Light pulses can stimulate a new designer peptide to initiate death pathways in cancer cells. The peptide, linked to a light-responsive dye, remains inactive until exposed to the external light pulses, which convert it into a cell death signal. An interdisciplinary team at Cardiff University developed the peptide switch to alter critical interactions in B-cell lymphoma cancer cells in a controlled way. The pathway-activation technology, called transient photoactivation, may enable scientists to identify cells normally resistant to chemotherapy, thereby leading to the development of more effective treatment strategies. “Whilst killing cancer cells is a goal in itself, this is also proof of a wider principle,” said chemistry professor Rudolf Allemann. “Directing therapeutic peptides to the precise location where they are required can be difficult, but activating peptides with light will allow us to precisely define the area where we wish a peptide to act.” The work demonstrates that cellular processes can be controlled with light. “Our tools can be used to understand the inner workings of cells and to work out how to correct misfiring pathways that lead to disease,” Allemann said, adding that it could bring about light-controlled drugs and tools for probing molecular interactions in intact cells and organisms for basic biomedical research. The findings are published in Molecular Biosystems (doi: 10.1039/C3MB70246D). The work was funded by an Engineering and Physical Sciences Research Council grant worth £1.4 million (about $2.3 million).