[Catalyst 2017]

F
BIOLOGICAL BLOODHOUNDS:
ifty years ago, doctors needed to see
cancer to diagnose it - and by then, it was
usually too late to do anything about it.
Newer tests have made cancer detection
easier and more precise, but preventable
cases continue to slip through the cracks,
often with fatal consequences. However, a
new test has the potential to stop these types
of missed diagnoses - it can detect cancer
from a single drop of blood, and it may finally
allow us to ensure patients receive care when
they need it.
Blood platelets are a major component of
blood, best known for their ability to stop
bleeding by clotting injured blood vessels.
However, blood platelets are far more
versatile than previously understood. When
cancer is formed in the human body, the
tumors shed molecules such as proteins
and RNA directly into the bloodstream. The
blood platelets come in contact with these
shed molecules and will absorb them. This
results in an alteration of the blood platelets’
own RNA. Persons with cancer will therefore
have blood platelets that contain information
about the specific cancer present. These
“educated” blood platelets are called tumor
educated platelets, or TEPs. Recently, TEPs
have been used to aid in the detection of
specific cancers, and even to identify their
locations. 1
In a recent study, a group of scientists
investigated how TEPs could be used to
diagnose cancer. The scientists took blood
platelets from healthy individuals and from
those with either advanced or early stages of
six different types of cancer and compared
their blood platelet RNA. While doing so, the
sniffing out cancer
JESSICA WAGNER
researchers found that those with cancer
had different amounts of certain platelet
RNA molecules. For example, the scientists
discovered that the levels of dozens of
specific non-protein coding RNAs were altered
in patients who had TEPs. The further analysis
of hundreds of different RNA levels, from the
nearly 300 patients in the study, enabled the
scientists to distinguish a cancer-associated
RNA profile from a healthy one. Using these
results, the team created an algorithm that
could classify if someone did or did not have
cancer with up to 96% accuracy. 1
NOT ONLY COULD THE TEPS DISTINGUISH
BETWEEN HEALTHY INDIVIDUALS AND
THOSE WITH A SPECIFIC CANCER,
BUT THEY COULD ALSO IDENTIFY THE
LOCATION OF THE CANCER.
Not only could the TEPs distinguish between
healthy individuals and those with a specific
type of cancer, but they could also identify
the location of the cancer. The patients in
the study had one of six types of cancer:
non-small-cell lung cancer, breast cancer,
pancreatic cancer, colorectal cancer,
glioblastoma, or hepatobiliary cancer.
The scientists analyzed the specific TEPs
associated with the specific types of cancer
and created an algorithm to predict tumor
locations. The TEP-trained algorithm correctly
identified the location of these six types of
cancer 71% of the time. 1
cancerous
protein/RNA
The authors of the study noted that this
is the first blood-borne factor that can
diagnose cancer and pinpoint the location
of primary tumors. It is possible that in the
near future, TEP-based tests could lead to
a new class of extremely accurate liquid
biopsies. Nowadays, many cancer tests are
costly, invasive, or painful. For example,
lung cancer tests require an X-ray, sputum
cytology examination, or tissue sample
biopsy. X-rays and sputum cytology must be
performed after symptoms present, and can
often have misleading results. Biopsies are
more accurate, but are also highly painful
and relatively dangerous. TEP-based blood
tests have the potential to both obviate the
need for these techniques and provide more
granular, clinically useful information. They
can be performed before symptoms are
shown, at low cost, and with minimal patient
discomfort, making them an ideal choice to
interdict a growing tumor early.
The information that TEPs have revealed
has opened a gate to many potential
breakthroughs in the detection of cancer.
With high accuracy and an early detection
time, cancer blood tests have the potential to
save many lives in the future.
WORKS CITED
[1] Best, M. et al. Cancer Cell 2015 28, 676
[2] Marquedant, K. “Tumor RNA within Platelets May
Help Diagnose and Classify Cancer, Identify Treatment
Strategies.” Massachusetts General Hospital. (Accessed
October 22, 2016).
DESIGN BY Katrina Cherk, Monika Karki
EDITED BY Justin Qian
TUMOR
EDUCATED
PLATELET
the researchers found that those with
cancer had different amounts of certain
platelet rna molecules.
CANCER CELL
CATALYST | 5