Express delivery for cancer drugs

A new drug-delivery method has dramatically reduced tumors in experiments conducted with mice.

Bert Vogelstein and his colleagues at the Johns Hopkins cancer center in Baltimore injected mice with microscopic containers, called liposomes, loaded with the anticancer drug doxorubicin. The blood vessels in and around tumors tend to have larger-than-normal pores, so the liposomes pass into and accumulate in cancerous tissues more readily than they do in healthy ones. The liposomes eventually rupture, releasing the drug.

At the same time, the scientists injected the mice with spores of the modified bacterium Clostridium novyi-NT, which comes to life only in environments depleted of oxygen. Because tumors grow faster than their blood supply, their centers usually lack oxygen. Researchers had noted that the bacterium releases a protein that breaks down the membranes of red blood cells. The Johns Hopkins team decided to combine the therapies, predicting that the protein would penetrate the liposomes and make them deliver their load of drug more efficiently.

The strategy succeeded: Human-colon tumors vanished in mice receiving the combination treatment, but the cancer continued growing in animals getting either treatment alone, the researchers report in the Nov. 24 Science.

“It’s worked remarkably well compared to other therapies, melting away very large tumors,” says Kenneth W. Kinzler, an author of the new report.

He and his coauthors caution that the method has a long way to go before it can be used in people.