For example, to spatiotemporally regulate therapeutic T cells, a drug can be light activated at a tumor site to mediate multiple cell signaling events: e.g., targeting endogenous proteins such as a programmed death ligand-1 (PD-L1) to inhibit the checkpoint signaling of tumor-dwelling T cells (Zak et al., 2016) and dimerizing T-cell receptor signaling proteins to activate the T cells (Wu et al., 2015). The gene discussed is CD274; the disease is neoplasm.