Fig. 3

Dual treatment with trametinib and a phosphatidylinositol‐4,5‐bisphosphate 3‐kinase (PI3K) inhibitor has a synergistic effect in vitro. (A) Four‐day proliferation assay testing the efficacy of trametinib (20nm) and of BYL719 (2μm; the isoform‐specific inhibitor of PI3K), or GDC‐0941 (1μm; the inhibitor of α and δ PI3K), alone or in combination, in CAL33 and HSC3 head and neck squamous cell carcinoma (HNSCC) cell lines. Error bars indicate SD. Data represent a representative experiment from three independent experiments. (B) Western blot for the indicated proteins following 24h of 20nm trametinib treatment with or without BYL719 (2μm) or GDC‐0941 (1μm) in CAL33 and HSC3 HNSCC cell lines. Continued use of tumor cell lysates from Fig. 1B. Numbers indicate the fold change in protein level normalized to Actin. Data represent a representative experiment from three independent experiments. (C) Synergy scores and heatmap calculated by SynergyFinder for the combination of trametinib with BYL719 or GDC‐0941 in CAL33 and HSC3 HNSCC cell lines. Data represent a representative experiment from three independent experiments. Statistical significance was calculated using one‐way ANOVA (*P<0.05, **P<0.01, ***P<0.001, ****P<0.0001).