Kinetic modeling of H2O2 dynamics in the mitochondria of HeLa cells.

Hydrogen peroxide (H2O2) promotes a range of phenotypes depending on its intracellular concentration and dosing kinetics, including cell death. While this qualitative relationship has been well established, the quantitative and mechanistic aspects of H2O2 signaling are still being elucidated. Mitochondria, a putative source of intracellular H2O2, have recently been demonstrated to be particularly vulnerable to localized H2O2 perturbations, eliciting a dramatic cell death response in comparison to similar cytosolic perturbations.

A xenograft and cell line model of SDH-deficient pheochromocytoma derived from Sdhb+/- rats.

Tumors caused by loss-of-function mutations in genes encoding TCA cycle enzymes have been recently discovered and are now of great interest. Mutations in succinate dehydrogenase (SDH) subunits cause pheochromocytoma/paraganglioma (PCPG) and syndromically associated tumors, which differ phenotypically and clinically from more common SDH-intact tumors of the same types. Consequences of SDH deficiency include rewired metabolism, pseudohypoxic signaling and altered redox balance.

Mitochondrial HO Generation Using a Tunable Chemogenetic Tool To Perturb Redox Homeostasis in Human Cells and Induce Cell Death.

Among reactive oxygen species (ROS), HO alone acts as a signaling molecule that promotes diverse phenotypes depending on the intracellular concentration. Mitochondria have been suggested as both sources and sinks of cellular HO, and mitochondrial dysfunction has been implicated in diseases such as cancer. A genetically encoded HO generator, d-amino acid oxidase (DAAO), was targeted to the mitochondria of human cells, and its utility in investigating cellular response to a range of HO doses over time was assessed.

A unique model for SDH-deficient GIST: an endocrine-related cancer.

We describe a unique patient-derived xenograft (PDX) and cell culture model of succinate dehydrogenase-deficient gastrointestinal stromal tumor (SDH-deficient GIST), a rare mesenchymal tumor that can occur in association with paragangliomas in hereditary and non-hereditary syndromes. This model is potentially important for what it might reveal specifically pertinent to this rare tumor type and, more broadly, to other types of SDH-deficient tumors. The primary tumor and xenografts show a very high proliferative fraction, and distinctive morphology characterized by tiny cells with marked autophagic activity.

Modulating and Measuring Intracellular HO Using Genetically Encoded Tools to Study Its Toxicity to Human Cells.

Reactive oxygen species (ROS) such as HO play paradoxical roles in mammalian physiology. It is hypothesized that low, baseline levels of HO are necessary for growth and differentiation, while increased intracellular HO concentrations are associated with pathological phenotypes and genetic instability, eventually reaching a toxic threshold that causes cell death. However, the quantities of intracellular HO that lead to these different responses remain an unanswered question in the field.

Interpreting Heterogeneity in Response of Cells Expressing a Fluorescent Hydrogen Peroxide Biosensor.

Fluorescent, genetically encoded sensors of hydrogen peroxide have enabled visualization of perturbations to the intracellular level of this signaling molecule with subcellular and temporal resolution. Ratiometric sensors hold the additional promise of meaningful quantification of intracellular hydrogen peroxide levels as a function of time, a longstanding goal in the field of redox signaling. To date, studies that have connected the magnitudes of observed ratios with peroxide concentrations have either examined suspensions of cells or small numbers of adherent cells (∼10).