Induction of AQP9 expression with ATRA treatment of HL-60 cells. (A) Semiquantitative polymerase chain reaction showed that the expression of AQP9 gene in HL-60 was significantly induced after 48-hour incubation of 100 nM, 1 μM, and 10μM ATRA. β-actin gene was used as internal control of the RT-PCR. Western-blot analysis also showed increasing AQP9 protein expression (about 30 kDa) with increasing concentrations of ATRA. The loading amount of protein samples was standardized by PointSau staining. (B) In MTT assay, HL-60 cells pretreated with 100 μM ATRA for 48 hours exhibited an increased sensitivity to the cytotoxicity of As2O3 compared with the untreated control. (C) In arsenic-uptake assay, HL-60 cells pretreated with 100 μM ATRA for 48 hours were incubated with 1 μM As2O3. There was a time-dependent increase in arsenic uptake compared with the untreated control (Student t test for each of the points analyzed).
