Metastisis Flashcards
What are the stages of metastasis?
Invasion - tumour spread to blood/lymph
Intravasation - tumour cells in the blood/lymph
Arrest in micro vessels of an organ
Extravasation - tumour cells leave blood/lymph at distant sites and colonise. Survival after this is the limiting step.
Proliferation in new organ
What static models can be used to study metastasis?
Animal models - spontaneous (induce a tumour, see if metastasis) or experimental (inject cells into tail vein, see where they go)
Cell culture - see if cells invade/form colonies/display metastatic properties through a porous membrane. Can also do motility assays
What are the assumptions in in vitro models of metastasis?
Metastatic cells have unique properties not in the malignant cell - isn’t clear that metastatic cells are invasive; model may not be relevant - malignant breast cells don’t invade collagen gels whilst normal ones do. Also, is unclear if malignant cells are abnormally motile.
What are dynamic experimental models that can be used to study metastasis?
Intravital imaging - detect fluorescence and use it to study location, motility, adhesion and interactions off cells over time.
What has been observed through intravital imaging?
Macrophages and tumour cells and endothelial cells form a structure that p umps tumour cells into the blood stream
Tumour cells get into structures already present and use as a ‘highway’ e.g. muscle and nerve fibres
What is the Fidler classic heterogeneity experiment?
Plated one cell per well and grew up into a colony. Each was injected into a mouse and metastatic potential was observed. The results suggested that only some of the cells in the primary tumour had strong metastatic potential. Fidler suggested that only a few cells in the primary tumour could metastasise but all the cells in the metastatic tumour could
What is the problem with the Fidler conclusions?
When the Fidler experiment is run using cells from the metastatic tumour, get the same rates of metastasis as with cells from the primary tumour.
What is the Kerbel clonality experiment?
Create primary tumours with a mass of cells, each market with a distinct retrovirus insert. Found that cells required to create the primary tumour (dominant clone) are generally those required for metastasis (are found in the metastases)
What is Bernards and Weinberg profiling argument?
That there are no genes and genetic changes that are specific for metastasis - suggested it occurs by ‘accident’ - chance of a cell escaping into the vasculature is based on the tumour position not the genetics.
What is known about the sequence heterogeneity of metastasis?
Multi genome sequencing was done of cells in primary and metastatic tumours - found regions of the primary tumour were similar to the metastasis and that diversity in the primary tumour predicts diversity in the metastasis. When looking at driver mutations in pancreatic cancer found that there was little difference between primary and metastasis. When looking in renal carcinoma found that many mutations are sub clonal but all were in the same pathway.
A crispr screen showed that many of the genes lost in tumour progression were the same as those needed to become metastatic.
What was the experiment done by van der Weyden to find genes involved in metastasis?
Looked in a collection of knockout mice - looked for more or less metastasis into the lungs. Found that genes that affected metastasis were involved in the immune system. Found that genes that when deleted resulted in higher NK and effector T cells in the lungs had less metastasis (more tumour cells were killed)
How can cancer be monitored with CTC and ctDNA
Circulating tumour cells and circulating tumour DNA. Can monitor fluctuation and predict relapse and look for progression of disease. ctDNA is much more sensitive - but need to know mutational landscape so primers can be designed for deep sequencing of the blood
