Researchers published a tumor‑selective mRNA system (SMRTS) that encodes an internal decision logic enabling therapeutic gene translation in cancer cells while shutting off in healthy tissues. The two‑mRNA design—one encoding Cas6 under microRNA control and a second bearing a Cas6‑cleavable hairpin—showed striking selectivity in mouse tumor models. Authors propose the approach shifts selectivity from delivery vehicles to the mRNA payload itself.