Bubble zeros in on deadly tumours

Cancer researchers Thomas Madden and Marcel Bally are working on getting the
bubble to burst.

Madden, an adjunct professor of pharmacology, and Bally, a biochemist at the
B.C. Cancer Agency, are designing a new type of liposome, or fat bubble, that
can deliver anti-cancer drugs directly into tumours.

Liposome therapy is less toxic and more effective than other types of chemotherapy.

A bubble containing anti-cancer drug is carried through the bloodstream directly
to the site of the tumour. The drug is encapsulated by the bubble as it travels
through the bloodstream so healthy cells aren’t damaged and patients experience
fewer side effects from their chemotherapy.

Using liposomes as drug carriers means that 10 to 20 times more anti-cancer
drug can be delivered to the tumour than is used in conventional therapies.
Because of the concentrated drug dosage, liposome therapy doesn’t need to last
as long as conventional chemotherapy

How does it work? Microscopic bubbles containing the drug are injected intravenously
and move through the bloodstream. When the blood reaches the tumour site, liposomes
find their target.

Blood vessels in tumours are leaky, weakened by the cancer’s rapid growth.

“The vessels have holes just like a sieve,” says Bally. “We control liposome
size so they’re small enough to travel through the holes and move right into
the blood vessels supplying the tumour.”

A concentration of bubbles then starts to build at the site.

The only problem is getting the bubbles to burst.

“Although we can get the bubbles accumulating at the tumour site, they don’t
release the drug well,” says Madden. “We’re working on a new type of bubble
that becomes unstable over time, and either fuses with the cancer cells or bursts,
releasing the drug directly into the tumour site.”

A full release of liposome contents would ensure all the drug was being used,
making it more effective.

Liposome therapy has been the subject of research since the 1960s when lipid
bubbles were first created. The therapy works best with solid tumours whose
blood vessels provide an entry point for the bubbles.

In the 1980s, Madden, Bally and other UBC researchers worked on a first generation
of liposomes, which is undergoing widespread clinical testing in the United
States for the treatment of breast cancer.

Because it would revolutionize cancer treatment, researchers world-wide are
investigating liposome therapy. Researchers have confirmed that drug release
from the bubbles can be controlled and that the process results in improved
anti-cancer activity.

Madden and Bally’s research on the new type of liposome is being supported
by the National Cancer Institute of Canada through funds provided by the Canadian
Cancer Society, B.C. and Yukon division.