KSHV and HPV modulate epithelial-to-mesenchymal transition in oral epithelial cells.

Most oral viral infections that manifest as oral diseases or cancers are caused by oncogenic human papillomavirus and herpesviruses. However, the mechanisms involved in the association between oral cancer and oncogenic virus infection are not well understood. In this study, we used telomerase (hTERT) -immortalized normal oral gingival keratinocytes (NOKs) and generated latent Kaposi's sarcoma-associated herpesvirus (KSHV)- and human papillomavirus 31 (HPV31)-infected NOKs. NOKs either stably maintaining HPV episomes or latently infected with KSHV acquired a fibroblast-like morphology and upregulated cell proliferation in both complete media and serum starvation culture conditions. Moreover, migration and invasion assays revealed that the KSHV- and HPV-infected NOKs show markedly higher migration and invasion activity compared to uninfected cells. We demonstrated that KSHV-NOK and HPV-NOK express much lower protein levels of the epithelial cell marker E-cadherin and significantly higher protein levels of mesenchymal cell marker vimentin, indicating that KSHV and HPV31 infection induces an epithelial-to-mesenchymal transition (EMT). Notably, after efficient vimentin knockdown using two different lentiviral short hairpin RNAs (shRNAs) or eribulin treatment, E-cadherin expression was restored, and phenotypic alterations (proliferation, migration, and invasion) caused by KSHV and HPV31 infection were abolished, suggesting that KSHV- and HPV31-induced EMTs play an important role in these phenotypic alterations by KSHV and HPV31. Given that changes in EMT are often associated with cancer progression, our results offer important insight into the mechanism behind KSHV and HPV infection and cancer, suggesting that EMT is a potential therapeutic target for KSHV- and HPV-driven cancers.IMPORTANCEThe oral cavity is believed to be a primary site where many viruses infect the human body. Kaposi's sarcoma-associated herpesvirus (KSHV) and human papillomavirus (HPV) are both found and cause cancers in the oral cavity. However, knowledge of how KSHV and HPV infection is connected to oral cancer (e.g., oncogenesis and metastasis) remains limited. Here, our study reveals that KSHV and high-risk HPV31 can induce epithelial-to-mesenchymal transition by upregulation of vimentin and downregulation of E-cadherin, which is vital for KSHV-normal oral gingival keratinocyte (NOK) and HPV-NOK to acquire cancer cell characteristics such as cell survival, migration, and invasion activities. For the first time, we show that knockdown of vimentin and eribulin treatment can restore E-cadherin and reverse epithelial-to-mesenchymal transition in KSHV- and HPV31-infected oral epithelial cells. These findings fill a gap in our understanding of oncogenesis and metastasis of oral cancers caused by KSHV and HPV31, revealing that vimentin may serve as a potential therapeutic molecular target for KSHV- and HPV-associated oral cancer.