Regulation of DNA Repair Mechanism in Human Glioma Xenograft Cells both In Vitro and In Vivo in Nude Mice

Glioblastoma Multiforme (GBM) is the most lethal form of brain tumor. Efficient DNA repair and anti-apoptotic mechanisms are making glioma treatment difficult. Proteases such as MMP9, cathepsin B and urokinase plasminogen activator receptor (uPAR) are over expressed in gliomas and contribute to enhanced cancer cell proliferation. Non-homologous end joining (NHEJ) repair mechanism plays a major role in double strand break (DSB) repair in mammalian cells.Here we show that silencing MMP9 in combination with uPAR/cathepsin B effects NHEJ repair machinery. Expression of DNA PKcs and Ku70/80 at both mRNA and protein levels in MMP9-uPAR (pMU) and MMP9-cathepsin B (pMC) shRNA-treated glioma xenograft cells were reduced. FACS analysis showed an increase in apoptotic peak and proliferation assays revealed a significant reduction in the cell population in pMU- and pMC-treated cells compared to untreated cells. We hypothesized that reduced NHEJ repair led to DSBs accumulation in pMU- and pMC-treated cells, thereby initiating cell death. This hypothesis was confirmed by reduced Ku70/Ku80 protein binding to DSB, increased comet tail length and elevated γH2AX expression in treated cells compared to control. Immunoprecipitation analysis showed that EGFR-mediated lowered DNA PK activity in treated cells compared to controls. Treatment with pMU and pMC shRNA reduced the expression of DNA PKcs and ATM, and elevated γH2AX levels in xenograft implanted nude mice. Glioma cells exposed to hypoxia and irradiation showed DSB accumulation and apoptosis after pMU and pMC treatments compared to respective controls.Our results suggest that pMU and pMC shRNA reduce glioma proliferation by DSB accumulation and increase apoptosis under normoxia, hypoxia and in combination with irradiation. Considering the radio- and chemo-resistant cancers favored by hypoxia, our study provides important therapeutic potential of MMP9, uPAR and cathepsin B shRNA in the treatment of glioma from clinical stand point

Probabilistic decision making with spikes: From ISI distributions to behaviour via information gain

Computational theories of decision making in the brain usually assume that sensory 'evidence' is accumulated supporting a number of hypotheses, and that the first accumulator to reach threshold triggers a decision in favour of its associated hypothesis. However, the evidence is often assumed to occur as a continuous process whose origins are somewhat abstract, with no direct link to the neural signals - action potentials or 'spikes' - that must ultimately form the substrate for decision making in the brain. Here we introduce a new variant of the well-known multi-hypothesis sequential probability ratio test (MSPRT) for decision making whose evidence observations consist of the basic unit of neural signalling - the inter-spike interval (ISI) - and which is based on a new form of the likelihood function. We dub this mechanism s-MSPRT and show its precise form for a range of realistic ISI distributions with positive support. In this way we show that, at the level of spikes, the refractory period may actually facilitate shorter decision times, and that the mechanism is robust against poor choice of the hypothesized data distribution. We show that s-MSPRT performance is related to the Kullback-Leibler divergence (KLD) or information gain between ISI distributions, through which we are able to link neural signalling to psychophysical observation at the behavioural level. Thus, we find the mean information needed for a decision is constant, thereby offering an account of Hick's law (relating decision time to the number of choices). Further, the mean decision time of s-MSPRT shows a power law dependence on the KLD offering an account of Piéron's law (relating reaction time to stimulus intensity). These results show the foundations for a research programme in which spike train analysis can be made the basis for predictions about behavior in multi-alternative choice tasks

Effect of Macitentan on the Development of New Ischemic Digital Ulcers in Patients With Systemic Sclerosis DUAL-1 and DUAL-2 Randomized Clinical Trials

IMPORTANCE Digital ulcers in patients with systemic sclerosis are associated with pain and poor quality of life. Endothelin-1 promotes vasculopathy in systemic sclerosis after macitentan, an endothelin-1 blocker. OBJECTIVE To evaluate the efficacy of macitentan in reducing the number of new digital ulcers in patients with systemic sclerosis. DESIGN, SETTING, AND PARTICIPANTS Two international, randomized, double-blind, placebo-controlled trials (DUAL-1, DUAL-2) were conducted between January 2012 and February 2014. Participants were patients with systemic sclerosis and active digital ulcers at baseline. Target enrollment for each study was 285 patients. INTERVENTIONS Patients were randomized (1: 1: 1) to receive oral doses of 3 mg of macitentan, 10mg of macitentan, or placebo once daily and stratified according to number of digital ulcers at baseline (3). MAIN OUTCOMES AND MEASURES The primary outcome for each trial was the cumulative number of new digital ulcers from baseline to week 16. Treatment effect was expressed as the ratio between treatment groups. RESULTS In DUAL-1, among 289 randomized patients (mean age 51.2 years; 85.8% women), 226 completed the study. The adjusted mean number of new digital ulcers per patient over 16 weeks was 0.94 in the 3-mg macitentan group (n = 95) and 1.08 in the 10-mg macitentan group (n = 97) compared with 0.85 in the placebo group (n = 97) (absolute difference, 0.09 [95% CI, -0.37 to 0.54] for 3mg of macitentan vs placebo and 0.23 [-0.27 to 0.72] for 10mg of macitentan vs placebo). Among 265 patients randomized in DUAL-2 (mean age 49.6 years; 81.9% women), 216 completed the study. In DUAL-2, the adjusted mean number of new digital ulcers was 1.44 in the 3-mg macitentan group (n = 88) and 1.46 in the 10-mg macitentan group (n = 88) compared with 1.21 in the placebo group (n = 89) (absolute difference, 0.23 [95% CI, -0.35 to 0.82] for 3mg of macitentan vs placebo and 0.25 [95% CI, -0.34 to 0.84] for 10mg of macitentan vs placebo). Adverse events more frequently associated with macitentan than with placebo were headache, peripheral edema, skin ulcer, anemia, upper respiratory tract infection, diarrhea, and nasopharyngitis. CONCLUSIONS AND RELEVANCE Among patients with systemic sclerosis and active ischemic digital ulcers, treatment with macitentan did not reduce new digital ulcers over 16 weeks. These results do not support the use of macitentan for the treatment of digital ulcers in this patient population