FRIDAY, July 11 (HealthDay News) -- California researchers say they have developed molecular "smart bombs" that stop pancreatic and kidney cancer from spreading in mice while causing fewer side effects and damage to healthy surrounding tissues than traditional chemotherapy.

A team from the University of California, San Diego, designed a "nanoparticle" anti-cancer drug delivery system that zooms in on a protein marker called integrin avB3, which is found on the surface of certain tumor blood vessels. The marker is tied to the development of new blood vessels and malignant tumor growth.

While the system had little impact on primary tumors, it halted the metastasis of pancreatic and kidney cancers throughout the bodies of mice. Cancer metastasis normally is much harder to treat than the primary tumor, and it usually leads to the patient's death.

The findings were published in this week's online issue of the Proceedings of the National Academy of Sciences.

According to the report, the system works with a lower dose of chemotherapy because it attacks the cancer with such precision. In most chemo treatments, the destruction of healthy tissue is a side effect as it floods the body with cancer-killing toxins.

"We were able to establish the desired anti-cancer effect while delivering the drug at levels 15 times below what is needed when the drug is used systemically," study leader David Cheresh, vice chairman of pathology at UCSD, said in a university news release. "Even more interesting is that the metastatic lesions were more sensitive to this therapy than the primary tumor."

UCSD engineers and oncologists together designed the nanoparticle -- a microscopic particle made of lipid-based polymers -- to work with the cancer-killing drug doxorubicin.

"Doxorubicin is known to be an effective anti-cancer drug but has been difficult to give patients an adequate dose without negative side effects," Cheresh said. "This new strategy represents the first time we've seen such an impact on metastatic growth, and it was accomplished without the collateral damage of weight loss or other outward signs of toxicity in the patient."

"Traditional cancer therapies are often limited or non-effective over time, because the toxic side effects limit the dose we can safely deliver to the patient," he said. "This new drug delivery system offers an important advance in treating metastatic disease."

More information

The National Cancer Institute has more about nanotechnology uses in cancer treatment.