Impairment of HIF-1α-mediated metabolic adaption by NRF2-silencing in breast cancer cells

Sujin Lee,Steffanus Pranoto Hallis,Kyeong-Ah Jung,Dayoung Ryu,Mi-Kyoung Kwak

doi:10.1016/j.redox.2019.101210

Sujin Lee, Steffanus Pranoto Hallis + Show 3 more

Open Access

https://doi.org/10.1016/j.redox.2019.101210

Copy DOI

Abstract

Hypoxia, a common element in the tumor environment, leads to Hypoxia-Inducible Factor-1α (HIF-1α) stabilization to modulate cellular metabolism as an adaptive response. In a previous study, we showed that inhibition of the nuclear factor erythroid 2-like-2 (NFE2L2; NRF2), a master regulator of many genes coping with electrophilic and oxidative stress, elevated the level of miR-181c and induced mitochondrial dysfunction in colon cancer cells. In this study, we demonstrate that NRF2-silencing hindered HIF-1α accumulation in hypoxic breast cancer cells and subsequently suppressed hypoxia-inducible expression of glycolysis-associated glucose transporter-1, hexokinase-2, pyruvate dehydrogenase kinase-1, and lactate dehydrogenase A. HIF-1α dysregulation in NRF2-silenced cancer cells was associated with miR-181c elevation. Overexpression of miR-181c in breast cancer cells blocked HIF-1α accumulation and diminished hypoxia-inducible levels of glycolysis enzymes, whereas the inhibition of miR-181c in NRF2-silenced cells restored HIF-1α accumulation. In a subsequent metabolomic analysis, hypoxic incubation increased the levels of metabolites involved in glycolysis and activated the pentose phosphate pathway (PPP) in control cells. However, these elevations were less pronounced in NRF2-silenced cells. In particular, hypoxic incubation increased the levels of amino acids, which implies a shift to catabolic metabolism, and the increased levels were higher in control cells than in NRF2-silenced cells. Concurrently, hypoxia activated BCL2 interacting protein 3 (BNIP3)-mediated autophagy in the control cells and miR-181c was found to be involved in this autophagy activation. Taken together, these results show that hypoxia-induced metabolic changes to glycolysis, the PPP, and autophagy are inhibited by NRF2-silencing through miR-181c-mediated HIF-1α dysregulation. Therefore, targeting NRF2/miR-181c could be an effective strategy to counteract HIF-1α-orchestrated metabolic adaptation of hypoxic cancer cells.

Highlights

Hypoxia-inducible factor-1 (HIF-1) senses cellular oxygen (O2) levels and induces an adaptive response to hypoxia by upregulating an array of genes associated with angiogenesis, cell growth, and glycolytic metabolism [1,2]
Hypoxia-Inducible Factor-1α (HIF-1α) accumulation and hypoxia-induced levels of glycolysis-associated proteins such as glucose transporter-1 (GLUT1), HK2, pyruvate dehydrogenase kinase-1 (PDK1), and lactate dehydrogenase A (LDHA) were significantly diminished in hypoxic miR181c MCF-7 and MDA-MB-231 when compared to the cell lines in normoxia (Fig. 2C)
The introduction of a miR-181c inhibitor in NRF2-silenced breast cancer cells restored HIF-1α accumulation and HK2 elevation following hypoxic incubation (Fig. 2F and G). These results clearly show that miR-181c elevation is a molecular mediator for the dysregulation HIF-1α signaling in NRF2-silenced breast cancer cells

Summary

Introduction

Hypoxia-inducible factor-1 (HIF-1) senses cellular oxygen (O2) levels and induces an adaptive response to hypoxia by upregulating an array of genes associated with angiogenesis, cell growth, and glycolytic metabolism [1,2]. In the presence of normal O2 levels, the stability of the HIF-1α protein is regulated by prolyl hydroxylases domain protein (PHD)-mediated hydroxylation at the Pro402 and Pro564 residues and the Von Hippel-Lindau protein (VHL)-mediated proteasomal degradation [2,4,5]. In this reaction, O2 is used as a substrate of PHDs and, the hypoxic condition causes inhibition of the PHD-mediated hydroxylation and VHL-mediated degradation of HIF1α. HIF-1α accumulation directly upregulates glucose transporter-1 (GLUT1), a transporter for cellular

Methods

Results

Conclusion