Researchers published a Molecular Therapy paper describing SMRTS (selective modified RNA translation system), an engineered mRNA approach that activates therapeutic genes in tumor cells while shutting off in healthy cells. The two‑component system uses an mRNA encoding Cas6 (an RNA‑cleaving enzyme) regulated by cancer‑specific microRNAs and a companion therapeutic mRNA with a Cas6‑recognition hairpin. In cancer cells lacking the microRNA, Cas6 is produced and cuts the therapeutic mRNA; in tumor cells where the microRNA silences Cas6, the therapeutic mRNA remains intact and translates. Proof‑of‑concept mouse studies produced cancer‑specific activation for breast and colon variants (bcSMRTS, ccSMRTS), demonstrating markedly improved selectivity in vivo. The approach shifts selectivity from delivery vehicles to programmable mRNA logic.