SAMHD1 expression contributes to doxorubicin resistance and predicts survival outcomes in diffuse large B-cell lymphoma patients

Diffuse large B-cell lymphoma (DLBCL) is a commonly diagnosed, aggressive non-Hodgkin's lymphoma. While R-CHOP chemoimmunotherapy is potentially curative, about 40% of DLBCL patients will fail, highlighting the need to identify biomarkers to optimize management. SAMHD1 has a dNTPase-independent role in promoting resection to facilitate DNA double-strand break (DSB) repair by homologous recombination. We evaluated the relationship of SAMHD1 levels with sensitivity to DSB-sensitizing agents in DLBCL cells and the association of SAMHD1 expression with clinical outcomes in 79 DLBCL patients treated with definitive therapy and an independent cohort dataset of 234 DLBCL patients. Low SAMHD1 expression, Vpx-mediated, or siRNA-mediated degradation/depletion in DLBCL cells was associated with greater sensitivity to doxorubicin and PARP inhibitors. On Kaplan-Meier log-rank survival analysis, low SAMHD1 expression was associated with improved overall survival (OS), which on subset analysis remained significant only in patients with advanced stage (III-IV) and moderate to high risk (2-5 International Prognostic Index (IPI)). The association of low SAMHD1 expression with improved OS remained significant on multivariate analysis independent of other adverse factors, including IPI, and was validated in an independent cohort. Our findings suggest that SAMHD1 expression mediates doxorubicin resistance and may be an important prognostic biomarker in advanced, higher-risk DLBCL patients.

AZD5582 plus SIV-specific antibodies reduce lymph node viral reservoirs in antiretroviral therapy-suppressed macaques

The main barrier to HIV cure is a persistent reservoir of latently infected CD4+ T cells harboring replication-competent provirus that fuels rebound viremia upon antiretroviral therapy (ART) interruption. A leading approach to target this reservoir involves agents that reactivate latent HIV proviruses followed by direct clearance of cells expressing induced viral antigens by immune effector cells and immunotherapeutics. We previously showed that AZD5582, an antagonist of inhibitor of apoptosis proteins and mimetic of the second mitochondrial-derived activator of caspases (IAPi/SMACm), induces systemic reversal of HIV/SIV latency but with no reduction in size of the viral reservoir. In this study, we investigated the effects of AZD5582 in combination with four SIV Env-specific Rhesus monoclonal antibodies (RhmAbs) ± N-803 (an IL-15 superagonist) in SIV-infected, ART-suppressed rhesus macaques. Here we confirm the efficacy of AZD5582 in inducing SIV reactivation, demonstrate enhancement of latency reversal when AZD5582 is used in combination with N-803 and show a reduction in total and replication-competent SIV-DNA in lymph-node-derived CD4+ T cells in macaques treated with AZD5582 + RhmAbs. Further exploration of this therapeutic approach may contribute to the goal of achieving an HIV cure.

Viral Particle-Mediated SAMHD1 Depletion Sensitizes Refractory Glioblastoma to DNA-Damaging Therapeutics by Impairing Homologous Recombination

Simple Summary

Glioblastoma (GBM) is a lethal and common primary brain tumor that accounts for about 50% of all diagnosed malignant gliomas. Despite aggressive standard-of-care treatment of surgical resection followed by γ-irradiation (IR) and DNA alkylating agent temozolomide (TMZ), the average post-diagnosis survival time for a GBM patient remains at 15 months. This is mainly due to acquired resistance and limited therapeutic options. Sterile alpha motif and HD domain-containing protein 1 (SAMHD1) supports DNA double-strand break repair by promoting homologous recombination (HR) and it can be targeted to proteasomal degradation by viral protein X (Vpx). We aim to evaluate whether depleting SAMHD1 sensitizes refractory GBM to IR and TMZ, and the possibility of utilizing Vpx as therapeutic tool. We report that SAMHD1 is highly expressed in GBM. Vpx-mediated SAMHD1 depletion impaired HR and sensitized GBM cells to IR and TMZ. Our finding demonstrates the potential therapeutic benefit of targeting SAMHD1 with Vpx in GBM.

Abstract

The current standard-of-care treatment for glioblastoma includes DNA damaging agents, γ-irradiation (IR) and temozolomide (TMZ). These treatments fail frequently and there is limited alternative strategy. Therefore, identifying a new therapeutic target is urgently needed to develop a strategy that improves the efficacy of the existing treatments. Here, we report that tumor samples from GBM patients express a high level of SAMHD1, emphasizing SAMHD1’s importance. The depletion of SAMHD1 using virus-like particles containing Vpx, VLP(+Vpx), sensitized two independent GBM cell lines (LN-229 and U-87) to veliparib, a well-established PARP inhibitor, and slowed cell growth in a dose-dependent manner. In the mouse GBM xenograft model, Vpx-mediated SAMHD1 depletion reduced tumor growth and SAMHD1 knockout (KO) improved survival. In combination with IR or TMZ, SAMHD1 KO and exposure to 50% growth inhibitory dose (gID50) of VLP(+Vpx) displayed a synergistic effect, resulting in impaired HR, and improved LN-229 cells’ sensitivity to TMZ and IR. In conclusion, our finding demonstrates that SAMHD1 promotes GBM resistance to treatment, and it is a plausible therapeutic target to improve the efficacy of TMZ and IR in GBM. Furthermore, we show that Vpx could be a potential therapeutic tool that can be utilized to deplete SAMHD1 in GBM.

Novel mouse hemostasis model for real-time determination of bleeding time and hemostatic plug composition

INTRODUCTION

Hemostasis is a rapid response by the body to stop bleeding at sites of vessel injury. Both platelets and fibrin are important for the formation of a hemostatic plug. Mice have been used to uncover the molecular mechanisms that regulate the activation of platelets and coagulation under physiologic conditions. However, measurements of hemostasis in mice are quite variable, and current methods do not quantify platelet adhesion or fibrin formation at the site of injury.

METHODS

We describe a novel hemostasis model that uses intravital fluorescence microscopy to quantify platelet adhesion, fibrin formation and time to hemostatic plug formation in real time. Repeated vessel injuries of ~ 50-100 μm in diameter were induced with laser ablation technology in the saphenous vein of mice.

RESULTS

Hemostasis in this model was strongly impaired in mice deficient in glycoprotein Ibα or talin-1, which are important regulators of platelet adhesiveness. In contrast, the time to hemostatic plug formation was only minimally affected in mice deficient in the extrinsic tissue factor (TF(low)) or the intrinsic factor IX coagulation pathways, even though platelet adhesion was significantly reduced. A partial reduction in platelet adhesiveness obtained with clopidogrel led to instability within the hemostatic plug, especially when combined with impaired coagulation in TF(low) mice.

CONCLUSIONS

In summary, we present a novel, highly sensitive method to quantify hemostatic plug formation in mice. On the basis of its sensitivity to platelet adhesion defects and its real-time imaging capability, we propose this model as an ideal tool with which to study the efficacy and safety of antiplatelet agents.

Molecular Beam Epitaxial Growth of Very High Mobility Two-Dimensional Electron Gases in Si/GeSi Heterostructures

We report the fabrication of modulation doped Si/Gex Si1−x heterostructures by molecular beam epitaxy. The samples are characterized by Rutherford backscattering spectrometry, cross-sectional transmission electron microscopy, electron beam induced current, Hall measurement, and the magnetoresistance (Shubnikov-de Haas) measurements. Threading dislocation densities of = 106cm−2 are observed for relaxed Ge0.3Si0.7 films on Si (100). The modulation doped structures fabricated on these Ge0.3 Si0.7 films contain two-dimensional electron gases with mobilities ranging from 60,000 to 96,000 cm2/V - s at 4.2 K.

1/f Noise in the Tunneling Current of thin Gate Oxides

We have observed fluctuations in the tunneling current through 3.5 nm gate oxides with a 1/f power spectrum where f is the frequency. For voltages in the direct tunneling regime we lind an anomalous current dependence of the noise relative to previous observations of noise in thin oxides. We present a simplified model for the current noise in terms of fluctuations in a trap assisted tunneling current that exists in the oxide in addition to the direct tunneling current. Current noise appears to be a very sensitive probe of trap assisted tunneling and degradation in oxides.

Abnormal hemostasis in a knock-in mouse carrying a variant of factor IX with impaired binding to collagen type IV

BACKGROUND

Factor IX binds to collagen type IV, but this binding has no known consequence.

OBJECTIVES

To determine the effect of reduced binding of FIX to collagen IV.

METHODS

We constructed and characterized 'knock-in' mice containing the mutation lysine 5 to alanine (K5A) in the Gla domain of their FIX. The K5A mutation dramatically reduced the affinity of FIX for collagen type IV, but had no measurable effect on platelet binding, phospholipid binding, or in vitro clotting activity. However, K5AFIX mice had a mild bleeding tendency, despite their in vitro clotting activity being normal. Hemostatic protection from delayed rebleeding was intermediate between wild-type and hemophilia B mice (which had no detectable clotting activity); moreover, survival of K5A FIX mice after nascent clot removal was dramatically improved as compared with hemophilia B mice. Importantly, there was no detectable difference between K5AFIX and wild-type mice in either a laser-induced thrombosis model or the chromogenic FIX activity assay. In contrast, after ferric chloride injury, which exposes collagen IV as well as other basement membrane proteins, intravital microscopy revealed that vessel occlusion was significantly slower in K5AFIX mice than in wild-type mice.

CONCLUSIONS

Our results indicate that the FIX molecule with decreased affinity for collagen IV has altered hemostatic properties in vivo and that the binding of FIX to collagen IV probably plays a significant functional role in hemostasis.

Dehydroepiandrosterone and related steroids alter 3T3-L1 preadipocyte proliferation and differentiation

The purpose of the present study was to determine if the anti-adipogenic effects of dehydroepiandrosterone (DHEA) are mediated solely by DHEA or by one or more of its downstream metabolites. In Experiment 1, preconfluent proliferating cultures of 3T3-L1 preadipocytes were incubated for either 24 or 72 h with 0, 1, 5 or 25 microM DHEA, DHEA sulfate (DHEAS), testosterone, estrone and 17beta-estradiol. Pregnenolone, a precursor of DHEA(S), was also tested at these concentrations. After 24 h of incubation, DHEAS, 17beta-estradiol and estrone at the 1 microM level stimulated preadipocyte proliferation. In contrast, DHEA and 17beta-estradiol at the 25 microM level attenuated proliferation to a greater extent than all other steroids. After 72 h of incubation, DHEA and 17beta-estradiol at the 25 microM level attenuated proliferation to a greater extent than all other steroids. In Experiment 2, post-confluent cultures of differentiating 3T3-L1 preadipocytes were incubated for 6 days with 0, 5, 30, or 60 microM levels of these steroids. Preadipocyte differentiation, as assessed by lipid content and glycerol-3-phosphate dehydrogenase activity, decreased markedly when treated with 30 and 60 microM DHEA, 17beta-estradiol, estrone and pregnenolone. In contrast, DHEAS had no impact on preadipocyte proliferation or differentiation. These results suggest that the anti-adipogenic actions of DHEA in adipose tissue may be mediated, in part, by one or more of its distal metabolites, including 17beta-estradiol.

Previous donor pregnancy as a risk factor for acute graft-versus-host disease in patients with aplastic anaemia treated by allogeneic marrow transplantation

To determine if previous donor pregnancies influence the development of acute graft-versus-host disease (GVHD) we evaluated data from 136 patients with aplastic anaemia greater than 15 years of age and given marrow grafts from HLA-identical sibling donors. Of the 136 marrow donors, 30 were parous females (previous history of pregnancy), 30 were nulliparous females (no history of pregnancy or abortions), and 76 were males. The cumulative incidence of grade II-IV GVHD was 57%, 21% and 46% for patients with parous, nulliparous and male donors, respectively. A multivariate analysis of the data confirmed that the risk of grade II-IV acute GVHD was significantly increased among patients receiving marrow from parous females as compared to those from nulliparous females (relative risk = 2.5, P = 0.02). There was no statistically significant difference in the incidence of acute GVHD, however, between patients with parous donors and male donors (relative risk = 1.3, P = 0.26). Male patients given grafts from parous donors showed a higher incidence of acute GVHD (63%) than female patients (45%), though this difference was not statistically significant. The 5-year probability of survival was 47% for patients with parous donors, 68% for patients with nulliparous donors and 70% for those with male donors. We confirm that prior donor pregnancy represents an important factor in selecting marrow donors or designing clinical protocols for GVHD prophylaxis.

Amperometric immunoassay

An exciting new analytical technique based on amperometric devices used to measure immunoassays is reviewed in this article. The utility, ease, speed, simplicity, and many other advantages of performing amperometric immunoassays (AIAs) are discussed throughout the review. Limitations are also described, with electrochemical comparisons being made between AIAs and other conventional analytical methods, including potentiometric immunoassays. The review essentially consists of a general AIA overview, followed by sections devoted to amperometric electrode types, assay design, basic principles, automation, application, and future use. Operational features of oxygen gas selective electrodes and oxidoreductase probes are discussed for a better understanding of AIA principles. Characteristics, limits, advantages, and disadvantages of these different devices are presented. A variety of homogeneous and heterogeneous AIAs are described, together with many applications of the different assay formats available. AIAs are classified according to the electrode type employed, enzyme labels required, or electrochemical components involved. Important related AIAs discussed include pulse agglutination reactions and bioaffinity or displacement assays.

Patient teaching for X-ray and other diagnostics

Many patients scheduled for diagnostic tests want to know in detail what they will experience. Here are the first in a new series of patient guides to X-ray exams.

Potentiometric (bioselective electrodes) assay systems: utility and limitations

Numerous potentiometric assays utilizing bioselective electrodes are fast revolutionizing many areas of biotechnology. Adequately discussing the utility and limitations of these electrochemical systems is the purpose of this review. A general overview introduces bioselective potentiometry by presenting basic concepts, historical background, and current developments. Essentially, the review consists of several sections describing electrode architecture, operational concepts, different biosensors, assay systems, applications, and future trends. Advantages and disadvantages of the different bioselective assay systems discussed are included throughout each section. Electrode design discussion covers conventional liquid probes and the newer solid-state transitor biosensors. Limitations and advantages of different chemoreceptors, biocatalysts, and potentiometric transducers are presented. Operational characteristics include: linear behavior, sensitivity, stability, specificity, response, recovery, and the influence of interfering factors. Enzyme, organelle, tissue, and microbial biocatalytic sensors are discussed. Bioligand systems include: affinity, immunoselective enzyme, and liposome sensors. Potentiometric bioselective drug, microbial, and immunoassay systems are also included.

Therapy of severe aplastic anemia with anti-human thymocyte globulin and androgens: the effect of HLA-haploidentical marrow infusion

Fifty-four patients with severe aplastic anemia were treated with horse anti-human thymocyte globulin (ATG) and androgens. Thirty of these patients also received an infusion of HLA-haploidentical marrow cells. Only those patients having evidence of hematologic recovery within 3 mo after ATG therapy were considered responders to the immunosuppressive regimen. Of 53 patients evaluable for response, 21 had complete or partial responses and 7 had minimal improvement by defined criteria. The remaining patients did not respond or died. Factors correlated with response to therapy included a short duration of aplasia and a high admission granulocyte count. Thirty-six patients (66.7%) are surviving between 18 and 43 mo, and 18 have died. Deaths were due to hemorrhage and/or infection. Short duration of aplasia and high granulocyte counts also correlated with survival, as did younger age. Four patients with complete or partial responses had a recurrence of severe aplasia 6-17 mo after their first course of ATG. Three of these patients were retreated with ATG (and oxymetholone in two cases). All three had second responses to therapy, but two of the three have had second relapses. The fourth patient responded to oxymetholone alone, but died after a second relapse. Mismatched marrow infusion had no effect on the incidence of response or survival.