Figure 6.

Pre-B cell receptor–mediated suppression of leukemic growth requires IKAROS function. mRNA levels of Ikaros after μ chain induction were measured by quantitative RT-PCR (A; three experiments). BCR-ABL1–transformed ALL cells were retrovirally transduced with the dominant-negative IKAROS splice variant IK6/GFP or a GFP empty vector control (B–D). Leukemia cells transduced with IK6/GFP (+IK6) or an empty vector control (-IK6) were studied in the presence or absence of pre–B cell receptor activation (+/− μ chain). IK6/GFP- and GFP-transduced leukemia cells were subjected to cell cycle analysis in the presence or absence of inducible pre–B cell receptor signaling (B–D). The percentages of cells in G0/G1, S and G2/M phase are indicated and means of three experiments are indicated in C. In D, the relative increase or decrease of IK6/GFP⁺ versus GFP⁺ leukemia cells in the presence or absence of pre–B cell receptor activation (± μ chain) was measured. The experiment was repeated once.