Roanoke Times
Copyright (c) 1995, Landmark Communications, Inc.
DATE: WEDNESDAY, February 17, 1993 TAG: 9302170103
SECTION: NATIONAL/INTERNATIONAL PAGE: A1 EDITION: METRO
SOURCE: Newsday
DATELINE: WASHINGTON LENGTH: Medium
MEDICAL GOAL OF AGES MAY BE NEAR: CANCER VACCINES
After years of struggle, dead ends and failed experiments, medical researchers suspect they finally are closing in on a critical and elusive target: vaccines that stop cancer.In studies at dozens of cancer centers of hundreds of patients with melanoma, enough success against this deadly skin cancer is being seen to warrant optimism. Other types of tumors are being targeted for treatment, although that work is less advanced.
"This is the end of the beginning," said Dr. Donald L. Morton, a cancer specialist at the John Wayne Cancer Institute in Santa Monica, Calif.
Morton noted his own vaccine preparation - "the first successful vaccine that can make tumors in man go away" - has prolonged life in many melanoma patients, and seemingly cured a few.
Morton and others believe cancer vaccines finally show promise of becoming the powerful anti-tumor weapons doctors have long been seeking.
"We are now at the stage where we can look for specific substances that can immunize against cancer," said Dr. Malcolm S. Mitchell, head of immunotherapy at the University of Southern California's Comprehensive Cancer Center. "We've found that the crude vaccines can work. They are effective. The second wave will be finding out what causes a good effect," Mitchell said.
The number of apparent cures is still small, and much work must be done before cancer vaccines could become common. But, because of the potent new tools of molecular biology, and the growing understanding of human immunity, progress is accelerating dramatically.
Unlike vaccines for infectious diseases, the first cancer vaccines being explored would not be aimed at preventing disease. Instead, they would seek to treat existing cancer and prevent it from spreading by stimulating immunity: spurring the body's immune system to attack and kill cancer cells.
To do that, a patient would be injected with harmless versions of other people's cancer cells. These carry antigens, protein molecules that stimulate the immune system. The recipient's immune system recognizes them as foreign bodies and attacks, in the same way it can reject transplanted organs. Once the attack begins, it spreads to the patient's own cancer cells. In other words, the body is tricked into treating its own cancer like a foreign invader.
"Within the next two years," Mitchell predicted, "I'm fairly confident we'll have significant numbers of antigens isolated" from cancer cells for use in potential cancer vaccines.
The idea that the human immune system can be stimulated to attack and reject cancer is not new. Many medical researchers, including Dr. Jean-Claude Bystryn of New York University Medical Center, have pursued that goal for decades. The vaccine approach to cancer is based on knowledge that "the body has machinery that is available to resist cancer cells," Bystryn said. In many cases, the immune system does seem to guard against cancer. That is why people with suppressed immunity, such as organ transplant recipients and people with AIDS, are more prone to some cancers.
All too often the immune system responds poorly to cancer, like a lifeguard hearing the call but stopping at the water's edge. In fact, part of the puzzle lies in finding out why tumors manage to escape immune surveillance.
Most cancer vaccine efforts are aimed at melanoma, which struck about 32,000 people and killed 7,000 in the United States last year. This form of skin cancer can be fatal if it spreads to the lymph nodes, lungs or brain. It is a tempting target because of some evidence that melanoma cells stimulate immunity, somewhat, on their own.