CHK2 PHOSPHORYLATION OF SURVIVIN-DEX3 CONTRIBUTES TO A DNA DAMAGE-SENSING CHECKPOINT IN CANCER

Survivin is a pivotal cancer gene with multiple roles in cell viability and mitosis, but the function(s) of its alternatively spliced isoforms has remained elusive. Here, we show that a survivin spliced variant that lacks exon 3 and contains a unique -COOH terminus sequence, survivin-DEx3, is differentially expressed in cancer, compared to normal tissues, and correlates with aggressive disease and markers of unfavorable prognosis, by genome-wide bioinformatics analysis. Unlike other survivin variants, survivin-DEx3 localizes exclusively to nuclei in tumor cells, and is phosphorylated by the DNA damage checkpoint kinase, Chk2, on residues located in its unique -COOH terminus. Ala mutagenesis of the Chk2 phosphorylation sites prolongs survivin-DEx3 stability in tumor cells, inhibits the expression of Ser139 phosphorylated H2AX in response to double strand DNA breaks, and impairs colony formation in soft agar after DNA damage. Active Chk2 was detected at the earliest stages of the colorectal adenoma-to-carcinoma transition, persisted in advanced tumors, and correlated with increased survivin expression, in vivo. These data suggest that Chk2 phosphorylation of survivin-DEx3 contributes to a DNA damage-sensing checkpoint in tumor cells, which may affect sensitivity to genotoxic therapies

Evaluation of finite-element calculations in a part-circular crack by coherent optics techniques

Two techniques, speckle photography and holographic interferometry, were used to test three-dimensional finite-element calculations in an internally pressurized cylinder with an external part-circular crack. Opening displacements along the crack line were measured by speckle photography. Radial displacements were obtained from holographic fringe patterns. Good agreement between experimental and numerical data is obtained. Stress-intensity factor variations along the crack front are calculated from numerical results

Survivin family proteins as novel molecular determinants of doxorubicin resistance in organotypic human breast tumors

Introduction: The molecular determinants of breast cancer resistance to first-line anthracycline-containing chemotherapy are unknown.Methods: We examined the response to doxorubicin of organotypic cultures of primary human breast tumors ex vivo with respect to cell proliferation, DNA damage and modulation of apoptosis. Samples were analyzed for genome-wide modulation of cell death pathways, differential activation of p53, and the role of survivin family molecules in drug resistance. Rational drug combination regimens were explored by high-throughput screening, and validated in model breast cancer cell types.Results: Doxorubicin treatment segregated organotypic human breast tumors into distinct Responder or Non Responder groups, characterized by differential proliferative index, stabilization of p53, and induction of apoptosis. Conversely, tumor histotype, hormone receptor or human epidermal growth factor receptor-2 (HER2) status did not influence chemotherapy sensitivity. Global analysis of cell death pathways identified survivin and its alternatively spliced form, survivin-\u394Ex3 as uniquely overexpressed in Non Responder breast tumors. Forced expression of survivin-\u394Ex3 preserved cell viability and prevented doxorubicin-induced apoptosis in breast cancer cell types. High-throughput pharmacologic targeting of survivin family proteins with a small-molecule survivin suppressant currently in the clinic (YM155) selectively potentiated the effect of doxorubicin, but not other chemotherapeutics in breast cancer cell types, and induced tumor cell apoptosis.Conclusions: Survivin family proteins are novel effectors of doxorubicin resistance in chemotherapy-naive breast cancer. The incorporation of survivin antagonist(s) in anthracycline-containing regimens may have improved clinical activity in these patients. \ua9 2014 Faversani et al.; licensee BioMed Central Ltd

Activation of Hsp90 Enzymatic Activity and Conformational Dynamics through Rationally Designed Allosteric Ligands

Hsp90 is a molecular chaperone of pivotal importance for multiple cell pathways. ATP-regulated internal dynamics are critical for its function and current pharmacological approaches block the chaperone with ATP-competitive inhibitors. Herein, a general approach to perturb Hsp90 through design of new allosteric ligands aimed at modulating its functional dynamics is proposed. Based on the characterization of a first set of 2-phenylbenzofurans showing stimulatory effects on Hsp90 ATPase and conformational dynamics, new ligands were developed that activate Hsp90 by targeting an allosteric site, located 65 æ from the active site. Specifically, analysis of protein responses to first-generation activators was exploited to guide the design of novel derivatives with improved ability to stimulate ATP hydrolysis. The molecules’ effects on Hsp90 enzymatic, conformational, cochaperone and client-binding properties were characterized through biochemical, biophysical and cellular approaches. These designed probes act as allosteric activators of the chaperone and affect the viability of cancer cell lines for which proper functioning of Hsp90 is necessary

Anti-tumor activity of selective inhibitors of XPO1/CRM1-mediated nuclear export in diffuse malignant peritoneal mesothelioma : the role of survivin

Survivin, which is highly expressed and promotes cell survival in diffuse malignant peritoneal mesothelioma (DMPM), exclusively relies on exportin 1 (XPO1/ CRM1) to be shuttled into the cytoplasm and perform its anti-apoptotic function. Here, we explored the efficacy of Selective Inhibitors of Nuclear Export (SINE), KPT-251, KPT-276 and the orally available, clinical stage KPT-330 (selinexor), in DMPM preclinical models. Exposure to SINE induced dose-dependent inhibition of cell growth, cell cycle arrest at G1-phase and caspase-dependent apoptosis, which were consequent to a decrease of XPO1/CRM1 protein levels and the concomitant nuclear accumulation of its cargo proteins p53 and CDKN1a. Cell exposure to SINE led to a time-dependent reduction of cytoplasmic survivin levels. In addition, after an initial accumulation, the nuclear protein abundance progressively decreased, as a consequence of an enhanced ubiquitination and proteasome-dependent degradation. SINE and the survivin inhibitor YM155 synergistically cooperated in reducing DMPM cell proliferation. Most importantly, orally administered SINE caused a significant antitumor effect in subcutaneous and orthotopic DMPM xenografts without appreciable toxicity. Overall, we have demonstrated a marked efficacy of SINE in DMPM preclinical models that may relay on the interference with survivin intracellular distribution and function. Our study suggests SINE-mediated XPO1/ CRM1 inhibition as a novel therapeutic option for DMPM

SLC12A2 variants cause a neurodevelopmental disorder or cochleovestibular defect

The SLC12 gene family consists of SLC12A1–SLC12A9, encoding electroneutral cation-coupled chloride co-transporters. SCL12A2 has been shown to play a role in corticogenesis and therefore represents a strong candidate neurodevelopmental disorder gene. Through trio exome sequencing we identified de novo mutations in SLC12A2 in six children with neurodevelopmental disorders. All had developmental delay or intellectual disability ranging from mild to severe. Two had sensorineural deafness. We also identified SLC12A2 variants in three individuals with non-syndromic bilateral sensorineural hearing loss and vestibular areflexia. The SLC12A2 de novo mutation rate was demonstrated to be significantly elevated in the deciphering developmental disorders cohort. All tested variants were shown to reduce co-transporter function in Xenopus laevis oocytes. Analysis of SLC12A2 expression in foetal brain at 16–18 weeks post-conception revealed high expression in radial glial cells, compatible with a role in neurogenesis. Gene co-expression analysis in cells robustly expressing SLC12A2 at 16–18 weeks post-conception identified a transcriptomic programme associated with active neurogenesis. We identify SLC12A2 de novo mutations as the cause of a novel neurodevelopmental disorder and bilateral non-syndromic sensorineural hearing loss and provide further data supporting a role for this gene in human neurodevelopment