Malignant progression in cancer requires populations of tumor-initiating cells (TICs

The encapsulation of mRNA in nanosystems as gene vaccines for immunotherapy purposes has experienced an exponential increase in recent years. Despite the many advantages envisaged within these approaches, their application in clinical treatments is still limited due to safety issues. These issues can be attributed, in part, to liver accumulation of most of the designed nanosystems and to the inability to transfect immune cells after an intravenous administration. In this context, this study takes advantage of the known versatile properties of the oligopeptide end-modified poly (β-amino esters) (OM-PBAEs) to complex mRNA and form discrete nanoparticles. Importantly, it is demonstrated that the selection of the appropriate end-oligopeptide modifications enables the specific targeting and major transfection of antigen-presenting cells (APC) in vivo, after intravenous administration, thus enabling their use for immunotherapy strategies. Therefore, with this study, it can be confirmed that OM-PBAE are appropriate systems for the design of mRNA-based immunotherapy approaches aimed to in vivo transfect APCs and trigger immune responses to fight either tumors or infectious diseases.

RNF8 is a ubiquitin ligase with a FHA domain near its N terminus, and a RING-finger domain at its C terminus, through which it recruits several ubiquitin-conjugating enzymes. In metazoans, only the mitotic checkpoint regulator CHFR shares this domain architecture. Here we show that RNF8 is a nuclear protein that follows a cellcycle-dependent turnover, reaching its highest levels in mitosis, followed by a strong decline in late mitotic stages. Overexpression of RNF8 caused a delay in cytokinesis and the frequent appearance of aberrant mitotic figures. These effects were dependent on the ubiquitin ligase activity of RNF8, since they were significantly attenuated when a RING-finger mutant, inactive as an E3, was overexpressed. Depletion of RNF8 also caused a delay in the exit from the mitotic arrest induced by nocodazole, associated with a reduced turnover of the APC/C substrate cyclin B1. These observations suggest that RNF8 regulates the rate of exit from mitosis and cytokinesis.

BackgroundSeveral pathways that control cell survival under stress, namely RNF8-dependent DNA damage recognition and repair, PCNA-dependent DNA damage tolerance and activation of NF-κB by extrinsic signals, are regulated by the tagging of key proteins with lysine 63-based polyubiquitylated chains, catalyzed by the conserved ubiquitin conjugating heterodimeric enzyme Ubc13-Uev.Methodology/Principal FindingsBy applying a selection based on in vivo protein-protein interaction assays of compounds from a combinatorial chemical library followed by virtual screening, we have developed small molecules that efficiently antagonize the Ubc13-Uev1 protein-protein interaction, inhibiting the enzymatic activity of the heterodimer. In mammalian cells, they inhibit lysine 63-type polyubiquitylation of PCNA, inhibit activation of NF-κB by TNF-α and sensitize tumor cells to chemotherapeutic agents. One of these compounds significantly inhibited invasiveness, clonogenicity and tumor growth of prostate cancer cells.Conclusions/SignificanceThis is the first development of pharmacological inhibitors of non-canonical polyubiquitylation that show that these compounds produce selective biological effects with potential therapeutic applications.