Fig. 2: Intrinsic AKT activation induces FGFR1 inhibition resistance in lung-cancer cells.

a Western blot analysis comparing main signaling pathways between control (HCC15), resistant (NCI-H520 and NCI-H1703) and sensitive (DMS114, H1581 and LK2) lung-cancer cell lines after FGFR1 inhibition with AZD4547. b Cell viability assay comparing sensitivity profiles of the six lung-cancer cell lines indicated to FGFR1 inhibition with DMSO treatment as standard. c, d Knockdown of FGFR1 with small interfering RNA (siRNA, SI02224684) in different lung-cancer cell lines validated by western blot analysis after 48 h (c) and proliferation of cells was compared on day 6 (d). e, f Cell viability assay showing the effect of combining the AKT inhibitor AZD5363 with the FGFR1 inhibitor AZD4547 at different concentrations after 96 h incubation in NCI-H520 (e) and NCI-H1703 (f) SQCLC cell lines. g Combination index plot showing the synergetic effect of combining AZD4547 with AZD5363 in NCI-H520 and NCI-H1703 cell lines calculated using CompuSyn software based on the Chou–Talalay drug interaction algorithm: CI < 1, synergetic effect; CI = 1, additive effect; CI > 1, antagonistic effect. h Immunohistochemical staining of SQCLC patient tissue samples with negative, weak and strong phosphorylated AKT signals. i, j H-score quantification of pAKT signals in the SQCLC patients with FGFR1 amplification (i) and in the SQCLC patients with FGFR1 overexpression (j). Statistical analysis was performed with the chi-squared test: ns (p > 0.05), *(p < 0.05), **(p ≤ 0.01) and ***(p ≤ 0.001). Mean values are plotted; error bars represent standard deviation.