A Limited Role for the Cell Cycle Regulator Cyclin A1 in Murine Leukemogenesis

The quest for novel therapeutic targets in acute myeloid leukemia (AML) is still ongoing. One of such targets, cyclin A1, was shown to be overexpressed in AML including AML stem cells. However, the function of cyclin A1 in AML is largely unknown, and the data on its impact on patients´ survival remain controversial. Therefore, we developed a transgenic mouse model of stem cell-directed inducible cyclin A1 overexpression and crossed these mice with PML-RARα-knockin mice, which develop an AML M3-like phenotype. To observe the effects of cyclin A1 loss-of-function, we also crossed PML-RARα-knockin mice to cyclin A1-knockout mice. Neither overexpression nor loss of cyclin A1 significantly altered leukemogenesis in PML-RARα-knockin mice. These findings imply that upregulation of cyclin A1 is not essential for leukemogenesis. Our data suggest that cyclin A1 does not represent a suitable target for AML therapy

RAC1(P29S) Induces a Mesenchymal Phenotypic Switch via Serum Response Factor to Promote Melanoma Development and Therapy Resistance

RAC1 P29 is the third most commonly mutated codon in human cutaneous melanoma, after BRAF V600 and NRAS Q61. Here, we study the role of RAC1P29S in melanoma development and reveal that RAC1P29S activates PAK, AKT, and a gene expression program initiated by the SRF/MRTF transcriptional pathway, which results in a melanocytic to mesenchymal phenotypic switch. Mice with ubiquitous expression of RAC1P29S from the endogenous locus develop lymphoma. When expressed only in melanocytes, RAC1P29S cooperates with oncogenic BRAF or with NF1-loss to promote tumorigenesis. RAC1P29S also drives resistance to BRAF inhibitors, which is reversed by SRF/MRTF inhibitors. These findings establish RAC1P29S as a promoter of melanoma initiation and mediator of therapy resistance, while identifying SRF/MRTF as a potential therapeutic target

Corrosion protection of different environmentally friendly coatings on powder metallurgy magnesium

Pure magnesium was processed by a powder metallurgy (PM) route to generate microstructural features that provide higher mechanical properties than those of cast pure magnesium and commercial AZ31 alloy. Nevertheless, corrosion resistance of PM Mg needs to be improved if this material is to be used for structural applications in a corrosive medium. In the present work, the corrosion protection effectiveness of three simple, economical and environmentally friendly coatings has been evaluated over immersion time in a chloride-containing solution. A silane coating, an anticorrosive paint formulated with ion-exchangeable pigments (IEPs) and a chemical conversion treatment to form a MgF2 layer have been studied. Silane film and anticorrosive paint enhance the corrosion behaviour of PM Mg during the first hours of immersion, but their protection effectiveness completely disappears after 2 days. For longer immersion times, the fluoride conversion coating may be considered the only viable and effective barrier to protect PM magnesium from degradation. © 2010 Elsevier B.V. All rights reserved.Peer Reviewe

Cyclin A1 expression in human and murine leukemic blasts.

<p>A. and B. Cyclin A1 was analyzed in mRNA microarray expression data from the purified fraction of human mononuclear bone marrow cells after Ficoll density centrifugation [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0129147#pone.0129147.ref018" target="_blank">18</a>,<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0129147#pone.0129147.ref019" target="_blank">19</a>]. A. The expression of cyclin A1 was significantly increased in AML blasts compared to normal bone marrow (NBM) (p<0.001, t-test). Shown here are log arbitrary units. B. The expression of cyclin A1 was significantly decreased in AML blasts with complex karyotype and increased in AML M3 blasts compared with normal karyotype and (*p<0.001, t-test). C. Cyclin A1 expression was significantly induced in bone marrow cells from human AML patients with FAB subtype M3 (p = 0.015, t-test) and with FAB subtype M5/5a/5b (p = 0.05, two-tailed t-test) compared to normal bone marrow cells (NBM). Cyclin A1 expression was determined by qRT-PCR and normalized to GAPDH expression level. D. In bone marrow cells of PML-RARα-knockin mice, cyclin A1 expression was significantly upregulated upon a full-blown leukemic phenotype compared to non-leukemic PML-RARα-knockin mice (p = 0.04, t-test).</p

Development of a cyclin A1-transgenic mouse model.

<p>A. Schematic overview about the constructs used to develop transgenic mouse lines. The driver mouse line SCL-tTA expresses the tetracycline-dependent transactivator protein (tTA) in hematopoietic stem cells under the control of the stem cell leukemia-factor enhancer [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0129147#pone.0129147.ref023" target="_blank">23</a>,<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0129147#pone.0129147.ref024" target="_blank">24</a>]. In the novel cyclin A1-bi-luciferase responder mouse line, the cDNA of cyclin A1 and luciferase as reporter gene were expressed in absence of tetracycline in parallel and inducibly under control of the bidirectional tTA-responsive promoter element Pbi-1. B. Bars indicate expression levels of human cyclin A1 expression as detected by qRT-PCR in bone marrow cells that were transduced with a retroviral tTA-containing construct and cultured with or without tetracycline in methylcellulose for 10 days (n = 2 for each sample). C. Three months old mice carrying either cyclin A1 alone (control) or together with the driver construct SCL-tTA (SCL-tTAxcyclinA1-tg; n = 3 for each genotype) were induced for seven weeks and investigated for luciferase activity and cyclin A1 mRNA in the bone marrow and spleen. High luciferase activity was only detectable in induced SCL-tTAxcyclinA1-tg bone marrow and spleen cells. Numbers indicate mean luciferase levels.</p

Cyclin A1 expression does not significantly influence PML-RARα-driven leukemogenesis.

<p>A. Kaplan-Meier survival curves of heterozygous PML-RARα-knockin mice with (SCL-cyclinA1-tg; n = 12) or without (control; n = 14) ectopic human cyclin A1 expression in the bone marrow. Although there was a trend towards an accelerated disease in the presence of ectopic cyclin A1 expression, latency and penetrance did not differ significantly between the two genotypes (p = 0.282, log-rank test). Also, the phenotype of acute myeloid leukemia was not changed by the presence of cyclin A1 (B). Shown here are examples of FACS analysis of bone marrow (upper panels) and spleen cells (lower panels) of diseased mice. Murine PML-RARα-driven leukemic blasts are characterized by the surface expression of CD34 and GR-1 which does not occur in non-leukemic mice. The number of CD34⁺/GR-1⁺ cells in diseased mice did not alter significantly upon cyclin A1 expression. SCL, Stem Cell Leukemia enhancer driving tTA expression [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0129147#pone.0129147.ref023" target="_blank">23</a>]; FI, fluorescent intensity; P/Rα-KI, PML-RARα-knockin mice. C. Kaplan-Meier survival curves of PML-RARα-knockin mice with wild type (PML-RARα-KI/cyclin A1^+/+; n = 30) or cyclin A1-knockout (PML-RARα-KI/cyclin A1^-/-; n = 35). Cyclin A1^-/- mice without PML-RARα-expression did not develop a lethal phenotype (control/cyclinA1^-/-; n = 3). Absence of murine cyclin A1 did not affect PML-RARα-driven leukemia. D. The PML-RARα-leukemic phenotype was not altered by the absence or presence of murine cyclin A1. May-Grünwald staining of blood smears showed the same distribution of leukemic blasts and high numbers of differentiated myeloid cells (upper panels). FACS analysis revealed comparable numbers of myeloid cells in the blood (CD11b⁺/GR-1⁺, lower panels).</p

A low incidence of preoperative neurosonographic abnormalities in neonates with heart defects

Background and aim: To investigate whether neonates with prenatally detected congenital heart defects (CHD) demonstrate cerebral abnormalities on early preoperative cranial ultrasound (CUS), compared to healthy neonates, and to measure brain structures to assess brain growth and development in both groups. Study design, subjects and outcome measures: Prospective cohort study with controls. Between September 2013 and May 2016 consecutive cases of prenatally detected severe isolated CHD were included. Neonatal CUS was performed shortly after birth, before surgery and in a healthy control group. Blinded images were reviewed for brain abnormalities and various measurements of intracranial structures were compared. Results: CUS was performed in 59 healthy controls and 50 CHD cases. Physiological CUS variants were present in 54% of controls and in 52% of CHD cases. Abnormalities requiring additional monitoring (both significant and minor) were identified in four controls (7%) and five CHD neonates (10%). Significant abnormalities were only identified in four CHD neonates (8%) and never in controls. A separate analysis of an additional 8 CHD neonates after endovascular intervention demonstrated arterial stroke in two cases that underwent balloon atrioseptostomy (BAS). Cerebral measurements were smaller in CHD neonates, except for the cerebrospinal fluid measurements, which were similar to the controls. Conclusions: The prevalence of significant preoperative CUS abnormalities in CHD cases was lower than previously reported, which may be partially caused by a guarding effect of a prenatal diagnosis. Arterial stroke occurred only in cases after BAS. As expected, neonates with CHD display slightly smaller head size and cerebral growth