Week 2 P&I Lectures Flashcards
What is metastasis?
The multi-step process by which tumour cells move from a primary site to colonise a secondary site
What is a neoplasm?
new cellular growth – can either be benign or malignant
What are the 6 biological capabilities acquired during the multistep development of human tumours?
- Sustaining proliferative signalling
- Resisting cell death
- Evading growth suppressors
- Inducing angiogenesis
- Activating invasion and metastasis
- Enabling replicative immortality
What is the acquisition of the 6 biological capabilities for the development of tumours enabled by?
- The development on genomic instability in cancer cells
- Inflammatory state of premalignant and frankly malignant lesions
How does genomic instability lead to the acquisition of the 6 biological capabilities for the development of tumours?
which generates random mutations including chromosomal rearrangement
How does the Inflammatory state of premalignant and frankly malignant lesions lead to the acquisition of the 6 biological capabilities for the development of tumours?
It is driven by cells of the immune system, some of which serve to promote tumour progression.
How is metastasis the leading cause of cancer related death?
- Physical obstruction
- Compromise organ function
- Compete with healthy tissue for nutrients and oxygen
What is the metastatic cascade?
the steps that a tumour needs to take to be able to metastasise and set up in a new location
What are the steps of the metastatic cascade? (6 steps)
- Invasion
- Intravasation
- Transport
- Extravasation
- Colonisation
- Angiogenesis
What are the 7 key characteristics involved in the metastatic cascade?
- Reduced cell-cell adhesion
- Altered cell-substratum adhesion
- Increased motility
- Increased proteolytic ability
- Angiogenic ability
- Ability to intravasate and extravasate
- Ability to proliferate (locally and ectopic sites)
What is the epithelial-mesenchymal transition (EMT)?
The process in which epithelial cells lose their characteristic polarity, disassemble cell-cell junctions and become more migratory
What are stress fibres?
Long strands of actin that are important for movement
What maintains Adherens junction?
E-cadherin
What is the importance of the adherens junction?
It is important in maintaining sheet like structure of epithelial cells
What can cause aberrant E-cadherin expression in tumours? (5 examples)
- somatic mutations
- chromosomal deletions
- silencing of the CDH1 promoter by methylation
- mutations in proteins that interact with E-cadherin
- mutations in transcription factors (Slug, Snail, & Twist) that regulate E-cadherin expression
what can E-cadherin be turned into?
N-cadherin - functionally is very different to E-cadherin
What are integrins?
Transmembrane receptors that bind to and respond to the ECM
What type of signalling can integrins do?
bidirectional signalling – can receive signals from inside the cell and from the ECM
How many possible heterodimers of Integrins are there?
24
What are examples of where integrins are found?
Basal epithelial cells and in focal adhesions in migrating cells
What are focal adhesions?
focal adhesions are little attachment sites. Stress fibres attach to focal adhesions
What is the role of integrins in cancer?
- support oncogenic growth factor receptor (GFR) signalling – can augment it
- cell migration and invasion
- extravasation from blood vessels
- colonisation of metastatic sites
- survival of circulating tumour cells
what is HGF?
Hepatocyte growth factor (or scatter factor)
What are the functions of HGF (in terms of a tumour)?
A mitogen and motogen
What produces HGF in a tumour?
Stromal cells
What does HGF bind to in the tumour?
C-met (a RTK on tumour epithelial cells)
What does activation of C-met lead to?
Increased tyrosine phosphorylation if B-catenin (involved in the structure and binding of e-cadherin)
What is the result of C-met activation?
disrupted E-cadherin-mediated cell-cell junctions
What are morphogens?
signalling molecules that emanate from a restricted region of a tissue and spread away from their source to form a concentration gradient
What does the gradient of a morphogen signal determine?
The pattern of development of the cells
What can HGF/scatter factor induce?
Epithelial cells to dissociate and scatter
What else can have a similar effect to HGF?
EGF
What does the increased proteolytic activity of tumours facilitate?
- Invasion of the ECM at primary and secondary sites
- Digestion of the endothelial BM
- Angiogenesis
- Activate proteases
What is the function of Urokinase plasminogen activator?
Plasminogen –> plasmin
Plasmin activates MMPs and degrades the ECM
What do MMPs do?
MMP2 - degrades type IV collagen (the type found in the BM)
What does Cathepsin K collagenolytic activity do?
Matrix degradation
What is an example of a serine protease?
Urokinase plasminogen activator (uPA)
What is an example of a cysteine protease?
Cathepsin K
What are the different mechanisms of cell motility?
- Mesenchymal migration
- Cluster/ cohort migration
- Ameboid migration
What is mesenchymal migration?
send out stress fibre driven processes to push the membrane out and make new contact through the integrins and the focal adhesions. At the leading edge of the cell there is also proteases being made.
What is cluster/ cohort migration?
Cells at the leading edge drag others along. The cells at the leading edge are making new contacts (integrin mediated) and making proteases at the front to degrade as they move along
How are cells connected in cluster/cohort migration?
by cadherins and gap-junctional communication
What is ameboid migration?
They send processes out in every way until they find the favourable way to move through the ECM
What type of tumour cells tend to move using Ameboid migration?
Lymphoma cells
What are the modes of tumour spread?
- Lymphatic
- Haematogenous
- Transcoelomic
Why is lymphatic spread easier than haematogenous?
- the lymphatic capillaries are thin-walled single layers of endothelial cells - they lack inter-endothelial tight junctions
- They are not covered by smooth muscle
- no basement membrane
What is commonly spread through haematogenous spread?
Sarcomas
What is Transcoelomic spread?
Across the peritoneal cavity
What are the three steps of a tumour moving through a capillary?
- Intravasation
- Transport
- Extravasation
What is intravasation?
The movement of the tumour cells from their primary sites into the capillary
What is extravasation?
The movement of the tumour cells from the vessel to its new site
Why do most tumour cells not survive transport?
- Shear stress of blood flow can destroy them
- Cells must avoid immune detection
- Anoikis
What is an emboli and how can it help the cancer avoid immune detection?
White blood cells and platelets attach to the tumour cells so the body may not recognise it as a threat
What is anoikis?
a form of apoptosis for cells that are meant to be attached to the ECM – if they detach they go through a process to apoptose but since it is slightly different it is called anoikis.
What are the steps of intravasation?
- Attachment
- Degrade BM
- diapedesis
What are selectins?
carbohydrate-binding transmembrane molecules
Where is P-selectin found?
Platelets and endothelial cells
Where is E-selectin found?
endothelial cells
What are E-selectins important for in cancer?
the attachment of cancer cells to endothelium
Where is L-selectin found?
leukocytes
What is the main physiological function of all selectins?
to mediate leukocyte recruitment to sites of inflammation or to lymphoid tissues
What happens when VEGF is transcripted?
- Endothelial cell proliferate, penetrate basement membrane & migrate.
- Formation of invasive endothelial tips (angiogenic sprouting) is followed by stabilisation of some and regression of other vessels.
What happens in angiogenesis in cancer?
Prolonged increase of angiogenic activators which doesn’t turn off and there is no increase of angiogenic inhibitors which means it just continues on.
What is the “seed and soil” theory?
secondary growth of cancer cells (the “seed”) is dependent on the microenvironment of the distant organ (the “soil”)
What is the mechanical theory of metastasis?
- Mechanical factors influence the initial fate of cancer cells after they have left a primary tumour.
- Blood-flow patterns from the primary tumour determine which organ the cells travel to first.
- The relative sizes of cancer cells and capillaries lead to the efficient arrest of most circulating cancer cells in the first capillary bed that they encounter.
What makes up the tumour microenvironment?
various cell types including endothelial cells forming lymph and blood vessels, pericytes, stromal fibroblasts and bone marrow derived cells such as macrophages, neutrophils, mast cells and mesenchymal stem cells
How does the tumour microenvironment contribute to tumour progression?
- secretion of growth factors, cytokines and chemokines
- by the rearrangement of ECM3 preparation of the “soil” at the putative distal site of metastasis
What are M1 macrophages?
Tumoricidal
What do M2 macrophages do?
Promote tumour growth
How do macrophages promote tumour growth?
- chronic inflammation – increased risk of cancer
- immune suppression – recruit immunosuppressive cells
- angiogenesis - secrete angiogenic factors
- invasion/ metastasis - CSF1/EGF paracrine loop