E2F1 and head and neck squamous cell carcinoma: Additionally, the results from qRT-PCR indicated that all E2Fs were overexpressed in HNSCC cell lines (Fig. 2 C-H), except for there was no difference in E2F1 and E2F2 expression between SCC15 and HOK cells (P > 0.05) (Fig. 2A-B).