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Percorrer por autor "Howarth, Alison"

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  • Annexin A2 regulates AKT upon H2O2-dependent signaling activation in cancer cells
    Publication . Castaldo, Stéphanie Anais; Ajime, Tom; Serrão Fernandes, Lina Gisela; Anastácio, Fábio; Rosa, Joana Teixeira; Giacomantonio, Carman Anthony; Howarth, Alison; Hill, Richard; Madureira, Patricia
    Hydrogen peroxide (H2O2) is a main second messenger in oncogenic signaling networks including the Ras and the growth factor receptor pathways. This is achieved predominantly through the oxidation of redox-sensitive cysteine (Cys) residues in proteins resulting in changes to their structure and function. We previously identified annexin A2 (ANXA2) as a redox regulatory protein that plays an important cellular role during oxidative stress and also promoting tumorigenesis. Here we investigated the role of ANXA2 in the regulation of H2O2-dependent signaling that drives tumor progression. We show that depletion of ANXA2 leads to the enhanced activation of AKT following either EGF/EGFR stimulation or oncogenic Ras transformation. The phosphatase and tensin homologue (PTEN) protein negatively regulates the PI3K/AKT pathway. We demonstrate that ANXA2 via its reactive Cys-8 residue, binds to PTEN and that the co-expression of PTEN and ANXA2, but not ANXA2 Cys-8-Ala mutant, inhibits AKT phosphorylation on Ser 473. These results indicate that ANXA2 is important for PTEN regulation within the PI3K/AKT signaling cascade. Furthermore, we also reveal that ANXA2 inversely regulates the expression of the peroxidase, peroxiredoxin 2, in a reactive oxygen species dependent manner.
    2019-04-07Artigo científico Acesso aberto Ver mais
  • DIVERSet JAG compounds inhibit topoisomerase II and are effective against adult and pediatric high-grade gliomas
    Publication . Howarth, Alison; Simms, Claire; Kerai, Nitesh; Allen, Olivia; Mihajluk, Karina; Madureira, Patricia; Sokratous, Giannis; Cragg, Simon; Lee, Sang Y.; Morley, Andy D.; Ashkan, Keyoumars; Cox, Paul A.; Pilkington, Geoffrey J.; Hill, Richard
    High-grade gliomas (HGGs) are aggressive primary brain tumors with local invasive growth and poor clinical prognosis in both adult and pediatric patients. Clinical response is compounded by resistance to standard frontline antineoplastic agents, an absence of novel therapeutics, and poor in vitro models to evaluate these. We screened a range of recently identified anticancer compounds in conventional adult, pediatric, and new biopsy-derived HGG models. These in vitro lines showed a range of sensitivity to standard chemotherapeutics, with varying expression levels of the prognostic markers hypoxia-induced factor (HIF) 1α and p53. Our evaluation of lead DIVERSet library compounds identified that JAG-6A, a compound that was significantly more potent than temozolomide or etoposide, was effective against HGG models in two-dimensional and three-dimensional systems; mediated this response by the potent inhibition of topoisomerase Iiα; remained effective under normoxic and hypoxic conditions; and displayed limited toxicity to non-neoplastic astrocytes. These data suggest that JAG-6A could be an alternative topoisomerase IIα inhibitor and used for the treatment of HGG.
    2019Artigo científico Acesso aberto Ver mais