YM155 Induces DNA Damage and Cell Death in Anaplastic Thyroid Cancer Cells by Inhibiting DNA Topoisomerase IIα at the ATP-Binding Site

Anaplastic thyroid cancer (ATC) is among the most aggressive of human cancers, and currently there are few effective treatments for most patients. YM155, first identified as a survivin inhibitor, was highlighted in a high-throughput screen performed by the National Cancer Institute, killing ATC cells in vitro and in vivo. However, there was no association between survivin expression and response to YM155 in clinical trials, and YM155 has been mostly abandoned for development despite favorable pharmacokinetic and toxicity profiles. Currently, alternative mechanisms are being explored for YM155 by a number of groups. In this study, ATC patient samples show overexpression of topoisomerase Top2α compared with benign thyroid samples and to differentiated thyroid cancers. ATC cell lines that overexpress Top2α are more sensitive to YM155. We created a YM155-resistant cell line, which shows decreased expression of Top2α and is resensitized with Top2α overexpression. Molecular modeling predicts binding for YM155 in the Top2α ATP-binding site and identifies key amino acids for YM155-Top2α interaction. A Top2α mutant abrogates the effect of YM155, confirming the contribution of Top2α to YM155 mechanism of action. Our results suggest a novel mechanism of action for YM155 and may represent a new therapeutic approach for the treatment of ATC.

Abstract 453: Investigating The Role Of Glutathione During Macrophage Apoptotic Cell Clearance

Atherosclerosis (ASVD) is characterized by the buildup of lipids and fibrous elements in large arteries creating a plaque. As it progresses, apoptotic cells (AC) accumulate forming a necrotic core making the plaque unstable and prone to rupture. Rupture can lead to artery occlusion and moreover to stroke or myocardial infarction (MI). A main contributor to a large necrotic core is the inability of macrophages to clear accumulated AC and as a result undergo secondary necrosis. This clearance process, referred to as efferocytosis, is impaired in advanced atherosclerotic lesions. It has been shown that the process that leads to a thin fibrous cap and a large necrotic core are accelerated by a decrease in glutathione (GSH) availability by a deletion of the modifier subunit of Glutamate Cysteine Ligase (GCLM) in mice. Additionally, it has also been shown that a single nucleotide polymorphism (SNP) in the promoter region of human GCLM (-588 C/T) has an increased risk for MI. Our objective is to identify the role and mechanism of the GCLM SNP during the formation of the necrotic core in atherosclerosis. We hypothesize that proper function of GCLM and GSH is important in macrophages for adequate function and clearance of AC in ASVD.

Methods: Human peripheral blood mononuclear cells (PBMCs) were isolated from blood donors, genotyped to test for the presence of SNP, and used for RNA sequencing. Efferocytic index was measured using labelled AC in GCLM WT, Het, and KO murine bone marrow derived macrophages (BMDM) and PBMCs. Percent positive macrophages containing fluorescently labelled AC were quantified for each sample. Cells were collected for total protein, surface receptor expression, and mRNA analysis.

Results: Efferocytosis was affected in macrophages with defective GCLM as compared to control. RNA analysis has showed a decrease in efferocytosis receptors such as MerTK, confirmed by cell surface expression.

Conclusion: These results suggest that loss of GCLM and GSH in macrophages impairs adequate efferocytosis.

Abstract 488: Glutathione-CaSR Interaction Contributes To Glutathione Regulation Of Angiogenesis

Introduction: In addition to its classic role in redox chemistry, glutathione (GSH) also acts as an allosteric regulator of the calcium-sensing receptor (CaSR). CaSR has been found in a variety of cell types including endothelial cells (ECs), where its activity has been linked to EC adhesion and migration. Although a relationship between GSH and CaSR has been discovered, no link has been established between GSH-CaSR interaction and regulation of angiogenesis. We hypothesize a novel mechanism for GSH regulation of blood vessel development occurs through an extracellular interaction with CaSR as a part of physiological and pathological angiogenesis.

Methods: Matrigel tube formation and wound healing assays were used to measure EC activity. RGECO1.2 was used to measure changes in intracellular calcium. Cell surface expression assay was used to measure surface CaSR expression. Cell counts and flow cytometry were used to monitor cell proliferation and cell cycle progression. Endothelial and mesenchymal markers were measured using real-time PCR.

Results: Extracellular GSH increased endothelial tube length and branching in tube formation assay, while a selective CaSR inhibitor abrogated these effects. GSH also influenced EC migration as measured by wound healing assay. GSH or a CaSR agonist (R-568) reduced surface CaSR expression, with no changes in intracellular calcium. Extracellular GSH alters EC proliferation and cell cycle progression, coinciding with alterations in endothelial phenotype along the endothelial-mesenchymal spectrum.

Conclusion: In addition to its classic antioxidant role, GSH appears to act extracellularly to influence EC activity. GSH caused significant increases in EC branching as measured by tube formation assay. The use of a selective CaSR inhibitor confirms the contribution of CaSR to this effect. Additionally, GSH influenced EC migration in wound healing assays. These results could be explained by GSH-CaSR-mediated alterations in endothelial differentiation. These results suggest a role for GSH in vascular development and angiogenesis, through a ligand interaction with the CaSR G-protein coupled receptor, representing a novel mechanism of action for physiological and pathological blood vessel development.

Construction and Performance Testing of a Fast-Assembly COVID-19 (FALCON) Emergency Ventilator in a Model of Normal and Low-Pulmonary Compliance Conditions

INTRODUCTION

The COVID-19 pandemic has revealed an immense, unmet and international need for available ventilators. Both clinical and engineering groups around the globe have responded through the development of "homemade" or do-it-yourself (DIY) ventilators. Several designs have been prototyped, tested, and shared over the internet. However, many open source DIY ventilators require extensive familiarity with microcontroller programming and electronics assembly, which many healthcare providers may lack. In light of this, we designed and bench tested a low-cost, pressure-controlled mechanical ventilator that is "plug and play" by design, where no end-user microcontroller programming is required. This Fast-AssembLy COVID-Nineteen (FALCON) emergency prototype ventilator can be rapidly assembled and could be readily modified and improved upon to potentially provide a ventilatory option when no other is present, especially in low- and middle-income countries.

HYPOTHESIS

We anticipated that a minimal component prototype ventilator could be easily assembled that could reproduce pressure/flow waveforms and tidal volumes similar to a hospital grade ventilator (Engström CarestationTM).

MATERIALS AND METHODS

We benched-tested our prototype ventilator using an artificial test lung under 36 test conditions with varying respiratory rates, peak inspiratory pressures (PIP), positive end expiratory pressures (PEEP), and artificial lung compliances. Pressure and flow waveforms were recorded, and tidal volumes calculated with prototype ventilator performance compared to a hospital-grade ventilator (Engström CarestationTM) under identical test conditions.

RESULTS

Pressure and flow waveforms produced by the prototype ventilator were highly similar to the CarestationTM. The ventilator generated consistent PIP/PEEP, with tidal volume ranges similar to the CarestationTM. The FALCON prototype was tested continuously for a 5-day period without failure or significant changes in delivered PIP/PEEP.

CONCLUSION

The FALCON prototype ventilator is an inexpensive and easily-assembled "plug and play" emergency ventilator design. The FALCON ventilator is currently a non-certified prototype that, following further appropriate validation and testing, might eventually be used as a life-saving emergency device in extraordinary circumstances when more sophisticated forms of ventilation are unavailable.

Ym155 Induces Oxidative Stress-Mediated DNA Damage and Cell Cycle Arrest, and Causes Programmed Cell Death in Anaplastic Thyroid Cancer Cells

Anaplastic thyroid cancer (ATC) is one of the most lethal malignancies with a median survival time of about 4 months. Currently, there is no effective treatment, and the development of new therapies is an important and urgent issue for ATC patients. YM155 is a small molecule that was identified as the top candidate in a high-throughput screen of small molecule inhibitors performed against a panel of ATC cell lines by the National Cancer Institute. However, there were no follow-up studies investigating YM155 in ATC. Here, we determined the effects of YM155 on ATC and human primary benign thyroid cell (PBTC) survival with alamarBlue assay. Our data show that YM155 inhibited proliferation of ATC cell lines while sparing normal thyroid cells, suggesting a high therapeutic window. YM155-induced DNA damage was detected by measuring phosphorylation of γ-H2AX as a marker for DNA double-strand breaks. The formamidopyrimidine-DNA glycosylase (FPG)-modified alkaline comet assay in conjunction with reactive oxygen species (ROS) assay and glutathione (GSH)/glutathione (GSSG) assay suggests that YM155-mediated oxidative stress contributes to DNA damage. In addition, we provide evidence that YM155 causes cell cycle arrest in S phase and in the G2/M transition and causes apoptosis, as seen with flow cytometry. In this study, we show for the first time the multiple effects of YM155 in ATC cells, furthering a potential therapeutic approach for ATC.

Liver kinase B1 inhibits the expression of inflammation-related genes postcontraction in skeletal muscle

Skeletal muscle-specific liver kinase B1 (LKB1) knockout mice (skmLKB1-KO) exhibit elevated mitogen-activated protein kinase (MAPK) signaling after treadmill running. MAPK activation is also associated with inflammation-related signaling in skeletal muscle. Since exercise can induce muscle damage, and inflammation is a response triggered by damaged tissue, we therefore hypothesized that LKB1 plays an important role in dampening the inflammatory response to muscle contraction, and that this may be due in part to increased susceptibility to muscle damage with contractions in LKB1-deficient muscle. Here we studied the inflammatory response and muscle damage with in situ muscle contraction or downhill running. After in situ muscle contractions, the phosphorylation of both NF-κB and STAT3 was increased more in skmLKB1-KO vs. wild-type (WT) muscles. Analysis of gene expression via microarray and RT-PCR shows that expression of many inflammation-related genes increased after contraction only in skmLKB1-KO muscles. This was associated with mild skeletal muscle fiber membrane damage in skmLKB1-KO muscles. Gene markers of oxidative stress were also elevated in skmLKB1-KO muscles after contraction. Using the downhill running model, we observed significantly more muscle damage after running in skmLKB1-KO mice, and this was associated with greater phosphorylation of both Jnk and STAT3 and increased expression of SOCS3 and Fos. In conclusion, we have shown that the lack of LKB1 in skeletal muscle leads to an increased inflammatory state in skeletal muscle that is exacerbated by muscle contraction. Increased susceptibility of the muscle to damage may underlie part of this response.