Downregulation of VAP-1 in OSCC suppresses tumor growth and metastasis via NF-κB/IL-8 signaling and reduces neutrophil infiltration

Background: Vascular adhesion protein-1 (VAP-1) is believed to play a role in inflammation. Studies have suggested that VAP-1-mediated activation of inflammation is dependent on NF-κB, leading to secretion of the interleukin (IL)-8; however, no reports have addressed the association between VAP-1 and NF-κB/IL-8 signaling in oral squamous cell carcinoma (OSCC). This study aimed to investigate the role of VAP-1 in OSCC and further explore whether VAP-1 is involved in the regulation of neutrophil infiltration in the tumor microenvironment (TME).

Methods: Immunochemistry staining was used to observe VAP-1 expression. CCK-8 and Transwell assays were used to measure cell proliferation, migration, and invasion. OSCC xenograft mouse models were used for in vivo verification of the VAP-1 function. The expression of NF-κB and IL-8 were determined by qRT-PCR and western blot. ELISA for IL-8 was also conducted. The relationship between VAP-1 expression and neutrophil infiltration was analyzed by immunofluorescence.

Results: VAP-1 was overexpressed in human OSCC tissues. Downregulation of VAP-1 suppressed OSCC cells proliferation, migration, and invasion in vitro and inhibited tumor proliferation and metastasis in vivo. Additionally, downregulation of VAP-1 inhibited NF-κB/IL-8 signaling in vitro and in vivo. VAP-1 expression was positively correlated with neutrophil infiltration in human OSCC tissues. Moreover, blocking VAP-1 decreased neutrophil infiltration by reducing IL-8 production.

Conclusions: VAP-1 downregulation in OSCC suppresses tumor growth and metastasis by inhibiting NF-κB/IL-8 signaling and reducing neutrophil infiltration in the TME, suggesting that VAP-1 may be a potential therapeutic target for OSCC.