WEDNESDAY, June 19 (HealthDay News) -- Researchers interested in
learning how certain rodents manage to live long, cancer-free lives
have stumbled upon a potentially valuable clue: a substance outside
their cells seems to help stop malignancies from spreading.
Most research has focused on how cancer occurs inside cells.
Studying the area outside the cell, in what is called the
"extracellular matrix," is new territory, explained study co-author
Vera Gorbunova, a professor of biology and oncology at the
University of Rochester, in Rochester, N.Y.
The substance the team studied is a molecule called hyaluronan.
The rodents, naked mole rats that are the size of mice, live about
eight times longer than rats and mice do. Unlike other mammals,
they also have never been known to develop cancer. As it turned
out, naked mole rats have tissue rich in hyaluronan.
The potentially good news for humans?
Hyaluronan is also a natural component of human tissues, and it
is already used to treat arthritis, cover skin in burn victims and
as an ingredient in anti-wrinkle creams, according to
Hyaluronan works by binding to certain receptors that control
cell behavior. Short forms of the molecule are associated with
inflammation and cell growth, while the longer form (the kind the
naked mole rats possess) are not linked to inflammation and prevent
cell proliferation, Gorbunova explained.
In other words, for cancer cells to spread, they have to break
out of the tissue. Luckily for naked mole rats, their long
molecules of hyaluronan prevent that from happening.
Should the connection between the naked mole rat's form of
hyaluronan and cancer prevention be proven through further
research, it's likely that humans could get injections or pills
that increase the amount of the molecule in their bodies, said
Gorbunova. The next step is to test the ability of hyaluronan to
stop the spread of cancer in mice, she added.
For the research, which was published June 19 in the journal
Nature, the scientists began by looking at naked mole rat
cells in a growth medium in the laboratory. They noticed that their
cells seemed to grow differently than did others, allowing more
space between other cells than expected, said Gorbunova.
The investigators also realized that the growth medium was
somehow becoming unusually "gooey" after a couple of days. They
knew that growth media with cells from humans, guinea pigs and mice
did not become thick and sticky.
But the scientists had no idea what could be transforming the
consistency of the growth medium. "When we saw the gooey media, I
was pessimistic and thought we'd never find out what it was," noted
Gorbunova. But a graduate student working on the research decided
to simply "google" a description of what they had found, and
learned it was hyaluronan, she added.
Next, the researchers tested what would happen if they removed
the hyaluronan, and discovered that the cells then became
susceptible to tumors, confirming the role the molecule plays in
"cancer-proofing" naked mole rats. The scientists went on to
identify the gene responsible for making hyaluronan, and learned
that it was not the same as it is in other mammals.
Hyaluronan, which makes tissue more elastic and facilitates the
healing process, is found in high concentrations in naked mole
rats. The researchers think the rodents may have developed high
levels of the substance to make it easier to squeeze through
Gorbunova said scientists have been focusing on what was going
on inside cells, and now they may start studying the extracellular
matrix. "Now there may be a shift to understanding the
extracellular environment as a key component in cancer
development," she said.
Vadim Gladyshev, director of the Center for Redox Medicine at
Brigham and Women's Hospital and Harvard Medical School, agreed.
The discovery is "a little bit unexpected because it's not the
typical type of cancer research -- studying the outside of cells --
rather than focusing on cell mechanisms and tumor suppressors," he
Gladyshev has something in common with Gorbunova: He's been
studying naked mole rats, too. He published research two years ago
that showed how he sequenced the full genome of the rodents,
looking for clues to their exceptionally long, cancer-free lives.
He thinks her findings should now be examined at the genomic level
to search for pathways associated with the function of hyaluronan.
His hope is that he can pursue that effort in cooperation with
Gorbunova's team, he said.
Learn more about cancer from the
U.S. National Library of Medicine.
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