Figure 5. MK-2206 treatment enhanced the susceptibility of Ctx^R cells to cetuximab by inducing apoptosis. (A) MK-2206 treatment enhanced the susceptibility of Ctx^R cells to cetuximab. Ctx^R cells (HC1, HC4, HC8) and parental controls (HP) were treated with DMSO, Ctx (0.1–1000 nM), MK-2206 (0.1–10 uM) or the combination of Ctx 100nM+ MK-2206 (0.1–10 uM), for 72 h. Growth was measured at 72 h after drug treatment using the proliferation assay as described in the experimental procedures and plotted as a percentage of growth relative to the untreated control cells. Data points are represented as mean ± SEM (n = 4). *p ≤ 0.05. (B) MK-2206 plus Cetuximab induced modest apoptosis in Ctx^R clones. Ctx^S parental cell line (HP) or Ctx^R cell lines (HC1, HC4, HC8) were plated and allowed to adhere for 24 h prior to treatment with vehicle (DMSO), cetuximab (100 nM), MK-2206 (5 uM) or the combination (cetuximab+MK-2206) for 24 h prior to Annexin-V analysis via flow cytometry. Annexin-V analysis was described in the materials and methods. Data points are represented as mean ± SEM (n = 3). *p ≤ 0.05. Flow cytometry profile represents Annexin-V-FITC staining in x axis and PI in y axis. The number represents the percentage of cells in each condition.