Transduction of CLL cells to express ZAP-70 activates Hsp90 and induces sensitivity to 17-AAG-mediated apoptosis. (A) ZAP-70^-leukemia cells were transduced with adenovirus expressing ZAP-70 (Ad-ZAP-70; solid histogram) and β-galactosidase (Ad-LacZ; bold line histogram). Cells were kept in media as a control (dashed line histogram). After 48 hours in culture Ad-ZAP-70- but not Ad-LacZ-transduced cells expressed the ZAP-70 transgene (46% expression with a mean fluorescence intensity ratio [MFIR] of 2.8). (B) ZAP-70^-CLL cells were transduced with adenovirus and after 48 hours they were harvested and lysed. Immunoprecipitations and immunoblots were performed with the antibodies indicated. The bound fractions represent the immunoprecipitated proteins and the unbound samples represent the soluble protein lysate after immunoprecipitation. (C) After 48 hours of transduction with adenovirus, the leukemia cells were treated in vitro with 17-AAG (100 nM) for additional 48 hours and then assessed for apoptosis by flow cytometry using DiOC6 and PI. After treatment with 17-AAG, CLL cells transduced with Ad-ZAP-70 had a significantly higher level of apoptosis compared with nontransduced or Ad-LacZ-transduced cells; P = .001. indicates control, untreated with 17-AAG; ▪, treated with 17-AAG.