Body's Own Natural Immunity
To Cancer Now Understood
WASHINGTON Scientists said on Monday they had seen for the first time how the body can naturally fight off cancer " a discovery that they said could lead to new ways to battle the disease.
They found immune cells known as T-cells that can kill cancer cells. Doctors had suspected such T-cells existed but had not been able to find them.
"We have discovered something that had been hypothesized for a long time " which is that the body is able to make an immune response that can kill its own cancer cells,'' Dr. Robert Darnell of the Rockefeller University, who led the study, said in a telephone interview.
But patients who have such cancer-killing T-cells pay a heavy price. They develop a condition known as paraneoplastic cerebellar disorder (PCD), which causes brain damage that makes them fall down and have difficulty eating.
When such patients come to doctors, 90 percent of them are found to have little tumours they did not even know about.
Darnell wanted to see if whatever was causing the brain damage was also holding those tumours in check.
It turned out the cancer cells were waving a little flag at the immune system - a flag they share with brain cells.
Darnell's team studied four patients, one who was in the acute stage, having just started developing symptoms in the past three weeks, and the other three suffering chronic PCD for six months or more.
It had been noticed that patients' tumour cells were expressing a protein " that means generating it " that is normally found only in the brain.
So Darnell's team took some cells, manipulated them to express the protein, which is known as cdr2, and put them in a lab dish with immune cells from the patients.
The patients' T-cells " immune cells that attack invaders " killed the cells with cdr2 on them.
"So that shows immune response,'' Darnell said.
"This is really the first observation of cells that can kill tumours in people. We'd like to find out how normal this is,'' he said.
Darnell said cdr2 was normally only found in the brain, so it would be interesting to find out why the tumour cells were expressing it.
It also seems that in the women with PCD, the T-cells are crossing the blood-brain barrier to attack the neurons that normally express cdr2 " something they are not supposed to do.
In higher animals such as humans, the immune system is kept strictly separate from the brain.
"What we believe is going on is that cancer cells are sometimes expressing proteins normally made only in the brain by neurons,'' Darnell said. "When these are taken out and expressed in tumour cells it's a lot like the body seeing a foreign protein produced by virus.''
So the T-cells kill it.
The big hope is that this ability of the body could be turned on in other cancer patients.
Darnell said a doctor would have to take a patient's T-cells, manipulate them and then inject them back in the patient.
Unfortunately, while cells expressing cdr2 are abundant in the PCD patients, Darnell's team could not find them in anyone else.
But there might be other proteins that would work.
Darnell thinks a lot of people might be fighting off cancer, with no side effects.
"If you or I were to get cancer, and our body was able to effectively recognise it, we might wipe out the cancer in a week or two weeks just like we were wiping out a viral infection like the common cold,'' he said.
"It's been hypothesized that people might be cropping up with cancers all the time and immune cells might be recognising it. Maybe (the cancers that are diagnosed) are the tip of (the) iceberg.''