Biology subjects

Eaton, J. K.

Publications and source records attributed to Eaton, J. K..

7 recordsLinked to original sources

bioRxiv2024

Assessing the Impact of Valve Sizing and Orientation on Bioprosthetic Pulmonary Valve Hemodynamics Using In Vitro 4D-Flow MRI

PurposePulmonary valve replacement (PVR) using bioprosthetic valves is a common procedure performed in patients with repaired Tetralogy of Fallot and other conditions, but these valves frequently become dysfunctional within 15 years of implantation. Since PVR is often performed in adolescence, valves are typically oversized to account for somatic growth. However, the contribution of oversizing to early valve failure are not clearly understood. The purpose of this study was to explore the impact of valve sizing and orientation on local hemodynamics and valve performance. MethodsDifferent valve sizes were represented by changing the cardiac output through a 25 mm bioprosthetic valve implanted in an idealized 3D-printed model of the right ventricular outflow tract (RVOT). The local hemodynamics at three valve sizes and two valve orientations were assessed using 4D-Flow MRI and high-speed camera imaging. ResultsNoticeable differences in jet asymmetry, the amount of recirculation, leaflet opening patterns, as well as the size and location of reversed flow regions were observed with varying valve sizes. Rotation of the valve resulted in drastic differences in reversed flow regions, but not forward flow. ConclusionFlow features observed in the oversized valve in this study have previously been correlated with calcification, hemolysis, and leaflet fatigue. Therefore, valve oversizing can negatively impact local hemodynamics and leaflet performance.

bioengineering↗

bioRxiv2024

The enzyme glutamate-cysteine ligase (GCL) is a target for ferroptosis induction in cancer

Despite glutathiones long-recognized role as a major cellular antioxidant and its central role in ferroptosis defense, inhibition of glutathione biosynthetic enzymes has received little attention as a target for the therapeutic induction of ferroptosis. Here, we report that small-molecule inhibition of glutamate-cysteine ligase (GCL), the rate-limiting enzyme of glutathione biosynthesis, selectively and potently kills cancer cells by ferroptosis. We further describe novel GCL inhibitors including KOJ-1 and KOJ-2, compounds with excellent cellular potency and pharmacological properties, representing valuable tools to study the biology of ferroptosis and glutathione.

cancer biology↗

bioRxiv2024

Validation of ferroptosis in canine cancer cells to enable comparative oncology and translational medicine

Ferroptosis is a cell death mechanism that has attracted significant attention as a potential basis for the development of new cancer therapies. Validation of ferroptosis biology in species commonly used in translation and pre-clinical development is a necessary foundation for enabling the advancement of such ferroptosis modulating drugs. Here, we demonstrate that canine cancer cells exhibit sensitivity to a wide range of ferroptosis-inducing perturbations in a manner indistinguishable from human cancer cells, and recapitulate characteristic patterns of ferroptotic response across tumor types seen in the human setting. The foundation provided herein establishes the dog as a relevant efficacy and toxicology model for ferroptosis and creates new opportunities to leverage the canine comparative oncology paradigm to accelerate the development of ferroptosis-inducing drugs for human cancer patients.

cancer biology↗

bioRxiv2024

Commonly used organoid culture media prevent ferroptosis

Organoids enable the recreation of organ physiology in vitro and serve as powerful models for biology in basic life science research and drug discovery and development. However, organoid culture requires complex media formulations that include antioxidants, potentially confounding experimental results sensitive to such conditions. Here we report that the growth conditions used commonly to generate organoid models inhibit ferroptosis, an iron-dependent form of lipid peroxidative cell death with relevance to human disease, thus rendering such models incompatible with ferroptosis research. We identify medium components that diminish or eliminate ferroptosis sensitivity and outline strategies for avoiding anti-ferroptotic culture conditions in organoid and other cell culture applications. These findings provide a roadmap for adapting organoid models for the study of ferroptosis and leveraging their strengths for advancing ferroptosis-modulating therapeutics.

cancer biology↗

bioRxiv2020

Modulation of ferroptosis sensitivity by TXNRD1 in pancreatic cancer cells

AO_SCPLOWBSTRACTC_SCPLOWThe selenoprotein thioredoxin reductase 1 (TXNRD1) plays a central role in ameliorating oxidative stress. Inhibition of TXNRD1 has been explored as a means of killing cancer cells that are thought to develop an enhanced reliance on such antioxidant proteins. In the context of ferroptosis, a non-apoptotic form of oxidative cell death, TXNRD1 has been proposed to cooperate with the phospholipid hydroperoxidase enzyme glutathione peroxidase 4 (GPX4) to protect cells from the lethal accumulation of lipid peroxides. Here, we report our unexpected finding that in pancreatic cancer cells, CRISPR-Cas9-mediated loss of TXNRD1 confers protection from ferroptosis induced by small-molecule inhibition of GPX4. Insights stemming from mechanistic interrogation of this phenomenon suggest that loss of TXNRD1 results in increased levels of GPX4 protein, potentially by influencing availability of selenocysteine, a scarce amino acid required by both proteins for proper synthesis and function. Increased abundance of GPX4 protein, in turn, protects cells from the effects of small-molecule GPX4 inhibition. These findings implicate selenoprotein regulation in governing ferroptosis sensitivity. Furthermore, by delineating a relationship between GPX4 and TXNRD1 contrary to that observed in numerous other settings, our discoveries underscore the context-specific nature of ferroptosis circuitry and its modulators.

cell biology↗

bioRxiv2018

HIF-2α drives an intrinsic vulnerability to ferroptosis in clear cell renal cell carcinoma

Kidney cancers are characterized by extensive metabolic reprogramming and resistance to a broad range of anti-cancer therapies. By interrogating the Cancer Therapeutics Response Portal compound sensitivity dataset, we show that cells of clear-cell renal cell carcinoma (ccRCC) possess a lineage-specific vulnerability to ferroptosis that can be exploited by inhibiting glutathione peroxidase 4 (GPX4). Using genome-wide CRISPR screening and lipidomic profiling, we reveal that this vulnerability is driven by the HIF-2-HILPDA pathway by inducing a polyunsaturated fatty acyl (PUFA)-lipid-enriched cell state that is dependent on GPX4 for survival and susceptible to ferroptosis. This cell state is developmentally primed by the HNF-1{beta}-1-Acylglycerol-3-Phosphate O-Acyltransferase 3 (AGPAT3) axis in the renal lineage. In addition to PUFA metabolism, ferroptosis is facilitated by a phospholipid flippase TMEM30A involved in membrane topology. Our study uncovers an oncogenesis-associated vulnerability, delineates the underlying mechanisms and suggests targeting GPX4 to induce ferroptosis as a therapeutic opportunity in ccRCC.\n\nHIGHLIGHTSO_LIccRCC cells exhibit strong susceptibility to GPX4 inhibition-induced ferroptosis\nC_LIO_LIThe GPX4-dependent and ferroptosis-susceptible state in ccRCC is associated with PUFA-lipid abundance\nC_LIO_LIThe HIF-2-HILPDA axis promotes the selective deposition of PUFA-lipids and ferroptosis susceptibility\nC_LIO_LIAGPAT3 selectively synthesizes PUFA-phospholipids and primes renal cells for ferroptosis\nC_LI

cancer biology↗

bioRxiv2018

Targeting a Therapy-Resistant Cancer Cell State Using Masked Electrophiles as GPX4 Inhibitors

We recently discovered that inhibition of the lipid peroxidase GPX4 can selectively kill cancer cells in a therapy-resistant state through induction of ferroptosis. Although GPX4 lacks a conventional druggable pocket, covalent small-molecule inhibitors are able to overcome this challenge by reacting with the GPX4 catalytic selenocysteine residue to eliminate enzymatic activity. Unfortunately, all currently-reported GPX4 inhibitors achieve their activity through reactive chloroacetamide groups. We demonstrate that such chloroacetamide-containing compounds are poor starting points for further advancement given their promiscuity, instability, and low bioavailability. Development of improved GPX4 inhibitors, including those with therapeutic potential, requires the identification of new electrophilic chemotypes and mechanisms of action that do not suffer these shortcomings. Here, we report our discovery that nitrile oxide electrophiles, and a set of remarkable chemical transformations that generates them in cells from masked precursors, provide an effective strategy for selective targeting of GPX4. Our results, which include structural insights, target engagement assays, and diverse GPX4-inhibitor tool compounds, provide critical insights that may galvanize development of improved compounds that illuminate the basic biology of GPX4 and therapeutic potential of ferroptosis induction. In addition, our discovery that nitrile oxide electrophiles engage in highly selective cellular interactions and are bioavailable in their masked forms may be relevant for targeting other currently undruggable proteins, such as those revealed by recent proteome-wide ligandability studies.

biochemistry↗