Background: Serine/arginine-rich splicing factor 1 (SRSF1) is a critical RNA splicing regulator implicated in various cancer types. However, its cell-type-specific expression patterns and functions within the tumor microenvironment remain poorly understood, particularly its interaction with immune cell populations. This study aimed to investigate SRSF1 expression patterns across different cell types in the endometrial carcinoma microenvironment using single-cell RNA sequencing and explore its potential association with macrophage efferocytosis.

Methods: We analyzed single-cell RNA sequencing data from five endometrial carcinoma samples (GSE173682, n = 33,178 cells) to characterize SRSF1 expression patterns. Efferocytosis activity was assessed using gene signature scoring with the AUCell algorithm. Cell-cell communication networks were analyzed using CellChat to identify interaction patterns. SRSF1 expression was validated in bulk tissue datasets from The Cancer Genome Atlas (TCGA) and Clinical Proteomic Tumor Analysis Consortium (CPTAC). Functional validation studies were performed in the Ishikawa endometrial cancer cell line using lentiviral-mediated SRSF1 knockdown.

Results: Single-cell analysis revealed significantly elevated SRSF1 expression in tumor-associated macrophages compared to other cell types (p < 0.05), with moderate expression also detected in tumor epithelial cells. Spatial analysis demonstrated a strong overlap between regions of high SRSF1 expression and areas exhibiting elevated efferocytosis activity. Functional enrichment analysis showed that efferocytosis-related genes participate in immune responses, extracellular activities, and antigen processing pathways. Pseudotime trajectory analysis identified seven functionally distinct macrophage subpopulations, including pro-inflammatory (M1-like) and immunosuppressive (M2-like) phenotypes, with varying SRSF1 expression levels. Cell-cell communication analysis revealed extensive interactions between macrophages and other cell types through specific ligand-receptor pairs, including SPP1-CD44. Bulk tissue analysis confirmed SRSF1 upregulation in endometrial carcinoma at both mRNA (TCGA, p < 0.05) and protein (CPTAC, p < 0.05) levels. In vitro functional validation in the Ishikawa cell line demonstrated that SRSF1 knockdown significantly inhibited cell proliferation (30–40% reduction at 96 hours), migration, invasion, and modulated epithelial-mesenchymal transition markers.

Conclusion: This study reveals cell-type-specific SRSF1 expression patterns in the endometrial carcinoma microenvironment and demonstrates strong associations between SRSF1 and macrophage efferocytosis activity. Correlation analysis showed significant associations between SRSF1 and key efferocytosis receptors (Mer tyrosine kinase (MERTK)), growth arrest-specific protein 6 (GAS6), providing molecular evidence for SRSF1's involvement in macrophage function.