TNFAIP2 promotes NF-κB signaling mediate lymph node metastasis of oral squamous cell carcinoma by protecting IKKβ from ubiquitin proteasome degradation

BACKGROUND: Tumor dissemination is a life-threatening event which confers to most cancer-related deaths with limited effective therapeutic option. TNFα-induced protein 2 (TNFAIP2) reveals pro-metastasis potential in several cancers. However, its definite role and underlying mechanism in oral squamous cell carcinoma (OSCC) is largely unknown. METHODS: The impact of TNFAIP2 on tumor metastasis was assessed based on the conditional knockout mouse with 4-nitroquinoline-1-oxide (4NQO) induced OSCC model through feature and immunohistochemistry analysis. To explore the specific mechanism, enrichment analysis and co-immunoprecipitation were applied. Meanwhile, the nano-hydroxyapatite (nHAp) and poly-L-lysine (PLL) based RNA interference delivery system was designed to restrict tumor dissemination. RESULTS: The conditional knockout Tnfaip2 in epithelium reduced tumor initiation rate, differentiation degree and cervical lymph node metastasis (LNM) in mouse exposed to 4NQO. Enrichment analysis suggested nuclear factor-kappa B (NF-κB) signaling was associated with these effects. Western blot proved that TNFAIP2 prevented the ubiquitin proteasome degradation of inhibitor of kappa light polypeptide gene enhancer in B-cells, kinase beta (IKKβ), a classical transcriptional activator protein in NF-κB signaling. Mechanistically, TNFAIP2 was demonstrated to competitively interact with kelch-like ECH-associated protein 1 (KEAP1) to avoid IKKβ from ubiquitination at K63 and proteasomal degradation subsequently, which finally sustained NF-κB signaling and facilitated tumor metastasis by enhancing epithelial-mesenchymal transition (EMT) and lymphangiogenesis. Notably, the synthetic small interfering RNA delivery systems nHAp@PLL-siTnfaip2 showed significant effect in attenuating tumor progression of OSCC mouse. CONCLUSION: Above results showed TNFAIP2 promoted EMT and lymphangiogenesis of OSCC by regulating NF-κB signaling, a mechanism that was dependent on the interaction with KEAP1 competitively. The nHAp based TNFAIP2 interference might serve as a novel therapeutic in limiting OSCC metastasis.