- 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.
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- 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.
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- "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.
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- 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.
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- When such patients come to doctors, 90
percent of them are found to have little tumours they did not even know
about.
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- Darnell wanted to see if whatever was
causing the brain damage was also holding those tumours in check.
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- It turned out the cancer cells were waving
a little flag at the immune system - a flag they share with brain cells.
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- 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.
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- It had been noticed that patients' tumour
cells were expressing a protein " that means generating it "
that is normally found only in the brain.
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- 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.
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- The patients' T-cells " immune cells
that attack invaders " killed the cells with cdr2 on them.
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- "So that shows immune response,''
Darnell said.
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- "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.
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- 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.
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- 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.
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- In higher animals such as humans, the
immune system is kept strictly separate from the brain.
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- "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.''
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- So the T-cells kill it.
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- The big hope is that this ability of
the body could be turned on in other cancer patients.
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- Darnell said a doctor would have to take
a patient's T-cells, manipulate them and then inject them back in the
patient.
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- Unfortunately, while cells expressing
cdr2 are abundant in the PCD patients, Darnell's team could not find them
in anyone else.
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- But there might be other proteins that
would work.
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- Darnell thinks a lot of people might
be fighting off cancer, with no side effects.
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- "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.
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- "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.''
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