Dr. Robert Gallo, collaborating with an international team, reports that a natural hormone produced during pregnancy may become an effective treatment for a painful cancer that strikes many AIDS patients.
The scientists say they destroyed isolated tumors of Kaposi's sarcoma in a group of AIDS patients by injecting the hormone directly into the lesions. Now, they are hoping to bring about whole-body remissions by injecting the drug into the bloodstream.
For years, chemotherapy has been the best option for patients suffering from the cancer, which is marked by bluish-red nodules that spread across the skin and invade internal organs.
But many people with AIDS cannot tolerate chemotherapy because of harsh side effects. Also, traditional anti-cancer drugs can interfere with other drugs that are used to combat the virus itself.
Gallo, co-discoverer of the AIDS virus who recently formed a new institute on the University of Maryland's campus in Baltimore, said the hormone appears to be easily tolerated.
"I think this is a material that is not significantly toxic," said Gallo, director of the Institute of Human Virology.
"We're desperately looking for compounds that are not toxic and are therapeutic," said Dr. Parkash S. Gill, a collaborating scientist at the University of Southern California. "We have the first indication of such a molecule. If it works well as a systemic treatment, it should play a role in the treatment of KS."
The findings appear in today's New England Journal of Medicine.
Gallo said the hormone appears to work by triggering "programmed cell death" in the tumor cells. This is a normal process by which cells die so they can be replaced by new ones. In cancer, genetic changes switch off this process -- resulting in uncontrolled growth.
Relief from the cancer might not extend the lives of people with AIDS, but it would enhance their quality of life. As the cancer invades organs, it can cause internal bleeding and interfere with breathing, digestion and swallowing.
Kaposi's sarcoma, which strikes 10 percent to 20 percent of people with AIDS, can also be extremely disfiguring, with skin lesions and internal tumors eventually merging as they become more numerous. They can number in the hundreds as they spread throughout the body.
The hormone is called hCG, which stands for human chorionic gonadotropin.
It is produced by the placenta, and is commercially extracted from the urine of pregnant women. For many years, it has been used to treat hormonal conditions in men and women.
The discovery that it could be a potent weapon against Kaposi's sarcoma was a chance event.
Dr. Joseph Bryant, a veterinarian who heads animal research at the Institute of Human Virology, was trying to grow human Kaposi's tumors in mice so researchers could more easily study the cancer's biology. It was Gallo's lab that first isolated Kaposi's cells and grew them in a laboratory, but nobody had yet created an animal model for the disease.
Work on animal models for human disease frequently leads to new treatments.
When he injected the cells into mice -- male and female, young and old -- he discovered that the Kaposi's tumors grew in practically all of the animals except those in the early stages of pregnancy. "Something about the pregnancy was protecting them," Bryant said.
Bryant suspected a hormone that is a natural product of pregnancy, so he tested several hormones on mice that already had the cancer. Hormones such as estrogen and progesterone had no effect.
"But lo and behold, if you treated the tumors with hCG, they all resolved," Bryant said.
More recently, Gill administered the hormone to patients at the University of Southern California School of Medicine. The highest of four doses tried was the most effective -- eliminating tumors in almost all cases. No changes were seen in patients given a placebo.
Gallo, Bryant and Gill collaborated with scientists in Belgium and France. Their work is still preliminary.
Each of the patients received hormone injections in just three tumors. In an editorial accompanying today's article, Dr. Susan E. Krown of Memorial Sloan-Kettering Cancer Center in New York noted that the cost of directly treating all of a patient's tumors would be astronomical.
A more practical approach would be to inject the drug into the bloodstream. Gill said he is trying this approach and hopes not only to bring about widespread remission of Kaposi's tumors but also to prevent the growth of new ones.
Despite the hormone's promise, Gallo said he is not sure what exactly is quashing the tumors. There are several pharmaceutical preparations of hCG, and one made by Wyeth-Ayerst Laboratories has worked better than the others. This suggests that a mystery ingredient, not pure hCG, deserves the credit.
Pub Date: 10/24/96