Necrotizing Meningoencephalitis and Pneumonitis in a Simian Immunodeficiency Virus—infected Rhesus Macaque due to Acanthamoeba

Free-living amoebae of the genus Acanthamoeba can cause a fatal disease of the brain in humans called granulomatous amoebic encephalitis. We present a case of meningoencephalitis and pneumonitis in a simian immunodeficiency virus (SIV)-infected rhesus macaque caused by Acanthamoeba sp. The animal became ill 176 days after intravenous inoculation with SIVmac251 after a short history of weight loss and a sudden onset of hind limb paresis and abnormal head movements. Histopathologic examination of hematoxylin and eosin-stained tissues revealed multifocal to coalescing necrotizing neutrophilic meningoencephalitis and pneumonitis. Immunofluorescence and polymerase chain reaction were used to identify the genus of amoeba as Acanthamoeba. Immunohistochemistry of immune cell markers was used to characterize the animal's immune response to the opportunistic amoebic infection with features of both innate and adaptive cell-mediated immunity. Although not previously reported, the potential transmission to humans, either through environmental contamination or contact with an infected animal, makes this disease a threat to laboratory animal care staff and pathologists.

Phase stability of the nanolaminates V2Ga2C and (Mo1-xVx)2Ga2C from first-principles calculations

We here use first-principles calculations to investigate the phase stability of the hypothetical laminated material V₂Ga₂C and the related alloy (Mo_1–xV_x)₂Ga₂C, the latter for a potential parent material for synthesis of (Mo_1–xV_x)₂C, a new two-dimensional material in the family of so called MXenes.

We here use first-principles calculations to investigate the phase stability of the hypothetical laminated material V₂Ga₂C and the related alloy (Mo_1–xV_x)₂Ga₂C, the latter for a potential parent material for synthesis of (Mo_1–xV_x)₂C, a new two-dimensional material in the family of so called MXenes. We predict that V₂Ga₂C is thermodynamically stable with respect to all identified competing phases in the ternary V–Ga–C phase diagram. We further calculate the stability of ordered and disordered configurations of Mo and V in (Mo_1–xV_x)₂Ga₂C and predict that ordered (Mo_1–xV_x)₂Ga₂C for x ≤ 0.25 is stable, with an order–disorder transition temperature of ∼1000 K. Furthermore, (Mo_1–xV_x)₂Ga₂C for x = 0.5 and x ≥ 0.75 is suggested to be stable, but only for disordered Mo–V configurations, and only at elevated temperatures. We have also investigated the electronic and elastic properties of V₂Ga₂C; the calculated bulk, shear, and Young's modulus are 141, 94, and 230 GPa, respectively.

Order and disorder in quaternary atomic laminates from first-principles calculations

We report on the phase stability of chemically ordered and disordered quaternary MAX phases - TiMAlC, TiM2AlC2, MTi2AlC2, and Ti2M2AlC3 where M = Zr, Hf (group IV), M = V, Nb, Ta (group V), and M = Cr, Mo, W (group VI). At 0 K, layered chemically ordered structures are predicted to be stable for M from groups V and VI. By taking into account the configurational entropy, an order-disorder temperature Tdisorder can be estimated. TiM2AlC2 (M = Cr, Mo, W) and Ti2M2AlC3 (M = Mo, W) are found with Tdisorder > 1773 K and are hence predicted to be ordered at the typical bulk synthesis temperature of 1773 K. Other ordered phases, even though metastable at elevated temperatures, may be synthesized by non-equilibrium methods such as thin film growth. Furthermore, phases predicted not to be stable in any form at 0 K can be stabilized at higher temperatures in a disordered form, being the case for group IV, for MTi2AlC2 (M = V, Cr, Mo), and for Ti2M2AlC3 (M = V, Ta). The stability of the layered ordered structures with M from group VI can primarily be explained by Ti breaking the energetically unfavorable stacking of M and C where M is surrounded by C in a face-centered cubic configuration, and by M having a larger electronegativity than Al resulting in a fewer electrons available for populating antibonding Al-Al orbitals. The results show that these chemically ordered quaternary MAX phases allow for new elemental combinations in MAX phases, which can be used to add new properties to this family of atomic laminates and in turn prospects for tuning these properties.

Influence of boron vacancies on phase stability, bonding and structure of MB₂ (M = Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W) with AlB₂ type structure

Transition metal diborides in hexagonal AlB2 type structure typically form stable MB2 phases for group IV elements (M  =  Ti, Zr, Hf). For group V (M  =  V, Nb, Ta) and group VI (M  =  Cr, Mo, W) the stability is reduced and an alternative hexagonal rhombohedral MB2 structure becomes more stable. In this work we investigate the effect of vacancies on the B-site in hexagonal MB2 and its influence on the phase stability and the structure for TiB2, ZrB2, HfB2, VB2, NbB2, TaB2, CrB2, MoB2, and WB2 using first-principles calculations. Selected phases are also analyzed with respect to electronic and bonding properties. We identify trends showing that MB2 with M from group V and IV are stabilized when introducing B-vacancies, consistent with a decrease in the number of states at the Fermi level and by strengthening of the B-M interaction. The stabilization upon vacancy formation also increases when going from M in period 4 to period 6. For TiB2, ZrB2, and HfB2, introduction of B-vacancies have a destabilizing effect due to occupation of B-B antibonding orbitals close to the Fermi level and an increase in states at the Fermi level.

A theoretical investigation of mixing thermodynamics, age-hardening potential, and electronic structure of ternary M(1)1-x M(2)xB2 alloys with AlB2 type structure

Transition metal diborides are ceramic materials with potential applications as hard protective thin films and electrical contact materials. We investigate the possibility to obtain age hardening through isostructural clustering, including spinodal decomposition, or ordering-induced precipitation in ternary diboride alloys. By means of first-principles mixing thermodynamics calculations, 45 ternary M¹_1–xM²_xB₂ alloys comprising MⁱB₂ (Mⁱ = Mg, Al, Sc, Y, Ti, Zr, Hf, V, Nb, Ta) with AlB₂ type structure are studied. In particular Al_1–xTi_xB₂ is found to be of interest for coherent isostructural decomposition with a strong driving force for phase separation, while having almost concentration independent a and c lattice parameters. The results are explained by revealing the nature of the electronic structure in these alloys, and in particular, the origin of the pseudogap at E_F in TiB₂, ZrB₂, and HfB₂.

A critical evaluation of GGA + U modeling for atomic, electronic and magnetic structure of Cr2AlC, Cr2GaC and Cr2GeC

In this work we critically evaluate methods for treating electron correlation effects in multicomponent carbides using a GGA + U framework, addressing doubts from previous works on the usability of density functional theory in the design of magnetic MAX phases. We have studied the influence of the Hubbard U-parameter, applied to Cr 3d orbitals, on the calculated lattice parameters, magnetic moments, magnetic order, bulk modulus and electronic density of states of Cr2AlC, Cr2GaC and Cr2GeC. By considering non-, ferro-, and five different antiferromagnetic spin configurations, we show the importance of including a broad range of magnetic orders in the search for MAX phases with finite magnetic moments in the ground state. We show that when electron correlation is treated on the level of the generalized gradient approximation (U = 0 eV), the magnetic ground state of Cr2AC (A = Al, Ga, Ge) is in-plane antiferromagnetic with finite Cr local moments, and calculated lattice parameters and bulk modulus close to experimentally reported values. By comparing GGA and GGA + U results with experimental data we find that using a U-value larger than 1 eV results in structural parameters deviating strongly from experimentally observed values. Comparisons are also done with hybrid functional calculations (HSE06) resulting in an exchange splitting larger than what is obtained for a U-value of 2 eV. Our results suggest caution and that investigations need to involve several different magnetic orders before lack of magnetism in calculations are blamed on the exchange-correlation approximations in this class of magnetic MAX phases.

Mo2Ga2C: a new ternary nanolaminated carbide

We report the discovery of a new hexagonal Mo₂Ga₂C phase, wherein two Ga layers – instead of one – are stacked in a simple hexagonal arrangement in between Mo₂C layers.

Magnetic self-organized atomic laminate from first principles and thin film synthesis

The first experimental realization of a magnetic M(n+1)AX(n) (MAX) phase, (Cr(0.75)Mn(0.25))(2)GeC, is presented, synthesized as a heteroepitaxial single crystal thin film, exhibiting excellent structural quality. This self-organized atomic laminate is based on the well-known Cr(2)GeC, with Mn, a new element in MAX phase research, substituting Cr. The compound was predicted using first-principles calculations, from which a variety of magnetic behavior is envisaged, depending on the Mn concentration and Cr/Mn atomic configuration within the sublattice. The analyzed thin films display a magnetic signal at room temperature.

Abstract P4-02-08: Quantitative Characterization of 3D Vasculature Spatial Patterns Within Tumor Microenvironment of Breast Cancer Stem Cells

The sustainment characters of cancer stem cells (CSCs) such as self-renew and differentiation to other tumor cells greatly depend on the tumor microenvironment, which is composed of many components, e.g. vasculature, extracellular matrix, epithelial cells, stromal cells, as well as nutrients and oxygen. As vasculature is an important factor for the CSC and tumor development, the understanding of their spatial patterns is essential for calibrating the CSC-microenvironment interactions in mathematical modeling. In this study, we acquired the vasculature in side tumors and normal breast tissues by using two-photon fluorescence microscopy, which enables 3D in vivo imaging. We developed an advanced vasculature segmentation approach for an objective and accurate quantification of the vasculature in 3D image volumes. The approach integrates supervoxel analysis and the orientation guided hidden Markov random field (ori-HMRF) modeling together to compensate for low quality images, e.g., low signal-to-noise ratio (SNR) and uneven background. By constructing a new feature space that combines the CIELAB color space and the coordinates space, the supervoxel analysis divides an image volume into subregions with local similar intensity and restricted regular shape, boundaries of which can delineate the vasculature boundaries accurately even in low intensity contrast regions. We further designed a set of features for the separation of blood vessel regions from the background. To make use of the context information, i.e. the continuity of vasculature, the ori-HMRF model is used to incorporate the consistency of vasculatures' orientation in order to reduce the false positives and negatives. Experimental results on image volumes from both breast cancer and normal breast tissues show that the proposed method can effectively reconstruct the vasculature structure with the CSC embedded tumor microenvironment.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P4-02-08.

Abstract P5-03-08: A fluorescence STAT3 reporter preferentially expressed in human breast cancer tumor-initiating cells

Cancer initiating/stem cells are thought to be responsible for treatment-resistance, disease-recurrence and metastasis. Current breast cancer stem cell markers lack direct correlation with stem cell function, which makes the targeted therapeutic design difficult. The STAT3 pathway is a critical regulator of the function of normal stem cells and evidence is accumulating for its important role in breast cancer stem cells, as well as associated “niche” cells. However, due to lack of method for pathway-activity-based live cell separation, whether STAT3 functions in the cancer stem cells themselves or in surrounding niche cells, or both remains unknown. To answer this question, we have constructed lentiviral fluorescent reporters, which enables FACS-sorting of cells differ in STAT3 activity as well as in vivo/in situ localization of STAT3 responsive cells. Our study for the first time separated the STAT3 positive and STAT3 negative cells from the same breast tumor in live, and for the first time provided functional evidences that the STAT3 positive cells are enriched for breast cancer stem cells compared to STAT3 negative cells, as tumor cells positive for reporter activity perform better in both mammosphere formation and dilution transplantation assays compared to the negatives.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P5-03-08.

PD08-05: Stat3 Signaling in Human Breast Cancer Stem Cells

Recent data suggest the existence of a unique subset of breast cancer cells capable of initiating tumor growth and giving rise to all other cells characteristic of a given tumor. These cells have been termed “cancer stem cells” or “tumor-initiating cells”. Breast cancer stem cells appear to be resistant to chemo- and radiotherapies and may be responsible for recurrence and metastasis in breast cancer patients. Identifying the cellular signaling pathways responsible for breast cancer stem cell maintenance and self-renewal represents a critical hurdle for developing effective therapeutics. The Stat3 pathway is a critical regulator of the function of normal stem cells, and shows altered expression in human breast cancers [4]. Moreover, IL-6, the Stat3 signaling agonist, is required for breast cancer stem cell function in human breast cancer cell lines. All these suggest an important role of Stat3 signaling in breast cancer stem cells. However, due to lack of method for pathway-activity-based live cell separation, whether Stat3 functions in the cancer stem cells themselves or whether it may function in surrounding niche cells remain unknown. We have constructed a lentiviral fluorescent reporter for Stat3 signaling which contains four copies of M67 Stat3 binding sites upstream of enhanced Green Fluorescent Protein. This reporter system enables FACS-sorting of cells with active Stat3 signaling and in vivo/in situ localization of Stat3 responsive cells. In addition, C188-9, the first Stat3 specific competitive inhibitor, has been developed in our collaborator's lab, which provides us an advanced tool in studying Stat3 function.

We hypothesize that Stat3 signaling is preferentially active in stemlike subpopulation and depend on non-stem cancer cells to maintain its activation. Three aims to test this hypothesis include: 1. To test whether cancer cells with activated Stat3 signaling are enriched for breast cancer stem cells or whether they may serve as niche cells. 2. To test whether small molecule antagonists of Stat3 signaling can inhibit cancer stem cell function. 3. To identify novel targets of Stat3 signaling that may serve as indicators of responsiveness to Stat3 antagonist or predict treatment response.

So far, our GFP reporters for Stat3 signaling effectively report Stat3 activity in both patient xenografts and human breast cancer cell lines in vivo and in vitro, which enables effective separation of Stat3+/Stat3- cells for functional Study. MDA231 and SUM159 tumors with reporters have been established. Tumor cells will be sorted according to Stat3 activity and perform limiting dilution and MSFE assays. Tumors with reporters will also be treated by C188-9, Chemo, or in combination to study synergistic effect of Stat3 inhibitors on tumor growth. Preliminary data based on inhibitor and limiting dilution studies suggested that Stat3 signaling is required for stem cell function. However, neither Stat3+ nor Stat3- cells are self-sufficient in performing these functions, indicating communications between subpopulations.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr PD08-05.

The Role of Smoothened in Mammary Gland Development and Breast Cancer

The hedgehog (Hh) signaling pathway is a critical pathway for development and is known to influence proliferation, cell fate, morphogenesis, and stem cell self-renewal. Mutations activating Hh signaling have been found in a wide variety of cancers, and it is estimated that up to 25% of all tumors display misregulated Hh signaling. Smoothened (Smo), a seven pass transmembrane protein is the Hh signaling pathway's primary effector and its sole non-redundant member. In a recent study, Smo was found to be over-expressed in 70% of ductal carcinom in-situ (DCIS) lesions and 30% of invasive breast carcinomas (IBC). Despite the implication of this protein in breast cancer, little is known about its role in normal mammary gland development.In order to understand the role of Smo in mammary gland development we have performed phenotypic analyses of a conditional mouse model expressing constitutively activated Smo under the control of a mammary gland selective Cre recombinase. We show that activation of the Hh pathway results in increased proliferation starting around five weeks of age that leads to a dramatic increase in branching and budding of the mammary gland at around ten weeks of age. In addition, immunostaining using the ductal markers Na-K-Cl Co-transporter 1 (NKCC1) and aquaporin 5 (AQP5) suggests alterations in cell fate. Finally, these mice exhibit changes in the stroma surrounding the mammary ducts including an increase in collagen deposition. Gene profiling studies show upregulation of several genes, including targets of the Notch pathway, in ten-week-old virgin mammary glands from the constitutively active conditional Smo mouse model when compared to control. Surprisingly, canonical downstream Hh target genes like Patched and Gli were not found to be upregulated. These data in conjunction with recent published studies suggest that Smo activation in the mammary gland may be acting via a non-canonical mechanism to produce the observed hyper-branched and budded phenotype. Preliminary studies indicate that Smoothened may be functioning as a G-protein coupled receptor (GPCR) via a pertussis-toxin sensitive mechanism. Interestingly, constituitive Smo activity does not appear to alter cyclic AMP (cAMP) levels as recently reported in Drosophila indicating that mammalian Smo may be acting via a different mechanism.In addition to these gain-of-function studies, experiments are underway utilizing a conditional null Smo mouse model (loss-of-function) to determine if there is a requirement for Hh pathway activation in normal mammary gland development. Preliminary analysis indicates that partial loss of Smo in mammary gland cells leads to impaired ductal elongation and reduced branching.Future studies will include the generation of mammary gland chimeras to study the possible paracrine interactions between Smo over-expressing and wild type cells. Additionally, experiments are under way to elucidate the mechanism of Smo's GPCR function in the mammary gland.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 2164.

Signal-Transduction Based Network Biomarkers for Tumor-Initiating Cells in a p53-Null Mouse Model of Breast Cancer

Introduction: Tumor initiating cells (TICs), or cancer stem cells, have the capacity to self-renew, and are likely to be responsible for resistance to conventional therapies, disease recurrence, and metastasis. Known TIC biomarkers may allow us to understand which genes are critical to self-renewal of TICs. However, little is known about how these biomarkers manipulate other molecules to enable TICs to self-renew. Here, we develop a systems biology approach to identify the signal-transduction network biomarkers for understanding the mechanisms in the renewal of TICs.Methods: Comparing with conventional biomarker discovery, the network biomarkers are identified by not only differential genes but also protein-protein interaction (PPI) network and available signaling pathways. Depending on the interacting patterns in PPI network and their associated cellular processes in signaling pathways, we can reveal the key signal transductions or subnetworks responsible for self-renewal of TICs. We chose two types of enriched interacting patterns, i.e. triangle and spoon, to indicate the signal transductions around the single biomarkers. A published RNA microarray (GSE8863) was performed on mammary epithelial cells from p53-null tumors sorted by two stem cell markers CD29 and CD24. The differential genes were identified by the Fold-Changes (FCs) comparing the subpopulations of Lin —CD29HCD24H with other subpopulations. Gene Set Enrichment Analysis (GSEA) revealed that the identified differential genes are significantly enriched in 20 regulatory pathways including 'Cell cycle', 'Adherens junction', 'Cell adhesion molecules (CAMs)', 'Tight junction' (P<10-3). A model called Multiple Objective Optimization (MOO) was employed to search the network biomarkers whose component proteins satisfy that (1) be most differentially expressed in Lin —CD29HCD24H cells and (2) pass through a large number of enriched signaling pathways.Results: Four genes (Lsm5, Calm3, Bmi1 and Ezh2) are extremely up-regulated in the Lin —CD29HCD24H subpopulations (FC>4), in which Bmi1 is important in regulating the self-renewal capacity of hematopoietic, as well as human mammary gland stem cells. To understand how these genes manipulate other genes and the enriched signaling pathways, we first analyzed the interacting patterns around these genes. Calm3 and Bmi1 are surrounded by 355 and 22 interacting patterns respectively. The component coding-genes in the interacting patterns are more likely to be differentially expressed (91/127, P <10-61). Then, the protein-paths were identified from the interacting patterns of Calm3 and Bmi1 by MOO. IPA (Ingenuity Pathway Analysis) indicated that these protein paths have many particular cellular functions related to self-renewal, such as 'Cell Growth and Proliferation', 'Hematological System Development and Function', 'Cell-To-Cell Signaling and Interaction', and 'Cell Death' (P <10-3).Conclusion: The network biomarkers revealed that the surrounding interaction patterns and related signaling pathways of single biomarkers are essential to understand the signal-transduction mechanisms of TICs in self-renewal. They may be useful as prognostic or predictive indicators as well as suggest possible targets for novel therapies.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 2138.

Hyperthermia Sensitizes Breast Cancer Stem Cells to Radiation Therapy

Background In cancer, metastatic disease and recurrence are hypothesized to result, at least in part, from the residual cancer stem cells (CSCs), also referred to as tumor-initiating cells(TICs), which evade initial treatment. In several genetically engineered mouse models that resemble human breast cancer, the tumor subpopulation CD29+/CD24+/lin- has been shown to be more tumorigenic as compared to other subpopulations by in vitro and in vivo assays. We and others have demonstrated that the tumorigenic CD29+/CD24+/lin- subpopulation repairs radiation-induced DNA strand breaks more efficiently than the other subpopulations. Therefore, we hypothesized that hyperthermia, a documented means of inhibiting DNA repair, may radiosensitize CSCs to radiation therapy(RT) by delaying and inhibiting the repair of DNA strand breaks. Methods To test this hypothesis, we assayed for tumorigenic CD29+/CD24+/lin- cells in p53null mouse mammary tumor model with and without radiation, and in combination with hyperthermia (42°C) administered as optically-activated gold nanoparticles. We then determined if there was a decrease in functional CSCs by FACS analysis and limiting dilution transplantation assays. Results These studies confirmed that CD29+/CD24+/lin- cells were more radiation resistant and that their relative proportion was increased after RT, as compared to the other cell populations. However, the addition of hyperthermia increased the sensitivity of the CD29+/CD24+/lin- subpopulation to radiation. Radiation treatment alone in vivo resulted in a decrease in tumor size, but the percentage of tumorigenic cells increased as compared to untreated controls. In contrast, following post-treatment with 20 minutes of local hyperthermia, using intravenously administered optically activated gold nanoparticles, a larger regression in tumor size was observed, without a concomitant increase in the percentage of CD29+/CD24+/lin- tumorigenic cells. Using the functional limiting dilution transplantation assay to assay for CSCs, we showed that 48 hours after treatment cells derived from tumors treated with RT exhibited an increased frequency of TICs as compared to untreated controls, and tumors treated with radiation and hyperthermia. In addition, clonogenic survival assays of this tumorigenic subpopulation had consistent results with the in vivo data. Conclusion These results suggest that localized hyperthermia serves as a simple strategy to selectively sensitize the radioresistant subpopulation of CSCs to enhance their response to radiation therapy. The mechanisms responsible for these effects of hyperthermia are currently under investigation. Supported by grant NCI R01 CA112305 and CA16303.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 506.

Amorphous and crystalline phases in thermal quench simulations of alumina

The authors report molecular dynamics simulations of alumina (Al2O3) during crystallization from the melt. Using liquid quench methods, they investigate the effect of cooling rate on the structural evolution of the alpha, kappa, and the bixbyite phases. A critical temperature window is identified, where the time spent in this window is crucial in determining the extent to which the systems approach crystallinity. A strong dependence is observed between the final structure and the quench rate, which is most pronounced for the alpha phase and to lesser extent for the other phases. The results show that the different phases have different tendencies to crystallize that are determined by energetics, complexity of crystal structure, and the number of metastable states.