Sex differences in glioblastoma (GBM) incidence and survival are well documented but the underlying mechanisms are not well understood, resulting in lack of clinical guidance for therapeutic strategies. The proposed mechanisms for these sex differences include cell intrinsic and systemic factors. Iron is uniquely positioned as a critical cell intrinsic factor whose systemic levels impact tumor burden and whose bioavailability is influenced by sex. Iron is required for the regulation of metabolism, gene expression, macrophage/microglial function, and global immune status. Due to the critical importance of iron in biological systems, there are multiple homeostatic cell and molecular pathways that must be coordinated, which include complementary communication among different cell types in the tumor microenvironment. This complex biological regulatory system is collectively defined as the tumor iron signature. We observed that expression of the iron homeostatic regulator gene (HFE), which is a key regulator of iron uptake by all cells, predicts prognosis in female but not male GBM patients. In addition, extrinsic factors such as circulating levels of ferritin in the cerebrospinal fluid are associated with poor outcomes in GBM, likely related to our new finding that H-ferritin binds to cells in the GBM as part of a sex-specific GBM iron signature. While the iron status influences gliomagenesis, iron homeostatic pathways have specific sex-based challenges, such as higher incidence of anemia in women, that are under- appreciated in the context of cancer and the focus of this project. Based on published data in multiple cancers and our published and preliminary data, we hypothesize that sex differences in the regulation of both host and cellular iron status will impact cell-intrinsic metabolism, gene expression, cell:microenvironment interactions and gliomagenesis. The objective of this proposal is to characterize the iron signature of GBM in humans and then to leverage these data to interrogate mouse and cell culture models to identify the mechanisms by which the iron signature in the GBM is established and modified by cell intrinsic and environmental factors. We will test our hypothesis through two specific aims:
Specific Aim 1 will test the hypothesis that sex-specific complementary iron regulation signatures are present in tumor cells and the GBM microenvironment;
Specific Aim 2 will test the hypothesis that the iron signature of GBM displays sexual dimorphism and drives tumor growth through integration of cell-intrinsic and cell-extrinsic iron-mediated interactions. These studies complement the other P01 projects on genetic/epigenetic features (Project 1) and tumor microenvironment associated inflammation states (Project 3) by bridging cell intrinsic versus cell extrinsic tumorigenic programs through a common mechanism, iron metabolism.
Iron is essential for a multitude of biological processes and in cancer, iron concomitantly drives tumor cell proliferation and immune suppression in the tumor microenvironment. As part of a Program Project grant on sex differences in glioblastoma (GBM), this project will define the mechanisms by which sex-specific microenvironmental interactions, including differences in iron metabolism (tumor and host), microglia, and macrophages, alter the dynamics of GBM growth. This project provides an opportunity to bridge mechanisms by which iron impacts the epigenetic state (Project 1) and microglial and immune cell activation (Project 3).
