Solute carrier family 25 member 32 promotes the proliferation of esophageal squamous cell carcinoma and is associated with immune infiltration

Abstract

Abstract Esophageal squamous cell carcinoma (ESCC) is a highly invasive and poorly prognosed malignant tumor of the digestive tract. Currently, there are no effective molecular classification markers for ESCC. This study screened out the key gene SLC25A32 based on mitochondrial-related genes and explored its expression characteristics, biological functions, and its relationship with the immune microenvironment. We integrated the transcriptome data of ESCC from the TCGA and GEO databases, used the limma package to screen for differentially expressed genes, and combined GO and KEGG enrichment analysis to explore the related signaling pathways. Subsequently, based on the mitochondrial-related genome, we identified 9 key genes, and through the screening of protein interaction networks, we identified 9 core hub genes, including BID , SLC25A32 , HIGD1A , ETFDH , ALDH3A2 , MPC1 , PINK1 , ACADM and ECHDC2 . Among them, BID and SLC25A32 are both upregulated in esophageal cancer, and BID is a known pro-apoptotic member of the BCL-2 family, with a relatively clear functional mechanism. However, the functional study of SLC25A32 , which is a mitochondrial folate transporter, in ESCC is still relatively limited and deserves further exploration. Further, we evaluated the correlation between SLC25A32 and immune infiltration characteristics, and used single-cell transcriptome data to analyze its expression distribution in different cell subpopulations in the tumor microenvironment. Finally, through immunohistochemistry, qRT-PCR, Western blot, proliferation and colony formation experiments, and an in vivo xenograft model, we systematically verified the regulatory role of SLC25A32 on the malignant phenotype of ESCC. A total of 1099 differentially expressed genes (DEGs), which are widely involved in important biological processes such as the cell cycle, DNA replication, and energy metabolism, were identified. Combined with mitochondria-related genes and protein–protein interaction (PPI) network analysis, SLC25A32 was selected as the hub gene for subsequent analysis and experimental verification. Immune infiltration analysis revealed that the expression level of SLC25A32 was positively correlated with M0-type macrophages and memory B cells but was negatively correlated with most immune cell types, such as plasma cells, monocytes, regulatory T cells (Tregs), CD8 + T cells, and naive B cells. Single-cell transcriptome sequencing revealed that SLC25A32 was expressed mainly in epithelial cells. Experimental validation demonstrated that SLC25A32 was significantly upregulated in ESCC tissues and cell lines, and functional assays—including proliferation, colony formation, and xenograft tumor models—confirmed that SLC25A32 knockdown suppressed ESCC cell proliferation in vitro and in vivo, accompanied by reduced Ki-67 expression. The results of this study indicate that SLC25A32 is an regulatory factor for the progression of ESCC, highlighting its potential as a therapeutic target for ESCC.