Figure 5. Combination of trametinib with FGFR inhibition effectively leads to cell death in mesenchymal-like KRAS mutant lung cancer.

(A) Mesenchymal-like KRAS mutant NCI-H1792 and LU99 cells were treated with 1uM pan-FGFR inhibitor NVP-BGJ398, 50 nM trametinib, or the combination of these two drugs for 48 hours, and lysates were probed with the indicated antibodies. (B, C) Cell lines were treated with DMSO, 1uM afatinib, 1uM NVP-BGJ398, with or without 50 nM trametinib, and drug was replenished every 72 hours for 6 days. Plates were then stained with crystal violet and imaged. A representative plate of 2 independent experiments are shown. (D, E) NCI-H1792 (D) or LU99 (E) cells were treated with drug and drug combinations as in (A) for 72 hours and analyzed by FACS to quantify annexin positive cells. The average amount of apoptosis ± SD of 3 independent experiments is shown (p < 0.05 by Student’s t test). (F) Epithelial-like KRAS mutant NCI-H358 and NCI-H1573 cells were treated as in (A). Lysates from LU99 were used as positive control for the induction of FRS2 phosphorylation following trametinib treatment. Independent experiments were performed three times, and a representative result is shown. (G) The levels of phosphorylated ERK after treatment with trametinib or trametinib with NVP-BGJ398 were quantified for eleven mesenchymal-like KRAS mutant cancer cell lines examined (raw data shown in (A) and Supplementary Fig. S8A). A paired Student’s t-test was used for comparisons. (H) Induction of apoptosis by trametinib or the combination of trametinib with NVP-BGJ398 in mesenchymal-like KRAS mutant lung cancer cell lines. Raw data is shown in (D), (E), and Supplementary Fig. S8D. A paired Student’s t-test was used for comparisons.