ELF3 Overexpression Contributes to the Malignant Transformation of HPV16 E6/ E7-Immortalized Keratinocytes by Promoting CCNE2 Expression.

Current cancer burden caused by persistent infection with human papillomaviruse genotype 16 (HPV16) cannot be ignored. The related mechanisms of oncoproteins E6 and E7 from HPV16 on keratinocyte malignant transformation need to be further elucidated. GSE3292 dataset analysis revealed the upregulation of ETS transcription factor 3 (ELF3) and cyclin E2 (CCNE2). To verify whether there is an interaction between ELF3 and CCNE2, E74 like ELF3 and CCNE2 expression profiles as well as their putative binding sites were analyzed using bioinformatics. Retroviruses encoding HPV16 E6 and E7 genes were used to induce immortalization of human foreskin keratinocytes (HFKs) in vitro. Dual luciferase reporters assay was used to verify the binding of ELF3 and CCNE2. The effect of ELF3 on the immortalized cells was investigated using CCK-8 assay, cell cycle analysis and western blot. ELF3 and CCNE2 presented overexpression patterns in head and neck squamous cell carcinoma. HPV16 E6/E7-expressing HFKs showed enhanced viability, accelerated cell cycle as well as upregulated ELF3 and CCNE2. ELF3 overexpression enhanced the activity of CCNE2 promoter. ELF3 silencing reduced viability, induced cell cycle arrest and suppressed expressions of CCNE2, E6 and E7 in HPV16 E6/E7-expressing HFKs. Downregulation of ELF3 played an inhibiting role in the malignant transformation of HPV16 E6/E7-immortalized HFKs by decreasing CCNE2 expression.