Targeting Acute Myeloid Leukemia Stem Cells Through Perturbation of Mitochondrial Calcium

We previously reported that acute myeloid leukemia stem cells (LSCs) are uniquely reliant on oxidative phosphorylation (OXPHOS) for survival. Moreover, maintenance of OXPHOS is dependent on BCL2, creating a therapeutic opportunity to target LSCs using the BCL2 inhibitor drug venetoclax. While venetoclax-based regimens have indeed shown promising clinical activity, the emergence of drug resistance is prevalent. Thus, in the present study, we investigated how mitochondrial properties may influence mechanisms that dictate venetoclax responsiveness. Our data show that utilization of mitochondrial calcium is fundamentally different between drug responsive and non-responsive LSCs. By comparison, venetoclax-resistant LSCs demonstrate a more active metabolic (i.e., OXPHOS) status with relatively high steady-state levels of calcium. Consequently, we tested genetic and pharmacological approaches to target the mitochondrial calcium uniporter, MCU. We demonstrate that inhibition of calcium uptake sharply reduces OXPHOS and leads to eradication of venetoclax-resistant LSCs. These findings demonstrate a central role for calcium signaling in the biology of LSCs and provide a therapeutic avenue for clinical management of venetoclax resistance.

Machine Learning–Based Exploratory Clinical Decision Support for Newly Diagnosed Patients With Acute Myeloid Leukemia Treated With 7 + 3 Type Chemotherapy or Venetoclax/Azacitidine

PURPOSE

There are currently limited objective criteria to help assist physicians in determining whether an individual patient with acute myeloid leukemia (AML) is likely to do better with induction with either standard 7 + 3 chemotherapy or targeted therapy with venetoclax plus azacitidine. The study goal was to address this need by developing exploratory clinical decision support methods.

PATIENTS AND METHODS

Univariable and multivariable analysis as well as comparison of a range of machine learning (ML) predictors were performed using cohorts of 120 newly diagnosed 7 + 3-treated AML patients compared with 101 venetoclax plus azacitidine–treated patients.

RESULTS

A variety of features in the two patient cohorts were identified that may potentially correlate with short- and long-term outcomes, toxicities, and other considerations. A subset of these diagnostic features was then used to develop ML-based predictors with relatively high areas under the curve of short- and long-term outcomes, hospital stays, transfusion requirements, and toxicities for individual patients treated with either venetoclax/azacitidine or 7 + 3.

CONCLUSION

Potential ML-based approaches to clinical decision support to help guide individual patients with newly diagnosed AML to either 7 + 3 or venetoclax plus azacitidine induction therapy were identified. Larger cohorts with separate test and validation studies are necessary to confirm these initial findings.

EPEN-26. NON-CANONICAL NF-κB SIGNALING DRIVES MESENCHYMAL EPENDYMAL CELL SUBPOPULATION IN PFA EPENDYMOMA

NF-κB signaling is a hallmark of PFA1 ependymoma. Loss of LDOC1, through epigenetic silencing, leads to constitutively active NF-κB signaling and chronic IL-6 secretion. In this study, we investigate the loss of LDOC1 within the PFA tumor clusters. Using our PFA scRNAseq database, in which there are 5 clusters within the tumor cell compartment: mesenchymal (MEC), ciliated (CEC), transportive (TEC), and undifferentiated (UEC). LDOC1 expression was significantly reduced and had an inverse correlation with genes defining the unfavorable MEC subpopulation, predominate in PFA1. This is consistent with our findings that MEC was defined by an NF-κB2 signaling profile. In contrast, LDOC1 expression was higher and positively correlated with genes defining the favorable CEC subpopulation, mostly seen in PFA2. RELA expression, which we studied as a target of LDOC1, was not localized to MEC and was wide-spread throughout the PFA compartment. RELB, part of non-conical NF-κB signaling, was expressed only the MEC subpopulation correlating with IL-6 gene expression found only in this subpopulation. In MAF-811, a PFA cell line with more CEC-like gene phenotype, RELB co-immunoprecipates with the active form of NF-κB2 in both the nucleus and cytoplasm. IL-6 gene expression is almost completely lost when NF-κB2 is knock-down using shRNA. Additionally, loss of LDOC1 leads to over 3 fold increase in NF-κB2 expression. Combined with our previous work, this would suggest that NF-κB2 drives IL-6 expression by binding with RELB in MEC subpopulation and targeting loss of LDOC1 may shift the MEC subpopulation toward the more favorable CEC subpopulation.

EPEN-31. SINGLE-CELL RNAseq OF CHILDHOOD EPENDYMOMA REVEALS DISTINCT NEOPLASTIC CELL SUBPOPULATIONS THAT IMPACT ETIOLOGY, MOLECULAR CLASSIFICATION AND OUTCOME

Ependymoma (EPN) is a brain tumor commonly presenting in childhood that remains fatal in the majority of children. Intra-tumoral cellular heterogeneity in bulk-tumor samples significantly confounds our understanding of EPN biology, impeding development of effective therapy. We therefore used single-cell RNA sequencing to catalog cellular heterogeneity of 26 childhood EPN, predominantly from ST-RELA, PFA1 and PFA2 subgroups. ST-RELA and PFA subgroups clustered separately, with ST-RELA clustering largely according to individual sample-of-origin. PFA1 and PFA2 subgroup EPNs cells were intermixed and revealed 4 major subpopulations – 2 with characteristics of ependymal differentiation (transporter and ciliated phenotype subpopulations), an undifferentiated subpopulation and a mesenchymal phenotype. Pseudotime analysis showed the undifferentiated progenitor subpopulation either differentiating into ependymal differentiation subpopulations or transitioning into the mesenchymal subpopulation. Histological analysis revealed that undifferentiated and mesenchymal subpopulations cells colocalized to perinecrotic/perivascular zones, the putative ependymoma stem cell niche. Deconvolution of PFA bulk transcriptome data showed that undifferentiated and mesenchymal subpopulations were associated with a poor prognosis; whereas the ciliated ependymal cell-differentiated subpopulation was associated with a good prognosis. In conflict with current distinct classification paradigms, the ratio of mesenchymal and ciliated subpopulations determined bulk-tumor subgroups assignment to PFA1 and PFA2 respectively. This atlas of EPN cellular heterogeneity provides an important advance in our understanding of EPN biology, identifying high-risk associated subpopulations for therapeutic targeting.

Prdm8 regulates pMN progenitor specification for motor neuron and oligodendrocyte fates by modulating the Shh signaling response

Spinal cord pMN progenitors sequentially produce motor neurons and oligodendrocyte precursor cells (OPCs). Some OPCs differentiate rapidly as myelinating oligodendrocytes, whereas others remain into adulthood. How pMN progenitors switch from producing motor neurons to OPCs with distinct fates is poorly understood. pMN progenitors express prdm8, which encodes a transcriptional repressor, during motor neuron and OPC formation. To determine whether prdm8 controls pMN cell fate specification, we used zebrafish as a model system to investigate prdm8 function. Our analysis revealed that prdm8 mutant embryos have fewer motor neurons resulting from a premature switch from motor neuron to OPC production. Additionally, prdm8 mutant larvae have excess oligodendrocytes and a concomitant deficit of OPCs. Notably, pMN cells of mutant embryos have elevated Shh signaling, coincident with the motor neuron to OPC switch. Inhibition of Shh signaling restored the number of motor neurons to normal but did not rescue the proportion of oligodendrocytes. These data suggest that Prdm8 regulates the motor neuron-OPC switch by controlling the level of Shh activity in pMN progenitors, and also regulates the allocation of oligodendrocyte lineage cell fates.This article has an associated 'The people behind the papers' interview.

Redistribution of EC-SOD resolves bleomycin-induced inflammation via increased apoptosis of recruited alveolar macrophages

A human single nucleotide polymorphism (SNP) in the matrix-binding domain of extracellular superoxide dismutase (EC-SOD), with arginine to glycine substitution at position 213 (R213G), redistributes EC-SOD from the matrix into extracellular fluids. We reported that, following bleomycin (bleo), knockin mice harboring the human R213G SNP (R213G mice) exhibit enhanced resolution of inflammation and protection against fibrosis, compared with wild-type (WT) littermates. In this study, we tested the hypothesis that the EC-SOD R213G SNP promotes resolution via accelerated apoptosis of recruited alveolar macrophage (AM). RNA sequencing and Ingenuity Pathway Analysis 7 d postbleo in recruited AM implicated increased apoptosis and blunted inflammatory responses in the R213G strain exhibiting accelerated resolution. We validated that the percentage of apoptosis was significantly elevated in R213G recruited AM vs. WT at 3 and 7 d postbleo in vivo. Recruited AM numbers were also significantly decreased in R213G mice vs. WT at 3 and 7 d postbleo. ChaC glutathione-specific γ-glutamylcyclotransferase 1 (Chac1), a proapoptotic γ-glutamyl cyclotransferase that depletes glutathione, was increased in the R213G recruited AM. Overexpression of Chac1 in vitro induced apoptosis of macrophages and was blocked by administration of cell-permeable glutathione. In summary, we provide new evidence that redistributed EC-SOD accelerates the resolution of inflammation through redox-regulated mechanisms that increase recruited AM apoptosis.-Allawzi, A., McDermott, I., Delaney, C., Nguyen, K., Banimostafa, L., Trumpie, A., Hernandez-Lagunas, L., Riemondy, K., Gillen, A., Hesselberth, J., El Kasmi, K., Sucharov, C. C., Janssen, W. J., Stenmark, K., Bowler, R., Nozik-Grayck, E. Redistribution of EC-SOD resolves bleomycin-induced inflammation via increased apoptosis of recruited alveolar macrophages.

SAT-LB063 The ZFP36 Family of RNA-Binding Proteins Regulate Human Steroidogenesis

Human steroid hormones produced by the adrenal cortex control important physiology including metabolism, inflammation, blood pressure and volume, and sexual characteristics. While the signaling components, transcriptional regulators, and steroidogenic enzymes necessary for adrenocortical production of hormones have been identified, little to nothing is known about post-transcriptional regulation by RNA-binding proteins (RBPs). Recently technological advances have revolutionized our ability to investigate RBP-driven RNA regulation making it possible for the first time to investigate how this mechanism controls steroidogenesis. We have recently carried out an siRNA screen of RBPs regulating human aldosterone production that revealed a critical role for the tristetraprolin (ZFP36) family of RNA-binding protein. The ZFP36 family of RBPs binds to AU-rich elements in 3’UTRs and consequently destabilizes and/or translationally represses these ARE-containing mRNAs. Remarkably, depletion of either ZFP36L2 or ZFP36L1 significantly increased aldosterone levels. In addition, we have data demonstrating that: 1) mRNA stability controls the temporal pattern of RNA expression during steroidogenesis; 2) mRNAs with AU-rich elements (AREs) in their 3’ UTR are rapidly induced and cleared out in response to steroidogenic stimulation; 3) The ZFP36 family of RBPs are induced during steroidogenesis. We propose a model in which the ZFP36 family of proteins operate a negative feedback loop that prevent overproduction of aldosterone by destabilizing and/or translationally repressing ARE-containing mRNAs encoding steroidogenic proteins. Notably, over-production of aldosterone is a major cause of hypertension, suggesting that failure of this negative feedback loop could have important implications for human health. Our ongoing work will elucidate the mechanism underlying this negative feedback loop that controls aldosterone biosynthesis post-transcriptionally through the action of ZFP36 RNA binding proteins and yet to be discovered factors that they interact with. The adrenal cortex is amenable to the delivery of modified antisense oligonucleotides. Thus, our discoveries can facilitate the design of oligonucleotide therapeutics that can be used to precisely and specifically modulate human steroidogenesis. Unless otherwise noted, all abstracts presented at ENDO are embargoed until the date and time of presentation. For oral presentations, the abstracts are embargoed until the session begins. Abstracts presented at a news conference are embargoed until the date and time of the news conference. The Endocrine Society reserves the right to lift the embargo on specific abstracts that are selected for promotion prior to or during ENDO.

Abstract PD9-09: Proteomic analysis of extracellular matrix helps define drivers of metastatic progression

Tumor microenvironment (TME) plays a central role in the development of distant metastasis. However, given its complexity, successful targeting of TME will require a detailed understanding of its composition. Cancer-associated fibroblasts represent a large component of TME and are a major contributor to the extracellular matrix (ECM). Previously, we demonstrated the presence of two fibroblast sub-populations (CDCP1pos vs CD146pos fibroblasts) in breast cancer TME, which determine therapeutic response in estrogen receptor (ER) positive breast cancer. We hypothesized that the same fibroblast subtypes would also influence ECM composition and alter the metastatic potential of breast cancer cells. Here, we present the development of a novel fibroblast driven orthotopic model of ER+ breast cancer metastasis, which we combined with an innovative proteomics approach to precisely quantify extracellular matrix proteins.

Results: 1.CDCP1pos fibroblasts promote increased breast cancer cell mobility, invasion and metastasis compared to CD146pos fibroblasts.We demonstrate that CDCP1pos fibroblasts significantly increase the invasion potential of breast cancer cells, when compared to CD146pos fibroblasts. Orthotopic co-implantation of ER+ tumor cells with CDCP1pos fibroblasts into the mammary fat pad of mice more frequently drives distant organ metastases to lung and brain when compared with tumors implanted with CD146pos fibroblasts. 2. Proteomic analysis of ER+ tumors influenced by CDCP1pos fibroblasts revealed known and novel drivers of breast cancer metastasis. Breast cancer cells mixed with CDCP1pos fibroblasts produce a non-uniform collagen orientation to the tumor boarder. Our novel proteomic analysis of TME specific proteins revealed that tumors influenced by CDCP1pos fibroblasts have high expression of many ECM proteins linked to increased risk of breast cancer metastasis, including TNC, FN1, COL5A3, and FBN1 among others. Derived proteomic TME signature accurately predicted lymph node involvement in patients who presented with early stage (T0 and T1) tumors in a cohort of 1,009 breast cancer patients from Cancer Genome Atlas Database. 3. Inhibiting fibroblast production of Tenascin C (TNC) results in decreased breast cancer cell invasion. Our in vitro mixed co-culture models, which contain ER+ breast cancer cells with both fibroblast subtypes, demonstrate that only CDCP1pos fibroblasts produce TNC. Furthermore, in spheroid assays with CDCP1posfibroblasts and breast cancer tumor cells, invasion is inhibited by TNC knockdown. The invasion phenotype can be rescued by addition of EGF, which suggests TNC promotes invasion via EGFR signaling.

Conclusion: Metastatic spread of cancer cells relies heavily on TME alterations and makeup of the extracellular matrix. Our data suggest that fibroblast composition directly influences ECM properties and metastatic potential in breast cancer. Taken together, we believe that a better understanding of ECM composition will lead to a more personalized approach to breast cancer treatment.

Citation Format: Brechbuhl HM, Barrett AS, Kopin E, Gillen A, Hagen J, Johnson L, Finaly-Shultz J, Sartorius CA, Hansen KC, Kabos P. Proteomic analysis of extracellular matrix helps define drivers of metastatic progression [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr PD9-09.

valr: Reproducible genome interval analysis in R

New tools for reproducible exploratory data analysis of large datasets are important to address the rising size and complexity of genomic data. We developed the valr R package to enable flexible and efficient genomic interval analysis. valr leverages new tools available in the ”tidyverse”, including dplyr. Benchmarks of valr show it performs similar to BEDtools and can be used for interactive analyses and incorporated into existing analysis pipelines.

Integrating baseline health status data collection into the process of care

BACKGROUND

Health status data are an increasingly important component of outcomes assessment and can be used to facilitate quality assessment and improvement efforts. An enormous challenge to the use of health status data among hospitalized patients, however, is collecting baseline data at the time of treatment, an essential component for risk-adjusting subsequent outcomes. The Mid America Heart Institute of Saint Luke's Hospital (Kansas City, Mo), attempted to integrate the collection of health status assessments within the process of performing coronary revascularization.

THE DATA COLLECTION STRATEGY

The data collection strategy was developed for each admission portalelective outpatients (admissions for same-day procedures), inpatients, and emergent cases. Health status data were collected on all patients with coronary artery disease who were receiving a percutaneous coronary intervention or coronary artery bypass graft with no disruption to physician scheduling or nursing staff.

RESULTS

In general, patients were agreeable to completing the health status survey. Despite initial efforts to educate the hospital staff about the goal and purpose of health status assessment, staff members who were unaware of the uses of these data seemed to minimize their value. Providing examples of how to use these data relative to the staff member's specific occupational role facilitated buy-in for this project.

EPILOGUE

After the pilot study, which lasted until June 1999, data were continually collected for 18 months, through August 2000, even with the cessation of external grant funding for this project. Baseline data collection finally stopped, primarily because of a failure to accommodate data collection into the routine flow of patient care by existing nursing staff.

An antigen chimera of poliovirus induces antibodies against human papillomavirus type 16

It has been established that the surface of poliovirus type 1 can be extensively modified to incorporate antigenic domains from other poliovirus serotypes and from unrelated viruses. The fact that the modified (chimeric) viruses exhibit dual antigenicity and immunogenicity led us to explore the possibility of using the Sabin vaccine strain of poliovirus type 1 as a vector for the presentation of antigenic domains from human papillomavirus type 16 (HPV-16), a virus associated with the development of cervical carcinoma. We report here the construction and characterization of a chimeric poliovirus containing a 16-residue sequence derived from the major capsid protein (L1) of HPV-16. This virus chimera stimulated the production in rabbits of antibodies which recognized the HPV-16-derived peptide and an L1 fusion protein synthesized in Escherichia coli and detected HPV-16 in human biopsy material by immunoperoxidase staining. The possibility that poliovirus-HPV chimeras could be used as vaccines against HPV-16 is discussed.