Integrated Analysis of hsa-miR-26b-5p and hsa-miR-186-5p in Blood Serum and Tumor Tissue Reveals their Prognostic and Predictive Significance in Breast Cancer.

BACKGROUND

Breast cancer (BC) heterogeneity signifi antly complicates diagnosis, prognosis, and prediction of treatment response. MicroRNAs (miRNAs) have emerged as promising biomarkers due to their involvement in tu- mor progression and in regulating therapy sensitivity. however, the combined clinical signifi ance of circulating and tumor-associated miRNAs, such as hsa-miR-26b-5p and hsa-miR-186-5p, remains insuffi    tly elucidated. Materi- als and Methods. Expression levels of hsa-miR-26b-5p and hsa-miR-186-5p were analyzed in serum and tumor tis- sue of 124 BC patients. Associations with clinicopathological parameters were assessed. The prognostic signifi ance was evaluated based on disease progression and recurrence within 3 years. The predictive value was determined in patients receiving neoadjuvant chemotherapy (4AC regimen) using response assessment and ROC analysis. Re- sults. young BC patients (≤45 years) demonstrated signifi antly lower circulating levels of both miRNAs. Serum hsa-miR-186-5p expression was associated with early-stage disease, tumor size, lymph node status, and molecular subtype. Increased circulating hsa-miR-26b-5p levels were linked to disease progression, whereas decreased hsa- miR-186-5p levels were observed in patients with unfavorable outcomes. In tumor tissue, hsa-miR-26b-5p expres- sion correlated with tumor grade, size, and metastatic status, showing elevated levels in poorly differentiated tumors and reduced expression in metastatic disease. In contrast, hsa-miR-186-5p was associated with the molecular sub- type and lymph node involvement, with the highest expression observed in hER2-positive tumors and in patients with recurrence. Elevated levels of hsa-miR-186-5p in both serum and tumor tissue were associated with reduced sensitivity to doxorubicin-based neoadjuvant chemotherapy. ROC analysis confi med its predictive value (AUC =  0.750 for serum and 0.818 for tumor tissue). No signifi ant association between hsa-miR-26b-5p and chemothe- rapy response was observed.

CONCLUSIONS

hsa-miR-26b-5p and hsa-miR-186-5p demonstrate complementary roles in BC biology. hsa-miR-26b-5p is primarily associated with tumor aggressiveness and cancer progression, whereas hsa-miR-186-5p refl cts its molecular characteristics and response to chemotherapy. Their combined assessment in serum and tumor tissue represents a promising approach for improving prognostic stratifi ation and predicting treatment effi acy in BC patients.