November 29, 2009 | 11
Rather than surgically removing tumors, what if doctors could simply implant new tools in our bodies to do the work internally? One team of researchers has been able to vanquish tumors in mice by implanting bioengineered disks filled with tumor-specific antigens, and another has developed magnetized nanodiscs to induce cancer cells to destroy themselves.
Numerous cancer vaccines have shown promise in animal models only to later fail to generate results in humans. But an implant-based approach may hold the key, according to a team of immunologists and bioengineers at Harvard University. They designed a tiny polymer disk saturated with dendritic cells and antigens specifically tuned to go after tumor cells. The results, published online November 25 in Science Translational Medicine, show "the power of applying engineering approaches to immunology," David Mooney, a professor of bioengineering ant Harvard’s School of Engineering and Applied Sciences, said in a prepared statement.
The principal is the same as a vaccine: prompt the immune system to attack invading cells. However, unlike previously tested injected cancer vaccines, cells from the disk are less prone to die before they can get the job done.
The 8.5-millimeter biodegradable disk can be "inserted anywhere under the skin—much like the implantable contraceptives that can be placed in a woman’s arm," Mooney said. "The implants activate an immune response that destroys tumor cells." When the disks were implanted in mice with melanoma, the treatment led to remission and longer lives in "a substantial portion of the population," the authors reported.
Another trick to zapping cancer cells may lie in nano-scale magnets. Previous studies have investigated the use of magnetic fields to kill cancer cells via hyperthermia, but they required a lot more power than the new method and proved to have some dangerous side effects.
A new study, published November 29 in Nature Materials, reports promise in a scaled-down version of this idea to tackle tumors. "Nanomagnetic materials offer exciting avenues for probing cell mechanics and…advancing cancer therapies," the paper authors wrote. Using nanodiscs (about 60 nanometers thick) made of iron and nickel, researchers based in the Argonne National Laboratory in Illinois and the University of Chicago Pritzker School of Medicine have created a so-called "magnetic vortex" in the magnetic alloy with the magnetic charge arranged in concentric circles. "Integration of magnetic materials with biological molecules and therapeutics creates hybrid materials with advanced properties," the authors noted in the paper.
By introducing an alternating magnetic field, researchers made the discs oscillate, thereby damaging the membranes of cancer cells in the lab and causing the cells to die. The researchers needed only a frequency of "a few tens of hertz applied for only 10 minutes" to "achieve cancer-cell destruction in vitro," they wrote. With this approach they rely on neither heat nor mechanical assault, but rather on the oscillation "which triggers the programmed cell-death pathway" via an ionic electrical signal, the authors explained. Thus, "the total energy necessary to accomplish cell death is minute."
While these innovative implant technologies are being tested in the lab, however, cancer continues to be one of the leading causes of death in the U.S. (second only to heart disease), killing more than half a million people last year.
Image of polymer matrix (next to dime for size comparison) courtesy of InCytu, Inc.