USE OF AN ANTI-RAS RIBOZYME TO ALTER THE MALIGNANT PHENOTYPE OF A HUMAN BLADDER-CANCER CELL-LINE

Purpose: In this study, we evaluated the ability of a ribozyme (cataly tic RNA), which site specifically cleaves the mRNA of the activated H- ras gene, to alter the malignant phenotype of an invasive human bladde r cancer cell line. Materials and Methods: The human bladder cancer ce ll line EJ which contains the activated H-ras gene was used in these s tudies. Cell lines with and without the anti-ras ribozyme were examine d for their malignant potential in athymic (nude) mice by using an ort hotopic model of bladder cancer. Endpoints evaluated included tumor ta ke and animal survival. Results: EJ tumors containing the anti-ras rib ozyme showed a reduction in tumor take (35% versus 45%) and prolonged survival (74 days versus 65 days) compared with standard EJ cells. Thi s survival advantage was not as pronounced as anticipated. To evaluate this finding, we examined the tumor from mice originally inoculated w ith the ribozyme-containing cell line to determine if the ribozyme was still present. Approximately 60% of the animals had lost ribozyme exp ression. Animals that maintained ribozyme expression had a mean surviv al of 81 +/- 4 days which was significantly prolonged compared with co ntrol mice (65 +/- 5 days). Conclusion: This study suggests that the i nvasive phenotype is blunted with the anti-ras ribozyme, delaying but not abolishing the metastatic phenotype. These results further delinea te the roles of ras genes in malignancy and demonstrate that ribozymes may be a powerful tool for exploring the role of individual oncogenes and may be used as anticancer agents.