Hypoxia mediates cellular iron deficiency by decreasing in LMW iron and ferritin levels. HepG2, MDA-MB-231, and MCF-7 cells were exposed to iron (100 μM FeSO4) immediately prior to hypoxia (1% O2). After 6 h treatment, LMW iron was determined by calcein assay (A) and ferritin levels by ELISA (B). Data points are means ± SD of four independent experiments (n = 4). * Significantly different from normoxic controls (p < 0.05). + Significantly different from respective normoxic or hypoxic controls without iron treatments (p < 0.05).