Lecture 19: Introduction to metastasis Flashcards
What is metastasis
spread of tumour cells from a primary site to set up secondary tumours in a distant location
Main cause of cancer death (90%)
What cancers rarely metastasise?
Basal cell carcinoma
Brain tumours
Leukaemia
What are the different stages of metastasis in breast cancer
Stage 1: early (2cm or smaller) - 99% survive >5 years after diagnosis
Stage 2: 90% survive >5 years after diagnosis
Stage 3: Locally advanced - 60% survive >5 years after diagnosis
Stage 4: Advanced, secondary or metastatic - 15% survive >5 years after diagnosis
What are the 7 stages of metastasis?
- Detachment
- Intravasation
- Transport through circulation
- Arrest
- Extravasation
- Formation of micro-metastasis
- Colonisation
How do we study metastasis?
In-vitro
1. Transwell assay / Boyden chamber assay
a. chemokinesis
b. chemoinvasion
2. Organoids
a. tiny, self-organised in vitro tissue culture mimicking in vivo organ
b. e.g., brain, intestine, liver, stomach, lung, tumouroids
c. generated using stem cells
In-vivo
1. Chick chorioallantoic membrane (CAM) assay
a. CAM - highly vascularized
b. uses chick egg
2. Experimental metastasis assay
a. intravenous injection
b. circulation, arrest, extravasation, colonisation
3. Spontaneous metastasis assay
a. subcutaneous injection, orthotopic injection
4. Transgenic mice (GEMMs)
a. oncogenes over-expressed, tumour suppressor genes silenced
b. spontaneous tumour dev as a result
c. E.g., breast cancer models - MMTV-Her2 and MMTV-PyMT mice
How do metastatic cells arise?
Fidler’s experiment with B16 melanoma cells - suggested a small metastatic sub-population of cells in a primary tumour that can be selected for
B16F0 = poor metastasis
B16F1 = low metastatic ability
B16F10 = highly metastatic
Metastatic cells show a very different gene expression
How is gene expression linked to prognosis of metastasis?
Gene expression profiling - genomic test to predict cancer prognosis
Mammaprint (AGENDIA)
1. 70 gene poor prognosis signature
2. Analyses 70 most important genes
3. Classifies patient as low to high risk of metastasis development in the
first 10 years after diagnosis
What are the common metastasis sites of some primary tumours?
prostate > bone
Breast > bone, brain, adrenal, lung, liver
Gastrointestinal > liver
Melanoma (skin) > liver, brain, bowel
Melanoma (eye) > liver
What is the haemodynamic theory?
Frequency of metastases in different organis is primaryily determined by the numbers of cancer cells delivered to them
E.g.,
Gastro-intestinal tumours first pass the liver
Breast tumours flow to lungs, then to bones, brain etc via the heart
What is the seed and soil theory?
Metastasis occurs at sites where the local microenvironemtn is favourable.
Cancer cells: seed Tissue: soil
Majority of cells dont adapt to the new tissue and will never form macrometastatsis
Cancer cells will adapt uniquely depending on the new site, e.g., bone vs adapting to lungs
What is the premetastatic niche
Sites outside of the primary tumour which are not tumourous may be primed for colonisation
E.g., bone marrow derived cells may be recruited by primary tumours to colonise a pre-metastatic niche in a distant organ, prior to their arrival
How is the premetastatic niche prepared?
EXPERIMENTALLY
1. mice irradiated to kill of their bone marrow cells - which were replaced by GFP-labelled bone marrow cells
2. mice injected in the skin with RFP-labelled melanoma carcinoma cells - spontaneous metastasis assay
3. GFP labelled bone marrow cells appear in the lungs 2 weeks after injection of tumour cells, before the arrival of any tumour cells in the lungs
4. RFP labelled tumour cells arrived 9 days later
What is the preparations of the premetastatic niche?
primary cancer cells send signals to activate normal fibroblasts in the future metastatic site (lungs) to make fibronectin
Fibronectin: binds cells to ECM
Creating preferred environment fo bone marrow cells to adhere
Exosomes circulate through the body, and interact with local target sites due to surface specific integrins
What is the preparations of the premetastatic niche?
primary cancer cells send signals to activate normal fibroblasts in the future metastatic site (lungs) to make fibronectin
Fibronectin: binds cells to ECM
Creating preferred environment fo bone marrow cells to adhere
Exosomes circulate through the body, and interact with local target sites due to surface specific integrins
