Nuclear localization signal-tagged systems: relevant nuclear import principles in the context of current therapeutic design

Nuclear targeting of therapeutics provides a strategy for enhancing efficacy of molecules active in the nucleus and minimizing off-target effects. 'Active' nuclear-directed transport and efficient translocations across nuclear pore complexes provide the most effective means of maximizing nuclear localization. Nuclear-targeting systems based on nuclear localization signal (NLS) motifs have progressed significantly since the beginning of the current millennium. Here, we offer a roadmap for understanding the basic mechanisms of nuclear import in the context of actionable therapeutic design for developing NLS-therapeutics with improved treatment efficacy.

Assessment of the quality of atmospheric air in woodlands of natural areas based on the intensity analysis of the process of dry deposition of impurities on an artificial underlying surface

To assess the quality of atmospheric air, the authors propose to apply the process of dry deposition of impurities on an artificial underlying surface that binds impurities in contact with it. The mass of these impurities is calculated upon laboratory exposure, after being transferred to an aqueous solution. The ease of absorber fabrication and the low cost facilitate the monitoring of air pollution at various points in woodlands, where the stationary stations for air-pollution-monitoring are very difficult and costly to arrange. A large number of control points makes it possible to identify forest areas with the highest levels of air pollution. A dynamic air-quality study at one of the monitoring points is necessary and sufficient to determine the concentration of impurities. The authors surveyed an urban forest using the proposed method, and the survey results confirmed that areas with an elevated concentration of airborne nitrogen dioxide exist within the woodland. This can lead to soil eutrophication and changes in forest biodiversity at the species and ecosystem levels.

Abstract P061: De novo design of importin-a-specific NLS sequences for nuclear-targeted therapeutics

Background: Research focused on the application of nuclear localization sequence (NLS)-based therapeutics has been a topic of intense interest to medicine since the core principles governing nuclear transport were awarded the Nobel Prize in 1999. Despite these efforts, efficient nuclear localization has been difficult. A major obstacle is that NLSs have cationic-net charges (abundance of lysines/arginines) required for appropriate interactions with the nuclear transporter importin-a (Impa). Once in the blood stream, cationic charges can cause strong non-specific cellular uptake and are rapidly cleared from the plasma compartment, which prevents sufficient tumor cell uptake and, hence, nuclear localization. Here, describe a de novo computational approach for generating 43 novel NLSs (based on 3 different NLS classes) that contained amino acid substitutions to achieve net-neutral charge states. We also introduce a novel nuclear isolation-quantitative flow cytometric method for determining nuclear localization efficiency. Material and methods An algorithm was created based on complete interaction binding affinity strengths for 20 x 20 pairs of octapeptides consisting of the 20 common amino acids. 9 PDB files were selected as templates and were comprised of viral, RNA processing, and transcription initiation protein NLSs bound to Impa. In silico alanine scanning on all NLS templates generated rankings on amino acid sensitivities for each position in the sequences. Non-sensitive residues were then subjected to residue scanning for generating net-neutral charged NLSs. Computational docking studies generated predictive binding scores relative to wild type NLSs. Favorable NLS candidates were genetically fused to GFP. In contrast to utilizing fluorescence microscopy, which cannot determine nuclear localization efficiency, we created a method to isolate nuclei from transiently transfected CHOK1 cells and quantify nuclear localization by flow cytometry. Results 2-8 net-neutral NLSs with good binding for Imga could be generated for each PDB file. The net-neutral mutants often contained an abundance of glutamic and/or aspartic acid substitutions, and were able to bind to Impa residues to compensate for the replaced amino acids. Transfected GFP-NLS constructs displayed variable fluorescence expression kinetics. Therefore, we created an in-house plasma membrane lysis protocol to isolate intact nuclei. Quantitative evaluations are currently underway by evaluating nuclei fluorescence by flow cytometry at various time points. Thus far, the tested GFP-NLSs are able to localize to the nucleus. Conclusions An important objective of computational protein design is the generation of high affinity peptides as a precursor to the development of therapeutics, and as a tool to aid researchers in understanding governing interaction principles of specific complexes. We have achieved both the development of potential NLS peptides for overcoming the cationic-sequestration barrier, and for understanding novel NLS principles to further advance the NLS-therapeutics field.

Citation Format: Olga Bednova, Alexis Rioux-Chevalier, Dipika Patel, Mathieu Boudreau, Jeffrey Victor Leyton. De novo design of importin-a-specific NLS sequences for nuclear-targeted therapeutics [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2021 Oct 7-10. Philadelphia (PA): AACR; Mol Cancer Ther 2021;20(12 Suppl):Abstract nr P061.

Targeted Molecular Therapeutics for Bladder Cancer-A New Option beyond the Mixed Fortunes of Immune Checkpoint Inhibitors?

The fact that there are now five immune checkpoint inhibitor (ICI) monoclonal antibodies approved since 2016 that target programmed cell death protein 1 or programmed death ligand-1 for the treatment of metastatic and refractory bladder cancer is an outstanding achievement. Although patients can display pronounced responses that extend survival when treated with ICIs, the main benefit of these drugs compared to traditional chemotherapy is that they are better tolerated and result in reduced adverse events (AEs). Unfortunately, response rates to ICI treatment are relatively low and, these drugs are expensive and have a high economic burden. As a result, their clinical efficacy/cost-value relationship is debated. Long sought after targeted molecular therapeutics have now emerged and are boasting impressive response rates in heavily pre-treated, including ICI treated, patients with metastatic bladder cancer. The antibody-drug conjugates (ADCs) enfortumab vedotin (EV) and sacituzumab govitecan (SG) have demonstrated the ability to provide objective response rates (ORRs) of 44% and 31% in patients with bladder tumor cells that express Nectin-4 and Trop-2, respectively. As a result, EV was approved by the U.S. Food and Drug Administration for the treatment of patients with advanced or metastatic bladder cancer who have previously received ICI and platinum-containing chemotherapy. SG has been granted fast track designation. The small molecule Erdafitinib was recently approved for the treatment of patients with advanced or metastatic bladder cancer with genetic alterations in fibroblast growth factor receptors that have previously been treated with a platinum-containing chemotherapy. Erdafitinib achieved an ORR of 40% in patients including a proportion who had previously received ICI therapy. In addition, these targeted drugs are sufficiently tolerated or AEs can be appropriately managed. Hence, the early performance in clinical effectiveness of these targeted drugs are substantially increased relative to ICIs. In this article, the most up to date follow-ups on treatment efficacy and AEs of the ICIs and targeted therapeutics are described. In addition, drug price and cost-effectiveness are described. For best overall value taking into account clinical effectiveness, price and cost-effectiveness, results favor avelumab and atezolizumab for ICIs. Although therapeutically promising, it is too early to determine if the described targeted therapeutics provide the best overall value as cost-effectiveness analyses have yet to be performed and long-term follow-ups are needed. Nonetheless, with the arrival of targeted molecular therapeutics and their increased effectiveness relative to ICIs, creates a potential novel paradigm based on 'targeting' for affecting clinical practice for metastatic bladder cancer treatment.