Attenuated TRAF3 fosters alternative activation of NF-{kappa}B and reduced expression of anti-viral interferon, TP53, and RB to promote HPV-positive head and neck cancers

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 modulation of pathways that promote the aggressive phenotype of these cancers is unclear. Recently, a subset of HPV+ 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-κB pathway activation, and activator of anti-viral type-I interferon (IFN) response to other DNA viruses. How TRAF3 alterations affect pathogenesis of HPV+ HNSCC has not been extensively investigated. Here, we report that TRAF3-deficient HPV+ tumors and cell lines exhibit increased expression of alternative NF-κB pathway components and transcription factors NF-κB2/RELB. Overexpression of TRAF3 in HPV+ cell lines with decreased endogenous TRAF3 inhibited NF-κB2/RELB expression, nuclear localization, and NF-κB 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 HPV+ cells. Correspondingly, TRAF3 inhibited cell growth, colony formation, migration, and resistance to TNF-α and cisplatin-induced cell death. Conversely, TRAF3 knockout enhanced colony formation and proliferation of an HPV+ HNSCC line expressing higher TRAF3 levels. Together, these findings support a functional role of TRAF3 as a tumor suppressor modulating established cancer hallmarks in HPV+ HNSCC.

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