Cancer cells executed by magnet

Metal nanoparticles trigger cell's own death machinery

Evil geniuses, commence drooling. Scientists have figured out how to remotely control a cell’s self-destruction. Magnets that guide the behavior of tiny metal beads can be used to flip on a cell’s death switch, kick-starting the cell’s demolition. The approach might one day be used to kill cancer cells or orchestrate other cellular events without drugs or incisions.

In the past, scientists have explored killing cancer using tiny iron-containing nanoparticles that latch onto malignant cells and heat up when exposed to a magnetic field. In the new work, a bit of protein guides each nanoparticle to death receptor 4, an aptly named handle on the outside of a cell that acts as a molecular doomsday switch. Exposing the cells to a magnetic field makes the nanoparticles clump together. This clumping pulls together the three molecular prongs that make up the switch, activating it and triggering a process that leads to the cell’s demise.

The scientists from Yonsei University in South Korea tried the approach with a dish of colon cancer cells. Within 24 hours, more than half of the cells exposed to the magnetic field were dead, the team reports online October 7 in Nature Materials.

“They’ve identified a major opportunity for magnetic nanoparticles,” says bioengineer Andrew MacKay of the University of Southern California. “This might be a new way to do really targeted therapeutics.”

Figuring out how to target only particular cells is an ongoing problem, though. Death receptor 4 sits on normal cells too, which can also be destroyed via remote-controlled magnetism. When the researchers tested their approach on developing zebra fish, the tails of the exposed fish developed a kink where cells were killed off in a particular area.

It’s not yet clear whether the magnetic field could be directed with such finesse and specificity that it would kill only tumor cells and not nearby healthy cells. Many cancer cells become resistant and stop responding to the protein that normally hits the death switch; such cells also might not respond to the magnetic nanoparticle version, says Courtney Broaddus, a doctor at the University of California, San Francisco who investigates resistance in cancer cells.

“But it’s very intriguing, the potential applications of this technology for remote controlling activities at the cell membrane,” she says.

The researchers are now working on extending the concept to switches on other cells, such as those that stimulate blood vessel growth, says chemist and team member Jinwoo Cheon.

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