Cancer's road map to metastasis revealed
Last Updated: December 07, 2005



LONDON (Reuters) - Scientists have discovered how cancer spreads from
a primary site to other places in the body in a finding that could
open doors for new ways of treating and preventing advanced disease.


Instead of a cell just breaking off from a tumour and travelling
through the bloodstream to another organ where it forms a secondary
tumour, or metastasis, researchers in the United States have shown
that the cancer sends out envoys to prepare the new site.

Intercepting those envoys, or blocking their action with drugs, might
help to prevent the spread of cancer or to treat patients in whom
metastasis has already occurred.

"We are basically looking at all the earlier steps that are involved
in metastasis that we weren't previously aware of. It is complex but
we are opening the door to all these things that occur before the
tumour cell implants itself," said Dr. David Lyden of Cornell
University in New York. "It is a map to where the metastasis will
occur," he added in an interview.

LANDING SITE FOR CANCER CELLS

Cancer's ability to colonise other organs is what makes the disease
so deadly. Once the cancer has spread beyond its original site it is
much more difficult to treat.

In research reported in the journal Nature, Lyden and his colleagues
describe what happens before the arrival of the cancerous cells at
the new site.

"The authors show that tumour cells can mobilise normal bone marrow
cells, causing them to migrate to particular regions and change the
local environment so as to attract and support a developing
metastasis," Dr. Patricia Steeg, of the National Cancer Institute in
Bethesda, Maryland, said in a commentary.

Cells at the site of the metastasis multiply and produce a protein
called fibronectin, which acts like a glue to attract and trap the
bone marrow cells to create a landing pad or nest for the cancer
cells.

"These nests provide attachment factors for the tumour cells to
implant and nurture them. It causes them not only to bind, but to
proliferate. Once that all takes place we have a fully formed
metastatic site or secondary tumour," said Lyden.

"This is the first time anyone has discovered what we call the pre-
metastatic niche."

Without the landing pad, the cancerous cell cannot colonise the organ.

In animal and laboratory studies, the scientists looked at how
breast, lung and oesophageal cancer spread. The envoys from the
tumour determine the site of the secondary site.

Lyden said measuring the number of special bone marrow cells
circulating in the body could help to determine whether a cancer is
likely to spread.

"This opens up the door to new concepts of how metastasis is taking
place. If we can understand all these multiple processes we can
develop new drugs that block each step. That way we have a much
better future than just trying to treat the tumour cell, which is
almost like a last step in this process," he added.





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