E2F1 and breast neoplasm: As in our previous studies in breast tumors (26) and pleural mesotheliomas (27), we observed the lack of CDK4 T172-phosphorylation in some thyroid tumors to be associated with high expressions of CDKN2A (p16), CCNE1 (cyclin E1) and E2F1. Transcript levels of CDKN2A, E2F1 and CCNE1 were indeed elevated in ATC and PDTC samples with profile A of CDK4 (Figures 1D-F).