Treatment of wild-type, R38+ and R38− HL-60 with the AhR agonist FICZ. Wild-type (WT), R38+ and R38− were treated for 48 h with RA or RA and the AhR agonist FICZ and analyzed by flow cytometry for (A) CD38 expression, (B) CD11b expression, or (C) G1/G0 cell cycle arrest. Asterisks for p-values of treatment group means compared to control indicate whether p < 0.0001 (****), p < 0.001 (***), p < 0.01 (**) or p < 0.05 (*). FICZ treatment does not significantly rescues (A) CD38 expression, (B) CD11b expression or (C) G1/G0 cell cycle arrest in either RA-resistant cell line.