Fighting Disease with Sound

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Mon., April 14, 2:30 p.m. PDT
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FIGHTING DISEASE WITH SOUND

SAN FRANCISCO, April 14 -- Zapping a cancer patient's tumor with ultrasound increases the tumor's vulnerability to chemotherapy, according to Dr. Mark Bednarski, a visiting professor/scholar at Stanford University School of Medicine, who is presenting a paper at the American Chemical Society national meeting here today. A focused ultrasound beam temporarily makes blood vessels in the tumor leaky, permitting drugs to move more easily out of the blood vessels into the tumor. Bednarski likens this to "pulling the drain plug and letting the compound drain out of the vasculature into the area you want it." Scientists have been aware of this effect but until now haven't been able to capitalize on it because they couldn't track the beam's effects. The key to Bednarski's method is to combine the ultrasound technique with MRI (magnetic resonance imaging). MRI is used to target the ultrasound beam, track delivery of the drugs to the difficult-to-reach tumors, and gauge their effect at the site.

The technique could be particularly useful in fighting tumors tucked deep in soft tissues such as the liver and brain, which are hard to reach via surgery. Currently such patients are treated with high levels of drugs in the hopes that at least some of the drug will make it to the tumor. Bednarski notes that "this can lead to severe side effects that limit the use of many chemotherapy regimens. Patients get sick because the drugs don't just go where you want them to. It becomes a matter of how much a person can tolerate before the cancer cells die, and that's a matter of how much drug gets to the cancer site. We're trying to alter the ratio of how much drug is going where we want it versus how much is going where we don't."

In animal tests, Bednarski, who worked with radiologist Dr. King Li and other colleagues, loaded liposomes -- microscopic sacs used to deliver drugs and other substances to targets in the body -- with gadolinium ions, which show up in MRI scans. He injected the liposomes intravenously into rabbits, and then focused an ultrasound beam deep within the rabbit thigh muscle for five minutes, making the blood vessels in that region more permeable. MRI imaging showed that area began to accumulate liposome particles after about two hours, indicating that they had leaked out of the blood vessels into the thigh muscle, where they tend to stay put. "Little injury or cellular damage was observed, indicating that the treatment is safe and causes no permanent tissue damage," Bednarski says.

He concludes that "focused ultrasound together with magnetic resonance imaging offers a new vehicle for the selective delivery of chemotherapeutic agents and other pharmaceutical molecules to specific regions in tissues." Bednarski expects human clinical trials for the treatment of head and neck tumors to begin within the year. In addition to the cancer therapy applications, he is also looking into the use of this technology for the "delivery of genes for the production of therapeutic protein." One potential application is as a substitute for bypass surgery. Bednarski explains the delivered genes would program cells in the region of damaged heart tissue to produce fibroblast growth factor -- which causes blood vessels to grow -- resulting in a sort of naturally assisted bypass.

CARB 16 will be presented at 2:15 p.m., Mon., April 14, in Rooms 122/125, Exhibit Level, Moscone Center. The national meeting of the American Chemical Society will be held in San Francisco April 13-17. This paper is among the 7,700 presentations that will be made.

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The American Chemical Society, founded in 1876, is the world's largest scientific society, with more than 151,000 members.