Expression of the hemochromatosis gene modulates the cytotoxicity of doxorubicin in breast cancer cells.
The antineoplastic agent doxorubicin inhibits cell growth through mechanisms that include an interaction with iron, resulting in the generation of cytotoxic reactive oxygen species (ROS). Prior studies have shown that the wild-type hemochromatosis gene (wt HFE) may downregulate iron uptake and alter iron homeostasis in cells. We therefore tested the hypothesis that expression of wt HFE would affect the cytotoxicity of doxorubicin. Human breast cancer MCF-7 cells were transfected with an expression plasmid for a FLAG-tagged wt HFE gene [fwtHFE(+) cells], to examine the impact of wt HFE expression on doxorubicin-induced apoptosis. Our results show that, in MCF-7 cells, fwtHFE expression resulted in a reduction in cellular iron uptake and a decrease in the growth inhibitory effects of doxorubicin. Two micromolar doxorubicin inhibited the growth of fwtHFE(+) and fwtHFE(-) MCF-7 cells by 34% and 61%, respectively. In parallel, doxorubicin induced caspase-3-like activity in fwtHFE(-) cells, but not in fwtHFE(+) cells. On analysis with a DCF fluorescence assay, ROS could be detected in fwtHFE(-) cells but not in fwtHFE(+) cells exposed to doxorubicin. Western blot analysis of breast biopsy samples from patients revealed immunoreactive HFE and transferrin receptor proteins in both normal and malignant breast tissues. Our studies suggest that HFE expression and its consequent effect on cellular iron homeostasis may modulate doxorubicin-induced oxidative stress and apoptosis in breast cancer cells. Further investigation is warranted to determine whether HFE expression in tumor cells impacts on the clinical efficacy of doxorubicin.