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Hello everyone and
welcome to this talk on
liquid biopsy in oncology
and tumor evolution.
I'm Giulia Siravegna and
I'm an employee of
Haystack Oncology,
now part of Quest Diagnostics.
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The existence of circulating
free DNA has been
known since 1948,
and later it was found that
its concentration was
higher in cancer patients.
Many groups then
started detecting
tumor-associated
alteration in this DNA,
as well as mutation and
amplification associated
with resistance to
targeted agents
until being able to
sequence the entire exome
directly from plasma DNA.
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Although, when talking
about liquid biopsy,
we refer to both
circulating tumor cells
and circulating cell-free DNA,
and to the analysis
of other sources of
circulating nucleic
acids such as microRNA,
and RNA in circulating
vesicles such as exosomes.
This talk will be focused
only on circulating free DNA.
Circulating DNA is released in
the bloodstream by all
cells in the body,
and it is very fragmented
and of poor quality.
It is released by an
active process, secretion,
from tumor cells in
different organs by
circulating tumor cells,
and by passive processes of
necrosis and apoptosis
by neoplastic cells.
This DNA is very
fragmented and diluted by
the normal DNA which is
released by the healthy cells.
Therefore, in order to be
able to successfully analyze it,
we need very sensitive
technologies.
In all these nucleic acids,
it is possible to assess the
presence of point mutations,
methylation status,
copy number variation,
and structural changes.
The sensitive
technologies that we
exploited involved
too many approaches.
The first is a single or
multiple candidate analysis
exploiting digital-based PCR,
in particular, BEAMing,
which I will talk about later,
and droplet digital PCR
technologies which are able to
precisely detect and quantify
known molecular alterations,
and the second one is based
on next-generation
sequencing technologies,
which are able to interrogate
the whole exome or
selected panel of genes
directly from the
circulating DNA.
With the detection
of point mutation,
copy number variation in
those gene arrangements and
could enable us to
discover novo alterations.
Of course, not every
tumor releases
