Invasion and Metastasis Flashcards
Define invasion
Ability of cells to break through normal barriers e.g. basement membrane into the surrounding tissue
How to neoplastic cells invade and spread?
Detachment of neoplastic cells from each other (through down-regulation of cadherin expression)
Attachment to ECM via specific receptors
Degradation of the ECM through secretion of collagenases and proteases
Locomotion through the ECM via secretion of motility factors
Cells then spread via vascular system, lymphatics or transcoelomic
How is cell adhesion altered?
Reduced expression and alteration of cadherins. Cadherins are Ca2+ dependent glycoproteins on the cell membrane that interact between cells and maintain cell polarity and structure. Reduction allows cells to move apart
Reduced expression of intergins. Cell surefacec glycoproteins that anchor the cell to the basement membrane. Modifies contact between the malignance cell and stroma, allowing movement.
How doe saltered enzyme synthesis promote metastasis?
Different enzymes can modify stroma allowing cells to break through the basement membrane and spread. e.g. MMPs, gelatinases, stromelysins
Malignant cells produce factors that stimulate stroma (fibroblasts) to synthesise more enzymes.
Remodelling determined by levels of MMPs and TIMPs (tissue inhibitor of MMPs). Can inhibit TIMP activity to alter balance of remodelling
What is metastasis?
Ability of malignant cells to invade lymphatics, blood vessels and cavities, and spread to distant sites.
Cells must be able to invade from channels and grow at a distant site.
What are the steps of metastasis?
Invade basement membrane
Pass through ECM
Intravasation
Immune interaction
Platelet adhesion
Adhesion to endothelium
Extravasation
Angiogenesis
Why don’t all malignant cells metastasise?
Cells may invade and circulate but distal environment may not be appropriate for growth due to:
Incorrect receptors
Metabolic factors
Failure of angiogenesis
What is angiogenesis
Formation of small new vessels needed to maintain the growth of cells.
Produced in response to growth factors.
Name 3 growth factors that promote angiogenesis
VEGF
Basic fibroblast growth factor
Angiopoietins
Anti angiogenic factors: thrombospondin, angiostatin, endostatin
Define primary and secondary metastasis
Primary: site where the malignant neoplasm arises
Secondary: carcioma that has spread to another organ
What are the routes of metastatic spread?
Lymphatics - spread via draining lymphatics to lymph nodes
Vascular - spread by veins draining the lesion. GI tumours metastasise to the liver via portal vein. Cells that enter systemic veins form mets in the lung, BM, brain and adrenals.
Transcoelomic - tumours in the abdomincal cavity or thorax can spread across coelomic spaces - peritoneal or pleural cavities.
Common sites of vascular spread
Liver
Lung
Bone
Brain
Cancers which commonly spread to the lung via the blood
Sarcomas - osteosarcoma
Carcinomas - breast, stomach, large intestine
Kidney
Testis
Cancers which commonly spread to the liver
GI carcinomas via portal vein
Bronchial carcinoma
Breast carcinoma
Cancers which commonly spread to the bone
Bronchial carcinoma
Breast carcinoma
Thyroid carcinoma
Renal carcinoma
All cause the destruction of bone