ALDH3A1 upregulation inhibits neutrophils N2 polarization and halts oral cancer growth.

Objectives: Tumor-associated neutrophils (TANs) are among the most abundant inflammatory cells in tumor microenvironment (TME). Aldehyde dehydrogenase 3A1 (ALDH3A1) is significantly reduced in oral squamous cell carcinoma (OSCC), ALDH3A1 overexpression suppresses tumorigenesis by inhibiting inflammation. This study investigated the relationship and mechanisms underlying the crosstalk between ALDH3A1 and TANs in OSCC.

Materials and methods: Immunohistochemistry and immunofluorescence were performed to investigate the abundance of TANs and the expression of ALDH3A1. dHL-60 were induced with tumor-conditioned media and recombinant IL-6/IL-8. The expression of key proteins in PI3K/AKT/NF-κB pathway were detected by RT-PCR and western blot. A xenograft model was utilized to examine the effect of ALDH3A1 on tumorigenicity and polarization of TANs.

Results: In patients with OSCC, TANs significantly increased and were associated with a worse prognosis. Additionally, ALDH3A1 negatively correlated with TANs infiltration and especially the N2 phenotype which was the prominent part in OSCC. Furthermore, our study demonstrated that tumor-derived IL-8 drives ALDH3A1-mediated TANs N2 polarization in the TME through PI3K/AKT/NF-κB pathway in vitro and in vivo.

Conclusion: Our results indicate that TANs can serve as a prognostic biomarker and ALDH3A1 could be a promising therapeutic target for regulating TANs N2 polarization in antitumor therapy.