To determine whether their method could be used to monitor possible changes in HER2 expression in response to treatment, the team next injected the Affibody molecule into mice with tumors that expressed very high or high levels of HER2 and then treated them with the drug 17-DMAG, which is known to decrease HER2 expression. PET scans were performed before and after 17-DMAG treatment. The researchers found that HER2 levels were reduced by 71 percent in mice with tumors that expressed very high levels of HER2 and by 33 percent in mice with tumors that expressed high levels of HER2 in comparison with mice that did not receive 17-DMAG. The researchers confirmed these reductions by using established laboratory techniques to determine the concentrations of HER2 in the tumors after they were removed from the mice.

"Our work shows that PET imaging using Affibody molecules was sufficiently sensitive to detect a twofold to threefold decrease in HER2 expression," said senior author Jacek Capala, Ph.D., of NCI's Center for Cancer Research. "Therefore, PET imaging may provide a considerable advantage over current methods. Our technique would allow a better selection of patients for HER2-targeted therapies and also early detection of tumors that either do not respond to or acquire resistance to these therapies."


"This approach might easily be extended to forms of cancer other than breast cancer," continued Capala. "Because Affibody molecules may be selected to target specific cell proteins, similar compounds can be developed to target proteins that are unique to other types of tumors."
For more information on Dr. Capala's research, please go to http://ccr.cancer.gov/staff/staff.asp?profileid=9891.

NIBIB, a component of NIH, is dedicated to improving health by bridging the physical and biological sciences to develop and apply new biomedical technologies. Additional information and publications are available at http://www.nibib.nih.gov.

NCI leads the National Cancer Program and the NIH effort to dramatically reduce the burden of cancer and improve the lives of cancer patients and their families, through research into prevention and cancer biology, the development of new interventions, and the training and mentoring of new researchers. For more information about cancer, please visit the NCI Web site at http://www.cancer.gov or call NCI's Cancer Information Service at 1-800-4-CANCER (1-800-422-6237).
The National Institutes of Health (NIH) - The Nation's Medical Research Agency - includes 27 Institutes and Centers and is a component of the U.S. Department of Health and Human Services. It is the primary federal agency for conducting and supporting basic, clinical and translational medical research, and it investigates the causes, treatments, and cures for both common and rare diseases. For more information about NIH and its programs, visit www.nih.gov.Reference: Kramer-Marek G, Kiesewetter DO, and Capala J. HER2 expression changes in breast cancer xenografts following therapeutic intervention can be quantified using PET imaging and 18F-labelled Affibody molecules. J. Nucl. Med. Vol.50, No. 7.

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