Attenuated TRAF3 fosters activation of alternative NF-kB and reduced expression of antiviral interferon, TP53, and RB to promote HPV-positive head and neck cancers

Abstract

Human papilloma viruses (HPV) are linked to an epidemic increase in oropharyngeal head and neck squamous cell carcinomas (HNSCC), which display viral inactivation of tumor suppressors TP53 and RB1 and rapid regional spread. However, the role of genomic alterations in enabling the modulation of pathways that promote the aggressive phenotype of these cancers is unclear. Recently, a subset of HPVþ HNSCC has been shown to harbor novel genetic defects or decreased expression of TNF receptor–associated factor 3 (TRAF3). TRAF3 has been implicated as a negative regulator of alternative NF-kB pathway activation and activator of antiviral type I IFN response to other DNA viruses. How TRAF3 alterations affect pathogenesis of HPVþ HNSCC has not been extensively investigated. Here, we report that TRAF3-deficient HPVþ tumors and cell lines exhibit increased expression of alternative NF-kB pathway components and transcription factors NF-kB2/RELB. Overexpression of TRAF3 in HPVþ cell lines with decreased endogenous TRAF3 inhibited NF-kB2/RELB expression, nuclear localization, and NF-kB reporter activity, while increasing the expression of IFNA1 mRNA and protein and sensitizing cells to its growth inhibition. Overexpression of TRAF3 also enhanced TP53 and RB tumor suppressor proteins and decreased HPV E6 oncoprotein in HPVþ cells. Correspondingly, TRAF3 inhibited cell growth, colony formation, migration, and resistance to TNFa and cisplatin-induced cell death. Conversely, TRAF3 knockout enhanced colony formation and proliferation of an HPVþ HNSCC line expressing higher TRAF3 levels. Together, these findings support a functional role of TRAF3 as a tumor suppressor modulating established cancer hallmarks in HPVþ HNSCC. Significance: These findings report the functional role of TRAF3 as a tumor suppressor that modulates the malignant phenotype of HPVþ head and neck cancers.