By using tumor-targeting nanoparticles filled with chemotherapy drugs, scientists kept kidney and pancreas cancers from spreading through the bodies of mice.

In an experiment described today in the Proceedings of the National Academy of Sciences, researchers led by University of California, San Diego pathologist David Cheresh designed nanoparticles that selectively attached to a protein found on the surface of blood vessels that supply tumors with nutrients and oxygen.

The particles were loaded with doxorubicin, an effective but highly toxic anti-cancer drug with side effects ranging from white cell destruction to fatal heart disease. By targeting blood vessel cells, the researchers needed just one-fifteenth the amount used in a traditional, system-flooding dose.

"To use an analogy from warfare, we didn't have as much collateral damage," said Cheresh.

Such findings aren't unique in the fast-growing field of cancer nanotech, but the researchers found something new: Although their nanoparticles didn't affect the original tumor, they did stop the cancers from spreading through the mice. That process is known as metastasis – a word synonymous, for anyone who has experience with cancer, with doom.

"Patients often don't die from primary tumors, which you can recognize and detect and develop a therapy for," said Cheresh. "They die from metastatic disease – when, for example, a breast cancer spreads to the liver, the lymph nodes, the brain. Those patients could theoretically be treated with this type of therapy, with the hope that it would prolong the progression of the disease, that the metastatic lesions would slow."

Cheresh said that newly forming tumors, still too small to be detected, depend on a fresh supply of blood. With doxorubicin rendering them unable to form blood vessels, the tumors didn't grow.

Cheresh added that doxorubicin, which has already been approved for human use, is merely one example of what could be achieved through the nanotherapeutic use of other, highly toxic drugs.

In addition to treatment, nanoparticles can also be used for the early detection of cancer.

"Those trials have begun or are in the process of being finalized," he said. "The day isn't too far off."

Nanoparticle-mediated drug delivery to tumor vasculature suppresses metastasis [PNAS]

Image: Areas of nanoparticle binding show up green, courtesy of PNAS.

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