Treatment with AZA restores sensitivity to GCs in Molt-4 cells. A. Molt-4 cells treated for 48 hours with DMSO or 100 nM AZA were cloned by serial dilution to single cells and viable cell populations were allowed to regrow. % growth repression and residual apoptotic cells after 96 hours of 1 μM Dex treatment for control (49 clones, open diamonds) or AZA (49 clones, closed squares) are plotted. Upon further culture, the Dex-sensitivity of these clones proved to be unstable; therefore in B-D, experiments were performed on the MOLT-4 mass culture. B. DNA methylation of uncloned Molt-4 cells treated with DMSO vehicle or 100 nM AZA for 48 h. Data show DPMs of incorporated 3H dCTP per μg of genomic DNA. Error bars = 1 SD, n = 5. p = 0.001, DMSO vs. AZA C. Timing of response to Dex. Molt-4 cells were treated in triplicate with vehicle (control, closed squares), 1 μM Dex (open squares), 100 nM AZA (closed triangles), or 100 nM AZA for 24 hours before adding 1 μM Dex (open triangles). Average percentage of 3 independent replicates for cell culture viability following the addition of Dex. Sensitive clone CEM-C7-14 (C7-14, dashed line, closed triangles, data from Figure 1C) included for comparison. Error bars = 1 SD. D. Flow cytometry of uncloned MOLT-4 cells treated with AZA, Dex or AZA followed by Dex. Cells were treated as in C. with evaluation by PI staining and flow cytometry 72 hours after Dex. Each histogram (all histograms are same scale) results from the collection of 20,000 “events” where possible. n = 1. Extensive cell loss caused lower number of “events” in lower right hand histogram. Cytometric evaluations, Table 1.