New Technique May Enable Leukemia Victims to Donate Bone Marrow to Selves

Leukemia patients who lack a matched donor for a bone marrow transplant may someday be able to become self-donors through a new technique that a Wisconsin researcher says has achieved a high success rate in experiments on animals.

The new procedure involves removing marrow from leukemic animals and replacing it several hours later, after it has been treated with a light-activated dye that kills leukemia cells, according to Fritz Sieber, a photobiologist at the Medical College of Wisconsin. The dye is nontoxic to healthy cells, he said.

Compatible Tissue

A trial with human leukemia patients began last week in Milwaukee, the scientist said. If the treatment is successful on humans, it could dramatically increase the number of people with leukemia who may benefit from a marrow transplant but who lack a sibling donor with a compatible tissue type, Sieber said in an interview in Los Angeles, where he is attending a meeting of the American Society of Photobiology. Currently, he said, 70% of leukemia patients lack such donors.

Photobiology is the study of the effects, both beneficial and damaging, that light has on living systems.

The dye, called Merocyanine 540, was originally developed as a means of making film emulsion more evenly responsive to all colors. In the late 1970s it was discovered that the dye could identify leukemia cells from among healthy cells, when they were exposed to light.

It occurred to Sieber, who at the time was involved with bone marrow transplant research at Johns Hopkins University in Baltimore, that the dye could have other uses. He began a series of experiments in which some of the leukemia-ridden bone marrow of mice was removed, treated with the dye and exposed to fluorescent light for 2 1/2 hours in the laboratory.

The mice were given a potentially lethal dose of radiation to destroy the cancerous marrow that remained in their bodies. Their own treated, cancer-free marrow was reinfused into the mice, where it regenerated and resulted in 97% of the animals being cured, Sieber said.

The success rate in humans will not be known for many months, he said.

In another report at the meeting, David Kessel, a photobiologist at Wayne State University in Detroit, discussed how photobiology could be used to successfully treat early lung or bladder cancer.

About 10 years ago, he said, it was discovered that a group of compounds called porphyrins localize in cancer cells and turn the cells bright orange when exposed to ultraviolet light. The exposure also produces a chemical that kills the dyed cells, Kessel said.

Prior Uses

This method of killing cancer cells has been used on several thousand patients worldwide, he said. It is especially applicable to early lung or bladder cancer. A tiny fiberoptic tube is fed into the lung or bladder, allowing doctors to identify the cells and expose them to a red light that is flashed through the tube from outside the body.

Drawbacks to the new therapy, according to Kessel, include the need for highly complex technological equipment and physicians who understand the biological effects of light.

“It doesn’t always work, but when it does work, there is nothing like it,” Kessel said.

Robert H. Haynes, a biologist at York University in Toronto, Canada, told the conference about systems that the body uses to repair damage that ultraviolet light produces in DNA, the genetic material of cells.

Much to the surprise of scientists, Haynes said, it has been discovered that some of these repair systems can be induced by the damaging agent itself. Ultraviolet light, for example, can not only cause a mutation but also triggers an appropriate system to repair the damage.

The capacity of the body to repair some kinds of DNA damage is enormous, according to Haynes, but the ability to do so varies among individuals. It is for this reason that certain genetic populations--the Scotch and Irish, for example--are much more susceptible to skin cancer due to exposure to sunlight, he said.