The next step for the Swiss team is already clear: find out if the light switch works inside a living animal. The molecule, a photoPROTAC, has only been tested in lab conditions so far. Erick M.
Carreira and Katharina Gapp of ETH Zürich need to prove their creation can reach a tumor, get turned on by a specific color of light, and destroy the glucocorticoid receptor without hitting the rest of the body. That is a big jump from a dish to a mouse.
If it works in animals, the next question is timing. The receptor sits inside cells. It reacts to stress hormones.
In some solid tumors, especially lung cancer, that reaction pushes cells into a drug-resistant, dormant state. The photoPROTAC is engineered to stay inert in the dark.
Shine the right light, and it goes to work. Keep the light off, and it does nothing. That precision is the whole point.
The same receptor calms inflammation everywhere else in the body. Wiping it out systemically would cause real damage. The team needed a way to hit it only inside the tumor.
They built a class of molecules they call photoPROTACs. The research is described in the journal Proceedings of the National Academy of Sciences.
What is at stake is the ability to probe, and possibly disrupt, the hiding strategy cancer uses to survive treatment. Tumor cells slip into a kind of biological hibernation. They shrug off drugs.
They lie low until conditions improve. Then they wake up and bring the disease back.
For decades, researchers have struggled to shut down that trick without causing harm elsewhere. The obvious fix was to destroy the receptor outright. But the catch was always the same: the receptor does important jobs all over the body.
Removing it everywhere would cause damage. The photoPROTAC approach offers a way around that. Shine the right light on the tumor, and the molecule destroys the receptor there.
Leave the rest of the body in the dark. Now the team has to show it can be done in a living system.
That means getting the molecule into a tumor, delivering the right wavelength of light to the right spot, and watching the receptor disappear without side effects. It is a narrow path. Light does not penetrate tissue well.
Getting it deep into a lung tumor, for example, will require a delivery method the team has not yet described in the paper. Gapp and Carreira have not announced a timeline for animal trials.
No dates have been set. No next paper has been promised. The work is at the stage where the mechanism is proven in principle.
The hard part — showing it works in a body — is still ahead. If it does, the implications are significant. Cancer’s dirty trick, the cellular sleep state, would have a targeted off switch.
The disease would lose its hiding place. But that is a long way off.
The photoPROTAC is a molecule. It is not a drug. It is not a therapy.
It is a tool for probing a biological process. Whether that tool becomes a treatment depends on the next experiments.
The team has built the switch. Now they have to prove it flips.
