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Release: Feb. 3, 2000

UI researchers gain insight on basic mechanisms of new cancer treatment

IOWA CITY, Iowa — A team of University of Iowa Health Care researchers is beginning to fill in the basic science blanks of how a new alternative treatment for various cancers works, or in some cases, doesn't work.

The UI investigation centers on a new cancer-killing strategy called photodynamic therapy (PDT). During PDT, patients first receive an injection of a special dye that accumulates in tumor cell membranes. The following day, patients are then exposed to a source of bright light designed to activate the dye and destroy the tumor.

This treatment is proving beneficial for many patients; however, little is known about the basic mechanisms involved. Recently, Freya Q. Schafer, Ph.D., assistant research scientist in the UI Free Radical and Radiation Biology Program, and Garry R. Buettner, Ph.D., UI professor of radiology, found that as the lipid and protein compositions in the cell membrane changed, the responsiveness of the cell to PDT changed as well.

"We need to better understand how photodynamic therapy works so that we can begin to make it work better," Schafer said. "Depending upon whether you have a kidney, lung or bladder tumor, the tumor cells can be quite different and thus may react very differently, so treatments must be adjusted."

Details of the UI findings on PDT are included in a recent issue of the journal Photochemistry and Photobiology.

Schafer and Buettner studied nine different leukemia cell lines during their investigation. The duo wanted to determine cell protein and lipid content and then how the cells reacted to PDT. Schafer and Buettner also wanted to investigate the toxicity of singlet oxygen, which is produced during PDT. The UI researchers conducted their experiments using the photosensitizing dye called Photofrin.

The idea of using PDT dates back about a quarter of a century; however, it has been approved for use in the United States for only the last two years. Other clinicians and basic researchers are attempting to find ways to improve the therapy. Currently, second-generation photosensitizing dyes are in clinical trials. The improved dyes are excreted from the body faster; thus eliminating a person's prolonged sensitivity to light. Researchers are also looking at ways to increase the wavelength of the light used so that the light goes deeper into the tumors.

In addition to their lipid and protein investigation, Schafer and Buettner are looking at how other factors, such as antioxidant vitamins, affect PDT's effectiveness.

The UI investigation is funded by a National Institutes of Health grant.

University of Iowa Health Care describes the partnership between the UI College of Medicine and the UI Hospitals and Clinics and the patient care, medical education and research programs and services they provide.