Circulating MicroRNA in Breast Cancer

Area of Science:

• Molecular Biology and Genetics
• Oncology
• Biomarker Discovery

Background:

• Triple-negative breast cancer (TNBC) remains a clinical challenge despite advances in diagnostics and personalized medicine.
• Extracellular microRNAs (miRNAs) are gene regulators found in biofluids, protected by vesicles or proteins.
• This review focuses on extracellular miRNAs in breast cancer, their subtype-specific roles, and potential as liquid-biopsy biomarkers.

Purpose of the Study:

• To review current evidence on oncogenic and tumor-suppressive extracellular miRNAs in breast cancer.
• To emphasize subtype-specific functions and clinical relevance of miRNAs as biomarkers and therapeutic targets.
• To synthesize findings on circulating miRNAs for diagnosis, prognosis, and treatment response prediction.

Main Methods:

• PubMed literature review (January 2000-February 2026) using combined search terms for breast cancer and circulating miRNAs.
• Prioritization of studies with validated targets, mechanisms, or clinical evidence for diagnostic/prognostic utility.
• Subtype-aware evaluation of findings, organized by functional categories and clinical/translational studies.

Main Results:

• miR-21 and miR-155 identified as prominent oncogenic miRNAs; miR-205 as a tumor-suppressive miRNA.
• Circulating miRNA panels show potential for sensitive and specific breast cancer diagnostics.
• Subtype-dependent miRNA effects observed, with opposing roles in TNBC versus ER-positive breast cancer.

Conclusions:

• Circulating miRNAs are promising minimally invasive biomarkers and potential therapeutic targets for breast cancer.
• Clinical translation is limited by biological context dependence and pre-analytical/analytical variability.
• Standardized, subtype-aware protocols and validated panels are crucial for clinical implementation and precision oncology.