Light‐Controlled Cell‐Cycle Arrest and Apoptosis

Cell‐cycle interference by small molecules has widely been used to study fundamental biological mechanisms and to treat a great variety of diseases, most notably cancer. However, at present only limited possibilities exist for spatio‐temporal control of the cell cycle. Here we report on a photocaging strategy to reversibly arrest the cell cycle at metaphase or induce apoptosis using blue‐light irradiation. The versatile proteasome inhibitor MG132 is photocaged directly at the reactive aldehyde function effectively masking its biological activity. Upon irradiation reversible cell‐cycle arrest in the metaphase is demonstrated to take place in vivo. Similarly, apoptosis can efficiently be induced by irradiation of human cancer cells. With the developed photopharmacological approach spatio‐temporal control of the cell cycle is thus enabled with very high modulation, as caged MG132 shows no effect on proliferation in the dark. In addition, full compatibility of photo‐controlled uncaging with dynamic microscopy techniques in vivo is demonstrated. This visible‐light responsive tool should be of great value for biological as well as medicinal approaches in need of high‐precision targeting of the proteasome and thereby the cell cycle and apoptosis.