Dendritic cells (DCs) infiltration in head and neck tumor tissues correlates with survival, recurrence and metastasis of hypopharyngeal cancer patients. The high expression of programmed death ligand-1 (PD-L1) in DCs activate the PD-L1/PD-1 pathway, leading to the decrease of immune function of effector T cells (CD8+ T cells). This study aims to investigate the role and mechanism of the novel molecule Mitogen-activated protein three kinase 19 (MAP3K19) in regulating DCs function and PD-L1 regulation during hypopharyngeal cancer progression.

Materials and Methods: Clinical samples from patients with hypopharyngeal cancer were analyzed. Recombinant adenovirus or siRNA was used to regulate MAP3K19 in DCs from healthy donors. DC function makers (CD83, CD80, CD86), cytokine release (IL-6, TNF-α, IL-1β, IL-12p70), and their capacity to activate CD8+ T cells (CD107a, Ki67, IFN-γ, granzyme B) were assessed via flow cytometry, ELISA, and qRT-PCR. Key signaling molecules, including phosphorylated glycogen synthase kinase 3β (GSK3β) and NF-κB pathway components, were evaluated by Western blot. The in vivo role of MAP3K19 was validated using a xenograft tumor model in nude mice.

Results: MAP3K19 expression was markedly up-regulated in tumor tissue and peripheral blood mononuclear cells of hypopharyngeal cancer patients. In vitro and in vivo, MAP3K19 overexpression in DCs potently suppressed their activation, maturation, and cytokine production. Consequently, these DCs exhibited a diminished ability to stimulate CD8+ T cell cytotoxicity. Mechanistically, MAP3K19 overexpression promoted inhibitory phosphorylation of GSK3β. This led to a dual effect: suppression of NF-κB signaling activation and enhancement of PD-L1 protein stability (without affecting its mRNA level), thereby increasing PD-L1 surface expression. The critical role of GSK3β was confirmed, as the GSK3β inhibitor AR-A014418 largely rescued the suppressive effects of MAP3K19 on both NF-κB activation and PD-L1 expression. In vivo, overexpressing MAP3K19 significantly promoted tumor growth and reduced intratumoral DC activation and CD8+ T cell cytotoxic function.

Conclusion: Our findings demonstrate that MAP3K19 drives hypopharyngeal cancer progression by crippling DC activation, maturation, and function. MAP3K19 orchestrates DC dysfunction by phosphorylating and inactivating GSK3β, which simultaneously suppresses the NF-κB pathway and enhances PD-L1 protein stability. Targeting the MAP3K19/GSK3β axis may represent a novel therapeutic strategy to reverse immunosuppression in hypopharyngeal cancer.