Aviscumine, a recombinant ribosomal inhibitor, increases the antitumor activity of natural killer cells

Abstract

Abstract. Aviscumine, a recombinant lectin I, has been identified as an immunomodulatory agent within a new class of ribotoxic stress-inducing anticancer substances that have demonstrated efficacy in phase I/II trials. The aim of the present study was to elucidate the presumed effect of aviscumine on enhancing human natural killer (NK) cell antitumor cytotoxicity. To measure the effect of aviscumine on human NK cell cytotoxicity, chromium-51-release assays against K-562 cells were performed with isolated NK cells from the whole blood of 34 healthy volunteers. Two effector-to-target cell ratios (12.5:1 and 25:1) were used by two independent investigators with a focus on the concentration-dependent effect (0.5 vs. 1 ng/ml aviscumine), reproducibility (first vs. second investigator) and the specificity of the effect by comparison to a heat-inactivated aliquot and interleukin 2 (IL-2) stimulation (10 ng/ml). The mediation of the effect via degranulation was demonstrated by flow cytometric analyses of CD107α expression. Statistics were performed with SPSS using Student's t-tests for normally distributed data. Aviscumine induced a significant and reproducible, concentration-dependent increase in NK cell cytotoxicity (n=22; P<0.01 for both concentrations and ratios), which was also demonstrated when administered in combination with IL-2 (n=12; 12.5:1 ratio, P<0.001; 25:1 ratio, P=0.025) and when compared with the heat-inactivated aliquots (n=12; 12.5:1, P= 0.004; 25:1 ratio, P= 0.007). The mediation of its effect via interferon γ degranulation was demonstrated by significantly enhanced CD107α expression (n=7; P=0.005). Taken together, the results indicate that aviscumine induced an increase in NK cell anticancer cytotoxicity. These results highlight its clinical potential as an immunostimulatory agent, particularly with regard to combined use with chemotherapeutics or immune checkpoint inhibitors. However, further studies are required.

Robot Cookies – Plant Cell Packs as an Automated High-Throughput Screening Platform Based on Transient Expression

“…The transient expression of proteins in plants infiltrated with Agrobacterium tumefaciens can tackle these issues because the production of plant biomass is cost-efficient and scalable, and the plants act as self-contained bioreactors (Buyel and Fischer, 2012;Buyel, 2018). Furthermore, plants do not support the growth of human pathogens, they can be engineered to carry out authentic post-translational modifications (Jansing et al, 2019), and they can accumulate proteins such as toxins that kill mammalian cells (Gamerith et al, 2017;Gengenbach et al, 2019). Transient expression in plants is also rapid, with even large-scale experiments requiring only weeks from gene to product (Garabagi et al, 2012;Shoji et al, 2012;Sainsbury and Lomonossoff, 2014).…”

A high-throughput assay for screening natural products that boost NK cell-mediated killing of cancer cells

“…We next investigated the underlying mechanism of DI3A and I3A in induction of NK cell cytotoxicity. Since NK cells destroy target cells mainly through degranulation of cytolytic granules and IFN-c production, we evaluated the expression of CD107a (a marker of degranulation) (Zhao et al 2015;Gamerith et al 2017) and the production of IFN-c by NK cells after DI3A and I3A treatment (Figure 8). The results showed that the CD107a expression and intracellular IFN-c production were enhanced in Figure 5.…”

“…However, the chromium release assay has many limitations, such as, hazardous radioactivity, high cost, short half-life, increased staff requirements for radiation safety training and licencing, and disposal of radioactive waste. Other established methods to assess NK cell cytotoxicity, such as CD107a degranulation assay (Gamerith et al 2017;Zhang et al 2017), ELISA detecting interferon (IFN)-c secreted from NK cells (Gong et al 2017), and intracellular staining of IFN-c produced in NK cells, are also not available for high-throughput screening due to their requirements of complex and time-consuming operations.…”