"Johns Hopkins researchers have devised a protein "switch" that instructs cancer cells to produce their own anti-cancer medication.

In lab tests, the researchers showed that these switches, working from inside the cells, can activate a powerful cell-killing drug when the device detects a marker linked to cancer. The goal, the scientists said, is to deploy a new type of weapon that causes cancer cells to self-destruct while sparing healthy tissue.

This new cancer-fighting strategy and promising early lab test results were reported this week in the online early edition of Proceedings of the National Academy of Sciences. Although the switches have not yet been tested on human patients, and much more testing must be done, the researchers say they have taken a positive first step toward adding a novel weapon to the difficult task of treating cancer.

One key problem in fighting cancer is that broadly applied chemotherapy usually also harms healthy cells. In the protein switch strategy, however, a doctor would instead administer a "prodrug," meaning an inactive form of a cancer-fighting drug. Only when a cancer marker is present would the cellular switch turn this harmless prodrug into a potent form of chemotherapy.

"The switch in effect turns the cancer cell into a factory for producing the anti-cancer drug inside the cancer cell," said Marc Ostermeier, a Johns Hopkins chemical and biomolecular engineering professor in the Whiting School of Engineering, who supervised development of the switch..."

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