Sabine[a]
Cancer vaccine shows promise against brain tumor
By Maggie Fox, Health and Science Correspondent, Reuters: Tue Apr 16, 2002
A cancer vaccine meant to help the body seek out and destroy brain tumors seems to educate the immune system, helping it to prevent cancer from occurring in the first place, researchers said on Tuesday.
Rats treated with the vaccine were not only seemingly cured of their cancer, but when researchers tried to infect them again later with more cancer, they were immune.
The approach is a long way from being tried in humans but opens new avenues in the field of cancer vaccines, the team at the University of California Los Angeles´ Jonsson Cancer Center said.
"The 100 percent protection is pretty dramatic," said Dr. Linda Liau, a brain cancer surgeon who led the study.
Writing in the journal Cancer Research, Liau and colleagues said they started with a Listeria bacteria and spliced in a protein that would act as an antigen. Antigens are flags recognized by immune system cells that attack microbes and cancer cells.
They spliced the same protein into human brain tumor cells, which they injected under the skin of lab rats. When the rats grew tumors, they were injected with the altered bacteria.
As hoped, the bacteria provoked an immune response and the tumors shrank, Liau said.
Then they injected brain tumor cells into the brains of the rats, but none developed brain tumors, when normally they all would have. This suggested that the vaccine was working to prevent cancer, Liau said.
APPROACH EDUCATED IMMUNE SYSTEM
It seemed that once the antigen attracted immune cells to attack cancer cells, the immune cells somehow learned what a cancer cell looked like and were ready to attack when the tumor cells reappeared, she said.
This is good news for the field of cancer vaccines, because each tumor or cancer cell type is different. It was feared that cancer vaccines would have to be tailored to each patient -- an approach that, right now, would not be possible.
Liau said her study suggested that it was not necessary to use an antigen from the tumor. "You don´t really need to know what antigen you are targeting," she said.
"Even though there´s a leap of faith there, the concept is that you could take a human tumor, engineer that, flagging it somehow, and then injecting it back into the human to trigger an immune response," she said.
Such a treatment would be a boon for the 17,000 Americans who develop brain tumors each year, especially those with a type called gliomas. Without treatment, patients with the most aggressive gliomas usually do not live longer than nine months, Liau said.
"We desperately need treatment options for inoperable brain tumors and for the cancer cells that get left behind when we can´t surgically remove an entire tumor," she added.
"I suspect that the body´s immune system is more intelligent than anything we could configure ... and more effective than traditional treatments at leaving healthy cells alone."
However rat experiments do not accurately model human cancer. Laboratory rats get cancer when injected with cancer cells, while human cancer develops over time because of genetic defects or damage.
"Obviously, the concern is that we can cure cancer in rats and mice but we can´t do it in humans," Liau said. "But we won´t know until we try."