The cytoplasmic deoxyribonucleic acid (DNA) sensor cyclic guanosine monophosphate (GMP) – adenosine monophosphate (AMP) synthase (cGAS) recognizes cytosolic tumor DNA, and then produces 2′3’‐cyclic GMP‐AMP (2′3’‐cGAMP), a natural ligand of the STING protein. The gene discussed is STING1; the disease is neoplasm.