Staphylococcus Aureus Endocarditis associated with Injecting New Psychoactive Substances

Background

Staphylococcus aureus infective endocarditis (IE) associated with injection of new psychoactive substances (NPS) in Edinburgh from 2014 to 2016 was observed. We compared these infections with a series of S. aureus IE cases in a non-injecting population within Edinburgh.

Methods

NPS-associated S. aureus IE diagnosed between 1 January 2014 and 31 May 2016 in persons who inject drugs (PWID) were compared with a series of S. aureus IE cases from non-PWID.

Results

There was a fourfold increase in the annual incidence of S. aureus IE, mainly due to NPS use in PWID. A larger vegetation diameter was seen on echocardiogram in PWID vs non-PWID (median 1.7 cm vs 0.65 cm; p = 0.009) with more embolic complications in PWID (15 PWID vs 1 non-PWID; p = 2.1 x 10-7) but no difference in 90-day mortality (2 PWID vs 4 non-PWID; p = 0.39).

Conclusions

NPS-associated S. aureus IE correlated with complications, such as deep organ embolic abscesses, that were different from non-PWID S. aureus IE. The alarming increase in incidence resolved with targeted public health and legislative measures.

FLT3 K663Q is a novel AML-associated oncogenic kinase: Determination of biochemical properties and sensitivity to Sunitinib (SU11248)

Somatic mutations of FLT3 resulting in constitutive kinase activation are the most common acquired genomic abnormality found in acute myeloid leukemia (AML). The majority of these mutations are internal tandem duplications (ITD) of the juxtamembrane region (JM). In addition, a minority of cases of AML are associated with mutation of the FLT3 activation loop (AL), typically involving codons D835 and/or I836. We hypothesized that other novel mutations of FLT3 could also contribute to leukemogenesis. We genotyped 109 cases of AML and identified two novel gain-of-function mutations. The first mutation, N841 H, is similar to previously described mutations involving amino-acid substitutions of codon 841. The other novel mutation, FLT3 K663Q, is the first AML-associated gain-of-function mutation located outside the JM and AL domains. Of note, this mutation was potently inhibited by Sunitinib (SU11248), a previously described FLT3 kinase inhibitor. Sunitinib reduced the proliferation and induced apoptosis of transformed Ba/F3 cells expressing FLT3 K663Q. The potency of Sunitinib against FLT3 K663Q was similar to its potency against FLT3 ITD mutations. We conclude that FLT3 mutations in AML can involve novel regions of the TK1. Future studies are needed to define the incidence and prognostic significance of FLT3 mutations outside the well-established JM and AL regions.

Co-transduction of cDNAs for c-kit and steel factor into single CD34+ cord blood cells further enhances the growth of erythroid and multipotential progenitors

Previous studies have demonstrated that the c-kit encoded tyrosine kinase receptor and its ligand, steel factor (SLF), are critical for normal blood cell development. We have reported that transduction of the c-kit gene into single hematopoietic progenitor cells (HPC), CD34(+++) cells, from cord blood (CB) enhances erythroid colony formation via a SLF-dependent mechanism. We therefore decided to evaluate the impact on cell proliferation of co-transducing c-kit and SLF cDNAs into these cells. CD34(+++) cells were sorted as a population or as 1 cell/well for cells expressing the highest levels of CD34 and different levels of c-kit. Cells were then prestimulated with granulocyte macrophage (GM)-colony stimulating factor (CSF), interleukin (IL)-3, IL-6, erythropoietin (Epo) in the presence and absence of various concentrations of SLF. Cells were then transduced with SLF and/or c-kit cDNAs, and then assayed for colony formation with the same cytokine combination. At a single cell level, co-transduction with c-kit and SLF genes significantly enhanced colony formation compared with individual gene transduction, especially by erythroid and multipotential progenitors that responded to stimulation by added cytokines. Little or no growth was seen with the c-kit- and/or SLF-transduced cells without addition of cytokines. The degree of enhancement effected by co-transduction inversely correlated with the degree of expression of c-kit protein before transduction. Optimal enhancing effects were noted in CD34(+++) kit(Lo/-) cells co-transduced with both c-kit and SLF cDNAs. Reverse transcriptase-polymerase chain (RT-PCR) analysis of SLF mRNA expression in CD34(+++) cells and enzyme-linked immunoadsorbent assay (ELISA) measurement of secreted SLF protein demonstrated that the transduced SLF cDNA was expressed and soluble SLF was released in medium cultured with SLF gene transduced MACS-separated CD34(+) cells in the presence, but not in the absence, of IL-3, GM-CSF, IL-6, and Epo. These results demonstrate the enhancement of the proliferation of growth factor responsive HPC that express transduced c-kit and SLF genes.

Inhibition of c-kit receptor tyrosine kinase activity by STI 571, a selective tyrosine kinase inhibitor

STI 571 (formerly known as CGP 57148B) is a known inhibitor of the c-abl, bcr-abl, and platelet-derived growth-factor receptor (PDGFR) tyrosine kinases. This compound is being evaluated in clinical trials for the treatment of chronic myelogenous leukemia. We sought to extend the activity profile of STI 571 by testing its ability to inhibit the tyrosine kinase activity of c-kit, a receptor structurally similar to PDGFR. We treated a c-kit expressing a human myeloid leukemia cell line, M-07e, with STI 571 before stimulation with Steel factor (SLF). STI 571 inhibited c-kit autophosphorylation, activation of mitogen-activated protein (MAP) kinase, and activation of Akt without altering total protein levels of c-kit, MAP kinase, or Akt. The concentration that produced 50% inhibition for these effects was approximately 100 nmol/L. STI 571 also significantly decreased SLF-dependent growth of M-07e cells in a dose-dependent manner and blocked the antiapoptotic activity of SLF. In contrast, the compound had no effect on MAP kinase activation or cellular proliferation in response to granulocyte-macrophage colony-stimulating factor. We also tested the activity of STI 571 in a human mast cell leukemia cell line (HMC-1), which has an activated mutant form of c-kit. STI 571 had a more potent inhibitory effect on the kinase activity of this mutant receptor than it did on ligand-dependent activation of the wild-type receptor. These findings show that STI 571 selectively inhibits c-kit tyrosine kinase activity and downstream activation of target proteins involved in cellular proliferation and survival. This compound may be useful in treating cancers associated with increased c-kit kinase activity.

Posttranscriptional cell cycle-dependent regulation of human FANCC expression

The Fanconi Anemia (FA) Group C complementation group gene (FANCC) encodes a protein, FANCC, with a predicted M(r) of 63,000 daltons. FANCC is found in both the cytoplasmic and the nuclear compartments and interacts with certain other FA complementation group proteins as well as with non-FA proteins. Despite intensive investigation, the biologic roles of FANCC and of the other cloned FA gene products (FANCA and FANCG) remain unknown. As an approach to understanding FANCC function, we have studied the molecular regulation of FANCC expression. We found that although FANCC mRNA levels are constant throughout the cell cycle, FANCC is expressed in a cell cycle-dependent manner, with the lowest levels seen in cells synchronized at the G1/S boundary and the highest levels in the M-phase. Cell cycle-dependent regulation occurred despite deletion of the 5' and 3' FANCC untranslated regions, indicating that information in the FANCC coding sequence is sufficient to mediate cell cycle-dependent regulation. Moreover, inhibitors of proteasome function blocked the observed regulation. We conclude that FANCC expression is controlled by posttranscriptional mechanisms that are proteasome dependent. Recent work has demonstrated that the functional activity of FA proteins requires the physical interaction of at least FANCA, FANCC, and FANCG, and possibly of other FA and non-FA proteins. Our observation of dynamic control of FANCC expression by the proteasome has important implications for understanding the molecular regulation of the multiprotein complex. (Blood. 2000;95:3970-3977)

Core temperature rhythms in normal and tumor-bearing mice

The core temperature temporal behavior of DBA/2 mice (11 normal and 13 with an ascites tumor) was studied using surgically implanted radio telemetry transmitters. Normal mice continuously displayed a stable 24 hour temperature rhythm. Tumor-bearers displayed a progressive deterioration of the temperature rhythm following inoculation with tumor cells. While such disruptions have been noted by others, details on the dynamics of the changes have been mostly qualitative, often due to time-averaging or steady-state analysis of the data. The present study attempts to quantify the dynamics of the disruption of temperature rhythm (when present) by continuously monitoring temperatures over periods up to a month. Analysis indicated that temperature regulation in tumor-bearers was adversely affected during the active period only. Furthermore, it appears that the malignancy may be influencing temperature regulation via pathways not directly attributable to the energy needs of the growing tumor.