1. ¹Division of Molecular Therapy, Advanced Clinical Research Center, Institute of Medical Science, University of Tokyo, Tokyo, Japan
2. ²Department of Chemistry and Biotechnology, School of Engineering, University of Tokyo, Tokyo, Japan
3. ³The 21st Century Center of Excellence (COE) Program, Graduate School of Medicine, University of Tokyo, Tokyo, Japan

Correspondence: Dr A Tojo, Division of Molecular Therapy, Advanced Clinical Research Center, Institute of Medical Science, University of Tokyo, 4-6-1 Shirokanedai, Munato-ku, Tokyo 108-8639, Japan. E-mail: a-tojo@ims.u-tokyo.ac.jp

Received 26 August 2007; Revised 18 February 2008; Accepted 19 February 2008; Published online 27 March 2008.

Abstract

The 190 kD (p190) and 210 kD (p210) Bcr-Abl proteins are responsible for the pathophysiology of Philadelphia chromosome (Ph)⁺ leukemia. We applied RNA interference (RNAi) to specific killing of p190⁺ cells, and determined the optimal sequences for gene silencing in the BCR, junctional and ABL regions of p190, respectively. Then, p190⁺ and p210⁺ cells were infected with lentiviral vectors encoding these shRNAs, resulting in efficient killing of p190⁺ cells, while p210⁺ cells were only sensitive to shBCR and shABL. In p190-transformed Ba/F3 cells, silencing of p190 specifically inhibited tyrosine phospohorylation of Stat5 prior to their death, but did not affect phosphorylation of Jak2, Akt or MEK1/2. In contrast, downregulation of p190 by their treatment with 17-allylamino-17-demetoxygeldanamycin (17-AAG) was associated with reduced protein levels of Jak2, Akt and MEK1/2. shRNA targeting p190 collaborated additively with imatinib and 17-AAG in growth inhibition of Ba/F3-p190wt and imatinib-resistant Ba/F3-p190Y253 H cells. Collectively, RNAi-mediated silencing of p190 is a promising option both for delineating signal transduction and for therapeutic application in 190⁺ leukemia.