For years, doctors have looked at tissue biopsies and spotted unusual
cells that seem to have early signs of cancer. The problem is that, until
recently, doctors have never had the right tools to extract the cells from
the tissue, leaving them with no good way to confirm their observation
while the tumor is in its early stages and most treatable.
That situation changed recently with the publication of a report on
a powerful new technique, called laser capture microdissection, that can
pull out a small cluster of cells from a tissue sample in as little as
By taking these cells directly from the tissue, National Institutes
of Health (NIH) scientists say that they can immediately analyze the cells'
gene and enzyme activity with other research tools. Currently, scientists
must attempt to extract, or microdissect, cells either by trying to yank
them free with a manual tool or through a convoluted process of isolating
and culturing the cells. Most scientists consider both approaches to be
tedious, time-consuming, and inefficient.
According to Lance Liotta, MD, PhD, a scientist at the National Cancer
Institute (NCI) and senior author of the paper, published in the November
8, 1996, issue of Science, the direct access to cells should revolutionize
the understanding of the molecular basis of cancer and other diseases,
helping to lay the groundwork for earlier and more precise disease detection.
"Having this technique is the difference between being able to
investigate a crime in progress and going back 2 weeks later to the scene
of the crime when much of the evidence has vanished, as we typically do
now," said Liotta. "Laser capture microdissection gives us access
to the disease, in a sense, while the crime is still in the planning stages,
and that's really powerful information to have in designing strategies
to halt the disease process."
"Low-Tech," User-Friendly Procedure
Laser capture microdissection is a fully automated, one-step technique
that, in today's high-tech world, has emerged as a remarkably low-tech
creation. It integrates a standard laboratory microscope with a low-energy
laser and a transparent ethylene vinyl acetate polymer thermoplastic film--the
same plastic seal as is used in a container of yogurt.
Michael Emmert-Buck, MD, PhD, an NCI scientist and lead author of the
paper, said the group's prototype device works on the same basic aim-and-shoot
principle as a fully automated camera:
- Scientist looks through a microscope at a tissue biopsy, which typically
contains hundreds of different types of cells.
- Upon spotting a group of tumor cells, for example, the scientist presses
a button attached to the side of the microscope. The button activates the
laser, which flashes a beam of light that has an intensity slightly greater
than a laser pointer.
- The beam of light passes through the plastic film placed above the
tissue sample and focuses onto the cells. In the process, the beam heats
the plastic, giving it the thermal qualities of a piece of cellophane tape.
The cells then stick to the plastic directly above them, whereupon the
cells are immediately extracted and ready for analysis.
Emmert-Buck said he and his colleagues purposely designed their device
with a camera in mind. "We wanted an instrument that any scientist
could sit down and use immediately," he said. "That meant creating
a fully automated, user-friendly device that was free of any tricky, manual
manipulations to complicate its operation. A camera seemed like a device
that is simple and familiar to most people. With this idea in mind, we
spent about 2 years creating a viable, one-step technique."
In the Science paper, Emmert-Buck and colleagues report that
laser capture microdissection has successfully extracted cells in all tissues
in which it has been tested. These include kidney glomeruli, in situ breast
carcinoma, atypical ductal hyperplasia of the breast, prostatic intraepithelial
neoplasia, and lymphoid follicles.
They reported no limitation in their ability to amplify DNA or RNA from
tumor cells extracted with laser capture microdissection. The scientists
also found that they were able to recover enzymes from within the cells
and test them for activity.
Robert F. Bonner, PhD, a coauthor on the paper and a scientist with
NIH's National Center for Research Resources, said laser capture microdissection,
like all emerging techniques, still has room for improvement. Bonner said
with further refinement of the plastic film and activation of a finer laser
beam, he could easily foresee the technique extracting single cells, rather
than the two or three cells at a time that it now yields.
Technique May Prove Useful in Recording Gene Expression Patterns
Another likely role for the technique is in helping to record the patterns
of gene expression in various cell types, an emerging issue in medical
research. For instance, NCI's Cancer Genome Anatomy Project (CGAP) seeks,
in part, to define the patterns of gene expression in normal, precancerous,
and malignant cells.
In projects such as CGAP, laser capture microdissection fits in nicely
at the front end of the process as the tool that procures pure cell samples
from tissue, feeding the rest of the analytical process.
Given the technique's great potential to advance the study of biology
and medicine, the NCI has made plans to make the device widely available
to researchers and clinicians around the country. A demonstration project
is already in the works with Steven Bova, MD, a scientist in the Departments
of Urology and Pathology at The Johns Hopkins University School of Medicine.
Liotta said the aim of this project is to receive input from fellow researchers
on how the device might be simplified even more, while also achieving the
highest standard of quality.
"As new information accrues about the genetics of cancer and other
human diseases, it opens up new opportunities for discovery, which will
ultimately lead to more targeted ways to diagnose and treat disease,"
said Richard Klausner, MD, NCI director. "The NCI recognizes that
it has a commitment to place powerful, new research tools into the hands
of scientists to catalyze the discovery process. And, the NCI will make
every effort to do so with laser capture microdissection."