Human papillomavirus 16 oncoprotein regulates the translocation of β‐catenin via the activation of epidermal growth factor receptor

Abstract

BACKGROUND:To understand the mechanism of frequent and early lymph node metastasis in high-risk human papillomavirus (HPV)-associated oropharyngeal squamous cell carcinoma (OPSCC), this study investigated whether b-catenin is regulated by the HPV oncoprotein and contributes to OPSCC metastasis. METHODS: Expression levels of p16, b-catenin, and epidermal growth factor receptor (EGFR) were examined in OPSCC samples (n 5 208) by immunohistochemistry. The expression and subcellular localization of b-catenin and EGFR activation were also studied in HPV-positive and HPV-negative head and neck squamous cell carcinoma cell lines with western blot analysis. HPV16 E6 small interfering RNA was used to elucidate the effect of the HPV oncoprotein on bcatenin translocation. The involvement of EGFR in b-catenin translocation was confirmed by treatment with erlotinib. Moreover, the invasive capacity was evaluated after HPV16 E6/E7 repression. RESULTS: The results showed that the membrane weighted index of b-catenin was inversely correlated with p16 positivity (P <.001) and lymph node metastasis (P 5.026), whereas nuclear staining of bcatenin was associated with p16-positive OPSCC (P <.001). A low level of membrane b-catenin expression was significantly associated with disease-free and overall survival (P <.0001 in both cases). Furthermore, the membrane weighted index of EGFR was inversely correlated with p16 positivity (P <.001) and positively correlated with membrane b-catenin (P <.001). The in vitro study showed that HPV16 E6 repression led to reductions of phospho-EGFR and nuclear b-catenin, which were also observed after erlotinib treatment, and inhibition of invasion. CONCLUSIONS: The findings suggest that HPV16 E6 mediates the translocation of b-catenin to the nucleus, which may be regulated by activated EGFR. Cancer 2015;121:214-25.

Human papillomavirus oncoprotein E6 upregulates c-Met through p53 downregulation

“…In the present study, we found that inhibition of c-Met expression by siRNA and a c-Met tyrosine kinase inhibitor, SU11274, remarkably decreased cell proliferation, migration, and colony formation of CaSki, UM-SCC47, and 93-VU-147T cancer cells, indicating an important role of c-Met in maintaining the aggressive phenotypes of HPV-positive cancer cells. These findings are similar to those of previous studies including our recent paper showing that HPV E6 knockdown results in decrease/elimination of oncogenic behaviors, such as cell proliferation and invasion of HPV-positive cancer cells (28, 41). …”

“…Formalin-fixed, paraffin-embedded tissue sections were used for IHC staining according to the ABC method as described previously (28). In brief, the sections were incubated with a primary antibody of anti-c-Met (1:100 dilution; Cell Signaling) or anti-p53 (1:100 dilution; DAKO), followed by secondary antibody and diaminobenzidine (DAB, Vector Laboratories, Burlingame, CA) staining.…”

“…When co-expressed, E6 and E7 can synergistically immortalize and transform various human primary cells (8). Recently we have shown that HPV E6 oncoprotein can upregulate EGFR to increase nuclear localization of β-catenin, which plays an important role in cell proliferation, migration, and invasion of HPV-associated HNSCC (9). On the other hand, little is known about whether HPV oncoproteins regulate other tyrosine kinase receptors that are frequently overexpressed in HNSCC.…”

Effect of selective small molecule inhibitors on MMP-9 and VEGFR-1 expression in p16-positive and -negative squamous cell carcinoma

“…Therefore, a potential explanation for the intransigence or increase in MMP-9 expression is the counter regulation of the drug-induced decrease in MMP-9 through the activation of viral oncoproteins. Hu et al (59) demonstrated that activation of β-catenin, a functional protein coordinating cell-cell adhesion and promoting the expression of ECM components, including fibronectin, may be induced by viral oncoproteins. It was hypothesized that other metastasis-associated proteins may be facilitated by p16-induced oncoproteins, which is consistent with the results of the present study of increased MMP-9 expression by nilotinib, dasatinib, erlotinib and gefitinib as it is not affected by this type of selective tyrosine kinase inhibition.…”

β-Catenin Expression in Oropharyngeal Squamous Cell Carcinomas: Comparison and Correlation with p16 and Human Papillomavirus in situ Hybridization

“…The E6 oncoprotein from HPV-16 is involved in the induction of nuclear β-catenin localization [6,7]. It has been suggested that HPV-16 E6 mediates the translocation of β-catenin, an action that may be regulated by activated epidermal growth factor receptor [8]. Currently, standard practice involves the determination of the HPV status in the pathologic evaluation of OSCC as it has prognostic and therapeutic implications [9].…”