Reversal of the malignant phenotype by an anti-ras ribozyme

In this study a ribozyme (catalytic RNA) was designed to site specifically cleave the mRNA of the activated H-ras gene expressed in human bladder carcinoma EJ cells. The optimal conditions for catalytic cleavage by the ribozyme were demonstrated in vitro. A synthetic DNA encoding the ribozyme was cloned into a mammalian expression vector (pH beta APr-1) and transfected into EJ cells. The expressed ribozyme significantly altered the morphology and suppressed the growth of EJ cells in vitro. These cell lines were examined for their malignant potential in athymic (nude) mice by an orthotopic (transurethral) implantation model, which recapitulates the invasive potential of various bladder carcinomas. EJ tumors expressing the H-ras ribozyme were characterized by a marked reduction in tumor take and invasion compared to those formed by control EJ cells. These differences resulted in almost a twofold increase in survival of mice implanted with ribozyme-containing EJ cells. These results further elucidate the role of ras genes in tumorigenicity and invasion, as well as introduce ribozymes as a new class of anticancer agents.