Invasion: Regulation of cell migration Flashcards
(57 cards)
What sort of tissue is involved in 80-90% of cancers?
Epithelial
What is beneath the layer of cells that are tightly attached to each other lying on a basement membrane?
The stroma which consists of blood vessels and supportive tissues
What happens if there is an accumulation of genetic alterations in the layer of cells?
There may be some hyper proliferation which will lead to the formation of a benign tumour
How does a benign tumour progress to a malignant tumour?
Cells de-differentiate (losing their identity and function as epithelial cells), cell-cell contacts disassemble and cells lose polarity
What do malignant cells require to invade the basement membrane?
Cleavage of ECM proteins and increased motility
What can occur after invasion of basement membrane by malignant cells?
Metastasis
How does the movement of metastatic cells differ to normal cells?
They migrate much faster than normal
They don’t attach to neighbours
They move haphazardly in every direction (normal cells show oriented movement
They move all over each other and don’t stop when they should by contact inhibition
What stimuli for cell movement are there?
Organogenesis Morphogenesis Wounding Growth factor/chemoattractants De-differentiation
What happens when a cell is stimulated to move?
It will change its shape to achieve polarity and thus have directionality to the movement
What coordinates the change in shape of a cell that has been stimulated to move?
The cytoskeleton
Why is regulation an important aspect of cell movement?
The cell needs to know when to stop (contact-inhibition motility)
How to move- develop specialised structures to allow movement e.g. focal adhesions, lamellae, folipodia
What is responsible for the important aspect of cell movement of attaching to the substratum?
ECM
What are focal adhesions?
The sites at which the cell attaches to proteins which make the ECM
What does filamentous actin that lies beneath the membrane do?
Hooks focal adhesions to cytoskeletons via integrins
What do integrins do on the intracellular side?
They interact with various cytoskeletal proteins to form a plaque
What are filopodia?
Finger-like protrusions rich in actin. These protrude from the cell to sense where they want to attach and direction of movement
What overlies filopodia?
Vinuncilin- a protein
What are lamellipodia?
Sheet-like protrusions rich in actin filaments that attach to the substratum and when they move back, the structures are called ruffles
In what way is cell movement similar to wall climbing?
First the filopodia extend to find support to hold onto (focal adhesions)
Lamellipodia then attach to the substratum to provide support during movement
Movement of the cell body occurs with retraction of the dorsum and movement forward. This is repeated quickly
Why is control of cell movement required?
To coordinate what is happening in different parts of the cell i.e. where to extend and retract
Also needed to regulate adhesion/release of cell-extracellular matrix receptors to prevent cell breaking
Also needed from the outside to respond to external influences. This involves sensors and directionality
What are the two types of cell motility?
Hapoptatic- Movement with no direction
Chemotactic- movement in which the cell senses a stimulus and moves towards it
How can actin be found?
Small soluble globular monomers (G-actin) or large polymerised filamentous polymer (F-actin)
In terms of F-actin, what will happen if there is a signal like a nutrient source at the other end of the cell to the F-actin?
The F-actin will disassemble and subunits will defuse to the side with the signal. There is reassembly of the subunits at the new site and this facilitates movement
Give some examples of structures that are affected by the arrangement of actin filaments?
Cell cortex has a random gel-like arrangement to provide support to the plasma membrane
Stress fibres have anti-parallel arrangement forming contractile bundles
Filopodium have tight parallel bundles
