TUMOR INHIBITORY ACTIVITY OF ANTI-RAS RIBOZYMES DELIVERED BY RETROVIRAL GENE-TRANSFER

This study reports the successful introduction into tumor cells of a r ibozyme directed against an oncogene using a retroviral gene delivery system. A hammerhead ribozyme that selectively targets and cleaves the activated Ha ras (V12Ras) oncogene was delivered using a retroviral v ector and expressed under the control of a transfer RNA promoter in V1 2Ras-transformed 3T3 murine fibroblast and rat colon epithelial cells. The expression of V12Ras messenger RNA and V12Ras P21 protein was red uced by up to 100% and 75%, respectively, in cells transduced with fun ctional ribozyme. Reductions in V12Ras expression correlated with the stable expression of the functional ribozyme in vivo and decreased tum origenicity in nude mice. Ribozyme constructs containing identical ant isense flanking regions, but a mutant catalytic center, did not attenu ate V12Ras expression or decrease the tumorigenicity of transduced tum or cells. These data support the potential therapeutic role of antionc ogene ribozymes.