Using ultrasound to pop drug-containing bubbles introduced into tumors of the liver could be the latest weapon in the fight against cancer in that organ, researchers say.

The technique can be used to accurately reposition a federally-approved cancer-fighting drug to specifically target cancer tumors within the liver, they say.

"In this study, we re-purposed the topical agent bexarotene (Targretin) — currently in limited use for cutaneous manifestations of T-cell lymphomas — and re-engineered it for use in solid tumor applications by forming self-assembling nanobubbles," says study leader Dipanjan Pan of the University of Illinois, Champaign-Urbana.

By using a highly selective activation method — popping the bubbles only within a tumor — healthy cells are spared, says Pan, an assistant professor of bioengineering.

"These tiny bubbles filled with Targretin in 'prodrug' form can be 'popped' to release the drug inside liver cancer cells, activating the prodrug during cellular internalization process," he explains.

A highly targeted but minimally-invasive approach is the result of a "triple attack" technique combining chemotherapy, hyperthermia and thermal ablation, the researchers report in their study appearing in the journal ACS Nano.

Ablation is defined as a process for destroying or removing body tissue.

"In this study, we successfully re-purposed and repackaged bexarotene into a sensitive nanobubble form, inserted it directly into the tumor using a flexible catheter, and used ultrasound ablation therapy to 'pop' the bubbles to release the agent," explains Santosh Misra, a postdoctoral research associate in Pan's laboratory.

"Liver cancer is normally difficult to attack and usually requires significant surgical intervention," he says.

The technique for attacking liver cancer tumors has been successfully demonstrated in animal studies, the researchers say, suggesting the next step could be human trials.

By the end of this year, around 1.66 million new cancer cases of all types will be diagnosed in the United States, with around 35,000 of them being cancers of the liver, according to estimates by the American Cancer Society.

About 24,500 will die of those liver cancers, the society estimates.

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