Feeling the tension: Engineered stem cells convert tumor stiffness into a drug target.

Radiopharmaceutical theranostics remains constrained by tumors lacking a validated molecular target. Yang et al.1 engineer mesenchymal stem cells that sense tumor stiffness and respond by manufacturing a synthetic target in situ, making PET imaging and radionuclide therapy possible with existing clinical radioligands in tumors that were previously untargetable.