BLNK expression in BLNK^+/−STAT5b-CA pre-B leukemia cell line induces apoptosis. (A) RT-PCR analysis of IL-7 and GAPDH (cDNA quantity control) mRNA expression in the indicated cell lines. (B) The BLNK^+/−STAT5b-CA pre-B leukemia cell line was infected with retroviral vectors carrying either SOCS1, SOCS1 F59D, or BLNK, coupled via an IRES to EGFP. EGFP expression in the virus-infected cells (open) and noninfected cells (shaded) was analyzed by flow cytometry. The percentage of EGFP⁺ cells in each infected sample is indicated. (C-E) BLNK^+/−STAT5B-CA pre-B leukemia cell line was infected with retroviral vectors carrying either SOCS1, SOCS1 F59D, BLNK, or none (MOCK), coupled via an IRES to rCD2. rCD2⁺ cells were sorted by MACS 72 and 96 hours after infection and used for each analysis. (C) Cell-cycle profiles of SOCS1, BLNK, or MOCK-transduced cells were analyzed as in Figure 2A. (D) Sorted cells were stained with annexin-V and analyzed by flow cytometry. The mean (± SD) proportion of apoptotic cells (Annexin-V⁺) in duplicate samples is indicated by each bar. (E) Lysates of BLNK- or MOCK-transduced cells were analyzed by Western blotting with the indicated antibodies. All data are representative of 2 independent experiments.