Abstract
BACKGROUND: The tumor microenvironment in lung adenocarcinoma (LUAD) exhibits complex cellular interactions that drive disease progression. While mast cells (MCs) are known to infiltrate tumors, their specific immunomodulatory functions remain incompletely characterized. METHODS: We conducted a retrospective analysis of hematological parameters, including plasma factors such as interleukin-17 (IL-17). Multiplex immunohistochemical (mIHC) staining was performed on LUAD tissue to investigate the spatial distance and distribution of MCs and Th17 cells. It was integrated with single-cell RNA sequencing for spatial characterization of the tumor microenvironment (TME). Functional validation was performed through in vitro co-culture systems assessing MC-activation, Th17 cell polarization, and tumor cell behavior. Mechanistic insights were confirmed in an orthotopic lung cancer mouse model using pharmacological interventions. RESULTS: Retrospective analysis of hematological parameters revealed significantly elevated serum IL-17 levels in LUAD patients with malignant pleural effusion (MPE). mIHC analysis of clinical specimens demonstrated a significant positive correlation between MC infiltration and Th17 cell abundance in LUAD tissues. Quantitative spatial distance analysis indicated that MCs and Th17 cells were in significantly closer proximity in LUAD tissues than in normal lung. Spatial distribution analysis further revealed that both MCs and Th17 cells were preferentially enriched in peritumoral regions, exhibiting a distinct distance-dependent co-localization pattern from the tumor margin. The accumulation of both MCs and Th17 cells was strongly linked to disease progression and predicted poor clinical outcome in LUAD patients. Single-cell transcriptomics identified enhanced cellular interactions between MCs and Th17 cells, predominantly mediated by Macrophage migration inhibitory factor (MIF) signaling pathways. Mechanistically, tumor-derived soluble factors stimulated MCs to secrete multiple factors, among which MIF functioned as the principal mediator to drive Th17 cell polarization-an effect effectively blocked by the MIF antagonist ISO-1 or the MC stabilizer cromolyn sodium (CS). The resulting Th17-derived IL-17A directly enhanced tumor cell malignant properties including proliferation, migration and invasion. Consistent with these findings, in vivo targeting of the MC-MIF axis significantly suppressed Th17 polarization and impeded tumor progression in orthotopic lung cancer mouse models. CONCLUSION: Our findings establish that MCs promote LUAD progression mainly through MIF-mediated polarization of Th17 cells, revealing the MC-MIF-Th17 axis as a promising therapeutic target for LUAD treatment.