FGFR4 blockade results in loss of GBM cell adhesion and sensitizes towards the RGD-mimetic cilengitide. A-C,EREACTOME gene sets enriched in BTL1528 GFP versus FGFR4-KD(K504M) gene expression data based on GSEA. NES = normalized enrichment score, padj = adjusted p-value. D Adhesion capacities of BTL1528 FGFR4-KD(K504M) and respective GFP cells towards collagen as percentage of cell-coated well surfaces (means ± SEM of three experiments (left). Exemplary photomicrographs are shown. Outspread cells after 60 min were counted microscopically and data normalized to GFP control cells (right).F Integrin-mediated cell adhesion arrays of FGFR4-KD(K504M)- and GFP-transduced BTL1528 subclones are shown (means of two experiments). (G + H) Viability of BTL1528 FGFR4-KD(K504M)- and GFP-expressing GBM cells in response to single-agent cilengitide (G), combined-agent cilengitide + ponatinib (pon.) (H left) and cilengitide + BLU554 (H middle) was evaluated by MTT assays. For each panel, one representative out of three experiments is shown as mean ± SD from triplicates. Combination indices (CI) are given for selected drug concentrations combining cilengitide with ponatinib (blue) or BLU554 (black) (H right). CI values < 0.9 were considered synergistic [22]. Statistical analyses: 2-way ANOVA/Bonferroni correction (D left, F–H), Student’s t-tests (D right). *p < 0.05, **p < 0.01, ***p < 0.001, n.s. = not significant, n.d. = not detected
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