'3 genes spread cancer to brain'
2009-05-07 08:34
Chicago - Three genes in mice may
help explain how breast cancer cells overcome a natural barrier
to get into the brain, scientists said on Wednesday.
Two of the genes, COX2 and HB-EGF, have already been found
to help cancer spread to the lungs, the team reported in the
journal Nature.
The third - ST6GALNAC5 - appears to make the outer coat
of cancer cells sticky, allowing them to linger in tiny blood
vessels in the brain long enough to seep through and enter
brain tissue.
"Our research sheds light on the role these genes play in
determining how breast tumour cells break free and, once mobile,
how they decide where to attack," Joan Massague of Memorial
Sloan-Kettering Cancer Centre in New York and a Howard Hughes
Medical Institute investigator, who worked on the study, said
in a statement.
When breast cancer spreads to the brain, it must pass
through a dense network of capillaries that make up the
so-called blood brain barrier.
This natural barrier helps keep toxins in the blood from
reaching brain tissue. Some advanced cancers, however, manage
to breach this barrier years after the original tumour was
removed.
Top cancer killer of women
To study how this happens, Massague, graduate student Paula
Bos and colleagues used cancer cells from patients whose breast
cancer had spread.
They injected them into mice, and isolated
the ones that could grow in the mouse brain.
They also analysed what genes in the mouse cells and in
human cells were most active.
COX2 and HB-EGF appear to make cancer cells more mobile and
more invasive, they found, while ST6GALNAC5 appears to cause a
chemical reaction that coats the outside of breast cancer
cells, making them sticky.
Massague said it may be possible to find drugs that can
block this process.
Breast cancer is the top cancer killer of women globally.
It is diagnosed in 1.2 million people every year and kills
500 000.