Evaluation of hsa-miR-155-5p as a diagnostic biomarker in breast cancer and identification of its potential target genes

Abstract Objectives Reliable molecular biomarkers are essential for improving early diagnosis and risk stratification in breast cancer. Among microRNAs, Homo sapiens microRNA-155-5p (hsa-miR-155-5p) has been widely implicated in tumorigenesis, but its diagnostic potential and functional targets remain incompletely defined. This study aimed to evaluate the diagnostic utility of miR-155-5p and identify its high-confidence target genes through integrative in silico analysis. Methods A case-control study was conducted on 52 paired breast tumors and adjacent non-tumor (ANT) tissues collected at Zheen International Hospital, Erbil, Kurdistan Region, Iraq. Expression levels of miR-155-5p were quantified by RT-qPCR using the ΔCq method, and associations with clinicopathological features were assessed. Diagnostic performance was evaluated using receiver operating characteristic (ROC) analysis. Integrative in silico analysis combined three computational tools (TargetScan, miRDB, and miRmap) with validated interactions from miRTarBase to identify potential target genes. Results Tumor tissues consistently exhibited lower ΔCq values compared with matched ANT tissues (52/52 pairs), corresponding to a robust median fold-change of 4.06 (interquartile range [IQR] 2.20–5.82), indicating significant upregulation. Expression was inversely correlated with patient age (Spearman’s ρ=−0.397, p=0.0036), with higher levels observed in younger patients. However, it showed no association with tumor grade (p=0.177) or histological subtype (p=0.950). ROC analysis demonstrated moderate diagnostic accuracy with an AUC of 0.746 (95 % CI 0.651–0.840; p<0.0001). In silico prediction identified 19 putative target genes, of which five (BRCA1, GNAS, KRAS, APC, and PIK3CA) were high-confidence targets. Conclusions miR-155-5p is significantly upregulated in breast tumor tissues, particularly among younger patients, and demonstrates moderate diagnostic potential. Integrative bioinformatics analysis provides novel insights by linking miR-155-5p with biologically relevant oncogenic pathways. These findings highlight both the clinical and biological importance of miR-155-5p and support further functional validation in larger independent cohorts.