P5-05-06: Dysregulation in the Transport of Iron and Haem Is Implicated in the Aetiopathogenesis of Breast Cancer.

Abstract

Abstract Backround: Mounting evidence implicates iron in the development of a number of cancers, including breast. The responsible mechanism is poorly understood in breast cancer, although recent work has demonstrated irregular expression of various molecular iron transporters. Materials and Methods: Immunohistochemistry on archived material was used to evaluate differences in expression of iron and haem exporters, importers and storage proteins between breast cancer, DCIS and normal breast tissue. The results were corroborated by Western blotting and RT-qPCR on protein and RNA samples generated from matched normal and cancer specimens collected at mastectomy. The ability of benign and malignant breast cells in vitro to accumulate excess iron in the presence of exogenous iron/haem was evaluated with a ferrozine assay. In addition the effect of exogenous iron and haem on cell phenotype in vitro was assessed in benign and malignant cell lines. Assays utilised included viability (MTT), proliferation (BrdU), migration, anchorage-independent growth (colony formation) and invasive capacity. These assays were then repeated in the presence of iron chelators to investigate their potential utility as a therapeutic modality. Results: Statistically significant increases (p<0.05) were observed in expression of the iron importers DCytB, DMT1 and TfR in breast cancer relative to normal tissue. Levels of the storage protein ferritin were also significantly raised. The iron exporters ferroportin and hephaestin were significantly under-expressed in breast cancer, while hepcidin (which induces exporter degradation) was over-expressed. Levels of the haem importer HCP1 and the exporters BCRP and FLVCR were all significantly down-regulated in cancer relative to normal. Both benign and malignant breast cells were capable of importing excess iron, although only malignant cells could import excess haem. Iron induced increased viability and proliferation in benign cells but had no effect on their migratory or invasive capability, or their ability to form colonies. Haem had no effect on benign cell phenotype. Iron and haem both had significantly positive effects on all these aspects of cell phenotype when introduced to malignant breast cells in vitro. Iron chelators were capable of abrogating these positive effects. Discussion: Archived material and prospectively collected matched tissue pairs demonstrate that breast cancers exhibit altered expression of the proteins involved in transporting iron and haem through the cell. In vitro experiments reveal malignant cells to be capable of taking up both substances, which both appear to drive a more malignant phenotype. These in vitro changes can be reversed through the introduction of iron chelators, implying possible efficacy as a novel therapy in breast cancer. Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P5-05-06.