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THE sugar coating that surrounds our body’s cells could be exploited to
target tumours, by using fragments of the sugars to stop cancer cells in their
tracks

Much of the research into cancer and other diseases has focused on DNA and
proteins. But the long, straight sugar molecules on the surfaces of cells play a
key role in how cells interact with their surroundings. “They are crucial to how
cells filter information coming in from the outside,” says cell biologist Ram
Sasisekharan.

Normally cells maintain a delicate balance, changing their sugar coats only
when their environment demands it. But Sasisekharan thinks tumour cells switch
their coatings at whim, looking for combinations that enable them to grow and
spread.

Sugars have been hard to study because they are highly complex. They have
dozens of building blocks, compared with four for DNA, and unlike proteins,
sugars don’t have a fixed DNA blueprint. Instead, families of enzymes add bits
of sugar to these dynamic molecules or remove them according to the cell type,
or in response to outside signals. Only in the past two years or so have
researchers been able to routinely study individual sugar molecules.

Sasisekharan and his team at the Massachusetts Institute of Technology
studied a group of sugars called HSGAGs, that are known to change as a tumour
develops. They injected mice that had skin cancer with enzymes called heparinase
I and heparinase III. Both these enzymes snip sugar fragments from HSGAGs, but
in different places. The researchers found that heparinase I accelerated the
growth and spread of the tumours, whereas heparinase III suppressed it.
Intrigued, the team then injected mice with the corresponding sugar fragments,
and saw the same effect.

“It raises the exciting possibility of using this as a therapeutic target,”
says Sasisekharan. Even tiny amounts of sugar fragment had a strong effect, he
adds. And since different cell types have different sugars, therapies could be
targeted to specific tissues, minimising side effects.