Mir-21-5p and Mir-455-5p as Markers for Diagnosis and Prognosis of Rectal Adenocarcinoma may Reduce Local CD4⁺ and CD8⁺ Lymphocyte Infiltration

Objective: This study aimed to verify miRNAs and the molecular mechanisms of diagnostic and prognostic biomarkers for rectal adenocarcinoma. Methods: Two miRNA datasets of rectal adenocarcinoma were obtained from GEO and TCGA. GEO2R tool, Venn diagram, Kaplan-Meier survival analysis, KEGG pathway analyses, DIANA TOOLS, and Wilcoxon rank-sum test were used for biological information analysis. The diagnostic utility of miRNAs and immune infiltration of tumors in Chinese patients were validated by RTqPCR and immunofluorescence analysis. Results: MiR-21-5P and miR-455-5p were both found to have a significant correlation with poor prognosis and higher expression in rectal adenocarcinoma. Besides, the ability to prognosis was independent of the clinicopathological stage. MiR-21-5P and miR-455-5p were enriched in the TGF-beta, Wnt, MAKP, and PI3K-AKT signaling pathways. Meanwhile, the high expression phenotype of miR-21-5P and miR-455-5p decreased CD4⁺ and CD8⁺ T cells. Conclusion: In summary, we found two significant diagnostic and prognostic miRNAs of rectal adenocarcinoma via integrated bioinformatics approach and clinical trials, which might decrease CD4⁺ and CD8⁺ T cells.