Glioblastoma multiforme (GBM) is the most aggressive form of adult primary malignant brain tumour with poor prognosis. Extracellular vesicles (EVs) are a key-mediator through which GBM cells promote a pro-oncogenic microenvironment. Peptidylarginine deiminases (PADs), which catalyze the post-translational protein deimination of target proteins, are implicated in cancer, including via EV modulation. Pan-PAD inhibitor Cl-amidine affected EV release from GBM cells, and EV related microRNA cargo, with reduced pro-oncogenic microRNA21 and increased anti-oncogenic microRNA126, also in combinatory treatment with the chemotherapeutic agent temozolomide (TMZ). The GBM cell lines under study, LN18 and LN229, differed in PAD2, PAD3 and PAD4 isozyme expression. Various cytoskeletal, nuclear and mitochondrial proteins were identified to be deiminated in GBM, including prohibitin (PHB), a key protein in mitochondrial integrity and also involved in chemo-resistance. Post-translational deimination of PHB, and PHB protein levels, were reduced after 1 h treatment with pan-PAD inhibitor Cl-amidine in GBM cells. Histone H3 deimination was also reduced following Cl-amidine treatment. Multifaceted roles for PADs on EV-mediated pathways, as well as deimination of mitochondrial, nuclear and invadopodia related proteins, highlight PADs as novel targets for modulating GBM tumour communication.

No abstract

The unique electronic properties of lanthanide ions (longlived luminescence and sharp emission spectra) make them particularly suitable for the development of diagnostic tools in medical analysis. [1,2] Lanthanide complexes are increasingly used for sensor development [3] and as luminescent probes in time-resolved high-throughput assays and fluorescence imaging because of their ability to discriminate between background fluorescence and the target signal.[ ).[ [15][16][17][18] As the Laporte-forbidden 4f-4f transition prevents direct excitation of lanthanide luminescence, lanthanide ions require sensitization by suitable organic chromophores. Furthermore, for practical applications under physiological conditions, the lanthanide ion should be incorporated into highly stable complexes. The efficiency of ligand-to-lanthanide energy transfer, which requires compatibility between the energy levels of the ligand excited states and the accepting levels of lanthanide ions, is crucial in the design of highperformance probes.[19] Moreover, high quantum yield cannot be obtained without the prevention of nonradiative deactivation of the lanthanide excited states by OÀH oscillators of coordinated or closely diffusing water molecules. The incorporation of suitable chromophores in carefully designed polydentate ligands leads to increased stability of the lanthanide chelate in solution and allows for the metal center to be well protected from water molecules. However, the tendency of lanthanide ions to adopt high coordination numbers and their lack of stereochemical preferences make the design of such ligands very challenging.[20] A successful strategy adopted by several investigators relies on tripodal architectures for the organization of three tridentate binding units in nine-coordinate Ln iii complexes. [21][22][23][24][25] The design of polydentate ligands that allow the arrangement of four bidentate moieties around a lanthanide ion has received less attention in spite of the excellent luminescent properties observed for tetrakis complexes of bidentate chomophores, such as quinolinates [26] or tropolonates. [27] Recently, octadentate ligands incorporating four bidentate chromophores have been shown to yield lanthanide complexes with very efficient emissions in the visible or NIR regions. [15,28] The structures of these complexes have not been elucidated, but the highly flexible structure of the backbone that connects the bidentate units suggests nonoptimal protection of the metal center in such systems.Herein, we describe a new and particularly efficient way of assembling four picolinate chromophores around a lanthanide center with a multidentate ligand that yields highly luminescent and water-stable lanthanide complexes. The decadentate ligand N,N,N'N'-tetrakis[(6-carboxypyridin-2-yl)methyl]ethylenediamine (H 4 tpaen) is readily obtained in five steps from commercially available pyridine-2,6-dicarboxylic acid and ethylenediamine in a yield of 26 % (Scheme 1).The water-soluble complexes of tpaen were isolated in 50-60 % yie...