Scientists have identified and blocked the action of a protein
linked to the spread of breast, prostate and skin cancer cells to the
bones.

The molecule called RANKL is produced in bone marrow. In
studies of mice, researchers from Austria and Canada showed that
inhibiting the protein could stop the cancerous cells from migrating to
the bones.

"RANKL is a protein which tells tumor cells to come to
it," said Professor Josef Penninger, of the Austrian Academy of
Sciences in Vienna.

"It sits on the bones and when tumor cells circulate in the body then RANKL attracts them into the bones," he told Reuters.

Once
a cancer has spread beyond its original site in a process known as
metastasis, it becomes much more serious and difficult to treat. An
estimated 70 percent of patients with progressive breast cancer and 84
percent of advanced prostate cancer sufferers develop bone metastases.

The
findings, reported in the journal Nature, explain the puzzle of why
certain cancers spread to the bones and how interfering with the
process could help to prevent the spread of the disease.

When the
researchers gave mice with skin cancer a drug that blocked RANKL, the
rodents had fewer tumors in their bones than animals that were not
treated. But the drug did not slow the spread of the cancer to other
sites in the body.

Penninger and his colleagues stressed that the
research was done in mice but they added that drugs that interfere with
RANKL are in development which could be used test their findings and
show it the same holds true for humans.

"This is an idea that can be directly tested," Penninger added.

Nearly
all breast cancer tumors in women have the receptor for RANKL which
Penninger said is an indirect indication that the findings are relevant
to humans.

"Since there are novel inhibitors of RANKL far along
in clinical development, the idea is that people who have cancer that
is known to spread to bone can start taking this drug when they are
diagnosed," said D. Holstead Jones, of the University of Toronto and
the lead author of the study.

By Patricia Reaney
Reuters.com