Nanotechnology turns heat on tumors in mice

Carrie Peyton Dahlberg

SACRAMENTO, Calif. (MCT) — In a small lab tucked behind brick and glass near central Sacramento, Dr. Sally DeNardo is enlisting magnets, molecules and mice in the fight against breast cancer.

For the past four years, using increasingly potent little clusters of iron and antibodies, DeNardo has been testing a treatment to latch tiny metal fragments onto a tumor, then basically cook it to death.

The work has stopped tumor growth in some mice and slowed the cancer in others.

The treatment might be ready for very preliminary testing in humans in as little as two years, said DeNardo, a University of California-Davis professor of oncology and nuclear medicine. It’s too early to predict, though, when or whether the approach could take its place as one more weapon against a disease that has proved far wilier than doctors once hoped.

Researchers have learned from bitter experience that they can cure cancer repeatedly in mice, only to see the same therapies fall short in humans.

Yet DeNardo, lively and determined, remains endlessly hopeful, buoyed by the surge of enthusiasm that has infused nanomedicine, the growing ability to create and manipulate on the “nano” scale – one-billionth of a meter.

The National Cancer Institute sees so much promise that it is spending $144 million over five years for eight special centers, including three in California, to explore how nanotechnology can detect, monitor and treat cancer.

“It’s a very new and exciting and promising direction,” said Sadik Esener, an engineering professor who directs the National Cancer Institute-funded cancer nanotech center at the University of California-San Diego. Other California centers are based at Stanford and the California Institute of Technology.

On this front of the cancer war, doctors, materials scientists, physicists and others are teaming up to create tiny structures that can prowl within the body. Some particles can be used to make better pictures of tumors, while others can shed light on how cancer grows and changes, or perhaps one day will carry drugs directly to cancer cells.

By working on such a minute scale, scientists hope to achieve lethal precision, delivering a killing blow to cancer while sparing healthy tissue.

The University of California-Davis team headed by DeNardo, working with Boston-based Triton BioSystems, is using special antibodies to steer iron oxide nanoparticles to breast cancer tumors. Once the particles have latched onto their target, the team bombards the tumor with alternating magnetic pulses. In this rapid flux, the bits of metal repeatedly switch magnetic poles so fast that they heat up.

One of the beauties of the system, said DeNardo, is that it’s been coupled with radioactive particles, which don’t treat the cancer itself but instead let doctors track what’s going on within the body. That should help calibrate doses and create treatment plans.

Later this month, DeNardo’s team plans to work with a new iron oxide particle that generates more heat from magnetic fluctuations, raising hopes for greater tumor-killing power.

The better particle exists because of strides in nanoscience, DeNardo said, but it also will set researchers back, because they want to see how it performs before moving toward doing any studies in people.

“It’s an art form, I guess, not necessarily science, as to when it’s time to go into human study,” she said. “Sometime along the line you have to say this is good enough and we can’t wait forever.”

Right now, though, the time for human subjects hasn’t arrived.

Instead the group is working with perky, hairless mice whose immune systems aren’t very good at repelling foreign tissue, and whose personalities incline toward a gentle curiosity.

“If they haven’t bit me yet, they’re nice,” said DeNardo as one of her test subjects crawled into the treatment coils that will be used for the next round of testing.

Such mice have been tumor hosts of choice for decades, because a few human cancer cells can be injected under their skin, to grow vigorously into little pink lumps, easily accessible for testing.

The University of California-Davis team is not alone in harnessing nanotechnology to try to heat tumors in mice.

Researchers at Rice University have used gold nanoshells, designed to respond to specific wavelengths of light, to deliver heat to tumors when exposed to near-infrared light.

“There have been many, many experiments trying to cure cancer using magnetic particles” or other nanoparticles and heat, said Sungho Jin, a material science professor at the University of California-San Diego.

Yet with federal funds pouring into nanotech and biotech, Jin said, more work also needs to be done on potential risks. Jin, who co-authored a recent paper looking at potential negative impacts of iron oxide particles on nerve cells, said creating the right particle coatings will be crucial for safety.

As researchers probe nanotechnology’s promise, said San Diego’s Esener, doors could open to many new ways to stop tumors in their tracks, either shutting down their growth or short-circuiting their spread.

So far, those are dreams, not realities, he said, stressing that the field is so young he can’t even begin to guess at a time frame for significant results.

Carrie Peyton Dahlberg

McClatchy Newspapers