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
For years, doctors have looked at tissue biopsies and spotted unusualcells that seem to have early signs of cancer. The problem is that, untilrecently, doctors have never had the right tools to extract the cells fromthe tissue, leaving them with no good way to confirm their observationwhile the tumor is in its early stages and most treatable.
That situation changed recently with the publication of a report ona powerful new technique, called laser capture microdissection, that canpull out a small cluster of cells from a tissue sample in as little as8 seconds.
By taking these cells directly from the tissue, National Institutesof Health (NIH) scientists say that they can immediately analyze the cells'gene and enzyme activity with other research tools. Currently, scientistsmust attempt to extract, or microdissect, cells either by trying to yankthem free with a manual tool or through a convoluted process of isolatingand culturing the cells. Most scientists consider both approaches to betedious, time-consuming, and inefficient.
According to Lance Liotta, MD, PhD, a scientist at the National CancerInstitute (NCI) and senior author of the paper, published in the November8, 1996, issue of Science, the direct access to cells should revolutionizethe 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 toinvestigate a crime in progress and going back 2 weeks later to the sceneof the crime when much of the evidence has vanished, as we typically donow," said Liotta. "Laser capture microdissection gives us accessto the disease, in a sense, while the crime is still in the planning stages,and that's really powerful information to have in designing strategiesto halt the disease process."
"Low-Tech," User-Friendly Procedure
Laser capture microdissection is a fully automated, one-step techniquethat, in today's high-tech world, has emerged as a remarkably low-techcreation. It integrates a standard laboratory microscope with a low-energylaser and a transparent ethylene vinyl acetate polymer thermoplastic film--thesame plastic seal as is used in a container of yogurt.
Michael Emmert-Buck, MD, PhD, an NCI scientist and lead author of thepaper, said the group's prototype device works on the same basic aim-and-shootprinciple as a fully automated camera:
Emmert-Buck said he and his colleagues purposely designed their devicewith a camera in mind. "We wanted an instrument that any scientistcould sit down and use immediately," he said. "That meant creatinga fully automated, user-friendly device that was free of any tricky, manualmanipulations to complicate its operation. A camera seemed like a devicethat is simple and familiar to most people. With this idea in mind, wespent about 2 years creating a viable, one-step technique."
In the Science paper, Emmert-Buck and colleagues report thatlaser capture microdissection has successfully extracted cells in all tissuesin which it has been tested. These include kidney glomeruli, in situ breastcarcinoma, atypical ductal hyperplasia of the breast, prostatic intraepithelialneoplasia, and lymphoid follicles.
They reported no limitation in their ability to amplify DNA or RNA fromtumor cells extracted with laser capture microdissection. The scientistsalso found that they were able to recover enzymes from within the cellsand test them for activity.
Robert F. Bonner, PhD, a coauthor on the paper and a scientist withNIH's National Center for Research Resources, said laser capture microdissection,like all emerging techniques, still has room for improvement. Bonner saidwith further refinement of the plastic film and activation of a finer laserbeam, he could easily foresee the technique extracting single cells, ratherthan 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 patternsof gene expression in various cell types, an emerging issue in medicalresearch. 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 nicelyat the front end of the process as the tool that procures pure cell samplesfrom tissue, feeding the rest of the analytical process.
Given the technique's great potential to advance the study of biologyand medicine, the NCI has made plans to make the device widely availableto researchers and clinicians around the country. A demonstration projectis already in the works with Steven Bova, MD, a scientist in the Departmentsof Urology and Pathology at The Johns Hopkins University School of Medicine.Liotta said the aim of this project is to receive input from fellow researcherson how the device might be simplified even more, while also achieving thehighest standard of quality.
"As new information accrues about the genetics of cancer and otherhuman diseases, it opens up new opportunities for discovery, which willultimately lead to more targeted ways to diagnose and treat disease,"said Richard Klausner, MD, NCI director. "The NCI recognizes thatit has a commitment to place powerful, new research tools into the handsof scientists to catalyze the discovery process. And, the NCI will makeevery effort to do so with laser capture microdissection."