Downregulation of miR-125a-5p Leads to STAT3 Increased Expression in Breast Cancer Patients.

Background: Breast cancer (BC) is one of the main causes of cancer-related death in women worldwide. It is necessary to find methods for prognosis and early detection of BC. MicroRNAs inhibit the expression of special target genes at the post-transcriptional stage and have a fundamental role in various cancers. They function as oncogenes or tumor suppressors. MiR-125a- 5p acts as a tumor suppressor in some cancers through a signal transducer and activator of transcription 3 (STAT3) suppression. STAT3 is activated in response to cytokines and growth factors, affecting the transcription of target genes.

Objective: We examined the association between miR-125a-5p and STAT3 expression levels in breast cancer patients for the first time through a case-control study on an Iranian population.

Methods: Total RNAs were extracted from breast cancer and healthy tissues using TRIzol Reagent. Complementary DNA synthesis was performed, and Real-time PCR was done using miR-125a and STAT3-specific primers. GAPDH and U48 genes were used as internal controls. Statistical analysis of the results was conducted by SPSS v.19.0 software.

Results: We obtained a significant association between miR-125a-5p down-regulation and breast cancer disease (0.4333 in patients vs. 1.656 in controls, p-value = 0.009). STAT3 expression was significantly up-regulated in BC samples relative to healthy subjects (1.324 vs. 0.6557, respectively) and p-value <0.0001.

Conclusion: We investigated that decreased miR-125a-5p expression levels were significantly associated with increased STAT3 expression in BC tissues. Therefore, the expression changes of miR- 125a-5p can be an important potential biomarker for early diagnosis of breast cancer. Also, the miRNA molecule may have serious therapeutic potential.