The chance discovery that some pregnant lab mice are resistant to Kaposi’s sarcoma, a form of cancer seen almost exclusively among AIDS patients, has yielded a promising new treatment for the disease.
The treatment involves a hormone derived from the urine of pregnant women. Researchers found that injections directly into the tumor often make the cancer disappear.
The hormone triggers the cancer cells to commit suicide, although exactly how it works remains a mystery.
“It’s an important finding,” said Dr. Anthony Fauci, head of the National Institute of Allergy and Infectious Diseases. “It certainly has a dramatic effect and needs to be aggressively pursued.”
Kaposi’s sarcoma is a form of skin cancer that is extremely rare except among AIDS patients, especially homosexuals, striking between 15 percent and 30 percent. The disease can be fatal and causes purplish blotches.
Researchers working with AIDS pioneer Robert Gallo, now at the Institute of Human Virology at the University of Maryland, discovered that an inbred strain of hairless mice, which are ordinarily susceptible to all sorts of cancer, could not be induced to get Kaposi’s sarcoma if they were pregnant.
Eventually the researchers found that chorionic gonadotropin, a hormone made early in pregnancy by the human placenta, seemed to stop the cancer in the test tube.
Next, Dr. Parkash S. Gill and colleagues from the University of Southern California tested the treatment on 36 patients. They reported their results in today’s issue of the New England Journal of Medicine.
They tried four commercial varieties and found that one made by Wyeth-Ayerst Laboratories worked best. Cancerous spots went away completely in 10 of 12 patients who got the highest doses, although it is unclear whether the lesions will come back.
Currently, Kaposi’s sarcoma is treated with radiation and chemotherapy, which carry unpleasant side effects. In contrast, chorionic gonadotropin actually makes patients feel better.
“I have never used a drug before that has side effects that patients actually like,” Gill said. “Some gain weight, have improved endurance, can lift more weight and have a feeling of well-being.”
Gill said it costs about $150 to treat one spot of cancer, and the approach is suitable for those with up to 10 or so cancerous outbreaks. Some patients have much more extensive cancer, involving even hundreds of tumors.
Researchers are now testing bloodstream injections of the hormone to see if it stops Kaposi’s sarcoma that has spread through the body.