Stanford researchers elicit more efficient cancer drug delivery method

April 21, 2014, 12:27 a.m.
Courtesy of Bryan Smith
Courtesy of Bryan Smith

A team of Stanford researchers has identified a more efficient means of delivering nanoparticle cancer drugs to afflicted cells, opening the door to an original method of cancer therapy.

The research team — which was led by Professor of Radiology Sanjiv Gambhir — had sought to look into whether or not the immune system could become a Trojan horse for more efficient nanoparticle cancer drug delivery.

“Certain kinds of immune cells are gobbling up nanoparticles and taking them to tumor site,” Gambhir explained.

Given their potential for precise targeting and active cellular uptake, nanoparticles have emerged as a promising class of cancer therapeutics. The human body’s unique treatment of such small particles — nanoparticles range from one to a few hundred nanometers — in size may also enhance the delivery of nanoparticles into the tumor bed

“The nanoparticle itself is very simple,” Gambhir said. “It is just carbon atoms rolled up in a cylinder.

Senior research scientist Bryan Smith explained that the team had injected the nanoparticles into living mice with tumors in order to visualize the nanoparticles’ behavior. Although researchers had expected the nanoparticles to find the tumor on their own, they found that many of the nanoparticles rapidly entered circulating cells in the bloodstream.

“The nanoparticles were taken up with unprecedented selectivity by a single subset of monocytes,” Smith recalled.

The team also found that monocytes, an immune cell for fueling many diseases including cancer, ferried the nanoparticles into the tumor like a Trojan horse.

Gambhir emphasized that the research was only possible with state-of-the-art imaging, which allowed them to watch the immune cells and nanoparticles moving in a living animal.

“Once you can visualize what is going on at the cellular level, then you can start to unmask things,” Gambhir said. “Imaging is powerful because it lets you construct a movie for the entire process as opposed to taking snapshots.”

“Microscopy techniques in animals let us understand exactly what is going on and then that let’s us optimize what we can do in humans,” he added.

The researchers next plan to address whether the results are predictive of what might happen in humans and in various cancer models. Smith expressed hope that human trials of drugs targeted with this mechanism would take plan within ten years.

According to Gambhir, although researchers know that the immune system interacts heavily with tumors, they have not yet determined the exact details of those interactions.

“Researchers haven’t been able to harness the power of the immune system to destroy tumors,” Gambhir said.

Gambhir framed an ideal future scenario as one in which doctors would be able to remove a patient’s own immune cells, preload them with nanoparticles carrying the right drugs and put them back in the body to find and destroy the tumor.

The researchers’ work was published in Nature Nanoparticles last week.


Contact Julia Turan at jturan ‘at’ stanford ‘dot’ edu.

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