300 PLX4720 and Preclinical Thyroid Cancer Models Figure 2. PLX4720 inhibits proliferation in thyroid cancer cells. (A–C): 1 M PLX4720 reduced BrdU incorporation in TPC-1 cells (*p .01); 10 M PLX4720 reduced BrdU uptake in 8505c and TPC-1 cells (***p .001). (D): 1 M PLX4720 signifi- cantly reduced S-phase (*p .01) and caused G1 phase arrest (**p .01) in TPC-1 cells and 10 M PLX4720 reduced S-phase (***p .001) and caused G1 phase arrest (**p .001) in both TPC-1 and 8505c cells. Abbreviations: BrdU, bromodeoxyuridine; DMSO, dimethyl sulfoxide; wt, wild-type. with PLX4720 treatment compared with controls (sup- plemental online Fig. 1A). Additionally, the Raf–ERK pathway can synergize with phosphoinositide 3-kinase (PI3K)/Akt–mediated signaling on specific biochemical effectors [26] and we wanted to see whether phospho- ERK-1/ERK-2 downregulation by PLX4720 could affect downstream targets such as Akt phosphorylation levels. We found no significant difference in phospho-Akt ser473 protein levels in 8505c cells after 1 hour with PLX4720 treatment, compared with the control (supple- mental online Fig. 1A). We have previously shown an important role for B-RafV600E in mediating migration and invasion of 8505c into Matrigel [19]. One micromolar PLX4720 reduced mi- gration from 71.3 1.5 cells/field to 35 1 migrated cells/ field, and 10 M PLX4720 further reduced migration to