Invasion and Metastasis Flashcards
What is TGF-beta?
A potent tumour promoter
What does TGF-beta promote?
Intravasation
Extravasation
Invasion
Metastatic colonisation
What is metastasis?
Where a tumour cell leaves the primary tumour and travels to a distant site via the blood stream and establishes a secondary tumour
How many cancer related mortalities does metastasis account for?
~90%
What are the common distal sites for breast adenocarcinoma?
Bone
Brain
Adrenal
What are the two theories for organ selectivity?
Mechanistic theory
Seed and soil theory
What is the mechanistic theory?
Determined by the pattern of blood flow
What is the seed and soil theory?
Provision of a fertile environment which compatible tumour cells could grow
What are the determining factors of metastasis?
Appropriate growth factors or extracellular matrix environment
Compatible adhesion sites on the endothelial lumen surface
Selective chemotaxis - soluble attraction to bring the tumour in
What are the 5 steps of metastasis?
1) invasion and infiltration of surrounding host tissue
2) release of neoplastic cells (single cells or small clumps) into the circulation
3) Survival in the circulation
4) Arrest in the capillary bed of distant organs
5) Penetration of the lymphatic or blood vessel walls followed by growth of disseminated tumour cells
How are the blood vessels in tumours different from normal blood vessels?
They have different adhesion junctions so they are often leaky, allowing tumour cells to enter the blood stream easier
What is intravasation?
Leaving the tumour tissue into the blood stream
What is extravasation?
Moving from the blood stream into the tissue
Why is the liver and bones easier to migrate to?
They have a natural fenestrated epithelium, meaning they have natural gaps for the lymphocytes to enter and leave the bone marrow and liver
What are the 3 phases of invasion?
1) Translocation of cells across extracellular matrix barriers
2) Lysis of matrix proteins by specific proteinases
3) Cell migration
How do cells respond to a chemotactic que?
Sticks out an lallelopodium
Makes new attachments to pull itself towards the lallepodium
Lets go of the back so it can move forward without stretching
What is a transwell invasion system?
Mimic the basement membrane to see which tumour cells get through
Put the tumour on top of the basement membrane and add a chemotactic que at the bottom to see if they can get through
How do you mimic the basement membrane?
Produce a fibrillar collagen and matrigel mix
What is incucyte zoom?
Real-time imaging of migration and invasion
How much does incucyte zoom cost?
£120,000
In breast cancer, what gene is required for invasion?
CSF2
In terms of CSF2, what is the issue in breast cancer?
Patients are given CSF2 to prevent other side effects but is evoking metastasis
How have assays been developed to investigate intravasation and extravasation?
Put an endothelial layer underneath the basement membrane
What is amoeboid invasion?
Move through the membrane, not by eating it, by pushing their way through the fibres of collagen
What is mesenchymal invasion?
Going through the extracellular matrix
What is matrix degrading enzymes required for?
Controlled degradation of components of the extracellular matrix
What are proteases are involved in degradation the ECM classified into?
serine-, cysteine-, aspartyl-, and metalloproteases
How many members of matrix metalloproteases are there?
16
How many subgroups of matrix metalloproteases are there?
4
What matrix metalloproteases are soluble and secreted?
Collagenase
Gelatinase
Stromelysins
What matrix metalloproteases are membrane-type? And what are these?
Invadapodia
They are anchored into the plasma membrane
What matrix metalloproteases cleave type IV collagen of the basement membrane?
MMP2 and MMP9
What is collective invasion?
Tumours made up of tumour cells and other cells and move together
Name a cancer type which fibroblasts are important for invasion?
Squamous cell carcinoma
How do squamous cell carcinomas migrate?
Via collective invasion
What GTPase effects tumour cell migration and how?
RhoGTPases
Through changing their cytoskeletal structure
Describe lamellipodia
High Rac activity
Polymerisation of the actin cytoskeleton and forms the F-actin which pushes the membrane forward
Describe filopodia
High CDC42 activity
F-actin filaments make fine protutions in the membrane and this’ll push the activity
Describe invadopia
High CDC42 activity
Still has filopodia
Positions the matrix metalloproteases at the end of the membrane and degrades the matrix
Describe membrane blebs
High RhoA activity
Pushes your way through the fibres
Pulls the membrane apart and allows the interstitial pressure to push the membrane up
What is EMT?
Changing from a more epithelial phenotype to a more mesenchymal phenotype
How does EMT occur?
Dissolve the hemidesmosomes which epithelial cells are attached to the plasma membrane by
Downregulate tight junctions and adhesion junctions such as E cadherin - switch to N cadherin
Lose basal polarity through downregulating polarity proteins including Crumbs, PATJ and LGL
Increase plasticity
Increase MMP
How is E cadherin downregulated?
Upregulate transcriptional repressors, ZEB, Snail and/or slug and Twist1 -> bind to E cadherin promoter -> downregulate it
How is ZED1, TWIST and SNAIL upregulated?
TGF-beta activates SMAD -> SMAD translocates to the nucleus -> SMAD binds to their promoters -> increased transcription
What signalling pathway does cytokine receptors stimulate?
JAK/STAT
How does WNT signalling promoter migration?
Produce beta-catenin -> increased EMT
How do integrins induce EMT?
Through interacting with the ECM
How does hypoxia induce EMT?
Induce HIF-1alpha -> interact with Notch intracellular domain -> upregulate TGF-beta expression -> SMAD pathway
How do tumour-associated fibroblasts induce EMT?
Make TGF-beta and IL-6 -> push EMT forward
How do tumour-associated macrophages induce EMT?
Make TGF-beta and cytokines
How do myeloid derived suppressor cells induce EMT?
make TGF-beta and EGF
Effect of CD4 T cells on migration?
Promote EMT
Effect of CD8 T cells on migration?
block EMT but tumour cells can manipulate them to induce EMT through changing their behaviour
How do Tregs induce EMT?
Produce TGF-beta
Why is the point nature of tumour cells important in migration?
When they get into the blood stream, important in making sure they can withstand the severity of the blood flow
Why is EMT important?
Promotes a cancer stem cell-like phenotype
Produces survival signals to avoid anoikis
Increasing drug resistance
How does EMT modulate the immune response?
Downregulate HLA molecules so it doesn’t present as many antigens
Increased checkpoint molecules
Promote Treg differentiation instead of CD4’s and CD8’s
M2 phenotype macrophages (tumour-promoting phenotype)
What part of EMT modules the immune response?
The production of TGF-beta
How can macrophages be tumour-promoting?
They guide tumour cells in the process of intravasation since they naturally move in and out of the circulatory and lymphatic system
How do tumour cells interact with platelets?
Via platelet adhesion receptors and their ligands
How do tumour cells induce platelet activation?
Through tumour-induced platelet aggregation
What effect does activated platelets and platelet microparticles have on tumour cells?
Produce growth factors such as VEGF, insulin-like growth factor, platelet derived growth factor and TGF-beta1
Promotes angiogenesis and tumour growth
Why do platelets express so much TGF-beta?
Since TGF-beta is involved in wound healing
What stages of metastasis do platelets aid?
Intravasation and extravasation
How do platelets help tumour cells move throughout the blood stream?
Single tumour cells can roll on the endothelium with the aid of platelet P-selectin to prevent sheer force damage
Platelet tumour aggregates circulate in the blood stream with the tumour cells shielded by platelets, which release growth factors to inhibit NK cells
How do platelets aid with extravasation?
Due to clot formation abilities
TGF-beta helps paracellular extravasation
How does TGF-beta promote metastasis to the lung from a breast tumour?
Upregulates ANGPTL4 -> loosens epithelial junctions in the lung endothelium
Induces Id1 -> drives tumour reinitiation
How does TGF-beta promote metastasis to the bone from a breast tumour?
TGF-beta activates osteoclasts -> osteoclasts degrade the bone matrix -> releases more TGF-beta -> stimulate PTHrP and IL-11 -> stimulate oestblasts -> release RANKL to mobilise osteoclasts
What can ID-1 induce?
Tumour reinitiation
Stem cell-like phenotype
Why to osteoclasts need to be activated for metastasis?
there is no room in the bond for tumours to metastasis too unless some is eaten
How do tumours make microenvironments before they migrate?
They produce exosomes which bud off and are full of proteases, microRNA etc. to a pre-metastatic niche and release growth factors, chemokines etc.
What kind of niche are glioblastoma cells in?
Perivascular niche
What is a perivascular niche?
Where the tumour cells attach at the top of the epithelium
What is a ad hoc niche?
Coordination between the tumour cells, myeloid cells and fibroblasts
Make moelcules which will make a supportive extracellular environment and provides survival signals for the tumour cells
What is a native stem cell niche?
the normal stem cell provides a stem cell environment for the cancer cell to invade
How are cadherin junctions loosened in the lung?
Exosomes release GLIO105 which downregulates ZO1
Release of chemokines will produce more chemokines and activate monocytes which will stimulate VEGF to losen the junctions
How do alveloar cells support the production of the pre-metastatic niche in the lungs?
They produce chemokines which release neutrophils - act as a chemoattractant signal
How long can clinical dormancy last in breast cancer?
10 years
How are dormant cells reactivated?
Growth factor stimulation
Activation of self renewal stem cell transcription factors
MET
What are three approaches being investigated for dormant cells?
Keep them dormant since they aren’t doing any harm
Turn the dormant cells on so they can be targeted for chemotherapy
Kill the dormant cells
What is the issue with keeping the dormant cells?
They could eventually stop being dormant
What is the issue with turning the dormant cells on?
They could be more aggressive so chemotherapy doesn’t work
What is the issue with killing dormant cells?
Do not know what is keeping them dormant, need to know this to be able to target it
What is being diagnosed with lymph node positive associated with?
Worse prognosis
Indicates the tumour cells are moving
Why do most cells spread via the lymphatic instead of the blood?
The lymphatics has a fenestrated membrane so it is easier for the tumour cells
How can tumour cells and their associated macrophages manipulate the lymph system?
They can induce lymph angiogenesis (enlargement of the lymph nodes) - those which are closest to the tumour are enlarged
Could allow them to access the circulatory system
