Behaviour of Tumours Flashcards
What is invasion of tumours?
Tumour invades adjacent normal tissue and starts to destroy it
What is metastasis of tumours?
Spreads from site of origin to a distant site and establishes a new tumour there
What causes the progression from local disease to systemic disease?
Invasion –> metastasis
How are epithelial cells normally connected?
Tightly connected, polarised and tethered to each other (unable to move)
How are mesenchymal cells normally connected?
Loosely connected, able to migrate
What is the epithelial-mesenchymal transition?
In cancer, epithelial cells gain MESENCHYMAL properties and can invade and migrate
How do epithelial cells gain mesenchymal properties?
- Increased motility
- Decreased adhesion
- Production of proteolytic enzymes
- Mechanical pressure
What is an example of a cell-to-cell adhesion molecule (CAM)?
Cadherins: important in the formation of adherens junctions to bind cells with each other.
What can a mutation in E-cadherin in the tumour lead to?
reduced cell to cell adhesion
What is an example of a cell to matrix adhesion molecule and receptor?
Integrin: the principal receptors used by animal cells to bind to the extracellular matrix.
What can changes in integrin expression (as seen in tumours) lead to?
Decreased cell-matrix adhesion
What is the most important proteolytic enzyme in neoplastic invasion?
Matrix metalloproteinases
What are matrix metalloproteinases secreted by?
Malignant neoplastic cells
What are matrix metalloproteinases able to digest ?
Able to digest surrounding connective tissue
What are the 3 major types of matrix metalloproteinases?
- Interstitial collagenases
- Gelatinases
- Stromelysins
What do interstitial collagenases degrade?
Type I, II and III collagen
What do gelatinases degrade?
Type IV collagen and gelatin
What do stromelysins degrade?
Type IV collagen and proteoglycans
The balance of proteolytic enzymes in normal vs cancer?
- Normal: balance between tissue inhibitors of metalloproteinases and matrix metalloproteinases
- Cancer: more matrix metalloproteinases so cancer favours extracellular matrix breakdown
Uncontrolled proliferation and invasion can lead to a mass. How can a mass affect vessels?
Mass can occlude vessels or put pressure on tissues –> clinical effects on patients
Malignant neoplasms invade along the ‘path of least resistance’. What does this mean?
- Most commonly along blood vessels or nerves
- Cartilage and bone are extremely resistant to neoplastic invasion
Describe the tumour mass of a secondary tumour (metastasis) compared to the primary tumour
Often tumour mass of secondary tumours exceeds that of the primary lesion. May be presenting clinical feature:
- Bone lesions
- Palpable lymph nodes
Metastatic sequence:
- Detachment and invasion (cancer cells detach from primary tumour)
- loss of surface adhesion molecules and imbalance of matrix metalloproteinases
- ECM is broken down
- Neoplastic cells are motile
- loss of surface adhesion molecules and imbalance of matrix metalloproteinases
- Intravasation
- The invasion of cancer cells through the basement membrane
- Survival against host defences
- Often have a reduced expression of the MHC complex on their surfaces
- Adherence and extravasation
- Adhere to lining of blood vessel at the distant site
- Movement of cells out of a blood vessel into tissue during metastasis
- Angiogenesis
- Ability to promote formation of new blood vessels
What are the 4 main routes of metastasis?
- Lymphatics
- Haematogenous (blood)
- Transcoelomic
- Implantation
How does metastasis occur via lymphatics?
Form secondary tumours in lymph nodes
What is the lymphatic route most common initially for?
Carcinomas