Looking for Cancer's Fingerprint

Doctors, like detectives, rely on clues. When cancer is suspected, it's important to have as much information as possible in order to make the correct diagnosis and prescribe the best treatment plan.

Focus article photo

Dr. Kauppinen is using nuclear magnetic resonance (NMR) spectroscopy to identify changes in cells that will help diagnose cancer and track response to treatment.

Risto Kauppinen, MD, PhD, works to get doctors the data they need. Kauppinen is director of the Biomedical Nuclear Magnetic Resonance Research Center at Dartmouth Medical School and a member of the Cancer Imaging and Radiobiology Research Program at Norris Cotton Cancer Center. With the help of a technique called nuclear magnetic resonance (NMR), he investigates the molecular identity of cancer cells. The technology behind his work is complicated, but the goal is simple-to find cancer's fingerprint.

The focus of Kauppinen's research is a process called NMR spectroscopy. Every cell contains a number of small molecules called metabolites. The entire collection of metabolites in a sample is called the metabolome, just as all the genes in a DNA sample make up the genome. When cells change—for example, as the result of a genetic mutation that causes cancer—the metabolome changes as well. Certain metabolites will be found at higher or lower levels depending on the changes taking place. NMR spectroscopy can identify the presence of more than 20 different metabolites, so a series of scans will show the changes taking place over time.

Tracking Cell Signals

Producing all this information relies on the complex behavior of the nucleus of an atom. Inside the NMR machine, a superconducting coil bathed in liquid helium creates a powerful magnetic field. In tissue being tested, the protons of some atoms, such as hydrogen, align with the magnetic field.

Then, radio waves are pulsed through the tissue, causing the hydrogen protons to lose their initial alignment. As the protons return to alignment, they emit signals that are picked up by coils in the NMR machine. The behavior of the protons, and the signals they give off, vary depending on the metabolites present in the cells.

Kauppinen can plug this information into pattern-recognition software, which analyzes the results to produce a spectrum showing the levels of various metabolites.

Some cancers already have a known metabolic fingerprint, so if the results from the scan match one of those profiles, it would indicate the type of cancer. Kauppinen and other researchers around the world are collecting the results of NMR spectroscopy scans to create a database that might someday give doctors better information to make accurate cancer diagnoses.

Kauppinen is also using NMR spectroscopy to try to identify changes in the metabolome that may indicate that cancer treatment is working. In that case, a patient could undergo regular NMR scans to check the effectiveness of the treatment regimen. Kauppinen notes that because spectroscopy can be used to study cancer in the patients themselves, it could eventually replace more invasive techniques such as biopsies.

As scientists gather more information, they might be able to help doctors predict which types of tumors are likely to respond to specific treatments, tailoring therapies to the specific profile of a patient. "It's molecular medicine at its best," Kauppinen says.

January 20, 2009