Clinical OMICs - Issue 8 - (Page 28)
Clinical OMICs CASE STUDY
Droplet Digital PCR Primes Liquid Biopsies for the Clinic
George Karlin-Neumann
R
esearchers at Memorial Sloan
Kettering Cancer Center
(MSKCC) in New York are investigating the use of Droplet Digital
PCRTM (ddPCRTM) to personalize melanoma treatment using liquid biopsies
in the clinical setting.
Although a common practice for
detecting and monitoring cancer is
through tissue biopsy, more recently,
researchers have looked for a less invasive means of investigating cancerous
cells to assess disease progression
and treatment response. By harnessing the power of advanced DNA testing to perform biopsies using easily
obtained bodily fluids such as urine
and blood-liquid biopsy-these
minimally invasive blood tests have
the potential to detect cancer biomarkers found within cell-free DNA
(cfDNA).
The hope is that this new approach
will accelerate research into what
makes cancers tick, including how
tumors spread, as well as which therapies patients will respond to and how
GEORGE KARLIN-NEUMANN
is director of scientific affairs at
Bio-Rad's Digital Biology Center.
Website: www.biorad.com.
(george_karlin-neumann@bio-rad.
com)
28
Clinical OMICs August 13, 2014
they are responding, offering clues
into recurrence and treatment resistance.
However, despite the promise of liquid biopsies, conventional digital and
real-time PCR assays have been seen
as cumbersome and vulnerable to
false positive results or insufficiently
sensitive, making it nearly impossible
to translate this technique for routine
clinical use. 1
The Droplet Approach
ddPCR has entered into the spotlight
in the past few years as a resource for
cancer investigation, given its ability to rapidly interrogate the cancer
genome with high levels of sensitivity and precision. In fact, researchers
using Bio-Rad Laboratories QX200
ddPCR system for mutation detection
report that they can detect a point
mutation at 0.0005% to 0.001% of
wild type, which is more than 1,000
times more sensitive than conventional quantitative real-time PCR
(qPCR). Essentially, what was previously undetectable with other
methods, can now be detected and
quantified.
At its core, ddPCR counts nucleic
acid molecules by partitioning the
sample in such a way that either zero
or at most a small number of nucleic
acid molecules of interest (i.e., targets) are present in each partition.
The QX200 system partitions samples
into 20,000 droplets containing either
target-specific Taqman assays or
target-specific primers and the fluorescent DNA-binding dye, EvaGreen.
These droplets are then amplified to
endpoint using normal PCR conditions in a conventional thermocycler
to achieve an absolute measurement
of the target concentration through
elevated droplet fluorescence.
The level of sensitivity and precision offered by Bio-Rad's ddPCR system allows researchers to quantify
cancer biomarkers, which could be
the key to bringing liquid biopsies
into the clinic.
Using ddPCR to Monitor
Treatment Response in
Plasma of Patients with
Melanoma
Omar Abdel-Wahab, M.D., an oncologist at MSKCC, and his team used
ddPCR to track disease progression
and identify an effective treatment
regimen for a patient initially diagnosed with BRAF-mutant positive
melanoma. Treatment with the targeted drug vemurafenib-effective
against BRAF mutations but also
known to activate ERK signaling in
www.clinicalomics.com
http://www.biorad.com
http://www.clinicalomics.com
Table of Contents for the Digital Edition of Clinical OMICs - Issue 8
Contents
Clinical OMICs - Issue 8
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