HPV Oncoproteins Modulate Human β-defensin-3 Expression in Oral Epithelial Cells

Objective: To elucidate mechanisms by which high-risk human papillomavirus (HPV) could evade immune detection and clearing via infected epithelial cells and the role of HPV-induced gene expression in orchestrating local immunity.

Method: Immunofluorescence microscopy was used to determine hBD-3 expression and E6 and E7 oncoproteins in normal and head and neck cancer biopsies. Expression of hBD-3 were determined by quantitative PCR and ELISA in primary oral epithelial cells transfected with each of expression vectors producing HPV-16 E6 and E7 as well as HPV-11 E6. The hBD-3 luciferase promoter constructs with serial promoter deletions were co-introduced with early genes of HPV-16 and HPV-11 for determination of transactivity.

Result: HPV-16 E6 and E7 are causal factors for a subset of oral cancer; while HPV-11 E6 protein may contribute to causing benign warts in the mouth. Cancer cells of HPV-related oral and oropharyngeal squamous cell carcinoma biopsies overproduce hBD-3. HPV-16 E6 or E7 increases the levels of hBD-3 mRNA and peptide in primary oral epithelial cells. However, HPV-11 E6 is significantly less potent in promoting hBD-3 expression. Combination of oncogenic E6 and E7 in oral epithelial cells also shows reduced induction of hBD-3. The transactivity of an hBD-3 luciferase promoter construct is differentially stimulated by oncogenic E6 and E7 compared with MEKK1, a known inducer of hBD-3 expression. Pharmacological inhibitors for MAPK and PI3K reduce the transactivity of a 2.5 kb hBD-3 promoter reporter; but not the reporter containing a 450 bp 3’-regulatory region.

Conclusion: Our previous work has suggested that overexpression of hBD-3 may contribute to oral cancer progression through modulating the immune response in the tumor microenvironment. These data suggest that early genes of high- and low-risk HPV types differentially modulate hBD-3 expression in oral epithelial cells, which may play a role in oral lesions related to HPV infection.