HFE Variants and the Expression of Iron-Related Proteins in Breast Cancer-Associated Lymphocytes and Macrophages

Iron is an essential functional element for several biologic processes, such as energy production and intermediate metabolism. However, when in excess, it can be toxic and produce free radicals. As a fundamental element involved in cell metabolism, division and proliferation, iron has been implicated as an important player in cancer development. Iron is thought to promote carcinogenesis through iron-induced oxidative stress, modulation of signaling networks associated with malignancy and by providing selective advantage to rapidly growing tumor cells. From the cell biology perspective, it is well accepted that the malignant state in breast epithelial cells is characterized by a deregulation in cellular iron homeostasis. We have previously shown that the deregulation of iron-related proteins in breast cancer, more specifically hepcidin, ferroportin 1 (FPN1), TfR1 (Transferrin Receptor 1) and ferritin (FT), is not restricted to epithelial cells, but also extends to cells of the tumor microenvironment, and is associated with clinicopathological markers of breast cancer poor prognosis, such as negative hormone receptor status and tumor size.

HFE (High Iron Fe) is a MHC (Major Histocompatibility Complex) class-I like protein that acts as a gatekeeper of systemic iron homeostasis by controlling hepatic hepcidin levels. Hepcidin, in turn, maintains normal plasma iron levels by regulating iron release from cells through the binding to its receptor, the iron exporter ferroportin 1. HFE gene variants p.Cys282Tyr and p.His63Asp are very common in European derived populations. The p.Cys282Tyr variant disrupts the association of HFE with β-2 microglobulin, reducing the cellular surface expression of HFE. This alteration is responsible for the large majority of hereditary hemochromatosis cases. The p.His63Asp variant is believed to lower the HFE protein affinity for TfR1. The association of HFE major variants with breast cancer risk and behavior has been a matter of discussion for a long time. However, their impact on the expression of iron-related proteins in the breast cancer tissue has never been addressed. In the present study, hepcidin, FPN1, TfR1, and ferritin expressions, as well as tissue iron deposition were evaluated in a collection of samples from breast cancers patients and analyzed according to the patients’ HFE genotype. Within the group of patients with invasive carcinoma, those carrying the p.Cys282Tyr variant in heterozygosity presented a higher expression of hepcidin in lymphocytes and macrophages than wild-type or p.His63Asp carriers. An increased expression of TfR1 was also observed in all the cell types analyzed but only in p.Cys282Tyr/p.His63Asp compound heterozygous patients. A differential impact of the two HFE variants was further noticed with the observation of a significantly higher percentage of p.Cys282Tyr heterozygous patients presenting tissue iron deposition in comparison to p.His63Asp heterozygous. In the present cohort, no significant associations were found between HFE variants and classical clinicopathological markers of breast cancer behavior and prognosis. Although limited by a low sampling size, our results provide a new possible explanation for the previously reported impact of HFE major variants on breast cancer progression, i.e., not by influencing systemic iron homeostasis but rather by differentially modulating the local cellular expression of iron-related proteins and tissue iron deposition.

Authors and Affiliations:

Oriana Marques^1,2,3,4,5; Ana Rosa^3,4,5; Luciana Leite³; Paula Faustino^6,7; Alexandra Rêma³; Berta Martins da Silva^1,3; Graça Porto^3,4,5,8; Carlos Lopes^3,9

¹Unit for Multidisciplinary Biomedical Research (UMIB), Institute of Biomedical Sciences Abel Salazar (ICBAS), University of Porto, Porto, Portugal

²Lab Immunogenetics & Autoimmu and NeuroScien, UMIB, ICBAS, University of Porto, Porto, Portugal

³Pathology and Molecular Immunology Department, Institute of Biomedical Sciences Abel Salazar (ICBAS), University of Porto, Porto, Portugal

⁴Basic and Clinical Research on Iron Biology, Molecular and Cell Biology Institute (IBMC), University of Porto, Porto, Portugal

⁵Instituto de Investigação e Inovação em Saúde (i3S), University of Porto, Porto, Portugal

⁶Human Genetics Department, National Institute of Health Dr. Ricardo Jorge, Lisbon, Portugal

⁷Institute of Environmental Health, Faculty of Medicine, University of Lisbon, Lisbon, Portugal

⁸Hematology Service, Hospital de Santo António, Centro Hospitalar do Porto, Porto, Portugal

⁹Department of Pathology, Portuguese Oncology Institute (IPO), Porto, Portugal

Abstrac:

The association of HFE (High Iron FE) major variants with breast cancer risk and behavior has been a matter of discussion for a long time. However, their impact on the expression of iron-related proteins in the breast cancer tissue has never been addressed. In the present study, hepcidin, ferroportin 1, transferrin receptor 1 (TfR1), and ferritin expressions, as well as tissue iron deposition were evaluated in a collection of samples from breast cancers patients and analyzed according to the patients’ HFE genotype. Within the group of patients with invasive carcinoma, those carrying the p.Cys282Tyr variant in heterozygosity presented a higher expression of hepcidin in lymphocytes and macrophages than wild-type or p.His63Asp carriers. An increased expression of TfR1 was also observed in all the cell types analyzed but only in p.Cys282Tyr/p.His63Asp compound heterozygous patients. A differential impact of the two HFE variants was further noticed with the observation of a significantly higher percentage of p.Cys282Tyr heterozygous patients presenting tissue iron deposition in comparison to p.His63Asp heterozygous. In the present cohort, no significant associations were found between HFE variants and classical clinicopathological markers of breast cancer behavior and prognosis. Although limited by a low sampling size, our results provide a new possible explanation for the previously reported impact of HFE major variants on breast cancer progression, i.e., not by influencing systemic iron homeostasis but rather by differentially modulating the local cellular expression of iron-related proteins and tissue iron deposition.

Journal: Cancer Microenvironment

Link: https://link.springer.com/article/10.1007/s12307-016-0191-4