Human papillomavirus 16 E5 up-regulates the expression of vascular endothelial growth factor through the activation of epidermal growth factor receptor, MEK/ ERK1,2 and PI3K/Akt

Abstract.

The E5 oncoprotein of human papillomavirus (HPV) 16 plays an important role in early cervical carcinogenesis. Vascular endothelial growth factor (VEGF) plays a central role in switching on the angiogenic phenotype during early cervical carcinogenesis. However, the relationship between E5 and VEGF has not previously been examined. To clarify the regulatory role of E5 in VEGF expression, we transferred the E5 gene into various cell types. E5 increased VEGF expression. The addition of epidermal growth factor receptor (EGFR) inhibitor significantly suppressed VEGF expression, demonstrating that E5 stimulates VEGF expression through the activation of EGFR. E5-mediated EGFR activation was accompanied by phosphorylation of Akt and ERK1/2, which are also involved in VEGF expression. Furthermore, the mRNA stability of VEGF was not affected by E5, but VEGF promoter activity could be modulated by inhibitors of the EGFR, MEK-ERK1/2 and PI3K/Akt pathways in E5-expressing cells. Collectively, these novel results suggest that HPV 16 E5 increases VEGF expression by activating EGFR, MEK/ERK1/2 and PI3K/Akt.