Dysregulated replication and damage repair of genomic DNA frequently occurs in proliferating cancer cells, leading to generation of aberrant DNA species such as single-stranded DNA (ssDNA) in the cytosol, which in turn activates the cyclic guanosine monophosphate-adenosine monophosphate synthase (cGAS) to produce the secondary messenger cytosolic 2’,3’-cyclic guanylate-adenylyl monophosphate (cGAMP) (1–6). The gene discussed is CGAS; the disease is cancer.