USP7-stabilized CEBPB promotes HpSCC progression by upregulating IL6 to activate the JAK2/STAT3 signaling

CCAAT/enhancer-binding protein B (CEBPB) has been reported as a transcription factor implicated in the occurrence and development of various human tumors. However, its role and mechanism in hypopharyngeal squamous cell carcinoma (HpSCC) remain unclear.

qRT-PCR, western blot, and immunohistochemistry assays were used for mRNA or protein expression in HpSCC tissus or cells. HpSCC cell phenotypes were evaluated using colony formation, EdU, wound healing, and transwell assays. The role of CEBPB in HpSCC tumorigenesis was also investigated by establishing xenograft model in mice. Interaction between CEBPB and ubiquitin-specific peptidase 7 (USP7) was confirmed using co-immunoprecipitation (Co-IP), cycloheximide (CHX) chase, and deubiquitination assays. Chromatin immunoprecipitation (ChIP) and luciferase reporter assays were employed to determine the transcription regulation of CEBPB on IL-6.

Higher CEBPB expression was found in HpSCC tissues and represented a worse prognosis. Knockdown of CEBPB inhibited HpSCC cell proliferation, migration, invasion, and EMT, while overexpression of CEBPB displayed the opposite trend. USP7 stabilized CEBPB protein by its deubiquitination activity. CEBPB binds to the promoter of IL-6 to increase its transcription, thus activating the JAK2/STAT3 signaling pathway. Furthermore, USP7 could promote IL-6 expression through CEBPB. Functionally, restoration of CEBPB expression reversed the anti-cancer effect of USP7 depletion in HpSCC. Moreover, the inhibitory effect of HpSCC progression mediated by CEBPB knockdown was abated upon IL-6 upregulation.

Our finding reveals a novel USP7/CEBPB/IL-6/JAK2/STAT3 axis in regulating HpSCC progression, targeting this pathway might be a valuable strategy for HpSCC therapy.