In a Zurich laboratory, a beam of blue light flicks a molecular switch inside lung cancer cells, jolting them awake from a protective slumber that once shielded them from treatment. At ETH Zurich, researchers led by doctoral student Robin Scheuplein and Professor Katharina Gapp have engineered a precision tool that destroys glucocorticoid receptors—molecular gatekeepers that, when activated by stress hormones, send certain cancer cells into dormancy. These dormant cells are notoriously resistant to chemotherapy and radiation, often leading to relapse. But by dismantling the receptors only where it matters, the team has found a way to make tumors vulnerable again—without harming the body’s healthy functions.
Glucocorticoid receptors exist in nearly every cell, regulating inflammation, metabolism, and immune response. A systemic attack on them would be catastrophic. The breakthrough lies in control: the team designed a three-part molecular switch that tags these receptors for destruction, but only when and where it’s needed. The key is a light-sensitive connector developed in collaboration with Professor Erick Carreira’s organic synthesis lab. When exposed to a specific wavelength of light, the connector kinks, deactivating the switch. Outside the tumor, light turns the system off—protecting healthy tissue. Inside the tumor, the switch stays on, marking receptors for the cell’s natural recycling machinery to destroy.
In lab cultures of human lung cancer cells, the active compound triggered a 90% reduction in glucocorticoid receptor levels within hours. Genetic analysis confirmed the cells exited dormancy, resuming metabolic activity and cell division—making them susceptible to conventional therapies. Two of the synthesized connectors, tested among several candidates, responded with perfect light sensitivity, offering a tunable, reversible system. "Activity can therefore be strictly limited to the tumor core, preserving the surrounding tissue and causing significantly fewer side effects. The effect is reversible and can be controlled precisely," says Scheuplein.
While still in preclinical stages, the approach opens doors beyond lung cancer. Breast and prostate cancers also exploit dormancy and glucocorticoid signaling to evade treatment. The system’s modular design could be adapted to target other receptors or diseases. Because it leverages existing medical light-delivery technologies—like endoscopic lasers or implanted LEDs—the path to clinical use is clearer than for many experimental therapies. The next step is testing in animal models, a critical leap toward human trials. For now, the quiet hum of a lab in Zurich holds a promise: one day, a flash of light might wake a tumor up—just so medicine can finish it off.