A, prevalence of RB1 mutations in human ATC. B, Western blot analysis of RB expression in human ATC cell lines. Nthy-ori (non-tumor, immortalized) and FTC133 (follicular thyroid carcinoma) are shown as controls. C, effect of 1 hour treatment with 100nM Palbociclib on RB phosphorylation in two representative ATC cell lines. D,E dose/response analysis of palbociclib effect on the proliferation of human (D) and mouse (E) ATC cell lines.