HO-1 overexpression decreases TfR expression and iron uptake in differentiated MEL cells. (A) qRT-PCR showing TfR mRNA of MEL (control) and MELHO-1 cells before (0 hours) and after (72 hours) induction with DMSO. (B) Flow cytometry analysis showing cell membrane TfR levels of DMSO-treated controls and induced MELHO-1 cells. (C) MEL cells were differentiated for 72 hours and, 3 hours before harvest, incubated with ⁵⁹Fe-Tf, after which heme and non-heme fractions were isolated (see the “Materials and methods” section). (D) MEL cells were differentiated for 72 hours and 3 hours before harvest; they were then incubated with increasing amounts of ⁵⁹Fe-SIH. Error bars of graphs represent standard deviation of 3 independent experiments (n = 3). *P < .05; **P < .001.