Figure 2. Persistent ERK activation is associated with acquired resistance to MEK inhibitor in OV.

(A) A2780-P, A2780-R, OVCAR5-P, and OVCAR5-R cells were treated with the indicated concentrations of trametinib. The number of viable cells was measured at 96 hours. Data represent the mean of 3 biological replicates. IC₅₀ was calculated using GraphPad Prism software. (B) Colony formation assay of parental and resistant A2780 and OVCAR5 cells treated with vehicle or trametinib (100 or 500 nM). Images are representative of 3 independent experiments. (C) Quantification of the apoptotic cells among A2780-P/R and OVCAR5-P/R cells treated with vehicle or trametinib for 72 hours, analyzed by flow cytometry. Results are represented as mean ± SD of 3 independent experiments. **P < 0.01, ***P < 0.001 by unpaired Student’s t test. (D and E) Immunoblot analysis of MEK/ERK signaling in A2780 (D) and OVCAR5 (E) cells with their counterpart resistant lines treated with increasing concentrations of trametinib for 48 hours. (F and G) Immunoblot analysis of MEK/ERK signaling in A2780 (F) and OVCAR5 (G) cells with their counterpart resistant lines treated with 50 nM (A2780) or 100 nM (OVCAR5) trametinib at indicated time points.