Liquid Biomarker Flashcards

1
Q

what is a liquid biopsy

A

Sampling and analysis of non-solid biological tissue, primarily blood. It is a minimally invasive technology for detection Of molecular biomarkers. Representative Of the tissue/s from which it has spread.

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2
Q

examples of liquids used for liquid biopsy (6 points)

A

blood, plasma, CSF, urine, amniotic fluid, saliva

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3
Q

Types of material we can find circulating in blood (7 points )

A

Circulating endothelial cells (CEC), Extracellular micro-vesicle (exosomes), metabolites, disseminated tumour cells (DTCs),cell free nucleotide, tumour educated platelets (TEPs), circulating tumour cells (CTCs)

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4
Q

what are the 2 types of tube used in liquid biopsy

A

EDTA,citrate

cell-free DNA tubes

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5
Q

properties of EDTA, citrate tubes

A

contain anticoagulant to prevent clotting

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6
Q

Logistics and storage of EDTA, citrate

A

Onsite centrifugation within six hours of collection to isolate plasma and avoid white cell apoptosis. if not possible sample can be stored at 4 degrees Celsius for up to a week

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7
Q

Properties of cell free DNA tubes

A

Contain a stabiliser to prevent release of gDNA from white blood and haemolysis of red blood cells

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8
Q

Logistics and storage of cell free DNA tube

A

Samples can be stored for 6-14 days at 6-37 degree Celsius

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9
Q

speed, time and temperature at which you centrifuge for liquid biopsies

A

15 minutes
2000 xg
4 degrees Celsius

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10
Q

order of content from top to bottom after centrifugation for liquid biopsies and percentages of each content

A

Plasma 55%
less than 1% buffy coat
45% haematocrit

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11
Q

Which content contains cfDNA and exosomes

A

plasma

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12
Q

which content contains WBC and CTCs

A

buffy coat

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13
Q

which content contains RBC

A

Haematocrit

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14
Q

what are circulating tumour cells (CTC)

A
  • Cells that have detached from a tumour and travel through the bloodstream
    to other parts Of the body- single cells or clusters.
  • Marker for tumour growth and negative cancer prognosis and treatment
    response.
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15
Q

why can we isolate tumour cells

A

We can isolate circulating tumour cells because they are CD45 negative EpCAM positive And CK a positive

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16
Q

What is Circulating Tumour DNA (ctDNA)

A
  • Present in different fluids: plasma, serum, urine and others.
  • Low concentration (1-50ng DNA/mL plasma).
  • Amount highly variable for person to person and depending on
    health status in the same person (increase in cancer, trauma, etc.).
  • Presence of permanent genomic DNA
    background in plasma.
    -Highly fragmented with specific size range (less than 500bp)
17
Q

how do you isolate ctDNA

A

using magnetic beads, cellulose based or silica based systems

18
Q

what can next generation sequencing (NGS), Digital droplet PCR (ddPCR) and array CGH be used for when analysing ctDNA from liquid biopsy

A

Amplifications and deletions, Translocations, Point

mutations, Chromosomes abnormalities, epigenetic status (methylation)

19
Q

what can Real Time Quantitative Polymerase Chain reaction (qPCR) be used for when analysing ctDNA from liquid biopsy

A

ctDNA presence quantification

20
Q

5 advantages of liquid biopsies

A
Lower invasiveness 
Higher patient compliance 
Higher cost/effectiveness 
Allow repeated access and multiple 
sampling 
No special training required for extraction
21
Q

3 disadvantages of liquid biopsies

A

Low amount of material
Early diagnosis
Data interpretation

22
Q

why liquid biopsy for detecting cancer

A
  • cancer is a heterogenous disease therefore molecular properties with a tumour differ and also between metastatic sites. this means it would difficult to know where the tumour originates and so will make solid biopsy difficult to do
  • No need to identify tumour site before taking a biopsy
  • allows repeat sampling
  • allow analysis of tissues that’s difficult to access