Oral squamous cell carcinoma (OSCC) and hypopharyngeal squamous cell carcinoma (HSCC) are representative of head and neck squamous cell carcinoma (HNSCC) and the molecular pathogenesis has not been completely clarified. Ubiquitin-conjugating enzyme E2 L3 (UBE2L3) is the key member of the E2 family that encodes 153 amino acid residues. Previous studies demonstrate that UBE2L3 is aberrantly overexpressed in various types of human cancers, suggesting that UBE2L3 may function as an oncogene. However, its functional role and the potential mechanisms in the OSCC and HSCC remain unclear. In the present study, we found that UBE2L3 was significantly upregulated in clinical HNSCC samples and HNSCC cell lines, and patients with lower UBE2L3 expression have a higher survival rate. Two HNSCC cell lines FaDu (HSCC cells) and CAL-27 (OSCC cells) with moderate expression of UBE2L3 were selected for in vitro experiments. We proved that UBE2L3 overexpression was positively associated with cellular malignant phenotypes in vitro, including proliferation, invasion, migration, and tumor growth in vivo. Conversely, UBE2L3 suppression diametrically yielded opposing results. Our further study demonstrated that overexpression of UBE2L3 significantly activated the nuclear factor kappa B (NF-κB) signaling pathway through promoting NF-κB p65 nuclear translocation and the ubiquitination and degradation of IκBα protein. Additionally, UBE2L3 was proved to be targeted and negatively regulated by miR-378a-5p, and UBE2L3 overexpression reversed the effects of miR-378a-5p upregulation. Collectively, the present study indicates that UBE2L3 may promote OSCC and HSCC progression via activating the NF-κB signaling by increasing IκBα degradation, indicating that UBE2L3 may be a potential therapeutic target for the treatment of HNSCC.
Keywords: NF-κB; OSCC; UBE2L3; miR-378a-5p; ubiquitination.
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