node Metastasis in a Rectal Cancer Orthotopic Model. Metastasis in a Rectal Cancer Orthotopic Model. Surg TodaySurg Today, , 3535: 131-138.: 131-138.

(8) Akagi, K. et al (2000). Vascular endothelial growth factor C (VEGF-C) expression in human (8) Akagi, K. et al (2000). Vascular endothelial growth factor C (VEGF-C) expression in human colorectal cancer tissues. colorectal cancer tissues. Br J CancerBr J Cancer, , 8383: 887-891.: 887-891.

(9) Skobe, M. et al (2001). Induction of tumour lymphangiogenesis by VEGF-C promotes(9) Skobe, M. et al (2001). Induction of tumour lymphangiogenesis by VEGF-C promotes breast breast cancer metastasis. cancer metastasis. Nat MedNat Med, , 77: 192-198.: 192-198.

(10) Hirakawa, S. et al (2007). VEGF-C-induced lymphangiogenesis in sentinel lymph nodes (10) Hirakawa, S. et al (2007). VEGF-C-induced lymphangiogenesis in sentinel lymph nodes promotes tumour metastasis to distant sites. promotes tumour metastasis to distant sites. BloodBlood, , 109109: 1010-1017.: 1010-1017.