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.
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