The Role of MiR-145-5p in Esophageal Squamous Cell Carcinoma Tumor-associated Macrophages and Selection of Immunochemotherapy

Background: The impact of miR-145-5p in immune infiltration and the potential application in esophageal squamous cell carcinoma (ESCC) immunochemotherapy remains unknown.

Methods: Transcriptomic data for ESCC tissues and normal tissues and clinical materials of patients with ESCC were obtained from The Cancer Genome Atlas (TCGA) and the Gene Expression Omnibus (GEO) databases. The differences in mRNA levels in cancer tissues and noncancerous tissues were analyzed, and we subsequently investigated the association between miR-145-5p expression and the key parameters of ESCC progression and prognosis. Additionally, cytological experiments were performed to evaluate the biological functions of miR-145-5p. Pathways potentially affected by miR-145-5p were analyzed by Gene Set Enrichment Analysis (GSEA) and REACTOME. We also analyzed the function of miR-145-5p in immune infiltration through the TIMER2 (Tumor Immune Estimation Resource) database.

Results: The analysis of gene chip data from the TCGA database and GEO database (including GSE13937 and GSE43732) showed that the expression of miR-145-5p is downregulated in ESCC (P<0.05) and that patients with high miR-145-5p levels had lower survival rates (P<0.05). The expression of miR-145-5p was significantly correlated with the disease-free survival (DFS) rate (P<0.05) and M stage (P<0.05) in the TCGA database and was significantly correlated with the T stage (P<0.05) and TNM stage (P<0.05) in the GSE13937 database. Functional experiments showed that miR-145-5p attenuated proliferation (P<0.05), migration (P<0.01) and invasion (P<0.01) in the Eca109 cell line. Both GSEA gene enrichment and REACTOME gene enrichment revealed that miR-145-5p was associated with tumor signaling pathways and immune signaling pathways. Immune infiltration analysis revealed that the expression level of miR-145-5p was significantly correlated with the infiltration level of macrophages (P<0.05) and was positively correlated with the level of gene markers of M2 macrophages and tumor-associated macrophages (P<0.05).

Conclusions: MiR-145-5p acts as a tumor suppressor microRNA in ESCC and is an important noncoding RNA in the high M2-like tumor-associated macrophage infiltration of ESCC. Assessing the miR-145-5p level in ESCC samples has translational meaning, which help illustrate the immune infiltration status, predict the prognostic outcome, and select the type of immunochemotherapy.