Nucera, Nehs, Nagarkatti et al. 299 Figure 1. p-ERK-1/ERK-2 expression in thyroid cancer cells. (A): B-RafV600E mutation in 8505c cells; TPC-1 cells have wt B-Raf and harbor the PIK3CA H1047R mutation and RET/PTC-1 translocation. (B): One hour of 1 M PLX4720 treatment re- sulted in lower p-ERK-1/ERK-2 levels (by Western blotting) in 8505c cells, but higher levels in TPC-1 cells. p-ERK-1/ERK-2 levels were lower in 8505c cells and TPC-1 cells with 10 M PLX4720. (C): 72 hours of PLX4720 treatment resulted in lower p-ERK-1/ERK-2 levels in 8505c cells and higher levels in TPC-1 cells. Abbreviations: DMSO, dimethyl sulfoxide; ERK, extracellular signal–related kinase; p, phosphorylated; wt, wild-type. PLX4720, respectively; p .001), reduced the S-phase cell fraction (Fig. 2A, 2B), and caused G1 arrest (38.9% 1.8% versus 56.4% 1.9% in control versus PLX4720, respectively; p .001) (Fig. 2D). PLX4720 treatment (1 M or 10 M) did not lead to apoptosis (ab- sence of sub-G1 cell population) according to the flow cytometric analysis (Fig. 2D). Recently, it was demonstrated that PLX4720 induces activation of C-Raf [25]. We analyzed C-Raf protein lev- els and did not find a significant difference after 1 hour www.TheOncologist.com