Liquid Biopsies Flashcards
What is a liquid biopsy?
Sampling and analysis of non-solid biological tissue
What does amniotic analysis test for?
Paternity
Sex
Chromosomal abnormalities
Why is blood really good as a liquid biopsy?
Fragments from apoptotic cells make their way into the blood on their way to being discarded
What can blood liquid biopsies test for?
Circulating endothelial cells Circulating tumour cells Disseminated tumor cells Tumor educated platelets Cell free nucleotides Metabolites Extracellular microvesicles
What type of information can you get from a liquid biopsy?
Germline (hereditary) and somatic information
How do you extract a liquid biopsy?
By taking 10mL blood by vernipuncture (4-5mL plasma)
What do the biopsy tubes need to prevent?
Blood clots
Genomic DNA release
Haemolysis
What do the EDTA and citrate tubes contain?
Anticoagulant to prevent clotting
What are the properties of cell-free DNA tubes?
Contain a stabiliser to prevent release of gDNA from white blood and haemolysis of red blood cells
What are circulating tumour cells?
Cells that have detached from a tumour and travelled through the bloodstream to other parts of the body
How often do you find circulating tumour cells?
Rarely
1-10 in 1mL of blood
How can you isolate circulating tumour cells?
Antibodies of cell surface markers
Size (they’re a little bit bigger than other cells)
What can you use to analyse circulating tumour cells?
NGS, FISH, flow cytometry RTqPCR or in vivo/in vitro culture
What does circulating tumour cell analysis give information about?
The tumour they’ve detached from
What concentration is circulating tumour DNA present in?
1-50ng DNA/mL plasma
What does circulating tumour DNA provide information of?
Current genetic makeup
80-95% specificity and 60-85% sensitivity
How do you isolate the circulating DNA?
Transfer the supernatant to a clean polypropylene tube and freeze it
Then isolate using magnetic beads cellulose or silica based systems
What are the advantages of a liquid biopsy?
Low invasiveness
Higher patient compliance
Higher cost/effectiveness
Allow repeated access and multiple sampling
No special training needed for extraction
What are the disadvantages of liquid biopsy?
Low amount of material
Early diagnosis
Data interpretation
Why are liquid biopsies good for cancer biomarkers?
Molecular properties within a tumour differ so you get a better overview
No need to identify the tumor site before taking a biopsy
Allows for repeat sampling
When can liquid biopsies be used in cancer biomarkers?
Early disease stages
Check disease response
Determine subsequent therapy
What is an example of a currently approved cancer biomarker test?
EGFR mutation in lung cancer
