[Ecthyma gangrenosum associated with infection involving a methicillin-sensitive, Panton-Valentine-negative strain of Staphylococcus aureus]. / Ecthyma gangréneux dû à une souche de Staphylococcus aureus sensible à la méthicilline et non sécrétrice de toxine de Panton-Valentine.

BACKGROUND: Ecthyma gangrenosum (EG) is an anatomoclinical syndrome commonly associated with Pseudomonas aeruginosa cutaneous infection. Other microorganisms have also been incriminated on occasion, with other viral, fungal and bacterial agents potentially causing EG. In this report, we present an extremely rare case of an EG caused by methicillin-sensitive Staphylococcus aureus (MSSA) infection. This case, highly characteristic of EG both clinically and histologically, calls into question the physiopathological mechanisms of the disease and provides a reminder that it may be caused by a variety of organisms. PATIENTS AND METHODS: A 62-year-old woman, followed for HIV seropositivity at the AIDS stage, developed a painful purpuric skin rash evolving towards necrotic nodules characteristic of ecthyma gangrenosum. Skin biopsy confirmed the diagnosis of EG due to methicillin-sensitive S. aureus (MSSA) infection without toxins or bacteraemia. DISCUSSION: To the best of our knowledge, this is the first case in the literature in which MSSA is reported as the underlying cause of such lesions.

Role of the lean body mass and of pharmacogenetic variants on the pharmacokinetics and pharmacodynamics of sunitinib in cancer patients.

INTRODUCTION: Sunitinib is a multikinase inhibitor active in various cancers types including renal cancers and endocrine tumors. The study analyzed the influence of the lean body mass (LBM) and of pharmacogenetic variants on the exposure to sunitinib and its active metabolite, SU12662, and on sunitinib toxicity and clinical activity. MATERIALS AND METHODS: Exposure to sunitinib and SU12662 was assessed on days 10 and 21 during the first treatment cycle. Acute toxicity was graded using the NCI 4.0 CTCAE ver. 4.0. The LBM and 14 common single nucleotide polymorphisms in the CYP3A4/3A5, NR1I2, NR1I3, ABCB1, and ABCG2 genes were analyzed according to the drug exposure at day 10. Determinants (including sunitinib exposure and pharmacogenetic variants) for toxicities were assessed, as well as the relationship between drug exposure and survival in renal cancer patients. RESULTS: Ninety-two patients (60 % with renal cancer) were assessable for pharmacokinetics, toxicity and survival, and 66 for genetic analysis. The LBM (p < 0.0001) and a polymorphism in the ABCG2 transporter (421C>A) (p = 0.014) were two independent parameters accounting for the variability of composite (sunitinib + SU12662) exposure. Advanced age (OR = 1.47 [1.01-2.15], p = 0.048) and high sunitinib exposure (OR = 1.16 [1.05-1.28], p = 0.005) were independently associated with any grade ≥ 3 acute toxicity, and high SU12662 exposure was associated with grade ≥ 2 thrombocytopenia (OR = 1.27 [1.03-1.57], p = 0.028). A high composite area under the curve (AUC) >1,973 ng/mL∙h at day 21 was associated with a doubled survival (35.2 vs 16.7 months; log-rank p = 0.0051) in renal cancer patients. CONCLUSIONS: This study indicates that LBM and drug monitoring may be helpful in the management of sunitinib-treated patients.

The pathway of MAP kinase mediation of CSF arrest in Xenopus oocytes.

A cytoplasmic activity in mature oocytes responsible for second meiotic metaphase arrest was identified over 30 years ago in amphibian oocytes. In Xenopus oocytes CSF activity is initiated by the progesterone-dependent synthesis of Mos, a MAPK kinase kinase, which activates the MAPK pathway. CSF arrest is mediated by a sole MAPK target, the protein kinase p90Rsk which leads to inhibition of cyclin B degradation by the anaphase-promoting complex. Rsk phosphorylates and activates the Bub1 protein kinase, which may cause metaphase arrest due to inhibition of the anaphase-promoting complex (APC) by a conserved mechanism defined genetically in yeast and mammalian cells. CSF arrest in vertebrate oocytes by p90Rsk provides a potential link between the MAPK pathway and the spindle assembly checkpoint in the cell cycle.

The polo-like kinase Plx1 is required for activation of the phosphatase Cdc25C and cyclin B-Cdc2 in Xenopus oocytes.

In the Xenopus oocyte system mitogen treatment triggers the G(2)/M transition by transiently inhibiting the cAMP-dependent protein kinase (PKA); subsequently, other signal transduction pathways are activated, including the mitogen-activated protein kinase (MAPK) and polo-like kinase pathways. To study the interactions between these pathways, we have utilized a cell-free oocyte extract that carries out the signaling events of oocyte maturation after addition of the heat-stable inhibitor of PKA, PKI. PKI stimulated the synthesis of Mos and activation of both the MAPK pathway and the Plx1/Cdc25C/cyclin B-Cdc2 pathway. Activation of the MAPK pathway alone by glutathione S-transferase (GST)-Mos did not lead to activation of Plx1 or cyclin B-Cdc2. Inhibition of the MAPK pathway in the extract by the MEK1 inhibitor U0126 delayed, but did not prevent, activation of the Plx1 pathway, and inhibition of Mos synthesis by cycloheximide had a similar effect, suggesting that MAPK activation is the only relevant function of Mos. Immunodepletion of Plx1 completely inhibited activation of Cdc25C and cyclin B-Cdc2 by PKI, indicating that Plx1 is necessary for Cdc25C activation. In extracts containing fully activated Plx1 and Cdc25C, inhibition of cyclin B-Cdc2 by p21(Cip1) had no significant effect on either the phosphorylation of Cdc25C or the activity of Plx1. These results demonstrate that maintenance of Plx1 and Cdc25C activity during mitosis does not require cyclin B-Cdc2 activity.

The critical role of the MAP kinase pathway in meiosis II in Xenopus oocytes is mediated by p90(Rsk).

BACKGROUND: During oocyte maturation in Xenopus, progesterone induces entry into meiosis I, and the M phases of meiosis I and II occur consecutively without an intervening S phase. The mitogen-activated protein (MAP) kinase is activated during meiotic entry, and it has been suggested that the linkage of M phases reflects activation of the MAP kinase pathway and the failure to fully degrade cyclin B during anaphase I. To analyze the function of the MAP kinase pathway in oocyte maturation, we used U0126, a potent inhibitor of MAP kinase kinase, and a constitutively active mutant of the protein kinase p90(Rsk), a MAP kinase target. RESULTS: Even with complete inhibition of the MAP kinase pathway by U0126, up to 90% of oocytes were able to enter meiosis I after progesterone treatment, most likely through activation of the phosphatase Cdc25C by the polo-like kinase Plx1. Subsequently, however, U0126-treated oocytes failed to form metaphase I spindles, failed to reaccumulate cyclin B to a high level and failed to hyperphosphorylate Cdc27, a component of the anaphase-promoting complex (APC) that controls cyclin B degradation. Such oocytes entered S phase rather than meiosis II. U0126-treated oocytes expressing a constitutively active form of p90(Rsk) were able to reaccumulate cyclin B, hyperphosphorylate Cdc27 and form metaphase spindles in the absence of detectable MAP kinase activity. CONCLUSIONS: The MAP kinase pathway is not essential for entry into meiosis I in Xenopus but is required during the onset of meiosis II to suppress entry into S phase, to regulate the APC so as to support cyclin B accumulation, and to support spindle formation. Moreover, one substrate of MAP kinase, p90(Rsk), is sufficient to mediate these effects during oocyte maturation.

Human retinoblastoma protein (Rb) is phosphorylated by cdc2 kinase and MAP kinase in Xenopus maturing oocytes.

Xenopus oocyte meiotic maturation combines features of G0/G1 and G2/M transitions of the cell cycle. To study the in ovo Rb kinase activity, we have microinjected human Rb into oocytes. Microinjected human Rb localizes into the nucleus, is hypophosphorylated in prophase oocytes, becomes hyperphosphorylated during meiotic maturation and is dephosphorylated as the cell reenters interphase. Inactivation or overexpression of the cyclin D-cdk4/6 complex in an oocyte extract does not affect the Rb kinase activity. This kinase activity could be attributed to both cdc2-cyclin B and MAP kinase, opening new perspectives of investigation in somatic cells.

Increased stable retroviral gene transfer in early hematopoietic progenitors released from quiescence.

It has been previously demonstrated that prestimulation with cytokines could improve gene transfer in hematopoietic progenitors. However, we have shown that no combination of cytokines so far tested is able to release rapidly in vitro the stem cell compartment from quiescence unless an autocrine transforming growth factor-beta 1 (TGF-beta 1) is blocked by specific oligonucleotide antisense or antiserum (Hatzfeld et al., 1991, J. Exp. Med., 174, 925). We now report that a 10-hr cytokine prestimulation of SBA-CD34high human umbilical cord blood progenitors increases retrovirally mediated transfer of the nls-lacZ reporter gene from 1% to 23.8% and addition of anti-TGF-beta serum doubles this increase (47.3%). Interestingly, the effect of anti-TGF-beta preincubation on gene transfer is most effective on the most immature progenitors, which develop into high proliferative potential mixed colonies with 1-2 x 10(5) cells. Anti-TGF-beta serum pretreatment increases gene transfer in these early colony-forming units granulocyte-erythroid-megakaryocyte-macrophage (CFU-GEMM) from 54.1% to 93.3%. It augments significantly the stability of gene expression in all subpopulations of mixed colonies. Colonies obtained after pretreatment with anti-TGF-beta serum are larger and the expression of the stably integrated recombinant provirus does not reduce their size. This prestimulation method provides a substantial improvement for gene transfer efficiency within the quiescent stem cell compartment that is responsible for long-term engraftment.