Liquid biopsies Flashcards
What is a liquid biopsy?
= sampling and analysis of non-solid biological tissue, normally blood
- Minimally invasive technology for detection of molecular biomarkers
- Sample is representative of the tissue/s from which it has spread
- At the moment - use solid biopsy, whereas liquid biopsy is the future
What is amniotic fluid analysis?
= example of an established liquid biopsy
What can be detected in blood as a liquid biopsy?
- cell free nucleotides - released by those cells that are normally dying by apoptosis and necrosis - they circulate in the bloodstream for a bit so you can detect them
- circulating endothelial cells - detect heart attacks
- circulating tumour cells
- disseminated tumour cells
- metabolites
- extracellular micro-vesicles
Whats the difference between somatic information and germline information in a liquid biospy?
Mainly interested in somatic information as this is specific to the tissue we are targeting
Germline information can be representative of the whole body, compared to one area eg. Lung in lung cancer
How do we collect liquid biopsies?
10mL blood collected by venepuncture to get 4-5 mL plasma
How can we prevent blood clots, haemolysis and genomic DNA release?
Need to use:
How is the blood biopsy split after centrifugation?
What are the different types of biomarkers that can be found in different liquid biopsy samples?
What are circulating tumour cells (CTC)?
= Cells that have detached from a tumour and travel through the bloodstream to other parts of the body in single cells or clusters
- Marker for tumour growth and negative cancer prognosis and treatment response
- Found in a high background of normal cells - sensitive and specific methods are needed to study them
- Identified/characterised based on transcripts - PCR done on total RNA extracted from the cells
Analysed by NGS, FISH, flow-cytometry, in vivo culture
What is circulating tumour DNA? (ctDNA)
- Present in different fluids - plasma, serum, urine
- Low concentration
- Amount variable for each person and depending on health status (increase in cancer and trauma)
- Presence of permanent genomic DNA background in plasma
Highly fragmented but with specific size range
Has low sensitivity and slightly low specificity
To isolate the ctDNA:
- Transfer supernatant to a clean polypropylene tube and freeze if needed
- Isolation using magnetic bead, cellulose-base or silica-based systems
Can be analysed using: NGS, digital PCR and RTqPCR
What is the advantages and disadvanatges of using liquid biopsies compared to solid?
Advantages:
- Lower invasiveness
- Higher patient compliance
- Higher cost/effectiveness
- Allow repeated access and multiple sampling
- No special training required for extraction
Disadvantages
- Low amount of material
- Early diagnosis
- Data interpretation
How is liquid bioposy used in clinical application for cancer?
Cancer is a heterogenous disease and the molecular properties within a tumour differ and between metastatic sites
- No need to identify tumour site before taking sampling
- Allows analysis tissues difficult to access
Using liquid biopsys you can…
- Monitor response to therapy
- See the progression of the disease
- Extract information at any point
What is cancer biomarkers?
Biomarker testing is a way to look for genes, proteins, and other substances that can provide information about cancer.
Each person’s cancer has a unique pattern of biomarkers.
Some biomarkers affect how certain cancer treatments work.
- Need to be clinically validated
- Not implemented as diagnosis tool yet
- But provides highly specific and complementary information
