Loss of Dhx9 acts in concert with Myc to enhance ABT-737 sensitivity. (A) Growth curves of NIH3T3, NIH3T3/Myc-ER(−4-OHT), and NIH3T3/Myc-ER(+4-OHT) fibroblasts expressing the indicated shRNAs. (B) Cell death was measured in NIH3T3 cells expressing pBABE or pBABE-MycER, as well as the indicated shRNAs. Infected cells were sorted by flow cytometry, exposed to 250 nM 4-OHT for 24 hours and then to vehicle or ABT-737 for an additional 12 hours. Cells were harvested, stained with PI, and analyzed by flow cytometry. Error bars represent standard error of the mean; n = 3. (C) Competition assay of control (shRluc) or Dhx9 shRNAs in the context of either normal Myc levels or Myc suppression in Arf^−/−Eμ-myc/Bcl-2 lymphomas. Lymphomas were infected with the indicated shRNAs, selected with puromycin, and cultured in the presence of media containing vehicle or ABT-737. The percent GFP⁺ cells was determined over a 5-day period. (D) Immunoblot analysis of extracts prepared from Arf^−/−Eμ-myc/Bcl-2 cells that had been infected with retroviral vectors expressing the indicated shRNAs and puromycin selected and sorted for GFP⁺ lymphomas. (E) Arf^−/−Eμ-myc/Bcl-2 lymphomas were infected with the indicated shRNAs and sorted with flow cytometry for GFP⁺. Lymphomas were plated at 100 000 cells per well and allowed to grow an additional 2 days. Cells were then collected and counted. Error bars represent standard error of the mean; n = 3.