Suppression of EJ cells tumorigenicity.

: Ribozymes, site-specific ribonucleases, are a new vehicle for the manipulation of gene expression. A hammerhead ribozyme designed to cleave the GUC sequence in codon 12 of activated H-ras RNA was cloned into a plasmid (pH beta Apr-1) and transfected into EJ human bladder carcinoma cells. Expression of the ribozyme dramatically reduced H-ras gene expression and inhibited growth of EJ transformants in vitro. In vivo, the H-ras ribozyme suppressed EJ cell tumorigenicity in nude mice. In contrast, the insertion of a mutant ribozyme with no demonstrable cleavage capacity into EJ cells resulted in smaller reductions in H-ras gene expression and growth inhibition while also suppressing tumorigenicity in nude mice. The ribozyme's effect on tumorigenicity was stable, as the cells were cultured for up to five months in vitro prior to injection into nude mice. These studies define a role for anti-oncogenic ribozymes as a unique class of tumor suppressing agents.