IN-VITRO AND IN-VIVO EFFECTS OF SYNTHETIC RIBOZYMES TARGETED AGAINST BCR ABL MESSENGER-RNA/

Chronic myelogenous leukemia (CML) is associated with a translocation of the BCR and the ABL genes, t(9;22). Results of this event are trans cription and translation products that are unique to malignant cells. We therefore designed synthetic ribozymes which are capable of exclusi vely cleaving the BCR/ABL B3A2-type mRNA without altering normal cellu lar transcripts. Synthetic B3A2-type transcripts could only be cleaved by B3A2-type mRNA targeted ribozymes and not by any of the controls. The B3A2-type mRNA directed ribozyme, on the other hand, did not cleav e any of the control transcripts. The effective delivery of ribonuclei c acids by lipofection into K562 cells could be demonstrated by fluore scent microscopy, slot blot analysis, and RNA polyacrylamide gel elect rophoresis. In vivo, we were able to induce a significant inhibition o f the proliferation of K562 cells with ribozymes directed against the B3A2-type mRNA. Quantitative PCR analyses showed an up to fivefold red uction of the relative number of BCR/ABL mRNA molecules per single cel l after exposure to ribozymes compared to controls. We conclude that r ibozymes targeted against the B3A2-type BCR/ABL mRNA function in vitro and in vivo.