Regulatory T Cell Infiltration-Driven Single-Cell Transcriptomic Analysis Identifies SAP18 as a Prognostic Marker for Esophageal Squamous Cell Carcinoma.

Abstract

Background: Advanced esophageal squamous cell carcinoma (ESCC) is characterized by molecular heterogeneity and distinct patterns of immune cell infiltration. Regulatory T cells (Tregs), in particular, play a critical role in shaping an immunosuppressive tumor microenvironment (TME), which is associated with poor clinical outcomes.

Methods: We developed a prognostic model by integrating GEO-derived bulk RNA sequencing data and single-cell transcriptome. Model predictions were confirmed through RT-qPCR, Western blot, and immunohistochemistry on clinical specimens, while in vitro assays (CCK8, transwell invasion, scratch, colony formation, and immunofluorescence) validated the function of SAP18 in cell proliferation, invasion, and ECM remodeling.

Results: Expression patterns of the 5 Tregs-associated genes in clinical specimens aligned with model predictions, underscoring the model's robustness. The high-risk subgroup was associated with upregulated extracellular matrix (ECM) remodeling, an abundance of immune-suppressive cells, higher TP53 mutation rate, and limited benefit from immunotherapy. In contrast, the low-risk subgroup exhibited anti-tumor immunity. Cell-cell communication analysis also implicated the collagen pathway in Tregs-mediated immune evasion in ESCC. Functional assays indicated that SAP18 in the prognostic model significantly promotes proliferation, invasion, and ECM reconstruction, further highlighting its potential as a therapeutic target.

Conclusion: Our findings elucidate the role of Tregs in the TME, underscoring significant potential of SAP18, which is essential for assessing patient prognosis and may facilitate the development of personalized therapies for ESCC.