Metabolic Reprogramming in Breast Cancer and Its Therapeutic Implications

Abstract

Current standard-of-care (SOC) therapy for breast cancer includes targeted therapies such as endocrine therapy for estrogen receptor-alpha (ERα) positive; anti-HER2 monoclonal antibodies for human epidermal growth factor receptor-2 (HER2)-enriched; and general chemotherapy for triple negative breast cancer (TNBC) subtypes. These therapies frequently fail due to acquired or inherent resistance. Altered metabolism has been recognized as one of the major mechanisms underlying therapeutic resistance. There are several cues that dictate metabolic reprogramming that also account for the tumors' metabolic plasticity. For metabolic therapy to be efficacious there is a need to understand the metabolic underpinnings of the different subtypes of breast cancer as well as the role the SOC treatments play in targeting the metabolic phenotype. Understanding the mechanism will allow us to identify potential therapeutic vulnerabilities. There are some very interesting questions being tackled by researchers today as they pertain to altered metabolism in breast cancer. What are the metabolic differences between the different subtypes of breast cancer? Do cancer cells have a metabolic pathway preference based on the site and stage of metastasis? How do the cell-intrinsic and -extrinsic cues dictate the metabolic phenotype? How do the nucleus and mitochondria coordinately regulate metabolism? How does sensitivity or resistance to SOC affect metabolic reprogramming and vice-versa? This review addresses these issues along with the latest updates in the field of breast cancer metabolism.

Keywords: breast cancer; estrogen receptors; metabolic reprogramming; metabolism; metabolism in metastatic cascade; mito-nuclear crosstalk; mitochondria; molecular subtypes; p53; precision medicine; resistance mechanisms; standard-of-care; tumor microenvironment.

Figure 1

Metabolic crosstalk between ERα and p53. Metabolic targets regulated by both p53 and ERα are shown. These targets maybe regulated in the same direction (yellow: activated or repressed), opposite direction (red: repressed by one and activated by the other) or are bi-directionally regulated (orange: both activated and repressed).

Figure 2

Metabolic interactions between the tumor and its microenvironment. T-cells, dendritic cells, and macrophages undergo metabolic reprogramming with different functional consequences (noted in the figure) that often propel tumor growth and progression.

Figure 3

Metabolic plasticity of cancer cells during metastatic cascade. Cancer cells may adopt different energy pathways, i.e., glycolysis or OXPHOS based on their stage in the metastatic cascade as well as the site to which they metastasize.