Validation of telomerase-upregulated pathways. A, Western blot analysis using protein extracts from thyroid tumors from 20-week-old animals with the indicated genotypes for phospho-NF-κB p65 and vinculin (VCL, loading control). B, Representative images from phospho-Erk (pErk) IHC performed in mouse tumors from 20-week-old animals with the indicated genotypes. C, Quantification of the percentage of tumor cells staining positive for pErk in mice with the indicated genotypes. D, Western blot analysis using protein extracts from thyroid tumors from 20-week-old animals with the indicated genotypes for phospho- and total Erk (MAPK pathway) and Akt (PI3K effector), as well as p85 (loading control; only protein that was reblotted on stripped membranes). “Braf+Tert” and “Braf+K5-Tert” labels denote “BrafV600E+Tert−123C>T” and “BrafV600E+keratin 5-driven Tert” genotypes, respectively.