Transcriptional suppression of E-cadherin by HPV-16 E6 and E7 oncogenes is independent of hypermethylation of E-cadherin promoter

الملخص EN

Background: Cervical cancer is one of the most common cancers observed in women worldwide, and its development is related to E6 and E7 two viral oncoproteins of high-risk human papillomavirus (HPV) types.

Aberrant expression of E-cadherin, which is associated with epithelial-to-mesenchymal transition (EMT), is frequently observed in cervical cancer.

Objectives: The mechanisms underlying E-cadherin suppression in cervical cancer are not clear; therefore, this experimental study from Iran was designed to elucidate the relationship of DNA methyltransferase expression and E-cadherin promoter methylation with E-cadherin expression in HPV-16 E6- and E7-expressing cells.

Materials and Methods: Real-time PCR and western blot were used to determine the effects of HPV-16 E6 and E7 on E-cadherin, DNMT1, DNMT3a, and DNMT3b expression in HCT-116 cell line.We also analyzed E-cadherin promoter methylation in cells expressing HPV-16 E6 and E7 oncoproteins by bisulfite sequencing.

Results: HPV-16 E6 and E7 proteins reduced E-cadherin expression 3.7 and 2.2 timeswhencompared with control cells (P = 0.0221 and P = 0.0461, respectively).

This reduction was greater in HPV-16 E6-expressing cells than in HPV-16 E7-expressing cells.

Although HPV-16 E6 and E7 increased DNA methyltransferase 1 expression 2.6 and 3.4 times, respectively (P = 0.0133 and P = 0.0113) when compared with control cells, they was no E-cadherin promoter methylation.

Conclusions: Unlike other cancer-associated viruses (HBV, HCV, and EBV), reduction in E-cadherin expression in HPV-16 E6- and E7- expressing cells is not due to hypermethylation of the E-cadherin promoter.