Old test provides new tricks
January 11, 2013
THE tried and true Pap Test may
show up more than cervical cancer,
with researchers finding it may
contain cells from ovarian and
endometrial cancer also.
The research, published in Science
Translational Medicine, was based
on a small study which analysed
liquid-based pap tests and the
routinely collected DNA the tests
collect.
“We reasoned that this routinely
collected DNA could be exploited to
detect somatic mutations present
in rare tumor cells that accumulate
in the cervix once shed from
endometrial or ovarian cancers,”
the researchers said.
As such, a panel of genes that are
commonly mutated in endometrial
and ovarian cancers was assembled
with new whole-exome sequencing
data from 22 endometrial cancers
and previously published data on
other tumor types.
This panel was then used to
search for mutations in 24
endometrial and 22 ovarian cancers
and identified mutations in all 46
samples.
The researchers then used a
sensitive massively parallel
sequencing method, which enabled
them to identify the same mutations
in the DNA from liquid Pap smear
specimens in 100% of endometrial
cancers (24 of 24) and in 41% of
ovarian cancers (9 of 22).
“Prompted by these findings, we
developed a sequence-based
method to query mutations in 12
genes in a single liquid pap smear
specimen without previous
knowledge of the tumor’s
genotype,” the researchers said.
“When applied to 14 samples
selected from the positive cases
described above, the expected
tumor-specific mutations were
identified,” the researchers added.
As a result, the researchers
concluded that DNA from most
endometrial and a fraction of
ovarian cancers can be detected in
a standard liquid-based pap smear
specimens obtained during routine
pelvic examinations.
“Although improvements need to
be made before applying this test
in a routine clinical manner, it
represents a promising step toward
a broadly applicable screening
methodology for the early
detection of gynecologic
malignancies,” the researchers said.
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