Chemotherapeutic Activity of Pitavastatin in Vincristine Resistant B-Cell Acute Lymphoblastic Leukemia

B-cell acute lymphoblastic leukemia (ALL) is derived from an accumulation of malignant, immature B cells in the bone marrow and blood. Relapse due, in part, to the emergence of tumor cells that are resistant to front line standard chemotherapy is associated with poor patient outcomes. This challenge highlights the need for new treatment strategies to eliminate residual chemoresistant tumor cells. Based on the use of pitavastatin in acute myeloid leukemia (AML), we evaluated its efficacy in an REH ALL cell line derived to be resistant to vincristine. We found that pitavastatin inhibited the proliferation of both parental and vincristine-resistant REH tumor cells at an IC50 of 449 nM and 217 nM, respectively. Mitochondrial bioenergetic assays demonstrated that neither vincristine resistance nor pitavastatin treatment affected cellular oxidative phosphorylation, beta-oxidation, or glycolytic metabolism in ALL cells. In a co-culture model of ALL cells with bone marrow stromal cells, pitavastatin significantly decreased cell viability more robustly in the vincristine-resistant ALL cells compared with their parental controls. Subsequently, NSG mice were used to develop an in vivo model of B-cell ALL using both parental and vincristine-resistant ALL cells. Pitavastatin (10 mg/kg i.p.) significantly reduced the number of human CD45+ REH ALL cells in the bone marrow of mice after 4 weeks of treatment. Mechanistic studies showed that pitavastatin treatment in the vincristine-resistant cells led to apoptosis, with increased levels of cleaved PARP and protein-signaling changes for AMP-activated protein kinase/FoxO3a/Puma. Our data suggest the possible repurposing of pitavastatin as a chemotherapeutic agent in a model of vincristine-resistant B-cell ALL.

Pitavastatin Is Anti-Leukemic in a Bone Marrow Microenvironment Model of B-Lineage Acute Lymphoblastic Leukemia

Simple Summary

Chemoresistance after chemotherapy is a negative prognostic indicator for B-cell acute lymphoblastic leukemia (ALL), necessitating the search for novel therapies. By growing ALL cells together with bone marrow stromal cells, we developed a chemoresistant ALL model. Using this model, we found that the lipid lowering drug pitavastatin had antileukemic activity in this chemoresistant co-culture model. Our data suggests that pitavastatin may be a novel treatment option for repurposing in chemoresistant, relapse ALL.

Abstract

The lack of complete therapeutic success in the treatment of B-cell acute lymphoblastic leukemia (ALL) has been attributed, in part, to a subset of cells within the bone marrow microenvironment that are drug resistant. Recently, the cholesterol synthesis inhibitor, pitavastatin (PIT), was shown to be active in acute myeloid leukemia, prompting us to evaluate it in our in vitro co-culture model, which supports a chemo-resistant ALL population. We used phospho-protein profiling to evaluate the use of lipid metabolic active compounds in these chemo-resistant cells, due to the up-regulation of multiple active survival signals. In a co-culture with stromal cells, a shift towards anabolic processes occurred, which was further confirmed by assays showing increased lipid content. The treatment of REH leukemia cells with pitavastatin in the co-culture model resulted in significantly higher leukemic cell death than exposure to the standard-of-care chemotherapeutic agent, cytarabine (Ara-C). Our data demonstrates the use of pitavastatin as a possible alternative treatment strategy to improve patient outcomes in chemo-resistant, relapsed ALL.

Cell Communication Network factor 4 promotes tumor-induced immunosuppression in melanoma

Cell Communication Network factor 4 (CCN4/WISP1) is a matricellular protein secreted by cancer cells that promotes metastasis by inducing the epithelial-mesenchymal transition. While metastasis limits survival, limited anti-tumor immunity also associates with poor patient outcomes with recent work linking these two clinical correlates. Motivated by increased CCN4 correlating with dampened anti-tumor immunity in primary melanoma, we test for a direct causal link by knocking out CCN4 (CCN4 KO) in the B16F0 and YUMM1.7 mouse melanoma models. Tumor growth is reduced when CCN4 KO melanoma cells are implanted in immunocompetent but not in immunodeficient mice. Correspondingly, CD45⁺ tumor-infiltrating leukocytes are significantly increased in CCN4 KO tumors, with increased natural killer and CD8⁺ T cells and reduced myeloid-derived suppressor cells (MDSC). Among mechanisms linked to local immunosuppression, CCN4 suppresses IFN-gamma release by CD8⁺ T cells and enhances tumor secretion of MDSC-attracting chemokines like CCL2 and CXCL1. Finally, CCN4 KO potentiates the anti-tumor effect of immune checkpoint blockade (ICB) therapy. Overall, our results suggest that CCN4 promotes tumor-induced immunosuppression and is a potential target for therapeutic combinations with ICB.

Loss of the redox mitochondrial protein mitoNEET leads to mitochondrial dysfunction in B-cell acute lymphoblastic leukemia

B-cell acute lymphoblastic leukemia (ALL) affects both pediatric and adult patients. Chemotherapy resistant tumor cells that contribute to minimal residual disease (MRD) underlie relapse and poor clinical outcomes in a sub-set of patients. Targeting mitochondrial oxidative phosphorylation (OXPHOS) in the treatment of refractory leukemic cells is a potential novel approach to sensitizing tumor cells to existing standard of care therapeutic agents. In the current study, we have expanded our previous investigation of the mitoNEET ligand NL-1 in the treatment of ALL to interrogate the functional role of the mitochondrial outer membrane protein mitoNEET in B-cell ALL. Knockout (KO) of mitoNEET (gene: CISD1) in REH leukemic cells led to changes in mitochondrial ultra-structure and function. REH cells have significantly reduced OXPHOS capacity in the KO cells coincident with reduction in electron flow and increased reactive oxygen species. In addition, we found a decrease in lipid content in KO cells, as compared to the vector control cells was observed. Lastly, the KO of mitoNEET was associated with decreased proliferation as compared to control cells when exposed to the standard of care agent cytarabine (Ara-C). Taken together, these observations suggest that mitoNEET is essential for optimal function of mitochondria in B-cell ALL and may represent a novel anti-leukemic drug target for treatment of minimal residual disease.

Co-culture model of B-cell acute lymphoblastic leukemia recapitulates a transcription signature of chemotherapy-refractory minimal residual disease

B-cell acute lymphoblastic leukemia (ALL) is characterized by accumulation of immature hematopoietic cells in the bone marrow, a well-established sanctuary site for leukemic cell survival during treatment. While standard of care treatment results in remission in most patients, a small population of patients will relapse, due to the presence of minimal residual disease (MRD) consisting of dormant, chemotherapy-resistant tumor cells. To interrogate this clinically relevant population of treatment refractory cells, we developed an in vitro cell model in which human ALL cells are grown in co-culture with human derived bone marrow stromal cells or osteoblasts. Within this co-culture, tumor cells are found in suspension, lightly attached to the top of the adherent cells, or buried under the adherent cells in a population that is phase dim (PD) by light microscopy. PD cells are dormant and chemotherapy-resistant, consistent with the population of cells that underlies MRD. In the current study, we characterized the transcriptional signature of PD cells by RNA-Seq, and these data were compared to a published expression data set derived from human MRD B-cell ALL patients. Our comparative analyses revealed that the PD cell population is markedly similar to the MRD expression patterns from the primary cells isolated from patients. We further identified genes and key signaling pathways that are common between the PD tumor cells from co-culture and patient derived MRD cells as potential therapeutic targets for future studies.

Pyrvinium Pamoate Use in a B cell Acute Lymphoblastic Leukemia Model of the Bone Tumor Microenvironment

PURPOSE

Pyrvinium pamoate (PP) is an anthelmintic drug that has been found to have anti-cancer activity in several cancer types. In the present study, we evaluated PP for potential anti-leukemic activity in B cell acute lymphoblastic leukemia (ALL) cell lines, in an effort to evaluate the repurposing potential of this drug in leukemia.

METHODS

ALL cells were treated with PP at various concentrations to determine its effect on cell proliferation. Metabolic function was tested by evaluating Extracellular Acidification Rate (ECAR) and Oxygen Consumption Rate (OCR). Lastly, 3D spheroids were grown, and PP was reformulated into nanoparticles to evaluate distribution effectiveness.

RESULTS

PP was found to inhibit ALL proliferation, with varied selectivity to different ALL cell subtypes. We also found that PP's cell death activity was specific for leukemic cells, as primary normal immune cells were resistant to PP-mediated cell death. Metabolic studies indicated that PP, in part, inhibits mitochondrial oxidative phosphorylation. To increase the targeting of PP to a hypoxic bone tumor microenvironment (BTME) niche, we successfully encapsulated PP in a nanoparticle drug delivery system and demonstrated that it retained its anti-leukemic activity in a hemosphere assay.

CONCLUSION

We have demonstrated that PP is a novel therapeutic lead compound that counteracts the respiratory reprogramming found in refractory ALL cells and can be effectively formulated into a nanoparticle delivery system to target the BTME.

Amyloid-β Causes Mitochondrial Dysfunction via a Ca2+-Driven Upregulation of Oxidative Phosphorylation and Superoxide Production in Cerebrovascular Endothelial Cells

Cerebrovascular pathology is pervasive in Alzheimer's disease (AD), yet it is unknown whether cerebrovascular dysfunction contributes to the progression or etiology of AD. In human subjects and in animal models of AD, cerebral hypoperfusion and hypometabolism are reported to manifest during the early stages of the disease and persist for its duration. Amyloid-β is known to cause cellular injury in both neurons and endothelial cells by inducing the production of reactive oxygen species and disrupting intracellular Ca2+ homeostasis. We present a mechanism for mitochondrial degeneration caused by the production of mitochondrial superoxide, which is driven by increased mitochondrial Ca2+ uptake. We found that persistent superoxide production injures mitochondria and disrupts electron transport in cerebrovascular endothelial cells. These observations provide a mechanism for the mitochondrial deficits that contribute to cerebrovascular dysfunction in patients with AD.

Extracellular Vesicles Secreted in Response to Cytokine Exposure Increase Mitochondrial Oxygen Consumption in Recipient Cells

Extracellular vesicles (EVs) are small, membrane-bound nanoparticles released from most, if not all cells, and can carry functionally active cargo (proteins, nucleic acids) which can be taken up by neighboring cells and mediate physiologically relevant effects. In this capacity, EVs are being regarded as novel cell-to-cell communicators, which may play important roles in the progression of neurodegenerative diseases, like Alzheimer’s disease (AD). Aside from the canonical physical hallmarks of this disease [amyloid β (Aβ) plaques, neurofibrillary tangles, and widespread cell death], AD is characterized by chronic neuroinflammation and mitochondrial dysfunction. In the current study, we sought to better understand the role of tumor necrosis factor-alpha (TNF-α), known to be involved in inflammation, in mediating alterations in mitochondrial function and EV secretion. Using an immortalized hippocampal cell line, we observed significant reductions in several parameters of mitochondrial oxygen consumption after a 24-h exposure period to TNF-α. In addition, after TNF-α exposure we also observed significant upregulation of two microRNAs (miRNAs; miR-34a and miR-146a) associated with mitochondrial dysfunction in secreted EVs. Despite this, when naïve cells are exposed to EVs isolated from TNF-α treated cells, mitochondrial respiration, proton leak, and reactive oxygen species (ROS) production are all significantly increased. Collectively these data indicate that a potent proinflammatory cytokine, TNF-α, induces significant mitochondrial dysfunction in a neuronal cell type, in part via the secretion of EVs, which significantly alter mitochondrial activity in recipient cells.

Gradual common carotid artery occlusion as a novel model for cerebrovascular Hypoperfusion

Chronic cerebrovascular hypoperfusion results in vascular dementia and increases predisposition to lacunar infarcts. However, there are no suitable animal models. In this study, we developed a novel model for chronic irreversible cerebral hypoperfusion in mice. Briefly, an ameroid constrictor was placed on the right carotid artery to gradually occlude the vessel, while a microcoil was placed on the left carotid artery to prevent compensation of the blood flow. This procedure resulted in a gradual hypoperfusion developing over a period of 34 days with no cerebral blood flow recovery. Histological analysis of the brain revealed neuronal and axonal degeneration as well as necrotic lesions. The most severely affected regions were located in the hippocampus and the corpus callosum. Overall, our paradigm is a viable model to study brain pathology resulting from gradual cerebrovascular hypoperfusion.

MiR-34a and stroke: Assessment of non-modifiable biological risk factors in cerebral ischemia

Aging of the nervous system, and the occurrence of age-related brain diseases such as stroke, are associated with changes to a variety of cellular processes controlled by many distinct genes. MicroRNAs (miRNAs), short non-coding functional RNAs that can induce translational repression or site-specific cleavage of numerous target mRNAs, have recently emerged as important regulators of cellular senescence, aging, and the response to neurological insult. Here, we focused on the assessment of the role of miR-34a in stroke. We noted increases in miR-34a expression in the blood of stroke patients as well as in blood and brain of mice subjected to experimental stroke. Our methodical genetic manipulation of miR-34a expression substantially impacted stroke-associated preclinical outcomes and we have in vitro evidence that these changes may be driven at least in part by disruptions to blood brain barrier integrity and mitochondrial oxidative phosphorylation in endothelial cells. Finally, aging, independent of brain injury, appears to be associated with shifts in circulating miRNA profiles. Taken together, these data support a role for miRNAs, and specifically miR-34a, in brain aging and the physiological response to age-related neurological insult, and lay the groundwork for future investigation of this novel therapeutic target.

Exosomes derived from B16F0 melanoma cells alter the transcriptome of cytotoxic T cells that impacts mitochondrial respiration

While recent clinical studies demonstrate the promise of cancer immunotherapy, a barrier for broadening the clinical benefit is identifying how tumors locally suppress cytotoxic immunity. As an emerging mode of intercellular communication, exosomes secreted by malignant cells can deliver a complex payload of coding and noncoding RNA to cells within the tumor microenvironment. Here, we quantified the RNA payload within tumor-derived exosomes and the resulting dynamic transcriptomic response to cytotoxic T cells upon exosome delivery to better understand how tumor-derived exosomes can alter immune cell function. Exosomes derived from B16F0 melanoma cells were enriched for a subset of coding and noncoding RNAs that did not reflect the abundance in the parental cell. Upon exosome delivery, RNAseq revealed the dynamic changes in the transcriptome of CTLL2 cytotoxic T cells. In analyzing transiently coexpressed gene clusters, pathway enrichment suggested that the B16F0 exosomal payload altered mitochondrial respiration, which was confirmed independently, and upregulated genes associated with the Notch signaling pathway. Interestingly, exosomal miRNA appeared to have no systematic effect on downregulating target mRNA levels.

DATABASES

Gene expression data are available in the GEO database under the accession SuperSeries number GSE102951.

Uncoupling of the Electron Transport Chain Compromises Mitochondrial Oxidative Phosphorylation and Exacerbates Stroke Outcomes

Objective

Mitochondrial dysfunction is known to be implicated in stroke, but the complex mechanisms of stroke have led to few stroke therapies. The present study to disrupted mitochondrial oxidative phosphorylation through a known electron transport chain (ETC) uncoupler, Carbonyl cyanide-4 (trifluoromethoxy) phenylhydrazone (FCCP). Analyzing the resulting neurological deficits as well as infarct volume could help determine the role of mitochondria in stroke outcome and determine whether uncoupling the ETC could potentially be a strategy for new stroke therapies. The objective of this study was to determine the effects of uncoupling electron flow on mitochondrial oxidative phosphorylation and stroke infarction.

Methods

Cerebral endovascular cells (CECs) were treated with various concentrations of FCCP, and bioenergetics were measured. For the stroke mouse model, FCCP (1 mg/kg, i.p) or vehicle was administered followed by 1-hour transient middle cerebral artery occlusion (tMCAO). Infarct volume was measured after a 23-hour reperfusion, and triphenyl tetrazolium chloride (TTC) staining was used to assess infarct volume.

Results

FCCP significantly decreased basal respiration, ATP turnover, maximal respiration, and spare capacity when the concentration of FCCP was greater than 1000 nM. The mice pretreated with FCCP had a significantly increased infarct volume within the cortex, striatum, and total hemisphere. Mice receiving FCCP had a significantly increased neurological deficit score compared to the vehicle.

Conclusions

FCCP compromised mitochondrial oxidative phosphorylation in CECs in a dose-dependent manner. Uncoupling the electron transport chain with FCCP prior to tMCAO exacerbated stroke infarction in mice.

Maternal-engineered nanomaterial exposure disrupts progeny cardiac function and bioenergetics

Nanomaterial production is expanding as new industrial and consumer applications are introduced. Nevertheless, the impacts of exposure to these compounds are not fully realized. The present study was designed to determine whether gestational nano-sized titanium dioxide exposure impacts cardiac and metabolic function of developing progeny. Pregnant Sprague-Dawley rats were exposed to nano-aerosols (~10 mg/m³, 130- to 150-nm count median aerodynamic diameter) for 7-8 nonconsecutive days, beginning at gestational day 5-6 Physiological and bioenergetic effects on heart function and cardiomyocytes across three time points, fetal (gestational day 20), neonatal (4-10 days), and young adult (6-12 wk), were evaluated. Functional analysis utilizing echocardiography, speckle-tracking based strain, and cardiomyocyte contractility, coupled with mitochondrial energetics, revealed effects of nano-exposure. Maternal exposed progeny demonstrated a decrease in E- and A-wave velocities, with a 15% higher E-to-A ratio than controls. Myocytes isolated from exposed animals exhibited ~30% decrease in total contractility, departure velocity, and area of contraction. Bioenergetic analysis revealed a significant increase in proton leak across all ages, accompanied by decreases in metabolic function, including basal respiration, maximal respiration, and spare capacity. Finally, electron transport chain complex I and IV activities were negatively impacted in the exposed group, which may be linked to a metabolic shift. Molecular data suggest that an increase in fatty acid metabolism, uncoupling, and cellular stress proteins may be associated with functional deficits of the heart. In conclusion, gestational nano-exposure significantly impairs the functional capabilities of the heart through cardiomyocyte impairment, which is associated with mitochondrial dysfunction.NEW & NOTEWORTHY Cardiac function is evaluated, for the first time, in progeny following maternal nanomaterial inhalation. The findings indicate that exposure to nano-sized titanium dioxide (nano-TiO₂) during gestation negatively impacts cardiac function and mitochondrial respiration and bioenergetics. We conclude that maternal nano-TiO₂ inhalation contributes to adverse cardiovascular health effects, lasting into adulthood.

Evaluation of Bioenergetic Function in Cerebral Vascular Endothelial Cells

The integrity of the blood-brain-barrier (BBB) is critical to prevent brain injury. Cerebral vascular endothelial (CVE) cells are one of the cell types that comprise the BBB; these cells have a very high-energy demand, which requires optimal mitochondrial function. In the case of disease or injury, the mitochondrial function in these cells can be altered, resulting in disease or the opening of the BBB. In this manuscript, we introduce a method to measure mitochondrial function in CVE cells by using whole, intact cells and a bioanalyzer. A mito-stress assay is used to challenge the cells that have been perturbed, either physically or chemically, and evaluate their bioenergetic function. Additionally, this method also provides a useful way to screen new therapeutics that have direct effects on mitochondrial function. We have optimized the cell density necessary to yield oxygen consumption rates that allow for the calculation of a variety of mitochondrial parameters, including ATP production, maximal respiration, and spare capacity. We also show the sensitivity of the assay by demonstrating that the introduction of the microRNA, miR-34a, leads to a pronounced and detectable decrease in mitochondrial activity. While the data shown in this paper is optimized for the bEnd.3 cell line, we have also optimized the protocol for primary CVE cells, further suggesting the utility in preclinical and clinical models.

Bone marrow microenvironment modulation of acute lymphoblastic leukemia phenotype

Acute lymphoblastic leukemia (ALL) treatment regimens have dramatically improved the survival of ALL patients. However, chemoresistant minimal residual disease that persists following cessation of therapy contributes to aggressive relapse. The bone marrow microenvironment (BMM) is an established "site of sanctuary" for ALL, as well as myeloid-lineage hematopoietic disease, with signals in this unique anatomic location contributing to drug resistance. Several models have been developed to recapitulate the interactions between the BMM and ALL cells. However, many in vitro models fail to accurately reflect the level of protection afforded to the most resistant subset of leukemic cells during coculture with BMM elements. Preclinical in vivo models have advantages, but can be costly, and are often not fully informed by optimal in vitro studies. We describe an innovative extension of 2-D coculture wherein ALL cells uniquely interact with bone marrow-derived stromal cells. Tumor cells in this model bury beneath primary human bone marrow-derived stromal cells or osteoblasts, termed "phase dim" ALL, and exhibit a unique phenotype characterized by altered metabolism, distinct protein expression profiles, increased quiescence, and pronounced chemotherapy resistance. Investigation focused on the phase dim subpopulation may more efficiently inform preclinical design and investigation of the minimal residual disease and relapse that arise from BMM-supported leukemic tumor cells.

Abstract W P105: Lipopolysaccharide Exacerbates Stroke Severity and Compromises Mitochondrial Function in Cerebral Endothelium

Stroke is the fourth leading cause of death in the U.S, with many cases leading to severe disabilities. Statistics reports present that more than 40% of ischemic stroke patients have recent prior infections. Acute infections initiate rapid inflammation and can be a trigger for acute ischemic stroke in people. Ischemia-reperfusion injury following ischemic stroke induces blood-brain barrier (BBB) breakdown, hyperpermeability and brain edema. Cerebral vascular endothelial cells (CVEC) lining the BBB play a key role in fluid leakage into the brain tissue. The expression of toll-like receptor 4 (TLR4, specific for bacteria-sourced lipopolysaccharide, LPS) on CVEC implicates that acute bacterial infections may directly target CVEC and regulate BBB permeability and integrity. High mitochondrial contents in BBB capillaries suggest mitochondrial mechanisms are important to maintain BBB integrity.

In order to test the hypothesis that bacterial infections regulate BBB permeability via mitochondrial mechanisms in stroke, we designed a series of studies both in vivo and in vitro. First, we used LPS challenged mice, then evaluated stroke outcomes including: infarct size, neurological deficits, BBB permeability and infiltration of neutrophils in the brain after transient middle cerebral artery occlusion (tMCAO). Second, we treated cultured CVEC with various concentrations of LPS and evaluated their mitochondrial function. Third, we impaired mitochondrial function in CVEC and investigated the BBB permeability in vitro.

Our results demonstrated that LPS (100ug/kg) prior to tMCAO administration significantly exacerbates stroke infarct volume, BBB permeability and neutrophil infiltration in the brain, and worsens neurological deficits in murine experimental stroke in vivo. In vitro, LPS significantly impaired mitochondrial oxidative phosphorylation and decreased maximal respiration and spare capacity in CVEC. Finally, pharmacological inhibition of mitochondria respiration disrupted tight junctions in CVEC monolayers and increased CVEC monolayer permeability in vitro.

These data are particularly important because they suggest a novel mitochondrial mechanism of the interactions between stroke and infections on BBB integrity.

Rapid mitochondrial dysfunction mediates TNF-alpha-induced neurotoxicity

Tumor necrosis factor alpha (TNF-α) is known to exacerbate ischemic brain injury; however, the mechanism is unknown. Previous studies have evaluated the effects of TNF-α on neurons with long exposures to high doses of TNF-α, which is not pathophysiologically relevant. We characterized the rapid effects of TNF-α on basal respiration, ATP production, and maximal respiration using pathophysiologically relevant, post-stroke concentrations of TNF-α. We observed a reduction in mitochondrial function as early as 1.5 h after exposure to low doses of TNF-α, followed by a decrease in cell viability in HT-22 cells and primary neurons. Subsequently, we used the HT-22 cell line to determine the mechanism by which TNF-α causes a rapid and profound reduction in mitochondrial function. Pre-treating with TNF-R1 antibody, but not TNF-R2 antibody, ameliorated the neurotoxic effects of TNF-α, indicating that TNF-α exerts its neurotoxic effects through TNF-R1. We observed an increase in caspase 8 activity and a decrease in mitochondrial membrane potential after exposure to TNF-α which resulted in a release of cytochrome c from the mitochondria into the cytosol. These novel findings indicate for the first time that an acute exposure to pathophysiologically relevant concentrations of TNF-α has neurotoxic effects mediated by a rapid impairment of mitochondrial function. This study focuses on the neurotoxic mechanism of a pro-inflammatory cytokine, tumor necrosis factor alpha (TNF-α). We demonstrate a prompt mitochondrial dysfunction followed by nerve cell loss after exposure to TNF-α. These studies may provide evidence that the immune system can rapidly and adversely affect brain function and that TNF-α signaling may be a target for neuroprotection.

The PYRIN domain-only protein POP3 inhibits ALR inflammasomes and regulates responses to infection with DNA viruses

The innate immune system responds to infection and tissue damage by activating cytosolic sensory complexes called 'inflammasomes'. Cytosolic DNA is sensed by AIM2-like receptors (ALRs) during bacterial and viral infections and in autoimmune diseases. Subsequently, recruitment of the inflammasome adaptor ASC links ALRs to the activation of caspase-1. A controlled immune response is crucial for maintaining homeostasis, but the regulation of ALR inflammasomes is poorly understood. Here we identified the PYRIN domain (PYD)-only protein POP3, which competes with ASC for recruitment to ALRs, as an inhibitor of DNA virus-induced activation of ALR inflammasomes in vivo. Data obtained with a mouse model with macrophage-specific POP3 expression emphasize the importance of the regulation of ALR inflammasomes in monocytes and macrophages.

Abstract TP232: A Biomarker Algorithm that Represents Time from Stroke Symptom Onset

Background and Purpose: Time of onset is critical when treating ischemic stroke (IS). The purpose of this project was to investigate the use of our 9 gene profile to develop a biomarker algorithm that represents time from stroke onset for use in the clinical setting to improve utilization of tissue plasminogen activator (tPA) and streamline appropriate secondary prevention.

Methods: Peripheral blood samples were collected from n=34 IS patients’ ≥18 years of age within 24 hours from symptom onset and 24-48 hours later. Total RNA was extracted from whole blood in Paxgene RNA tubes, amplified, and hybridized to Illumina HumanRef-8v2 bead chips. Gene expression was compared in a univariate manner between patients at both time points using t -test in GeneSpring. Inflation of type one error was corrected by Bonferroni. A linear regression was used to model the change in gene expression as a linear function of time when controlling for age.

Results: The mean age of the sample was 71.9± (14.6 sd ) years. Mean time from symptom onset to acute blood draw was 9:29± (6:2 sd ) hours (range 2:35-23:02); to follow up blood draw was 29:24± (7.1 sd ) hours (range 18:45-43:30); and time between acute and follow up blood draw was 19:55± (3.3 sd ) hours (range 13:30-27:32). CA4 and ARG1 expression significantly decreased >1.5 fold, and LY96 expression by >2-fold between baseline and follow up. This decrease in expression was associated with an increase from time of stroke onset and remained significant for only LY96 expression when controlling for age. ARG1 and CA4 expression were significantly lower in older patients.

Conclusions: Our profile provides evidence that the expression of LY96 , CA4 , and ARG1 in the peripheral blood may serve as a surrogate for determining the time of stroke onset. In clinical practice, an algorithm based on this biomarker profile and other clinical covariates could be used when time of onset is unknown. To increase the accuracy of our biomarker algorithm, it will be important to determine the effects of age, stroke severity, and other clinical covariates on the expression of these genes over time.

Melphalan exposure induces an interleukin-6 deficit in bone marrow stromal cells and osteoblasts

Bone marrow stromal cells (BMSC) and osteoblasts are critical components of the microenvironment that support hematopoietic recovery following bone marrow transplantation. Aggressive chemotherapy not only affects tumor cells, but also influences additional structural and functional components of the microenvironment. Successful reconstitution of hematopoiesis following stem cell or bone marrow transplantation after aggressive chemotherapy is dependent upon components of the microenvironment maintaining their supportive function. This includes secretion of soluble factors and expression of cellular adhesion molecules that impact on development of hematopoietic cells. In the current study, we investigated the effects of chemotherapy treatment on BMSC and human osteoblast (HOB) expression of interleukin-6 (IL-6) as one regulatory factor. IL-6 is a pleiotropic cytokine which has diverse effects on hematopoietic cell development. In the current study we demonstrate that exposure of BMSC or HOB to melphalan leads to decreases in IL-6 protein expression. Decreased IL-6 protein is the most pronounced following melphalan exposure compared to several other chemotherapeutic agents tested. We also observed that melphalan decreased IL-6 mRNA in both BMSC and HOB. Finally, using a model of BMSC or HOB co-cultured with myeloma cells exposed to melphalan, we observed that IL-6 protein was also decreased, consistent with treatment of adherent cells alone. Collectively, these observations are of dual significance. First, suggesting that chemotherapy induced IL-6 deficits in the bone marrow occur which may result in defective hematopoietic support of early progenitor cells. In contrast, the decrease in IL-6 protein may be a beneficial mechanism by which melphalan acts as a valuable therapeutic agent for treatment of multiple myeloma, where IL-6 present in the bone marrow acts as a proliferative factor and contributes to disease progression. Taken together, these data emphasize the responsiveness of the microenvironment to diverse stress that is important to consider in therapeutic settings.

Bone marrow osteoblast damage by chemotherapeutic agents

Hematopoietic reconstitution, following bone marrow or stem cell transplantation, requires a microenvironment niche capable of supporting both immature progenitors and stem cells with the capacity to differentiate and expand. Osteoblasts comprise one important component of this niche. We determined that treatment of human primary osteoblasts (HOB) with melphalan or VP-16 resulted in increased phospho-Smad2, consistent with increased TGF-β1 activity. This increase was coincident with reduced HOB capacity to support immature B lineage cell chemotaxis and adherence. The supportive deficit was not limited to committed progenitor cells, as human embryonic stem cells (hESC) or human CD34+ bone marrow cells co-cultured with HOB pre-exposed to melphalan, VP-16 or rTGF-β1 had profiles distinct from the same populations co-cultured with untreated HOB. Functional support deficits were downstream of changes in HOB gene expression profiles following chemotherapy exposure. Melphalan and VP-16 induced damage of HOB suggests vulnerability of this critical niche to therapeutic agents frequently utilized in pre-transplant regimens and suggests that dose escalated chemotherapy may contribute to post-transplantation hematopoietic deficits by damaging structural components of this supportive niche.

Cellular elements of the subarachnoid space promote ALL survival during chemotherapy

CNS infiltration by leukemic cells remains a problematic disease manifestation of acute lymphoblastic leukemia (ALL). Prophylactic regimens for CNS leukemia including intrathecal chemotherapeutics have decreased CNS involvement in ALL, but are not without toxicities. Using co-culture models, we show that astrocytes, choroid plexus epithelial cells, and meningeal cells protect ALL cells from chemotherapy-induced cell death using drugs included in prophylactic regimens-cytarabine, dexamethasone, and methotrexate. Understanding how ALL cells survive in the CNS remains invaluable for designing strategies to prevent CNS leukemia and minimizing the need for treatment in this sensitive anatomical site where treatment-induced toxicity is of significant concern.

A Shope Fibroma virus PYRIN-only protein modulates the host immune response

PYRIN domain (PYD) proteins have recently emerged as important signaling molecules involved in the development of innate immunity to intracellular pathogens through activation of inflammatory mediator pathways. ASC is the central adaptor protein, which links pathogen recognition by PYD-containing pathogen recognition receptors to the activation of downstream effectors, including activation of Caspase-1 and NF-kappaB. The cellular PYD-only protein 1 (cPOP1) can block the recruitment of ASC to activated PAN receptors and thereby functions as an endogenous inhibitor of the PYD-mediated signal transduction pathway. Here we describe the identification and characterization of a Shope Fibroma homolog to cPOP1. Like cPOP1, a Shope Fibroma virus-encoded POP (vPOP), co-localizes and directly associates with ASC and inhibits PYD-mediated signal transduction. Poxviruses are known to encode immune evasive proteins to promote host cell infection and suppression of the host immune response. Poxvirus-encoded vPOPs represent a novel class of immune evasive proteins and impair the host response by blocking Cryopyrin and ASC inflammasome-mediated activation of pro-Caspase-1 and subsequent processing of pro-interleukin (IL)-1beta, and expression of vPOPs causes activation of NF-kappaB.

Cellular pyrin domain-only protein 2 is a candidate regulator of inflammasome activation

Pyrin domain (PYD) proteins have recently emerged as important signaling molecules involved in the development of innate immunity against intracellular pathogens through activation of inflammatory mediator pathways. ASC is the central adaptor protein, which links pathogen recognition by PYD-containing pathogen recognition receptors, known as PYD-Nod-like receptors (NLR), PAN, PYPAF, NALP, Nod, and Caterpiller proteins, to the activation of downstream effectors, including activation of caspase-1 and NF-kappaB. Activation of these effectors occurs when specific protein complexes, known as inflammasomes, are formed. PYD signal transduction leads to inflammasome assembly and activation of specific effector proteins. It is modulated by a cellular PYD-only protein (cPOP1), which binds to ASC and interferes with the recruitment of ASC to activated PYD-NLRs. Here we describe the identification and characterization of a second cellular POP (cPOP2), which shows highest homology to the PYD of PAN1. cPOP2 binds to ASC and PAN1, thereby blocking formation of cryopyrin and PAN1-containing inflammasomes, activation of caspase-1, and subsequent processing and secretion of bioactive interleukin-1beta. Existence of a second cPOP provides additional insights into inflammasome formation and suggests that POPs might be a common regulatory mechanism to "fine-tune" the activity of specific PYD-NLR family protein-containing inflammasomes.