A novel chalcone derivative which acts as a microtubule depolymerising agent and an inhibitor of P-gp and BCRP in in-vitro and in-vivo glioblastoma models

<p>Abstract</p> <p>Background</p> <p>Over the past decades, in spite of intensive search, no significant increase in the survival of patients with glioblastoma has been obtained. The role of the blood-brain barrier (BBB) and especially the activity of efflux pumps belonging to the ATP Binding Cassette (ABC) family may, in part, explain this defect.</p> <p>Methods</p> <p>The <it>in-vitro </it>activities of JAI-51 on cell proliferation were assessed by various experimental approaches in four human and a murine glioblastoma cell lines. Using drug exclusion assays and flow-cytometry, potential inhibitory effects of JAI-51 on P-gp and BCRP were evaluated in sensitive or resistant cell lines. JAI-51 activity on <it>in-vitro </it>microtubule polymerization was assessed by tubulin polymerization assay and direct binding measurements by analytical ultracentrifugation. Finally, a model of C57BL/6 mice bearing subcutaneous GL26 glioblastoma xenografts was used to assess the activity of the title compound <it>in vivo</it>. An HPLC method was designed to detect JAI-51 in the brain and other target organs of the treated animals, as well as in the tumours.</p> <p>Results</p> <p>In the four human and the murine glioblastoma cell lines tested, 10 μM JAI-51 inhibited proliferation and blocked cells in the M phase of the cell cycle, via its activity as a microtubule depolymerising agent. This ligand binds to tubulin with an association constant of 2 × 10⁵M^-1, overlapping the colchicine binding site. JAI-51 also inhibited the activity of P-gp and BCRP, without being a substrate of these efflux pumps. These <it>in vitro </it>studies were reinforced by our <it>in vivo </it>investigations of C57BL/6 mice bearing GL26 glioblastoma xenografts, in which JAI-51 induced a delay in tumour onset and a tumour growth inhibition, following intraperitoneal administration of 96 mg/kg once a week. In accordance with these results, JAI-51 was detected by HPLC in the tumours of the treated animals. Moreover, JAI-51 was detected in the brain, showing that the molecule is also able to cross the BBB.</p> <p>Conclusion</p> <p>These <it>in vitro </it>and <it>in vivo </it>data suggest that JAI-51 could be a good candidate for a new treatment of tumours of the CNS. Further investigations are in progress to associate the title compound chemotherapy to radiotherapy in a rat model.</p

Dynamic Performance of an HVDC Link

This paper presents the results of a simulation study on a 12 pulse HVDC (High Voltage Direct Current) using a system in Matlab/Simulink. The object of the study is to investigate the steady state and dynamic performance of the system. First we examine response of current regulator after change in current reference in order to see the behavior of the controllers in controlling the desired current. Next, we present the digital simulation of a test system and show the response to a DC fault in the line and the AC fault at inverter side. The results are evaluated to enhance the recovery of the system from the disturbances for a full range of typical disturbances. The presented approach benefits from Simulink’s advantages in modeling and simulating dynamical systems