New research suggests that the most dangerous part
of any cancer is the thin, single-cell boundary where
a tumor meets healthy tissue.
Tumor cells that border normal tissue receive signals
that instruct them to leave the tumor and travel through
the body, resulting in the formation of deadly metastatic
tumors in other locations, report researchers at Washington
University School of Medicine in St. Louis.
The findings, which appear in the Jan. 10 issue of the
journal Developmental Cell, demonstrate the importance
of a tumor's environment. They also provide more information
about the metastatic process and how it might be halted,
the researchers said.
"What actually kills in cancer is not the primary
tumor -- it's metastasis. You can't study that in a laboratory
dish. You have to look at the tumor cells in their natural
environment, surrounded by normal tissues," senior
author Ross L. Cagan, associate professor of molecular
biology and pharmacology, said in a prepared statement.
He and his colleagues created tumors in fruit fly eyes
and wings and then observed the behavior of individual
tumor cells in those settings.
"We found that the tumor cells in direct contact
with normal cells had a different behavior than cells
further inside the tumor. They were exclusively the ones
that tended to leave the tissue," study lead author
Marcos Vidal, research associate in molecular biology
and pharmacology, said in a prepared statement.
The cancer cells that left the tumors in the fruit flies
eventually succumbed to natural programmed cell death
and were eliminated. This was not unusual.
"In a tumor, probably 99.9 percent of the border
cells are raining out of the edges and dying," Cagan
noted. "But as oncologists have found, cancer stems
from an accumulation of genetic mutations. If one of these
wandering cells acquires a second mutation that prevents
cell death, it could go on to establish a metastatic tumor."
The researchers are now investigating ways of preventing
metastatic behavior in these tumor boundary cells.
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