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

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. The impact of TNFAIP2 on tumor metastasis was assessed based on the conditional knockout mouse with 4-nitroquinoline-1-oxide (4NQO) induced OSCC through feature and immunohistochemistry analysis. To explore the specific mechanism and intervention means, enrichment analysis and co-immunoprecipitation were also applied, together with designing the nano-hydroxyapatite (nHAp) based RNA interference delivery system to restrict tumor dissemination. The epithelium conditional knockout Tnfaip2 reduced tumor initiation rate, differentiation degree and cervical lymph node metastasis (LNM) in mouse exposed to 4NQO. Enrichment analysis suggested 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, it was demonstrated that TNFAIP2 completely interacted with kelch-like ECH-associated protein 1 (KEAP1) to avoid IKKβ from ubiquitination at K63 and subsequent proteasomal degradation, 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. Above results showed TNFAIP2 promoted the EMT and lymphangiogenesis of OSCC by regulating NF-κB signaling, a mechanism that was dependent on the interaction with KEAP1 completely. The nHAp based TNFAIP2 interference might serve as novel therapeutics in limiting OSCC metastasis.