Aconitase 2 inhibits the proliferation of MCF-7 cells promoting mitochondrial oxidative metabolism and ROS/FoxO1-mediated autophagic response

Abstract

Background Deregulation of the tricarboxylic acid cycle (TCA) due to mutations in specific enzymes or defective aerobic metabolism is associated with tumour growth. Aconitase 2 (ACO2) participates in the TCA cycle by converting citrate to isocitrate, but no evident demonstrations of its involvement in cancer metabolism have been provided so far. Methods Biochemical assays coupled with molecular biology, in silico, and cellular tools were applied to circumstantiate the impact of ACO2 in the breast cancer cell line MCF-7 metabolism. Fluorescence lifetime imaging microscopy (FLIM) of NADH was used to corroborate the changes in bioenergetics. Results We showed that ACO2 levels are decreased in breast cancer cell lines and human tumour biopsies. We generated ACO2- overexpressing MCF-7 cells and employed comparative analyses to identify metabolic adaptations. We found that increased ACO2 expression impairs cell proliferation and commits cells to redirect pyruvate to mitochondria, which weakens Warburg-like bioenergetic features. We also demonstrated that the enhancement of oxidative metabolism was supported by mitochondrial biogenesis and FoxO1-mediated autophagy/mitophagy that sustains the increased ROS burst. Conclusions This work identifies ACO2 as a relevant gene in cancer metabolic rewiring of MCF-7 cells, promoting a different utilisation of pyruvate and revealing the potential metabolic vulnerability of ACO2-associated malignancies.

Iron: An Essential Element of Cancer Metabolism

“…Decreased mitochondrial aconitase ACO2 has been reported in gastric cancer, wherein it predicted poor prognosis, and in human breast tumor biopsies as well as breast cancer cell lines [88]. In addition, the induction of ACO2 enhanced mitochondrial oxidative metabolism and sustained ROS production, leading to reduced breast cancer cell proliferation [88]. A cytosolic isoform, more commonly termed iron-regulatory protein 1 (IRP1) or iron-responsive element binding protein (IRE-BP), exerts the same catalytic function but serves as a major iron-sensor and mRNA-binding protein, as discussed above [89].…”

“…The conformation of aconitase changes according to the ISC and determines its enzymatic activity: liaison with a [3Fe-4S] cluster is found in the inactive form, while the acquirement of an additional iron atom forming [4Fe-4S] activates the enzyme [86,87]. Decreased mitochondrial aconitase ACO2 has been reported in gastric cancer, wherein it predicted poor prognosis, and in human breast tumor biopsies as well as breast cancer cell lines [88]. In addition, the induction of ACO2 enhanced mitochondrial oxidative metabolism and sustained ROS production, leading to reduced breast cancer cell proliferation [88].…”

Antioxidants Targeting Mitochondrial Oxidative Stress: Promising Neuroprotectants for Epilepsy

“…Indeed, two of the respiratory chain complexes, namely complexes I (CI) and CIII, have been demonstrated, for a long time, to be involved in O 2 − production [ 17 , 18 ]. Mitochondrial ROS (mtROS) are also synthesized by several matrix proteins and complexes including enzymes of the TCA cycle (e.g., aconitase, pyruvate dehydrogenase, and α -ketoglutarate dehydrogenase) [ 19 – 22 ]. Additionally, numerous enzymatic reactions in mitochondria can also produce ROS, including those of glycerol-3-phosphate dehydrogenase, cytochrome P450, monoamine oxidase, and cytochrome b5 reductase.…”

Adipose Tissue and FoxO1: Bridging Physiology and Mechanisms

“…The interaction of β-catenin with FoxO is favored by oxidative stress and contributes to enhancing FoxO transcriptional activity at genes involved in resistance to oxidative damage in mammalian cells and C. elegans [80,81]. Reduced FoxO1 phosphorylation at S256 is associated with augmented ROS production in MCF-7 cancer cells overexpressing the mitochondrial aconitase, with consequences on autophagy induction [82]. JNK and nuclear translocation of FoxO1 has been shown to occur in endothelial cells and follicular granulosa cells upon oxidative stress [83,84].…”