Fig. 3

Titration of VS-4718 and carf in two MM cell lines. To find an effective and low toxic combination of carf and VS-4718, these drugs were titrated in (A) the cell line L-363 in different combinations of VS-4718 (1.5-3 µM) with carf (1–4 nM) starting with low doses of VS-4718 and high doses of carf, followed by high doses of VS-4718 with low doses of carf. 3 µM VS-4718 with 3 nM carf was determined as optimum in this test series. (B) 3 µM VS-4718 was then taken for the titration with different doses of carf (0.5-2 nM) in MM.1 S, taking previously reported carf concentrations as reference (Brünnert, Kraus et al. 2019). (C) 3 µM VS-4718 and 3 nM carf were tested in primary PBMCs. (A–C) Survival was determined by Annexin V-647/PI staining and subsequent measurements with a BD FACS Canto II from BD Biosciences. Bars represent the mean ± SD of three independent experiments. P-values were determined in an ordinary one-way ANOVA using Tukey’s multiple comparison test and only depicted for p < 0.05. The depiction of statistical comparisons was furthermore limited to DMSO vs. VS-4718 and single drugs (VS-4718 and carf) vs. drug combinations to focus on the most relevant results.