Single cell transcriptomics analyses reveal functional heterogeneity and anti-tumor role of mast cells in esophageal squamous cell carcinoma
Introduction Mast cells (MCs) play important roles in allergic reactions and tissue homeostasis; however, their functions in esophageal squamous cell carcinoma (ESCC) remain controversial. Understanding the heterogeneity and functional states of MCs in ESCC is essential for elucidating their roles in tumor progression and immune regulation. Methods single-cell RNA sequencing (scRNA-seq) data from 84 ESCC samples across four independent cohorts were analyzed to identify MC subtypes, which were further validated using bulk RNA-seq and immunofluorescence staining. Functional assays were performed to assess the effects of stem cell factor (SCF)-stimulated MCs on ESCC cell proliferation, migration, and apoptosis. Spatial transcriptomics were used to investigate MC interactions within the tumor microenvironment (TME). Results MC abundance was significantly reduced in ESCC tissues compared with normal esophageal tissues, as confirmed by bulk RNA-seq and IHC analyses. scRNA-seq revealed five distinct MC subtypes in ESCC: T-type-activated MC, T-type-resting MC, TC-type-activated MC, TC-type-resting MC and proliferating MC. Resting MCs localized to normal and stromal regions, whereas activated MCs were enriched in stromal and tumor regions, with their proportion significantly elevated in tumor tissues. SCF activated MCs via the c-Kit pathway, promoting TNF-α release and tumor cell apoptosis. Spatial and cell-cell communication analyses revealed extensive MC interactions with stromal and immune cells. Activated MC abundance positively correlated with T-cell infiltration and favorable ESCC prognosis. Conclusions Our findings demonstrate that MCs exhibit distinct functional states in ESCC and regulate tumor progression. T-type-activated MCs, characterized by enhanced TNF-α expression, may contribute to anti-tumor immunity. These findings provide new insights into MC heterogeneity in ESCC and support their potential relevance in immunotherapy.