Researchers from the National Cancer Institute have devised a new method to watch for the presence of the HER2 protein, a commonly expressed marker of breast cancer. As you can imagine, the implications for this technology could be immense, from doing research on pathophysiology of breast CA to developing protocols for treatment.
From the statement issued by the National Cancer Institute:
… the research team used an imaging compound that consists of a radioactive atom (fluorine-18) attached to an Affibody molecule, a small protein that binds strongly and specifically to HER2. Affibody molecules, developed by Affibody AB, Bromma, Sweden, are much smaller than antibodies and can reach the surface of tumors more easily. The radioactive atom allows the distribution of the Affibody molecules in the body to be analyzed by positron emission tomography (PET) imaging.
The research team first used the radiolabeled Affibody molecule to visualize tumors that expressed HER2 in mice. The mice were injected under the skin with human breast cancer cells that varied in their levels of HER2 expression, from no expression to very high expression. After three to five weeks, when tumors had formed, the mice were injected with the Affibody molecule and PET images were recorded. The levels of HER2 expression as determined by PET were consistent with the levels measured in surgically removed samples of the same tumors using established laboratory techniques.
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.
Press release: Imaging Technique Allows Researchers to Monitor Protein Changes in Mouse Tumors
Article abstract in The Journal of Nuclear Medicine: Changes in HER2 Expression in Breast Cancer Xenografts After Therapy Can Be Quantified Using PET and 18F-Labeled Affibody Molecules….