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.