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Microchip
seeks out prostate cancer
By Robert Sanders
A clever technique for detecting proteins by inducing them to
stick to and bend a microscopic cantilever -- essentially a diving
board the thickness of a human hair -- is sensitive enough to
serve as a diagnostic test for the protein markers characteristic
of prostate cancer, a team of scientists from universities and
research laboratories across the country reported in a recent
issue of the journal Nature Biotechnology.
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| Three cantilevers coated
with antibodies to PSA, a prostate cancer marker found in
the blood. The left cantilever bends as the protein PSA binds
to the antibody. Although Majumdar and his team did not conduct
the current experiment with three adjacent cantilevers, the
illustration represents some of the individual experiments
they performed. The group currently is making a chip that
can do all three (or more) experiments simultaneously.
Photo courtesy of Kenneth Hsu/UC Berkeley & the Protein
Data Bank |
The protein markers, called PSAs for prostate-specific antigens,
are found at elevated levels in the blood of men with prostate
cancer, the number two killer of American men.
"The technique is sensitive enough to detect levels 20 times
lower than the clinically relevant threshold," says Berkeley
mechanical engineering professor Arun Majumdar, a lead author
of the report. "This is currently as good as, and potentially
better than, the so-called ELISA, enzyme-linked immunosorbent
assay, which is the standard today for detecting protein markers
like PSA."
The microcantilever technique has far broader applications, however.
Any disease, ranging from breast cancer to AIDS, characterized
by protein in blood or urine, could conceivably be assayed by
arrays of these microcantilevers. A microcantilever array would
be one of the first "protein chips," analogous to the
DNA chip used broadly today in research labs and the biotech industry
to conduct hundreds of DNA analysis simultaneously.
"This could lead to fast screening and molecular profiling
for many diseases and a possible chip for detecting cancer,"
says Majumdar.
"A big advantage of this technology is that one could look
at multiple markers in a single reaction, whereas currently available
assays require a separate reaction for each analyte," says
colleague Richard J. Cote, M.D., professor of pathology and urology
at the Keck School of Medicine of the University of Southern California
and the USC/ Norris Comprehensive Cancer Center. "So the
cost of performing a cantilever assay as opposed to a typical
ELISA assay is potentially much, much lower."
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