In vivo RNAi Library Screen to Identify Mediators of Disease Progression and Drug Resistance in CML

Abstract : Clinical data indicate a link of disease progression and resistance to imatinib therapy. While previous work on imatininb resistance has focused on mutations in the drug target these cannot explain the reduced effectiveness of imatinib in advanced disease stages. Usinga candidate approach we found that the p53 tumor suppressor is activated by and contributes to the antitumor activity of imatinib. Further p53 is implicated in disease progression inCML (Wendel et al. Proc NatI Acad Sci U S A. 2006 May 9;103(19):7444-9). To further approach the problem using an unbiased approach we proposed an in vivo RNAiscreen. This turned out to be technically extremely challenging and we had to take a very systematic approach at resolving some of the problems. However we have developed i) an improved RNAi design ii) suitable library vectors for in vivo and in vitro work iii)nearly genome wide libraries in these vectors and iv) improved array-based detection methods. With these necessary and important improvements we now have promising preliminary data from in vitro screens.