Selective Disruption of Respiratory Supercomplexes as a New Strategy to Suppress Her2high Breast Cancer.

AIMS: Expression of the HER2 oncogene in breast cancer is associated with resistance to treatment, and Her2 may regulate bioenergetics. Therefore, we investigated whether disruption of the electron transport chain (ETC) is a viable strategy to eliminate Her2high disease. RESULTS: We demonstrate that Her2high cells and tumors have increased assembly of respiratory supercomplexes (SCs) and increased complex I-driven respiration in vitro and in vivo. They are also highly sensitive to MitoTam, a novel mitochondrial-targeted derivative of tamoxifen. Unlike tamoxifen, MitoTam efficiently suppresses experimental Her2high tumors without systemic toxicity. Mechanistically, MitoTam inhibits complex I-driven respiration and disrupts respiratory SCs in Her2high background in vitro and in vivo, leading to elevated reactive oxygen species production and cell death. Intriguingly, higher sensitivity of Her2high cells to MitoTam is dependent on the mitochondrial fraction of Her2. INNOVATION: Oncogenes such as HER2 can restructure ETC, creating a previously unrecognized therapeutic vulnerability exploitable by SC-disrupting agents such as MitoTam. CONCLUSION: We propose that the ETC is a suitable therapeutic target in Her2high disease. Antioxid. Redox Signal. 26, 84-103.

Indoleamine-2,3-dioxygenase elevated in tumor-initiating cells is suppressed by mitocans.

Tumor-initiating cells (TICs) often survive therapy and give rise to second-line tumors. We tested the plausibility of sphere cultures as models of TICs. Microarray data and microRNA data analysis confirmed the validity of spheres as models of TICs for breast and prostate cancer as well as mesothelioma cell lines. Microarray data analysis revealed the Trp pathway as the only pathway upregulated significantly in all types of studied TICs, with increased levels of indoleamine-2,3-dioxygenase-1 (IDO1), the rate-limiting enzyme of Trp metabolism along the kynurenine pathway. All types of TICs also expressed higher levels of the Trp uptake system consisting of CD98 and LAT1 with functional consequences. IDO1 expression was regulated via both transcriptional and posttranscriptional mechanisms, depending on the cancer type. Serial transplantation of TICs in mice resulted in gradually increased IDO1. Mitocans, represented by α-tocopheryl succinate and mitochondrially targeted vitamin E succinate (MitoVES), suppressed IDO1 in TICs. MitoVES suppressed IDO1 in TICs with functional mitochondrial complex II, involving transcriptional and posttranscriptional mechanisms. IDO1 increase and its suppression by VE analogues were replicated in TICs from primary human glioblastomas. Our work indicates that IDO1 is increased in TICs and that mitocans suppress the protein.

Progressive loss of dopaminergic neurons induced by unilateral rotenone infusion into the medial forebrain bundle.

Rotenone, a mitochondrial complex 1 inhibitor, causes oxidative damage via production of reactive oxygen species. We examined the pathophysiology of neuronal and glial cells of the nigrostriatal pathway following unilateral infusion of varying doses of rotenone into the substantia nigra or medial forebrain bundle of adult male Sprague-Dawley rats, sacrificed 14 and 60 days after infusion. Immunofluorescence techniques were used to qualitatively and quantitatively assay dopaminergic neurons, their projections, glial cells, synapses, and oxidative stress. Rotenone infusion into the substantia nigra at all concentrations caused extensive damage and tissue necrosis, therefore of limited relevance for producing a Parkinson disease model. Infusion of 0.5µg of rotenone targeting the medial forebrain bundle induced oxidative stress in dopaminergic neurons causing ongoing cell stress as defined by an elevation of stress granule and oxidative stress markers. This treatment resulted in the loss of tyrosine hydroxylase immunoreactive cells in the substantia nigra (p≤0.01) and loss of tyrosine hydroxylase immunoreactive nerve fibres and synaptic specialisations in the striatum (p≤0.01). The infusion of 0.5µg of rotenone also caused an increase in astrocytes and microglial cells in the substantia nigra in comparison to control (p≤0.01). We examined the time-dependent reduction of tyrosine hydroxylase-positive nerve fibres and cell bodies in the striatum and substantia nigra respectively, with a progressive reduction evident 60days after infusion (p≤0.01, p≤0.05). Dopaminergic axons exposed to low-dose rotenone undergo oxidative stress, with a resultant ongoing loss of dopaminergic neurons, providing an animal model relevant to Parkinson disease.