LB Flashcards
What is a liquid biopsy?
→ Sampling and analysis of non-solid biological tissue, primarily blood
What other liquids are there for liquid biopsies?
→ urine,
→ plasma,
→ serum,
→ saliva
What are saliva biopsies useful for?
→ head and neck cancers
What is CSF biopsies used for?
→ circulating tumour DNA in brain tumours
What is an example of an established liquid biopsy?
→ amniotic fluid
What has amniotic fluid analysis been replaced with and why?
→ substituted with circulating foetal DNA in mothers blood
→ amniotic analysis is invasive
What are some markers for liquid biopsies?
→ cell free nucleotides → tumour educated platelets → circulating tumour cells → disseminated tumour cells → metabolites
Which cells are extracted for liquid biopsies?
Normally interested in somatic information because we can find germline information from any part of the body
→ germ line may not have tumour cells
Why are EDTAs used for venepuncture?
→ Preventing: blood clots
→ genomic DNA release (from white blood cells)
→ haemolysis
What does bursting of white blood cells release?
→ genomic DNA
What are the tubes used for liquid biopsises?
→ EDTA
→ citrate
→ cell free DNA
What are the properties that make EDTAs and citrates useful for LB?
→ contain anticoagulant to prevent clotting
What are the logistical and storage issues for EDTAs?
→ On-site centrifugation within 6hrs of collection to isolate plasma and avoid white cells apoptosis.
→ If not possible, sample can be stored at 4ºC for a up to a week
What are the properties of cell-free DNA tubes that makes them suitable for LB?
→ Contain a stabiliser to prevent release of gDNA from white blood and haemolysis of red blood cells
How can cell-free DNA tubes be stored?
→ Samples can be stored for 6-14 days at 6ºC-37ºC
What makers can be found in the plasma?
→ cfDNA
→ exosomes
→ hormones
What markers are found in the buffy coat layer?
→ WBC and CTC