Activation of the ATM pathway is pivotal for the antileukemic effect of Δ¹²-PGJ₃. (A) Western blot analysis of FV-LSCs treated with Δ¹²-PGJ₃ or vehicle control. Cell lysates were probed with indicated Abs. (B) TUNEL assay of spleen sections from Δ¹²-PGJ₃- or vehicle-treated, FV-infected mice. (C) Analysis of p53 transcript levels in FV-LSCs treated with Δ¹²-PGJ₃ (25nM) or in combination with the ATM inhibitor MTPO (50nM), CGK-733 (1μM), or DMSO control. Representative results of 3 experiments are shown. (D) Western blot analysis of caspase-3 and caspase-8 activation. Whole cell lysates from spleens of mice transplanted with MSCV-GFP or BCR-ABL⁺ LSCs that were treated with vehicle or Δ¹²-PGJ₃ (0.025 mg/kg) were probed with the indicated Abs. Lanes 1 through 4 represent MSCV-GFP⁺ HSC + vehicle, MSCV-GFP⁺ HSCs + Δ¹²-PGJ₃, BCR-ABL⁺LSC + vehicle, and BCR-ABL⁺LSC + Δ¹²-PGJ₃, respectively. Results shown are representative of n = 3 mice per group. (E) Analysis of the role of ATM in the Δ¹²-PGJ₃–dependent apoptosis of BCR-ABL–GFP⁺ LSCs. LSCs were pretreated with MTPO (50nM) or vehicle followed by the addition of Δ¹²-PGJ₃ (25nM). GFP⁺ and annexin V⁺ cells were analyzed using flow cytometry (n = 3). Shown are means ± SEM. (F) Analysis of p53 mRNA expression in BCR-ABL⁺ cells sorted from the spleens of mice transplanted with BCR-ABL⁺ LSCs followed by treatment with Δ¹²-PGJ₃ (25nM) alone or in combination with the ATM inhibitor MTPO (50nM). Representative results of 3 experiments are shown.