5-azaC down-regulates RRM2 expression ex vivo and in vivo. (A-B) 5-azaC inhibits RRM2 protein (A) and mRNA (B) expression in MV4-11 tumor xenografts in mice. Athymic nu/nu mice subcutaneously inoculated with MV4-11 cells were treated with 5-azaC and the engrafted tumor tissues were subjected to analysis. (C) 5-azaC reduces the RRM2 level in primary BM cells from AML patients. Primary cells from 6 patients were cultured in vitro and treated with the indicated concentrations of 5-azaC for 24 or 48 hours. Cells were then collected for Western blot and quantitative RT-PCR analyses. For Western blot analysis, densitometry was performed to quantify each lane, and the ratio of RRM2 over the loading control GAPDH is presented under each blot. For quantitative RT-PCR analysis, the data are presented as a percentage of the untreated controls. The results are means ± SD of the representative experiment performed in triplicate. *P < .05 and **P < .01 versus untreated controls.