ATO induces expression of CCL2 and CCL7 in NB4 cells. NB4 cells were cultured in medium in the presence or absence of ATRA (10⁻⁶ M), ATO (10⁻⁶ M), or their combination for 0, 4, 8, 24, 48, 72, and 96 hours. (A) CCL mRNA expression was determined at the indicated time points by quantitative PCR. Expression relative to GAPDH is plotted. (B) CCL protein levels were determined in supernatant of NB4 cells at the indicated time points using ELISA. MDD indicates minimal detectable dose, according to the manufacturer.