Figure 2

Azacytidine-mediated up-regulation of AQP9 expression and intracellular arsenic uptake. (A) AQP9 mRNA expression was significantly up-regulated with 5′Aza treatment in HL-60, K562, NB4, and OCI-AML3 cells, as determined by RT-PCR (upper panel) and quantitative RT-PCR (lower panel). Sample data were normalized to the control of each cell line individually by the ΔΔC_T method. (B) Up-regulation of membrane AQP9 protein expression was also confirmed by flow cytometric analysis. (C) Intracellular elemental arsenic concentration is significantly increased in K562 cells after pre-treatment with 5′Aza. (D) Treatment of K562 cells with HgCl₂ completely abrogated the cytotoxicity induced by As₂O₃, either alone (left panel) or in cells pre-treatment with 5′Aza (right panel).